[Federal Register Volume 80, Number 74 (Friday, April 17, 2015)]
[Rules and Regulations]
[Pages 21301-21501]
[FR Doc No: 2015-00257]

Vol. 80

Friday,

No. 74

April 17, 2015

Part II

Environmental Protection Agency

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40 CFR Parts 257 and 261

Hazardous and Solid Waste Management System; Disposal of Coal
Combustion Residuals From Electric Utilities; Final Rule

Federal Register / Vol. 80 , No. 74 / Friday, April 17, 2015 / Rules
and Regulations

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 257 and 261

[EPA-HQ-RCRA-2009-0640; FRL-9919-44-OSWER]
RIN-2050-AE81

Hazardous and Solid Waste Management System; Disposal of Coal
Combustion Residuals From Electric Utilities

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA or the Agency) is
publishing a final rule to regulate the disposal of coal combustion
residuals (CCR) as solid waste under subtitle D of the Resource
Conservation and Recovery Act (RCRA). The available information
demonstrates that the risks posed to human health and the environment
by certain CCR management units warrant regulatory controls. EPA is
finalizing national minimum criteria for existing and new CCR landfills
and existing and new CCR surface impoundments and all lateral
expansions consisting of location restrictions, design and operating
criteria, groundwater monitoring and corrective action, closure
requirements and post closure care, and recordkeeping, notification,
and internet posting requirements. The rule requires any existing
unlined CCR surface impoundment that is contaminating groundwater above
a regulated constituent's groundwater protection standard to stop
receiving CCR and either retrofit or close, except in limited
circumstances. It also requires the closure of any CCR landfill or CCR
surface impoundment that cannot meet the applicable performance
criteria for location restrictions or structural integrity. Finally,
those CCR surface impoundments that do not receive CCR after the
effective date of the rule, but still contain water and CCR will be
subject to all applicable regulatory requirements, unless the owner or
operator of the facility dewaters and installs a final cover system on
these inactive units no later than three years from publication of the
rule. EPA is deferring its final decision on the Bevill Regulatory
Determination because of regulatory and technical uncertainties that
cannot be resolved at this time.

DATES: This final rule is effective on October 14, 2015.

ADDRESSES: EPA has established three dockets for this regulatory action
under Docket ID No. EPA-HQ-RCRA-2009-0640, Docket ID No. EPA-HQ-RCRA-
2011-0392, and Docket ID No. EPA-HQ-RCRA-2012-0028. All documents in
these dockets are available at http://www.regulations.gov. Although
listed in the index, some information is not publicly available, e.g.,
Confidential Business Information (CBI) or other information whose
disclosure is restricted by statute. Certain other material, such as
copyrighted material, is not placed on the Internet and will be
publicly available only in hard copy form. Publicly available docket
materials are available either electronically in http://www.regulations.gov or in hard copy at the OSWER Docket, EPA/DC, WJC
West Building, Room 3334, 1301 Constitution Ave. NW., Washington, DC
20460. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m.,
Monday through Friday, excluding legal holidays. The telephone number
for the Public Reading Room is<PHONE_NUMBER>, and the telephone number
for the OSWER Docket is<PHONE_NUMBER>.

FOR FURTHER INFORMATION CONTACT: For questions on technical issues:
Alexander Livnat, Office of Resource Conservation and Recovery,
Environmental Protection Agency, 5304P; telephone number: (703) 308-
7251; fax number:<PHONE_NUMBER>; email address:
<EMAIL_ADDRESS>or Steve Souders, Office of Resource
Conservation and Recovery, Environmental Protection Agency, 5304P;
telephone number:<PHONE_NUMBER>; fax number:<PHONE_NUMBER>; email
address<EMAIL_ADDRESS>For questions on the regulatory impact
analysis: Richard Benware, Office of Resource Conservation and
Recovery, Environmental Protection Agency, 5305P; telephone number:
(703) 308-0436; fax number:<PHONE_NUMBER>; email address:
<EMAIL_ADDRESS>For questions on the risk assessment: Jason
Mills, Office of Resource Conservation and Recovery, Environmental
Protection Agency, 5305P; telephone number:<PHONE_NUMBER>; fax number:
(703) 308-7904; email address<EMAIL_ADDRESS>    For more information on this rulemaking please visit http://www.epa.gov/epawaste/nonhaz/industrial/special/fossil/index.htm.

SUPPLEMENTARY INFORMATION:

A. Does this action apply to me?

    This rule applies to all coal combustion residuals (CCR) generated
by electric utilities and independent power producers that fall within
the North American Industry Classification System (NAICS) code 221112
and may affect the following entities: Electric utility facilities and
independent power producers that fall under the NAICS code 221112. The
industry sector(s) identified above may not be exhaustive; other types
of entities not listed could also be affected. The Agency's aim is to
provide a guide for readers regarding those entities that potentially
could be affected by this action. To determine whether your facility,
company, business, organization, etc., is affected by this action, you
should refer to the applicability criteria discussed in Unit VI.A. of
this document If you have any questions regarding the applicability of
this action to a particular entity, consult the person listed in the
preceding FOR FURTHER INFORMATION CONTACT section.

B. What actions are not addressed in this rule?

    This rule does not address the placement of CCR in coal mines. The
U.S. Department of Interior (DOI) and, as necessary, EPA will address
the management of CCR in minefills in separate regulatory action(s),
consistent with the approach recommended by the National Academy of
Sciences, recognizing the expertise of DOI's Office of Surface Mining
Reclamation and Enforcement in this area. See Unit VI of this document
for further details. This rule does not regulate practices that meet
the definition of a beneficial use of CCR. Beneficial uses that occur
after the effective date of the rule need to determine if they comply
with the criteria contained in the definition of ``beneficial use of
CCRs.'' This rule does not affect past beneficial uses (i.e., uses
completed before the effective date of the rule.) See Unit VI of this
document for further details on proposed clarifications of beneficial
use. Furthermore, CCR from non-utility boilers burning coal are also
not addressed in this final rule. EPA will decide on an appropriate
action for these wastes through a separate rulemaking effort. See Unit
IV of this document for further details. Finally, this rule does not
apply to municipal solid waste landfills (MSWLFs) that receive CCR for
disposal or use as daily cover.

C. The Contents of This Preamble Are Listed in the Following Outline

I. Executive Summary
II. Statutory Authority
III. Background
IV. Bevill Regulatory Determination Relating to CCR From Electric
Utilities and Independent Power Producers
V. Development of the Final Rule--RCRA Subtitle D Regulatory
Approach

VI. Development of the Final Rule--Technical Requirements
VII. Summary of Major Differences Between the Proposed and Final
Rules
VIII. Implementation Timeframes for Minimum National Criteria and
Coordination With Steam Electric ELG Rule
IX. Implementation of the Minimum Federal Criteria and State Solid
Waste Management Plans
X. Risk Assessment
XI. Summary of Damage Cases
XII. Summary of Regulatory Impact Analysis
XIII. Uniquely Associated Wastes
XIV. Statutory and Executive Order Reviews

I. Executive Summary

    This rule establishes nationally applicable minimum criteria for
the safe disposal of coal combustion residuals in landfills and surface
impoundments. This section summarizes these criteria. Detailed
discussions of the criteria and the Agency's rationale for finalizing
these requirements are provided in Unit VI of this document.

A. What are coal combustion residuals?

    Coal combustion residuals (CCR) are generated from the combustion
of coal, including solid fuels classified as anthracite, bituminous,
subbituminous, and lignite, for the purpose of generating steam for the
purpose of powering a generator to produce electricity or electricity
and other thermal energy by electric utilities and independent power
producers. CCR includes fly ash, bottom ash, boiler slag, and flue gas
desulfurization materials. A description of the types of CCR can be
found in the proposed rule (see 75 FR 35137).
    CCR is one of the largest industrial waste streams generated in the
U.S. In 2012, over 470 coal-fired electric utilities burned over 800
million tons of coal, generating approximately 110 million tons of CCR
in 47 states and Puerto Rico. CCR may be generated wet or dry; however,
this composition may change after generation. Some CCR is dewatered
while other CCR is mixed with water to facilitate transport (i.e.,
sluiced). CCR can be sent off-site for disposal or beneficial use or
disposed in on-site landfills or surface impoundments. In 2012,
approximately 40 percent of the CCR generated was beneficially used,
with the remaining 60 percent disposed in surface impoundments and
landfills. Of that 60 percent, approximately 80 percent was disposed in
on-site disposal units. CCR disposal currently occurs at over 310
active on-site landfills, averaging over 120 acres in size with an
average depth of over 40 feet, and at over 735 active on-site surface
impoundments, averaging over 50 acres in size with an average depth of
20 feet.

B. Background

    The Agency first solicited comments on the regulation of CCR in a
proposed rule published in the Federal Register on June 21, 2010. This
proposal, under the Resource Conservation and Recovery Act (RCRA),
addressed the risks from disposal of CCR generated from the combustion
of coal at electric utilities and from independent power producers. Two
regulatory options were proposed. Under the first option, EPA proposed
to list CCR as special waste subject to regulation under subtitle C of
RCRA, when destined for disposal in landfills or surface impoundments.
Under this option, CCR would require ``cradle-to-grave'' management and
would be subject to requirements for, among other things, composite
liners, groundwater monitoring, structural stability requirements,
corrective action, closure/post closure care and financial assurance.
States would be required to adopt the rule before it went into effect
and a permitting program would be established with direct federal
oversight. The subtitle C option, as proposed, would also effectively
result in the closure of all CCR surface impoundments.
    Under the second option, EPA proposed to regulate the disposal of
CCR under subtitle D of RCRA by issuing minimum national criteria.
Similar to the subtitle C option, this option would require composite
liners, groundwater monitoring, structural stability requirements,
corrective action, and closure/post closure care. However, consistent
with the available statutory authority under subtitle D, EPA proposed
this option to be a self-implementing rule with no direct federal
oversight, with an effective date six months after publication in the
Federal Register. This option required all unlined surface impoundments
to either retrofit to a composite liner or close within five years.
    After reviewing all the comments and additional data received, EPA
is promulgating this final rule to regulate the disposal of CCR as
solid waste under subtitle D of RCRA. This rule addresses the risks
from structural failures of CCR surface impoundments, groundwater
contamination from the improper management of CCR in landfills and
surface impoundments and fugitive dust emissions. The rule has also
been designed to provide electric utilities and independent power
producers generating CCR with a practical approach for implementation
of the requirements and has established implementation timelines that
take into account, among other things, other upcoming regulatory
actions affecting electric utilities and site specific practical
realities. In order to ease implementation of the regulatory
requirements for CCR units with state programs, EPA is also providing
the opportunity for states to secure approval of its CCR program
through the State Solid Waste Management Plan (``SWMP''). EPA strongly
recommends that states take advantage of this process by revising their
SWMPs to address the issuance of the revised federal requirements in
this final rule, and to submit revisions of these plans to EPA for
review. EPA would then review and approve the revised SWMPs provided
they demonstrate that the minimum federal requirements in this final
rule will be met. In this way, EPA's approval of a revised SWMP signals
EPA's opinion that the state SWMP meets the minimum federal criteria.

C. What types of CCR units are covered by this rule?

    The final rule applies to owners and operators of new and existing
landfills and new and existing surface impoundments, including all
lateral expansions of landfills and surface impoundments that dispose
or otherwise engage in solid waste management of CCR generated from the
combustion of coal at electric utilities and independent power
producers. The requirements of the rule also apply to CCR units located
off-site of the electric utilities' or independent power producers'
facilities that receive CCR for disposal. In addition, the rule applies
to certain inactive CCR surface impoundments (i.e., units not receiving
CCR after the effective date of the rule) at active electric utilities'
or independent power producers' facilities, regardless of the fuel
currently used at the facility to produce electricity (e.g. coal,
natural gas, oil), if the CCR unit still contains CCR and liquids.
    The requirements do not apply to: (1) CCR landfills that ceased
receiving CCR prior to the effective date of the rule; (2) CCR units at
facilities that have ceased producing electricity (or electricity and
other thermal energy) prior to the effective date of the rule; (3) CCR
generated at facilities that are not part of an electric utility or
independent power producer, such as manufacturing facilities,
universities, and hospitals; (4) fly ash, bottom ash, boiler slag, and
flue gas desulfurization materials, generated primarily from the
combustion of fuels (including other fossil fuels) other than coal, for
the purpose of generating electricity unless the fuel burned

consists of more than fifty percent coal on a total heat input or mass
input basis, whichever results in the greater mass feed rate of coal;
(5) CCR that is beneficially used; (6) CCR placement at active or
abandoned underground or surface coal mines; or (7) municipal solid
waste landfills (MSWLF) that receive CCR.

D. What minimum national criteria are being established for CCR
landfills and CCR surface impoundments?

    This final rule establishes minimum national criteria for CCR
landfills, CCR surface impoundments, and all lateral expansions of CCR
units including location restrictions, liner design criteria,
structural integrity requirements, operating criteria, groundwater
monitoring and corrective action requirements, closure and post-closure
care requirements, and recordkeeping, notification, and internet
posting requirements.
    1. Location Restrictions. To ensure there will be no reasonable
probability of adverse effects on health or the environment from the
disposal of CCR in CCR landfills, CCR surface impoundments, and all
lateral expansions of CCR landfills and CCR surface impoundments
(together ``CCR units''), this final rule establishes five location
restrictions. The location criteria include restrictions relating to
placement of CCR above the uppermost aquifer, in wetlands, within fault
areas, in seismic impact zones, and in unstable areas. All of these
location restrictions require the owner or operator of a CCR unit to
demonstrate that they meet the specific criteria. As discussed
elsewhere in this preamble, the five location restrictions apply to all
new CCR landfills, all new and existing CCR surface impoundments, and
all lateral expansions of CCR units; however, existing CCR landfills
are only subject to the location restriction for unstable areas. Units
that do not meet these restrictions can retrofit or make appropriate
engineering demonstrations to meet this criteria. This final rule
requires owner or operators of existing CCR units that cannot make the
required demonstrations to close, while owners or operators of new CCR
units and all lateral expansions who fail to make the required
demonstrations are prohibited from placing CCR in the CCR unit.
    2. Liner Design Criteria. The final rule also establishes liner
design criteria to help prevent contaminants in CCR from leaching from
the CCR unit and contaminating groundwater. All new CCR landfills, new
CCR surface impoundments, and lateral expansions of CCR units must be
lined with composite liner, which is a liner system consisting of two
components--a geomembrane and a two-foot layer of compacted soil--
installed in direct and uniform contact with one another. The final
rule allows an owner or operator to construct a new CCR unit with an
alternative composite liner, provided the alternative composite liner
performs no less effectively than the composite liner. In addition, new
landfills are required to operate with a leachate collection and
removal system which is designed to remove excess leachate that may
accumulate on top of the composite (or alternative composite) liner.
Existing CCR landfills are not required to close or retrofit with a
composite (or alternative composite) liner and a leachate collection
and removal system. These existing CCR units can continue to receive
CCR after this rule is in effect; however, the CCR units must meet all
applicable groundwater monitoring and corrective action criteria to
address any groundwater releases promptly. Existing CCR surface
impoundments can also continue to operate as designed. However, if the
existing CCR surface impoundment was not constructed with a composite
(or alternative composite) liner or with at least two feet of compacted
soil with a specified hydraulic conductivity, the rule would require
the unit to retrofit or close if the CCR surface impoundment detects
concentrations of one or more constituents listed in appendix IV at
statistically significant levels above the groundwater protection
standard established by the rule.
    3. Structural Integrity Requirements. To help prevent the damages
associated with structural failures of CCR surface impoundments, the
final rule establishes structural integrity criteria for new and
existing surface impoundments (and all lateral expansions) as part of
the design criteria. While the applicability of the structural
integrity requirements to individual CCR surface impoundments vary
depending on factors such as dike heights and the potential for loss of
life, environmental damage and economic loss if there is a dike
failure, the final rule establishes requirements for owner or operators
to conduct a number of structural integrity-related assessments
regularly. These include: (1) Conducting periodic hazard potential
classification assessments to assess the potential adverse incremental
consequences that would occur if there was a failure of the CCR surface
impoundment; (2) conducting periodic structural stability assessments
by a qualified professional engineer to document whether the design,
construction, operation and maintenance is consistent with recognized
and generally accepted good engineering practices; and (3) conducting
periodic safety factor assessments to document whether the CCR unit
achieves minimum factors of safety for slope stability. If a CCR unit
required to conduct a safety factor assessment fails to demonstrate
that the unit achieves the specified factors of safety, the owner or
operator must close the unit. In addition, certain CCR surface
impoundments are required to develop an emergency action plan which
defines the events and circumstances involving the CCR unit that
represent an emergency and identifies the actions that will be taken in
the event of a safety emergency.
    4. Operating Criteria. The operating criteria include air criteria
for all CCR units, run-on and run-off controls for CCR landfills,
hydrologic and hydraulic capacity requirements for CCR surface
impoundments, and periodic inspection requirements for all CCR units.
These criteria address the day-to-day operations of CCR units and are
established to prevent health and environmental impacts from CCR units.
The air criteria address the pollution caused by windblown dust from
CCR units, and require owners and operators to minimize CCR from
becoming airborne at the facility. The run-on controls for CCR
landfills minimize the amount of surface water entering the unit that
will help prevent erosion, surface discharges of CCR in solution or
suspension, and will mitigate the generation of landfill leachate,
while run-off controls help prevent erosion, protect downstream surface
water from releases from the unit, and minimize storm water run-off
volume and velocity. CCR surface impoundments are subject to hydrologic
and hydraulic capacity requirements to ensure the unit can safely
handle flood flows, which will help prevent uncontrolled overtopping of
the unit or erosion of the materials used to construct the surface
impoundment. The final rule also requires periodic inspections of CCR
units to identify any appearance of structural weakness or other
conditions that are not consistent with recognized and generally
accepted good engineering standards.
    5. Groundwater Monitoring and Corrective Action. The groundwater
monitoring and corrective action criteria require an owner or operator
of a CCR unit to install a system of monitoring wells and specify
procedures for sampling these wells, in addition to methods for
analyzing the groundwater data collected, to detect the presence of

hazardous constituents (e.g., toxic metals) and other monitoring
parameters (e.g., pH, total dissolved solids) released from the units.
The final rule establishes a groundwater monitoring program consisting
of detection monitoring, assessment monitoring and corrective action.
Once a groundwater monitoring system and groundwater monitoring program
has been established for a CCR unit, the owner or operator must conduct
groundwater monitoring and, if the monitoring demonstrates an
exceedance of a groundwater protection standard for any of the
identified constituents in CCR, must initiate corrective action.
    6. Closure and Post-Closure Requirements. The closure and post-
closure care criteria require all CCR units to close in accordance with
specified standards and to monitor and maintain the units for a period
of time after closure, including the groundwater monitoring and
corrective action programs. These criteria are essential to ensuring
the long-term safety of closed CCR units. Closure of a CCR unit must be
completed either by leaving the CCR in place and installing a final
cover system or through removal of the CCR and decontamination of the
CCR unit. The final rule establishes timeframes to initiate and
complete closure activities, and authorize owners or operators to
obtain time extensions due to circumstances beyond the facility's
control. As discussed elsewhere in this preamble, the rule also
establishes alternative closure procedures in situations where an owner
or operator is closing a CCR unit, but has no alternative CCR disposal
capacity or is permanently closing the coal-fired boiler unit in the
foreseeable future. Finally, owners and operators are required to
prepare closure and post-closure care plans describing these
activities.
    7. Record Keeping, Notification, and Internet Posting Requirements.
The final rule requires owners or operators of CCR units to record
certain information in the facility's operating record. In addition,
owners and operators are required to provide notification to States
and/or appropriate Tribal authorities when the owner or operator places
information in the operating record, as well as to maintain a publicly
accessible internet site for this information.
    8. Severability. EPA intends that the provisions of this rule be
severable. In the event that any individual provision or part of this
rule is invalidated, EPA intends that this would not render the entire
rule invalid, and that any individual provisions that can continue to
operate will be left in place. The following tables provide a summary
of the specific technical requirements applicable to existing and new
CCR landfills, existing and new CCR surface impoundments, and all
lateral expansions of CCR units.

[GRAPHIC] [TIFF OMITTED] TR17AP15.000

[GRAPHIC] [TIFF OMITTED] TR17AP15.001

[GRAPHIC] [TIFF OMITTED] TR17AP15.002

E. When must owners or operators of CCR landfills and CCR surface
impoundments meet the minimum national criteria?

    The rule becomes effective six months after the publication date of
this rule. The final rule establishes timeframes for certain technical
criteria based on the amount of time determined to be necessary to
implement the requirements (e.g., installing the groundwater monitoring
wells and establishing the groundwater monitoring program). In
establishing these timeframes, EPA accounted for other Agency
rulemakings that are anticipated to also affect the owners or operators
of CCR units, namely the Effluent Limitations Guidelines and Standards
for the Steam Electric Power Generating Point Source Category (78 FR
34432; proposed rule issued June 7, 2013) and the Carbon Pollution
Emission Guidelines for Existing Stationary Sources: Electric Utility
Generating Units (79 FR 34830; proposed rule issued June 18, 2014).
Specifically, EPA developed implementation timeframes that would ensure
that owner or operators of CCR units would not be required to make
decisions about those CCR units without first understanding the
implications that such decisions would have for meeting the
requirements of all applicable EPA rules.

F. Deferral of Final Bevill Determination

    This rule defers a final Bevill Regulatory Determination with
respect to CCR that is disposed in CCR landfills and CCR surface
impoundments until additional information is available on a number of
key technical and policy questions. This includes information needed to
quantify the risks of CCR disposal, and the potential impacts of recent
Agency regulations on the chemical composition of CCR. The Agency also
needs further information on adequacy of the state programs.

G. Beneficial Use

    The final rule retains the Bevill exclusion for CCR that is
beneficially used, and provides a definition of beneficial use to
distinguish between beneficial use and disposal.

H. Implementation

    Because the regulations have been promulgated under sections
1008(a), 4004(a), and 4005(a) of RCRA, the rule does not require
permits, does not require states to adopt or implement these
requirements, and EPA cannot enforce these requirements. Instead,
states or citizens can enforce the requirements of this rule under
RCRA's citizen suit authority; the states can also continue to enforce
any state regulation under their independent state enforcement
authority. (For a more detailed discussion of EPA authorities under
RCRA and its relationship to this rule, see 75 FR 35128, June 21,
2010). EPA recognizes the significant role states play in implementing
these requirements and EPA strongly encourages states to revise their
SWMPs to show how these new criteria will be implemented. EPA would
then review and approve the revised plan provided it demonstrates that
the minimum federal requirements in this final rule will be met. In
this way, EPA's approval of a revised plan signals EPA's opinion that
the State's SWMP meets the minimum federal criteria. For a more
detailed discussion on the role of the states in implementing this
rule, please refer to Unit IX of this document.

I. Characterization of Baseline Affected Entities and CCR Management
Practices

    This action will affect CCR generated by coal-fired electric
utility plants in the NAICS industry code 221112 (i.e., the ``Fossil
Fuel Electric Power Generation'' industry within the NAICS 22
``Utilities'' sector code). Based on 2012 electricity generation data
published by the Energy Information Administration (EIA), the
Regulatory Impact Analysis (RIA) for this action estimated that a total
of 478 operational coal-fired electric utility plants in this NAICS
code could be affected by this action. These plants are owned by 242
entities consisting of 166 companies, 17 cooperative organizations, 58
state or local governments, and one federal agency. A sub-total of 81
of the 242 owner entities (i.e., 33 percent may be classified as small
businesses, small organizations, or small governments). The 478 coal-
fired electric utility plants operate a total of 1,045 CCR management
units (735 surface impoundments and 310 landfills). These 478 plants
generate 110 million tons of CCR, consisting of 201 plants (42 percent)
disposing in on-site landfills, 169 (35 percent) disposing in on-site
ponds, and 197 (41 percent) disposing in off-site landfills. Because
some plants use more than one CCR management method, these plant counts
exceed 478 total plants. In addition, 293 of the 478 plants supply CCR
for beneficial uses in at least 14 industries. Nineteen of the 293
plants solely supply CCR for beneficial uses. As of 2012, CCR
beneficial uses (i.e., industrial applications) involved about 52
million tons annually.

J. Summary of Estimated Regulatory Costs and Benefits

    The EPA estimated future regulatory compliance costs and expected
future human health and environmental protection benefits can be found
in the RIA document which is available from the docket for this action.
The estimated costs and benefits for the CCR rule are incremental to
the baseline (current) practices by the electric utility industry to
manage CCR in accordance with (a) existing state government
environmental regulations and (b) utility company CCR management
methods.
    The RIA estimates the cost of the rule over a 100 year period
because of: (1) CCR unit lifespans (40 years to 80 years of age); (2)
groundwater migration (estimated time to peak potential exposures of
CCR through groundwater migration to drinking water wells is 75 years);
and (3) latency periods for onset of illness after exposure to CCR,
which can average 20 years.
    The table below summarizes the estimated incremental costs and
benefits of the rule. The RIA estimates costs to comply with the 12
pollution control requirements associated with the rule, as well as
estimated monetized values for 11 expected benefits, and discusses 11
other non-monetized benefits.

       EPA Estimated Incremental Costs & Benefits of the CCR Rule
       [millions 2013$ over 100-year period of analysis 2015-2114]
------------------------------------------------------------------------
                                            3% Discount     7% Discount
                                               rate            rate
------------------------------------------------------------------------
A. Annualized Values
    A1. Total Costs.....................            $735            $509
    A2. Total monetized benefits........            $294            $236
    A3. Net Benefits (A2-A1)............          ($441)          ($441)
    A4. Benefit to Cost Ratio (A3/A1)...            0.40            0.46

B. Present Value
    B1. Total Costs.....................         $23,200          $7,260
    B2. Total monetized benefits........          $8,710          $3,360
    B3. Net Benefits (B2-B1)............       ($14,490)        ($3,900)
    B4. Benefit to Cost Ratio (B2/B1)...            0.38            0.46
------------------------------------------------------------------------

II. Statutory Authority

    These regulations are established under the authority of sections
1006(b), 1008(a), 2002(a), 3001, 4004, and 4005(a) of the Solid Waste
Disposal Act of 1970, as amended by the Resource Conservation and
Recovery Act of 1976 (RCRA), as amended by the Hazardous and Solid
Waste Amendments of 1984 (HSWA), 42 U.S.C. 6906(b), 6907(a), 6912(a),
6944 and 6945(a).
    RCRA section 1006(b) directs EPA to integrate the provisions of
RCRA for purposes of administration and enforcement and to avoid
duplication, to the maximum extent practicable, with the appropriate
provisions of other EPA statutes. Section 1006(b) conditions EPA's
authority to reduce or eliminate RCRA requirements on the Agency's
ability to demonstrate that the integration meets RCRA's protectiveness
mandate (42 U.S.C. 6005(b)(1)). See Chemical Waste Management v. EPA,
976 F.2d 2, 23, 25 (D.C. Cir. 1992).
    RCRA section 1008(a) authorizes EPA to publish ``suggested
guidelines for solid waste management.'' 42 U.S.C. 6907(a). RCRA
defines solid waste management as ``the systematic administration of
activities which provide for the collection, source separation,
storage, transportation, transfer, processing, treatment, and disposal
of solid waste.'' 42 U.S.C. 6903(28).
    Pursuant to section 1008(a)(3), the guidelines are to include the
minimum criteria to be used by the states to define the solid waste
management practices that constitute the open dumping of solid waste or
hazardous waste and are prohibited as ``open dumping''under section
4005. Only those requirements promulgated under the authority of
section 1008(a)(3) are enforceable under section 7002 of RCRA.
    RCRA section 4004 generally requires EPA to promulgate regulations
containing criteria for determining which facilities shall be
classified as sanitary landfills (and therefore not ``open dumps'').
The statute directs that, ``at a minimum, the criteria are to ensure
that units are classified as sanitary landfills only if there is no
reasonable probability of adverse effects on health or the environment
from disposal of solid wastes at such facility.'' 42 U.S.C. 6944(a).
    RCRA section 4005(a), entitled ``Closing or upgrading of existing
open dumps'' generally establishes the key implementation and
enforcement provisions applicable to EPA regulations issued under
sections 1008(a) and 4004(a). Specifically, this section prohibits any
solid waste management practices or disposal of solid waste that does
not comply with EPA regulations issued under RCRA section 1008(a) and
4004(a). 42 U.S.C. 6944(a). See also 42 U.S.C. 6903(14) (definition of
``open dump''). This prohibition takes effect ``upon promulgation'' of
any rules issued under section 1008(a)(3) and is enforceable through a
citizen suit brought pursuant to section 7002. As a general matter,
this means that facilities must be in compliance with any EPA rules
issued under this section no later than the effective date of such
rules, or be subject to a citizen suit for ``open dumping'' 42 U.S.C.
6945. RCRA section 4005 also directs that open dumps, i.e., facilities
out of compliance with EPA's criteria, must be ``closed or upgraded.''
    Section 7004 lays out specific requirements relating to public
participation in regulatory actions under RCRA. Subsection (b) provides
that ``[p]ublic participation in the . . . implementation, and
enforcement of any regulation under this chapter shall be provided for,
encouraged, and assisted by the Administrator.'' 42 U.S.C. 6974(b).

A. Regulation of Solid Wastes Under RCRA Subtitle D

    Solid wastes that are neither a listed nor characteristic hazardous
waste are subject to the requirements of RCRA subtitle D. Subtitle D of
RCRA establishes a framework for federal, state, and local government
cooperation in controlling the management of non-hazardous solid waste.
The federal role is to establish the overall regulatory direction, by
providing minimum nationwide standards that will protect human health
and the environment, and to provide technical assistance to states for
planning and developing their own environmentally sound waste
management practices. The actual planning and any direct implementation
of solid waste programs under RCRA subtitle D, however, remains a state
and local function, and the Act envisions that states will devise
programs to deal with state-specific conditions and needs. EPA has no
role in the planning and direct implementation of the minimum national
criteria or solid waste programs under RCRA subtitle D, and has no
authority to enforce the criteria. However, states are not required to
adopt solid waste management programs, and thus, Congress developed a
statutory structure that creates incentives for states to implement and
enforce the federal criteria, but that does not necessarily rely on or
require a regulatory entity to oversee or implement them. While
Congress developed the statutory structure to create incentives for
states to implement and enforce the federal criteria, it does not
require them to do so. As a result, subtitle D is also structured to be
self-implementing.
    RCRA sections 1008(a)(3) and 4004(a) delegate broad authority to
EPA to establish regulations governing the management of solid waste.
Under section 4004(a) EPA is charged with establishing requirements to
ensure that facilities will be classified as sanitary landfills ``only
if there is no reasonable probability of adverse effects on health or
the environment from the disposal of solid waste'' at the facility. Or
in other words, under section 4004(a) EPA is charged with issuing
regulations to address all ``reasonable probabilities of adverse
effects'' (i.e., all reasonably anticipated risks) to health and the
environment from the disposal of solid waste. Section 1008(a)(3)
expands EPA's authority to address the risks from any of the listed
activities. Specifically, EPA is authorized to establish requirements
applicable to ``storage, transportation, transfer, processing,
treatment, and disposal of solid waste.'' (42 U.S.C. 6907(a),
6903(28)).

    EPA interprets the standard in section 4004(a) to apply equally to
criteria issued under sections 1008(a)(3) and 4004(a); namely that the
criteria must ensure that a facility is to be classified as a sanitary
landfill, and thus allowed to continue to operate, ``only if there is
no reasonable probability of adverse effects on health or the
environment'' from either the disposal or other solid waste management
practices at the facility. Thus, under the combined authority conferred
by sections 1008(a)(3) and 4004(a), a facility is an ``open dump'' if
it engages in any activity involving the management of solid waste that
does not meet the standard in section 4004(a); or in other words, any
activity involved with the management of solid waste that presents a
reasonable probability of causing adverse effects on health or the
environment. EPA also interprets these provisions to authorize the
establishment of criteria that define the manner in which facilities
upgrade or close, consistent with the standard in section 4004(a), to
ensure there will be no reasonable probability of adverse effects on
health or the environment.
    As discussed previously, Congress created a regulatory structure
that limited EPA's role to the creation of national criteria that would
operate even in the absence of a regulatory entity to oversee or
implement the criteria. Under RCRA section 4005(a), upon promulgation
of criteria under section 1008(a)(3), any solid waste management
practice or disposal of solid waste that constitutes the ``open
dumping'' of solid waste is prohibited. The federal standards apply
directly to the facility (are self-implementing) and facilities are
directly responsible for ensuring that their operations comply with
these requirements. States are not required to incorporate or implement
these requirements under any state permitting program or other state
law requirement, and EPA is not authorized to impose such requirements,
directly or indirectly on the states. States and citizens may enforce
this prohibition (and therefore, the federal criteria) using the
authority under RCRA section 7002.\1\
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    \1\ EPA also may act if the handling, storage, treatment,
transportation, or disposal of such wastes may present an imminent
and substantial endangerment to health or the environment, pursuant
to RCRA section 7003.
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    The statute also creates incentives to states to implement the
criteria. Chief among the incentives is a greater role in
implementation and enforcement of the solid waste program, including to
a limited extent the ability to give facilities that are operating
within their state additional time to come into compliance with newly
promulgated EPA criteria. Specifically, if the facility is located in a
state with a plan that was approved under section 4003(b), the state
may grant the facility an extension of up to five years from the date
the final rule was published in the Federal Register to come into
compliance with EPA regulations, provided: (a) The facility is listed
in a state inventory of open dumps; and (b) the facility has
demonstrated that it has considered other public or private
alternatives for solid waste management to comply with the prohibition
on open dumping and is unable to utilize such alternative. For
facilities that meet these requirements, the state may establish a
``schedule for compliance'' which specifies a schedule of remedial
measures, including an enforceable sequence of actions or operations,
leading to compliance with the requirements ``within a reasonable time
(not to exceed five years from the date of publication of criteria
under section [1008] (a)(3) of this title).'' 42 U.S.C. 6945(a).
    As a consequence of this statutory structure--the requirement to
establish national criteria and the absence of any requirement for
direct regulatory oversight--to establish the criteria EPA must
demonstrate, through factual evidence available in the rulemaking
record, that the final rule will achieve the statutory standard (``no
reasonable probability of adverse effects on health or the
environment'') at all sites subject to the standards based exclusively
on the final rule provisions. This means that the standards must
account for and be protective of all sites, including those that are
highly vulnerable.

III. Background

A. EPA's Proposed Rule

    On June 21, 2010 (75 FR 35128), EPA proposed to regulate CCR under
RCRA to address the risks from the disposal of CCR generated from the
combustion of coal at electric utilities and independent power
producers. As described in the proposal, CCR are residuals generated
from the combustion of coal and include fly ash, bottom ash, boiler
slag (all composed predominantly of silica and aluminosilicates), and
flue gas desulfurization (FGD) materials (predominantly Ca-
SOX compounds) and can be managed in either wet (surface
impoundments) or dry (landfills) disposal systems. EPA noted in the
proposed rule that the constituents of most environmental concern in
CCR are metals, such as antimony, arsenic, barium, beryllium, cadmium,
chromium, lead, mercury, nickel, selenium, silver and thallium. EPA
also presented data showing numerous instances where these constituents
(especially arsenic) have leached at levels of concern from unlined and
inadequately clay-lined landfills and surface impoundments.
    In the proposal, EPA revisited its August 1993 and May 2000 Bevill
Regulatory Determinations regarding CCR generated at electric utilities
and independent power producers. The results from this effort led the
Agency to consider two primary options for the management of CCR and
thus, propose two alternative regulatory strategies. Under the first
option, EPA proposed to reverse its August 1993 and May 2000 Bevill
Regulatory Determinations (58 FR 42466 and 65 FR 32214 respectively)
regarding CCR and to list these residuals as special wastes subject to
regulation under subtitle C of RCRA when they are destined for disposal
in landfills or surface impoundments. Under this proposed option, CCR
would be regulated from the point of generation to the point of final
disposition and would generally be subject to the existing subtitle C
regulations at 40 CFR parts 260 through 268, as well as the permitting
requirements in 40 CFR part 270, and the state authorization process in
40 CFR parts 271-272. Among other things, the regulatory requirements
included waste characterization, location restrictions, liner and, if
applicable, leachate collection requirements for land disposal units,
fugitive dust controls, groundwater monitoring and corrective action
requirements, closure and post-closure care requirements, financial
assurance, permitting requirements, and recordkeeping and reporting
requirements. This option also imposed requirements on generators and
transporters of CCR destined for disposal, including manifesting (if
the CCR destined for disposal is sent off-site). However, in light of
practical difficulties in implementing certain subtitle C regulatory
requirements, EPA also proposed to revise selected requirements under
the subtitle C option. Consequently, EPA proposed, pursuant to its
authority under section 3004(x) of RCRA, modifications to the CCR
landfill and surface impoundment liner and leak detection system
requirements, the effective dates for the land disposal restrictions,
and the surface impoundment retrofit requirements. EPA also proposed to
establish new land disposal prohibitions and treatment standards for
both wastewater and non-wastewater forms of CCR. In part, the proposed

modifications to the treatment standards would result in the closure of
existing surface impoundments and the prohibition of all new surface
impoundments. (See 75 FR 35128 for a complete discussion of this
proposed option).
    Under the second option, EPA proposed to retain the August 1993 and
May 2000 Bevill Regulatory Determinations and to regulate CCR disposal
under subtitle D of RCRA by issuing national minimum criteria to ensure
the safe disposal of CCR in surface impoundments and landfills. Under
this option, CCR would remain classified as a non-hazardous RCRA solid
waste. EPA proposed to establish technical requirements, many of which
were nearly identical to the technical standards proposed under the
subtitle C option. The technical standards included, among other
things, locations standards, liner and leachate collection
requirements, groundwater monitoring and corrective action standards
for releases from the units, operating criteria, such as fugitive dust
control, closure and post-closure care requirements, and recordkeeping
and reporting requirements. Under this option, EPA did not propose to
establish regulatory requirements that would restrict the generation,
transportation, storage, or treatment of CCR prior to disposal, nor did
EPA propose to establish financial assurance requirements under
RCRA.\2\ Also, because of subtitle D's limitations, the proposed rule
did not require permits; nor could EPA enforce the national minimum
criteria. Rather, states or citizens could enforce the national minimum
criteria under RCRA's citizen suit authority, and states could continue
to enforce any state regulation that applies to CCR under their
independent state enforcement authority.
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    \2\ In the proposal, the Agency stated that the RCRA subtitle D
alternative did not include proposed financial responsibility
requirements and that any such requirements would be proposed
separately. The Agency solicited comment on whether financial
responsibility requirements under CERCLA section 108(b) should be a
key Agency focus under a RCRA subtitle D approach. While the Agency
received numerous comments urging the Agency to establish financial
responsibility as part of the subtitle D option, the CERCLA 108(b)
option did not receive significant support. As discussed in the
proposal and reiterated here, EPA will not be requiring financial
assurance requirements as part of this rule. The Agency however will
continue to investigate the use of other statutory authorities
(e.g., CERCLA) to establish financial responsibility requirements
for owners or operators of CCR landfills, CCR surface impoundments
and any lateral expansion.
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    The subtitle D proposed option was designed to be self-
implementing, meaning that the requirements were such that facilities
could comply with the regulatory requirements without the need to
interact with a regulatory authority. EPA sought to enhance the
protectiveness of the proposed option by requiring certified
demonstrations by an independent registered professional engineer to
provide verification that the regulatory requirements were being
adhered to. In addition, the option provided for state and public
notification of the certifications, as well as required posting of
certain information on a Web site maintained by the facility and in the
operating record. (See 75 FR 35128 for a complete discussion of this
proposed option).\3\
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    \3\ While EPA cannot enforce the subtitle D proposed rules, EPA
can take action under section 7003 of RCRA to abate conditions that
``may present an imminent and substantial endangerment to health or
the environment.'' EPA can also use the imminent and substantial
endangerment authorities under the CERCLA, or under other federal
authorities to address those circumstances where a unit(s) may pose
a threat.
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    The Agency also described other alternatives considered. For
example, one subtitle D option, called ``D-prime'' was structured so
that all existing CCR surface impoundments could continue to receive
CCR after the effective date of the rule for the remainder of the
unit's useful life, irrespective of their liner type, provided the
other provisions of the subtitle D option were met (e.g., groundwater
monitoring). (See 75 FR 35128 for a complete discussion of this and
other possible regulatory alternatives on which the Agency solicited
comment.)
    Under both the subtitle C and subtitle D alternatives, EPA proposed
establishing dam safety requirements to address the structural
integrity of surface impoundments. EPA also proposed not to change the
May 2000 Regulatory Determination for beneficially used CCR, which are
currently exempt from the hazardous waste regulations under section
3001(b)(3)(A) of RCRA. EPA also did not propose to address the
placement of CCR in mines, or non-minefill uses of CCR at coal mine
sites.
    In addition to proposing these two regulatory options for the
management of CCR, EPA identified many issues on which it solicited
comment, information, and data. Certain solicitations were very
general, such as comments on alternative options for regulating CCR,
while other requests for comment were very specific in nature, for
example, whether clay liners designed to meet a specified hydraulic
conductivity might perform differently in practices than modeled in the
risk assessment. (The Agency requested comment on issues throughout the
preamble; however specific issues for which EPA solicited comment can
be found at 75 FR 35221-34224.)

B. Comments Received on the Proposed Rule

    The Agency received over 450,000 comments on the proposed rule. The
majority of the commenters focused on which regulatory path the Agency
should pursue for regulating CCR, i.e., RCRA's subtitle C or subtitle
D. A number of commenters, however, argued that no additional
regulation was necessary and that the states were adequately regulating
the management of CCR. Generally, environmental groups and individual
citizens favored a subtitle C rule arguing that state programs have
failed and damage cases are growing in number. State organizations,
individual states, and industry groups (electric utilities, recycling
firms, trade associations), largely favored a subtitle D rule with a
permitting program.
    One area that received extensive comment was the re-evaluation of
the eight Bevill study factors.\4\ Numerous commenters provided
detailed analysis related to the study factors and provided their own
interpretations of the data (e.g., state programs and damage cases).
Other areas that received significant comment included beneficial use
and the risk assessment.
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    \4\ In considering whether to retain or to reverse the August
1993 and May 2000 Regulatory Determinations regarding the Bevill
exemption of CCR destined for disposal, the Agency re-examined the
RCRA section 8002(n) study factors. These eight study factors are:
(1) Source and volumes of CCR generated per year; (2) present
disposal and utilization practices (which includes evaluation of
existing state regulatory oversight and beneficial use); (3)
potential danger, if any, to human health and the environment from
the disposal and reuse of CCR; (4) documented cases in which danger
to human health or the environment from surface runoff or leachate
has been proved; (5) alternatives to current disposal methods; (6)
the cost of such alternative disposal methods; (7) the impact of the
alternative disposal methods on the use of coal and other natural
resources; and (8) the current and potential utilization of CCR (see
75 FR 35128).
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    Discussion of the specific comments germane to this rulemaking are
provided in the relevant sections of this document.

C. Other Actions During Which Comment Was Taken

1. Public Hearings
    EPA conducted eight public hearings during the months of August,
September, and October in 2010. There were over 1300 individual
speakers at the eight public hearings that commented on the proposed
rule. Testimony at the public hearings focused generally on whether EPA

should adopt a subtitle C or subtitle D approach for regulating CCR.
Many commenters were also concerned with fugitive dust emissions and
the affect these emissions had on their health and overall well-being.
Other commenters were concerned that adopting a subtitle C rule for CCR
would negatively affect the beneficial use of the material. In addition
to their testimonies that were entered into the rulemaking record, over
1200 additional documents were submitted in hard copy and entered into
the docket (see EPA-HQ-RCRA-2009-0640).
2. Notices of Data Availability
    Subsequent to the proposed rule, the Agency published several
Notices of Data Availability (NODAs), the first on October 21, 2010,
(75 FR 64974); the second on October 12, 2011 (76 FR 63252) and the
third on August 2, 2013 (78 FR 46940). Specifically:
     The first NODA invited comment on the responses EPA
received on Information Collection Requests that were sent to electric
utilities on their CCR surface impoundments, as well as reports and
materials related to the site assessments EPA had conducted on a subset
of these impoundments.
     The second NODA invited comment on a number of topics,
including (1) chemical constituent data from coal combustion residuals;
(2) facility and waste management unit data; (3) information on
additional alleged damage cases; (4) the adequacy of state programs;
and (5) beneficial use.
     The third NODA invited comment on (1) supplemental data
for the risk assessment; (2) supplemental data for the RIA; (3)
information regarding large-scale fill; and (4) data on the CCR
Assessment Program. EPA also sought comment on two technical issues
associated with the requirements for CCR management units: closure
requirements and regulation of overfills (i.e., CCR management units
built directly over pre-existing CCR landfills or CCR surface
impoundments).
    Specific comments received on each of the three NODAs are discussed
in the relevant sections of this rule.
3. Effluent Limitations Guidelines and Standards for the Steam Electric
Power Generating Point Source Category Proposed Rule
    On June 7, 2013 (78 FR 34432), EPA proposed a regulation that would
strengthen the controls on discharges from certain steam electric power
plants by revising the technology-based effluent limitation guidelines
(ELG) and standards for the steam electric power generating point
source category. As part of this proposal, EPA discussed its current
thinking on how a final RCRA CCR rule might be aligned and structured
to account for any final requirements adopted under the ELG for the
Steam Electric Power Generating point source category. Two primary
means of integrating the two rules were discussed: (1) Coordinating the
design of any final substantive CCR regulatory requirements and (2)
coordinating the timing and implementation of the rules to allow
facilities to coordinate their compliance planning and implementation
and to protect electricity reliability for consumers. EPA stated that
consistent with RCRA section 1006(b), effective coordination of any
final RCRA requirements with the ELG requirements would be sought in
order to minimize the overall complexity of the two regulatory
structures, and facilitate implementation of engineering, financial,
and permitting activities. EPA solicited comments on how any final CCR
final rule might be aligned and structured to account for any final
requirements adopted under the ELG for the Steam Electric Power
Generation point source category.

D. EPA's CCR Assessment Program

    In March 2009, the Agency's CCR Assessment Program (herein referred
to as the Assessment Program) was initiated. This effort was in
response to the December 22, 2008 dike failure of a coal ash
impoundment at the Tennessee Valley Authority (TVA) Kingston Fossil
Plant in Harriman, Tennessee where over one billion gallons of coal ash
slurry were released, affecting more than 300 acres, including
residences and infrastructure. The TVA Kingston impoundment failure
ignited a nation-wide concern over the safety of coal ash impoundments;
and EPA was tasked with determining whether the potential existed for
similar impoundment failures at other coal-fired power plants. In
response, EPA developed the Assessment Program to evaluate the
structural stability and safety of all coal ash impoundments throughout
the country.\5\ As of September 2014, 559 impoundments had been
assessed at over 230 coal-fired power plants.
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    \5\ The focus of the Assessment Program was to assess the
structural integrity of CCR impoundments meeting specified criteria.
The Agency did not include, as part of its evaluation, the
assessment of other conditions/characteristics of the impoundment
that may present potential risks to human health or the environment,
i.e., groundwater contamination due to an insufficient liner design.
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    The Assessment Program began as a separate effort from the
development of this final rule.\6\ However, the information and
experience developed in carrying out the site assessments during the
Assessment Program is directly relevant to many of the issues addressed
in this rulemaking, and provide further technical support for many of
the technical criteria. Consequently, many of the final technical
criteria were developed in direct response to findings from the site
assessments. For example, several of the technical criteria contained
in the proposed rule were modified to account for the widely accepted
engineering methodologies and practices used in conducting the site
assessments, as well as current facility practices documented during
the assessments. In a few instances, the criteria were supplemented to
better align the technical requirements with the Assessment Program.
Included among the final criteria that directly rely on the Assessment
Program are the provisions relating to structural integrity assessments
to address factors of safety, periodic reassessments, hazard potential
classifications, and the hydrologic and hydraulic capacity of CCR
surface impoundments. These requirements are further discussed in Unit
VI of this preamble.
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    \6\ EPA issued two Notices of Data Availability (75 FR 35128
(October 21, 2010) and 78 FR 46940 (August 2, 2013)) specifically
soliciting comment on the information generated by the Assessment
Program and the materials posted on our Web site.
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    The Assessment Program focused on impoundments meeting four general
criteria that were designed to identify the units most likely to
present the same risks as the collapsed TVA impoundment: (1) Above
ground or diked; (2) of sufficient height to be susceptible to
structural failure (i.e., six feet); (3) receiving CCR; and (4) located
at operating coal-fired power plants selling power to the electric
grid. Also included in the assessments were a number of inactive
impoundments, i.e., impoundments not receiving CCR but still containing
CCR and/or liquid. The Agency included these inactive units in the
assessment reasoning that these units would be as susceptible to
structural failure as units currently receiving CCR, given that they
still contained CCR and maintained an ability to impound liquid (i.e.,
the unit had not been breached). The Assessment Program did not
evaluate, however, incised (not having above ground berms or dikes)
impoundments or landfills (not containing liquid slurried CCR wastes).
EPA chose not to assess these units because they did not share the
characteristics of

impoundments likely to raise concern for catastrophic releases, and
because no known catastrophic structural failures were associated with
these types of units.
    Prior to initiating the assessments, EPA consulted with two key dam
safety organizations, the Association of State Dam Safety Officials
(ASDSO) and the Mine Safety and Health Administration (MSHA) to better
understand how these federal and state dam inspection programs
operated, including how earthen dams and impoundments were assessed.\7\
These groups provided the Agency with critical insight and information
for inspecting and evaluating CCR impoundments. The Agency also
reviewed various technical documents relating to dam safety and
conducting impoundment inspections, many of which were recommended by
these organizations. They were: (1) U.S. Army Corp of Engineers (USACE)
2008 National Inventory of Dams (NIDS); (2) Federal Emergency
Management Agency's (FEMA) Federal Guidelines for Dam Safety--Hazard
Potential Classification System for Dams (April 2004); (3) FEMA's Risk
Prioritization Tool for Dams User Manual (March 2008); (4) MSHA's
Handbook (PH07-01); (5) MSHA's Coal Mine Impoundment Inspection and
Plan Review Handbook (October 2007); and (6) MSHA's Engineering and
Design Manual: Coal Refuse Disposal Facility (May 2009); (7) ASDSO's
``Summary of State Dam Safety Laws and Regulations,'' (2000); (8)
ASDSO's ``Owner Responsible Periodic Inspection Guidance,'' (2005); (9)
``Guidelines for Inspections of Existing Dams.'' New Jersey Department
of Environmental Protection--Dam Safety (January 2008).
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    \7\ ASDSO identified for EPA key documents to review including
Federal Energy Regulatory Commission (FERC) and MSHA guidance.
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    In developing the criteria that were used to conduct the
assessments, a standard rating system was developed to classify the
units' suitability for continued safe and reliable operation. EPA
modeled its impoundment condition rating criteria on those developed by
the State of New Jersey (see reference above).
1. Conducting the Site Assessments
    In order to prioritize the assessments, a preliminary hazard
potential classification ranking was identified for each impoundment,
based on criteria developed by the FEMA and found generally in USACE's
NID. EPA elected to evaluate first those impoundments with a high
hazard potential classification, which signifies that a failure or mis-
operation of the unit would probably result in the loss of human life.
    Upon initiation of the Assessment Program, every owner or operator
of a CCR impoundment was contacted by the Agency and supplied with
information on the objectives of the assessment and how the assessments
were to be conducted. Assessments were conducted in rounds, consisting
of groups of 12-26 facilities per round.\8\ Prior to each site
assessment, to ensure uniformity throughout the study, a statement of
work and an impoundment field checklist was developed and adhered to
during the assessment.
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    \8\ The results of this effort are either presented on a
facility by facility basis or are summarized by round. All of these
data have been posted on the Agency Web site.
---------------------------------------------------------------------------

    To ensure objectivity, EPA contracted with professional engineers
(PEs) in the state where the impoundment was located who were experts
in the area of dam safety to perform the site assessments. Each
individual assessment was performed by PEs qualified in the areas of
geotechnical engineering, hydrology and hydraulics, and overall dam
safety. Upon evaluation of a robust set of technical documents
addressing dam safety and inspections as well as comprehensive
discussions with key dam safety organizations, the Assessment Program
developed a comprehensive set of factors that were to be used to
evaluate the overall safety of CCR surface impoundments, which
concluded that, among other important factors, the static and seismic
factors of safety, hydrologic and hydraulic capacity, liquefaction
potential analysis and a post-liquefaction stability analysis if the
soils of the embankment were identified to be susceptible to
liquefaction, and operation and maintenance protocols, e.g.
instrumentation monitoring, inspection program, emergency response
protocols were critical parameters for assessing the overall safety of
CCR surface impoundments.
    The individual evaluations or assessments were conducted at each
impoundment at each facility using standard, accepted engineering
practices, including a visual assessment of the CCR surface
impoundment, interviews with site personnel, a review of the history of
the CCR surface impoundment, and a review of engineering documentation
related to the design, construction, operation, and maintenance of the
impoundments, including available technical analyses. At each site
visit, additional documentation was collected and reviewed as
available, including descriptions, along with supporting information,
of: (1) The impoundment, including location, size, age, design and/or
alterations to the design, and the amount of residuals currently in the
unit; (2) known, measured settlement of the impoundment embankment; (3)
known, measured movement of the impoundment embankment; (4) observed
erosion of the impoundment embankment; (5) seepage; (6) leakage; (7);
observed cracking of the impoundment embankment; (8) deterioration,
such as scarps, boils, or sloughs, of the -- embankment; (9);
seismicity; (10) internal stresses; (11) functioning of foundation
drains and relief wells; (12) stability of critical slopes adjacent to
the units; and (13) regional and site geological conditions. If
available, state and federal inspections reports were also reviewed.\9\
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    \9\ It is important to note that during the assessment, no
physical drilling, coring or sampling was conducted, while on site;
however, studies were reviewed that often included such information.
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    In addition, for each assessment, the following factors were
identified, to the extent feasible, for evaluation: (1) The presence
and adequacy of spillways; (2) hydrologic and hydraulic capacity of the
unit; (3) overall structural adequacy and stability of structures under
all credible loading conditions through a review of static, seismic,
and liquefaction analyses with determined factors of safety; (4) soil,
groundwater, surface water, geology, and geohydrology characteristics
associated with the unit, including hydrological data accumulated since
the impoundment was constructed or last inspected; (5) a history of the
performance of the management unit through analysis of data from
monitoring instruments, interviews with facility personnel, and review
of available operating records; (6) quality and adequacy of
maintenance, surveillance, and methods of unit operations for the
protection of public safety; (7) location of schools, hospitals, or
other critical infrastructures within five miles down gradient of the
impoundment; and (8) whether the impoundment is located within
federally designated flood plains. Finally, each impoundment and any
associated spillways were evaluated to determine whether the
impoundment and the spillways could withstand the loading or
overtopping from appropriate inflow design flood events.
    Each CCR surface impoundment was classified with a hazard potential
classification following the New Jersey Department of Environmental
Protection

Bureau of Dam Safety and Flood Control's hazard potential ranking. Each
impoundment was classified with a hazard potential classification of
either; ``high,'' ``significant,'' ``low,'' or ``less-than-low.'' The
hazard potential classification was a qualitative assessment of the
potential adverse incremental consequences of a dam failure.
    At the conclusion of each assessment, a report was generated and
the impoundment was given a condition rating of either; satisfactory,
fair, poor, or unsatisfactory. The condition ratings were based on the
availability of information on the unit and evaluation of the
previously mentioned factors, including the static, seismic, and
liquefaction factors of safety. No impoundments received an
``unsatisfactory'' rating. Numerous impoundments were, however, rated
as ``poor,'' often for lack of appropriate technical documentation in
the aforementioned areas. ``Poor'' or ``fair'' ratings were also an
indication that additional measures were needed to improve the
stability of the unit. Of 559 impoundments assessed, 241 received a
condition rating of ``satisfactory,'' 166 received a condition rating
of ``fair,'' and 152 received a ``poor'' condition rating.
    It is important to note that the condition rating did not
necessarily imply that the unit had inadequate structural integrity. On
the contrary, in many instances a structurally sound impoundment may
have been given a condition rating or ``fair'' or ``poor'' based on
other factors such as a lack of documented information on the unit or
insufficient operations and maintenance protocols. For example, an
impoundment could be rated as ``poor'' if it lacked the appropriate
technical documentation and analyses regarding structural or hydrologic
and hydraulic analyses. EPA rated numerous units as ``poor'' based
primarily on unavailable technical analyses.
    Once the assessment was performed, a draft report was prepared.
Draft reports were reviewed by the appropriate state agency, the
utility, and by EPA.\10\ Once comments were received and incorporated,
a final report was issued along with recommendations for additional
actions to be taken by the facility (if needed). Facilities then
developed action plans and schedules to implement the recommendations.
EPA also informed facility owners and operators that in addition to
implementing their action plans, they need to adopt an ongoing, routine
program to assess each surface impoundment and to take necessary
corrective measures to ensure the units' continued structural
integrity.
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    \10\ As noted many times in this document, states play a
critical role in implementing and overseeing these units. To assist
states in this effort, EPA has, in the majority of cases directly
provided the states with all of the information from our
assessments. The Assessment Program reports may be accessed at:
http://www.epa.gov/wastes/nonhaz/industrial/special/fossil/surveys2/index.htm.
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2. Assessment Program Findings
    Upon completion of the Assessment Program, a review was undertaken
to ascertain the key findings or lessons learned from the effort. These
key findings included: (1) The majority of CCR surface impoundments are
currently inspected on a periodic basis; (2) most utilities were
readily able to supplement outdated or missing information with new or
updated evaluations of their impoundments after the on-site portion of
EPA's assessment was conducted; (3) in response to the assessment
report recommendations, facilities typically willingly conducted
remedial actions; (4) interaction with the states and the utilities
assured accuracy in the final assessment reports; (5) placing site
assessment materials on an internet site assured that the public,
states, and utilities had full access to information about the design
and operation of CCR impoundments and did not present either homeland
security or other confidentiality concerns; (6) static, seismic, and
liquefaction analyses did not pose a significant technical or cost
burden on facilities since many already routinely conducted these types
of evaluations; (7) state regulatory bodies viewed the assessments as a
means to further support existing assessment programs; and (8) the use
of PEs to certify all final reports ensured that the assessments
reflected the PE's best judgments.
3. Assessment Program's Support for the Structural Integrity
Requirements of the Rule
    As noted, the findings from EPA's Assessment Program provide
technical and factual support for many of the final requirements for
structural stability in this rule. A more detailed discussion of
several of the most significant of these is presented below. Additional
discussion of the relevance of these findings is included throughout
Unit VI of this document.

a. Periodic Inspections/Assessments

    Consistent with the findings from the assessments and with EPA's
recommendations to facilities as part of the Assessment Program, this
rule requires that all CCR surface impoundments be inspected at
intervals not exceeding seven days for any appearances of actual or
potential structural weakness and other conditions that are disrupting
or have the potential to disrupt the operation or safety of the CCR
surface impoundment. Monitoring of instrumentation is also required to
be conducted at intervals not exceeding 30 days. The Assessment Program
found that virtually all utility companies conduct some sort of
periodic inspection or monitoring at CCR surface impoundments, although
practices varied among facilities and between states. The Assessment
Program also found that while many facilities were conducting regularly
scheduled inspections, some did not adequately document the results of
these inspections.
    In the final rule, CCR surface impoundments exceeding a specified
size threshold, i.e., height of five feet or more and capacity of 20
acre-feet or more or a height of 20 feet or more, are required to
perform annual inspections as well as two assessments of structural
stability quinquennially, (i.e., every five years) that include a
structural stability assessment of specified parameters and a factor of
safety assessment. Annual inspections are broader in scope than weekly
inspections and are conducted to ensure that the design, construction,
operation and maintenance of the CCR unit is consistent with recognized
and generally accepted good engineering standards. Annual inspections
must include a review of available information regarding the status and
condition of the unit and a visual inspection to identify signs of
distress or malfunction of the unit and appurtenant structures. The
annual inspections must be conducted by a qualified professional
engineer.
    The Assessment Program also reviewed how detailed structural
stability reviews and inspections were recommended to be conducted by
FEMA, MSHA, and the USACE guidelines and found that such inspections
were recommended to take place every three to five years. Review of
state dam safety programs demonstrated that similar detailed
inspections were also conducted on a three-to-five year cycle.
Therefore, in the final rule, EPA is requiring that structural
integrity assessments, including the calculation of factors of safety
under various loading conditions, be conducted within 18 months of
publication of the rule, and be repeated every five years. The five
year review timeframe is based on documentation showing that the
factual bases for such reviews are only sound for that time

period, and is consistent with federal dam safety guidance,
specifically FEMA. FEMA recommends in Federal Guidelines for Dam Safety
that dams be formally assessed at a frequency not to exceed five years
by a qualified professional engineer. EPA has adopted this timeframe to
maintain consistency with FEMA guidance. The inspection and assessment
requirements in this rule will ensure that there are consistent and
uniform inspection and assessment practices across states and
facilities and will ensure that problems related to their stability
will be promptly identified and remediated as necessary.

b. Static, Seismic, and Liquefaction Factors of Safety

    (1) Static Factors of Safety.
    Factor of safety (FOS) means the ratio of the forces tending to
resist the failure of a structure, as compared to the forces tending to
cause such failure as determined by accepted engineering practice. This
analysis is used to determine whether a CCR surface impoundment's dikes
are engineered to withstand the specific loading conditions that can be
reasonably anticipated to occur during the lifetime of the unit without
failure of the dike, if accepted good engineering practices are
employed. Static factors of safety refer to the factors of safety (FOS)
under static loading conditions that can reasonably be anticipated to
occur during the lifetime of the unit. Static loading conditions are
unique from other loading conditions (e.g., seismic, liquefaction) in
that static loading conditions are those which are in equilibrium,
meaning the load is at rest or is applied with constant velocity.
    EPA reviewed a series of USACE guidance documents addressing how to
determine static FOS. These documents included, but were not limited
to, Engineer Manual EM 1110-2-1902 ``Slope Stability'' (October 2003),
and EM 1110-2-1902 ``Stability of Earth and Rock-Fill Dams.'' The
Agency also assessed the recommendations on how to conduct static
analysis contained in the Engineering and Design Manual for Coal Refuse
Disposal Facilities, originally published by the Mining Enforcement and
Safety Administration (MESA) in 1975 and updated for MSHA in May 2009,
and in particular Chapter 6, ``Geotechnical Exploration, Material
Testing, Engineering Analysis and Design.'' Based on recommendations
from ASDSO, among others, the Agency adopted the USACE guidance to
determine static FOS, both in the Assessment Program and in this
rulemaking, as these manuals are recognized throughout industry as the
standard routinely used in field assessment of structural integrity.
    In EPA's Assessment Program all CCR units were assessed to
determine their static FOS. Each assessment classified a CCR unit as
having sufficient structural stability under static loading conditions
if analysis of critical sections of embankments demonstrated FOS that
met or exceeded the values defined by USACE for static specific loading
conditions. EPA found that most CCR surface impoundments exhibited
sufficient calculated factors of safety under static loading
conditions. EPA also found that in those CCR units which insufficient
factors of safety against failure due to static loading were
calculated, the owner or operator was able to implement actions which
increased the factors of safety under static loading conditions to
acceptable levels. Oftentimes, these implemented actions were of a
simple nature, such as installing riprap (rock armoring the slopes) or
buttressing the slopes.
    Similarly, this rule adopts the static FOS from USACE Engineer
Manual EM 1110-2-1902 ``Slope Stability,'' with the exception of the
rapid drawdown loading condition,\11\ which was determined not to be
relevant to CCR surface impoundments. EPA found the factors of safety
identified by EM 1110-2-1902, specifically the Maximum Storage pool,
Maximum Surcharge pool, and End-Of-Construction loading conditions,
provided consistent, achievable levels of safety in CCR surface
impoundment dikes, comprehensively assessed static stability, and
provided sufficient consideration of compounding stresses on dikes
(e.g., factors of safety values greater than 1.00 to account for
unanticipated loadings acting in conjunction or misidentified strength
of materials).
---------------------------------------------------------------------------

    \11\ Rapid (or sudden) drawdown is a condition in earthen dikes
that may develop when the embankment becomes saturated through
seepage during a high pool elevation in the reservoir. Rapid
drawdown becomes a threat to the dike when the reservoir pool is
drawn down or lowered at a rate significantly higher than the excess
poor water pressure within the dike can dissipate. Typically, rapid
drawdown scenarios are considered for dikes with reservoirs used for
water supply and management or agricultural supply. In these
scenarios, a high pool elevation is maintained in the reservoir in
storage months. Subsequently, the water supply is drawn on in months
where there is a demand for the reservoirs contents. This drawing
down of the pool can present issues for the structural integrity of
the unit. However, the management of CCR surface impoundments
differs from that of conventional water supply reservoirs. CCR
surface impoundments are never used for water supply, and the only
instance in which EPA determined through its Assessment Program that
rapid drawdown loading conditions would be relevant to CCR surface
impoundments was in the event that the CCR surface impoundment had
already released the contents of the impoundment through a breach of
the dike or emergency discharge. Since the threat of release of CCR
and the reservoir has already been realized, any failure due to
rapid drawdown of the embankment is no longer critical to the
overall containment of the now-released contents of the CCR unit.
---------------------------------------------------------------------------

    (2) Seismic Factor of Safety.
    Seismic FOS means the FOS determined using analysis under
earthquake conditions for a seismic loading event, based on the U.S.
Geological Survey (USGS) seismic hazard maps for seismic events with a
specified return period for the location where the CCR surface
impoundment is located. The seismic FOS analysis is used to determine
whether a dam would remain stable during an earthquake or other seismic
event. The Agency relied on guidance from USACE and MSHA to evaluate
the appropriate methods to determine if a dam would remain stable
during a seismic event. This includes the USACE guidance Engineer
Circular 1110-2-6061: Safety of Dams--Policy and Procedures 2204,
Engineer Circular 1110-2-6000: Selection of Design Earthquakes and
Associated Ground Motions 2008, and Engineer Circular 1110-2-6001:
Dynamic Stability of Embankment Dams 2004). EPA also reviewed MSHA's
2009 Engineering and Design Manual for Coal Refuse Disposal Facilities,
in particular Chapter 7, ``Seismic Design: Stability and Deformation
Analyses.'' These documents are viewed by ASDSO, FEMA and MSHA as
generally accepted guidance on how to conduct seismic stability
analyses.
    As noted earlier, in performing the assessments, EPA directed its
engineering contractors to assess seismic stability of CCR impoundments
during and following a seismic event with a 2% probability of
exceedance in 50 years (i.e. probable earthquake within approximately
2,500 years) and a horizontal spectral response acceleration for 1.0-
second period (5% of Critical Damping). EPA selected this return period
for determining the maximum design earthquake (MDE) by first
considering the operating life anticipated for CCR surface
impoundments. EPA has identified the operating life of CCR surface
impoundments to range between 40-80 years. EPA then consulted the
United States Geological Survey (USGS) and ASDSO to determine a
conservative probability that should be used in the assessments.\12\ To
reduce the likelihood of a CCR unit failing during a seismic

event, the Agency assessed various return periods and chose a
conservative 2500 year return period. The use of this ``return'' period
was chosen because it is conservative, reflects the fact that many CCR
impoundments are located in active seismic zones, and the use of a
conservative ``return'' period ensures that if a unit meets the seismic
FOS it is unlikely to fail under most seismic events. By evaluating
seismic stability under a conservative return period and requiring the
unit to maintain structural stability under that design seismic event,
the likelihood of a seismic event occurring at the location of the CCR
surface impoundment in which the strength of the unit is exceeded and
the unit fails is considerably reduced. Additionally, the unit can
reasonably be anticipated to withstand seismic events of a more
frequent return period (i.e., smaller magnitude).
---------------------------------------------------------------------------

    \12\ Wieland, M., ``Seismic Design and Performance Criteria for
Large Storage Dams'', Proc. 15th World Conf. on Earthquake
Engineering, Lisbon, Portugal, Sep. 24-28, 2012.
---------------------------------------------------------------------------

    The Agency assessed CCR impoundments and classified them as having
seismic stability if modeling results of critical failure surfaces were
calculated to have a FOS greater than 1.0 under the specified seismic
loading condition. The Assessment Program found that most CCR
impoundments did meet the required seismic FOS. This rule also adopts
this seismic stability FOS under the 2% probability of exceedance in 50
years event.
    The Assessment Program found that many CCR impoundments had not
undergone static or seismic analyses in sufficient detail that an
independent professional engineer could assert that they were stable.
The assessments gave impoundments a condition rating of ``poor'' if the
utility was unable to provide static and seismic studies of their units
conducted in a fashion which represented acceptable professional
engineering practice. As the Assessment Program advanced, many
utilities independently conducted new or updated static and seismic
analyses of CCR surface impoundments in anticipation of their
facilities being assessed. By the end of the program, virtually all
facilities had conducted or were in the process of conducting static
and seismic analyses. While some utilities noted concern over the costs
of conducting additional static or seismic stability studies, none
found that completing these studies presented any significant
engineering challenges.
(3) Liquefaction Factors of Safety
    Liquefaction FOS means the factor of safety determined using
analysis under liquefaction conditions. Liquefaction is a phenomenon
which typically occurs in loose, saturated or partially-saturated soils
in which the effective stress of the soils reduces to zero,
corresponding to a total loss of shear strength of the soil. The most
common occurrence of liquefaction is in loose soils, typically sands.
The liquefaction FOS determination in the final rule is used to
determine if a CCR unit would remain stable if the soils of the
embankment of the CCR unit were to experience liquefaction. EPA relied
primarily on one source to evaluate the appropriate methods to
determine if a dam would remain stable under liquefaction conditions.
This source was ``Soil Liquefaction during Earthquakes,'' Idriss and
Boulanger, Earthquake Engineering Research Institute, 2008.\13\ EPA
also reviewed several technical resources regarding soil liquefaction,
including ``Ground Motions and Soil Liquefaction During Earthquakes,''
Seed and Idriss, 1982,\14\ ``Liquefaction Resistance of Soils: Summary
report from the 1996 and 1998 NCEER/NSF Workshops on Evaluation of
Liquefaction Resistance of Soils,'' Youd and Idriss, 2001,\15\ and
Seismic Design Guidance for Municipal Solid Waste Landfill Facilities,
US EPA, Office of Research and Development, 1995.\16\ These documents
are viewed as generally accepted guidance on how to conduct
liquefaction potential analyses and residual strength analyses under
post-liquefaction conditions.
---------------------------------------------------------------------------

    \13\ https://www.eeri.org/products-page/monographs/soil-liquefaction-during-earthquakes-3/.
    \14\ Seed, H. B., and Idriss, I. M., 1982, ``Ground Motions and
Soil Liquefaction During Earthquakes,'' Monograph No. 5, Earthquake
Engineering Research Institute, Berkeley, California, pp. 134.
    \15\ Youd, T. L., Idriss, I. M., 2001, ``Liquefaction Resistance
of Soils: Summary report from the 1996 and 1998 NCEER/NSF Workshops
on Evaluation of Liquefaction Resistance of Soils.'' Journal of
Geotechnical and Geoenvironmental Engineering, ASCE.
    \16\ United States EPA, Office of Research and Development,
1995, EPA/600/R-95/051, RCRA Subtitle D (258) Seismic Design
Guidance for Municipal Solid Waste Landfill Facilities. Available as
of the Writing of this policy at www.epa.gov/clhtml/pubtitle.html on
the U.S. EPA Web site.
---------------------------------------------------------------------------

    As noted earlier, in performing the assessments, EPA assessed the
liquefaction potential of soils that compose the embankments of the CCR
unit to determine if the soils present in the embankment were of the
soil classification and configuration that was susceptible to
liquefaction. This determination was based on evidence available
through interviews with facility personnel, construction documentation,
or representative soil sampling, such as information provided by
corings and borings. Identical to the requirements for seismic factor
of safety calculation, EPA selected a return period for a seismic event
for analysis of liquefaction potential, under a seismic loading which
may induce liquefaction in embankments, of a 2% probability of
exceedance in 50 years. The discussion of the selection of this return
period can be found in the ``Seismic Factor of Safety'' section above.
    The Agency assessed CCR impoundments and classified them as having
stability under liquefaction conditions if representative soil
sampling, anecdotal evidence from interviews with facility personnel,
or construction documentation indicated that there was no
susceptibility to liquefaction of the embankment soils or if modeling
or analysis in critical failure planes in the embankment expected to be
susceptible to liquefaction were calculated to have a FOS greater than
1.00 under post-liquefaction conditions. The Assessment Program found
that most CCR surface impoundments did not contain soils in detrimental
volumes or configurations in the embankment that would indicate
susceptibility to liquefaction. However, the assessment effort found
that in embankments with a presence of soils susceptible to
liquefaction, most CCR surface impoundments did not meet the required
liquefaction FOS.
    The Assessment Program found that many CCR surface impoundments had
not undergone liquefaction potential analyses or post-liquefaction
residual strength analyses in those instances in which liquefaction
potential was identified (i.e., soils subject to liquefaction were
present). The assessments gave impoundments a condition rating of
``poor'' if there was no information available to characterize the
soils of the embankment, and a condition rating of ``poor'' or ``fair''
if post-liquefaction residual strength analysis of soils previously
identified as being susceptible to liquefaction had not been available,
with the rating dependent on the determined severity of the
liquefaction potential in the embankment. Impoundments with calculated
liquefaction factors of safety which did not meet or exceed 1.00 were
given a condition rating of ``poor.''
    As the Assessment Program advanced, many utilities independently
conducted new or updated liquefaction potential analyses or residual
strength analyses of CCR surface impoundments in anticipation of their
facilities being assessed. By the end of the program, virtually all
facilities had conducted or were in the process of conducting
liquefaction potential analyses or residual strength analyses. While
some utilities noted concern over the costs of

conducting additional liquefaction potential or residual strength
studies, none found that completing these studies presented any
significant engineering challenges.
    Based on its experience in the Assessment Program and subsequent
review of numerous technical resources, EPA determined that a post-
liquefaction residual strength factor of safety in the embankment of
1.00 is not sufficient. Liquefaction potential analysis and post-
liquefaction residual strength analysis involves a larger degree of
uncertainties, e.g., liquefiable stratum configuration, in assumptions
and analysis which must be accounted for with a factor of safety above
1.00. The final rule therefore requires CCR surface impoundments which
are constructed of soils determined to be susceptible to liquefaction
to meet or exceed a liquefaction factor of safety of 1.20. EPA has
determined that 1.20 is an appropriate liquefaction factor of safety
based on several technical guidances and memos, including Federal
Guidelines for Dam Safety: Earthquake Analyses and Design of Dams,
Document 65, FEMA May 2005, which states that ``post-liquefaction
factors of safety are generally required to be a minimum of 1.2 to
1.3.'' 17 18 19 20 21
---------------------------------------------------------------------------

    \17\ US Bureau of Reclamation (USBR), ``Water Operation and
Maintenance Bulletin No. 222,'' Denver, Colorado, December 2007.
    \18\ http://www.oregon.gov/odot/hwy/bridge/docs/bddm/pdfs/psha.pdf.
    \19\ Canadian Dam Association. Canadian Dam Safety Guidelines,
2007, 88 pp.
    \20\ Sonmez, H., 2003. Modification of the liquefaction
potential index and liquefaction susceptibility mapping for a
liquefaction-prone area (Inegol, Turkey), Env. Geology, (44): 862-
871.
    \21\ Seed, R.B., Cetin, O.K., Moss, R.E.S., Kammerer, A.M., Wu,
J., Pestana, J.M., Riemer, M.F., Sancio, R.B., Bray, J.D., Kayen,
R.E., Faris, A., 2003. Recent advances in soil liquefaction
engineering: a unified and consistent framework, 26th annual ASCE
L.A. Geot. Spring Sem., Long Beach, California, April 30, 71 pp.
---------------------------------------------------------------------------

c. Impoundment Height and Relationship to Regulatory Requirements

    During the Assessment Program, the Agency reviewed the stability
issues related to various heights of impoundments. The Assessment
Program concluded that impoundments with heights less than five feet or
those retaining less than 20 acre feet were unlikely to cause
significant environmental or economic loss should they undergo a
catastrophic failure. The Agency's review of MSHA and FEMA guidance
also noted that ``small'' units were unlikely to cause significant
losses should they fail. Based on the Agency's experience and FEMA and
MSHA's guidance, the Agency has concluded that there is a substantial
benefit in having impoundments which exceed a specified size threshold,
i.e., height of five feet or more and capacity of 20 acre-feet or more
or a height of 20 feet or more determine their static, seismic, and
liquefaction FOS on a regular basis. The analyses and experience gained
in conducting the Assessment Program indicates that a catastrophic
failure of a CCR surface impoundment is unlikely to occur so long as
the factors of safety are maintained or exceeded throughout the unit's
operating life. This conclusion is also consistent with relevant
guidance and regulations which do not require such evaluations for
units below a certain size threshold.

d. Hazard Potential Ratings

    Each impoundment assessed in the Assessment Program was given a
Hazard Potential Classification rating of either Less-than-Low, Low,
Significant, and High. Previous classifications were reviewed and
amended as necessary to reflect guidance developed for the Assessment
Program. The hazard potential ratings refer to the potential for loss
of life or damage if there is a dam failure. The ratings do not refer
to the condition or structural stability of the dam. Four hazard
potential classifications were used in assessing the impoundments in
the Assessment Program:
    High Hazard Potential--Dams assigned the high hazard potential
classification are those where failure or mis-operation will probably
cause loss of human life.
    Significant Hazard Potential--Dams assigned the significant hazard
potential classification are those dams where failure or mis-operation
results in no probable loss of human life, but can cause economic loss,
environment damage, disruption of lifeline facilities, or impact other
concerns. Significant hazard potential classification dams are often
located in predominantly rural or agricultural areas, but could be
located in areas with population and significant infrastructure.
    Low Hazard Potential--Dams assigned the low hazard potential
classification are those where failure or mis-operation results in no
probable loss of human life and low economic and/or environmental
losses. Losses are principally limited to the owner's property.
    Less Than Low Hazard Potential--Dams which do not pose high,
significant, or low hazard potential.
    There is a substantial benefit in having owners or operators of all
CCR impoundments determine the hazard potential classification of their
units. The Assessment Program found that many CCR surface impoundments
had not been given a hazard potential classification and consequently,
their potential threat to human health and the environment if a failure
were to occur was not clearly identified, nor had response plans been
developed to respond to any catastrophic failure. Moreover, these
classifications should be updated over time, particularly to account
for changes such as population growth, construction of key
infrastructure, or changes to the impoundment's size or operation. The
Assessment Program also found that some states do not classify CCR
impoundments as ``dams'' and therefore those units may not be required
to determine their hazard potential classification or otherwise
evaluate the potential effects of a catastrophic failure. Consistent
with the guidance from ASDSO, FEMA, and the state of New Jersey, this
rule requires that all diked CCR impoundments determine their hazard
potential classification according to the definitions set out in this
regulation. For those units with a hazard potential classification of
significant or high, the owner or operator of such impoundments is also
required to develop an Emergency Action Plan to address the higher
potential impacts of a potential failure.

e. Condition Ratings

    While the rule does require facilities to evaluate the same
engineering factors that went into developing these ratings, the rule
does not require that each impoundment be given a condition rating.
After evaluation of the use of these ratings, the Agency determined
that the rating may have relied too heavily on subjective factors. For
that reason, this rule requires that the qualified professional
engineer certify, based on quantitative determinations, that an
impoundment meets the requirements for FOS and hydraulic and hydrologic
capacity. This approach is less subjective and allows the professional
engineer to make quantifiable certifications.

IV. Bevill Regulatory Determination Relating to CCR From Electric
Utilities and Independent Power Producers

    As discussed in the preceding sections, in the proposed rule EPA
reopened its August 1993 and May 2000 Regulatory Determinations
regarding CCR generated at electric utilities and independent power
producers, to re-evaluate whether regulation of CCR under RCRA subtitle
C is necessary in light of subsequent information. EPA explained that
this was based on several

relatively recent developments, such as a newly completed quantitative
risk assessment that concluded that the disposal of CCR in unlined
waste management units posed substantial risks, with upper end risk
estimates ranging from 10-2-10-4. Citing to the
recent structural failures of surface impoundments, the proposed rule
also noted that these wastes have caused greater damage to human health
and the environment than EPA originally estimated. Finally, EPA
explained that recently collected information regarding the existing
state regulatory programs had called into question whether those
programs, in the absence of national minimum standards specific to
these wastes, had sufficiently improved to address the gaps originally
identified in the May 2000 Regulatory Determination. EPA ultimately
concluded that federal regulation of this material was necessary, but
did not reach any conclusion as to whether regulation under subtitle D
would be sufficient or whether regulation under subtitle C would be
necessary to adequately address the risks.
    Of the over 450,000 comments received on the proposed rule, the
vast majority focused on whether the Bevill exemption should be
retained, and the corresponding question of whether CCR regulations
should be established under RCRA subtitle C or subtitle D. In terms of
the sheer numbers, the majority of commenters supported a decision to
revoke the Bevill exemption and to regulate CCR under a subtitle C
rule. These commenters, largely individual members of the public and
environmental groups, generally argued that the Bevill exemption should
be revoked because state programs have failed to adequately regulate
the disposal of CCR and because the risks associated with the
management of these wastes are significant. In support of both points,
these commenters pointed to the fact that the number of damage cases
that have been discovered has increased substantially since the
original 2000 Regulatory Determination, and have continued to grow
since publication of the proposed rule in 2010.
    By contrast, state organizations, individual states, and industry
groups (electric utilities, recycling firms, trade associations),
largely favored a subtitle D rule. Overall, these commenters raised
concern about the costs of the subtitle C regime, arguing that the
subtitle C requirements were more stringent than necessary to address
the risks from CCR disposal. Commenters also raised concern that
regulation of these wastes under subtitle C would negatively affect the
beneficial use of these materials, arguing that the stigma associated
with regulating the disposal of CCR as a hazardous waste would
``cripple'' the current beneficial reuse market. Many of these
commenters also argued that EPA lacks the legal authority to regulate
these wastes under subtitle C on a variety of grounds, including claims
that EPA entirely lacks the authority to revisit its Bevill Regulatory
Determination, and that EPA had failed to comply with statutory
procedures in doing so.

A. Deferral of a Final Decision on the Bevill Regulatory Determination
for CCR Destined for Disposal

    In determining whether the Bevill exemption should be retained for
CCR, EPA must evaluate and weigh eight factors that were enumerated in
section 8002(n) of RCRA. 42 U.S.C. 6921(b)(3)(C). The eight factors
are: (1) The source and volumes of CCR generated per year; (2) present
disposal and utilization practices; (3) potential danger, if any, to
human health or the environment from the disposal and reuse of CCR; (4)
documented cases in which danger to human health or the environment
from surface run-off or leachate has been proved; (5) alternatives to
current disposal methods; (6) the cost of such alternative disposal
methods; (7) the impact of those alternatives on the use of coal and
other natural resources; and (8) the current and potential utilization
of CCR. 42 U.S.C. 6982(n).
    EPA addressed each of these study factors in the 1988 and 1999
Reports to Congress, and in reaching our decisions in the August 1993
and the May 2000 Regulatory Determinations to maintain the Bevill
exemption for CCR. 58 FR 42466 (August 9, 1993); 65 FR 32214 (May 22,
2000). Consequently, in considering whether to reverse these Regulatory
Determinations for CCR destined for disposal, EPA reexamined the RCRA
section 8002(n) study factors against all of the available data, which
included both the data that formed the basis for the May 2000
Regulatory Determination and the most recent data available. (See 75 FR
35150-35156.)
    As discussed at length in the proposed rule, three of these factors
weighed the most heavily in the Agency's decision to reconsider its
previous Regulatory Determinations. (See 75 FR 35133 and 35156-35158.)
The first of these related to the extent of the risks posed by the
current management of these wastes. Since the 2000 Regulatory
Determination, EPA had completed a quantitative risk assessment that
estimated significant risks to human health and the environment. EPA's
2010 CCR risk assessment estimated the cancer risk from arsenic that
leaches into groundwater from CCR managed in units without composite
liners to exceed EPA's typical risk thresholds of 10-4 to
10-6. For example, depending on various assumptions about
disposal practices (e.g., whether CCR is co-disposed with coal refuse),
groundwater interception and arsenic speciation, the 90th percentile
risks from unlined surface impoundments ranged from 2 x 10-3
to 1 x 10-4. The risks from clay lined surface impoundments
ranged from 7 x 10-2 to 4 x 10-5. Similarly,
estimated risks from unlined landfills ranged from 5 x 10-4
to 3 x 10-6, and from 2 x 10-4 to 5 x
10-9 for clay-lined landfills. EPA's risk assessment also
estimated Hazard Quotients (HQs) \22\ above 1 for other metals,
including selenium and lead in unlined and clay-lined units. However, a
number of technical questions were raised regarding this quantitative
risk assessment that called into question the accuracy of these risk
estimates.
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    \22\ For more information on HQs please see Unit X. Risk
Assessment of this preamble.
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    A second and equally significant consideration related to how
effectively state regulatory programs address the risks associated with
the improper management of these wastes. The existing reports on state
regulatory programs had called into question whether the trend in
improving state regulatory regimes that EPA identified in May 2000 had
materialized to the degree anticipated in the Regulatory Determination.
EPA noted concern about the lack of substantial details regarding the
full extent of state regulatory authority over the disposal of these
materials, and the manner in which states have, in practice,
implemented this oversight.
    The final consideration, which is tightly related to the first two,
was the recent information documenting continued instances involving
the contamination of ground or surface water from the management of
these wastes. Since the 2000 Regulatory Determination EPA had gathered
or received information on 67 ``proven or potential'' cases involving
damage to (i.e., contamination of) ground and surface water, and to
human health and the environment from improper management of CCR in
landfills and surface impoundments. These also included cases involving
the structural failure of surface impoundments and the catastrophic
release of CCR.

    For each of these key areas, EPA identified a number of issues on
which the absence of critical information prevented the Agency from
reaching an initial decision on whether to revise the Bevill
Determination. Some of these issues or uncertainties have been resolved
during the development of the final rule, either as a result of
information received from commenters or through additional information
and analyses EPA obtained or developed, which were held out for comment
in subsequent NODAs. See 75 FR 35128 (October 21, 2010) and 78 FR 46940
(August 2, 2013). However, as discussed in more detail below, critical
information necessary to make a final Regulatory Determination is still
lacking in two of these three areas. This information bears directly on
the extent and magnitude of the risks over the course of the next
several years, and the degree to which those risks can be managed
sufficiently under each of the two regulatory structures available to
the Agency. In the absence of this information, EPA is unable to reach
a conclusion on the issue that is central to a Bevill Determination:
Whether the risks presented by management of CCR waste streams can only
be adequately mitigated through regulation under RCRA subtitle C. As a
consequence, EPA is deferring a final Regulatory Determination for
these wastes.\23\
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    \23\ Because EPA is deferring its final Bevill Determination,
EPA has not responded to comments that pertain exclusively to that
issue. However EPA has responded to significant comments that relate
to topics that are otherwise relevant to the final subtitle D
regulation. For example, because EPA is relying on the damage cases
to support certain aspects of the technical requirements, EPA has
responded to comments relating to the accuracy of the facts involved
in the damage cases. EPA has not, however, responded to many
comments on state programs because the Agency has made no final
conclusions on the adequacy of those programs and is not relying on
state programs to support any of the final rule's provisions.
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    Nevertheless, the record is clear that current management of these
wastes can present, and in many cases has presented, significant risks
to human health and the environment. Although EPA cannot reach
conclusions as to the full extent or magnitude of those risks over the
long term, the current level of risk clearly warrants the issuance of
federal standards to ensure consistent management practices and a
national minimum level of safety.
    In the following sections, EPA describes the information that was
obtained over the course of the rulemaking relating to each area of
concern, and the extent to which the new information addressed the
issue.
1. Risks Posed by Current Management of CCR and Potential Danger to
Human Health From the Disposal of CCR
    In the proposed rule, EPA specifically noted that several
uncertainties remained in the Agency's quantitative risk analysis of
the current management of CCR. Chief among these uncertainties was the
evolving character and composition of CCR due to electric utility
upgrades and retrofits of multi-pollutant controls needed to comply
with the emerging Clean Air Act (CAA) requirements, which could present
new or otherwise unforeseen contaminant issues (e.g., addition of
calcium bromide to coal prior to combustion increasing mercury capture;
use of selective catalytic reduction for post-NOX controls
forming hexavalent chromium). As EPA explained, changes to fly ash and
other types of CCR is expected to occur as a result of increased use
and application of advanced air pollution control technologies in coal-
fired power plants. These technologies include flue gas desulfurization
(FGD) systems for SO2 control, selective catalytic reduction
(SCR) systems for NOX control, and activated carbon
injection (ACI) systems for mercury control. These technologies are
being installed or are expected to be installed in response to federal
regulations, state regulations, legal consent decrees, and voluntary
actions taken by industry to adopt more stringent air pollution
controls. Use of these more advanced air pollution control technologies
reduces air emissions of metals and other pollutants in the flue gas of
a coal-fired power plant by capturing and transferring the pollutants
to the fly ash and other air pollution control residues. Previous EPA
studies of whether increased pollutant content would increase the risks
correspondingly were inconclusive. For example, EPA evaluated the
environmental fate of metals that are captured in CCR through use of
enhanced air pollution controls, by characterizing the leaching
behavior of 73 air pollution control residues, using the Leaching
Environmental Assessment Framework (LEAF) methodology. Materials were
tested over the pH conditions and liquid/solid ratios expected during
management via land disposal or beneficial use. Leachate concentrations
for most metals were highly variable over a range of coal type,
facility configurations, and air pollution control residues. In
addition, the data showed significantly different leaching behavior for
similar residue types and facility configurations. Overall, the
variability in leaching of the metals in the CCR was greater than the
variability in totals concentrations by several orders of magnitude,
suggesting that total pollutant content may not be predictive of
leaching behavior, and consequently the risks.\24\
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    \24\ Thorneloe, S, Kosson, D., Sanchez, F., Garrabrants, A.C.,
and Helms, G., Evaluating the Fate of Metals in Air Pollution
Control Residues from Coal-Fired Power Plants, Environ. Sci.
Technol. 2010, 44, 7351-7356.
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    The Agency received no data from commenters that would aid in
resolving this uncertainty. To try to establish some parameters around
the uncertainty, EPA attempted to develop estimates of the extent to
which this issue could meaningfully affect the risks.
    As an initial step, EPA focused on mercury pollution controls, as
mercury levels in these wastes was an issue of particular concern in
the public comments. It has been established that mercury pollution
controls can affect both the mercury content and the general leaching
behavior of ash (US EPA 2006, 2008, 2009). Using the limited data
available, EPA attempted to evaluate the extent to which mercury
controlled wastes could ultimately affect the overall risk associated
with disposal of CCR.
    EPA conducted a sensitivity analysis that filtered the full 2014
risk assessment results for the subset of fly ash samples generated by
facilities that have currently installed ACI systems. The samples were
collected from five different facilities that were either installing or
evaluating an ACI system for increasing mercury capture. At each
facility, samples were collected both before and after the installation
of an ACI system. Ultimately the results were inconclusive, likely
because of the small sample size, and EPA can draw no conclusions about
the exact effects of ACI systems on the risks from CCR disposal.
Nevertheless, the analysis provided some useful information. Capturing
and transferring pollutants from air emission to the fly ash and other
air pollution control residues would normally be expected to increase
the risks associated with disposal of these wastes. EPA's analyses,
however, showed only a marginal difference in risks for ash generated
with or without the use of an ACI system, and in some instances the
risks decreased slightly with the addition of activated carbon. The
significance of these results should not be overstated--the observed
decreases were not consistent and were thought to be an artifact of the
relatively small number of model iterations. It is also important to
remember that these results provide no information about the potential
effects from the installation of

FGD systems for SO2 control, or SCR systems for
NOX control, any of which could also significantly affect
the characteristics of the wastes. But these results also suggest that
EPA should be cautious about assuming that the risks will necessarily
increase as a result of the imposition of additional air pollution
controls.
    Other uncertainties in the risk assessment developed for the
proposal related to the extent to which some sampled data with high
concentrations of constituents used in the risk assessment accurately
reflect coal ash leaching from landfills or surface impoundments. For
example, as explained in the proposed rule, some data reflected pore
water taken in the upper section of a surface impoundment where coal
refuse was placed. There were acid generating conditions and high
concentrations of arsenic, but the data demonstrated that the
underlying coal ash neutralized the acid conditions and greatly reduced
the arsenic which leached from the bottom of the impoundment. EPA also
noted that much of the pore water samples and leachate data were
several years old, and questions had been raised whether these data
accurately reflected current management practices. Finally, EPA noted
that recent research indicated that traditional leach procedures (e.g.,
Toxicity Characteristic Leaching Procedure (TCLP) and Synthetic
Precipitation Leaching Procedure (SPLP)) may underestimate the actual
leach rates of toxic constituents from CCR under different field
conditions.
    First, regarding the question of appropriate pH conditions in CCR
units, and the resulting leachate concentrations in impoundments where
coal refuse was placed, EPA obtained data during the development of
this rule directly relevant to this issue. A survey conducted by the
Electric Power Research Institute (EPRI) in 1995 had shown that 34
percent of unlined landfills and 68 percent of unlined surface
impoundments actively managed CCR with coal refuse. However, more
recent data collected by EPA as part of the Clean Water Act ELG
rulemaking in 2009-2010 indicates that this management practice has
declined significantly to approximately five percent of current units.
    EPA also obtained sufficient data to resolve concerns about the
accuracy of the concentrations in pore water and leachate used in the
risk assessment. EPA received a substantial amount of data on CCR
chemical constituents from commenters, which included total
concentrations, pore water, and leaching test results for various types
of CCR, i.e., bottom ash, FGD gypsum, FGD sludge, fly ash cenospheres,
boiler slag, and combined waste streams. This included data from
several EPRI reports, which provided field leachate results for bottom
ash, fly ash, and FGD solids from a number of landfills and surface
impoundments. EPA also received leachate data from the Alaska
Department of Environmental Conservation, the Michigan Department of
Natural Resources and Environment (MI DNRE), and from the Maryland
Department of the Environment on total metals, TCLP, and SPLP results
for bottom ash and fly ash. Included among these data were TCLP results
for 102 CCR samples and 12 FGD gypsum samples, and two landfill
leachate samples, as well as several laboratory reports on CCR leachate
from 2008 through 2010. EPA also received several reports from the
University of North Dakota Energy & Environmental Research Center, with
leaching test results for 58 fly ash, five FGD, and four FGD gypsum
samples using various leaching methods other than TCLP, and TCLP
mercury results for 15 fly ash samples, as well as leaching test
results for five fly ash and two bottom ash samples using 18-hr, 30-
day, and 60-day leach methods, plus bulk and trace element data for
five fly ash samples, two bottom ash samples, and one slag sample. (See
76 FR 63252, October 12, 2011.)
    In addition to the data submitted by commenters, EPA's Office of
Research and Development (ORD), in collaboration with Vanderbilt
University (VU), developed additional CCR leaching data using a revised
methodology, the Leaching Environmental Assessment Framework, or LEAF,
consisting of four methods that evaluate leaching potential for various
waste forms at different plausible pH values and liquid-solid ratios,
in order to more accurately simulate leaching potential over a variety
of field conditions. The LEAF methods went through validation working
with 20 different laboratories, different waste matrices, and
documented in two EPA reports finding good agreement between the labs
for the four methods.\25\ In addition, EPA compiled decades of data for
ten different case studies to compare field and laboratory leach
data.\26\ These data also showed LEAF methods to be a good predictor of
field leachate behavior using geochemical speciation modeling for
factors such as oxidation that are difficult to account for in the lab.
When considered along with the methods validation, the field-to-lab
leachate data comparison provides additional confidence that LEAF
methods can more accurately predict environmental release over a range
of materials, waste form, pH, liquid-solid ratio, and other parameters
influencing leaching behavior such as calcium depletion for a material.
---------------------------------------------------------------------------

    \25\ Garrabrants A.C., D.S. Kosson, H.A. van der Sloot, F.
Sanchez and O. Hjelmar (2010) Background information for the
Leaching Environmental Assessment Framework (LEAF) Test Methods,
EPA-600/R-10/170, U.S. Environmental Protection Agency, Air
Pollution Prevention and Control Division, December 2010.
    Garrabrants A.C., D.S. Kosson, L. Stefanski, R. DeLapp, P.F.A.B.
Seignette, H.A. van der Sloot, P. Kariher and M. Baldwin (2012a)
Interlaboratory Validation of the Leaching Environmental Assessment
Framework (LEAF) Method 1313 and Method 1316, EPA/600/R-12/623, U.S.
Environmental Protection Agency, Air Pollution Prevention and
Control Division, September 2012.
    Garrabrants A.C., D.S. Kosson, R. DeLapp, P. Kariher, P.F.A.B.
Seignette, H.A. van der Sloot, L. Stefanski and M. Baldwin (2012b)
Interlaboratory Validation of the Leaching Environmental Assessment
Framework (LEAF) Method 1314 and Method 1315, EPA-600/R-12/624, U.S.
Environmental Protection Agency, Air Pollution Prevention and
Control Division, September 2012.
    \26\ Kosson D.S., van der Sloot, H.A., Seignette, P.F.A.B. 2014.
Leaching Test Relationships, Laboratory-to-Field Comparisons and
Recommendations for Leaching Evaluation using the Leaching
Environmental Assessment Framework (LEAF), EPA-600/R-14/061. EPA
Office of Research and Development, National Risk Management
Research Laboratory, Research Triangle Park, NC, 27711. December.
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    In updating the risk assessment for the final rule, EPA relied on
surface impoundment pore water data and impoundment wastewater data,
including the data submitted by commenters. For landfills, EPA only
used LEAF data to characterize the leachate for the range of materials
resulting from various air pollution control technologies. The CCR data
documented in three EPA reports \27\ and summarized in Thorneloe et al,
2010 \28\

provides a robust characterization of air pollution control residues
from coal-fired power plants and indicates that leaching rates can vary
by several orders of magnitude, depending on pH levels and the amount
of liquid that comes into contact with the CCR solids (i.e., the liquid
to solid ratio).
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    \27\ Sanchez F., R. Keeney, D.S. Kosson and R. DeLapp (2006)
Characterization of Mercury-Enriched Coal Combustion Residues from
Electric Utilities using Enhanced Sorbents for Mercury Control, EPA-
600/R-06/008, U.S. Environmental Protection Agency, Air Pollution
Prevention and Control Division, February 2006.
    Sanchez F., D.S. Kosson, R. Keeney, R. DeLapp, L. Turner and P.
Kariher (2008) Characterization of Coal Combustion Residues from
Electric Utilities using Wet Scrubbers for Multi-pollutant Control,
EPA-600/R-08/077, U.S. Environmental Protection Agency, Air
Pollution Prevention and Control Division, July 2008.
    Kosson D.S., F. Sanchez, P. Kariher, L.H. Turner, R. DeLapp, and
P. Seignette (2009) Characterization of Coal Combustion Residues
from Electric Utilities--Leaching and Characterization Data, EPA-