As previously stated, many commenters argued that the proposed
numeric particulates standard was incompatible with the air quality
requirements established under the States' Implementation Plans (SIPs)
or with provisions set up by the states in their Title V Clean Air
Permits to the power producers. In addition, the commenters argued that
the proposed standard lacked technical details to facilitate effective
implementation, and that implementation of the standard required
specialized equipment and advanced training to carry out a judicious
reading and interpretation of opacity, a proxy measure for the level of
fugitive dust emissions. In light of these comments, EPA re-evaluated
the existing CAA standards applicable to these units; 40 CFR 70.2
identifies fossil-fuel-fired steam electric plants of more than 250
million BTU/hour heat input as potential sources of fugitive dust (PM
sources) that must be covered by state permitting, and 40 CFR 70.3
stipulates that fugitive emissions from a part 70 source shall be
included in the permit application and the part 70 permit in the same
manner as stack emissions, regardless of whether the source category is
included in the list of sources contained in the definition of major
source. Based on these applicable CAA requirements, the Agency agrees
that the adoption of a PM standard under the final rule would entail a
potential for duplication or inconsistency with applicable state-
established standards in SIP permits.
    EPA also acknowledges the challenges involved in measuring the
proposed compliance standard. Because fugitive dust is emitted from
non-point sources, it cannot be easily measured by conventional
methods. Usually, regulations developed by the states to control
fugitive dust stipulate that no person or source shall cause or allow,
from any activity, any emissions of fugitive particulate matter that
are visible to an observer who looks horizontally along the source's
property line. A quantitative measurement of fugitive dust levels
(EPA's Reference Method 9) would require measuring opacity, which, as
the commenters noted, necessitates specialized technical training,
trainee certification, and judicious application of instrumentation.
    Therefore, rather than requiring a potentially redundant and
challenging-to-implement quantitative standard, EPA is substituting a
performance standard for fugitive dust control. This standard requires
owners or operators of a CCR unit to adopt measures that will
effectively minimize CCR from becoming airborne at the facility,
including CCR fugitive dust originating from CCR units, CCR piles,
roads, and other CCR management activities. The Agency considers this
standard to be consistent with the intent of the proposed rule, with
the added advantage of allowing facilities the flexibility to determine
the appropriate measures to achieve regulatory compliance at their
individual site. This standard and the accompanying regulatory
requirements supporting its implementation, will achieve the statutory
obligation of ``no reasonable probability of adverse effects on human
health and the environment.''
    As in the proposal, the Agency is also requiring documentation of
the measures taken to comply with the technical standard in a ``CCR
fugitive dust control plan'' (herein referred to as ``plan'').
Consistent with the proposal, the plan must be certified by a qualified
professional engineer and placed in the operating record and on the
owner or operators publicly accessible internet site. The plan requires
owners or operators to elaborate on the types of activities applicable
and appropriate for the conditions at the facility that will be
employed to minimize CCR from becoming airborne at the facility.
Examples of control measures that may be appropriate include: Locating
CCR inside an enclosure or partial enclosure; operating a water spray
or fogging system; reducing fall distances at material drop points;
using wind barriers, compaction, or vegetative covers; establishing and
enforcing reduced vehicle speed limits; paving and sweeping roads;
covering trucks transporting CCR; reducing or halting operations during
high wind events; or applying a daily cover.
    The initial plan must be completed by the effective date of the
rule (i.e., within six months of publication). Because this is an
initial plan, and because it must be completed within a short
timeframe, EPA acknowledges that the facility may only be able to
present its initial judgment of the measures that it anticipates are
likely to be effective based on the information that is readily
available within this six month

timeframe. EPA anticipates that owners or operators may need to revise
the plan as they gain additional information and experience
implementing the regulations. In recognition of this, the final rule
also requires that the CCR fugitive dust control plan include a
description of the procedures the owner or operator will follow to
periodically assess the effectiveness of the control plan. Consistent
with other plans required in this rule, the owner or operator may amend
the written CCR fugitive dust control plan at any time. However, the
owner or operator must amend the written plan whenever there is a
change in conditions that would substantially affect the written plan
in effect, such as the construction and operation of a new CCR unit.
The plan and any subsequent amendments must be certified by a qualified
professional engineer.
    In addition, the Agency is promulgating with a slight modification
the requirement for owners and operators of all CCR landfills and any
lateral expansion to emplace CCR as conditioned CCR, as well as the
definition of conditioned CCR. Conditioned CCR has been defined to mean
CCR wetted with water to a moisture content that will prevent wind
dispersal, but will not result in free liquids, consistent with the
definition in the proposed rule. In response to several commenters'
requests, and upon further evaluation the Agency is allowing that in
lieu of water, CCR conditioning may be accomplished with an appropriate
chemical dust suppression agent.\106\ As with other requirements of
this rule, in order to ensure that the provisions of the fugitive dust
criteria are maintained throughout the operating life of the CCR unit,
the Agency is requiring that the owner or operator prepare an annual
CCR fugitive dust control report, describing the actions taken to
control CCR fugitive dust, a record of all citizen complaints, and a
summary of any corrective measures taken. The first annual report must
be completed no later than 14 months after placing the initial CCR
fugitive dust control plan in the facility's operating record. The
owner or operator has completed the annual CCR fugitive dust control
report when the plan has been placed in the facility's operating
record.
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    \106\ Spray-on adhesives, surfactants, aqueous foamers,
humectants (calcium, magnesium, ad sodium chloride and their
mixtures), and polymer solutions and emulsions. See, for instance
``The Role of Chemicals in Controlling Coal Dust Emissions''
Benetech, Inc. available at http://pdf.ebooks6.com/download.php?id=139860 or Peterson, Edwin. ``An Aid to Fugitive
Materials Control in Coal Ash Applications'' presented at the World
of Coal Ash (WOCA) conference--May 9-12, 2011 in Denver, Colorado.
---------------------------------------------------------------------------

    The general public, as well as the Agency, is highly concerned with
potential risks associated with CCR fugitive dusts. This was readily
apparent during the public hearings and from the many comments received
on this issue. The Agency continues to receive information regarding
this human health and environmental concern. While the subtitle D
provisions of this rule lack permitting oversight mechanisms to control
fugitive dust from CCR units, it is clear to the Agency that additional
substantive actions was needed to facilitate citizen suit enforcement
of this criteria. Consequently, the Agency are adding a specific
requirement to the CCR fugitive dust control plan to require owners and
operators of all CCR units to develop and implement formal procedures
to log citizen complaints involving CCR fugitive dust events. These
complaints must, then, be included as part of the annual CCR fugitive
dust control report. This report must be placed in the operating record
and on the owner or operator's publicly accessible internet site.
Promulgation of these measures will subject the owner or operator of
the CCR disposal facility to public and state scrutiny, and create an
incentive for the owner or operator of the CCR disposal facility to
improve compliance with the fugitive dust control requirements.

G. Operating Criteria--Run-On and Run-Off Controls for CCR Landfills

    EPA's proposal required owners or operators of CCR landfills and
all lateral expansions to design, construct and maintain a run-on
control system to prevent flow onto the active portion of these units
during the peak discharge from a 24-hour, 25-year storm. As described
in the proposed rule, run-on controls are designed to prevent erosion,
which may damage the physical structure of the landfill, prevent the
surface discharge of CCR in solution or suspension; and to minimize the
downward percolation of run-on through wastes, creating leachate.
Similarly, EPA proposed run-off controls in order to collect and
control, at a minimum, the water volume resulting from a 24-hour, 25-
year storm. This standard was proposed in order to protect surface
waters from contamination. Under the existing 40 CFR part 257
requirements, to which CCR units are currently subject, run-off must
not cause a discharge of pollutants into waters of the United States
that is in violation of the National Pollutant Discharge Elimination
System (NPDES) under section 402 of the Clean Water Act. EPA did not
propose to revise the existing requirement, but merely incorporated it
for ease of the regulated community.
    The Agency proposed the 24-hour period because it was a timeframe
that included storms of high intensity with short duration and storms
of low intensity with long duration. EPA believed that this was a
widely used standard that had been incorporated into the hazardous
waste landfills and MSW landfills regulatory requirements. At the time,
EPA had no information that warranted a more restrictive standard for
CCR landfills. EPA received no significant comment on the proposed
requirements, and for the most part, is adopting the proposed
requirements without revision. However, in an effort to clarify and
provide more direction to the owner or operator and the certifying
qualified professional engineer, the Agency has added additional
regulatory language that more specifically describes the technical
criteria established under this section of the rule.
    The run-on and run-off controls of the final rule require that the
owner or operator prepare the initial run-on and run-off control system
plan within 18 months of publication of the rule. Run-on and run-off
control system plan reporting may require design, construction, and
post-construction implementation. In instances where run-on and run-off
capacity is insufficient, installing additional capacity may involve
construction of diversion structures such as swales or ditches. Many of
these efforts may require several months of design and construction,
compounded by the fact that much of the work cannot be completed in
cold-weather or heavy-rain seasons.
1. Run-On and Run-Off Controls for CCR Landfills and All Lateral
Expansions \107\
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    \107\ In the proposed rule under the RCRA subtitle D option, EPA
jointly proposed run-on and run-off requirements for CCR landfills
and CCR surface impoundments under proposed Sec.  257.81. In this
final rule, EPA has modified the ``run-on and run-off'' requirements
and is providing separate requirements for CCR landfills and CCR
surface impoundments. CCR surface impoundments are now subject to
the hydrologic and hydraulic capacity requirements at Sec.  257.82.
This new section of the rule more appropriately addresses flow
management issues at CCR surface impoundments.
---------------------------------------------------------------------------

    All CCR landfills and all lateral expansions must be designed,
constructed, operated, and maintained with a run-on control system to
prevent flow onto the active portion of the CCR unit from the peak
discharge from a 24-hour, 25-year storm and a run-off control system to
collect and control at

least the volume of water resulting from a 24-hour, 25-year storm from
the active portion of the CCR unit.\108\
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    \108\ Under existing part 257 requirements, to which CCR units
are currently subject, runoff must not cause a discharge of
pollutants into waters of the United States that is in violation of
the National Pollutant Discharge Elimination System (NPDES) under
section 402 of the Clean Water Act (40 CFR 257.3-3). EPA did not
propose to revise this requirement but is merely incorporating it
here for ease of the regulated community.
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    Consistent with the proposal, the rule requires the owner or
operator of a CCR landfill or lateral expansion to prepare an initial
run-on and run-off control system plan for the CCR unit. For existing
CCR landfills, the plan must be prepared by the owner or operator no
later than one year from the effective date of the rule. For new CCR
landfills and any lateral expansion of a CCR landfill, the plan must be
prepared no later than the date of initial placement of CCR in the
landfill or lateral expansion. The plan must document how the run-on
and run-off control systems have been designed and constructed to meet
the requirements of rule and must be supported by appropriate
engineering calculations. The run-on and run-off control system plan
must be certified by a qualified professional engineer and is
considered prepared when the owner or operator has placed the plan in
the facility's operating record.
    The rule also provides for the owner or operator to amend the plan
at any time (e.g., prior to receipt of CCR in the CCR unit, during the
operating life of the CCR unit, during closure of the CCR unit, or
following closure of the CCR unit) provided the revised plan is placed
in the facility's operating record. The owner or operator must, however
revise the plan whenever there is a change in the conditions that would
substantially affect the written plan in effect (e.g., closure of an
existing portion or cell of the CCR landfill, resulting in a possible
change in the size of the ``active portion'' of the CCR landfill).
    In addition, consistent with other provisions in this rule, the
Agency is requiring that the run-on and run-off control system plan be
reviewed, and where necessary, revised or updated at least every five
years. The Agency is specifying this periodic review in order to
address factors having the potential to influence the run-on and run-
off control system. Among other things, CCR landfills can be subject to
build-out, operational changes, and surface cover changes, all of which
have the potential to significantly alter run-on and run-off flows to
and from the active portion of the CCR landfill. Changes in storm
intensity and duration, as well as upstream catchment area
characteristics, can alter flows that may significantly affect a
previously adequate run-on and run-off control system. A mandated five
year review of a control system plan is consistent with accepted good
engineering practices and protocols for proper maintenance of
operational systems supporting the overall performance of a CCR
landfill. It is also consistent with the proposed requirement that an
owner or operator ``maintain'' the run-on and run-off control system.
EPA interprets this to require the owner or operator to ensure that the
run-on and run-off control system is kept in a condition that meets the
requirements of the rule, i.e., that the run-on and run-off control
system both prevents flow onto the active portion of the unit during
the peak discharge from a 24-hour, 25-year storm and collects and
controls at least the water volume resulting from a 24-hour, 25-year
storm event for the duration of the CCR landfill's operational life. A
requirement to conduct a review of the control plan at least once every
five years merely provides an explicit mechanism to ensure this occurs
in a manner that facilitates citizen and state oversight.
    The date of preparing the initial plan is the basis for
establishing the deadline to complete the first subsequent plan; i.e.,
the subsequent plan must be completed within five years of the prior
plan. The owner or operator may complete any required plan prior to the
required deadline and must place the completed plan into the facility's
operating record within the five year timeframe. A qualified
professional engineer must certify that the run-on and run-off control
system plan, including any subsequent amendments, meets the run-on and
run-off control system requirements of this final rule.
a. Run-On Control
    Consistent with the proposal, EPA is defining run-on to mean any
liquid that drains over land onto any part of a CCR landfill or any
lateral expansion of a CCR landfill. In surface water hydrology, run-on
is a quantity of surface run-off, or excess rain, snowmelt, or other
sources of water, which flows from an upstream catchment area onto a
specific downstream location. This rule requires that the CCR landfill
be designed, constructed, operated, and maintained to prevent flow onto
the active portion of the CCR landfill during the peak discharge from a
24-hour, 25-year storm. EPA has adopted this requirement to minimize
the amount of surface water entering the CCR landfill and to minimize
disruption of the CCR landfills operation due to storm water inflow.
Uncontrolled or undesirable storm water run-on may have significant
impacts on the stability of the slopes of a CCR landfill and continued
safe operation of the CCR landfill, due to such phenomena as erosion
and infiltration.
b. Run-Off Control
    EPA has adopted the definition of run-off from the proposal without
revision. Run-off means any liquid that drains over land from any part
of the CCR landfill. Effectively, run-off is the portion of rainwater,
snowmelt, or other liquid which does not undergo abstraction, such as
infiltration, and travels overland. Typically, run-off is the product
of the inability of water to infiltrate into soil due to saturation or
infiltration rate capacity being exceeded. The rule requires that the
CCR landfill be designed, constructed, operated, and maintained to
collect and control at least the water volume resulting from a 24-hour,
25-year storm. The owner or operator must design, construct, operate,
and maintain the CCR landfill in such a way that any run-off generated
from at least a 24-hour, 25-year storm must be collected through
hydraulic structures, such as drainage ditches, toe drains, swales, or
other means, and controlled so as to not adversely affect the condition
of the CCR landfill. EPA has promulgated these requirements to minimize
the detention time of run-off on the CCR landfill and minimize
infiltration into the CCR landfill, to dissipate storm water run-off
velocity, and to minimize erosion of CCR landfill slopes. An additional
concern with run-off from CCR landfills is the water quality of the
run-off, which may collect suspended solids from the landfill slopes.
EPA acknowledges that the run-off requirements will also minimize the
amount of run-off related pollution generated by the landfill run-off.
c. Run-On and Run-Off Control System Plan
    The owner or operator of any CCR landfill must prepare an initial
run-on and run-off control system plan documenting, with supporting
engineering calculations, how the control systems have been designed
and constructed to meet the requirements of the rule. This has been
adopted without revision from the proposal. In most cases, EPA expects
this documentation will include in addition to the supporting
engineering calculations, references and drawings regarding the

identification of the 24-hour, 25-year storm for the location of the
CCR landfill, a characterization of the rainfall abstractions,
including but not limited to depression storage and infiltration, the
selection and basis of an appropriate run-off model, the selection and
basis of an appropriate run-on or run-off routing model, and the
selection and design of an appropriate run-on and run-off management
system (e.g., swales, ditches, retention or detention ponds).
Consideration of the above factors would generally constitute a
comprehensive review of the hydraulic and hydrologic processes
associated with the design of a run-on and run-off control system plan.
EPA recognizes that over time, any number of factors, e.g., expansion
of the facility, could affect a change in the run-on and run-off
control system plan. Consequently in the final rule EPA is providing
for flexibility in this area by stating that the plan can be amended by
the owner or operator at any time during the life of the CCR landfill,
provided the amendments are placed in the operating record and on the
facility's publicly accessible Internet site.

H. Operating Criteria--Hydrologic and Hydraulic Capacity Requirements
for CCR Surface Impoundments

    As discussed in the previous section, EPA proposed to require
owners or operators of CCR landfills to design, construct, operate, and
maintain: (1) A run-on control system to prevent flow onto the active
portion of the unit during the peak discharge from a 24-hour, 25-year
storm; and (2) a run-off control system to collect and control, at a
minimum, the water volume resulting from the same 24-hour, 25-year
storm. EPA also proposed to apply these same run-on and run-off
requirements to all CCR surface impoundments and lateral expansions.
    Commenters overwhelmingly disagreed with EPA's decision to apply
the same run-on and run-off requirements to both CCR landfills and CCR
surface impoundments, arguing that a ``control system to prevent flow
onto the active portion of the surface impoundment'' was at odds with a
commonly employed practice of using CCR surface impoundments to manage
incoming storm water and other inflow. While some commenters reasoned
that preventing run-on may be appropriate for CCR landfills and CCR
surface impoundments surrounded by above-ground dikes, the proposed
requirement was entirely inappropriate for units specifically designed
to retain storm water from an adjoining watershed or to operate as part
of a facility's overall storm water management system. Numerous
commenters suggested that instead of the run-on prevention provision
for CCR surface impoundments, EPA adopt a requirement specifying that
CCR surface impoundments be designed to accommodate ``peak discharge
events.'' Other commenters argued that storm water run-on controls were
only appropriate during and after the closure of CCR surface
impoundments; while still other commenters suggested that EPA remove
entirely the run-on and run-off requirements because CCR surface
impoundments were typically designed to impound and discharge storm
water flow far in excess of a 25-year/24-hour storm event.
    In evaluating the arguments against the requirements to prevent
flow onto the CCR surface impoundment, the Agency was strongly
influenced by guidance developed by FEMA for selecting and
accommodating hydraulic and hydrologic inflow and outflow as well as
the application of this guidance to the CCR surface impoundments
evaluated as part of EPA's Assessment Program.\109\ A review of FEMA
guidance confirmed commenters' contentions that managing flow both to
and from dams and impoundments was a widely used practice, and a
preferable management strategy for accommodating storm water flows.
This was further confirmed by observations made during EPA's Assessment
Program; EPA frequently observed units designed to detain or retain
storm water inflows of an upstream catchment area to manage CCR, and/or
to receive storm water inflow as part of the facility's overall storm
water management system. Moreover, EPA relied on the same FEMA guidance
to assess the adequacy of the hydrologic and hydraulic capacity of the
CCR surface impoundments. In conducting these assessments, EPA
considered a number of factors including operating freeboard, catchment
area, hydrologic structures' inflow and outflow ratings, design
precipitation event, spillway presence and capacity, and unit operating
procedures to make this determination. The adequacy of the capacity was
determined using FEMA guidance for selecting and accommodating inflow
design floods (IDF) for dams. (Note: The use of the terminology related
to ``inflow design flood'' for CCR surface impoundments rather than
``run-on'' and ``run-off'' is more directly applicable to the hydraulic
and hydrologic capacity of CCR surface impoundments to adequately
manage both the inflow and outflow from a design flood.)
---------------------------------------------------------------------------

    \109\ EPA referred to FEMA's ``Federal Guidelines for Dam
Safety: Selecting and Accommodating Inflow Design Floods for Dams''
in evaluating the adequacy of the CCR surface impoundment's
hydrologic and hydraulic capacity during its assessment effort.
---------------------------------------------------------------------------

    During its assessment effort, EPA also found that, contrary to
commenter's arguments CCR surface impoundments were often not designed
to address floods in excess of a 24-hour, 25-year storm event. Rather
many CCR surface impoundments were deficient in their hydrologic and
hydraulic capacity requirements due to factors such as lack of
operating freeboard, misunderstanding of the actual contributory area,
lack of documentation, undersized decant structures, undersized
spillways, and lack of spillways.
    EPA also disagrees with the comment asserting that storm water
controls are only appropriate during and after closure of CCR surface
impoundments. Hydrologic and hydraulic capacity, as determined by an
effective design flood control system, is an essential element of the
overall structural integrity and safety of a CCR surface impoundment.
CCR surface impoundments are subject to any number of stresses
throughout their operational life; one of the most common causes of a
dike or embankment failure being the inability of the CCR unit to
adequately pass or manage flood flows resultant from direct or indirect
precipitation. These failures can occur at any point in the CCR unit's
life, not solely during and after closure, and are usually due to
inadequate hydrologic and hydraulic capacity, leading to internal
erosion due to seepage and piping, erosion of spillways, overtopping
erosion, and overstressing of the embankment. Furthermore, according to
the U.S. Bureau of Reclamation, a common dam failure mode is due to
overtopping, accounting for 30% of the failures in the U.S. over the
last 75 years.\110\ Overtopping is the direct result of lack of
adequate hydrologic and hydraulic capacity of a dam or surface
impoundment. Therefore, EPA is not modifying the regulation as
suggested by the commenter.
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    \110\ http://www.usbr.gov/ssle/damsafety/Risk/BestPractices/16-FloodOvertoppingPP20121126.pdf.
---------------------------------------------------------------------------

    In light of comments received, observations made during EPA's
Assessment Program, and guidance developed by FEMA, EPA has concluded
that it was inappropriate to propose to prohibit all run-on discharge
or inflow from storm water to CCR surface impoundments. EPA has also

concluded that run-on and run-off criteria are inappropriate for CCR
surface impoundments, and that a more appropriate standard involves
determining the hydrologic and hydraulic capacity of a unit, measured
by its inflow design flood or IDF. Therefore, EPA is amending the
proposed run-on and run-off requirements for CCR surface impoundments
to require owners or operators of all CCR surface impoundments to
design, construct, operate, and maintain hydraulic and hydrologic
capacity to adequately manage flow both into and from a CCR surface
impoundment during and after the peak discharge resulting from the
inflow design flood, based on the Hazard Potential Classification of
the CCR surface impoundment.
    The final rule requires the preparation of the initial inflow
design flood control system plan within 18 months of publication of the
final rule. In many cases, inflow design flood control system plan
reporting may require design, construction, and post-construction
implementation in order to provide sufficient hydrologic and hydraulic
(H/H) capacity for the CCR unit. In instances where H/H capacity is
insufficient, installing additional capacity may involve spillway
construction or decant structure construction or installation. Many of
these efforts may require several months of design and construction,
compounded by the fact that much of the work cannot be completed in
cold-weather or heavy-rain seasons.
1. Inflow Design Flood Controls for CCR Surface Impoundments and All
Expansions
    The Agency has concluded that the proposed requirement preventing
run-on to a CCR surface impoundment was both impractical and
unwarranted and could possibly disrupt effective storm water management
systems operating at CCR facilities. Therefore, consistent with FEMA
guidance, the Agency is modifying this requirement to require an owner
or operator of an existing or new CCR surface impoundment or any
lateral expansion to design, construct, operate, and maintain H/H
capacity of CCR surface impoundments to: (1) Adequately manage flow
into the CCR surface impoundment during and following the peak
discharge of the inflow design flood; and (2) adequately manage flow
from the CCR unit to collect and control the peak discharge resulting
from the inflow design flood. The inflow design flood is based on the
hazard potential classification of the unit as required by Sec.  257.73
and Sec.  257.74 of this rule.\111\ The inflow design floods for
specific hazard potential classifications are as follows: (1) The
probable maximum flood (PMF) for high hazard potential CCR surface
impoundments; (2) the 1000-year flood for significant hazard potential
CCR surface impoundments; (3) the 100-year flood for low hazard
potential CCR surface impoundments; and (4) the 25-year flood for
incised CCR surface impoundments.\112\
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    \111\ Federal Guidelines for Dam Safety: Selecting and
Accommodating Inflow Design Floods for Dams. August 1, 2013. FEMA P-
94.
    \112\ All discharge from the CCR surface impoundment must be
handled in accordance with the surface water requirements under
Sec.  257.3-3.
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    EPA has based this revised requirement on the FEMA's guidance
entitled, ``Selecting and Accommodating Inflow Design Floods for
Dams,'' which represents current and accepted practices in dam
engineering and provides a consistent and uniform standard that has
been adopted throughout dam engineering.
    Incised CCR surface impoundments, as defined in this rule, are also
required to meet inflow design flood requirements.\113\ While incised
units do not pose the same potential for release as a diked unit, i.e.,
breach of dike and release of CCR, overtopping of an incised unit does
represent a potential environmental hazard warranting control. EPA
acknowledges, however, that overtopping of an incised unit would result
in a release of CCR material through a surcharge flow, i.e., flow of a
temporary stage overtopping the ``crest'' of the incised CCR surface
impoundment, and would not precipitate the degradation of a dike and
potential subsequent breach of a dike and massive release of contents
of the CCR surface impoundment. To reflect the lower risks associated
with such releases, and because incised CCR surface impoundments are
not required to determine their hazard potential classification, the
Agency is requiring that incised CCR surface impoundments only must
accommodate a 25-year flood for the hydrologic and hydraulic capacity
requirements of the rule. EPA chose the 25-year flood for incised CCR
surface impoundments to maintain consistency with the proposed rule,
which required that all units accommodate a 25-year storm event. As
part of these requirements, EPA is also finalizing a definition of
inflow design flood and flood hydrograph. Inflow design flood has been
defined to mean the flood hydrograph that is used to design or modify
the CCR surface impoundment and its appurtenant works, and flood
hydrograph has been defined to mean the temporal distribution of inflow
into a CCR surface impoundment.
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    \113\ Incised CCR surface impoundment means a CCR surface
impoundment which is constructed by excavating entirely below the
natural ground surface, holds an accumulation of CCR entirely below
the adjacent natural ground surface, and does not consist of any
constructed diked portion.
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2. Inflow Design Flood Control Systems
    Controlling the inflow and outflow of the CCR surface impoundment
reduces the risks of hydrologic failure, which include overtopping
erosion, internal excessive seepage and piping, erosion of spillways,
and overstressing of the structural components of the CCR surface
impoundment. The CCR surface impoundment's H/H capacity is to be
designed based on the unit's hazard potential classification as
determined by a qualified professional engineer. To meet the
performance standard in the rule, the CCR surface impoundment must be
designed to have adequate H/H capacity to ensure that rainfall and
watershed characteristics have been accounted for, the hydraulic
ratings of all intake structures are adequate and free of obstruction,
operating freeboard is adequate, all spillways and decant structures
have adequate capacity, and all downstream hydraulic structures have
adequate capacity. While not required, an antecedent flood study may be
necessary to characterize the condition of the CCR surface impoundment
under normal operating conditions.
    EPA recognizes that in many impoundment configurations, an inflow
design flood may be limited to the direct precipitation that falls
within the perimeter of the CCR surface impoundment during a storm
event, due to the lack of storm water inflow routing from adjacent
catchment areas. Other CCR surface impoundments may have storm water or
other hydrologic contributions from various catchment areas or other
sources. The final rule's hydraulic and hydrologic capacity standards
require all CCR surface impoundments to have adequate hydraulic and
hydrologic capacity to accommodate all contributory inflow to CCR
surface impoundments, regardless of the inflow's origin.
    The hydraulic and hydrologic capacity requirements will minimize
the potential for overtopping to occur from normal or abnormal
operations, overfilling, wind and wave action, rainfall, and run-on,
and will ensure that the unit is operated with appropriate
consideration of these potentially adverse conditions. The Agency
notes, however, that the operating freeboard of a CCR surface

impoundment is subject to fluctuations, deviating from original design
assumptions and specifications. Additionally, EPA notes that routine
maintenance and alterations of hydraulic structures associated with the
CCR surface impoundments, e.g., decant structures and spillways, can
adversely impact the hydrologic and hydraulic capacity of the CCR
surface impoundment. At no point should the inflow design flood exceed
the capacity of the CCR surface impoundment, regardless of fluctuations
in freeboard, maintenance of hydraulic structures, or other potential
obstructions to the hydraulic and hydrologic capacity of the unit. The
owner or operator must account for operational changes or diminished
capacity in the calculation of hydraulic and hydrologic capacity of the
CCR unit.
3. Inflow Design Flood Control System Plan
    The owner or operator of an existing CCR surface impoundment must
prepare an initial inflow design flood control system plan to document
that the design and construction of the system will achieve the rule's
performance standards no later than 18 months after the publication of
this rule in the Federal Register. New CCR surface impoundments or
lateral expansions of CCR surface impoundments must prepare an initial
inflow design flood control system plan no later than the date of
initial receipt of CCR in the unit. The owner or operator must obtain a
certification from a qualified professional engineer that the plan
meets all applicable requirements of the rule for inflow design flood
control system plans. The plan must also be supported by appropriate
engineering calculations. This documentation should also include
references, and drawings regarding the identification of the design
storm for the catchment area affecting the CCR surface impoundment and
the CCR surface impoundment itself, a characterization of the rainfall
abstractions, including but not limited to depression storage and
infiltration in the upstream catchment area affecting the CCR surface
impoundment. In addition, EPA expects supporting documentation to
address the selection and basis of an appropriate run-off model and an
appropriate run-on or run-off routing model; the identification and
characterization of any intake or decant structures of the CCR surface
impoundment; an appropriate characterization of the spillway(s) of the
CCR surface impoundment and their capacity; and characterization of
downstream hydraulic structures which ultimately receive the discharge
from the CCR surface impoundment. Finally, the owner or operator must
comply with the recordkeeping, notification and internet requirements
specified in the rule for the plan.
    The owner or operator may amend the written inflow design flood
control system plan at any time prior to receipt of CCR in the CCR
unit, during the operating life of the CCR unit, during closure of the
CCR unit, or following closure of the CCR unit provided the revised
plan is placed in the facility's operating record. The owner or
operator must amend the written inflow design flood control system plan
whenever there is a change in the conditions that would substantially
affect the written plan in effect. The owner or operator of the CCR
surface impoundment must also periodically update the inflow design
flood control system plan. The owner or operator must review or update
an existing plan at a frequency no less than every five years. Changes
in storm characteristics (e.g., intensity and duration) and upstream
catchment area characteristics, hazard potential classifications, as
well as build-out, operational changes, and diminishing available
capacity, all have the potential to influence inflow design flood
volumes and therefore the effectiveness of the existing inflow design
flood control systems. A periodic review of the plan to address these
and other factors is necessary to ensure that the hydrologic and
hydraulic capacity of the unit is maintained over time. An update of
the inflow design flood control system plan should document any
modifications pertinent to the inflow design flood control system.
    The owner or operator may amend the written inflow design flood
control system plan at any time and must place the revised plan in the
facility's operating record. However, the owner or operator must amend
the written inflow design flood control system plan whenever there is a
change in the conditions that would substantially affect the written
plan in effect. The owner or operator of the CCR unit must also review
and, where necessary, update an inflow design flood control system plan
every five years. As part of this review, the owner or operator must
obtain certification from a qualified professional engineer must
certify that the inflow design flood control system plan, and any
subsequent amendments continues to meet the requirements of the rule.
The date of completion of the initial plan is the basis for
establishing the deadline to complete the first subsequent plan. The
owner or operator may complete any required plan prior to the required
deadline, and must place the completed plan into the facility's
operating record within a reasonable amount of time.

I. Operating Criteria--Inspection Requirements for CCR Surface
Impoundments

    EPA proposed structural stability requirements for CCR surface
impoundments based on the long-standing MSHA requirements, with only
minor modifications. These structural stability requirements were
covered in various sections of the proposed rule (see specifically
proposed Sec. Sec.  257.71, 257.72, 257.83, and 257.84). Section 257.83
addressed requirements for periodic inspections of CCR surface
impoundments. In proposing these requirements, the Agency concluded
that periodic inspections were critical to ensure that any problems
relating to structural stability are quickly identified and remedied to
prevent catastrophic releases, such as occurred at Martins Creek,
Pennsylvania and TVA's Kingston, Tennessee facility. The proposed rule
required owners or operators to conduct: (1) Weekly inspections to
detect potentially hazardous conditions or structural weakness; and (2)
annual inspections to assure that the design, operation, and
maintenance of the surface impoundment was in accordance with generally
accepted engineering standards. EPA proposed that weekly inspections be
conducted by a person qualified to recognize specific signs of
structural instability and other hazardous conditions by visual
observation and, if applicable, to monitor instrumentation. The
proposed rule also required annual inspection reports from an
independent registered professional engineer, certifying that the
design, operation, and maintenance of the CCR surface impoundment was
in accordance with generally accepted engineering standards. Consistent
with the annual inspection requirements, EPA, as part of its
recordkeeping requirements also proposed that owners or operators of
CCR surface impoundments annually document and report on, among other
things: (1) Changes in the geometry of the impounding structure; (2)
location and type of instrumentation monitoring the unit; (3) the
minimum, maximum and present depth and elevation of the impounded
water, sediment or slurry for the reporting period; and (4) storage
capacity of the impounding structure (see 75 FR at 35246).
    The annual inspection provisions also required that if a
potentially hazardous

condition developed, the owner or operator must immediately take
several actions: Eliminate the potentially hazardous condition; notify
potentially affected persons and state and local first responders;
notify and prepare to evacuate, if necessary, all personnel from the
property who may be affected by the potentially hazardous condition(s);
and direct a qualified person to monitor all instruments and examine
the structure at least once every eight hours, or more often as
required by an authorized representative of the state. Finally, the
proposed rule required that inspection and monitoring reports be
maintained in the facility operating record and placed on the
facility's publicly accessible Internet site as well as promptly
reporting the results of the inspection or monitoring to the state.
    EPA specifically requested comment on whether to cover all CCR
impoundments for stability (including the inspection requirements),
regardless of height and storage volume, whether to use the cut-offs in
the MSHA regulations, or whether other regulations, approaches, or size
cut-offs should be used. The Agency further requested commenters who
believed that other regulations or size cut-offs should be used (and
not the size cut-offs established in the MSHA regulations) to provide
the basis and technical support for their position. (75 FR 35176,
35223). In response to EPA's general solicitation for alternative size
cut-offs, the Agency received little response. However, many commenters
questioned EPA's decision to require inspections for all CCR surface
impoundments, given that the other structural stability requirements
were triggered only if the CCR unit exceeded the proposed size
threshold (consistent with MSHA requirements). Commenters argued that
there was no basis to require inspections of all CCR surface
impoundments given that units below the specified size threshold had a
much lower risk of catastrophic failure. A more limited requirement the
commenter's argued, was supported by MSHA's decision to regulate only
those ``larger'' sized units. Other commenters argued that inspection
timeframes should take into account site specific conditions at the
site and be based on the recommendations of an independent registered
professional engineer. Commenters reasoned that while, in theory, a
short inspection interval (i.e., a weekly inspection) should increase
the chances of finding an adverse condition, the judgment of a
qualified professional engineer to establish the frequency and focus,
as well as the purpose of the dam safety inspection was a far more
effective method for detecting and preventing the development of a
potentially adverse situation. Still other commenters questioned the
overall value of a weekly inspection if, as proposed, no documentation
of the results was required.
    In reviewing the proposed regulatory language, it appears an error
was made. Although the preamble generally stated that the proposed
regulatory requirements addressing stability (which included
inspections) applied only to those CCR surface impoundments exceeding
the specified size threshold established by the MSHA regulations, the
regulatory text required inspections for all CCR units. The final rule
requires weekly general inspections and monthly instrumentation
inspections to be conducted for all CCR surface impoundments. Periodic
inspections of all CCR units are a necessary practice to ensure that
the overall structural integrity of the CCR unit is maintained and that
actual and potential structural weaknesses and other hazardous
conditions are quickly identified and remediated throughout the active
life of the unit. All CCR surface impoundments pose some risk of
release--whether from a catastrophic failure or from a more limited
structural failure, such as occurred at Duke Energy's Dan River plant.
Periodic inspections are a generally accepted, prudent engineering
practice that will significantly reduce the risks of such failures;
during the Assessment Program, EPA discovered that many facilities
routinely conduct some sort of periodic inspection and monitoring,
although the frequency varied widely between facilities. The final rule
merely codifies this practice, by establishing a consistent minimum
timeframe. EPA is therefore requiring that all CCR surface impoundments
be inspected by a qualified person both weekly (for visual signs of a
potentially adverse condition) and monthly (for instrumentation
monitoring). Consistent with the proposed rule, EPA is also requiring
annual inspections for all CCR surface impoundments that exceed the
specified size threshold of: (1) A height of five feet and a storage
capacity of 20 acre-feet; or (2) a height of 20 feet, must also be
inspected no less than annually by a qualified professional engineer.
These inspection requirements are generally being promulgated as
proposed, with minor technical clarifications.
    The final inspection requirements have been drawn heavily from
guidelines established by FEMA for dam safety, under which maintaining
structural integrity involves continuous evaluation of the unit, based
on periodic inspections. To be most effective, FEMA suggests, and EPA
concurs, that inspections be varied with respect to both the time
interval between inspections and the level of detail of the inspection.
FEMA guidance, in part, suggests that inspections can be categorized as
either: Visual observations to identify abnormal conditions (i.e.,
informal inspections); field inspections by a professional engineer
(i.e., intermediate inspections); and a technical review to determine
if the unit meets current and accepted design criteria and practices
(i.e., formal inspection).\114\ In general, FEMA recommends that
inspections focusing on visual observations should be conducted often
(e.g., weekly) while more substantive technical evaluation should be
conducted every year to every five years depending on the engineering
analyses required. (See also the preamble discussion on the
requirements specified in Sec. Sec.  257.73 and 257.74 of this rule, in
particular the discussion addressing the five year time interval for
structural stability and factor of safety reassessments.)
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    \114\ See ``Federal Guidelines for Dam Safety'' Federal
Emergency Management Agency. (Reprinted April 2004).
---------------------------------------------------------------------------

    For the reasons discussed above, EPA has concluded, consistent with
FEMA guidelines, that routine inspections of all CCR units are
necessary to ensure that the units are safely operated and that issues
that could disrupt the safety and continuing operation of these units
are promptly identified and remediated. Accordingly, the final rule
requires both weekly inspections and monthly instrumentation
inspections to be conducted at all CCR surface impoundments to confirm
that they are operating safely. These inspections must be conducted by
a qualified person trained to recognize specific signs of structural
instability and other hazardous conditions by visual observation and
if, applicable monitor instrumentation. EPA is also retaining the
annual inspection requirement for CCR surface impoundments exceeding
the specified size threshold established in this rule. This inspection
must be conducted and certified by a qualified professional engineer.
Units exceeding this size threshold pose a higher degree of risk of
release of CCR to the environment than other types of CCR surface
impoundments (e.g., incised or ``small'' CCR units) and as such warrant
additional regulatory control and oversight.

    The final rule requires that both weekly inspections of the CCR
unit and monthly monitoring of CCR unit instrumentation be initiated
within 6 months of the publication of the rule.
    Within nine months of the publication of the rule, the owner or
operator must complete the initial annual inspection of the CCR unit.
Initial annual inspection requires the retaining of a professional
engineer along with the familiarization of the engineer with the
facility and CCR units. Additionally, the annual inspection should not
be conducted unless weekly inspection and monthly instrumentation
monitoring has been initiated and established in order to generate a
body of information for the professional engineer to consider.
Furthermore, in some cold-weather regions of the United States, weather
may inhibit adequate inspection of CCR units, whether through snow or
ice cover. EPA is establishing a timeframe of nine months after the
publication of the rule so as to allow for adequate weather conditions
for inspection.
1. Surface Impoundment Inspection Requirements
a. Weekly Inspections
    As presented in the proposed rule and finalized here, this rule
requires all CCR surface impoundments to be examined by a qualified
person at least once every seven days for any appearance of actual or
potential structural weakness or other conditions that are disrupting
or that have the potential to disrupt the operation or safety of the
CCR unit. The results of the inspection by a qualified person must be
recorded in the facility's operating record.
    Weekly inspections are intended to detect, as early as practicable,
signs of distress in a CCR surface impoundment that may result in
larger, more severe conditions. They are also designed to identify
potential issues with hydraulic structures that may affect the
structural safety of the CCR surface impoundment and impact the
hydraulic and hydrologic capacity of the CCR surface impoundment. The
early detection of signs of structural weaknesses is an essential
preventative measure which helps to impede structural failure. The
required weekly inspections are designed to identify such signs of
structural weakness before they develop into larger, debilitating
concerns in the structural stability of the dike.
    Appearances of structural weakness may include, but are not limited
to: (1) Excessive, turbid, or sediment-laden seepage; (2) signs of
piping and other internal erosion; (3) transverse, longitudinal, and
desiccation cracking; (4) slides, bulges, boils, sloughs, scarps,
sinkholes, or depressions: (5) Abnormally high or low pool levels; (6)
animal burrows; (7) excessive or lacking vegetative cover; (8) slope
erosion; and (9) debris.
    In addition, EPA is also adopting a new provision that requires the
qualified person to inspect the discharge of all outlets of hydraulic
structures which pass underneath the base of the CCR surface
impoundment or through the dike of the CCR unit for abnormal
discoloration, flow, or discharge of debris or sediment. The
requirement is being added to aid in the identification of any internal
or sub-surface issues which cannot be reasonably identified in a
routine visual inspection. Abnormal discharges from hydraulic
structures are often an indication of potential issues with the sub-
surface or internal integrity of the structure. Hydraulic structures,
particularly corrugated metal pipe, are subject to deterioration and
corrosion over time and, as deterioration proceeds, the hydraulic
structure becomes more susceptible to collapse, translation, or
malfunction. Issues with hydraulic structures within the dike may
exacerbate structural or operational issues with the CCR surface
impoundment due to the significant internal deterioration of the dike
via the hydraulic structure. As an example, on February 2, 2014, Duke
Energy's Dan River Fossil Plant experienced a structural collapse of a
corrugated metal storm water discharge pipe which passed underneath the
interior of a CCR surface impoundment. The subsequent collapse of the
base of the CCR surface impoundment led to a massive release of CCR to
the environment. Additionally, the adjacent dike of the CCR surface
impoundment was severely damaged due to the erosion of the upstream
slope.
    Further, an owner or operator may want to consider inspections
outside of the weekly, seven-day schedule if an unanticipated event,
such as a flood, earthquake, or vandalism occurs on the site. While
rare in occurrence, these events may increase the chances that a
potential structural stability issue has arisen. Prudent CCR management
practices dictate that a visual assessment is warranted after such
events. For example, after a large flood (considered a flood with a
return period of equal or greater frequency of ten years) there is
potential for damage, including structural damage to the CCR surface
impoundment, caused by increased reservoir levels that inundate areas
infrequently inundated. The slopes of the dike should be inspected to
ensure that no significant erosion has occurred due to the flood, or
that any large debris or sediment has been deposited on the dike. An
inspection should also be conducted following an earthquake where
earthquake damage is observed or can be reasonably expected, where
ground motion is felt at the CCR surface impoundment or in nearby
locations, or following established magnitude-epicenter distance
relationships.\115\
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    \115\ The U.S. Army Corps of Engineers have developed useful
criteria for post-earthquake inspections, specifically their
published magnitude-epicenter distance criteria in Table 11.1 of
``Safety of Dams--Policy and Procedures,'' ER 1110-2-1156, 31 March
2014.\115\ The criteria stipulate when the dam (or in the case of
this rule, CCR surface impoundment) should be inspected.
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b. Monthly Instrumentation Inspection
    In a departure from the proposed rule, EPA is requiring the
monitoring of all instrumentation supporting the operation of the CCR
unit to be conducted by a qualified person no less than once per month.
This is a change from the proposal which required instrumentation to be
monitored no less than every seven days.
    Many commenters argued that requiring inspections every seven days
was excessive, and that, based on FEMA guidelines for dam safety, a
more reasonable timeframe would be once per month for CCR surface
impoundments with a hazard potential rating of ``high'' and quarterly
for those CCR surface impoundments with a hazard potential rating of
``significant.'' In considering these comments, the Agency was
influenced by a number of factors including the FEMA guidelines
suggested by the commenters. Also weighing heavily in EPA's decision
were the observations made as part of the Assessment Program, which
revealed that many CCR units are equipped with only ``basic'' measuring
devices such as piezometers and pool elevation and freeboard
instrumentation and not the more sophisticated (i.e., sensitive)
measuring devices for measuring pressure, seepage, internal movement,
slope movement; and vibration. These findings strongly suggested to the
Agency that, given the status of current instrumentation employed at
CCR facilities, weekly monitoring would be excessive, impractical,
and--of greatest significance--unlikely to indicate any measurable
changes in structural stability in such a short timeframe. EPA,
therefore, agrees that a monthly timeframe is a more appropriate
interval for detecting discernible or significant changes in the
operation of the CCR

unit. EPA has not, however, differentiated between high, significant,
and low hazard potential CCR surface impoundments in the requirement
that instrumentation be monitored monthly, as commenters suggested.
Through the assessment effort, EPA identified that typically low hazard
potential CCR surface impoundments were monitored less frequently than
high- or significant hazard potential CCR surface impoundments by the
owner or operator. Additionally, these low hazard potential CCR surface
impoundments less commonly were equipped with sophisticated monitoring
instrumentation, including remote monitoring instrumentation which
would allow the owner or operator to monitor the unit from a remote
location. Based on these observations, along with the limited burden
that instrumentation monitoring places on the owner or operator, the
rule requires all CCR surface impoundments with instrumentation to be
monitored monthly.
c. Annual Inspections
    The rule requires owners or operators of any CCR surface
impoundments exceeding the MSHA size threshold (i.e., a height of five
feet or more and a storage volume of 20 acre-feet or more; or a height
of 20 feet or more) to conduct annual inspections of the CCR unit
throughout its operating life. These annual inspections are focused
primarily on the structural stability of the CCR surface impoundment
and must ensure that the operation and maintenance of the CCR surface
impoundment is in accordance with recognized and generally accepted
good engineering standards. Inspections must be conducted and certified
by a qualified professional engineer.\116\ Incised CCR surface
impoundments, as defined in Sec.  257.53 are not subject to the annual
inspection requirements. Incised units present lower risks of
structural failure, and so weekly inspections are sufficient to address
any risks associated with these CCR units.
---------------------------------------------------------------------------

    \116\ For purposed of this requirement, qualified means an
individual experienced in the operation and maintenance of dams and
who has been trained to recognize signs of concern and structural
weakness by visual observation, and if applicable, to monitor
instrumentation.
---------------------------------------------------------------------------

    Annual inspections of any CCR surface impoundment must include, at
a minimum: (1) A review of all previously generated information
regarding the status and condition of the CCR unit, including, but not
limited to, all operating records and publicly accessible internet site
entries, design and construction drawings and other documentation; (2)
a thorough visual inspection to identify indications of distress,
unusual or adverse behavior, or malfunction of the CCR unit and
appurtenant structures; and (3) a thorough visual inspection of
hydraulic structures underlying the base of the CCR unit and passing
through the dike of the CCR unit for structural integrity and continued
safe and reliable operation. Additionally, following each inspection,
the qualified professional engineer must prepare an inspection report
which documents the following: (1) Any changes in geometry of the
impounding structure since the previous annual inspection; (2) the
location and type of existing instrumentation and the maximum recorded
readings of each instrument since the previous annual inspection; (3)
the approximate minimum, maximum, and present depth and elevation of
the impounded water and CCR since the previous annual inspection; (4)
the storage capacity of the impounding structure at the time of
inspection; (5) the approximate volume of the impounded water and CCR
at the time of the inspection; and (6) any appearances of an actual or
potential structural weakness of the CCR unit, in addition to any
existing conditions that are disrupting or have the potential to
disrupt the operation and safety of the CCR unit and appurtenant
structures; and (7) any other change(s) which may have affected the
stability or operation of the impounding structure since the previous
annual inspection.
    This last set of requirements was originally presented in Sec.
257.84 of the proposed rule (i.e., recordkeeping requirements),
however, the Agency has moved these requirements to the annual
inspection section of the rule because (1) these requirements apply
only to CCR surface impoundments exceeding the specified size
threshold, rather than all CCR surface impoundments, as proposed; (2)
must be reported annually; and (3) are more appropriately housed in the
inspection section.
    The owner or operator of existing CCR surface impoundments must
ensure that the initial annual inspection by a qualified professional
engineer is completed and documented with a report no later than nine
months after the publication of the rule. EPA established this
timeframe for completing an initial annual inspection based on its
experience with the Assessment Program. In an effort similar to
conducting an initial annual inspection, the following tasks were
generally completed within three months: Retaining the services of a
qualified professional engineer, developing a scope of work, reviewing
existing documentation on the CCR unit, conducting a thorough field
inspection, and completing an inspection report. Owners and operators
of new CCR surface impoundment must commence annual inspections no
later than one year from the initial placement of CCR into the new
unit. An annual inspection is not required in any calendar year in
which the five year structural stability reassessment is also required
to be completed. (See Sec. Sec.  257.73 and 257.74.) The report which
the qualified professional engineer has certified must be placed in the
facility's operating record and placed on the facility's publicly
accessible internet site. An annual inspection is considered complete
when the inspection report has been placed in the facility's operating
record. Finally, if a deficiency is identified during an inspection,
the owner or operator must take immediate measures to remedy the
structural weakness or disrupting condition as soon as feasible.

J. Operating Criteria--Inspections for CCR Landfills

    Under 40 CFR part 258, EPA does not require specific inspection
requirements for MSWLFs. Rather, EPA relies on states to establish
their own inspection criteria and frequency of inspections to ensure
protection of human health and the environment. It is the Agency's
understanding that many states require owners or operators of MSWLFs to
conduct either daily, weekly, quarterly and annual inspections of these
units to ensure that the design, construction, operation, and
maintenance complies with all requirements. In addition, based on a
review of selected state regulations most states conduct state
inspections of operating landfills no less than annually.
    Under the proposed subtitle D option, EPA did not propose to
require mandatory inspections of new or existing landfills or any
lateral expansion. However, under the subtitle C option, EPA proposed
to apply the requirements of Sec.  264.303 to permitted CCR landfills.
Specifically, these requirements stated that CCR landfills while in
operation would be required to be inspected weekly and after storms to
detect evidence of any of the following: (1) Deterioration,
malfunctions, or improper operation of run-on and run-off control
systems; (2) proper functioning of wind dispersal control systems,
where present; and (3) the presence of leachate in and proper
functioning of the leachate collection and removal system where
present. (See proposed Sec.  264.1306, 75 FR 35257).

    Upon further evaluation, the Agency has decided, consistent with
the weekly inspection requirements proposed for CCR landfills under the
subtitle C option, as well as many state requirements for MSWLFs, to
require all existing and new CCR landfills and any lateral expansion to
conduct, at intervals not exceeding seven days, inspections by a
qualified person for any appearances of actual or potential structural
weakness or any other conditions which are disrupting or have the
potential to disrupt the operation or safety of the CCR landfill. In
addition, EPA is also requiring inspections by a qualified professional
engineer at intervals not exceeding one year to ensure that the design,
construction, operation, and maintenance of the CCR landfill is
consistent with recognized and generally accepted good engineering
standards. This inspection must include a review of all data in the
operating record as well as a visual inspection of the unit to identify
signs of distress or malfunction that is or potentially could affect
the safe operation of the unit. The qualified professional engineer
must then also prepare a report to identify and discuss the findings of
the inspection as well as a discussion of potential remedies for
addressing any deficiencies discovered during the inspection. The
Agency has concluded that all CCR landfills should be routinely
inspected to ensure that they are operating as designed and are being
maintained in compliance with the federal criteria.
    The Agency is promulgating these inspection requirements based on:
(1) A review of state municipal landfill inspection requirements; and
(2) comments from parties that clearly supported inspections of all CCR
landfills. The Agency reviewed MSWLF inspection checklists in a
selected number of states to assess the scope of these inspections. The
Agency also conducted a preliminary review of state MSWLF regulations
for New York, Pennsylvania, Ohio, Wisconsin, Illinois, Missouri, North
Dakota and California. All of these states require MSWLF owners or
operators to conduct a either daily, weekly, monthly, quarterly and
annual inspections addressing the following: (1) Proper placement of
the waste; (2) slope stability and erosion control; (3) surface water
percolation is minimized (i.e. reduce ponding); (4) liner systems and
leachate collection systems are properly operated and maintained; (5)
water quality monitoring systems are maintained and operating; (6) dust
is controlled; and (7) a plan is in place to promptly address and
correct problems and deficiencies discovered during the inspection. The
Agency also noted during its review of state regulations that states
reserve the right to inspect landfills at any time and routinely
conduct state inspections on a no less than annual basis. CCR landfills
present at least the same level of risks as MSWLFs, and while the
operations may differ, both operating systems are equally susceptible
to malfunction. Weekly inspections of all CCR landfills by a qualified
person are therefore equally necessary to ensure that groundwater
monitoring, run-on and run-off controls, liner systems, and leachate
collection systems are operated and maintained to reduce adverse
environmental and human health impacts.
    This rule also requires that owners or operators of all existing
and new CCR landfills and any lateral expansion conduct an annual
inspection, certified by a qualified professional engineer, to assure
that these units are designed, constructed, operated, and maintained
throughout their operating life to ensure protection of human health
and the environment. The Agency finds that annual inspections for these
units are justified for a number of reasons. First, CCR landfills are
large engineered units that require that a variety of design and
operating parameters be assessed to assure that the CCR landfill is
operating as designed. Of particular concern to the Agency is the fact
that coal ash is a fine grained material that may have the potential to
compact and clog leachate collection systems (see: ``Operations and
Maintenance Guidelines for Coal Ash Landfills'' Christopher Hardin, et.
al. 2011 World of Coal Ash Conference. May 2011). It is reasonable
therefore that the rule requires annual inspections to assure that
these liner and leachate systems are assessed to assure that they are
performing their functions as designed. Second, a formal annual
inspection would review data collected during weekly inspections and
determine if any remedial actions are need to address deficiencies.
Third, the annual review by a qualified professional engineer ensures
that a detailed level of engineering analysis of operating conditions
are evaluated which could lead to recommendations to address design or
operating issues that need attention.

K. Groundwater Monitoring and Corrective Action

    EPA is finalizing groundwater monitoring and corrective action
requirements to ensure that groundwater contamination at new and
existing CCR units will be detected and cleaned up as necessary to
protect human health and the environment. These requirements reflect
Congressional intent that protection of groundwater be a prime
objective of any new solid waste regulations. As stated in the
proposal, EPA's damage cases and risk assessments indicate there is
significant potential for CCR landfills and CCR surface impoundments to
leach hazardous constituents into groundwater, impair drinking water
supplies and cause adverse impacts on human health and the environment.
Indeed, groundwater contamination is one of the key environmental and
human health risks EPA has identified with CCR landfills and CCR
surface impoundments. Groundwater monitoring is a key mechanism for
facilities to verify that the existing containment structures, such as
liners and leachate collection and removal systems, are functioning as
intended. Thus, in order for a CCR landfill or CCR surface impoundment
to show no reasonable probability of adverse effects on health or the
environment, a system of routine groundwater monitoring to detect any
contamination from a CCR unit, and corrective action requirements to
address identified contamination, are essential.
    EPA proposed to require that a system of monitoring wells be
installed at all new and existing CCR units. The regulation would also
provide procedures for sampling these wells and methods for statistical
analysis of the analytical data derived from the well samples to detect
the presence of hazardous constituents released from these CCR units.
The Agency proposed a groundwater monitoring program consisting of
detection monitoring and assessment monitoring, and a corrective action
program. This phased approach to groundwater monitoring and corrective
action programs provides for a graduated response over time to the
problem of groundwater contamination as the evidence of such
contamination increases. This allows for proper consideration of the
transport characteristics of CCR constituents in groundwater, while
protecting human health and the environment.
    EPA largely based these proposed groundwater monitoring
requirements on those for MSWLFs in the 40 CFR part 258 criteria,
albeit with certain modifications to tailor the requirements to the
case at hand. In particular, the possibility that a state may lack a
permit program for CCR units made it impossible to include some of the
alternatives available in 40 CFR part 258, which establish alternative
standards that allow a state, as part of

its permit program to tailor the default requirements to account for
site specific conditions at the individual facility. EPA also sought to
tailor the proposed requirements for CCR units, by incorporating
certain provisions from the interim status regulations, which operate
in the absence of a permit, and by including in several of the proposed
requirements, a certification by an independent registered professional
engineer that the rule's requirements had been met.
    In the proposed rule, the Agency required facilities to install a
groundwater monitoring system that met a specified performance standard
and that consisted of a minimum of one upgradient and three
downgradient wells at all CCR units. EPA acknowledged in the proposal
that the design of an appropriate groundwater monitoring system is
particularly dependent on site conditions relating to groundwater flow,
and on the development of a system that has a sufficient number of
wells, installed at appropriate locations and depths, to yield
groundwater samples from the uppermost aquifer that represent the
quality of background groundwater that has not been affected by
contaminants from a CCR unit. EPA's existing requirements under 40 CFR
parts 258 and 264 recognize this, and because they operate in a
permitting context, these requirements provide more flexibility in
establishing groundwater monitoring systems. But because the same
guarantee of permit oversight is not available under the criteria
developed for the proposal, EPA proposed to establish a minimum
requirement based on the part 265 interim status regulations, which are
self-implementing. Long experience demonstrates that these monitoring
requirements will be protective of a wide variety of conditions and
wastes, and that facilities can feasibly implement these requirements.
EPA also noted that in many instances a more detailed groundwater
monitoring system will need to be in place, and EPA therefore proposed
requiring a certification by the independent registered professional
engineer that the groundwater monitoring system is designed to detect
all significant groundwater contamination.
    EPA also proposed to require that owners and operators of CCR units
establish consistent sampling and analysis procedures to determine
whether a statistically significant increase in the level of a
hazardous constituent(s) has occurred, indicating the presence of
groundwater contamination.
    As noted, EPA proposed a phased approach to monitoring. The first
phase is detection monitoring where indicators would be monitored to
determine whether groundwater was potentially being contaminated. The
parameters EPA proposed to be used as indicators of groundwater
contamination were the following: Boron, chloride, conductivity,
fluoride, pH, sulfate, sulfide, and total dissolved solids (TDS). In
selecting the parameters for detection monitoring, EPA chose
constituents that are present in CCR and would rapidly move through the
subsurface, and thus provide an early detection of whether contaminants
were migrating from the CCR unit. Under the proposed rule, monitoring
would be required no less frequently than semiannually.
    When a statistically significant increase over background levels is
detected for any of these parameters, the proposed rule required the
facility to begin an assessment monitoring program to determine if
releases of CCR constituents of concern had occurred. The parameters
that were proposed for assessment monitoring were aluminum, antimony,
arsenic, barium, beryllium, boron, cadmium, chloride, chromium, copper,
fluoride, iron, lead, manganese, mercury, molybdenum, pH, selenium,
sulphate (sic), sulfide, thallium, and total dissolved solids.
    The proposed rule also required that whenever monitoring results
indicate a statistically significant level exceeding the groundwater
protection standard for any of these parameters, the owner or operator
must start the process for cleaning up the contamination, and initiate
an assessment of corrective action remedies. The proposed rule required
that the assessment of correction action remedies be initiated within
90 days and then completed within 90 days.
    EPA proposed that the assessment of corrective measures must
consider a number of factors, including the effectiveness, performance,
and time needed for the potential remedies. As part of the assessment
of corrective measures, the owner or operator was required to identify
the source of the release. The owner or operator was also required to
gather data on plume definition, fate of the contaminants, stratigraphy
and hydraulic properties of the aquifer. The owner or operator also was
required to consider whether immediate measures to limit further plume
migration or measures to minimize further introduction of contaminants
to groundwater would be necessary. EPA also proposed to require the
owner or operator to provide notification of the corrective measures
assessment to the State Director, place the corrective measures
assessment in the operating record and on the owner's or operator's
publicly accessible internet site, and discuss the results of the
corrective measures assessment in a public meeting with interested and
affected parties.
    Based on the results of the corrective measures assessment, EPA
proposed to require the owner or operator to select a remedy based on a
number of factors, including: the long- and short-term effectiveness
and protectiveness of the potential remedy, along with the degree of
certainty that the remedy will prove successful; the effectiveness of
the remedy in controlling the source to reduce further releases; the
ease or difficulty of implementing a potential remedy; the degree to
which community concerns are addressed by a potential remedy; and
potential risks to human health and the environment from exposure to
contamination prior to completion of the remedy. The owner or operator
was also required to specify as part of the selected remedy a schedule
for initiating and completing remedial activities.
    Under the proposed rule, implementing the corrective action program
required the owner or operator to establish and implement a corrective
action groundwater monitoring program; implement the corrective action
remedy selected; and take any interim measures necessary to ensure the
protection of human health and the environment, all according to the
schedule the owner or operator developed during the assessment of
corrective measures.
    The proposed rule also required that the owner or operator must
demonstrate that concentrations of constituents have not exceeded the
groundwater protection standards for three consecutive years in order
to support a determination that the remedy is complete.
    The majority of the commenters supported ``appropriate groundwater
monitoring standards for CCR waste management units'' and the
development of such standards under a RCRA subtitle D framework.
Comments were received on various parts of the groundwater monitoring
scheme laid out in the proposed rule. The majority of comments received
requested EPA to provide ``more flexibility'' to the proposed
requirements. Many commenters wanted the states to be more involved
with the process and provided comments suggesting that additional
``flexibility,'' such as is provided in the 40 CFR part 258

regulations for MSWLFs as part of the permitting process, be extended
to CCR units. For example, commenters wanted states to have the
authority to add or drop monitoring constituents; approve alternative
schedules; modify the number of wells needed; allow variances; allow
alternatives to the point of compliance specified in the rule; employ
alternative methods to detect potential groundwater contamination, such
as leak detection systems; allow alternatives to the statistical
methods used to determine whether groundwater contamination has
occurred; and to replace the qualified professional engineer role in
the certification process.
    For the final rule, EPA has developed a groundwater monitoring
program that is flexible and allows facilities to design a system that
accounts for site specific conditions within specific parameters. The
final rule establishes an overall performance standard that the system
must meet, lays out the minimum requirements of an effective system,
and requires the owner or operator to design a system that achieves
that overall performance standard based on a full characterization of
site conditions.
    As described in more detail below, in certain cases, EPA was able
to develop performance standards to serve as ``more flexible''
alternatives to the technical specifications laid out in the proposal.
In these instances, the available information allowed the Agency to
develop performance standards that were sufficiently objective and
determinate that EPA could conclude that the 4004(a) standard would be
met nationwide.
    However, many of the commenters' requests related to alternatives
that would be less stringent than the minimum criteria laid out in the
proposal and were based on arguments that state regulators (or
facilities) should be allowed to ``tailor'' those requirements to sites
that did not need those particular requirements. As explained at length
in the proposal, EPA is concerned that provisions allowing such
modifications are particularly susceptible to abuse, since in many
cases the provisions could allow substantial cost avoidance. In the
absence of a mandated state oversight mechanism to ensure that the
suggested modifications are technically appropriate, these kinds of
provisions can operate at the expense of protectiveness. In Unit II of
this preamble, EPA explains the extent of our authority to establish
criteria under RCRA sections 1008(a)(3) and 4004(a), including the
implications associated with the lack of any authority to establish a
program analogous to part 258, which relies on approved states to
implement the federal criteria through a permitting program. As a
result of the statutory structure, this rule is self-implementing and
is designed to operate to ensure that facilities will manage CCR in a
manner that achieves the 4004(a) standard even in the absence of any
regulatory entity available to judge the reasonableness of the desired
alternatives. While some states currently do have programs for the
regulation of CCR, which in some cases may be more stringent than this
final rule, the federal program must be defensible on the record in
place at the time the final rule is adopted. Based on the current
rulemaking record, in most cases EPA lacked the information necessary
to defend the commenters' less stringent alternatives (i.e., the
commenters' requested ``flexibilities'') to the minimum technical
criteria specified in this rule for these units. Under both the
subtitle C and part 258 programs, EPA can rely on subsequent
proceedings to develop the information necessary to support such
tailoring. This is clearly neither contemplated nor authorized under
the regulatory program relevant to this rule.
    In addition, given the extremely technical nature of these
requirements, EPA remains concerned that such provisions would render
the requirements appreciably more difficult for citizens to effectively
enforce. Nevertheless, working within these constraints this rule
specifically allows the qualified PE to design a system that accounts
for site conditions within the parameters of the minimum technical
criteria, and EPA has added language to the regulation that expressly
clarifies this. Moreover, states that have programs can continue to
impose more stringent requirements, and thus can require, for example,
additional monitoring wells, monitoring of additional aquifers, and
inclusion of additional parameters to the detection monitoring list or
the assessment monitoring list. The following discussion addresses in
more detail the technical requirements under groundwater monitoring and
corrective action in the final rule.
1. Applicability
    Consistent with the provisions in the proposed rule, the final rule
requires a system of monitoring wells to be installed at all CCR
landfills, CCR surface impoundments and lateral expansions. Existing
CCR units must install the groundwater monitoring system, develop their
groundwater sampling and analysis procedures, develop background levels
for appendix III and appendix IV constituents, and begin detection
monitoring (Sec.  257.90 through Sec.  257.94) within two years of the
effective date of this rule. The proposed rule required that existing
CCR units comply with the groundwater monitoring requirements within
one year of the effective date. EPA proposed one year believing that it
would be feasible for facilities to install the necessary systems. EPA
also believed that a one year timeframe would ensure that existing CCR
disposal facilities begin monitoring groundwater as soon as possible,
so that releases from existing CCR units are detected and addressed.
Comments received on this issue argued that the one-year timeframe was
not sufficient to complete a hydrogeologic study and develop a
monitoring plan. Several commenters requesting more time mentioned
staffing shortages and limited contractor and lab resources. One state,
referencing its experience relating to development and implementation
of groundwater monitoring systems, said that a one year timeframe to
investigate, design and submit and obtain approval for the installation
of an effective groundwater monitoring system was unreasonable. Most
commenters thought that a timeframe of two years was reasonable. After
review of the comments received on this issue and careful reexamination
of the actual requirements in the final rule, EPA agrees that a one-
year timeframe is not feasible, and has decided to extend the
timeframes for completing installation of the system, including
background monitoring, to two years. As important as it is to begin
detecting and addressing releases to groundwater, it is equally
important that these complex systems be designed and installed
correctly. That generally entails a number of activities, many of which
must occur sequentially, including: determining the uppermost aquifer,
deciding whether to install a single or multi-unit monitoring system,
collecting and evaluating hydrogeological information that can be used
to model the site, characterizing the site geology, characterizing the
groundwater flow beneath the site, determining the flow direction and
hydraulic gradient, establishing horizontal and vertical flow
direction, determining hydraulic conductivity, determining groundwater
flow rate, determining the monitoring wells placement, selecting the
drilling method, designing the monitoring wells, developing sampling
and analysis procedures, choosing a statistical method for evaluating
the data and

beginning detection monitoring. We also recognize that in some states,
the state may require the owner or operator to receive state approval
before they can install a groundwater monitoring system. Two years is a
more reasonable timeframe in which to carry out these activities. New
CCR landfills, new CCR surface impoundments and any lateral expansion
must comply with these same requirements (Sec. Sec.  257.90 through
257.94) before any CCR can be placed in the CCR unit.
    Consistent with the proposal, the final rule also requires that the
owner or operator of the CCR facility annually certify that each CCR
unit is in compliance with the groundwater monitoring and corrective
action provisions and provide a copy of this certification to the State
Director. Because this is a self-implementing rule that relies on
citizen enforcement, it is important for the owner or operator of the
facility to periodically document that they are in compliance with the
existing groundwater monitoring requirements, and an annual
certification is the easiest and most effective way to achieve this.
While the groundwater monitoring data will be made available on the
owner or operator's publicly accessible Web site and in the operating
record of the facility, the analysis of these data is complicated and
requires a certain level of scientific expertise to analyze the data
correctly. As such, a document that serves as both an interpretative
record of scientific analysis and regulatory compliance is critically
important to the successful implementation of a self-implementing rule
that is to be enforced exclusively by citizens and the states. For
similar reasons, the certification must also be placed in the operating
record, provided to the State Director, and posted on the owner or
operator's publicly accessible Web site.
    The groundwater monitoring requirements must be met throughout the
active life of the CCR unit, as well as during the closure and post-
closure care period.
    EPA has added a new provision to Sec.  257.90 to address the
corrective action requirements that apply when CCR have been released
into the environment, such as from the kind of structural failure that
occurred with TVA's Kingston Fossil Fuel plant release, or from the
kind of release that occurred in North Carolina at the Dan River. EPA
inadvertently drafted the corrective action requirements in the
proposed rule to apply exclusively upon detection of groundwater
contamination caused by a leaking unit. However, there is no reason to
establish different corrective action provisions for conducting clean-
up operations for different kinds of releases; the same general process
is applicable to all kinds of releases.
    The new provision requires that in the event of a release from a
CCR unit, the owner or operator must immediately take all necessary
measures to control the source(s) of releases so as to reduce or
eliminate, to the maximum extent practicable, further releases of
contaminants into the environment. The owner or operator of the CCR
unit is also required to comply with all of the relevant corrective
action requirements in Sec. Sec.  257.96, 257.97, and 257.98.
2. Groundwater Monitoring System Requirements
    EPA received comments that supported establishing more prescriptive
requirements for the design of the groundwater monitoring system. For
example, one commenter argued that three downgradient wells are
insufficient to ensure detection of leakage from the very large
disposal units typically used for CCR; due to uncertainty in flow
directions, the perimeter of the CCR unit must be monitored on its
cross-gradient, as well as downgradient sides. The commenter suggested
that the minimum number of non-background monitoring wells should
instead be three, plus one for every 500 feet of downgradient and
cross-gradient perimeter of the CCR unit (i.e., if the perimeter length
adds up to 1200 feet, the minimum number of wells would be five), and
that wells should be spaced no more than 500 feet apart along the
downgradient and cross-gradient perimeter. EPA also received many
comments arguing that the minimum requirements were overly
prescriptive, and that the final rule should instead allow a
professional engineer or hydrologist to design ``an alternative, but
equally effective, groundwater monitoring program.'' The majority of
comments on groundwater monitoring systems requested that EPA not
promulgate requirements that would be incompatible with state
requirements.
    The final rule provisions are fundamentally the same as those in
the proposal, although EPA has also added language to the regulations
to better clarify how the requirements in the various sections
collectively operate. The final rule establishes a general performance
standard that all groundwater monitoring systems must meet: All
groundwater monitoring systems must consist of a sufficient number of
appropriately located wells (at least one upgradient and three
downgradient wells) in order to yield groundwater samples from the
uppermost aquifer that represent the quality of background groundwater
and the quality of groundwater passing the waste boundary. This is the
same performance standard included in the proposed rule. The objective
of a groundwater monitoring system is to intercept groundwater to
determine whether the groundwater has been contaminated by the CCR
unit. Early contaminant detection is important to allow sufficient time
for corrective measures to be developed and implemented before
sensitive receptors are significantly affected. To accomplish this, the
rule requires that wells be located to sample groundwater from the
uppermost aquifer at the waste boundary. These requirements have been
adopted without fundamental change from the proposal.
    Because hydrogeologic conditions vary so widely from one site to
another, the rule does not prescribe the exact number, location and
depth of monitoring wells needed to achieve the general performance
standard. Rather, the rule requires the owner or operator to install a
minimum of one upgradient and three downgradient wells, and any
additional monitoring wells necessary to achieve the general
performance standard of accurately representing the quality of the
background groundwater and the groundwater passing the waste boundary.
The number, spacing, and depths of the monitoring wells must be
determined based on a thorough characterization of the site, including
a number of specifically identified factors relating to the
hydrogeology of the site (e.g., aquifer thickness, groundwater flow
rates and direction). Further, any owner or operator who determines
that the specified minimum number of wells is adequate must provide a
factual justification for that decision. Factors that may substantiate
a reduced density of groundwater monitoring wells includes simple
geology (i.e., horizontal, thick, homogenous strata that are continuous
across site, with no fractures, faults, folds, or solution channels), a
flat and constant hydraulic gradient, uniform hydraulic conductivity,
low seepage velocity, and high dispersivity potential.
    In essence, the rule establishes a presumption that the minimum of
one upgradient and three downgradient wells is not sufficient, and
requires the owner or operator to rebut that presumption in order to
install only this minimum. This is fundamentally consistent with the
proposed rule, which required the installation of a system that would
achieve the general performance standard, as well as the

``minimum'' of one upgradient and three downgradient wells. The final
regulation merely makes more explicit that both of these requirements
must be met.
    EPA considered establishing a more prescriptive set of
requirements, including a specified number, location, and design of
monitoring wells, but because of the highly site specific nature of
developing an adequate groundwater monitoring system, determined that
it lacked sufficient information to be able to design a single
groundwater monitoring system that would be nationally protective at
all sites. A properly designed system must account for many variables,
most of which are highly dependent on the individual characteristics of
the unit and the facility site. Consequently, the final rule leaves the
exact system design to be determined by those at the site, including a
qualified professional engineer, who can tailor the design of the
system to the unit and site conditions.
    Nevertheless, EPA is confident that the parameters laid out in the
regulation will ensure that the design of groundwater monitoring
systems at CCR facilities will be protective. As a practical matter,
EPA expects that there will be few cases, if any, where four wells will
be sufficient, given that this requirement was originally developed for
hazardous waste management units that are typically much smaller than
CCR units. As mentioned above, a small unit with simple geology, a flat
and constant hydraulic gradient, uniform hydraulic conductivity, low
seepage velocity, and high dispersivity potential would be the type of
unit for which the minimum number of wells could be sufficient to meet
the overall performance standard. Although EPA is finalizing a
requirement for one upgradient and three downgradient wells as a
regulatory minimum, the Agency expects large CCR units to have many
more wells because most CCR sites have hydrologic settings that are too
complex for the regulatory minimum to be adequate. Facilities with
large CCR units could have as many as thirty or more downgradient
wells. This is because the placement and spacing of detection
monitoring wells along the downgradient perimeter of the CCR unit must
be based on the abundance, extent, and physical/chemical
characteristics of the potential contaminant pathways. All potential
pathways need to be monitored.
    Therefore, even though EPA is not requiring a specific number of
wells, the Agency is confident that the combination of the requirements
will ensure that protective groundwater monitoring systems will be
installed. The owner or operator is required to install a sufficient
number of wells to meet the performance standard in Sec.  257.91(a)(1)
and (2), provide a justification if they determine the required minimum
is adequate, and have a qualified professional engineer certify that
their groundwater monitoring system has been designed and constructed
to ensure that the groundwater monitoring will meet this performance
standard--i.e., accurately represent the quality of groundwater that
has not been affected by leakage from any CCR unit--that is,
groundwater from background wells and the quality of groundwater
passing the waste boundary.
    The final rule establishes certain parameters regarding the
location of the wells. Upgradient background wells must be located
beyond the upgradient extent of potential contamination. However,
groundwater quality in areas where the geology is complex can be
difficult to characterize. If the facility is new, groundwater samples
collected from both upgradient and downgradient locations prior to
waste disposal can be used to establish background water quality.
Downgradient wells to monitor for any contaminants leaking into the
groundwater must be located at the hydraulically downgradient perimeter
(i.e., the edge) of the CCR unit or at the closest practical distance
from this location.
    Determining background groundwater quality by sampling wells that
are not hydraulically upgradient may be necessary where hydrogeologic
conditions do not allow the owner or operator to determine which wells
are hydraulically upgradient (e.g., floodplains, where nearby surface
water can influence groundwater). In such cases, the rule allows the
owner or operator to establish groundwater quality at existing units by
locating wells that are not upgradient under certain conditions (Sec.
257.91(a)(1)). This provision may be used when hydrogeologic conditions
do not allow the owner or operator to determine which wells are
hydraulically upgradient and when sampling at other wells will provide
data establishing background groundwater quality that is equally or
more representative than that provided by upgradient wells. These
conditions could include one or more of the following:
     The facility is located above an aquifer in which
groundwater flow directions change seasonally.
     The facility is located near production wells that
influence the direction of groundwater flow.
     Upgradient groundwater quality is affected by a source of
contamination other than the CCR unit.
     The proposed or existing CCR unit overlies a groundwater
divide or local source of recharge.
     Geologic units present at downgradient locations are
absent at upgradient locations.
     Karst terrain or fault zones modify flow.
     Nearby surface water (e.g., rivers) influences groundwater
flow directions.
    Additionally, there is nothing in the rule that would prevent the
owner or operator from monitoring multiple aquifers in addition to the
uppermost significant aquifer. Certain site conditions warrant more
extensive monitoring requirements, as discussed in ``Technical Manual
Solid Waste Disposal Facility Criteria'', EPA530-R-93-017, USEPA,
November, 1993, Chapter 5, Subpart E, Ground-Water Monitoring and
Corrective Action.
    Each CCR unit must have its own groundwater monitoring system,
unless the owner or operator chooses to install a multiunit groundwater
monitoring system. The final rule specifies that if a multiunit system
is installed, it must be based on the consideration of several factors,
including the number, spacing, and orientation of the CCR units, the
hydrogeologic setting, the site history and the engineering design of
the CCR units. A multiunit groundwater monitoring system must be
equally capable of detecting background and groundwater contamination
at the waste boundary as an individual monitoring system. This
documentation must be certified by a qualified professional engineer.
Whether a single or multi-unit system has been installed, the
monitoring wells must be cased in a manner maintaining the integrity of
the borehole and must be maintained so as to meet design
specifications. Both of these provisions have been adopted from the
proposal without revision.
3. Sampling and Analysis Requirements
    EPA received comment on several aspects of its proposed
requirements for conducting groundwater sampling and analyses.
Specifically mentioned here, commenters raised concern about the number
of samples required to establish background concentrations and about
the statistical test methodologies specified in the proposal. As
discussed below, EPA has modified the rule to account for the issues
raised by these commenters. The sampling and analysis requirements in
the final rule have

otherwise been adopted from the proposed rule with only minor
clarifications.
    The rule provides procedures for sampling monitoring wells and
methods for the statistical analysis of groundwater monitoring of
appendix III (detection monitoring) and appendix IV (assessment
monitoring) constituents that may be released from CCR units. The
sampling and analysis program must include procedures and documentation
for sample collection (including the frequency, water level
measurements, well purging, field analyses, and sample withdrawal and
collection); sample preservation and handling (including sample
containers, sample preservation, sample storage and shipment); chain of
custody control; analytical procedures (appropriate methods can be
found in ``Test Methods for Evaluating Solid Waste, Physical/Chemical
Methods,'' SW-846 (USEPA, 1986), http://www.epa.gov/waste/hazard/testmethods/sw846/online/index.htm); and quality assurance/quality
control. More information and guidance can be found in ``Technical
Manual Solid Waste Disposal Facility Criteria,'' EPA530-R-93-017,
USEPA, November, 1993, Chapter 5, Subpart E, Ground-Water Monitoring
and Corrective Action, as well as the ``Unified Guidance Document:
Statistical Analysis of Groundwater Monitoring Data at RCRA
Facilities,'' March 2009, EPA 530/R-09-007.
    Similar to the approach used in designing a groundwater a number of
system, the final rule adopts a combination of a general performance
standard for groundwater sampling and analytical methods, along with
particular technical specifications that must be met. The general
performance standard requires that the method used must accurately
measure hazardous constituents and other monitoring parameters. In
addition, the rule specifies that groundwater elevations must be
measured in each monitoring well immediately prior to sampling. Also,
the rate and direction of the groundwater flow in the uppermost aquifer
must be determined each time groundwater is sampled. Further, the rule
specifies that the background groundwater quality must be established
at a hydraulically upgradient well for each of the monitoring
parameters or constituents required by the applicable groundwater
monitoring program, except as provided in Sec.  257.91. The number of
samples collected to establish groundwater quality data must be
consistent with the appropriate statistical procedures determined for
the specific statistical method chosen. The sampling must also be
conducted to account for both seasonal and spatial variability in
groundwater quality.
    To establish background levels, the proposed rule required that ``a
minimum of four independent samples from each background and
downgradient well must be collected and analyzed . . .'' 75 FR 35247-
35248 (proposed Sec. Sec.  257.93(f) and 257.94(b)). This is the same
sampling protocol that EPA adopted for both the subtitle C and part 258
groundwater monitoring requirements.
    EPA received comments criticizing this sampling protocol. Several
commenters stated that more than the required four samples were needed
in order to adequately represent background water quality and reduce
the number of false negatives. For example, one commenter argued that
EPA should require a minimum of one year of monthly monitoring of
background concentrations to characterize fluctuations in parameters
that will be evaluated statistically. The commenter claimed that this
would also help to ensure that quarterly monitoring events are properly
timed. Another comment stated that more data points and time were
needed to ensure statistical confidence in the data. By contrast,
another commenter objected to the requirement to obtain four
independent samples, arguing that this requirement was unnecessary and
should be deleted. The commenter argued that this requirement was
inconsistent with EPA's Unified Guidance (EPA, 2009) for Statistical
Analysis of Groundwater Monitoring Data at RCRA Facilities, which
specifies that replicate samples (i.e., multiple samples from the same
location during a given sampling event) should typically be limited to
the collection of two samples from the same location, rather than four.
Another commenter requested clarification on the number of samples
required when establishing background levels that would serve as the
point of comparison in determining whether a statistically significant
increase over background levels had occurred.
    In response to these comments, EPA reviewed the available
information to determine whether revisions to the proposed requirements
were warranted.
    More recent information developed since the promulgation of the
subtitle C and part 258 groundwater monitoring requirements indicates
that statisticians now generally consider sample sizes of four or less
to be insufficient for good statistical analysis because the
observations are too few to adequately characterize the parameters of
the population. Tests utilizing a small background sample size have low
statistical performance in terms of power and per-test false positive
rates. In 2009, EPA issued a guidance document that accounts for more
recent scientific developments, ``Unified Guidance Document:
Statistical Analysis of Groundwater Monitoring Data at RCRA
Facilities,'' March 2009, EPA 530/R-09-007. This guidance recommends a
minimum of eight to ten independent background observations be
collected before performing the first statistical test. Sample sets of
20 are considered optimal.
    RCRA regulations are predicated on having appropriate and
representative background measurements. Samples should be tested
against data which best represent current uncontaminated conditions. In
addition, as discussed further in Unit VI.K.5 below, the detection of a
statistically significant increase over background concentrations of
the constituents of concern will have serious implications for unlined
surface impoundments, as these units will be required to close whenever
the facility makes such a finding. EPA is also cognizant of the
significant differences between the subtitle C and part 258 regulations
and the final regulations being promulgated for CCR units. Both the
subtitle C and the part 258 MSWLF requirements are implemented under
permit programs, under which regulatory authorities are specifically
authorized to establish more stringent requirements to account for
scientific advances (among other things). EPA expects that current
permits generally specify a greater number of samples than the minimum
laid out in the regulations (i.e., more than four) to determine
background concentrations. And because of this it is less critical that
those regulations (subtitle C and part 258) reflect the most current
science. By contrast, as previously discussed, the provisions adopted
under this rule are self-implementing, and will only be updated through
a subsequent rulemaking. Accordingly, the Agency agrees with the
comments that four samples would be insufficient and has amended the
rule to require the owner or operator to collect, at a minimum, eight
statistically independent and identically distributed (spatially
invariant) samples from each well for each monitoring parameter.
Although still a small sample size by statistical standards, eight
independent observations allows for minimally acceptable estimates of
variability and evaluation of trend and goodness-of fit. While more
samples, including a full

year of background monitoring, would be scientifically ideal, the
Agency selected eight samples by balancing the minimum number needed to
ensure the scientific accuracy of the results against the need to
expedite initiating the groundwater monitoring process of detecting
exceedances, along with any necessary corrective action at these
facilities.
    Background sampling (i.e., the requirement to collect eight
statistically independent samples from each well) must be completed for
all appendix III and IV constituents by the end of the 24 month period
to begin implementation of the groundwater monitoring program.
    EPA has also revised the regulatory text relating to the number of
samples that must be collected during subsequent sampling events after
background concentrations have been established to clarify how the
various provisions collectively operate. Consistent with the proposal,
the final rule requires the owner or operator to collect and analyze
the number of samples from each well necessary to be consistent with
the statistical test selected under Sec.  257.93(e) and with the unique
characteristics of the site, but at minimum, to collect at least one
sample from each background and downgradient well. In cases where the
groundwater is ``well-behaved'' one sample from each compliance well
could be all that the owner or operator would need to conduct the
necessary comparisons. But if statistical assumptions are not met
(e.g., the observations are not statistically independent or background
well data show trends) a comparison based on a single observation will
not yield a significant result, and will likely result in a false
positive. Further, detection monitoring tests, such as Student's t-
test, look at the difference between the sample means (e.g., upgradient
vs downgradient) to determine when an observed difference should be
considered more than a chance fluctuation. Every t-test assumes that
the observations that make up each data group meet the requirements of
statistical independence and stationarity. Therefore, the larger the
sample size the more significant the result. In other words, a facility
can choose to use only one observation (a group size of one), but the
chances are good that the result derived would be non-significant,
since there are many reasons sample means can vary. Consequently, it is
likely to be in the facility's best interest to take more samples than
the minimum, particularly in the early stages of monitoring. As
monitoring continues, each successive sample will be added to the
sampling data base, which will increase the confidence in the
statistical analyses performed. Additional guidance on sample size can
be found in the ``Unified Guidance Document: Statistical Analysis of
Groundwater Monitoring Data at RCRA Facilities,'' March 2009, EPA 530/
R-09-007.
    The requirements for applying statistical procedures in the rule
are the same as those included in the proposed rule, which were based
on the statistical procedures used in the MSWLF regulations. The rule
requires the owner or operator to select from among the listed
statistical procedures based on a determination that the test is
appropriate for evaluating groundwater at that site. The statistical
method chosen must be appropriate for the distribution of chemical
parameters or hazardous constituents. The rule has been revised to
include the clarification that normal distributions of data values
shall use parametric methods and non-normal distributions shall use
non-parametric methods. The rule identifies four statistical
procedures, along with an alternative procedure that must meet the
performance standard of Sec.  257.93(g). The four specific statistical
procedures provided in this final rule are: (1) A parametric analysis
of variance followed by multiple comparison procedures to identify
statistically significant evidence of contamination; (2) an analysis of
variance based on ranks followed by multiple comparison procedures to
identify statistically significant evidence of contamination; (3) a
tolerance or prediction interval procedure; and (4) a control chart
approach. The performance standard for the alternative method in
subsection (g) is the same as the performance standard in the proposal,
with minor revisions. EPA has deleted the performance standard
``protect human health and the environment'' in subsections (3), (4)
and (5). While that standard is perfectly appropriate in a context in
which a regulatory authority will apply the standard, EPA is concerned
that a qualified professional engineer will be unable to certify that
any alternative statistical method meets that standard. EPA received
comments from professional engineers raising concern about their
ability to certify that many of the requirements in the proposed rule
had been met without further specification or clarification. To address
those concerns, in those three provisions EPA has substituted a more
objective performance standard that more precisely defines the relevant
issues to be considered. Specifically, the subsections now specify that
those approaches must be ``at least as effective as any other approach
in this section for evaluating groundwater.''
    The data objectives of the monitoring, in terms of the number of
samples collected and the frequency of collection, must be consistent
with the statistical method selected. Guidance on selecting a specific
method is described in ``Unified Guidance Document: Statistical
Analysis of Groundwater Monitoring Data at RCRA Facilities,'' March
2009, EPA 530/R-09-007. The owner or operator must indicate in the
operating record the statistical method that will be used in the
analysis of groundwater monitoring results.
    The owner or operator must conduct the statistical comparisons
between upgradient and downgradient wells within 90 days of completion
of each sampling event and receipt of validated data. The statistical
comparison must be conducted in order to determine if a statistically
significant increase has occurred over background levels for each
parameter or constituent required in the particular groundwater
monitoring program that applies to the unit as determined under
Sec. Sec.  257.94(a) or 257.95(a). This has been adopted without
revision from the proposal.
    EPA is finalizing as proposed the prohibition in Sec.  257.93(b) on
field filtering groundwater samples because filtration of samples for
metals analyses will not provide accurate information concerning the
mobility of metals contaminants, the primary objective of groundwater
sampling. Metal contaminants may move through fractured and porous
media not only as dissolved species, but also as precipitated phases,
polymeric species, or adsorbed to particles of colloidal dimensions
(<10 microns). For an assessment of mobility, all mobile species must
be considered, including suspended or colloidal particles acting as
absorbents for contaminants. Filtration of groundwater samples for
metals analyses will not provide accurate information concerning the
mobility of metal contaminants because some mobile species in solution
are likely to be removed by filtration before chemical analysis.
Significant underestimations of mobility may result if filters
(typically 0.45 micron) are used to separate dissolved and particulate
phases.
    In its approach to sampling EPA is specifying in the final rule
that owners and operators use `total recoverable metals' concentrations
in measuring groundwater quality. Measurement of total recoverable
metals captures both the particulate fraction and dissolved

fraction of metals in natural waters. Exceedances of ambient water
criteria on a total recoverable basis are an indication that metal
loadings could be a stress to an ecosystem.
    One commenter argued that to prohibit field filtering would
potentially bias the results artificially high, particularly at sites
where low yielding formations or naturally high levels of turbidity in
groundwater are encountered. However, high turbidity can also be the
consequence of faulty well design and/or construction, which causes the
introduction of foreign materials (high turbidity) through created
fracture pathways. A properly designed well should allow for sufficient
groundwater flow for sampling, minimize the passage of materials into
the well, and exhibit sufficient structural integrity to prevent
collapse of the intake structure. It is vital that the well provide a
representative hydraulic connection to the geologic formation of
interest. Otherwise the water chemistry information cannot be correctly
interpreted in relation to groundwater flow or transport of chemical
constituents.
    Sampling with no filtration means that increased importance is
placed on proper well construction and purging sampling procedures to
eliminate or minimize sources of sampling artifacts. There should be
nothing in the well design that will lead to high levels of turbidity.
Groundwater sampling should be conducted utilizing EPA protocol low
stress (low-flow) purging and sampling methodology, including
measurement and stabilization of key indicator parameters prior to
sampling. For purposes of sampling, this final rule presumes that a
properly constructed well is capable of yielding groundwater samples
with low turbidity (<=5 Nephelometric Turbidity Units (NTU)), and by
knowing the cause of turbidity the qualified professional engineer will
be able to optimize well performance and reduce turbidity levels,
eliminating the need for filtration.
    EPA is revising Sec.  257.93(i)(2) to specify a time period of 90
days to determine if a statistically significant increase over
background concentrations of one of more of the contaminants has been
detected. As proposed, this section specified: ``Within a reasonable
period of time after completing sampling and analysis, the owner or
operator of the CCR landfill or surface impoundment must determine
whether there has been a statistically significant increase over
background at each monitoring well.'' Commenters pointed out that this
section of the regulation was very vague, and potentially
unenforceable. Several commenters suggested that once sampling and
analysis had been completed, 90 days would be a reasonable amount of
time to complete the statistical analysis to determine whether an
exceedance had occurred. No commenter suggested a longer period of time
was necessary and that timeframe is consistent with the Agency's
experience of the timeframes necessary to complete such analyses.
Accordingly, we have revised the provision to require the determination
of a statistically significant increase to be made within 90 days of
sampling and analysis.
4. Detection Monitoring Program
    With three exceptions, EPA is finalizing the regulatory provisions
relating to detection monitoring as proposed. The three revisions are
the appendix III list of monitoring parameters; the required number of
samples to determine background concentrations; and the availability of
an option to conduct detection monitoring on a less frequent basis due
to a lack of groundwater.
    The detection monitoring phase of the groundwater monitoring
program in this rule requires that the owners or operators of CCR units
establish background concentrations for all monitoring parameters
(appendix III and IV of part 257) and sample at least semiannually
during the active life of the facility, closure, and post closure
periods for a set of detection monitoring indicator parameters
(appendix III of part 257).
    In response to comments, EPA has revised appendix III to delete
conductivity and sulfide from the list of monitoring parameters and to
add calcium. Thus, the list of parameters included on the detection
monitoring list is boron, calcium, chloride, fluoride, pH, sulfate and
total dissolved solids (TDS). The Agency has deleted conductivity from
the detection monitoring program because it is merely a proxy for TDS,
which is already included on the list of parameters to analyze during
detection monitoring. The Agency has also deleted sulfide because it
occurs in groundwater only under strongly reducing conditions, and such
conditions are rather rare at CCR disposal facilities. Calcium is being
added to appendix III because it is an indicator of the extent of
leaching from fly ash and FGD gypsum and because of the strong
demonstrated link between the leaching of calcium and arsenic, which is
one of the primary risk drivers identified in the risk assessment.
    As discussed in the preceding section, in detection monitoring, a
minimum of eight independent samples from each background and
downgradient well must be collected and analyzed for the appendix III
and IV parameters no later than 24 months from the effective date of
the rule. During subsequent sampling events, at least one sample from
each background and downgradient well must be collected and analyzed,
although the total number of samples must be consistent with the
statistical procedures selected and with the performance standard in
Sec.  257.93(g). See discussion above in section 3. Sampling and
Analysis Requirements.
    Under the proposed rule, monitoring would be required no less
frequently than semiannually. In the final rule, semiannual sampling
remains the general requirement; however, in response to comments, EPA
has decided to include a provision that would allow an alternative
sampling frequency if there is not adequate groundwater to flow to
sample wells semiannually. Specifically, EPA received comment stating
that there may be instances where there simply is not enough water
available to collect and analyze on a semiannual basis, especially in
western climates where the rate of groundwater recharge may be too slow
or a lack of precipitation exists. The commenter also provided an
example demonstrating that mining practices in adjacent areas can
greatly alter the groundwater flow. Accordingly, EPA has included a
provision to address the situations where there is insufficient
groundwater available to collect and analyze samples around CCR units
on a semiannual basis.
    An owner or operator seeking to establish an alternative frequency
must demonstrate that less frequent monitoring is necessary based on
the following three factors: (1) Lithology of the aquifer and the
unsaturated zone; (2) hydraulic conductivity of the aquifer and the
unsaturated zone; and (3) groundwater flow rates. In addition, the rule
requires the owner or operator to demonstrate that any alternate
sampling frequency would be no less effective in ensuring that any
leakage from the CCR unit will be discovered within a timeframe that
does not materially delay the initiation of any necessary remediation
measures. The owner or operator must have a qualified professional
engineer certify that the alternative (i.e., less frequent) monitoring
will achieve this performance standard. The final rule also specifies
that any alternate frequency during the active life (including closure)
and the post-closure