EPA Replaces the Clean Power Plan with the Affordable Clean Energy Rule

EPA Replaces the Clean Power Plan with the Affordable Clean Energy Rule

Legal Sidebari
EPA Replaces the Clean Power Plan with the
Affordable Clean Energy Rule
Linda Tsang
Legislative Attorney
July 11, 2019
On July 8, 2019, the U.S. Environmental Protection Agency (EPA) published its final Affordable Clean
Energy (ACE) Rule to regulate greenhouse gas (GHG) emissions from certain existing coal-fired electric
utility generating units (EGUs) at power plants. The ACE Rule replaces the Obama Administration’s
Clean Power Plan (CPP), which EPA repealed in a separate rulemaking on the same day. EPA also
finalized new implementing regulations for the ACE Rule and future emission guidelines issued under the
Clean Air Act (CAA) Section 111(d). These three rulemakings are to take effect on September 6, 2019.
The contrast between the CPP and the ACE Rule highlights a change in how EPA interprets its authority
and discretion under CAA Section 111. In the CPP, EPA interpreted the “best system of emission
reduction” (BSER) expansively to include on- and off-site emission reduction measures that would reduce
overall emissions from the power sector. In contrast, the CPP repeal and the ACE Rule adopt a narrower
interpretation of EPA’s authority under Section 111 and limit the BSER to a set of on-site energy
efficiency measures that can be applied to individual EGUs at power plants. This Sidebar explores the
legal bases for the repeal of the CPP and adoption of the ACE Rule and potential legal challenges to these
rulemakings. See this CRS Insight for additional information about the ACE Rule.
Legal Authority to Regulate EGU GHG Emissions
CAA Section 111 directs EPA to list categories of stationary sources that cause or contribute significantly
to “air pollution which may reasonably be anticipated to endanger public health or welfare.” Once EPA
lists a source category, such as fossil fuel-fired EGUs, Section 111(b) requires EPA to establish “standards
of performance” for new and modified sources (known as NSPSs) within the listed category. Under
Section 111(a), a “standard of performance” is defined as “a standard for emissions of air pollutants
which reflects the degree of emission limitation achievable through the application of the best system of
emission reduction [BSER].”
Congressional Research Service
7-5700
www.crs.gov
LSB10325
CRS Legal Sidebar
Prepared for Members and
Committees of Congress

Congressional Research Service
2
After issuing NSPSs under Section 111(b) for new or modified sources in that category, EPA establishes
“emission guidelines” for states to set a “standard of performance” for existing sources under Section
111(d). Once EPA has set emission guidelines for existing sources, the CAA requires states to develop
implementation plans that establish standards of performance for existing sources in their jurisdiction.
In 2015, EPA finalized both NSPSs for new or modified EGUs under Section 111(b) and emission
guidelines for existing EGUs (the CPP) under Section 111(d). EPA has since proposed to revise or replace
both of these standards. In 2018, the agency proposed to revise the NSPSs for new or modified EGUs and
repeal and replace the CPP. The July 8, 2019, rulemakings finalize the repeal of the CPP and replace it
with the ACE Rule. EPA intends to take a separate final action on related CAA permitting reforms it
proposed in 2018.
EPA’s Legal Basis for the CPP Repeal and Its Reinterpretation of the “Best System of Emission
Reduction” (BSER)
Much of the legal debate on the repeal of the CPP and the final ACE Rule centers on how EPA interprets
its authority under Section 111 to determine the BSER for existing EGUs. CAA Section 111(a) requires
standards of performance to reflect the emissions reductions achievable through “application” of the
BSER. As explained in prior agency and court interpretations of Section 111(a), EPA identifies and
evaluates the ‘‘adequately demonstrated’’ “system[s] of emission reduction’’ for a particular source
category to determine which is the “best’’ and sets emission standards based on the BSER, ‘‘taking into
account’’ ‘‘cost . . . nonair quality health and environmental impact and energy requirements.’’
In the CPP, EPA took an expansive view of its Section 111 authority to identify the BSER. EPA
determined that the BSER was a combination of on- and off-site emission reduction measures that applied
to the entire source category. EPA reasoned that the “system” in the BSER reflected the “overall source
category,” taking into account the “unique characteristics of CO2 [carbon dioxide] pollution and the
unique, interconnected and interdependent manner in which affected EGUs and other generating sources
operate within the electricity sector.” EPA based the CPP BSER for existing coal-fired and natural gas
units on three “building blocks”: (1) improving the heat rate at coal-fired units, (2) shifting generation to
lower-emitting natural gas units, and (3) shifting generation from fossil fuel units to renewable energy
generation.
In the CPP repeal, EPA now argues for a more narrow reading of its authority to determine the BSER
under Section 111. EPA asserts that the “application” of the BSER as referenced in CAA Section 111(a)
“unambiguously limits the BSER to those systems” that can be “applied” or “put into operation at a
building, structure, facility, or installation.” In other words, EPA contends that the CAA does not
authorize the agency to select as the BSER measures that apply to the source category as a whole or to
entities entirely outside the regulated source category. For the ACE Rule, EPA limited its analysis to on-
site emission reduction measures that could be applied directly to the unit. It finalized its proposed
determination that the BSER is on-site heat rate improvements (HRI) (i.e., energy efficiency measures)
and best operating and maintenance practices that reduce the CO2 emissions that a coal-fired EGU
releases per unit of electricity it generates.
During the rulemaking process for the CPP repeal and the ACE Rule, EPA’s interpretation of its authority
under Section 111 has evolved. Previously in its proposed repeal of the CPP, EPA acknowledged multiple
possible “readings” of the scope of its Section 111 authority, but in its repeal, the agency takes a more
definitive stance and claims its revised and final interpretation is the “only permissible reading” that EPA
must limit the BSER to source-specific measures. EPA reasons that the CPP “beyond-the-source”
approach “ignored or misinterpreted” the plain text of the CAA that “clearly precluded the unsupportable
reading” of Section 111 used in the CPP to choose emission reduction measures that are not directly
applied to the regulated EGU.

Congressional Research Service
3
EPA also points to the “explicit statutory link” between the CAA’s Prevention of Significant Deterioration
(PSD) permitting program and Section 111 standards to support its interpretation that the BSER must be
source-specific. Under CAA Section 165, PSD permits are based only on source- or facility-specific
emission control technologies, and Section 111 emission standards derived from the BSER act as a
“floor” (minimum) for emission limits in PSD permits. EPA contends that if Section 111 emission
standards are the “floor” for PSD permits (which are source-specific), EPA must base the BSER (and the
emission standards established by applying the BSER) only on what is achievable at an individual source.
In comparison, in the CPP, EPA did not apply PSD program policies or interpretations to its BSER
determination because it interpreted the PSD permitting program as distinct from Section 111(d) emission
guidelines. In the CPP, EPA observed that the PSD permitting program applies to individual modified or
new sources in contrast to Section 111(d) guidelines that apply to an entire source category and therefore
found the two programs and standard-setting processes distinguishable.
Because the CPP BSER was based, in part, on “beyond-the-source” measures, EPA asserts in the ACE
Rule that the CPP “significantly exceeded” its authority after reconsidering the relevant statutory text,
structure, and purpose of CAA Section 111. Therefore, EPA repeals the CPP and limits the BSER in the
ACE Rule to emission reduction measures that can be applied only at individual EGUs.
Distinct Roles for EPA and the States in the ACE Rule
The ACE Rule and CPP also differ in their legal interpretations of the states’ role in setting emission
standards. Section 111(d) delineates specific statutory roles for EPA and the states, requiring the EPA to
establish “a procedure” (i.e., emission guidelines) “under which each State shall submit to the [EPA]
Administrator a plan which . . . establishes standards of performance for any existing source.” In the ACE
Rule, EPA explains that Section 111(d) requires the agency to identify the BSER and the degree of
emission limitation achievable by applying the BSER. In EPA’s view, Section 111(d) explicitly requires
states, not EPA, to establish emission standards reflecting the application of the BSER for each existing
source by considering source-specific factors. Therefore, EPA declines to set an emission standard that
presumptively reflects application of the BSER in the ACE Rule.
The ACE Rule requires states to set GHG emission standards, based on the ACE Rule BSER. In the ACE
Rule, EPA identifies the BSER as six “candidate” HRI technologies and best operating and maintenance
practices and specifies a “range” of expected emissions reductions associated with each of the
technologies. For each regulated EGU, the states must (1) evaluate the applicability of all “candidate”
HRI technologies and best operating and maintenance practices, (2) determine which candidate
technologies or practices are appropriate, and (3) establish CO2 standards based on the emission
reductions that the technology could achieve at the unit. States must submit to EPA for approval plans
detailing how the state (1) applied BSER to each source in setting the standards, and (2) will implement
and enforce such standards.
This interpretation of the federal and state roles in standard setting and state implementation differs from
the CPP. For the CPP, EPA used the BSER to set national CO2 emission standards of performance for both
fossil-fuel steam units (which are mostly coal units) and natural gas combined cycle units. Based on these
national standards, EPA established state-specific emission reduction goals. Under this approach, states
had discretion on how to meet those goals when developing their implementation plans (e.g., setting unit-
specific emission standards or establishing a state or regional cap-and-trade program), but did not have
discretion to set their state emission reduction goals or alter the national standards.
The ACE Rule and the CPP also diverge in their interpretation of the Section 111(d) provision that allows
states to consider the “remaining useful life of an existing source” and “other factors” when “applying” a
standard of performance to a particular source. EPA, in the ACE Rule, interprets this provision to allow
states to consider these factors when “establishing” emission standards, including the costs of
implementing HRI and technical feasibility. EPA acknowledges that consideration of such factors could

Congressional Research Service
4
result in source-specific emission standards “that reflect a value of HRI that falls outside” the emission
reduction ranges that EPA identified for each technology. The CPP, in contrast, only allowed states to
consider these factors when determining how to apply the national emission standards to existing EGUs,
and prohibited states from making “adjustments” to the mandatory statewide emission reduction goals
based on these source-specific factors.
Legal Challenges to EPA’s Interpretation of CAA Section 111(d)
Under CAA Section 307(d), a court may reverse an agency action that the court finds to be, among other
things, “arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law” or “in
excess of statutory jurisdiction, authority, or limitations.” Many of the legal issues raised in the litigation
challenging the CPP, including the scope of EPA’s authority and its interpretation of the BSER, may also
be central to legal challenges to the repeal of the CPP and implementation of the ACE Rule. For example,
in litigation challenging the CPP, petitioners claimed that the CPP is unlawful because Congress must
issue a “clear statement” of authority for an agency action that could have potentially serious economic
and political implications. In contrast, supporters of the CPP argued that EPA has discretion under Section
111(d) to consider all inside- and outside-the-fenceline measures to reduce emissions from existing EGUs.
Stakeholders may argue that EPA’s narrow interpretation of Section 111 in the ACE Rule and CPP repeal
is arbitrary and capricious.
Furthermore, the court would review whether EPA adequately justified its changed legal interpretation of
Section 111. EPA contends that it has discretion to change its interpretation of its legal authority so long
as it provides a “reasonable explanation” for the change. An agency rule that implements a policy change
by amending or repealing an existing rule is generally subject to the often deferential arbitrary and
capricious judicial review. However, the Supreme Court has held that when “serious reliance interests are
at stake,” an agency must present a “more reasoned explanation” for “why it deemed it necessary to
overrule its previous position.” As a result, EPA’s justification for overruling its previous legal
interpretation of Section 111 may face additional scrutiny if stakeholders can show “serious reliance” on
the CPP and its legal interpretations.
Next Steps
Under CAA Section 307(b), stakeholders may file a petition for review of the final CPP repeal or the final
ACE Rule with the U.S. Court of Appeals for the District of Columbia Circuit (D.C. Circuit) by
September 6, 2019. On July 8, 2019, the American Lung Association and the American Public Health
Association filed a petition for review in the D.C. Circuit. Several states, including New York and
California, have announced their intent to challenge the ACE Rule and the CPP repeal. Other stakeholders
and states, who opposed and challenged the CPP in court in 2015, will likely support EPA’s new legal
interpretation of CAA Section 111 and its inside-the-fenceline approach. The litigation challenging the
CPP, which the court paused during EPA’s review of the CPP, is essentially moot now that EPA has
finalized its repeal of the CPP. Petitioners of the CPP repeal or ACE Rule may also ask the court to stay
(i.e., pause) the rulemakings, similar to the petitioners’ request to stay the implementation and
enforcement of the CPP.
A court decision on the repeal of the CPP and the ACE Rule could set a precedent on the scope of EPA’s
authority to determine which emission reduction measures it may consider for EGUs and to set future
Section 111(d) emission guidelines for other existing industrial sources of pollution. Further, a judicial
decision upholding the states’ role in setting emission standards on a case-by-case application of the
BSER could have significant legal implications. Some states are concerned that the lack of uniform,
national emission standards in the ACE Rule could increase their litigation risks, as stakeholders may
challenge the standards the state sets for each EGU.
Congress could consider proposing legislation that would clarify the scope of EPA’s authority under CAA
Section 111 and the definition of the BSER, or it could consider participating in litigation. Congress took

Congressional Research Service
5
an active interest in the fate of the CPP since it was proposed in 2014 and subsequently challenged in
court. For instance, Members of Congress filed amici curiae briefs on both sides of the CPP litigation. A
brief opposing the CPP argued, among other things, that EPA “usurped the role of Congress” through the
CPP's “expansive regulatory requirements.” A brief in support of the CPP argued, among other things,
that Congress conferred “broad authority” on EPA, and that the CPP is “consistent with the text, structure,
and history” of the CAA.