[Federal Register Volume 70, Number 128 (Wednesday, July 6, 2005)]
[Rules and Regulations]
[Pages 39104-39172]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 05-12526]



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Part III





Environmental Protection Agency





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40 CFR Part 51



Regional Haze Regulations and Guidelines for Best Available Retrofit 
Technology (BART) Determinations; Final Rule

  Federal Register / Vol. 70, No. 128 / Wednesday, July 6, 2005 / Rules 
and Regulations  

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 51

[FRL-7925-9]
RIN 2060-AJ31


Regional Haze Regulations and Guidelines for Best Available 
Retrofit Technology (BART) Determinations

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: On July 1, 1999, EPA promulgated regulations to address 
regional haze (64 FR 35714). These regulations were challenged, and on 
May 24, 2002, the U.S. Court of Appeals for the District of Columbia 
Circuit issued a ruling vacating the regional haze rule in part and 
sustaining it in part. American Corn Growers Ass'n v. EPA, 291 F.3d 1 
(D.C. Cir. 2002). Today's rule addresses the court's ruling in that 
case.
    In addition, prior to the court's decision, EPA had proposed 
guidelines for implementation of the Best Available Retrofit Technology 
(BART) requirements under the regional haze rule, (66 FR 38108, July 
20, 2001). The proposed guidelines were intended to clarify the 
requirements of the regional haze rule's BART provisions. We proposed 
to add the guidelines and also proposed to add regulatory text 
requiring that these guidelines be used for addressing BART 
determinations under the regional haze rule. In addition, we proposed 
one revision to guidelines issued in 1980 for facilities contributing 
to ``reasonably attributable'' visibility impairment.
    In the American Corn Growers case, the court vacated and remanded 
the BART provisions of the regional haze rule. In response to the 
court's ruling, on May 5, 2004 we proposed new BART provisions and 
reproposed the BART guidelines. The American Corn Growers court also 
remanded to the Agency its decision to extend the deadline for the 
submittal of regional haze plans. Subsequently, Congress amended the 
deadlines for regional haze plans (Consolidated Appropriations Act for 
Fiscal Year 2004, Public Law 108-199, January 23, 2004). The May 5, 
2004 proposed rule also contained an amendment to the regional haze 
rule to conform to the new statutory deadlines.
    We received numerous comments on both the July 20, 2001 proposal 
and the May 5, 2004 reproposal. Today's final rule reflects our review 
of the public comments.

DATES: The regulatory amendments announced herein take effect on 
September 6, 2005.

ADDRESSES: Docket. All documents in the docket are listed in the 
EDOCKET index at http://www.epa.gov/edocket. Although listed in the 
index, some information is not publicly available, i.e., 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 
EDOCKET or in hard copy at the OAR Docket, EPA/DC, EPA West, Room B102, 
1301 Constitution Ave., NW., Washington, DC. 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 
(202) 566-1744, and the telephone number for the OAR Docket is (202) 
566-1742.

FOR FURTHER INFORMATION CONTACT: Kathy Kaufman at (919) 541-0102 or by 
e-mail at [email protected] or Todd Hawes at 919-541-5591 or by e-
mail [email protected].

SUPPLEMENTARY INFORMATION:
    Regulated Entities. This final rule will affect the following: 
State and local permitting authorities and Indian Tribes containing 
major stationary sources of pollution affecting visibility in federally 
protected scenic areas.
    This list is not intended to be exhaustive, but rather provides a 
guide for readers regarding entities likely to be regulated by this 
action. This list gives examples of the types of entities EPA is now 
aware could potentially be regulated by this action. Other types of 
entities not listed could also be affected. To determine whether your 
facility, company, business, organization, etc., is regulated by this 
action, you should examine the applicability criteria in Part II of 
this preamble. If you have any questions regarding the applicability of 
this action to a particular entity, consult the people listed in the 
preceding section.
    Outline. The contents of today's preamble are listed in the 
following outline.

I. Overview of Today's Proposed Actions
II. Background
    A. Regional Haze Rule
    B. Partial Remand of the Regional Haze Rule in American Corn 
Growers
    C. Changes in Response to American Corn Growers
    D. Center for Energy and Economic Development v. EPA
    E. Relationship Between BART and the Clean Air Interstate Rule 
(CAIR)
    F. Overview of the BART Process
III. Detailed Discussion of the BART Guidelines
    A. Introduction
    B. Scope of the Rule--Whether to Require States to Follow the 
Guidelines for All BART Sources
    C. How to Identify BART-Eligible Sources
    D. How to Determine Which BART-Eligible Sources are Subject to 
BART
    E. The BART Determination Process
IV. Effect of This Rule on State Options for Using Alternative 
Strategies In Lieu of Source-by-Source BART
V. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination with 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children from 
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions That Significantly Affect 
Energy Supply, Distribution, or Use.
    I. National Technology Transfer Advancement Act
    J. Executive Order 12898: Federal Actions to Address 
Environmental Justice in Minority Populations and Low-Income 
Populations

I. Overview of Today's Actions

    Today's rulemaking provides the following changes to the regional 
haze regulations:
    (1) Revised regulatory text in response to the American Corn 
Growers court's remand, to require that the BART determination include 
an analysis of the degree of visibility improvement resulting from the 
use of control technology at each source subject to BART,
    (2) Revised regulatory text in 40 CFR 51.308(b) and deletion of 40 
CFR 51.308(c) Options for regional planning in response to 
Congressional legislation amending the deadlines for submittal of 
regional haze implementation plans. This provision had provided for an 
alternative process for States to submit regional haze implementation 
plans in attainment areas,
    (3) BART guidelines, contained in a new Appendix Y to 40 CFR part 
51,
    (4) New and revised regulatory text, to be added to 40 CFR 
51.308(e), regarding the use of Appendix Y in establishing BART 
emission limits, and
    (5) Revised regulatory language at 40 CFR 51.302 to clarify the 
relationship between New Source Performance Standards (NSPS) and BART 
for reasonably attributable visibility impairment.
    How This Preamble Is Structured. Section II provides background on 
the

[[Page 39105]]

Clean Air Act (CAA) BART requirements as codified in the regional haze 
rule, on the D.C. Circuit Court decision which remanded parts of the 
rule, and on the April 2004 reproposal responding to the remand. 
Section III discusses specific issues in the BART guidelines in more 
detail, including background on each issue, major comments we received 
on the July 2001 proposal and May 2004 reproposal, and our responses to 
those comments. Section IV provides a discussion of how this rulemaking 
complies with the requirements of Statutory and Executive Order 
Reviews.

II. Background

A. The Regional Haze Rule

    In 1999, we published a final rule to address a type of visibility 
impairment known as regional haze (64 FR 35714, July 1, 1999). The 
regional haze rule requires States to submit implementation plans 
(SIPs) to address regional haze visibility impairment in 156 Federally-
protected parks and wilderness areas. These 156 scenic areas are called 
``mandatory Class I Federal areas'' in the Clean Air Act (CAA)\1\ but 
are referred to simply as ``Class I areas'' in today's rulemaking. The 
1999 rule was issued to fulfill a long-standing EPA commitment to 
address regional haze under the authority and requirements of sections 
169A and 169B of the CAA.
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    \1\ See, e.g. CAA Section 169A(a)(1).
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    As required by the CAA, we included in the final regional haze rule 
a requirement for BART for certain large stationary sources that were 
put in place between 1962 and 1977. We discussed these requirements in 
detail in the preamble to the final rule (64 FR at 35737-35743). The 
regulatory requirements for BART were codified at 40 CFR 51.308(e) and 
in definitions that appear in 40 CFR 51.301.
    The CAA, in sections 169A(b)(2)(A) and in 169A(g)(7), uses the term 
``major stationary source'' to describe those sources that are the 
focus of the BART requirement. To avoid confusion with other CAA 
requirements which also use the term ``major stationary source'' to 
refer to a somewhat different population of sources, the regional haze 
rule uses the term ``BART-eligible source'' to describe these sources. 
The BART-eligible sources are those sources which have the potential to 
emit 250 tons or more of a visibility-impairing air pollutant, were put 
in place between August 7, 1962 and August 7, 1977, and whose 
operations fall within one or more of 26 specifically listed source 
categories. Under the CAA, BART is required for any BART-eligible 
source which a State determines ``emits any air pollutant which may 
reasonably be anticipated to cause or contribute to any impairment of 
visibility in any such area.'' Accordingly, for stationary sources 
meeting these criteria, States must address the BART requirement when 
they develop their regional haze SIPs.
    Section 169A(g)(7) of the CAA requires that States must consider 
the following factors in making BART determinations:
    (1) The costs of compliance,
    (2) The energy and nonair quality environmental impacts of 
compliance,
    (3) Any existing pollution control technology in use at the source,
    (4) The remaining useful life of the source, and
    (5) The degree of improvement in visibility which may reasonably be 
anticipated to result from the use of such technology.

These statutory factors for BART were codified at 40 CFR 
51.308(e)(1)(ii).
    In the preamble to the regional haze rule, we committed to issuing 
further guidelines to clarify the requirements of the BART provision. 
The purpose of this rulemaking is to fulfill this commitment by 
providing guidelines to assist States as they identify which of their 
BART-eligible sources should undergo a BART analysis (i.e., which are 
``sources subject to BART'') and select controls in light of the 
statutory factors listed above (``the BART determination'').

B. Partial Remand of the Regional Haze Rule in American Corn Growers v. 
EPA

    In response to challenges to the regional haze rule by various 
petitioners, the D.C. Circuit in American Corn Growers \2\ issued a 
ruling striking down the regional haze rule in part and upholding it in 
part. This section discusses the court's opinion in that case as 
background for the discussion of specific changes to the regional haze 
rule and the BART guidelines presented in the next two sections, 
respectively.
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    \2\ American Corn Growers et al. v. EPA, 291 F.3d 1 (2002).
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    We explained in the preamble to the 1999 regional haze rule that 
the BART requirements in section 169A(b)(2)(A) of the CAA demonstrate 
Congress' intent to focus attention directly on the problem of 
pollution from a specific set of existing sources (64 FR 35737). The 
CAA requires that any of these existing sources ``which, as determined 
by the State, emits any air pollutant which may reasonably be 
anticipated to cause or contribute to any impairment of visibility [in 
a Class I area],'' shall install the best available retrofit technology 
for controlling emissions.\3\ In determining BART, the CAA requires the 
State to consider several factors that are set forth in section 
169(g)(2) of the CAA, including the degree of improvement in visibility 
which may reasonably result from the use of such technology.
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    \3\ CAA sections 169A(b)(2) and (g)(7).
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    The regional haze rule addresses visibility impairment resulting 
from emissions from a multitude of sources located across a wide 
geographic area. Because the problem of regional haze is caused in 
large part by the long-range transport of emissions from multiple 
sources, and for certain technical and other reasons explained in that 
rulemaking, we had adopted an approach that required States to look at 
the contribution of all BART sources to the problem of regional haze in 
determining both applicability and the appropriate level of control. 
Specifically, we had concluded that if a source potentially subject to 
BART is located within an upwind area from which pollutants may be 
transported downwind to a Class I area, that source ``may reasonably be 
anticipated to cause or contribute'' to visibility impairment in the 
Class I area. Similarly, we had also concluded that in weighing the 
factors set forth in the statute for determining BART, the States 
should consider the collective impact of BART sources on visibility. In 
particular, in considering the degree of visibility improvement that 
could reasonably be anticipated to result from the use of such 
technology, we stated that the State should consider the degree of 
improvement in visibility that would result from the cumulative impact 
of applying controls to all sources subject to BART. We had concluded 
that the States should use this analysis to determine the appropriate 
BART emission limitations for specific sources.\4\
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    \4\ See 66 FR at 35737-35743 for a discussion of the rationale 
for the BART requirements in the 1999 regional haze rule.
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    In American Corn Growers v. EPA, industry petitioners challenged 
EPA's interpretation of both these aspects of the BART determination 
process and raised other challenges to the rule. The court in American 
Corn Growers concluded that the BART provisions in the 1999 regional 
haze rule were inconsistent with the provisions in the CAA ``giving the 
states broad authority over BART determinations.'' 291 F.3d at 8. 
Specifically, with respect to the test for determining whether a source 
is subject to BART, the court held that the

[[Page 39106]]

method that EPA had prescribed for determining which eligible sources 
are subject to BART illegally constrained the authority Congress had 
conferred on the States. Id. The court did not decide whether the 
general collective contribution approach to determining BART 
applicability was necessarily inconsistent with the CAA. Id. at 9. 
Rather, the court stated that ``[i]f the [regional haze rule] contained 
some kind of a mechanism by which a state could exempt a BART-eligible 
source on the basis of an individualized contribution determination, 
then perhaps the plain meaning of the Act would not be violated. But 
the [regional haze rule] contains no such mechanism.'' Id. at 12.
    The court in American Corn Growers also found that our 
interpretation of the CAA requiring the States to consider the degree 
of improvement in visibility that would result from the cumulative 
impact of applying controls in determining BART was inconsistent with 
the language of the Act. 291 F.3d at 8. Based on its review of the 
statute, the court concluded that the five statutory factors in section 
169A(g)(2) ``were meant to be considered together by the states.'' Id. 
at 6.

C. Changes in Response to American Corn Growers

    Today's rule responds to the American Corn Growers court's decision 
on the BART provisions by including changes to the regional haze rule 
at 40 CFR 51.308, and by finalizing changes to the BART guidelines. 
This section outlines the changes to the regional haze rule due to the 
court's remand. It also explains the minor change we are making to the 
section of the regulation governing the use of the 1980 BART guidelines 
when conducting BART analyses for certain power plants for reasonably 
attributable (i.e., localized) visibility impairment.
1. Determination of Which Sources Are Subject to BART
    Today's action addresses the American Corn Growers court's vacature 
of the requirement in the regional haze rule requiring States to assess 
visibility impacts on a cumulative basis in determining which sources 
are subject to BART. Because this requirement was found only in the 
preamble to the 1999 regional haze rule (see 291 F.3d at 6, citing 64 
FR 35741), no changes to the regulations are required. Instead, this 
issue is addressed in the BART guidelines, which provide States with 
appropriate techniques and methods for determining which BART-eligible 
sources ``may reasonably be anticipated to cause or contribute to any 
impairment of visibility in any mandatory Class I Federal area.'' These 
processes, to address the holding of American Corn Growers by 
eliminating the previous constraint on State discretion, are explained 
in further detail in sections II.D. and III below.
2. Consideration of Anticipated Visibility Improvements in BART 
Determinations
    Pursuant to the remand in American Corn Growers, we are amending 
the regional haze rule to require the States to consider the degree of 
visibility improvement resulting from a source's installation and 
operation of retrofit technology, along with the other statutory 
factors set out in CAA section 169A(g)(2), when making a BART 
determination. This has been accomplished by listing the visibility 
improvement factor with the other statutory BART determination factors 
in 40 CFR 51.308(e)(1)(A), so that States will be required to consider 
all five factors, including visibility impacts, on an individual source 
basis when making each individual source BART determination.

D. Center for Energy and Economic Development v. EPA

    After the May 2004 reproposal of the BART guidelines, the D.C. 
Circuit decided another case where BART provisions were at issue, 
Center for Energy and Economic Development v. EPA, 398 F.3d 653, 2005 
(``CEED''). In this case, the court granted a petition challenging 
provisions of the regional haze rule governing the optional emissions 
trading program for certain western States and Tribes (the ``WRAP Annex 
Rule'').
    The court in CEED affirmed our interpretation of CAA section 
169A(b)(2) as allowing for non-BART alternatives where those 
alternatives are demonstrated to make greater progress than BART. 
(CEED, slip. op. at 13). The court, however, took issue with provisions 
of the regional haze rule governing the methodology of that 
demonstration. Specifically, 40 CFR 51.308(e)(2) requires that 
visibility improvements under source-specific BART--the benchmark for 
comparison to the alternative program--be estimated based on the 
application of BART controls to all sources subject to BART. (This 
section was incorporated into the WRAP Annex rule by reference at 40 
CFR 51.309(f)). The court held that we could not require this type of 
group BART approach--vacated in American Corn Growers in a source-
specific BART context--even in a program in which State participation 
was wholly optional.
    The BART guidelines as proposed in May 2004 contained a section 
offering guidance to States choosing to address their BART-eligible 
sources under the alternative strategy provided for in 40 CFR 
51.308(e)(2). This guidance included criteria for demonstrating that 
the alternative program achieves greater progress towards eliminating 
visibility impairment than would BART.
    In light of the D.C. Circuit's decision in CEED, we have not 
included the portion of the proposed BART guidelines addressing 
alternative programs in today's rulemaking. We remain committed to 
providing States with the flexibility to address BART through 
alternative means, and we note again that our authority to do so was 
upheld in CEED. Therefore, we intend to revise the provisions of the 
regional haze rule governing such alternatives and provide any 
additional guidance needed in a subsequent rulemaking conducted as 
expeditiously as practicable.

E. Relationship Between BART and the Clean Air Interstate Rule (CAIR)

    On March 10, 2005, EPA issued the Clean Air Interstate Rule (CAIR), 
requiring reductions in emissions of sulfur dioxide (SO2) 
and nitrogen oxides (NOX) in 28 eastern States and the 
District of Columbia. When fully implemented, CAIR will reduce 
SO2 emissions in these states by over 70 percent and 
NOX emissions by over 60 percent from 2003 levels. The CAIR 
imposes specified emissions reduction requirements on each affected 
State, and establishes an EPA-administered cap and trade program for 
EGUs in which States may participate as a means to meet these 
requirements. The relationship between BART and the Clean Air 
Interstate Rule (CAIR) is discussed in section IV. below.

F. Overview of the BART Process

    The process of establishing BART emission limitations can be 
logically broken down into three steps: First, States identify those 
sources which meet the definition of ``BART-eligible source'' set forth 
in 40 CFR 51.301. Second, States determine whether such sources 
``emit[] any air pollutant which may reasonably be anticipated to cause 
or contribute to any impairment of visibility [in a Class I area.]'' A 
source which fits this description is ``subject to BART.'' Third, for 
each source subject to BART, States then identify the appropriate type 
and the level of control for reducing emissions.

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    Identifying BART-eligible sources. The CAA defines BART-eligible 
sources as those sources which fall within one of 26 specific source 
categories, were built during the 15-year window of time from 1962 to 
1977, and have potential emissions greater than 250 tons per year. The 
remand did not address the step of identifying BART-eligible sources, 
which is conceptually the simplest of the three steps.
    Sources reasonably anticipated to cause or contribute to visibility 
impairment (sources subject to BART). As we noted in the preamble to 
the 1999 regional haze rule, defining the individual contributions of 
specific sources of the problem of regional haze can be time-consuming 
and expensive. Moreover, Congress established a very low threshold in 
the CAA for determining whether a source is subject to BART. We are 
accordingly finalizing several approaches for States for making the 
determination of whether a source ``emits any pollutants which may 
reasonably be anticipated to cause or contribute to any visibility 
impairment.'' Certain of these approaches would allow States to avoid 
undertaking unnecessary and costly studies of an individual source's 
contribution to haze by allowing States to adopt more streamlined 
processes for determining whether, or which, BART-eligible sources are 
subject to BART.
    In 1999, we adopted an applicability test that looked to the 
collective contribution of emissions from an area. In particular, we 
stated that if ``a State should find that a BART-eligible source is 
`reasonably anticipated to cause or contribute' to regional haze if it 
can be shown that the source emits pollutants within a geographic area 
from which pollutants can be emitted and transported downwind to a 
Class I area.'' \5\ States certainly have the discretion to consider 
that all BART-eligible sources within the State are ``reasonably 
anticipated to cause or contribute'' to some degree of visibility 
impairment in a Class I area.
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    \5\ 64 FR 335740, July 1, 1999. The regional haze rule discusses 
at length why we believe that States should draw this conclusion. 64 
FR at 35739-35740.
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    This is consistent with the American Corn Growers court's decision. 
As previously noted, the court's concern with our original approach 
governing BART applicability determinations was that it would have 
``tie[d] the states' hands and force[d] them to require BART controls 
at sources without any empirical evidence of the particular source's 
contribution to visibility impairment.'' 291 F.3d at 8. By the same 
rationale, we believe it would be an impermissible constraint of State 
authority for the EPA to force States to conduct individualized 
analyses in order to determine that a BART-eligible source ``emits any 
air pollutant which may reasonably be anticipated to cause or 
contribute to any impairment of visibility in any [Class I] area.'' \6\ 
American Corn Growers did not decide whether consideration of 
visibility impact on a cumulative basis would be invalid in all 
circumstances. 291 F.3d at 9. Given the court's emphasis on the 
importance of the role of the States in making BART determinations, we 
believe that a State's decision to use a cumulative analysis at the 
eligibility stage is consistent with the CAA and the findings of the 
D.C. Circuit.
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    \6\ CAA section 169A(b)(2)(A).
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    We believe a State may conclude that all BART-eligible sources 
within the State are subject to BART.\7\ Any potential for inequity 
towards sources could be addressed at the BART determination stage, 
which contains an individualized consideration of a source's 
contribution in establishing BART emission limits.
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    \7\ See 64 FR at 35714, 35721; see also Supporting Information 
for Proposed Applicability of Regional Haze Regulations, Memorandum 
by Rich Damberg to Docket A-95-38, U.S. Environmental Protection 
Agency, Office of Air Quality Planning and Standards, July 29, 1997.
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    States also have the option of performing an analysis to show that 
the full group of BART-eligible sources in a State cumulatively may not 
be reasonably anticipated to cause or contribute to any visibility 
impairment in Class I areas. We anticipate that in most, if not all 
States, the BART-eligible sources are likely to cause or contribute to 
some visibility impairment in Class I areas. However, it is possible 
that using a cumulative approach, a State could show that its BART 
sources do not pose a problem.
    Finally, States may consider the individualized contribution of a 
BART-eligible source to determine whether a specific source is subject 
to BART. Specifically, States may choose to undertake an analysis of 
each BART-eligible source in the State in considering whether each such 
source meets the test set forth in the CAA of ``emit[ting] any air 
pollutant which may reasonably be anticipated to cause or contribute to 
any impairment of visibility in any [Class I] area.'' Alternatively, 
States may choose to presume that all BART-eligible sources within the 
State meet this applicability test, but provide sources with the 
ability to demonstrate on a case by case basis that this is not the 
case. Either approach appears consistent with the D.C. Circuit's 
statement that a collective contribution approach may be appropriate so 
long as the States are allowed to exempt sources on the basis of an 
individualized contribution determination. 291 F.3d at 8.
    Today's guidelines include different options States can use to 
assess whether source should be subject to BART. States need to 
determine whether to make BART determinations for all of their BART-
eligible sources, or to consider exempting some of them from BART 
because they may not reasonably be anticipated to cause or contribute 
to any visibility impairment in a Class I area. For assessing the 
impact of BART-eligible sources on nearby Class I areas, we are 
including a process whereby the States would use an air quality model 
able to estimate a single source's contribution to visibility 
impairment and a different process whereby States could exempt groups 
of sources with common characteristics based on representative model 
plant analyses. Finally, States may use cumulative modeling to show 
that no sources in a State are subject to BART.
    The BART determination. The State must determine the appropriate 
level of BART control for each source subject to BART. Section 
169A(g)(7) of the CAA requires States to consider the following factors 
in making BART determinations: (1) The costs of compliance, (2) the 
energy and nonair quality environmental impacts of compliance, (3) any 
existing pollution control technology in use at the source, (4) the 
remaining useful life of the source, and (5) the degree of improvement 
in visibility which may reasonably be anticipated to result from the 
use of such technology. The remand did not address the first four steps 
of the BART determination. The remand did address the final step, 
mandating that we must permit States to take into account the degree of 
improvement in visibility that would result from imposition of BART on 
each individual source when deciding on particular controls.
    The first four factors are somewhat similar to the engineering 
analysis in the original BART guidelines proposed in 2001 and 
reproposed in 2004. The BART guidelines also contains a detailed 
discussion of available and cost-effective controls for reducing 
SO2 and NOX emissions from large coal-fired 
electric generating units (EGUs).
    For assessing the fifth factor, the degree of improvement in 
visibility from various BART control options, the States may run 
CALPUFF or another appropriate dispersion model to predict visibility 
impacts. Scenarios would be

[[Page 39108]]

run for the pre-controlled and post-controlled emission rates for each 
of the BART control options under review. The maximum 24-hour emission 
rates would be modeled for a period of three or five years of 
meteorological data. States have the flexibility to develop their own 
methods to evaluate model results.

III. Detailed Discussion of the Final BART Guidelines

A. Introduction

    In this section of the preamble, we discuss changes or 
clarifications to the reproposed BART guidelines. Where relevant, we 
also respond to comments received during the comment period on the 2001 
proposal. For each provision of the guidelines that we are changing or 
clarifying, we provide discussion of, as appropriate:

--Background information,
--How the provision was addressed in the May 2004 reproposal (and in 
the 2001 proposal, if different from the reproposal),
--A summary of comments received on the provision, either from the May 
2004 reproposal, from the July 2001 proposal, or from both, and
--The changes or clarifications that we are finalizing and the reasons 
for these changes or clarifications.

B. Scope of the Rule--Whether To Require States To Follow the 
Guidelines for All BART Sources

    Background. Section 169A(b)(1) of the CAA requires EPA to issue 
regulations to provide guidelines to States on the implementation of 
the visibility program. In addition, the last sentence of section 
169A(b) states:

    In the case of a fossil-fuel fired generating powerplant having 
a capacity in excess of 750 megawatts, the emission limitations 
required under this paragraph shall be determined pursuant to 
guidelines, promulgated by the Administrator under paragraph (1).

    This statutory requirement clearly requires us to promulgate BART 
guidelines that the States must follow in establishing BART emission 
limitations for power plants with a total capacity exceeding the 750 
megawatt cutoff. The statute is less clear regarding the import of the 
guidelines for sources other than 750 megawatt power plants.
    Proposed rules. Both the 2001 proposal and the 2004 reproposal 
included a requirement for States to follow the procedures set out in 
the guidelines in determining BART for sources in all of the 26 listed 
BART categories. The 2001 proposal requested comment on whether the 
regional haze rule should: (1) Require the use of the guidelines only 
for 750 megawatt utilities, with the guidelines applying as guidance 
for the remaining categories, or (2) require the use of the guidelines 
for all of the affected source categories.
    Comments. We received comments on this issue in both 2001 and 2004. 
Comments varied widely on whether we can or should require the use of 
the guidelines for all of the affected source categories.
    Comments from State, local and tribal air quality agencies 
generally supported our proposal to require the use of the guidelines 
for all of the source categories. These comments cited a need for 
national consistency in the application of the BART requirement across 
the source categories, and from State to State. One State agency 
commenter questioned our legal authority to require the use of the 
guidelines for all source categories; and several State agency 
commenters, while supporting the proposal, requested that we provide 
clarification of the legal authority for requiring the States to use 
the guidelines in establishing BART emission limitations for all 
categories.
    Comments from the utility industry, from various manufacturing 
trade groups, and from individual companies were critical of the 
proposal to require States to follow the guidelines generally. Many 
commenters also argued that EPA lacked the authority to issue 
guidelines for any industrial category other than 750 megawatt 
powerplants, whether the use of such guidelines were mandatory or not. 
Other commenters stated that the language in the CAA clearly restricts 
the scope of mandatory guidelines to larger powerplants. The commenters 
cited the legislative history of the 1977 Clean Air Act amendments in 
support of this position, and frequently claimed that requiring the 
guidelines for all 26 categories of sources would deprive States of 
flexibility in implementing the program.
    Comments from environmental organizations and the general public 
supported the approach in the proposed rule and stated that EPA is 
obligated to establish regional haze BART guidelines by rulemaking for 
all 26 categories of stationary sources. Environmental organization 
comments noted that while Congress expressed a particular concern for 
750 MW powerplants, this added emphasis on one sector does not change 
requirements in the Act for all BART-eligible sources. Accordingly, 
these commenters believed that we should not construe a special 
emphasis on powerplants as a restriction on our authority to require 
use of the guidelines for all categories.
    Final rule. The CAA and the relevant legislative history make clear 
that EPA has the authority and obligation to publish mandatory 
guidelines for powerplants exceeding 750 megawatts. As previously 
noted, Congress in section 169A(b) of the CAA expressly provided that 
emission limitations for powerplants larger than 750 megawatts ``shall 
be determined pursuant to guidelines promulgated by the 
Administrator.'' (Emphasis added). This unambiguous language leaves 
little room to dispute that the guidelines EPA is required to 
promulgate must be used by States when making BART determinations for 
this class of sources.
    Having carefully considered the comments and further reviewed the 
CAA and the legislative history, we have concluded that it would not be 
appropriate for EPA to require States to use the guidelines in making 
BART determinations for other categories of sources. The better reading 
of the Act indicates that Congress intended the guidelines to be 
mandatory only with respect to 750 megawatt powerplants. Thus, while we 
acknowledge the State agency comments and the policy reasons support 
consistency across States, we are not requiring States to use the BART 
guideline for these other categories. In response to State concerns 
about equitable application of the BART requirement to source owners 
with similar sources in different States, we do encourage States to 
follow the guidelines for all source categories but are not requiring 
States to do so. States should view the guidelines as helpful guidance 
for these other categories.
    We disagree with comments that the CAA and the legislative history 
prohibit us from issuing guidance for other source categories. As the 
guidelines make clear, States are not required to follow the approach 
in the guidelines for sources other than 750 megawatt powerplants. As 
such, although we believe that the guidelines provide useful advice in 
implementing the BART provisions of the regional haze rule, we do not 
believe that they hamper State discretion in making BART 
determinations.

C. How To Identify BART-Eligible Sources

    Section II of the BART guidelines contains a step-by-step process 
for identifying stiationary sources that are ``BART-eligible'' under 
the definitions in the regional haze rule. The four basic steps are:
    Step 1: Identify the emission units in the BART categories.
    Step 2: Identify the start-up dates of those emission units.

[[Page 39109]]

    Step 3: Compare the potential emissions from units identified in 
Steps 1 and 2 to the 250 ton/year cutoff.
    Step 4: Identify the emission units and pollutants that constitute 
the BART-eligible source.
    In this section of the preamble, we discuss some of the comments we 
received on the steps in this process, and any changes we are making in 
light of those comments.
Step 1: Identify the Emission Units in the BART Categories
    The BART guidelines list the 26 source categories that the CAA uses 
to describe the types of stationary sources that are BART-eligible. 
Both proposals clarified the descriptions of particular source 
categories.
    Comments. The final rule addresses comments on the following source 
categories. Some comments discussed below were submitted in response to 
the 2001 propoosal and were not addressed in the reproposal; other 
comments were submitted in response to the reproposal in 2004.
    (1) ``Charcoal production facilities.'' We received comments in 
2001 from two industry trade groups requesting that the final 
guidelines explicitly exclude ``low-emission'' charcoal production 
facilities from BART. These comments cited a 1975 study considered by 
Congress in development of the BART category list in the 1977 CAA 
amendments. This 1975 study noted that some charcoal production 
facilities have much higher emissions factors (i.e., 352 pounds of PM 
per ton of charcoal produced versus 20 to 25 pounds of PM per ton of 
charcoal produced). Accordingly, the comments asserted that the intent 
of Congress in the 1977 CAA amendments was to provide incentives for 
higher-emitting facilities to reduce their emissions, rather than to 
make the entire category BART-eligible.
    (2) ``Chemical process plants.'' In 2001 a trade group representing 
the pharmaceutical industry requested that we determine in the 
guidelines that the term ``chemical process plants'' does not include 
pharmaceutical plants.
    (3) ``Primary aluminum ore reduction.'' Comments from the aluminum 
industry in 2001 noted that not all emissions units at these facilities 
are necessarily involved in ``primary ore reduction.'' Thus, the 
comments recommended that we clarify that contiguous sources that are 
not related to primary aluminum ore reduction, such as fabricating 
facilities and ingot operations, are not BART-eligible. Further, the 
comments recommended that we use definitions in the NSPS for primary 
aluminum plants to describe the BART-eligible emissions units.
    (4) ``Fossil-fuel fired steam electric plants of more than 250 
million Btu/hour heat input.'' The 2004 reproposal contained the 
clarification, requested by commenters, that this source category 
refers only to those fossil-fuel fired steam electric plants that 
generate electricity for sale. One commenter objected to this 
clarification on the basis that emissions from co-generators would be 
excluded; many other commenters supported the clarification. Another 
commenter requested that we also clarify that this category includes 
only those steam electric plants that burn greater than 50 percent 
fossil fuel, in order to be consistent with the definition of fossil-
fuel boilers proposed in the guidelines. Other commenters requested 
that we clarify whether the definition includes units which are located 
at a steam electric plant, but which themselves are not in any of the 
26 BART source categories, such as simple cycle turbines, emergency 
diesel engines, and reciprocating internal combustion engines (RICE).
    Several commenters opined that the category should exclude combined 
cycle units with heat recovery steam generators that lack auxiliary 
firing, arguing that these units should count as simple cycle turbines. 
These commenters pointed to other EPA regulatory programs that treat 
combined cycle units with supplemental firing differently from combined 
cycle units without supplemental firing. They argued that we should 
only consider a combined cycle unit to be a ``steam electric plant'' if 
it has supplemental firing.
    (5) ``Fossil-fuel boilers of more than 250 million Btu/hour heat 
input.'' The 2004 reproposal clarified that this category should be 
read as including only those boilers individually greater than 250 
million Btu/hour heat input. We received many comments on this 
interpretation, both in favor and opposed. Those favoring this 
interpretation (generally industry commenters) cited the implementation 
burden that including smaller boilers would pose, the high cost-
effectiveness of controlling smaller boilers, and the relatively 
smaller impact on regional haze that smaller boilers would pose. They 
also noted that this interpretation is most consistent with definitions 
in the NOX SIP call and new source performance standards 
(NSPS).
    Commenters opposing this interpretation (environmental groups, one 
state, and one regional planning organization) noted that regarding all 
boilers, irrespective of size, as BART-eligible so long as the 
aggregate heat input exceeds 250 million Btu/hour is more consistent 
with the definition of stationary source under the Prevention of 
Significant Deterioration (PSD) program. These commenters noted that 
under the CAA, BART and PSD are complementary programs aimed at 
regulating the same source categories; either one or the other applies 
depending upon when the source was constructed.
    The 2004 reproposal also clarified that if a boiler smaller than 
250 million Btu/hour heat input is an integral part of an industrial 
process in a BART source category other than electric utilities, then 
the boiler should be considered part of the BART-eligible source in 
that category. Under these circumstances, the boiler, as part of the 
BART-eligible source, should be considered for emission control. Some 
commenters opposed this interpretation, asserting that it would result 
in an ``arbitrary and capricious'' inconsistency, in that some smaller 
boilers would be BART-eligible, and others would not. These commenters 
also noted that these boilers could be included in regional haze SIPs 
as necessary for making ``reasonable progress'' toward CAA visibility 
goals, even if they are not considered to be BART-eligible.
    Final rule. After considering the comments, we have made the 
following determinations on the definitions of the following source 
categories:
    (1) ``Charcoal production facilities.'' We believe that in using 
the term ``charcoal production facilities'' Congress intended to 
encompass all types of charcoal production facilities. We do not agree 
with comments that any inferences can necessarily be made regarding the 
presence of different PM emission factors for different types of 
charcoal production facilities in the 1975 report. For example, if 
Congress only intended to regulate a subset of the charcoal production 
industry, then we believe Congress could have easily indicated this in 
the source category title, as was done for ``kraft pulp mills'' and for 
``coal cleaning plants (thermal dryers).'' We also note that it is more 
likely that plants in the charcoal production industry with lower 
emission factors have emissions that are less than the 250 tons per 
year cutoff for BART eligibility.
    (2) ``Chemical process plants.'' We believe that there is a clear 
precedent to include pharmaceutical manufacturing operations as 
``chemical process plants.'' In the standard industrial classification 
(SIC) system, pharmaceutical operations are generally

[[Page 39110]]

in SIC codes 2833 and 2834, which are a subset of 2-digit category 28 
``Chemical and Allied products.'' Similarly, in the new North American 
Industrial Classification Codes (NAICS), pharmaceutical manufacturing 
is codes 32541 and 32542, which is a subset of the ``chemical 
manufacturing subsector'' which is code 325. Accordingly, in the PSD 
program, pharmaceutical plants have been treated as ``chemical process 
plants.'' The commenter is correct in noting that EPA has consistently 
distinguished between chemical manufacturing and pharmaceutical 
manufacturing. Examples where different standards or guidelines are 
established included control technique guideline (CTG) documents, NSPS 
standards under section 111 of the CAA, and, most recently, maximum 
achievable control technology (MACT) standards under section 112 of the 
CAA. We do not agree that these differentiations for emissions 
standards necessarily require differentiation for purposes of 
determining BART eligibility. Therefore we believe pharmaceuticals 
should not be excluded from BART. However, we expect that because of 
the MACT standards, there is a very low probability that BART 
determinations will lead to further control requirements from chemical 
production processes at pharmaceutical plants.
    (3) ``Primary aluminum ore reduction.'' We agree with commenters 
that BART-eligible units in this source category should be defined 
consistently with the NSPS definition for primary aluminum ore 
reduction. Therefore we have added a clarification to that effect in 
the final BART guidelines. We note that this definition is also 
consistent with the definition at 40 CFR 63.840, which establishes 
applicability for this source category for the MACT program.
    (4) ``Fossil-fuel fired steam electric plants of more than 250 
million Btu/hour heat input.'' We have retained the clarification that 
this source category refers only to those fossil-fuel fired steam 
electric plants that generate electricity for sale. We believe that 
this clarification helps to distinguish those plants that are electric 
utilities from plants in other industrial categories. We also believe 
that while large co-generators would be excluded from the fossil-fuel 
fired steam electric plant source category, most large co-generators 
will be BART-eligible under the fossil-fuel fired boilers source 
category.
    We do not believe it makes sense for this category to include only 
those steam electric plants that burn greater than 50 percent fossil 
fuel. We do not believe that a boiler should be excluded from BART 
review simply because it is located at a plant which burns less than 50 
percent fossil fuel. Emissions from any such boiler could be a 
significant contributor to regional haze, and as such, we believe that 
each fossil-fuel fired boiler merits a BART review.
    We do wish to clarify that units which are located at a steam 
electric plant, but which themselves are not in any of the 26 BART 
source categories, should not be considered to be BART-eligible units. 
We believe that Congress intended that BART review be focused on units 
in the source categories it delineated. This interepretation is most 
consistent with the definition of BART-eligible source as we have 
explained it elsewhere in this preamble in reference to whether entire 
plants are included if only some units at the plant meet the statutory 
criteria.
    Finally, we believe that all combined cycle units are included in 
the definition of fossil fuel fired steam electric plant, regardless of 
whether the combined cycle unit's heat recovery steam generator lacks 
auxilliary firing. Commenters are correct that some EPA programs have 
treated combined cycle units with supplemental firing differently from 
combined cycle units without supplemental firing. However, while some 
EPA programs do not consider a unit to be a combined cycle unit unless 
it contains supplemental firing, the definition at issue here is the 
definition of fossil-fuel fired steam electric plant, not fossil-fuel 
fired unit. The CAA defines both ``stationary source'' (for visibility 
purposes) and ``major emitting facility'' (for PSD purposes) to include 
``fossil fuel fired steam electric plants.'' In previous guidance for 
PSD, we have explained that combined cycle gas turbines do fall within 
the category of ``fossil-fuel fired steam electric plants.'' \8\
---------------------------------------------------------------------------

    \8\ See http://www.epa.gov/Region7/programs/artrd/air/nsr/nsrmemos/turbines.pdf.
---------------------------------------------------------------------------

    (5) ``Fossil-fuel boilers of more than 250 million Btu/hour heat 
input.'' We have decided to retain the interpretation that this 
category should be read as including only those boilers individually 
greater than 250 million Btu/hour heat input. We agree with commenters 
who noted that including smaller boilers would pose considerable 
implementation burden. As noted in the 2004 reproposal notice, we do 
not believe that this interpretation is likely to have a substantial 
impact. Because smaller boilers are generally less cost-effective to 
control, we believe that BART review would be unlikely to result in a 
significant amount of control on these boilers.
    We are also retaining the clarification that if a boiler smaller 
than 250 million Btu/hour heat input is an integral part of an 
industrial process in a BART source category other than electric 
utilities, then the boiler should be considered part of the BART-
eligible source in that category. (By ``integral to the process'', we 
mean that the process uses any by-product of the boiler, or vice-versa. 
We have added this clarification to the definition in the BART 
guidelines.) We believe that if a State is already considering a BART-
eligible industrial process for control, and a boiler is integrated 
into that process, it makes common sense not to prematurely rule out 
control options any of the emissions from that process as a whole. 
(Note that a boiler which is not integral, but is simply attached to a 
plant, should not be included.) For example, Kraft pulp mills may have 
boilers that are not serving the energy infrastructure of the plant but 
typically are serving a process directly by using the waste liquor from 
the process. Including such a boiler in consideration of control 
options for the process adds minimal additional burden while leaving 
maximum discretion to the State in determining BART for the process as 
a whole.
    We are also clarifying today that we have determined that this 
category should include all individual boilers of greater than 250 
million Btu/hour heat input burning any amount of fossil fuel, as 
opposed to only those boilers that burn greater than 50 percent fossil 
fuel. We believe that it is quite possible that boilers of this size 
could contribute to regional haze in a Class I area even if they burn 
less than 50 percent fossil fuel. Therefore we believe that each fossil 
fuel-fired boiler merits a BART review.
Step 2: Identify the Start-up Dates of Those Emission Units
    Background. BART applies only to a major stationary source which 
``was in existence on August 7, 1977 but which has not been in 
operation for more than fifteen years as of such date.'' The visibility 
regulations define ``in existence'' and ``in operation'' in 40 CFR 
51.301. Under these regulations, promulgated in 1980, ``in existence'' 
means

that the owner or operator has obtained all necessary 
preconstruction approvals or permits * * * and either has (1) begun, 
or caused to begin, a continuous program of physical on-site 
construction of the facility or (2) entered into binding agreements 
or contractual obligations.


[[Page 39111]]


The term ``in operation'' means engaged in activity related to the 
primary design function of the source.
    Step 2 also addresses the treatment of ``reconstructions'' and 
``modifications.'' Under the definition of BART-eligible facility, 
sources which were in operation before 1962 but reconstructed during 
the 1962 to 1977 time period are treated as new sources as of the time 
of reconstruction.\9\ The same policies and procedures for identifying 
reconstructed ``affected facilities'' under the NSPS are used to 
determine whether a source has been reconstructed for purposes of the 
BART requirements. ``Modifications'' under the CAA refers to physical 
change or change in the method of operation at a source which has led 
to an increase in emissions. In the proposed BART guidelines, we stated 
that the best interpretation of the visibility provisions is that a 
modification to a source does not change an emission's unit 
construction date for purposes of BART applicability. We requested 
comment on an alternative interpretation that we believed would be more 
difficult to implement. Under this approach, sources built before 1962 
but modified during the 1962 to 1977 time frame would be considered 
``new'' at the time of modification.
---------------------------------------------------------------------------

    \9\ However, sources reconstructed after 1977, which 
reconstruction had gone through NSR/PSD permitting, are not BART-
eligible.
---------------------------------------------------------------------------

    Comments. We received comments in 2001 and 2004 on the discussion 
in the guideline of the term ``in existence.'' These comments were 
critical of our statement in the guidelines that sources which had 
``commenced construction,'' that is, those which had entered into 
binding contracts, would be considered to be in existence, even if 
actual operations did not begin until after the August 7, 1977 cutoff 
date. These commenters asserted that Congress did not intend to treat a 
source as ``existing'' in 1977 if it was not yet built.
    Other commenters interpreted the proposed guidelines as expanding 
the definition of BART-eligible sources by requiring States to find 
that all emission units at a facility are BART-eligible if one part of 
the facility was built within the 1962-1977 time period. Other comments 
did not suggest that we had already expanded the definition in the 
proposed guidelines, but did suggest that we should expand the 
definition in that way in the final guidelines. Some commenters noted 
that there was a degree of confusion in the regulated community on 
whether the proposed guidelines were requiring BART for all units at a 
power plant, including those that were in operation before August 7, 
1962, if these units are co-located with one or more units that were 
put in place within the 1962-1977 time period. These commenters 
requested that we clarify that such pre-1962 units would not be BART-
eligible.
    Some commenters asserted that our proposed approach is unworkable, 
because the approach requires States to identify all emissions units 
put in place between the 1962 and 1977. Some of these commenters 
asserted that Congress intended that BART would apply only if entire 
plants satisfy the statutory criteria. These comments suggested that 
BART should apply only if an entire plant that is one of the 26 listed 
source category types had been placed in operation at a discrete point 
within the 15 year time period for BART eligibility. These commenters 
asserted that our proposed guidelines, which involved the 
identification and aggregation of individual emission units within the 
1962-1977 time period, were inconsistent with Congress' intent. Other 
comments suggested that EPA could improve implementation of the program 
by covering discrete projects rather than individual emissions units. A 
few commenters suggested that for purposes of identifying such discrete 
projects, we consider using the term ``process or production unit'' 
that we used in hazardous air pollutant regulations under CAA section 
112(g).
    One commenter requested that the guidelines clarify that emissions 
from ``linked'' emission units should not be considered in determining 
BART eligibility. That is, even if changes in emissions from one unit 
could affect the emissions from a ``linked'' unit that was not put in 
place within the 1962-1977 time period, that would not affect whether 
the ``linked'' unit was BART-eligible. Another commenter suggested that 
the approach set forth in the guidelines for identifying BART-eligible 
sources is inappropriate because the particular set of units identified 
as BART-eligible will not necessarily ``provide a reasonable and 
logical platform for the installation of controls.''
    Other commenters stated that facilities that had been modified 
after 1977 should not be included in the pool of sources subject to 
BART. Such facilities, it was argued, already meet the BART 
requirements because of the controls installed to meet the requirements 
of PSD, NSR, or the NSPS.
    Final rule. We disagree with the comments recommending that we 
interpret the term ``in existence'' to refer to sources that are in 
actual operation. The discussion of this term in Step 2 is based on the 
regulatory definition which has been in place since 1980. The 
guidelines reiterate this definition and provide examples of its 
application. Interpreting the term ``in existence'' as suggested by 
commenters would not be consistent with the plain language of the 
regulations.
    In the 2001 and 2004 proposed guidelines, we noted that ``the term 
`in existence' means the same thing as the term `commence construction' 
as that term is used in the PSD regulations.'' Commenters were critical 
of this statement, claiming that EPA was unlawfully reinterpreting 
section 169A in the guidelines. The statement in Step 2 of guidelines, 
however, is not a reinterpretation of the term ``in existence,'' but 
merely a statement noting that the definitions used in the visibility 
regulations and the PSD regulations are essentially identical.
    To the extent that commenters are claiming that the existing 
regulatory definition of ``in existence'' is unlawful, EPA's 
interpretation of this term in promulgating the 1980 regulations was a 
reasonable one. First, it is worth noting that the regulations adopting 
this interpretation of the term ``in existence'' were in effect in 1990 
and implicitly endorsed by Congress in its 1990 amendments to the 
CAA.\10\ Moreover, the definition at issue accurately reflects 
Congress' intent that the BART provision apply to sources which had 
been ``grandfathered'' from the new source review permit requirements 
in parts C and D of title I of the CAA. For all the above reasons, we 
are neither revising the regional haze regulations to change the 
definition of ``in existence,'' nor adopting a strained interpretation 
of the regulation in the guidelines.
---------------------------------------------------------------------------

    \10\ See CAA section 193.
---------------------------------------------------------------------------

    We agree with commenters that the definition of ``BART-eligible 
source'' does not require States to find that all emission units at a 
facility are subject to the requirement of the BART provisions if only 
one part of the facility was built within the 1962-1977 time period. We 
received comments on this issue in 2001 and clarified in 2004 that the 
BART guidelines do not direct States to find that all boilers at a 
facility are BART-eligible if one or more boilers at the facility were 
put in place during the relevant time period. Under Step 2 of the 
process for identifying BART-eligible sources set out in the 
guidelines, States are required to identify only those boilers that 
were put in place between 1962 and 1977. As explained in the preamble 
to the 2004 reproposed guidelines, only these boilers are potentially 
subject to BART.

[[Page 39112]]

    We do not agree with those commenters claiming that Congress 
clearly intended to apply BART only if an ``entire plant'' was put into 
place between 1962 and 1977. Most of the BART source categories are 
broad descriptions types of industrial facilities such as ``kraft pulp 
mills,'' ``petroleum refineries'' or ``primary copper smelters.'' For 
such source categories, the implication of commenters' argument would 
that if any portion of the plant was in operation before August 7, 
1962, then Congress intended to exempt the entire plant from BART. Such 
an interpretation is problematic and inequitable. For example, under 
this approach BART would not apply if a company chose to expand its 
production by building a second production line at an existing line in 
1965, but would apply if the same company chose to build the same 
equipment at a greenfield site. Under the approach set forth in the 
guidelines, such a production line would be treated similarly under 
either set of facts. We do not believe that either the plain language 
of the statute or the relevant legislative history indicate that 
Congress intended for major-emitting sources of visibility-impairing 
pollutants to be exempted from the BART requirements because a plant 
contains some emission units that began operation before 1962.
    Also, we disagree with the comment that modifications after 1977 
should change an emissions' unit date of construction for purposes of 
BART applicability. The commenter's suggestion that such sources 
already meet BART requirements may be accurate, but does not provide a 
basis for exempting the source from review. As we note in the 
guideline, the review process will take into account the controls 
already in place and the State may find that these controls are 
consistent with BART.
    We agree with the comments related to ``linked'' emission units. 
The comment appears to address whether emissions from the ``linked'' 
units are considered in determining BART eligibility. In the 
guidelines, we are focusing on only the emissions units that were put 
in place during the 1962 to 1977 dates and the emissions from those 
units. We agree that even if changes in emissions from one unit could 
affect the emissions from a ``linked'' unit that was not put in place 
within the 1962-1977 time period, this would not affect whether the 
``linked'' unit was BART-eligible.
    We disagree with commenters that the approach set forth in the 
guidelines for identifying BART-eligible sources is inappropriate 
because the particular set of units identified as BART-eligible will 
not necessarily ``provide a reasonable and logical platform for the 
installation of controls.'' We do not agree that this factor is 
relevant to the identification of those emissions units which meet the 
definition of BART-eligible source. Such factors are important in the 
States' consideration of control strategies and options but do not 
clearly relate to the first step of identifying those sources which 
fall within one of 26 source categories, were built during the 15 year 
window of time from 1962 to 1977, and have potential emissions of 
greater than 250 tons per year. We do thus agree generally with the 
commenter's recommendation of allowing States to consider the 
particular history and control potential of units in determining BART, 
but do not agree that it is relevant to the predicate question of 
identifying the BART-eligible source.
    Finally, the approach to identifying a ``BART-eligible source'' in 
the guidelines is based on the definitions in the regional haze rule of 
the relevant terms. For 750 MW power plants, States are required to 
apply the definitions as set forth in the guidelines; for other 
sources, States may adopt a different approach to the task of 
identifying BART-eligible sources, so long as that approach is 
consistent with the Act and the implementing regulations. In other 
words, while the guidelines adopt an approach for large power plants 
which involves the aggregation of all emissions units put into place 
between 1962 and 1977, States have the flexibility to consider other 
reasonable approaches to the question of identifying BART-eligible 
sources for other source categories.
    For 750 MW power plants, many of the issues identified by 
commenters with the approach of looking at a facility on an emission 
unit by emission unit basis do not exist. Unlike many types of 
industrial processes, power plants consist generally of a discrete 
number of very large emission units. For other types of facilities such 
as kraft pulp mills or chemical process plants which may have many 
small emission units that have undergone numerous changes, the 
guidelines do not limit the ability of the States to approach the 
question of identifying BART-eligible sources in ways which make sense 
for the particular sources given their design and history.
Step 3: Compare the Potential Emissions to the 250 Ton/Yr Cutoff.
    Background. Step 3 of the guidelines addresses the question of 
whether the units identified in Steps 1 and 2 have emissions in excess 
of the threshold for major sources set forth in section 169A(g)(7) of 
the CAA. The guidelines pose the following questions to help the States 
in determining whether the relevant emissions units have the potential 
to emit in excess of the 250 tons per year threshold of any single 
visibility-impairing pollutant:
    (1) What pollutants should I address?
    The 2001 proposed guidelines included the following list of 
visibility-impairing pollutants: SO2, NOX, 
particulate matter, volatile organic compounds (VOCs), and ammonia. We 
proposed in 2001 and again in 2004 that States use PM10 as 
the indicator for particulate matter. As explained in the guidelines, 
there is no need to have separate 250 ton thresholds for 
PM10 and PM2.5 because emissions of 
PM10 include the components of PM2.5 as a subset. 
In addition, because of various uncertainties associated with 
regulating VOCs and ammonia, we requested comment in 2004 on the level 
of discretion States should exercise in making BART determinations for 
VOCs and took ammonia off the list of visibility-impairing pollutants.
    In both proposals, we clarified that the 250 tons per year cutoff 
applies to emissions on a pollutant by pollutant basis. In other words, 
a source is subject to BART only if it emits at least 250 tons per year 
of an individual visibility-impairing pollutant.
    (2) What does the term ``potential'' emissions mean?
    The proposed guidelines in 2001 and the reproposed guidelines in 
2004 excerpt the definition of ``potential to emit'' from the 
regulations at 40 CFR 51.301. As the definition makes clear, the 
potential to emit of a source is calculated based on its capacity to 
emit a pollutant taking into account its physical and operational 
design. Under this definition, federally enforceable emission limits 
may be taken into account in calculating a source's potential 
emissions; however, emission limitations which are enforceable only by 
State and local agencies, but not by EPA and citizens in Federal court, 
cannot be used to limit a source's potential to emit for purposes of 
the regional haze program.
    (3) What is a ``stationary source?'
    As explained above, States are required to make a BART 
determination only for ``stationary sources'' of a certain size that 
fall within one of 26 types of industrial categories listed in the 
statute and that were built within a certain time frame. The regional 
haze rule contains definitions that are relevant to the determination 
of the emissions units that comprise a ``stationary source.'' First, 
the regulations at 40 CFR 51.301

[[Page 39113]]

define ``stationary source'' as ``any building, structure, facility, or 
installation which emits or may emit any air pollutant.'' Second, the 
terms ``building, structure, or facility'' are defined in part based on 
grouping pollutant-emitting activities by industrial category:

    Building, structure, or facility means all of the pollutant-
emitting activities which belong to the same industrial grouping, 
are located on one or more contiguous or adjacent properties, and 
are under the control of the same person (or persons under common 
control). Pollutant-emitting activities must be considered as part 
of the same industrial grouping if they belong to the same Major 
Group (i.e., which have the same two-digit code) as described in the 
Standard Industrial Classification Manual, 1972 as amended by the 
1977 Supplement (U.S. Government Printing Office stock numbers 4101-
0066 and 003-005-00176-0 respectively).

    In the 2001 proposed guideline, we noted that support facilities, 
i.e. facilities used to convey, store, or otherwise assist in the 
production of the principal product, are considered to fall within the 
same industrial grouping as the primary facility. To clarify this, in 
2004 we proposed to add language to the guideline noting that emission 
units at a plant, even if they are a ``support facility'' for purposes 
of other programs, would not be subject to BART unless they were within 
one of the 26 listed source categories and were built within the 1962 
to 1977 time frame.
Discussion of ``What Pollutants Should I Address?''
    Comments. PM10 as an indicator. Some comments questioned 
the use of PM10 (which includes both coarse and fine 
particulate matter) as the indicator for particulate matter. Commenters 
noted that the coarse fraction, that is particulate matter between 10 
and 2.5 micrograms in diameter, fundamentally differs compared to the 
fine mass in how it interacts with light. Commenters suggested that 
only the fine mass (PM2.5) component of particulate matter 
is likely to contribute to visibility impairment. Accordingly, these 
commenters recommended that the 250 ton cutoff for particulate matter 
should be based upon emissions of PM2.5.
    Ammonia. Many commenters addressed the exclusion of ammonia from 
the list of visibility-impairing pollutants. A number of commenters, 
primarily from industry but also from one state and one regional 
planning organization, supported the exclusion of ammonia. These 
commenters generally cited the complexity and variability of ammonia's 
role in the formation of PM2.5 in the atmosphere, the 
relative greater benefits of controlling NOX and 
SO2, the uncertainties in the inventory of ammonia 
emissions, and the inherent complexities of gauging the contribution of 
potential ammonia reductions to improving visibility in Class I areas. 
In addition, commenters noted that few, if any, point sources emit 
ammonia in amounts that exceed the 250 ton per year threshold.
    Other commenters, including a number of environmental groups and 
several states, regional planning organizations, and industry 
commenters, argued that ammonia should be included in the list of 
visibility-impairing pollutants in the guidelines. In support of this 
view, commenters cited evidence that ammonia is a known precursor to 
PM2.5. One commenter noted that improvements are being made 
to ammonia inventories and to the understanding of ammonia's role in 
the formation of haze. Other commenters pointed to a National Park 
Service (NPS) analysis of monitoring data that indicates that 
visibility-impairment due to nitrate aerosol formation (to which 
ammonia contributes) is of significant concern \11\ and to a 2003 
direction to policy-makers from the North American Research Strategy 
for Tropospheric Ozone (NARSTO) \12\ indicating that consideration of 
control strategies needs to include ammonia in combination with other 
precursors to particle formation. Many commenters also argued that EPA 
should encourage or allow the States to consider ammonia in their 
visibility protection plans, and noted that ammonia reductions could be 
a cost-effective way to improve visibility under certain conditions.
---------------------------------------------------------------------------

    \11\ See http://wrapair.org/forums/ioc/meetings/030728/index.html (specifically presentation by John Vimont, National Park 
Service).
    \12\ NARSTO, Particulate Matter Assessment for Policy Makers: A 
NARSTO Assessment. P. McMurry, M. Shepherd, and J. Vickery, eds. 
Cambridge University Press, Cambridge, England (2004).
---------------------------------------------------------------------------

    Volatile Organic Compounds (VOCs). Several commenters responded to 
our request for comments on whether States should treat VOCs in urban 
areas differently from VOCs in rural areas. Environmental groups and a 
few States argued that the current state of scientific knowledge does 
not support a differentiation between urban and rural sources of VOCs. 
One environmental commenter cited evidence that organic aerosols are a 
major constituent of visibility-reducing aerosols and that VOCs are 
important precursors to the formation of secondary organic aerosols. 
One commenter also stated that VOCs may play a particularly significant 
role in particle formation in those rural areas with significant nearby 
sources of NOX. Commenters also cited evidence that the 
contribution of VOC to particle formation likely varies widely in 
different areas of the country, and argued that States should retain 
flexibility to address local VOC sources if they determine that those 
sources are contributors of concern.
    Several industry commenters stated that more focus should be placed 
on controlling VOCs in urban rather than rural areas. A few commenters 
from industry argued that VOCs in rural areas have not been shown to be 
a significant contributor to particle formation, and should be excluded 
from the list of pollutants to be addressed in the BART process. One 
argued that VOCs should be excluded from BART entirely based upon 
uncertainties in the current state of knowledge, and a few argued that 
VOCs from both power plants and rural sources should be excluded from 
BART, based on low emissions and the cost of controls. One regional 
planning organization requested that EPA clarify the definitions of 
``urban'' and ``rural'' areas.
    Final rule. PM10 as an indicator. While it is always 
necessary to assess PM2.5 impacts, we agree with commenters 
who stated that the coarse fraction is less efficient at light 
scattering than fine particles, there is ample evidence that the coarse 
fraction does contribute to visibility impairment.\13\ For example, 
standard methods for calculating reconstructed light extinction 
routinely include a calculation for the contribution to light 
extinction from the coarse fraction, an implicit recognition that these 
particles contribute measurably to visibility impairment.\14\ We do 
recognize that coarse PM is likely to contribute more to regional haze 
in arid areas than humid areas. We believe that, as the Grand Canyon 
Visibility Transport Commission (GCTVC) recognized,\15\ States in the 
arid West in particular should take the coarse fraction of particulate 
matter into account in determining whether a source meets the threshold 
for BART applicability.
---------------------------------------------------------------------------

    \13\ See Fine particles: Overview of Atmospheric Chemistry, 
Sources of Emissions, and Ambient Monitoring Data, Memorandum to 
Docket OAR 2002-0076, April 1, 2005.
    \14\ These methods are described at the following Web site: 
http://vista.cira.colostate.edu/improve/Tools/ReconBext/reconBext.htm.
    \15\ Grand Canyon Visibility Transport Commission, 
Recommendations for Improving Western Vistas, Report to the U.S. 
EPA, June 10, 1996.
---------------------------------------------------------------------------

    Because long-range transport of fine particles is of particular 
concern in the formation of regional haze, we also

[[Page 39114]]

believe that it is very important to estimate the PM2.5 
fraction of direct particulate emissions as correctly as possible. In 
addition, we believe that air quality modeling results will be more 
meaningful provide a more accurate prediction of a source's impact on 
visibility if the inputs account for the relative particle size of 
directly emitted particulate matter (e.g. PM10 vs. 
PM2.5).
    States should consider whether their current test methods for 
measuring particulate matter emissions from stationary sources account 
for the condensible fraction of particulate matter and consider 
revising any such stationary source test methods to account for the 
condensible fraction of particulate emissions. See the source testing 
technical support document (TSD) in the docket for this rule, which 
discusses test methods for particulate matter in more detail.\16\
---------------------------------------------------------------------------

    \16\ Fine particles: Overview of Source Testing Approaches, 
Memorandum to Docket OAR 2002-0076, April 1, 2005.
---------------------------------------------------------------------------

    Ammonia. In regard to ammonia, we believe there is sufficient 
uncertainty about emission inventories and about the potential efficacy 
of control measures from location to location such that the most 
appropriate approach for States to take is a case-by-case approach. 
There are scientific data illustrating that ammonia in the atmosphere 
can be a precursor to the formation of particles such as ammonium 
sulfate and ammonium nitrate; \17\ however, it is less clear whether a 
reduction in ammonia emissions in a given location would result in a 
reduction in particles in the atmosphere and a concomitant improvement 
in visibility. In other words, the question of whether ammonia 
contribute to visibility impairment in a specific instance can be a 
difficult one.
---------------------------------------------------------------------------

    \17\ See Fine particles: Overview of Atmospheric Chemistry, 
Sources of Emissions, and Ambient Monitoring Data, Memorandum to 
Docket OAR 2002-0076, April 1, 2005.
---------------------------------------------------------------------------

    It may be that States will not be faced often with the question of 
addressing ammonia in making BART determinations. As noted above, 
States are required to make BART determinations only for stationary 
sources that fall within certain industrial categories. The types of 
sources subject to the BART provisions are not typically significant 
emitters of ammonia. Because of this, it is unlikely that including 
ammonia on the list of visibility-impairing pollutants in the BART 
guidelines would have much impact on the States' determinations of 
whether a source is BART-eligible. Thus, while ammonia can contribute 
to visibility impairment, we believe the decision whether to consider 
ammonia as a visibility-impairing pollutant in a specific case where a 
potential BART source actually emits more than 250 tons per year of 
ammonia is best left to the State.
    VOCs. Organic compounds can be categorized according to their 
varying degrees of volatility: highly reactive, volatile compounds with 
six or fewer carbon atoms which indirectly contribute to PM formation 
through the formation of oxidizing compounds such as the hydroxyl 
radical and ozone; semivolatile compounds with between seven and 24 
carbon atoms which can exist in particle form and can readily be 
oxidized to form other low volatility compounds; and high molecular 
weight organic compounds--those with 25 carbon atoms or more and low 
vapor pressure--which are emitted directly as primary organic particles 
and exist primarily in the condensed phase at ambient temperatures. The 
latter organic compounds are considered to be primary PM2.5 
emissions and not VOCs for BART purposes.
    Current scientific and technical information shows that 
carbonaceous material is a significant fraction of total 
PM2.5 mass in most areas and that certain aromatic VOC 
emissions such as toluene, xylene, and trimethyl-benzene are precursors 
to the formation of secondary organic aerosol.\18\ However, while 
progress has been made in understanding the role of VOCs in the 
formation of organic PM, this relationship remains complex, and issues 
such as the relative importance of biogenic versus anthropogenic 
emissions remain unresolved.
---------------------------------------------------------------------------

    \18\ Ibid.
---------------------------------------------------------------------------

    Therefore we believe that the best approach for States to follow in 
considering whether VOC emissions are precursors to PM2.5 
formation is a case-by-case approach. States should consider, in 
particular, whether a source's VOC emissions are those higher-carbon 
VOCs that are more likely to form secondary organic aerosols. In 
addition, given the variable contribution of a given amount of VOC 
emissions to PM2.5 formation, States may also wish to 
exercise discretion in considering only relatively larger VOC sources 
to be BART-eligible.
    After careful consideration of the comments, we agree with 
commenters who assert that EPA should not suggest a general distinction 
between the relative contributions of urban and rural VOC emissions to 
particle formation. The state of knowledge in this area is complex and 
rapidly evolving. Monitoring data in the East \19\ suggest that there 
may be a greater contribution to particle formation in urban areas from 
VOCs as compared to rural areas, but we recognize that further research 
is needed to better determine the extent of the contribution of 
specific VOC compounds to organic PM mass. We do not agree, however, 
with commenters who make the blanket assertion that rural VOCs are not 
a significant contributor to particle formation, as it is possible that 
in specific areas, such as where NOX emissions are high, 
rural anthropogenic VOCs could potentially play a significant role.
---------------------------------------------------------------------------

    \19\ Ibid.
---------------------------------------------------------------------------

Discussion of the Term ``Potential'' Emissions
    Comments. A number of commenters were critical of the restriction 
in the regional haze rule that allows States to credit federally 
enforceable limitations on emissions but not limitations that are 
enforceable only by States and local agencies. These commenters 
believed that this restriction had been rejected by the D.C. Circuit 
for a number of other EPA regulations and noted that EPA has developed 
policies that currently credit state-enforceable limits. The comments 
recommended that EPA issue guidance consistent with what commenters 
claimed were current policies for other regulations. In addition, we 
received comments arguing that in determining whether a source is a 
major stationary source, the States should consider a source's actual--
rather than potential--emissions. These commenters stated that using a 
source's potential emissions overstates a source's actual emissions and 
impacts on visibility.
    Final rule. CAA section 169A(g)(7) defines a ``major stationary 
source'' as a source with the potential to emit 250 tons or more any 
pollutant. Based inter alia on that statutory definition, EPA's 
implementing regulations define BART-eligible sources as those with the 
potential to emit 250 tons or more of any air pollutant. As these 
definitions clearly require consideration of a source's potential 
emissions, the guidelines state that a State should determine whether a 
source's potential emissions exceed the 250 ton threshold in 
determining whether the source is BART-eligible.
    As explained in the 2001 and 2004 proposed guidelines, the regional 
haze regulations define ``potential to emit.'' The guidelines repeat 
that regulatory definition and provide an example illustrating its 
application. EPA did not propose to change the definition in 2001 or 
2004, but merely highlighted the

[[Page 39115]]

current definition in 40 CFR 51.301. Although we noted in the 2001 
proposed guidelines that we expected to undertake a rulemaking to 
determine whether only federally enforceable limitations should be 
taken into account in the regional haze program definition, we have not 
yet begun the process for such a rulemaking. However, we consider the 
comments criticizing EPA's definition of ``potential to emit'' as a 
request for reconsideration of the visibility regulations and will take 
these requests into account in determining any future rulemaking 
efforts to address the general definition of ``potential to emit.'' For 
the time being, we believe that States may consider federally 
enforceable limits or emissions limitations in State permits, which are 
enforceable under State law, in determining a source's ``potential to 
emit.''
Discussion of What Emissions Units Should Be Considered Part of a 
``Stationary Source''
    Comments. A number of comments in 2001 expressed concern with our 
statement that a ``support facility'' should be grouped with a primary 
facility in determining which emissions units belong to the same 
industrial grouping. These comments generally coincided with comments 
discussed above that EPA should determine BART on a plantwide basis, 
rather than by aggregating emissions units. Commenters on the 2004 
reproposal noted with approval the clarification that ``support 
facilities'' should only be considered BART-eligible if these units 
themselves were both constructed within the 1962-1977 time frame and 
fell within one of the listed source categories.
    Two commenters felt that we should more clearly define the BART-
eligible source, either by identifying emission units within source 
categories, or by somehow accounting for the specific set of emission 
units, within the fenceline, to which controls would logically apply.
    Final rule. The guidelines continue to note that the definition of 
``building, structure or facility'' in the regional haze rule is based 
upon aggregating emissions units within the same industrial grouping. 
This discussion in the guidelines is consistent with the language in 
the definition of ``building, structure or facility'' in the regional 
haze rule which contains a specific reference to the 2-digit SIC 
classifications. The BART guidelines refer to this definition and 
explain how 2-digit SIC codes are used in determining the scope of BART 
for a given plantsite. (In the rare situation where industrial 
groupings in separate 2-digit SIC codes exist at a single plant site, 
then there would be more than one separate ``stationary source'' 
present. In that situation, each ``stationary source'' should be looked 
at individually for purposes of determining BART-eligibility.)
    We agree that more clarity is needed to account for situations 
where a specific set of units constitute the logical set to which BART 
controls would apply. The CAA requires BART at certain major stationary 
sources. Accordingly we believe it could be appropriate, at the BART 
determination step, for States to allow sources to ``average'' 
emissions across a set of BART-eligible emission units within a 
fenceline, so long as the amount of emission reductions from each 
pollutant being controlled for BART would be at least equal to those 
reductions that would be obtained by simply controlling each unit. We 
have added language to the guidelines to this effect.
Step 4: Identify the Emission Units and Pollutants That Constitute the 
BART-Eligible Source
    Background. The final step in identifying a ``BART-eligible 
source'' is to use the information from the previous three steps to 
identify the universe of equipment that makes up the BART-eligible 
source. The 2001 and 2004 proposed BART guidelines stated that if the 
emissions from the list of emissions units at a stationary source 
exceed a potential to emit of 250 tons per year for any individual 
visibility-impairing pollutant, then that collection of emissions units 
is a BART-eligible source. The guidelines also stated that a BART 
analysis would be required for each visibility-impairing pollutant 
emitted from this collection of emissions units.
    In the 2004 reproposed BART guidelines, we noted that we believed 
that section 169A(b)(2)(A) of the CAA requires a State to undertake a 
BART analysis for ``any'' visibility-impairing pollutant emitted by a 
BART-eligible source, regardless of the amount emitted. We proposed, 
however, to provide the States with the flexibility to identify de 
minimis levels for pollutants at BART-eligible sources, but limited 
that flexibility so that any such de minimis levels could not be higher 
than those used in the PSD program: 40 tons per year for 
SO2, NOX, and VOC, and 15 tons per year from 
PM10. We requested comment on this provision and on the use 
of de minimis values.
Discussion of Whether To Include All Emitted Visibility-Impairing 
Pollutants in the BART Analysis
    Comments. A number of commenters supported the concept of including 
all pollutants in the BART analysis once an individual pollutant 
triggers the BART review. Other commenters, although supportive of the 
concept generally, recommended that we should add the pollutants 
together before the comparison with the threshold.
    A number of commenters disagreed with EPA's conclusion that the CAA 
requires States to make a BART determination for any visibility-
impairing air pollutant emitted by a BART eligible source. These 
commenters stated that undertaking a BART analysis for all pollutants 
emitted by a major stationary source is an unnecessary administrative 
burden with minimal environmental benefit. Commenters argued that 
Congress intended for BART to apply only to those pollutants for which 
a source is major. Commenters accordingly recommended that the 250 ton 
per year threshold apply to each pollutant emitted by a source and that 
BART apply only to those pollutants which meet this threshold. A number 
of these commenters argued alternatively that only those pollutants 
from a source demonstrated, individually, to cause or contribute to 
visibility impairment are required to go through a BART determination.
    Final rule. We disagree with the comment that emissions of 
different visibility-impairing pollutants must be added together to 
determine whether a source exceeds the 250 ton per year threshold. The 
CAA, in section 169A(g)(7), defines a ``major stationary source'' as 
one with the potential to emit 250 tons or more of ``any pollutant.''
    We disagree with comments that the BART analysis is required only 
for those pollutants that individually exceed the 250 ton per year 
threshold. Section 169A(b)(2)(A) specifically requires States to submit 
SIPs that include a requirement that a major stationary source

which, as determined by the State * * * emits any air pollutant 
which may reasonably be anticipated to cause or contribute to any 
impairment of visibility in any [Class I area], shall procure, 
install, and operate * * * the best available retrofit technology, 
as determined by the State * * * for controlling emissions from such 
source for the purpose of eliminating or reducing any such 
impairment.

The regional haze regulations similarly require that the States submit 
a SIP that contains


[[Page 39116]]


A determination of BART for each BART-eligible source in the State 
that emits any air pollutant which may reasonably be anticipated to 
cause or contribute to any impairment of visibility in any mandatory 
Class I Federal area.

40 CFR 51.308(e)(1)(ii). Nothing in these statutory or regulatory 
requirement suggests that the BART analysis is limited to those 
pollutants for which a source is considered major. At best, these 
provisions can be read as requiring a BART determination only for those 
emissions from a specific source which do, in fact, cause or contribute 
to visibility impairment in a particular Class I area, or which could 
reasonably be anticipated to do so. Commenters, however, have not 
presented any evidence that as a general matter emissions of less than 
250 tons per year of PM2.5, SO2, or other 
visibility-impairing pollutants from potential BART sources do not 
``cause or contribute to any impairment of visibility'' in any of the 
Class I areas covered by the regional haze rule. As there is no such 
evidence currently before us, there is no basis to conclude that the 
States are required to make BART determinations only for those 
pollutants emitted in excess of 250 tons per year.
    At the same time, we agree with certain commenters that the CAA 
does not require a BART determination for any visibility impairing 
pollutant emitted by a source, regardless of the amount. After 
reviewing the language of the Act and the comments received, we have 
concluded that our interpretation of the relevant language in section 
169A(b)(2)(A) of the Act in the 2004 proposed guidelines is not 
necessarily the best reading of the BART provisions. Section 
169A(b)(2)(A) of the Act can be read to require the States to make a 
determination as to the appropriate level of BART controls, if any, for 
emissions of any visibility impairing pollutant from a source. Given 
the overall context of this provision, however, and that the purpose of 
the BART provision is to eliminate or reduce visibility impairment, it 
is reasonable to read the statute as requiring a BART determination 
only for those emissions from a source which are first determined to 
contribute to visibility impairment in a Class I area.
    The interpretation of the requirements of the regional haze program 
reflected in the discussion above does not necessitate costly and time-
consuming analyses. Consistent with the CAA and the implementing 
regulations, States can adopt a more streamlined approach to making 
BART determinations where appropriate. Although BART determinations are 
based on the totality of circumstances in a given situation, such as 
the distance of the source from a Class I area, the type and amount of 
pollutant at issue, and the availability and cost of controls, it is 
clear that in some situations, one or more factors will clearly suggest 
an outcome. Thus, for example, a State need not undertake an exhaustive 
analysis of a source's impact on visibility resulting from relatively 
minor emissions of a pollutant where it is clear that controls would be 
costly and any improvements in visibility resulting from reductions in 
emissions of that pollutant would be negligible. In a scenario, for 
example, where a source emits thousands of tons of SO2 but 
less than one hundred tons of NOX, the State could easily 
conclude that requiring expensive controls to reduce NOX 
would not be appropriate. In another situation, however, inexpensive 
NOX controls might be available and a State might reasonably 
conclude that NOX controls were justified as a means to 
improve visibility despite the fact that the source emits less than one 
hundred tons of the pollutant. Moreover, as discussed below, we are 
revising the regional haze regulations to allow the States to exempt de 
minimis emissions of SO2, NOX, and 
PM2.5 from the BART determination process which should help 
to address the concerns of certain commenters associated with the 
burden of a broad BART analysis.

De minimis levels

    Comments. Many commenters agreed that we should establish de 
minimis levels for individual pollutants in order to allow States and 
sources to avoid BART determinations for pollutants emitted in 
relatively trivial amounts. Many commenters suggested that States would 
be unlikely to impose emission limits for pollutants emitted at the 
proposed de minimis levels because it would not be cost-effective to do 
so and such emission reductions could not be expected to produce any 
perceptible improvements in visibility. Several commenters agreed that 
the pollutant coverage requirements for BART eligibility should be 
consistent with those for the PSD program, but others argued that BART 
should be required only for pollutants emitted in amounts greater than 
250 tons per year. Commenters also noted that the guidelines were not 
clear as to whether the de minimis provision would apply on a plant-
wide or unit by unit basis. A few commenters also noted that the final 
guidelines should clarify where in the BART determination process de 
minimis levels may be used.
    Other commenters opposed the use of de minimis exemptions. These 
commenters argued that it would be unreasonable to rule categorically 
that a certain level of emissions had a trivial impact on visibility 
without assessing the impacts of these emissions in particular 
circumstances. These commenters argued that States should consider the 
emissions of all visibility-impairing pollutants in a BART 
determination regardless and that, consequently, there should be no de 
minimis levels.
    Final rule. As proposed in 2004, we believe that it is reasonable 
to give States the flexibility to establish de minimis levels so as to 
allow them to exempt from the BART determination process pollutants 
emitted at very low levels from BART-eligible sources. As explained by 
the D.C. Circuit, ``categorical exemptions from the requirements of a 
statute may be permissible `as an exercise of agency power, inherent in 
most statutory schemes, to overlook circumstances that in context may 
fairly be considered de minimis.' '' \20\ The ability to create de 
minimis exemptions from a statute is a tool to be used in implementing 
the legislative design.\21\
---------------------------------------------------------------------------

    \20\ EDF et al. v. EPA, 82 F.3d 451, 466 (D.C. Cir. 1996) citing 
Alabama Power v. Costle, 636 F.2d 323 (D.C. Cir. 1979).
    \21\ Id.
---------------------------------------------------------------------------

    The intent of Congress in requiring controls on emissions from 
certain major stationary sources was to eliminate or reduce any 
anticipated contribution to visibility impairment from these sources. 
This, as section 169A(b)(2)(A) states, is the ``purpose'' of BART. In 
making a determination as to the appropriate level of controls, 
however, the States are required to take into account not only the 
visibility benefits resulting from imposing controls on these sources 
but also the costs of complying with the BART provision. The BART 
provision is accordingly designed to ensure that the States take into 
consideration all emissions of certain stationary sources in making a 
BART determination, but also to provide States with the flexibility to 
include the costs and benefits of controlling these sources in the 
calculus of determining the appropriate level of BART.
    We believe it would be permissible for States to create de minimis 
levels at a low level. If a State were to undertake a BART analysis for 
emissions of less than 40 tons of SO2 or NOX or 
15 tons of PM10 from a source, it is unlikely to result in 
anything but a trivial improvement in visibility. This is

[[Page 39117]]

because reducing emissions at these levels would have little effect on 
regional emissions loadings or visibility impairment. We believe most 
States would be unlikely to find that the costs of controlling a few 
tons of emissions were justified. Because the overall benefits to 
visibility of requiring BART determinations for emissions of less than 
the de minimis levels would be trivial, we are amending the regional 
haze rule to make clear that the States have this flexibility.
    The de minimis levels discussed today apply on a plant-wide basis. 
Applying de minimis levels on a unit by unit basis as suggested by 
certain commenters could exempt hundreds of tons of emissions of a 
visibility-impairing pollutant from BART analysis. In at least some of 
the twenty-six source categories covered by the BART provisions, a 
single control device can be used to control emissions from multiple 
units. Thus, it is possible that while emissions from each unit are 
relatively trivial, the costs of controlling emissions from multiple 
units might be cost-effective in light of the BART-eligible source's 
total emissions of the pollutant at issue. States should consider the 
control options in such situations and determine the appropriate 
approach for the specific source.
    We are revising the regional haze rule to provide States with the 
ability to establish de minimis levels up to the levels proposed in 
2004. We believe States may, if they choose, exclude from the BART 
determination process potential emissions from a source of less than 
forty tons per year of SO2 or NOX, or 15 tons per 
year for PM10. (Note also that for sources that are BART-
eligible for one pollutant, we also believe that States could allow 
those sources to model the visibility impacts of pollutants at levels 
between de minimis and 250 tons in order to show that the impact is 
negligible and should be disregarded. See section D below). In the 
guidelines, we include this as part of the BART determination in 
section IV of the guidelines. (We note that these emission levels 
represent the maximum allowable de minimis thresholds--States retain 
their discretion to set the thresholds at lesser amounts of each 
pollutant, or to not provide any pre-determined de mininis levels.) We 
believe that this approach is the clearest method for exempting trivial 
emissions from the BART determination process. Alternatively, States 
may find it useful to exclude de minimis emissions in identifying 
whether a source is subject to BART in section III of the guidelines. 
Either approach is consistent with the regulation issued in this rule.

D. How To Determine Which BART-eligible Sources Are ``Subject to BART''

Cause or Contribute
    Background. Under section 169A(b)(2)(A) of the Act, each State must 
review its BART eligible sources and determine whether they emit ``any 
air pollutant which may reasonably be anticipated to cause or 
contribute to any impairment of visibility in [a Class I] area.'' If a 
source meets this threshold, the State must then determine what is BART 
for that source.
    Proposed rule. In the reproposed guidelines, we identified three 
options for States to use in determining which BART-eligible sources 
meet the test set forth in section 169A(b)(2)(A) of the CAA. To 
determine whether a BART-eligible source is ``reasonably anticipated to 
cause or contribute to visibility impairment,'' the first proposed 
option was that a State could choose to consider the collective 
contribution of emissions from all BART-eligible sources and conclude 
that all BART-eligible sources within the State are ``reasonably 
anticipated to cause or contribute'' to some degree of visibility 
impairment in a Class I area. The preamble to the 1999 regional haze 
rule explains at length why we believe that looking to the collective 
contribution of many sources over a broad area is a reasonable 
approach, and we explained in the 2004 reproposed guideline that we 
believed that a State's decision to use a cumulative analysis at this 
stage of the BART determination process would be consistent with the 
CAA and the findings of the D.C. Circuit in American Corn Growers.
    The second proposed option was to allow a State to demonstrate, 
using a cumulative approach, that none of its BART-eligible sources 
contribute to visibility impairment. Specifically, we proposed to 
provide States with the option of performing an analysis to show that 
the full group of BART-eligible sources in a State cumulatively do not 
cause or contribute to visibility impairment in any Class I areas.
    As a third option, we proposed that a State may choose to determine 
which sources are subject to BART based on an analysis of each BART-
eligible source's individual contribution. We labeled this option as an 
``Individualized Source Exemption Process,'' and proposed that States 
use an air quality model to determine an individual source's 
contribution to visibility impairment, calculated on a 24 hour basis, 
using allowable emissions, and compared to an established threshold.
    Comments. Several commenters expressed the view that EPA was 
misinterpreting the American Corn Growers case to allow the States to 
apply a collective contribution test in determining whether BART-
eligible sources are subject to BART. These commenters took the 
position that, because this approach does not allow for a source to 
show that it does not individually cause or contribute to visibility 
impairment, it is incompatible with the language of section 
169A(b)(2)(A)of the Act. They argued that EPA should modify the 
provisions in the proposed rule to ensure that an individual source is 
afforded the opportunity to conduct an analysis to demonstrate that its 
emissions do not impair visibility in any Class I area. Conversely, 
several commenters indicated that the option to determine that all 
potential BART sources contribute to regional haze should be the 
starting point of determining BART eligibility.
    Many industry commenters and some States supported the second 
proposed option which would allow a State to demonstrate through an 
analysis of the collective contribution of all its BART-eligible 
sources that none of these sources contribute to visibility impairment. 
Several of these commenters added, however, that if this cumulative 
analysis were to show a contribution, then, consistent with the 
decision in American Corn Growers, the State must allow each individual 
source to demonstrate that its own emissions do not, by themselves, 
contribute to the problem of visibility impairment. One commenter 
requested clarification on what visibility threshold a State should use 
in determining that no sources are reasonably anticipated to cause or 
contribute to any impairment in a Class I area.
    A number of commenters supported the third option for determining 
BART applicability based on an analysis of source-specific effects on 
visibility. However, many of the commenters stated that the CAA 
requires that the States either conduct such an analysis in determining 
those sources subject to BART, or allow an individual source to make a 
showing that it does not cause or contribute to visibility impairment. 
In addition, although supportive of the general notion of allowing for 
an exemption process for BART-eligible sources, several commenters 
stated that the third option contained burdensome modeling 
requirements, and that States need a more flexible, straightforward,

[[Page 39118]]

and less costly method to make the ``cause or contribute'' 
determination.
    Several environmental groups commented that the proposed options 
potentially go too far in allowing sources to be exempted from the BART 
requirements. These commenters asserted that EPA should clarify that 
States may not allow a BART-eligible source to avoid the BART 
requirements without an affirmative demonstration by the State, or by 
the source, showing that the source does not emit any air pollutant 
which may reasonably be anticipated to cause or contribute to any 
impairment of visibility in a Class I area. Absent such a 
demonstration, they argue, a State may not choose to waive the 
requirement to conduct a BART review of the source.
    Final rule. The final BART guidelines adopt the general approach 
contained in the reproposal, providing the States with several options 
for identifying the sources subject to BART. The final BART guidelines 
describe the options contained in the reproposal as well as one new 
option. The discussion of options in the final guidelines are 
structured somewhat differently from the reproposal, and the options 
are explained in greater detail. The guidelines reaffirm that a State 
may choose to consider all BART-eligible sources to be subject to BART, 
and to make BART determinations for all its BART-eligible sources.\22\ 
For States that choose to consider exempting some or all of their BART-
eligible sources from review, the guidelines then discuss three options 
that States may use to determine whether its sources are ``reasonably 
anticipated to cause or contribute'' to visibility impairment at a 
Class I area. Options 1 and 3 are similar to options in the 2004 
reproposal; under option 1, States may use an individual source 
attribution approach, while option 3 provides the States with an 
approach for demonstrating that no sources in a State should be subject 
to BART. Option 2 is new; it is an approach for using model plants to 
exempt individual sources with common characteristics.
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    \22\ States choosing this approach should use the data being 
developed by the regional planning organizations, or on their own, 
as part of the regional haze SIP development process to make the 
showing that the State contributes to visibility impairment in one 
or more Class I areas.
---------------------------------------------------------------------------

    Threshold for visibility impact. One of the first steps in 
determining whether sources cause or contribute to visibility 
impairment for purposes of BART is to establish a threshold (quantified 
in units called ``deciviews'') against which to measure the visibility 
impact of one or more sources. We believe that a single source that is 
responsible for a 1.0 deciview change or more should be considered to 
``cause'' visibility impairment; a source that causes less than a 1.0 
deciview change may still contribute to visibility impairment and thus 
be subject to BART.
    The guidelines note that because of varying circumstances affecting 
different Class I areas, the appropriate threshold for determining 
whether a source ``contributes to any visibility impairment'' for the 
purposes of BART may reasonably differ across States. Although the 
appropriate threshold may vary, the Guidelines state that the 
contribution threshold used for BART applicability should not be higher 
than 0.5 deciviews. We discuss threshold issues in greater detail in 
the subsection immediately following this one, entitled Metric for 
Visibility Degradation.
Pollutants
    The guidelines direct that States should look at SO2, 
NOX, and direct particulate matter (PM) emissions in 
determining whether sources cause or contribute to visibility 
impairment, including both PM10 and PM2.5. 
Consistent with the approach for identifying BART-eligible sources, 
States do not need to consider less than de minimis emissions of these 
pollutants from a source.
    States may use their best judgement to determine whether VOC or 
ammonia emissions are likely to have an impact on visibility in an 
area. In addition, they may use PM10 or PM2.5 as 
an indicator for PM2.5 in determining whether a source is 
subject to BART. In determining whether a source contributes to 
visibility impairment, however, States should distinguish between the 
fine and coarse particle components of direct particulate emissions. 
Although both fine and coarse particulate matter contribute to 
visibility impairment, the long-range transport of fine particles is of 
particular concern in the formation of regional haze. Air quality 
modeling results used in the BART determination will provide a more 
accurate prediction of a source's impact on visibility if the inputs 
into the model account for the relative particle size of any directly 
emitted particulate matter (i.e. PM10 vs. PM2.5).
    We believe that PM10 is likely to contribute more to 
regional haze in arid areas than humid areas. As the Grand Canyon 
Visibility Transport Commission (GCTVC) recognized,\23\ States in the 
arid West, in particular, will need to take the coarse fraction of 
particulate matter into account in determining whether a source meets 
the threshold for BART applicability.
---------------------------------------------------------------------------

    \23\ Grand Canyon Visibility Transport Commission, 
Recommendations for Improving Western Vistas, Report to the U.S. 
EPA, June 10, 1996.
---------------------------------------------------------------------------

    Option 1. We agree with commenters supporting the use of an 
individual source analysis in determining if a BART-eligible source 
causes or contributes to visibility impairment. Consistent with 
American Corn Growers, this option provides a method for a State to 
evaluate the visibility impact from an individual source and show that 
the source is not reasonably anticipated to cause or contribute to 
visibility degradation in a Class I area and thus may be exempt from 
BART. (Note also that an individual source analysis is used to inform 
the BART determination). In general, a dispersion model is used to 
assess the visibility impact from a single source, and that impact is 
compared to a threshold which is determined by the State. The threshold 
(quantified in deciviews) is the numerical metric that is used to 
define ``cause or contribute''; if a source's impact is below the 
threshold, a State may exempt the source from BART; otherwise the 
source would be subject to BART.
    We discuss specific issues on the individualized source attribution 
process, including changes since proposal and issues raised by 
commenters, in the subsections immediately following this one: Metric 
for visibility degradation; Use of CALPUFF for visibility modeling; The 
use of natural conditions in determining visibility impacts for 
reasonable progress and comparison to threshold values; Modeling 
protocol; and Alternatives for determining visibility impacts from 
individual sources.
    Option 2. In the final guideline, we describe a modified approach, 
using model plants based on representative sources sharing certain 
characteristics, that the States may use to simplify the BART 
determination process, either to exempt (individually or as a group) 
those small sources that are not reasonably anticipated to cause or 
contribute to visibility impairment, or to identify those large sources 
that clearly should be subject to BART review. States could use the 
CALPUFF model, for example, to estimate levels of visibility impairment 
associated with different combinations of emissions and distances to 
the nearest Class I area. In carrying out this approach, the State 
could then reflect groupings of specific types of sources with 
important common characteristics, such as emissions, stack heights and 
plume characteristics, and develop ``composite model plants.'' Based on 
CALPUFF

[[Page 39119]]

analyses of these model plants, a State may find that certain types of 
sources are clearly reasonably anticipated to cause or contribute to 
visibility impairment. Conversely, representative plant analyses may 
show that certain types of sources are not reasonably anticipated to 
cause or contribute to visibility impairment. Based on the modeling 
results, a State could exempt from BART all sources that emit less than 
a certain amount per year and that are located a certain distance from 
the nearest Class I area.
    Our analyses of visibility impacts from model plants provide a 
useful example of the type of analyses that might be used to exempt 
categories of sources from BART.\24\ Based on our model plant analysis, 
EPA believes that a State could reasonably choose to exempt sources 
that emit less than 500 tons per year of NOX or 
SO2 (or combined NOX and SO2), as long 
as they are located more than 50 kilometers from any Class I area; and 
sources that emit less than 1000 tons per year of NOX or 
SO2 (or combined NOX and SO2) that are 
located more than 100 kilometers from any Class I area.
---------------------------------------------------------------------------

    \24\ Supplement to CALPUFF Analysis in Support of the June 2005 
Changes to the Regional Haze Rule, U.S. Environmental Protection 
Agency, June 15, 2005, Docket No. OAR-2002-0076.
---------------------------------------------------------------------------

    In our analysis, we developed two model plants (a EGU and a non-
EGU), with representative plume and stack characteristics, for use in 
considering the visibility impact from emission sources of different 
sizes and compositions at distances of 50, 100 and 200 kilometers from 
two hypothetical Class I areas (one in the East and one in the West). 
Because the plume and stack characteristics of these model plants were 
developed considering the broad range of sources within the EGU and 
non-EGU categories, they do not necessarily represent any specific 
plant. However, the results of these analyses may be instructive in the 
development of an exemption process for groups of BART-eligible 
sources, without modeling each of these sources individually.
    States may want to conduct their own model plant analysis that take 
into account local, regional, and other relevant factors (such as 
meteorology, sulfur dioxide, nitrogen dioxide, and ammonia). If so, you 
may want to consult your EPA Regional Office to ensure that any 
relevant technical issues are resolved before you conduct your 
modeling.
    In preparing our hypothetical examples, we have made a number of 
assumptions and exercised certain modeling choices; some of these have 
a tendency to lend conservatism to the results, overstating the likely 
impacts, while others may understate the modeling results. On balance, 
when all of these factors are considered, we believe that our examples 
reflect realistic treatments of the situations being modeled.\25\ A 
summary of the more significant elements and their implications is 
provided below.

    \25\ CALPUFF Analysis in Support of the June 2005 Changes to the 
Regional Haze Rule, U.S. Environmental Protection Agency, June 15, 
2005, Docket No. OAR-2002-0076.
---------------------------------------------------------------------------

Features of the modeling examples which may understate visibility 
impacts

     An annual emission rate was used for the example modeling 
(e.g. 10,000 TPY divided by 365 days divided by 24 hours). ``Real 
world'' sources have variable emission rates, and in any 24 hour period 
may be operating well above the annual rate.
     The monthly average relative humidity was used, rather 
than the daily average humidity, and would contribute to lowering the 
peak values in daily model averages.
     A 24-hour average was calculated from modeled hourly 
visibility impacts, reducing the impact of any one particular hour that 
could be higher due to a number of meteorological effects.

Features of the modeling examples which may overstate visibility 
impacts

     We located receptors using a grid of concentric circles 
for distances of 50, 100 and 200 km. A receptor was placed every 10 
degrees around each circle, and highest impacts were reported 
regardless of direction from the source. In actuality, receptors would 
be located only in the Class I area, or in only one direction from the 
source.
     We used simplified chemistry (i.e. for conversion of 
SO2 and NOX to fine particles) and disperson 
techniques which tend to overstate model impacts.
    Special care should be used to ensure that the criteria used in the 
modeling are appropriate for a given State. Our modeling may not be 
appropriate for every region of the country, due to the unique 
characteristics of different Class I areas and varying meteorological 
and geographical conditions in different regions. In addition, States 
may want to design their own model plants taking into account the types 
of sources at issue in their region.
    Option 3. Under the BART guidelines, a State may consider exempting 
all its BART-eligible sources from BART by conducting analyses that 
show that all of the emissions from BART-eligible sources in their 
State, taken together, are not reasonably anticipated to cause or 
contribute visibility impairment. To make such a showing, a State could 
use CALPUFF or another appropriate dispersion model to evaluate the 
impacts of individual sources on downwind Class I areas, aggregating 
those impacts to determine the collective contribution from all-BART 
eligible sources in the State. A State with a sufficiently large number 
of BART-eligible sources could also make such a showing using a 
photochemical grid model.\26\
---------------------------------------------------------------------------

    \26\ For regional haze applications, regional scale modeling 
typically involves use of a photochemical grid model that is capable 
of simulating aerosol chemistry, transport, and deposition of 
airborne pollutants, including particulate matter and ozone. 
Regional scale air quality models are generally applied for 
geographic scales ranging from a multi-state to the continental 
scale. Because of the design and intended applications of grid 
models, they may not be appropriate for BART assessments, so States 
should consult with the appropriate EPA Regional Office prior to 
carrying out any such modeling.
---------------------------------------------------------------------------

    We agree with commenters who pointed out that the option of 
allowing a State to demonstrate that the full group of BART-eligible 
sources in the State do not contribute to visibility impairment would, 
by default, satisfy an individual source contribution assessment. 
Commenters have not shown any reason to believe that if the sum total 
of emissions from the BART-eligible sources in a State do not ``cause 
or contribute'' to visibility impairment in any Class I area, that 
emissions from one such source will meet the threshold for BART 
applicability. A State following this approach accordingly need not 
undertake an affirmative demonstration based on a source by source 
analysis of visibility impacts to find that its sources are not subject 
to BART.
Metric for Visibility Degradation
    Background. The 2004 reproposed guidelines contained a proposed 
threshold for the States to use in determining whether an individual 
source could be considered to cause visibility impairment in a Class I 
area. We proposed a 0.5 deciview change relative to natural background 
conditions,\27\ as a numerical threshold for making this 
determination.\28\
---------------------------------------------------------------------------

    \27\ Guidance for Estimating Natural Visibility Conditions Under 
the Regional Haze Rule, ( U.S. Environmental Protection Agency, 
September 2003. http://www.epa.gov/ttncaaa1/t1/memoranda/rh_envcurhr_gd.pdf. Natural background conditions, expressed in 
deciviews, are defined for each Class I area. EPA has issued 
guidance for estimating natural background conditions which has 
estimates of default conditions as well as measures to develop 
refined estimates of natural conditions.
    \28\ In the proposal we noted that a 0.5 deciview change in 
visibility is linked to ``perceptibility,'' or a just noticeable 
change in most landscapes. National Acid Precipitation Assessment 
Program (NAPAP), Acid Deposition: State of Science and Technology 
Report 24, Visibility: Existing and Historical Conditions--Causes 
and Effects (Washington, DC, 1991) Appendix D at 24-D2 (``changes in 
light extinction of 5 percent will evoke a just noticeable change in 
most landscapes''). Converting a 5 percent change in light 
extinction to a change in deciviews yields a change of approximately 
0.5 deciviews.

---------------------------------------------------------------------------

[[Page 39120]]

    We proposed the CALPUFF model as the preferred approach for 
predicting whether a single source caused visibility impairment if the 
modeled results showed impacts from the source that exceeded the 
threshold on any given day during a five-year period. We also proposed 
that if a source had an estimated impact on visibility of less than 0.5 
deciviews, a State could choose to exempt the source from further BART 
analysis.
    Comments. We received numerous comments supporting the proposed 
threshold. A number of commenters stated that the 0.5 deciview 
threshold is appropriate given the low triggering threshold for 
applicability established by Congress, and that the literature supports 
it as the minimum level of perceptibility. Some commenters cited 
published documentation supporting their assertions that a minimum 
change in deciviews necessary for perceptibility is 0.5 deciviews.\29\
---------------------------------------------------------------------------

    \29\ Ibid.
---------------------------------------------------------------------------

    Other commenters criticized the threshold as too low. They stated 
that a change of 0.5 deciviews is inconsistent with language in the 
regional haze rule pointing to 1.0 deciview as the appropriate 
perceptibility threshold, and they cited more recent literature 
justifying perceptibility as greater than a change of 1 deciview.\30\
---------------------------------------------------------------------------

    \30\ Henry, R.C., Just-Noticeable Differences in Atmospheric 
Haze, Journal of the Air & Waste Management Association, 52:1238-
1243, October 2002.
---------------------------------------------------------------------------

    One commenter said that we should allow States and regional 
planning organizations (RPOs) the flexibility to determine appropriate 
visibility-impact thresholds in light of current knowledge about a 
range of perceptibility thresholds. Another commenter said that we 
should explain our basis for establishing a threshold of a one-time 
impact of greater than 0.5 deciviews, in light of the overall goal of 
the regional haze program. Yet another commenter said that the proposal 
would ``change the regulatory role of the deciview metric by converting 
it into a regulatory 0.5 deciview standard (versus a `goal') for 
defining how States must exercise their authority and discretion in 
determining whether an individual source `causes or contributes' to 
visibility impairment in a Class I area.''
    Several commenters said that the 0.5 deciview threshold is too 
high. A recurring comment was that the statutory BART applicability 
test from CAA Section 169A(b)(2)(A) contains two separate elements: 
``causation'' of any visibility impairment and ``contribution'' to any 
such impairment. Commenters pointed out that by setting a threshold of 
0.5 deciviews, we had combined ``cause or contribute'' into a single 
test of causality, thus effectively eliminating the ``contribution'' 
element of the BART applicability test. The commenters asserted that a 
single BART-eligible source can ``contribute'' to visibility impairment 
with impacts much lower than 0.5 deciviews. They argued that we must 
set the minimum threshold for individual source contribution to 
visibility impairment at the lowest level detectable by modeling or 
other appropriate analysis, and that this minimum individual 
contribution level must in any event be set at no greater than a 0.1 
deciview change relative to natural conditions, which is a clearly 
measurable level. One commenter suggested that a cause or contribute 
threshold be set at some percentage of the ``just noticeable'' change 
of 0.5 deciviews.
    Another commenter said that in a case where multiple sources each 
have a visibility impact of less than a 0.5 deciview change, but 
together result in a change of more than 0.5 deciview, each of these 
sources contributes to the resulting visibility impairment. This 
commenter asserted that BART guidelines that result in exemptions for 
these ``contributing'' sources would subvert the goals of the regional 
haze program.
    Similarly, several commenters suggested that if any combination of 
BART eligible sources causes visibility impairment in a Class I area of 
more than 0.5 deciviews (by CALPUFF modeling for any 24-hour period, 
for example), that State should determine that each individual source 
is subject to BART. Thus, the commenter added, the court's concern 
about the lack of ``empirical evidence of a source's contribution to 
visibility impairment'' would be addressed.
    Two commenters said that our requirement to use the maximum 24-hour 
value over the 5-year period of meteorological data in the modeling, as 
proposed, is too stringent, unreasonable, inappropriate, and departs 
from the previous methodologies for the regional haze program. 
Additionally they said that the threshold is restrictive because the 
single highest 24-hour modeled impact over a three- or five-year period 
may be influenced by short-term weather conditions, like high humidity, 
and the BART applicability determination should not be made based on a 
one-time occurrence.
    One commenter said that whatever the final threshold for a single-
source impact for BART sources, EPA should clarify that the purpose of 
this modeling assessment is to evaluate a source's anticipated 
contribution to uniform regional haze over the Class I area. EPA should 
state that the assumption of a uniform haze contribution based on 
CALPUFF modeling eliminates the need to assess issues related to the 
size of the Class I area, views within a Class I area, and weather 
impact interactions. Finally, one commenter said that thresholds should 
be established separately for the eastern and western regions of the 
United States, as natural visibility conditions are established 
separately for eastern and western regions in the guidance.
    Final Rule. Today's guidelines advise States to use a deciview 
metric in defining ``cause or contribute,'' as explained further below. 
The fact that the deciview is also used to track progress toward the 
goal of natural visibility does not in any way indicate that we are 
``converting'' a ``goal'' into a requirement.\31\ Use of the same 
metric in the ``cause or contribute'' context as used for establishing 
reasonable progress goals, tracking changes in visibility conditions, 
and defining baseline, current, and natural conditions simply provides 
for a consistent approach to quantifying visibility impairment.
---------------------------------------------------------------------------

    \31\ Moreover, the fact that the ultimate purpose of the 
visibility provisions is expressed as a ``goal'' does not mean that 
all aspects of the program are merely aspirational. CAA section 
169A(a)(4) requires EPA to establish regulations to ensure that 
reasonable progress is made toward the national visibility goal, and 
169A(b)(2) provides that EPA must require SIPs to contain emission 
limits, schedules of compliance, and other measures as may be 
necessary to make reasonable progress towards meeting the goal.
---------------------------------------------------------------------------

    In response to commenters who said we conflated the ``cause or 
contribute'' test, we are clarifying that for purposes of determining 
which sources are subject to BART, States should consider a 1.0 
deciview change or more from an individual source to ``cause'' 
visibility impairment, and a change of 0.5 deciviews to ``contribute'' 
to impairment.\32\
---------------------------------------------------------------------------

    \32\ If ``causing'' visibility impairment means causing a 
humanly perceptible change in visibility in virtually all situations 
(i.e. a 1.0 deciview change), then ``contributing'' to visibility 
impairment must mean having some lesser impact on the conditions 
affecting visibility that need not rise to the level of human 
perception.
---------------------------------------------------------------------------

    In a regulatory context, we believe that a State's decision as to 
an

[[Page 39121]]

appropriate threshold for contribution could depend upon the number of 
sources affecting a class I area. To illustrate, if there were only one 
emissions source affecting visibility in a class I area, that source 
could have a deciview impact only slightly below the perceptibility 
threshold without contributing to noticeable impairment. However, if 
there were 100 sources each changing visibility by 0.1 deciviews, the 
total impact would be a 10-deciview change in visibility. In this 
hypothetical example, all 100 sources would be contributing, in equal 
amounts, to substantial visibility impairment.
    Because circumstances will vary in different locations, we believe 
that States should have discretion to set an appropriate threshold 
depending on the facts of the situation. We believe, however, that it 
would be difficult for a State to justify a threshold higher than 0.5 
deciviews. In particular, 0.5 deciviews represents one half of the 1.0 
deciview level that we are equating with a single source ``causing'' 
visibility degradation. Typically, there are multiple sources that 
affect visibility in class I areas, so a source causing a 0.5 deciview 
change can be expected to be contributing to noticeable visibility 
impairment.
    In determining whether the maximum threshold of 0.5 deciviews or a 
lower threshold is appropriate for purposes of BART, we believe that 
States should consider the number of emissions sources affecting the 
class I area and the magnitude of the individual sources' impacts.\33\ 
In general, a larger number of sources causing impacts in a class I 
area may warrant a lower contribution threshold. In selecting a 
threshold, States may want to take into account the fact that 
individual sources have varying amounts of impact on visibility in 
class I areas. Depending on the facts regarding the number of sources 
affecting a class I area and their modeled impacts, the State could set 
a threshold that captures those sources responsible for most of the 
total visibility impacts, while still excluding other sources with very 
small impacts.\34\
---------------------------------------------------------------------------

    \33\ All states are working together in regional planning 
organizations, and we expect that states will have modeling 
information that identifies sources affecting visibility in 
individual class I areas, and the magnitude of their impacts.
    \34\ Under our guidelines, the contribution threshold should be 
used to determine whether an individual source is reasonably 
anticipated to contribute to visibility impairment. You should not 
aggregate the visibility effects of multiple sources and compare 
their collective effects against your contribution threshold because 
this would inappropriately create a ``contribution to contribution'' 
test.
---------------------------------------------------------------------------

    We also note that under this guidance, States would have discretion 
in setting the threshold for ``contributes to'' based on modeled 
impacts of sources. Consistent with American Corn Growers, we are not 
requiring States to find sources subject to BART regardless of their 
impact on Class I areas. We are suggesting that, in establishing a 
threshold for assessing contribution for BART, it may be logical to 
draw a line between ``contribution'' and ``non-contribution'' based on 
the number and magnitude of the various sources affecting the Class I 
areas at issue. Such an approach gives States the ability to assess the 
empirical evidence showing contribution and to design an appropriate 
regulatory regime in light of the nature of the problem. We note that 
for 750 MW power plants, such a line drawing exercise is likely to be 
unnecessary, as such sources will in most or all cases have impacts far 
exceeding 1.0 deciviews.
    Finally, we disagree that separate threshold levels should be 
established based on geography because a unit change in visibility 
expressed in deciviews, perceived or measured, is the same regardless 
of geography. As explained in the 1999 regional haze rule, the deciview 
can be used to express changes in visibility impairment in a way that 
corresponds to human perception in a linear manner. As a result, using 
the deciview as the metric for measuring visibility means, for example, 
that a one deciview change in a highly impaired environment would be 
perceived as roughly the same degree of change as one deciview in a 
relatively clear environment, and geography is not a factor.
Interpretation of CALPUFF Results
    The standard CALPUFF modeling run provides day-by-day estimates of 
a source's visibility effects over a five-year period. In the proposed 
BART guideline, we indicated that if the maximum daily visibility value 
at any receptor over the five years modeled is greater than the ``cause 
or contribute'' threshold, then the State should conclude that the 
source is subject to BART. A number of commenters took issue with our 
proposal to use the 24-hour maximum modeled visibility impact over five 
years of meteorological data. Several of them pointed out, for example, 
that the maximum modeled 24-hour impact may be an outlier unduly 
influenced by weather. We agree that the maximum modeled effect in a 
five-year period could be the result of unusual meteorology. We also 
recognize that, although CALPUFF is the best currently available tool 
for analyzing the visibility effects of individual sources, it is a 
model that includes certain assumptions and uncertainties. Thus, we 
agree with commenters that a State should not necessarily rely on the 
maximum modeled impact in determining whether a source may reasonably 
be anticipated to contribute to visibility impairment in a Class I 
area.
    The final guideline states that it would be reasonable for States 
to compare the 98th percentile of CALPUFF modeling results against the 
``contribution'' threshold established by the State for purposes of 
determining BART applicability. Some stakeholders have argued for the 
90th percentile value, or even lower, contending that EPA should not 
use extreme cases to make BART applicability decisions. EPA agrees 
that, in most cases, important public policy decisions should not be 
based on the extreme tails of a distribution. We have concluded, 
however, that the 98th percentile is appropriate in this case.
    The use of 90th percentile value would effectively allow visibility 
effects that are predicted to occur at the level of the threshold (or 
higher) on 36 or 37 days a year. We do not believe that such an 
approach would be consistent with the language of the statute. Second, 
we note that the 98th percentile value would only be used to determine 
whether a particular BART-eligible source would be subject to further 
review by the State. In determining what, if any, emission controls 
should be required, the State will have the opportunity to consider the 
frequency, duration, and intensity of a source's predicted effect on 
visibility.
    On the other hand, there are other features of our recommended 
modeling approach that are likely to overstate the actual visibility 
effects of an individual source. Most important, the simplified 
chemistry in the model tends to magnify the actual visibility effects 
of that source. Because of these features and the uncertainties 
associated with the model, we believe it is appropriate to use the 98th 
percentile--a more robust approach that does not give undue weight to 
the extreme tail of the distribution. The use of the 98th percentile of 
modeled visibility values would appear to exclude roughly 7 days per 
year from consideration. In our judgment, this approach will 
effectively capture the sources that contribute to visibility 
impairment in a Class I area, while minimizing the likelihood that the 
highest modeled visibility impacts might be caused by unusual 
meteorology or conservative assumptions in the model.

[[Page 39122]]

Use of CALPUFF for Visibility Modeling
    Background. In providing the States with the option of making a 
determination as to which sources are subject to BART based on a 
consideration of each source's individual contribution to visibility 
impairment, we proposed that States use an air quality model such as 
CALPUFF. We also proposed that States use a CALPUFF or other EPA 
approved model in the BART analysis itself. The CALPUFF system, as 
explained in the 2004 reproposed guideline, consists of a diagnostic 
meteorological model, a gaussian puff dispersion model with algorithms 
for chemical transformation and complex terrain, and a post processor 
for calculating concentration fields and visibility impacts.
    The regional haze rule addresses visibility impairment caused by 
emissions of fine particles and their precursors. As fine particle 
precursors, such as SO2 or NOX, are dispersed, 
they react in the atmosphere with other pollutants to form visibility-
impairing pollutants. In fact, Congress implicitly recognized in 1977 
the role of chemical transformation in creating visibility impairment, 
when it stated that the ``visibility problem is caused primarily by 
emissions of SO2, [NOX], and particulate 
matter.'' \35\ In most cases, to predict the impacts of a source's 
specific contribution to visibility impairment, a State will need a 
tool that takes into account not only the transport and diffusion of 
directly emitted PM2.5 but also one that can address 
chemical transformation.
---------------------------------------------------------------------------

    \35\ H.R. Rep. No. 95-294 at 204 (1077).
---------------------------------------------------------------------------

    Because the air quality model CALPUFF is currently the best 
application available to predict the impacts of a single source on 
visibility in a Class I area, we proposed that a CALPUFF assessment be 
used as the preferred approach first, for determining whether an 
individual source is subject to BART, and second, in the BART 
determination process. The CALPUFF assessment is specific to each 
source, taking into account the individual source's emission 
characteristics, location, and the particular meteorological, 
topographical, and climatological conditions of the area in which the 
source is located, any of which may have an impact on the transport of 
PM2.5 and its precursors. CALPUFF can be used to estimate 
not only the effects of directly emitted PM2.5 emissions 
from a source, but also to predict the visibility impacts from the 
transport and chemical transformation of fine particle precursors.
    The CALPUFF model is generally intended for use on scales from 50 
km to several hundred kilometers from a source. As a general matter, 
States will typically need to assess the impacts of potential BART 
sources on Class I areas located more than 50 km from the source.\36\ 
However, in situations where the State is assessing visibility impacts 
for source-receptor distances less than 50 km, we proposed that States 
use their discretion in determining visibility impacts, giving 
consideration to both CALPUFF and other EPA-approved methods. As an 
example, we suggested that States could use an appropriate local-scale 
plume impact model, such as PLUVUEII,\37\ to determine whether a 
source's emissions are below a level that would be reasonably 
anticipated to cause or contribute to visibility impairment in any 
Class I area.
---------------------------------------------------------------------------

    \36\ To determine whether a BART-eligible source ``may 
reasonably be anticipated to cause or contribute to any visibility 
impairment in any Class I area,'' it may not always be sufficient 
for the State to predict the impacts of a BART-eligible source only 
on the nearest Class I area (or on the nearest receptor in the 
nearest Class I area). The particular meteorological and 
topographical conditions, for example, could mean that a source's 
greatest impacts occurred at a Class I area other than the nearest 
one.
    \37\ PLUVUEII is a model used for estimating visual range 
reduction and atmospheric discoloration caused by plumes resulting 
from the emissions of particles, nitrogen oxides, and sulfur oxides 
from a single source. The model predicts the transport, dispersion, 
chemical reactions, optical effects and surface deposition of point 
or area source emissions. It is available at http://www.epa.gov/scram001/tt22.htm#pluvue.
---------------------------------------------------------------------------

    Comments. A number of States, environmental groups, and some 
industry commenters strongly supported the use of CALPUFF as proposed. 
Many commenters supported the use of CALPUFF but indicated that States 
must have the flexibility to use additional tools for their individual 
source analyses. Some suggested options for the ``cause or contribute'' 
determination were the use of photochemical grid models, or more 
simplified, non-modeling approaches. Commenters claimed that States 
must have the option to incorporate advances in science and 
technologies into models or other applications that may produce more 
accurate simulations of meteorology, chemistry, and visibility 
impairment. Other industry groups and States argued that CALPUFF has 
significant limitations, especially simulating complex atmospheric 
chemistry, and that EPA's recommendation of CALPUFF as the preferred 
approach is therefore inappropriate.
    Another issue raised by commenters was the use of CALPUFF for 
estimating secondary particulate matter formation. Commenters 
recognized that CALPUFF was incorporated into the ``Guideline on Air 
Quality Models'' at 40 CFR part 51, appendix W in April 2003 as the 
preferred model for Prevention of Significant Deterioration (PSD) 
increment and National Ambient Air Quality Standards (NAAQS) compliance 
assessments of long range transport of primary emissions of 
SO2 and PM2.5. However, commenters stated that 
CALPUFF has not been incorporated into the Guideline on Air Quality 
Models for predicting the secondary formation of PM. The commenters 
remarked that EPA guidance indicates that photochemical grid models be 
used to simulate secondary PM formation and concluded on this basis 
that the application of CALPUFF as we proposed is in conflict with our 
guidance.
    Final rule. We believe that CALPUFF is an appropriate application 
for States to use for the particular purposes of this rule, to 
determine if an individual source is reasonably anticipated to cause or 
contribute to impairment of visibility in Class I areas, and to predict 
the degree of visibility improvement which could reasonably be 
anticipated to result from the use of retrofit technology at an 
individual source. We encourage States to use it for these 
purposes.\38\
---------------------------------------------------------------------------

    \38\ The model code and its documentation are available at no 
cost for download from http://www.epa.gov/scram001/tt22.htm#calpuff.
---------------------------------------------------------------------------

    CALPUFF is the best modeling application available for predicting a 
single source's contribution to visibility impairment. It is the only 
EPA-approved model for use in estimating single source pollutant 
concentrations resulting from the long range transport of primary 
pollutants. In addition, it can also be used for some purposes, such as 
the visibility assessments addressed in today's rule, to account for 
the chemical transformation of SO2 and NOX. As 
explained above, simulating the effect of precursor pollutant emissions 
on PM2.5 concentrations requires air quality modeling that 
not only addresses transport and diffusion, but also chemical 
transformations. CALPUFF incorporates algorithms for predicting both. 
At a minimum, CALPUFF can be used to estimate the relative impacts of 
BART-eligible sources. We are confident that CALPUFF distinguishes, 
comparatively, the relative contributions from sources such that the 
differences in source configurations, sizes, emission rates, and 
visibility impacts are well-reflected in the model results. States can 
make judgements

[[Page 39123]]

concerning the conservativeness or overestimation, if any, of the 
results. In fact, although we focused on the use of CALPUFF for primary 
pollutants in revising the Guideline of Air Quality Modeling, section 
---------------------------------------------------------------------------
7.2.1.e. of the Guideline states:

    e. CALPUFF (Section A.3) may be applied when assessment is 
needed of reasonably attributable haze impairment or atmospheric 
deposition due to one or a small group of sources. This situation 
may involve more sources and larger modeling domains than that to 
which VISCREEN ideally may be applied. The procedures and analyses 
should be determined in consultation with the appropriate reviewing 
authority (paragraph 3.0(b) and the affected FLM(s).

    We believe that our proposed use of CALPUFF is thus fully in 
keeping with the Guideline on Air Quality Models, especially in light 
of the low triggering threshold for determining whether a source is 
reasonably anticipated to cause or contribute to visibility impairment 
in a Class I area, and the fact that the modeling results are used as 
only one of five statutory criteria evaluated to determine BART 
emission limits.
    Even so, as commenters point out, CALPUFF has not yet been fully 
evaluated for secondary pollutant formation. For the specific purposes 
of the regional haze rule's BART provisions, however, we have concluded 
that CALPUFF is sufficiently reliable to inform the decision making 
process.
    EPA revised the Guideline on Air Quality Models in 2003, in part, 
to add CALPUFF to the list of approved models for particular uses. At 
that time, we considered comments that CALPUFF should be approved for 
use in predicting the impact of secondary emissions on particulate 
matter concentrations. As we stated in the revision, CALPUFF represents 
a substantial improvement in methods for assessing long-range transport 
of air pollutants. However, as explained in the response to comments 
for that rulemaking, the modeling results in the context of a PSD 
review may be used as the sole determining factor in denying a source a 
permit to construct.\39\ Although its use in simulating long-range 
transport is beneficial, given the significance of the modeling results 
in assessing increment consumption due to a single source's impacts, we 
made a determination that it would not be appropriate in the rulemaking 
revising Appendix W to approve CALPUFF for use in modeling secondary 
emissions.
---------------------------------------------------------------------------

    \39\ Under CAA section 165(a), a major emitting facility may not 
be constructed unless the owner or operator of the facility 
demonstrates that the emissions from the facility will not cause or 
contribute air pollution in excess of an increment or NAAQS.
---------------------------------------------------------------------------

    In contrast to the significance of the modeling results in the PSD 
context, the use of CALPUFF in the context of the regional haze rule is 
not determinative of a source's ability to construct or operate. A 
State may use CALPUFF to determine whether a source can reasonably be 
anticipated to cause or contribute to visibility impairment and so 
should be subject to additional review to determine if the source 
should be subject to control.
    Based on our analysis of the power plants covered by the 
guidelines, we believe that all but a handful of these plants have 
impacts of greater than 1.0 deciview on one or more Class I areas.\40\ 
In fact, we anticipate that most of these plants are predicted to have 
much higher maximum impacts.\41\ Because of the scale of the predicted 
impacts from these sources, CALPUFF is an appropriate or a reasonable 
application to determine whether such a facility can reasonably be 
anticipated to cause or contribute to any impairment of visibility. In 
other words, to find that a source with a predicted maximum impact 
greater than 2 or 3 deciviews meets the contribution threshold adopted 
by the States does not require the degree of certainty in the results 
of the model that might be required for other regulatory purposes.
---------------------------------------------------------------------------

    \40\ CALPUFF Analysis in Support of the Regional Haze Rule, U.S. 
Environmental Protection Agency, April 15, 2005, Docket No. OAR-
2002-0076.
    \41\ Ibid.
---------------------------------------------------------------------------

    In the unlikely case that a State were to find that a 750 MW power 
plant's predicted contribution to visibility impairment is within a 
very narrow range between exemption from or being subject to BART, the 
State can work with EPA and the FLM to evaluate the CALPUFF results in 
combination with information derived from other appropriate techniques 
for estimating visibility impacts to inform the BART applicability 
determination. Similarly for other types of BART eligible sources, 
States can work with the EPA and FLM to determine appropriate methods 
for assessing a single source's impacts on visibility.
    As discussed in section E. below we also recommend that the States 
use CALPUFF as a screening application in estimating the degree of 
visibility improvement that may reasonably be expected from controlling 
a single source in order to inform the BART determination. As we noted 
in 2004, this estimate of visibility improvement does not by itself 
dictate the level of control a State would impose on a source; ``the 
degree of improvement in visibility which may reasonably be anticipated 
to result from the use of [BART]'' is only one of five criteria that 
the State must consider together in making a BART determination. The 
State makes a BART determination based on the estimates available for 
each criterion, and as the CAA does not specify how the State should 
take these factors into account, the States are free to determine the 
weight and significance to be assigned to each factor. CALPUFF 
accordingly is an appropriate application for use in combination with 
an analysis of the other statutory factors, to inform decisions related 
to BART.
    We understand the concerns of commenters that the chemistry modules 
of the CALPUFF model are less advanced than some of the more recent 
atmospheric chemistry simulations. To date, no other modeling 
applications with updated chemistry have been approved by EPA to 
estimate single source pollutant concentrations from long range 
transport. In its next review of the Guideline on Air Quality Models, 
EPA will evaluate these and other newer approaches and determine 
whether they are sufficiently documented, technically valid, and 
reliable to approve for general use. In the meantime, as the Guideline 
makes clear, States are free to make their own judgements about which 
of these or other alternative approaches are valid and appropriate for 
their intended applications.
    Theoretically, the CALPUFF chemistry simulations, in total, may 
lead to model predictions that are generally overestimated at distances 
downwind of 200 km. Again, States can make judgements concerning the 
conservativeness or overestimation, if any, of the results.
    The use of other models and techniques to estimate if a source 
causes or contributes to visibility impairment may be considered by the 
State, and the BART guidelines preserve a State's ability to use other 
models. Regional scale photochemical grid models may have merit, but 
such models have been designed to assess cumulative impacts, not 
impacts from individual sources. Such models are very resource 
intensive and time consuming relative to CALPUFF, but States may 
consider their use for SIP development in the future as they are 
adapted and demonstrated to be appropriate for single source 
applications. However, to date, regional models have not been evaluated 
for single source applications. Their use may be more appropriate in 
the cumulative modeling options discussed

[[Page 39124]]

above.\42\ In evaluating visibility improvement as one of the five 
factors to consider in setting BART controls, other models, used in 
combination with CALPUFF may be helpful in providing a relative sense 
of the source's visibility impact and can aid in informing the BART 
decision. A discussion of the use of alternative models is given in the 
Guideline on Air Quality in appendix W, section 3.2.
---------------------------------------------------------------------------

    \42\ For regional haze applications, regional scale modeling 
typically involves use of a photochemical grid model that is capable 
of simulating aerosol chemistry, transport, and deposition of 
airborne pollutants, including particulate matter and ozone. 
Regional scale air quality models are generally applied for 
geographic scales ranging from a multi-state to the continental 
scale. Because of the design and intended applications of grid 
models, they may not be appropriate for BART assessments, so States 
should consult with the appropriate EPA Regional Office prior to 
carrying out any such modeling.
---------------------------------------------------------------------------

The Use of Natural Conditions in Determining Visibility Impacts for 
Reasonable Progress and Comparison to Threshold Values
    Background. As set out in section 169A(a) of the CAA and stated in 
the 1999 regional haze rule, a return to natural visibility conditions, 
or the visibility conditions that would be experienced in the absence 
of human-caused impairment, is the ultimate goal of the regional haze 
program. To measure progress toward this goal, the regional haze rule 
requires that a comparison with natural conditions for the 20 percent 
best and worst days to calculate ``reasonable progress'' 
determinations. Default values for natural visibility conditions are 
provided in EPA guidance.\43\ In the 2004 reproposal of the BART 
guidelines, we proposed that changes in visibility, expressed in 
deciviews, should be determined by comparing the impact from a single 
source to natural visibility conditions. That impact should then be 
compared to a threshold impact, also expressed in deciviews, to assess 
if a BART-eligible source should be subject to a BART review.
---------------------------------------------------------------------------

    \43\ Guidance for Estimating Natural Visibility Conditions Under 
the Regional Haze Rule, U.S. Environmental Protection Agency, 
September 2003. http://www.epa.gov/ttncaaa1/t1/memoranda/rh_envcurhr_gd.pdf. Natural background conditions, expressed in 
deciviews, are defined for each Class I area. EPA has issued 
guidance for estimating natural background conditions which has 
estimates of default conditions as well as measures to develop 
refined estimates of natural conditions.
---------------------------------------------------------------------------

    Comments. Opposing commenters said that a return to natural 
conditions is unattainable as it would require the elimination of every 
manmade source, and that changes should be compared against currently 
existing conditions. They added that true ``natural conditions'' cannot 
be verified, do not account for manmade emissions from other countries, 
and are not a realistic target for improvement. Further, they argued 
that natural conditions are a ``goal'' representing a benchmark that is 
relevant to the States' determination, under the regional haze program, 
of the level of ``reasonable progress'' to achieve; however they stated 
that there is no legal requirement (and there could not be a legal 
requirement) that the natural conditions goal ultimately must be 
achieved. Several commenters added that current visibility conditions 
make more sense as a baseline because sources that are subject to BART 
today will likely not be in operation in the 2064 time frame. A 
commenter added that using current visibility conditions for the 
analysis will give a more realistic, real-world prediction of whether 
controlling the source pursuant to BART will actually improve 
visibility. The commenter said that Congress did not intend for sources 
to have to consider retrofitting controls under the BART provision if 
those sources currently are not impacting real-world visibility. Other 
utility groups stated that in addition to international emissions, the 
estimated natural visibility conditions failed to account for natural 
phenomena such as sea salt, wildfires, and natural organics. One 
commenter noted that natural visibility estimates will be revised and 
refined over time and it would be unwise to compare impacts and 
improvements to a moving baseline.
    On the other hand, numerous commenters supported the use of natural 
visibility conditions as a baseline for measuring visibility 
improvements. Several environmental groups said that any increase in 
the baseline beyond natural visibility conditions will unlawfully 
distort and weaken the BART requirement by effectively raising the 
applicability threshold in less protected, highly polluted areas, which 
would be illogical. Further, they pointed out that these BART-eligible 
sources clearly are contributing to the very manmade visibility 
impairment that the Act is explicitly designed to remedy by a return to 
natural conditions. They added that measuring natural conditions as 
opposed to some other baseline condition is a more appropriate 
approach, given that the planning goal is to achieve natural visibility 
by the end of the program. They also added that a baseline other than 
natural conditions would never assure ``reasonable progress''.
    Finally, two commenters asked for clarification on the values for 
natural conditions to be used for estimating changes in visibility. The 
commenters appeared to assume that we intended for the comparison to be 
done for natural visibility conditions on the 20 percent best days.
    Final Rule. We disagree with commenters saying that the use of 
natural conditions as the baseline for making visibility impact 
determinations is inappropriate. The visibility goal of the CAA is both 
the remedying of existing impairment, and prevention of future 
impairment. The court, in American Corn Growers, upheld our 
interpretation of that goal as the return to natural visibility 
conditions.\44\ Long-term regional haze strategies are developed to 
make ``reasonable progress'' towards the CAA goal, and States must 
demonstrate reasonable progress in their regional haze State 
implementation plans (SIPs). Since the BART program is one component of 
that demonstration, visibility changes due to BART are appropriately 
measured against the target of natural conditions.
---------------------------------------------------------------------------

    \44\ See also our explanation of the CAA goal provided in the 
regional haze rule at 64 FR at 35720-35722. We note that the court 
in American Corn Growers also observed, ``the natural visibility 
goal is not a mandate, it is a goal.'' 291 F.3d at 27.
---------------------------------------------------------------------------

    In establishing the goal of natural conditions, Congress made BART 
applicable to sources which ``may be reasonably anticipated to cause or 
contribute to any impairment of visibility at any Class I area''. Using 
existing conditions as the baseline for single source visibility impact 
determinations would create the following paradox: the dirtier the 
existing air, the less likely it would be that any control is required. 
This is true because of the nonlinear nature of visibility impairment. 
In other words, as a Class I area becomes more polluted, any individual 
source's contribution to changes in impairment becomes geometrically 
less. Therefore the more polluted the Class I area would become, the 
less control would seem to be needed from an individual source. We 
agree that this kind of calculation would essentially raise the ``cause 
or contribute'' applicability threshold to a level that would never 
allow enough emission control to significantly improve visibility. Such 
a reading would render the visibility provisions meaningless, as EPA 
and the States would be prevented from assuring ``reasonable progress'' 
and fulfilling the statutorily-defined goals of the visibility program. 
Conversely, measuring improvement against clean conditions would ensure 
reasonable progress toward those clean conditions.

[[Page 39125]]

    With regard to BART-eligible sources not being in operation for the 
duration of the program, a State, in making BART determinations, is 
explicitly directed by the CAA to account for the remaining useful life 
of a source. Thus, States may factor into their reasonable progress 
estimates those shut-downs that are required and effected in permit or 
SIP provisions. In addition, as provided for under our guidance,\45\ 
proper accounting for international emissions and natural phenomena is 
in the 5 year SIP progress report, not in the setting of natural 
visibility estimates. Finally, these final BART guidelines use the 
natural visibility baseline for the 20 percent best visibility days for 
comparison to the ``cause or contribute'' applicability thresholds. We 
believe this estimated baseline is likely to be reasonably conservative 
and consistent with the goal of natural conditions.
---------------------------------------------------------------------------

    \45\ Guidance for Estimating Natural Visibility Conditions Under 
the Regional Haze Rule, U.S. Environmental Protection Agency, 
September 2003. http://www.epa.gov/ttncaaa1/t1/memoranda/rh_envcurhr_gd.pdf.
---------------------------------------------------------------------------

Modeling Protocol
    Background. The 2004 guidelines proposed that a written modeling 
protocol be submitted for assessing visibility impacts from sources at 
distances greater than 200 km from a Class I area. The proposal 
indicated that the protocol should include a description of the methods 
and procedures to follow, for approval by the appropriate reviewing 
authority; critical items to include in the protocol are meteorological 
and terrain data, source-specific information (stack height, 
temperature, exit velocity, elevation, and allowable emission rate of 
applicable pollutants), and receptor data from appropriate Class I 
areas.
    Comments. All of the comments supported the development of a 
written modeling protocol. Industry, Federal, and State commenters said 
a modeling protocol should be required of all States and stakeholders 
who are performing the BART modeling analysis. Commenters said the 
protocol should allow all interested parties an opportunity to 
understand the modeling approach and how the results will be used, and 
that the State should provide opportunity for comments on the 
procedures prior to the publication of the final results.
    Many utility groups commented that the protocol should provide 
States with flexibility and that the choice of models should be at the 
States' (or RPOs') discretion. Some commenters stressed that it is 
important that states and sources retain the flexibility to decide how 
to set up and run the selected model, while others asked for specific 
guidance on the setup of CALPUFF or other approved models, including on 
specific parameters (e.g. how to adjust for cases where sources are 
greater than 200 km from a Class I area).
    Regarding the approval of a modeling protocol, some commenters said 
that the protocol should be approved by EPA. Others stated, however, 
that we should have only an advisory role in development of the 
protocol. They said that States are in a better position to determine 
which modeling input values best reflect conditions in their States.
    Several commenters representing environmental groups said we should 
develop a CALPUFF protocol that must be followed and should include, 
among other items, meteorological data (i.e., where available 5 years 
of data should be used), emissions reported for the same meteorological 
years, documented source parameters, model physical parameters, and 
assumed background concentrations for ozone and ammonia (based on 
nearby reliable observations and/or regional modeling results). They 
added that a protocol developed by EPA would help to produce consistent 
BART determinations across various sources and geographic areas for 
both shorter and longer distances. FLMs stated that this is also an 
appropriate time to create regional modeling platforms for CALPUFF, 
which would allow States and sources to run the model more 
expeditiously and more consistently. They recommended that we consider 
a multi-agency process to reach agreement on an appropriate modeling 
protocol prior to allowing BART applicability and control 
determinations to be based on model results. FLMs added that it would 
be helpful to establish a national procedure for this process, 
including a methodology for establishing natural background conditions, 
background ammonia concentrations, and determining sulfuric acid 
emission rates. Such a process, they said, could reasonably be engaged 
in prior to deadlines for state implementation plans, and would not 
delay implementation of the BART guidelines. The FLMs noted that 
consistent, nationally applicable guidance is essential, and that once 
it is developed, virtually no deviations should be allowed. Finally, 
they added that the CALPUFF modeling exercises should follow the 
Interagency Workgroup on Air Quality Modeling (IWAQM) Phase 2 Summary 
Report and Recommendations for Modeling Long Range Transport 
Impacts,\46\ but that we, in consultation with the FLMs and States, 
should also publish additional guidance to address more recent issues 
such as particle speciation, emission rate averaging times, and 
``natural obscuration.'' Another State commenter said that The 
Guideline on Air Quality Models (CFR Part 51, Appendix W) should be 
included along with the IWAQM Report as a reference for CALPUFF setup. 
One RPO commented that we should provide data, perhaps using example 
facilities, to demonstrate the effect of the process so that States can 
get a better feeling for which sources are likely to fall below the 0.5 
deciview threshold. This would help States understand the net effect of 
all of the parameters chosen in the exemption process.
---------------------------------------------------------------------------

    \46\ Interagency Workgroup on Air Quality Modeling (IWAQM) Phase 
2 Summary Report and Recommendations for Modeling Long Range 
Transport Impacts, U.S. Environmental Protection Agency, EPA-454/R-
98-019, December 1998.
---------------------------------------------------------------------------

    Commenters also said that we should continuously revise modeling 
protocols by providing a modeling clearinghouse to States, and further, 
that we should consider new models for use, such as the Community 
Multiscale Air Quality (CMAQ) model.
    There were specific comments requesting guidance for calculating 
visibility impacts and other general modeling concerns. One technical 
comment was that the guidelines should specify that the IMPROVE monitor 
is the receptor by which modeled visibility impacts should be evaluated 
with the CALPUFF model. Another commenter suggested using recent 
scientific evidence to update the light extinction coefficients used by 
CALPUFF to calculate visibility changes. These commenters also stated 
that CALPUFF might be improved by capping the relative humidity to 
lower values than are currently used.
    Additional commenters representing utility organizations discussed 
how to identify Class I areas that should be modeled. They said that 
the guidelines should require sources to model only the nearest Class I 
area (or possibly the two closest), and one commenter said that we 
should provide a reasonable methodology to minimize the effort needed 
to address impacts from BART-eligible sources on multiple Class I 
areas.
    Final Rule. We agree that States should adopt modeling protocols 
for all modeling demonstrations, regardless of the distance from the 
BART-eligible source and the Class I area impacted. We are therefore 
dropping the 200 km and greater distance requirement from the 
guidelines. As noted in the 2004 re-

[[Page 39126]]

proposal, we believe that potential uncertainties in model performance 
may be greater at distances greater than 200 km for a source. A 
modeling protocol may reduce the need for additional analyses. We favor 
coordination among States, EPA regions, RPOs, and other federal 
agencies to agree on a modeling protocol(s) which would provide 
consistent application.
    In developing a modeling protocol, we also encourage States to use 
the framework provided for model setup in EPA's IWAQM. CALPUFF model 
users may find default settings in that document which may be 
appropriate for their modeling situations and add an element of 
consistency to model applications. The Guideline on Air Quality Models 
(CFR Part 51, Appendix W) also provides useful guidance.
    We do, however, understand and agree that States have flexibility 
developing a modeling protocol. Moreover, the diversity of the nation's 
topography and climate, and variations in source configurations and 
operating characteristics, dictate against a strict modeling 
``cookbook''. A State may need to address site-specific circumstances 
at individual sources potentially affecting a specific Class I area. 
For example, in a particular area a State may have available emissions 
data, that is more representative of the modeling domain, which may 
supplement the model defaults. States may want to consult with the 
appropriate EPA regional office and Federal Land Managers in adjusting 
the model input parameters. The modeling input recommendations in the 
IWAQM report are designed for visibility impact applications, and those 
defaults allow for tailoring for a given application (e.g. puff 
splitting). The model developers Web site \47\ also has a series of 
frequently asked questions with answers to assist users in tailoring 
model applications.
---------------------------------------------------------------------------

    \47\ http://www.src.com/calpuff/calpuff1.htm.
---------------------------------------------------------------------------

    We agree that we have only an advisory role in development of the 
protocol as the States better understand the BART-eligible source 
configurations and the geophysical and meteorological data affecting 
their particular Class I area(s).
    In the protocol development process, we support the idea of 
designing example runs, as we have done in our example analysis for 
EGUs,\48\ so that States may get a better understanding of what 
visibility impacts might be expected from a particular type of source 
or sources. Once a protocol has been finalized, a State may be able to 
use example runs as a proxy in making BART determinations which could 
potentially eliminate the need for case-by-case review for every BART-
eligible source. A common sense approach should be taken, particularly 
where an analysis may add a significant resource burden to a State. For 
example, if there are multiple Class I areas in relatively close 
proximity to a BART-eligible source, a State may model a full field of 
receptors at the closest Class I area. Then a few strategic receptors 
may be added at the other Class I areas (perhaps at the closest point 
to the source, a receptor at the highest and lowest elevation in the 
Class I area, a receptor at the IMPROVE monitor, and a few receptors 
that are expected to be at the approximate plume release height). If 
the highest modeled impacts are observed at the nearest Class I area, a 
State may choose not to analyze the other Class I areas any further and 
additional analyses might be unwarranted.
---------------------------------------------------------------------------

    \48\ CALPUFF Analysis in Support of the June 2005 Changes to the 
Regional Haze Rule,U.S. Environmental Protection Agency, June 15, 
2005, Docket No. OAR-2002-0076.
---------------------------------------------------------------------------

    As models are revised and advances in science are incorporated into 
the models, we can make certain that revisions to protocols are made 
accordingly. We will work closely with States and FLMs, as should 
States; we expect that States will also work closely with FLMs 
throughout the protocol development process. We expect a similar 
protocol development process for other models that may be used, once 
those models are developed to predict and track single source impacts 
and demonstrate acceptable model performance. States should contact the 
appropriate FLM and EPA regional office for the latest guidance and 
modeling updates.
Alternatives for Determining Visibility Impacts From Individual Sources
    Background. In the 2004 reproposal, we requested comment on the 
following alternatives to CALPUFF modeling for determining whether 
individual sources cause or contribute to visibility impairment: look-
up tables developed from screening-level air quality modeling; running 
CALPUFF in a simpler screening mode than the preferred approach; a 
source ranking methodology; and an emissions divided by distance (Q/D) 
method. Except for the simplified CALPUFF approach, all alternatives 
were based on developing a relationship between source emissions and 
the source's distance to a Class I area. Each of these approaches was 
intended to reduce the resource burden on States.
    Comments. Some commenters supported the use of alternative 
approaches, while others suggested that the alternatives could be used 
either in conjunction, or in hierarchical fashion, with modeling 
approaches. Many commenters were opposed to their use. The opposing 
comments were consistent in stating that the alternatives were 
inappropriate because they did not account for important factors such 
as terrain, local meteorological data, prevailing wind directions 
(which influence pollutant transport), and differences in stack release 
parameters. Commenters added that there is no direct connection between 
emissions, distance, and visibility impairment, and that the methods 
treat SO2 and NOX equally for impairment 
estimates.
    Final Rule. We disagree that the alternatives are necessarily 
inappropriate, but we share most of the concerns articulated by the 
opposing commenters. We believe that alternatives should not be used to 
exempt a source from BART review without more rigorous evaluations and 
sensitivity tests showing that the results are at least as conservative 
as the CALPUFF model. We know of at least one study showing that, for 
one location and for one year, there is no guarantee that the 
simplified CALPUFF technique is as conservative as the preferred 
approach \49\. While we are not adopting in the guideline any specific 
alternative to modeling for power plants greater than 750MW, a State 
may develop its own alternative approach for the other source 
categories to determine if a source would be subject to BART, provided 
that the alternative demonstrates a sufficient basis to determine 
clearly that the source causes or contributes to visibility impairment, 
or that more refined analysis is warranted. Use of an alternative 
approach could be a conservative non-modeling method for easing a 
State's resource burden. We believe conservatism is needed because of 
the purpose of the test: i.e. solely to determine if a closer look at 
the source is warranted.
---------------------------------------------------------------------------

    \49\ Analysis of the CALMET/CALPUFF Modeling System in a 
Screening Mode, U.S. Environmental Protection Agency, November 1998, 
Docket No. OAR-2002-0076.
---------------------------------------------------------------------------

E. The BART Determination Process

    Background. CAA section 169A(g)(7) directs States to consider five 
factors in making BART determinations. The regional haze rule codified 
these factors in 40 CFR 51.308(e)(1)(ii)(B), which directs States to 
identify the ``best system of continuous emissions control

[[Page 39127]]

technology'' taking into account ``the technology available, the costs 
of compliance, the energy and nonair quality environmental impacts of 
compliance, any pollution control equipment in use at the source, and 
the remaining useful life of the source.'' Section IV. of the BART 
guidelines provides a step-by-step guide to conducting a BART 
determination which takes these factors into account.
    This section of the preamble addresses a number of issues relative 
to the process for conducting a BART determination contained in Section 
IV of the BART guidelines.
1. What Is Meant by ``Technical Feasibility of the Control Options'' in 
Step 2 of the BART Determination?
    Comments. We received several comments on this discussion, both on 
the 2001 proposal and on the 2004 reproposal. One commenter recommended 
that the concept of available technology for regional haze should be 
expanded to include those in the pilot scale testing phase, because 
these guidelines will precede the installation of controls by about 10 
years. Other commenters believed that the discussion of technical 
feasibility introduced terms and concepts that were not clear, for 
example, what is meant by ``commercial demonstration.'' One commenter 
raised issues with deeming technologies used in foreign countries 
``available'' unless their performance has been demonstrated in the 
United States. A few commenters expressed concern with the provision in 
the guidelines that new technologies should be considered up to the 
time of a State's public comment period on the BART determination. The 
commenter believed that this could create an endless review loop for 
States if new technologies continually became available.
    Final rule. In the final guidelines, we have largely retained the 
language that was in the proposed guidelines. Because the guidelines 
call for consideration of technologies that become available by the 
time of the State's public comment process on the BART determination, 
technologies should be considered that become available well after we 
finalize the BART guidelines. We also note, for clarity, that the 
Guidelines state that technologies need to be both licensed and 
commercially available (i.e. commercially demonstrated and sold).
2. How Should the Costs of Control Be Estimated in Step 4 of the BART 
Determination?
    Comments. This section of the guidelines remained unchanged between 
the 2001 proposal and the 2004 reproposal. Comments varied, ranging 
from questioning the reliance on EPA's OAQPS Control Cost Manual Fifth 
Edition, February 1996, EPA 453/B-96-001 (hereafter called the 
``Control Cost Manual'') to requesting that we not include the concept 
of incremental cost effectiveness in the guidelines. A commenter 
expressed concerns that incremental cost effectiveness calculations, 
the cost of implementing each succeeding control option, is too 
dependent on the number of interim options included in the analysis. 
Moreover, the commenter believed that incremental cost calculations 
increase the complexity of the analysis, and they also increase the 
possibility for inconsistent cost results.
    Final rule. We have finalized this section of the guidelines with 
some changes to how it was proposed. States have flexibility in how 
they caculate costs. We believe that the Control Cost Manual provides a 
good reference tool for cost calculations, but if there are elements or 
sources that are not addressed by the Control Cost Manual or there are 
additional cost methods that could be used, we believe that these could 
serve as useful supplemental information.
    In addition, the guidelines continue to include both average and 
incremental costs. We continue to believe that both average and 
incremental costs provide information useful for making control 
determinations. However, we believe that these techniques should not be 
misused. For example, a source may be faced with a choice between two 
available control devices, control A and control B, where control B 
achieves slightly greater emission reductions. The average cost (total 
annual cost/total annual emission reductions) for each may be deemed to 
be reasonable. However, the incremental cost (total annual 
costA-B/total annual emission reductionsA-B) of 
the additional emission reductions to be achieved by control B may be 
very great. In such an instance, it may be inappropriate to choose 
control B, based on its high incremental costs, even though its average 
cost may be considered reasonable.
    Finally, it is important to note that, while BART determinations 
are focused at individual sources, it is likely that in response to SIP 
requirements, States will be making BART determinations for many units 
in a subject source category all at the same time. In doing so, States 
are likely to compare costs across each source category as well as 
looking at costs for individual units in order to respond to SIP 
requirements in an efficient manner (from the State's perspective).
3. How Should ``Remaining Useful Life'' Be Considered in Step 4 of the 
BART Determination?
    Comments. We received a number of comments on the issue of 
remaining useful life, both on the 2001 proposal and on the 2004 
reproposal. One commenter asserted that remaining useful life should 
not be considered in the cost analysis and that if a source is in 
operation at the time of a State's SIP submittal, it must have plans to 
install controls. Other commenters believed that, to the extent that 
assertions regarding a plant's remaining useful life influences the 
BART decision, there must be an enforceable requirement for the plant 
to shut down by that date. Other comments questioned whether Congress 
intended enforceable restrictions in order to take into account the 
remaining useful life and whether EPA had the authority under the CAA 
to require plant shutdowns.
    A number of comments were received regarding our request for 
comments on how to provide flexibility for situations where market 
conditions change. Some comments interpreted this provision as a 
loophole that would allow sources to continue operation for a number of 
years without BART. Another comment supported the concept of allowing a 
source to later change its mind, so long as BART is installed.
    Final rule. We have retained the approach in the proposed 
guidelines, including the provision for flexibility for sources to 
continue operating, with BART in place, should conditions change. We 
believe that the CAA mandates consideration of the remaining useful 
life as a separate factor, and that it is appropriate to consider in 
the analysis the effects of remaining useful life on costs. We believe 
that, because the source would not be allowed to operate after the 5-
year point without such controls, the option for providing flexibility 
would not create a loophole for sources. Moreover, any source operating 
after this point without BART controls in place would be subject to 
enforcement actions for violating the BART limit. For any source that 
does not agree to shut down before the 5-year point, the State should 
identify a specific BART emission limit that would apply after this 
point in time.
4. How Should ``Visibility Impacts'' Be Considered in Step 5 of the 
BART Determination?
    Background. The fifth statutory factor addresses the degree of 
improvement in

[[Page 39128]]

visibility which may reasonably be anticipated to result from the use 
of the ``best control technology'' for sources subject to BART. The 
2004 reproposal focuses on the use of single source emissions modeling 
to evaluate the BART control options. As part of the BART 
determination, we proposed that a State or individual source would run 
CALPUFF, or another EPA-approved model, to estimate, in deciviews, a 
BART source's visibility impact at a Class I area. The source would run 
the model once using its allowable emission rates, and then again at 
the various post-control emissions rates being evaluated for the BART 
determination. The 24-hour model results would then be tabulated for 
the pre- and post-control scenarios, for the average of the 20 percent 
worst modeled days at each receptor, over the time period of 
meteorology modeled. The difference in the averages for each receptor 
is the expected degree of improvement in visibility. Alternatively, the 
proposal requested comment on the option of using the hourly modeled 
impacts from CALPUFF at each receptor and determining the improvement 
in visibility based on the number of hours above the 0.5 deciview 
threshold for both the pre- and post-control model runs. We also 
requested comment on combinations of the proposed and alternative 
options and on the use of the simpler screening version of CALPUFF to 
do the analysis.
    Comments. Several environmental groups said that issues relating to 
the determination of visibility improvement for evaluating BART 
controls are in many ways the same as for determining which BART-
eligible sources are subject to BART. Thus, the commenter pointed out, 
the issues concerning the BART applicability test, discussed in section 
D., are all equally applicable here, including comments on: using the 
0.5 deciview threshold on an aggregate basis for determining visibility 
impairment and potential exemption for BART-eligible sources, use of a 
natural visibility baseline versus current visibility, using a 
substantially lower deciview threshold than 0.5 deciviews to determine 
the contribution to visibility impairment by an individual source, and 
demonstration of those thresholds by means of appropriate modeling 
rather than other less reliable and more subjective techniques.
    An industry commenter claimed that the American Corn Growers case 
emphasized the fact that the CAA clearly provides that BART 
determinations should balance the visibility benefits of controls 
comprehensively against their burdens; the commenter noted that this is 
not mentioned in our proposal; the commenter said that although the 
proposal would allow States to run the CALPUFF model, it fails to 
specify how they might consider the results.
    One State commenter opposed the use of visibility modeling for the 
purpose of informing the choice of control option, stating that it is 
unnecessary, confusing and without adequate standards or guidance for 
implementation. The State added that the analysis of control options in 
the BART process should yield the greatest, most cost-effective control 
efficiency for NOX and SO2 at or above our 
presumptive levels of control. Moreover, it said that analysis of the 
degree of visibility improvement may result in very small increments of 
visibility improvements within Class I areas from an individual source, 
thus tilting the selection to the lower control efficiency option. The 
State added that we should remove this criterion from the analysis to 
ensure that the best cost effective controls will result. Another State 
agency said that modeling impacts should not be considered in BART 
determinations because they are not considered when determining BACT 
for the PSD program.
    A variety of commenters pointed out several areas where the 
guidelines should be improved or clarified in regard to the degree of 
visibility improvement determination:
     We should clarify that the analysis is pollutant-specific 
(e.g., the modeling evaluation of a BART control option for 
SO2 reduction should not be combined with the modeling 
evaluation of a BART control option for NOX.)
     We should clarify that only the closest Class I area must 
be modeled.
     We should describe CALPUFF as one possible model to use, 
rather than as the only model that may be used.
     States and sources should have the flexibility to perform 
multiple modeling runs based on different levels of available control.
     Predicted visibility improvements that are imperceptible 
should be given no weight in determining the level of control that 
constitutes BART.
     States should be allowed to establish a factor for the 
required degree of visibility improvement.
    Several industry and utility commenters expressed concern about 
using allowable emission rates to predict visibility impacts for BART 
control options; they argued that actual emission rates should be 
considered instead. Three commenters stated that we must make clear 
that States should use emission rates that will be permissible at the 
time BART controls take effect, not current emissions rates.
    Additional comments from utilities, industry, and one State opposed 
the approach wherein the results from the 20 percent worst modeled days 
(pre- and post-control) were used to evaluate the visibility 
improvements expected from the various control options. Some believed 
this was too stringent, while others said it was not stringent enough. 
Two utilities added that the criteria should use the 20 percent worst 
days based on monitored data, not modeled data. An environmental group 
stated that sources should not be limited to just the worst days, but 
the improvements should be based upon controls reducing visibility 
impairment on any day. The commenter added that this rationale ignores 
the middle 60 percent of days in which visibility may worsen, because 
sources may increase emissions on these days as a trade-off for cutting 
emissions on the worst days. The commenter further argued that there 
are no data to support our assertion that improvement on the worst days 
means improvement on other days. They noted that default ``natural 
condition'' deciview values for Class I areas in our natural conditions 
guidance exist only for the average of the 20 percent best and worst 
days. The commenter added that we used the average default natural 
conditions (for the 20 percent best days) for the visibility impairment 
analysis, but there are no default ``maximum 24-hour'' values in the 
guidance.
    Nine commenters supported implementation of visibility improvement 
thresholds, which were not proposed in 2004. A State commenter said it 
is unclear how the modeled net visibility improvement would be 
specifically utilized in the BART analysis, and requested a target 
level of improvement or a de minimis level by which to measure 
improvement. Two industry commenters suggested alternatives to the 24-
hour value. One said that setting a threshold for comparison, as in the 
BART-applicability test, is more appropriate than the overall 
comparison of the 20 percent worst case days, and that the threshold 
for comparison should be on at least a daily average (or longer), not 
an hourly average, due to the possibility of short-term spikes based on 
certain meteorological conditions.
    These commenters also said that a comparison of the number of days 
above or below a certain threshold is preferable since below a certain 
threshold, the impacts of visibility are not perceptible; unlike 
concentration

[[Page 39129]]

levels of certain pollutants (i.e., ozone) which do not have a 
threshold below which there are no effects, there are concentration 
levels of particulate below which there is no visibility impact. They 
also asserted that comparing the number of days would allow for a more 
complete picture of how controls would potentially improve visibility. 
As noted previously, a small number of unusual meteorological 
conditions can produce significant spikes on a single day or days. 
Since the overall goal of the regional haze rule is long-term 
visibility improvement, they said that a comparison of the total number 
of days exceeding a threshold over multiple years will provide a better 
overall indicator of visibility improvement. One commenter suggested 
that if we retain the maximum 24-hour value for the visibility 
impairment analysis, we should at least allow the use of only 1 year, 
rather than 5 years, of meteorological data. That would simplify the 
modeling and would lessen the chance that one day with atypical, 
extreme conditions would dictate the result.
    One FLM supported our proposed method to determine visibility 
improvement associated with installation of BART. However, with regard 
to the use of hourly data instead of 24 hour data for the degree of 
visibility improvement assessment, another FLM said that while hourly 
model data are, by their nature, less reliable in predicting actual 
conditions, a measure that reports the total number of hours above a 
given threshold would still be a useful measure of the long-term effect 
of BART control. They said we should require States to report a 
combination of measures of the visibility improvement expected from 
BART. Such measures would be the change in the 20 percent worst days as 
well as a metric that examines the amount of time during a year that 
the source's visibility impact would exceed a threshold with and 
without BART.
    Another utility commenter added that, if a BART control option 
would result in no perceptible improvement in visibility at a Class I 
area, then it is not a cost-effective option. This commenter said that 
based on Pitchford and Malm (1994) \50\ and Henry (2002) \51\ a 2 
deciview threshold of perception would be appropriate, with a 1 
deciview threshold providing a margin of safety. Another commenter said 
that we should clarify that visibility improvement differences among 
BART control options should be considered insignificant if the 
differences are less than the perceptibility threshold level, which 
should be set in excess of 1 deciview. Other commenters said the 
minimum threshold should be 1 deciview.
---------------------------------------------------------------------------

    \50\ Pitchford, M. and Malm, W., ``Development and Applications 
of a Standard Visual Index,'' Atmospheric Environment, V. 28, no. 5, 
March 1994.
    \51\ Henry, R.C. ``Just-Noticeable Differences in Atmospheric 
Haze'', Journal of the Air & Waste Management Association, 52:1238-
1243, October 2002.
---------------------------------------------------------------------------

    Final Rule. We disagree with the comment that modeling should not 
be part of a BART review because it is not considered for BACT. CAA 
section 169A(g)(2) clearly requires an evaluation of the expected 
degree of improvement in visibility from BART controls. All five 
statutory factors, including cost-effectiveness and expected visibility 
improvement, should be reflected in the level of BART control that the 
State implements. We believe that modeling, which provides model 
concentration estimates that are readily converted to deciviews, is the 
most efficient way to determine expected visibility improvement.
    For the purposes of determining visibility improvement, States may 
evaluate visibility changes on a pollutant-specific basis. If expected 
improvement is shown from the various control choices, the State can 
weigh the results with the other four BART determination factors when 
establishing BART for a particular source. For example, a State can use 
the CALPUFF model to predict visibility impacts from an EGU in 
examining the option to control NOX and SO2 with 
SCR technology and a scrubber, respectively. A comparison of visibility 
impacts might then be made with a modeling scenario whereby 
NOX is controlled by combustion controls. If expected 
visibility improvements are significantly different under one control 
scenario than under another, then a State may use that information, 
along with information on the other BART factors, to inform its BART 
determination.
    Even though the visibility improvement from an individual source 
may not be perceptible, it should still be considered in setting BART 
because the contribution to haze may be significant relative to other 
source contributions in the Class I area. Thus, we disagree that the 
degree of improvement should be contingent upon perceptibility. Failing 
to consider less-than-perceptible contributions to visibility 
impairment would ignore the CAA's intent to have BART requirements 
apply to sources that contribute to, as well as cause, such impairment.
    Although we are not requiring States to use allowable emission 
rates to predict the anticipated future visibility impacts of BART 
controls, we disagree that daily average actual emission rates should 
be used to make this assessment. Emissions from a source can vary 
widely on a day to day basis; during peak operating days, the 24-hour 
actual emission rate could be more than double the daily average. On 
the other hand, in the long term, estimating visibility impacts based 
on allowable emission rates for every hour of the year may unduly 
inflate the maximum 24 hour modeled impairment estimate from a BART-
eligible source. The emissions estimates used in the models are 
intended to reflect steady-state operating conditions during periods of 
high capacity utilization. We do not generally recommend that emissions 
reflecting periods of start-up, shutdown, and malfunction be used, as 
such emission rates could produce higher than normal effects than would 
be typical of most facilities. Where States have information on a 
source's daily emissions, an emission rate based on the maximum actual 
emissions over a 24 hour period for the most recent five years may be a 
more appropriate gauge of a source's potential impact as it would 
ensure that peak emission conditions are reflected, but would likely 
not overestimate a source's potential impact on any given day. We have 
accordingly included this change to the final guidelines. We recommend 
that the State use the highest 24-hour average actual emission rate, 
for the most recent three or five year period of meteorological data, 
to characterize the maximum potential benefit.
    Because each Class I area is unique, we believe States should have 
flexibility to assess visibility improvements due to BART controls by 
one or more methods, or by a combination of methods, and we agree with 
the commenters suggestions to do so. We believe the maximum 24-hour 
modeled impact can be an appropriate measure in determining the degree 
of visibility improvement expected from BART reductions (or for BART 
applicability). We have pointed out, however, that States should have 
flexibility when evaluating the fifth statutory factor. A State is 
encouraged to account for the magnitude, frequency, and duration of the 
contributions to visibility impairment caused by the source based on 
the natural variability of meteorology. These are important elements to 
consider as they would provide useful information on both the short 
term peak impact and long term average assessments which are critical 
in making the visibility assessment.
    We agree with the suggestion that the use of a comparison 
threshold, as is

[[Page 39130]]

done for determining if BART-eligible sources should be subject to a 
BART determination, is an appropriate way to evaluate visibility 
improvement. However, we believe the States have flexibility in setting 
absolute thresholds, target levels of improvement, or de minimis levels 
since the deciview improvement must be weighed among the five factors, 
and States are free to determine the weight and significance to be 
assigned to each factor. For example, a 0.3, 0.5, or even 1.0 deciview 
improvement may merit stronger weighting in one case versus another, so 
one ``bright line'' may not be appropriate.
    In addition, comparison thresholds can be used in a number of ways 
in evaluating visibility improvement (e.g. the number of days or hours 
that the threshold was exceeded, a single threshold for determining 
whether a change in impacts is significant, a threshold representing an 
x percent change in improvement, etc.). In our example modeling 
analysis of a hypothetical source,\52\ we used three different 24-hour 
thresholds (1.0, 0.5, and 0.1 deciviews) and examined the number of 
days that those thresholds were exceeded for a source with a 90 percent 
change, for example, in SO2 emissions (i.e. 10,000 TPY and 
1,000 TPY). The number of days that the thresholds were exceeded in the 
10,000 TPY case was substantial, and the visibility improvement due to 
the reduction in emissions was dramatic (i.e. the number of days 
exceeding the thresholds dropped considerably).\53\
---------------------------------------------------------------------------

    \52\ CALPUFF Analysis in Support of the June 2005 Changes to the 
Regional Haze Rule, U.S. Environmental Protection Agency, June 15, 
2005, Docket No. OAR-2002-0076.
    \53\ Ibid.
---------------------------------------------------------------------------

    Other ways that visibility improvement may be assessed to inform 
the control decisions would be to examine distributions of the daily 
impacts, determine if the time of year is important (e.g. high impacts 
are occurring during tourist season), consideration of the cost-
effectiveness of visibility improvements (i.e. the cost per change in 
deciview), using the measures of deciview improvement identified by the 
State, or simply compare the worst case days for the pre- and post-
control runs. States may develop other methods as well.
5. In What Sequence Should Alternatives Be Assessed in Step 5 of the 
BART Determination?
    Background. Both the 2001 proposal and the 2004 reproposal 
requested comments on two options for evaluating the ranked options. 
Under the first option, States would use a sequential process for 
conducting the impacts analysis, beginning with a complete evaluation 
of the most stringent control option. If a State determines that the 
most stringent alternative in the ranking does not impose unreasonable 
costs of compliance, taking into account both average and incremental 
costs, the analysis begins with a presumption that this level is 
selected. Under this option, States would then proceed to consider 
whether energy and non-air quality environmental impacts would justify 
selection of an alternative control option. If there are no outstanding 
issues regarding energy and non-air quality environmental impacts, the 
analysis is ended and the most stringent alternative is identified as 
the ``best system of continuous emission reduction.'' If a State 
determines that the most stringent alternative is unacceptable due to 
such impacts, this approach would require them to document the 
rationale for this finding for the public record. Then, the next most-
effective alternative in the listing becomes the new control candidate 
and is similarly evaluated. This process would continue until the State 
identifies a technology which does not pose unacceptable costs of 
compliance, energy and/or non-air quality environmental impacts.
    We also requested comment on an alternative decision-making 
approach that would not begin with an evaluation of the most stringent 
control option. For example, States could choose to begin the BART 
determination process by evaluating the least stringent technically 
feasible control option or by evaluating an intermediate control option 
drawn from the range of technically feasible control alternatives. 
Under this approach, States would then consider the additional 
emissions reductions, costs, and other effects (if any) of successively 
more stringent control options. Under such an approach, States would 
still be required to (1) display all of the options and identify the 
average and incremental costs of each option; (2) consider the energy 
and non-air quality environmental impacts of each option; and (3) 
provide a justification for adopting the technology selected as the 
``best'' level of control, including an explanation of its decision to 
reject the other control technologies identified in the BART 
determination.
    In selecting a ``best'' alternative, the proposed guidelines 
included a discussion on whether the affordability of controls should 
be considered. As a general matter, for plants that are essentially 
uncontrolled at present and emit at much greater levels per unit of 
production than other plants in the category, we believe it is likely 
that additional control will be cost-effective. The proposed guidelines 
noted, however, that we recognize there may be unusual circumstances 
that justify taking into consideration the conditions of the plant and 
the economic effects of requiring the use of a given control 
technology. These effects would include effects on product prices, the 
market share, and profitability of the source. We did not intend, for 
example, that the most stringent alternative must always be selected if 
that level would cause a plant to shut down, while a slightly lesser 
degree of control would not have this effect.
    Comments. We received comments supporting both of the approaches 
for evaluating ranked control alternatives. Many commenters, including 
commenters from State agencies, were supportive of the first approach. 
Comments from State air quality agencies were strongly supportive of 
this approach. These commenters believed that this approach is 
consistent with past approaches by States for considering control 
options for case-by-case determinations, is well understood by all 
parties, and thus easier to implement. The first approach also was 
strongly supported in comments from environmental organizations and 
private citizens. Some comments noted that the plain terminology 
``best'' suggests that there must be a sound reason for not using the 
most stringent control level.
    Many comments from industrial trade organizations were critical of 
the first approach and believed that any requirement to use this 
approach would reduce State discretion because this approach, in the 
judgment of the commenters, would amount to use of the most stringent 
alternative as a default. Some of these comments asserted that the 
approach in option 1 would shift the BART analysis away from a cost-
benefit approach mandated by the CAA towards a BACT-like technology 
analysis. Other commenters believed that EPA should recognize that 
BART, as a control requirement for retrofitting existing sources, 
should differ from BACT or other controls for new equipment. A number 
of comments, in supporting the second approach, believed that this 
approach provides greater consideration of the incremental cost of each 
succeeding option.
    Final rule. In the final guidelines, we have decided that States 
should retain the discretion to evaluate control options in whatever 
order they choose, so long as the State explains its analysis of the 
CAA factors. We agree with

[[Page 39131]]

commenters who asserted that the method for assessing BART controls for 
existing sources should consider all of the statutory factors.
6. What Should Be the Presumptive Limits for SO2 and 
NOX for Utility Boilers?
    Background. In the 2004 reproposal, we proposed that States, as a 
general matter, should require EGUs greater than 250 MW in size at 
power plants larger than 750 MW to control 95 percent of their 
SO2 emissions, or control to within an SO2 
emission range of 0.1 to 0.15 lb/mmBtu. We also proposed to establish a 
rebuttable presumption that States should impose these BART 
SO2 limits on all EGUs greater than 250 MW, regardless of 
the size of the power plant at which they are located.
    For NOX, we proposed that sources currently using 
controls such as SCRs to reduce NOX emissions during part of 
the year should be required to operate those controls year-round. For 
power plants without post-combustion controls, we proposed to establish 
a presumptive emissions limit of 0.20 lbs/mmbtu for EGUs greater than 
250 MW in size. We requested comment on the rate of NOX 
emissions that can be achieved with combustion modifications on 
specific types of boilers. Many commenters responded both in favor and 
in opposition to these proposed BART presumptive limits.
    Comments. A number of utility groups said the presumptive 
SO2 emissions control approach inappropriately ignores the 
need for a visibility impact evaluation which is required in step 5 of 
the proposed case-by-case BART engineering analysis. They said that 
setting presumptive limits infringes on a state's authority to 
establish BART on a case-by-case basis considering not only visibility 
improvement, but the other statutory factors as well. The commenters 
said that visibility is both Class I area and source specific, which is 
the reason Congress gave the States the lead role and discretion in the 
BART program to determine which sources need to install or upgrade 
controls. Through the use of presumptions and default values, however, 
our prescriptive process, as proposed, would make the installation of 
maximum controls more likely without regard to visibility benefits. 
Instead, they argued, we should give the states maximum flexibility to 
use the five statutory factors in their BART determinations. Commenters 
said sources must be allowed to assess the visibility improvements of a 
variety of control options.
    Several utilities raised concern that sources with existing 
controls should not be required to meet the presumptive limits without 
the chance to evaluate the degree of visibility improvement expected 
from the additional emission reduction requirements. They said that if 
a source can demonstrate a reduction in visibility impairment below the 
specified threshold (whether that threshold is our currently proposed 
0.5 deciview or an alternative level) with less stringent controls, 
then neither we nor States should impose, by default, more stringent 
reduction requirements.
    Commenters from industry, utilities, and States said that we had 
not indicated what previously-controlled sources must do to comply with 
BART, while we had determined what controls are necessary for 
uncontrolled sources. They were concerned that the guidelines would 
lead States to require previously-controlled sources to remove the 
controls and replace them with even newer controls at great cost and 
very little, if any, improvement in emission levels and visibility in 
Class I areas. Commenters added that States should be able to use their 
discretion to determine whether additional controls are needed.
    Some commenters were concerned that the proposed rule would require 
some plants to install SCR to meet the NOX control level 
proposed, as the potential retrofit of SCR technology for the BART 
determination may be supported by the degree of visibility improvement 
expected. They said that the guidelines indicate that if a State finds 
that a source's visibility contribution warrants the installation of 
SCR, then SCR may be imposed. The commenter added, however, that the 
guidelines also need to provide for instances where the visibility 
condition warrants a lesser control level than what would be achieved 
by advanced combustion control; the commenter claimed there was 
reference to this concept in the preamble but not the guidelines.
    Final rule. In these guidelines, we are finalizing specific 
presumptive limits for SO2 and NOX for certain 
EGUs based on fuel type, unit size, cost effectiveness, and the 
presence or absence of pre-existing controls. The presumptive limits 
finalized in today's rulemaking reflect highly cost-effective 
technologies as well as provide enough flexibility for States to take 
particular circumstances into account.
    The presumptive limits apply to EGUs at power plants with a total 
generating capacity in excess of 750 MW. As explained in greater detail 
below, for these sources we are establishing a BART presumptive 
emission limit for coal-fired EGUs greater than 200 MW in size without 
existing SO2 control. These EGUs should achieve either 95 
percent SO2 removal, or an emission rate of 0.15 lb 
SO2/mmBtu, unless a State determines that an alternative 
control level is justified based on a careful consideration of the 
statutory factors. For NOX, we are establishing a set of 
BART presumptive emission limits for coal-fired EGUs greater than 200 
MW in size based upon boiler size and coal type, and based upon whether 
selective catalytic reduction (SCR) or selective noncatalytic reduction 
(SNCR) are already employed at the source. See section d. below for a 
table listing those specific limits. Based on our analysis of emissions 
from power plants, we believe that applying these highly cost-effective 
controls at the large power plants covered by the guidelines would 
result in significant improvements in visibility and help to ensure 
reasonable progress toward the national visibility goal.
    States, as a general matter, must require owners and operators of 
greater than 750 MW power plants to meet these BART emission limits. We 
are establishing these requirements based on the consideration of 
certain factors discussed below. Although we believe that these 
requirements are extremely likely to be appropriate for all greater 
than 750 MW power plants subject to BART, a State may establish 
different requirements if the State can demonstrate that an alternative 
determination is justified based on a consideration of the five 
statutory factors.
    In addition, while States are not required to follow these 
guidelines for EGUs located at power plants with a generating capacity 
of less than 750 MW, based on our analysis detailed below, we believe 
that States will find these same presumptive controls to be highly-cost 
effective, and to result in a significant degree of visibility 
improvement, for most EGUs greater than 200 MW, regardless of the size 
of the plant at which they are located. A State is free to reach a 
different conclusion if the State believes that an alternative 
determination is justified based on a consideration of the five 
statutory factors. Nevertheless, our analysis indicates that these 
controls are likely to be among the most cost-effective controls 
available for any source subject to BART, and that they are likely to 
result in a significant degree of visibility improvement.
    The rest of this section discusses these presumptive limits for 
SO2 and NOX for EGUs and the additional

[[Page 39132]]

visibility impact and cost-effectiveness analyses we have performed 
since proposal of the guidelines in 2004.
    a. Visibility Analysis for SO2 and NOX 
Emissions From EGUs. In the 2004 reproposal, our preliminary CALPUFF 
modeling \54\ suggested that controlling a single 250 MW EGU at a 90 
percent level would improve visibility substantially from that source. 
Based on the expected degree of improvement in visibility and the use 
of highly effective control technologies that are available for sources 
of this capacity and greater, we concluded that the specific control 
levels in the proposal were appropriate. Even at that level of control 
however, our analysis indicated that emissions from the source might 
still cause a perceptible impact on visibility.
---------------------------------------------------------------------------

    \54\ Summary of Technical Analyses for the Proposed Rule, Mark 
Evangelista, U.S. Environmental Protection Agency, April 12, 2004, 
Docket No. OAR-2002-0076.
---------------------------------------------------------------------------

    Following comments that we had ignored the need to consider the 
degree of improvement in visibility which could reasonably be 
anticipated from the use of the presumptive control technologies, we 
undertook a more comprehensive modeling analysis of the anticipated 
visibility impacts of controlling large EGUs. Based on this modeling 
analysis, we anticipate that a majority of the currently uncontrolled 
EGUs at power plants covered by the guideline are predicted to have 24-
hour maximum impacts of greater than a change of 2 or 3 deciviews.\55\ 
Our modeling examples included scenarios that were representative of 
typical EGUs, but, in our first hypothetical run 1, we 
conservatively assumed SO2 emissions of 10,000 tons per year 
(TPY) and NOX emissions of approximately 3,500 TPY.\56\ Such 
levels of emissions are well below those that may be expected of an 
uncontrolled 200 MW EGU. The number of days during any year that such 
sources are predicted to have visibility impacts of greater than 0.5 
deciviews or even 1.0 deciview were 29 days and 12 days on average, 
respectively, at 50 km from a hypothetical Class I area in the East; if 
the 98th percentile were considered, there would be five days above a 
1.0 deciview change.
---------------------------------------------------------------------------

    \55\ CALPUFF Analysis in Support of the the June 2005 Changes to 
the Regional Haze Rule, U.S. Environmental Protection Agency, June 
15, 2005, Docket No. OAR-2002-0076.
    \56\ Ibid.
---------------------------------------------------------------------------

    The modeled emission rates in the example were conservative; for 
much larger EGUs with capacities of 750 MW or more, and emission rates 
much higher than those which were modeled, visibility degradation is 
expected to be far worse. Clearly there is a substantial degree of 
visibility improvement which is likely from emission reductions at 
these sources.
    Although we are confident that the EGUs for which we are 
establishing presumptive limits each have a significant impact on 
visibility at one or more Class I areas, a State retains the option and 
flexibility to conduct its own analysis or allow a source to 
demonstrate that it should not be subject to BART (based on its 
visibility effects).
    b. BART Presumptive Limits for SO2 From Coal-Fired 
Units. For currently uncontrolled coal-fired EGUs greater than 200 MW 
in size located at power plants greater than 750 MW, we are 
establishing a presumptive BART limits of 95 percent SO2 
removal, or an emission rate of 0.15 lb SO2/mmBtu. We are 
not establishing a presumptive limit for EGUs with existing post-
combustion SO2 controls or for EGUs that burn oil.
    In 2004, we proposed presumptive limits for SO2 of 95 
percent control or a comparable performance level of 0.1 to 0.15 lbs 
per million BTU as controls that would be achievable and cost-
effective. We requested comment on the removal effectiveness of flue 
gas desulfurization (``FGD'' or ``scrubber'' controls) for various coal 
types and sulfur content combinations. Having considered the comments 
received, we have determined that there is ample data to support the 
determination that the BART presumptive limits outlined in today's 
action are readily achievable by new wet or semi-dry FGD systems across 
a wide range of coal types and sulfur contents based on proven scrubber 
technologies currently operational in the electric industry.\57\
---------------------------------------------------------------------------

    \57\ Technical Support Document for BART SO2 Limits for Electric 
Generating Units, Memorandum to Docket OAR 2002-0076, April 1, 2005.
---------------------------------------------------------------------------

    We agree with the commenters who stated that our dual 
recommendation provided equity across sources burning coals of varying 
sulfur content. We believe the presumptive limits provide enough 
flexibility that absent unique circumstances, any BART-eligible coal-
fired EGU will be able to achieve one of the limits with a new FGD 
system. We expect that BART-eligible EGUs burning medium to high sulfur 
coal will be able to achieve a removal efficiency of 95 percent in a 
cost effective manner by utilizing various wet FGD technologies, and 
that those EGUs burning lower sulfur coals could meet the emission 
limit of 0.15lb/mmBtu in a cost effective manner by utilizing dry FGD 
technologies. As described below, EPA's unit specific economic modeling 
showed that the majority of BART eligible units greater than 200 MW can 
meet the presumptive BART limit at a cost of $400 to $2000 per ton of 
SO2 removed.
    Some commenters expressed concerns that the proposed limits were 
too stringent in particular for: (1) EGUs less than 750 MW in size, (2) 
EGUs burning low sulfur coals, and (3) EGUs burning lignite coals. 
However, numerous examples exist of smaller EGUs and EGUs burning low 
sulfur or lignite coals achieving these SO2 limits at 
reasonable cost.\58\ We recognize that semi-dry FGD systems are most 
commonly utilized on units burning lower sulfur coals and are not 
typically designed for removal efficiencies of 95 percent or greater. 
However, we believe that most of these EGUs can readily achieve the 
presumptive emission rate limit of 0.15 lb SO2/mmBtu. An 
analysis of EPA's RACT/BACT/LEAR Clearinghouse Dry FGD cost 
effectiveness data ranged from $393 to $2132 per ton SO2 
removed, with an average cost effectiveness of $792 per ton.\59\
---------------------------------------------------------------------------

    \58\ Ibid.
    \59\ Summary of BART Source Analyses, Memorandum from Bill 
Balcke and Doran Stegura, Perrin Quarles Associates, Inc., to Chad 
Whiteman, EPA March 24, 2003. See 2001 emissions data in BART AR 
file, attached.
---------------------------------------------------------------------------

    We received a few comments expressing the belief that the 
presumptive limits should be more stringent, given that BART emission 
limits will not be fully implemented until 2013 or 2014. We recognize 
that while some scrubber units currently achieve reductions greater 
than 95 percent, not all units can do so. The individual units that 
currently achieve greater than 95 percent control efficiencies do not 
necessarily represent the wide range of unit types across the universe 
of BART-eligible sources. An analysis of the Department of Energy's 
U.S. FGD Installation Database supports our belief that 95 percent 
removal efficiencies would be obtainable by all types of EGUs burning 
medium and high sulfur coal by 2014, including BART-eligible EGUs. In 
addition, we note that the presumption does not limit the States' 
ability to consider whether a different level of control is appropriate 
in a particular case. If, upon examination of an individual EGU, a 
State determines that a different emission limit is appropriate based 
upon its analysis of the five factors, then the State may apply a more 
or less stringent limit.
    Our analysis of presumptive BART limits accounted for variations in 
existing SO2 controls. We accordingly considered (1) coal-
fired EGUs without

[[Page 39133]]

existing SO2 controls, and (2) coal-fired EGUs with existing 
SO2 controls. This analysis consisted of the following key 
elements: (1) Identification of all potentially BART-eligible EGUs, and 
(2) technical analyses and industry research to determine applicable 
and appropriate SO2 control options, (3) economic analysis 
to determine cost effectiveness for each potentially BART-eligible EGU, 
and (4) evaluation of historical emissions and forecast emission 
reductions for each potentially BART-eligible EGU.\60\
---------------------------------------------------------------------------

    \60\ Ibid.
---------------------------------------------------------------------------

    We identified 491 potentially BART-eligible coal-fired units based 
on the following criteria: (1) The unit was put in place between August 
7, 1962 and August 7, 1977, and (2) the unit had the potential to emit 
more than 250 tons annually of SO2. Our assessment of 
potential controls included various industry case studies, technical 
papers, public comments, BACT analyses, and historical Acid Rain 
emissions data. Our analysis is described in detail in the TSD.\61\
---------------------------------------------------------------------------

    \61\ Ibid.
---------------------------------------------------------------------------

    We calculated cost effectiveness and projected SO2 
emission reductions on a per unit basis based on removal efficiencies 
of 90 percent for dry FGD systems, in particular spray dry lime 
systems, and 95 percent for wet FGD systems, in particular limestone 
forced oxidation systems. Based on our analysis, the average cost 
effectiveness for controlling all BART-eligible EGUs greater than 200 
MW without existing SO2 controls was estimated to $919 per 
ton of SO2 removed. Moreover, the range of costs 
effectiveness numbers demonstrates that the majority of these units can 
meet the presumptive limits at a cost of $400 to $2000 per ton of 
SO2 removed.

                                                    Figure 1
----------------------------------------------------------------------------------------------------------------
                                                                               Calculated         Percent of
                                                         Percent of BART      average cost         estimated
        Unit capacity  (MW)          Tons (K) of SO2     eligible coal-    effectiveness for  removable BART SO2
                                     emitted in 2001    fired unit's 2001   MW grouping  ($/    emissions from
                                                            emissions       ton SO2 removed)   coal-fired units*
----------------------------------------------------------------------------------------------------------------
<50 MW............................                 26                 0.4               1962                 0.9
50-100 MW.........................                 93                 1.4               2399                 1.6
100-150 MW........................                171                 2.5               1796                 2.2
150-200 MW........................                235                 3.5               1324                 3.4
200-250 MW........................                253                 3.8               1282                 3.1
250-300 MW........................                281                 3.2               1128                 4.0
>300 MW...........................               5712                85.2  .................                84.8
All Units.........................               6707               100                  984               100
BART Units (>200MW)...............               6246                92.2                919                91.9
----------------------------------------------------------------------------------------------------------------

    In establishing presumptive BART limits, we were cognizant of the 
fact that upgrading an existing scrubber system is typically considered 
more cost effective than constructing a new scrubber system. However, 
due to the diverse and complex nature of upgrading existing FGD systems 
(scrubber type, reagents, online year, absorber characteristics, 
current operating procedures, etc.), there is no single solution or 
standard appropriate for all EGUs. As a result, we are not including 
specific numerical presumptive limits for EGUs with pre-existing 
scrubbers. However, for scrubbers currently achieving removal 
efficiencies of at least 50 percent, we recommend States evaluate a 
range of scrubber upgrade options available for improving the 
SO2 removal performance of existing units. There are 
numerous scrubber enhancements available to upgrade the average removal 
efficiencies of all types of existing scrubber systems, and the 
guidelines contains a discussion of the options that States should 
evaluate in making BART determinations for EGUs with existing 
scrubbers.
    The guidelines do not require EGUs with existing FGD systems to 
remove these controls and replace them with new controls, but the 
guidelines do state that coal fired EGUs with existing SO2 
controls achieving removal efficiencies of less than 50 percent should 
consider constructing a new FGD system to meet the presumptive limits 
of 95 percent removal or 0.15 lb/mmBtu in addition to evaluating the 
suite of upgrade options. For these EGUs, the suite of available 
``upgrades'' may not be sufficient to remove significant SO2 
emissions in a cost effective manner, and States may determine that 
these EGUs should be retrofitted with new FGD systems.
    c. BART Limits for SO2 From Oil-Fired Units. We are not 
establishing a presumptive BART limit for SO2 from oil-fired 
EGUs. The guidelines state that the most appropriate control option for 
oil-fired EGUs, regardless of capacity, is to set limits on the sulfur 
content of the fuel oil burned in the unit.
    Commenters suggested EPA evaluate two primary control options for 
BART oil-burning units: (1) Sulfur content fuel oil limitations, and 
(2) flue gas desulfurization systems. We have been unable to find any 
FGD application in the U.S. electric industry on an oil-fired unit. As 
a result, our analysis for oil-fired units focused on benchmarking 
previously imposed fuel oil restrictions on the electric industry and 
(2) a regional economic analysis of switching from high sulfur to low 
sulfur fuel oil.
    Our study of currently imposed fuel oil restrictions on the 
electric industry suggested that all BART-eligible EGUs currently have 
some sort of imposed sulfur content or emission rate limitation. Of the 
74 BART-eligible oil-burning EGUs, 32 currently have sulfur fuel oil 
restrictions of less than 1 percent, and 67 have some sort of sulfur 
content limitation. In addition, our economic analysis suggests that 
switching to low sulfur fuel oil is a cost effective method in reducing 
SO2 emission from oil fired units.
    As approximately 43 percent of the BART eligible oil units 
currently have a sulfur content limitation that is either equivalent 
to, or more stringent than, one percent sulfur by weight, the 
guidelines require States to consider a one percent or lower sulfur by 
weight fuel oil restriction on all BART eligible EGUs as part of their 
BART analysis, and recommends that States establish appropriate and 
sustainable sulfur content fuel oil restrictions, taking into

[[Page 39134]]

account fuel oil availability. States should accordingly evaluate a one 
percent sulfur content limitation as a starting point of their BART 
determination for oil-fired EGUs subject to BART.
    d. BART Presumptive Limits for NOX From Coal-fired Units. In the 
2004 reproposal, in discussing NOX controls on EGUs, we 
explained that there are two somewhat distinct approaches to reducing 
emissions of NOX at existing sources. One is to use 
combustion controls (including careful control of combustion air and 
low-NOX burners). The other approach is removal technology 
applied to the flue gas stream (such as SCRs and SNCRs).
    For EGUs currently using controls such as SCRs or SNCRs to reduce 
NOX during part of the year, we are establishing a 
presumption that use of these same controls year-round is BART. (Some 
commenters supported year-round operation of these controls. One 
commenter suggested the cost of year-round operation of SCRs would be 
significant. However, our analysis showed year-round operation of 
existing SCRs compared to operation during the 5-month ozone season 
only to be highly cost effective (average cost-effectiveness of $170 
per ton).) Although only a few BART-eligible sources currently have 
SNCRs installed, we note that States may wish to consider SCR as an 
alternative to annual operation of SNCR in light of the relatively high 
operating costs associated with SNCR.
    For sources without post-combustion controls (i.e., SCRs and 
SNCRs), we are establishing a presumption as to the appropriate BART 
limits for coal-fired units based on boiler design and coal type. These 
presumptions apply to EGUs greater than 200 MW at power plants with a 
generating capacity greater than 750 MW and are based on control 
strategies that are generally cost-effective for all such units.
    In 2004 we noted that, unlike the methods for controlling 
SO2 (which fall within a fairly narrow range of cost 
effectiveness and control efficiencies), the removal efficiencies and 
costs associated with the control techniques for NOX vary 
considerably, depending on the design of the boiler and the type of 
coal used. In response to comments on the proposal, we have performed 
additional analyses of all individual BART-eligible coal-fired units 
\62\ and our analyses indicated that both cost effectiveness and post-
control rates for NOX do depend largely on boiler design and 
type of coal burned. Based on these analyses, we believe that States 
should carefully consider the specific NOX rate limits for 
different categories of coal-fired utility units, differentiated by 
boiler design and type of coal burned, set forth below as likely BART 
limits.
---------------------------------------------------------------------------

    \62\ See Technical Support Document for BART NOX 
Limits for Electric Generating Units and Technical Support Document 
for BART NOX Limits for Electric Generating Units Excel 
Spreadsheet, Memorandum to Docket OAR 2002-0076, April 15, 2005.
---------------------------------------------------------------------------

    In today's action, EPA is setting presumptive NOX limits 
for EGUs larger than 750 MW. EPA's analysis indicates that the large 
majority of the units can meet these presumptive limits at relatively 
low costs. Because of differences in individual boilers, however, there 
may be situations where the use of such controls would not be 
technically feasible and/or cost-effective. For example, certain 
boilers may lack adequate space between the burners and before the 
furnace exit to allow for the installation of over-fire air controls. 
Our presumption accordingly may not be appropriate for all sources. As 
noted, the NOX limits set forth here today are presumptions 
only; in making a BART determination, States have the ability to 
consider the specific characteristics of the source at issue and to 
find that the presumptive limits would not be appropriate for that 
source.
    The table below indicates the types of boilers installed at the 491 
BART-eligible coal-fired EGUs. Dry-bottom wall-fired boiler units and 
tangentially-fired boiler units make up a large majority of the total 
BART-eligible EGUs.

                              Table 1.--Population of BART-Eligible Coal-Fired EGUs
----------------------------------------------------------------------------------------------------------------
                                                                 Number            Number            Number
                                                           -----------------------------------------------------
                        Boiler type                                                              Units > 200 MW
                                                                All units      Units > 200 MW   at 750 MW plants
----------------------------------------------------------------------------------------------------------------
Cyclone...................................................                56                35                19
Cell Burner...............................................                35                35                29
Dry Bottom--Wall fired....................................               188               121                77
Dry Bottom Turbo-fired....................................                14                10                 4
Stoker....................................................                 5                 0                 0
Tangentially-fired........................................               186               164               112
Wet Bottom................................................                 6                 5                 5
Other.....................................................                 1                 0                 0
                                                           -------------------
    Total BART-eligible coal-fired EGUs...................               491               370               246
----------------------------------------------------------------------------------------------------------------

    For all types of boilers other than cyclone units, the limits in 
Table 2 are based on the use of current combustion control technology. 
Current combustion control technology is generally, but not always, 
more cost-effective than post-combustion controls such as SCRs. For 
cyclone boilers, SCRs were found to be more cost-effective than current 
combustion control technology;\63\ thus the NOX limits for 
cyclone units are set based on using SCRs. SNCRs are generally not 
cost-effective except in very limited applications and therefore were 
not included in EPA's analysis. The types of current combustion control 
technology options assumed include low NOX burners, over-
fire air, and coal reburning.
---------------------------------------------------------------------------

    \63\ The current combustion control technology EPA analyzed for 
cyclone units is coal reburning.
---------------------------------------------------------------------------

    We are establishing presumptive NOX limits in the 
guidelines that we have determined are cost-effective for most units 
for the different categories of units below, based on our analysis of 
the expected costs and performance of controls on BART-eligible units 
greater than 200 MW. We assumed that coal-fired EGUs would have space 
available to install separated over-fire air. Based on the large number 
of units of various boiler designs that have installed separated over-
fire air, we believe this assumption to be reasonable. It is

[[Page 39135]]

possible, however, that some EGUs may not have adequate space 
available. In such cases, other NOX combustion control 
technologies could be considered such as Rotating Opposed Fire Air 
(``ROFA''). The limits provided were chosen at levels that 
approximately 75 percent of the units could achieve with current 
combustion control technology. The costs of such controls in most cases 
range from just over $100 to $1000 per ton. Based on our analysis, 
however, we concluded that approximately 25 percent of the units could 
not meet these limits with current combustion control technology. 
However, our analysis indicates that all but a very few of these units 
could meet the presumptive limits using advanced combustion controls 
such as rotating opposed fire air (``ROFA''), which has already been 
demonstrated on a variety of coal-fired units. Based on the data before 
us, the costs of such controls in most cases are less than $1500 per 
ton.
---------------------------------------------------------------------------

    \64\ No Cell burners, dry-turbo-fired units, nor wet-bottom 
units burning lignite were identified as BART-eligible, thus no 
presumptive limit was determined. Similarly, no wet-bottom units 
burning sub-bituminous were identified as BART-eligible.
    \65\ These limits reflect the design and technological 
assumptions discussed in the technical support document for 
NOX limits for these guidelines, e.g., EPA assumed space 
would be available for over-fire air. See Technical Support Document 
for BART NOX Limits for Electric Generating Units and 
Technical Support Document for BART NOX Limits for Electric 
Generating Units Excel Spreadsheet, Memorandum to Docket OAR 2002-
0076, April 15, 2005.

 Table 2.--Presumptive NOX Emission Limits for BART-Eligible Coal-Fired
                               Units \64\
------------------------------------------------------------------------
                                                         NOX presumptive
           Unit type                   Coal type        limit (lb/mmbtu)
                                                              \65\
------------------------------------------------------------------------
Dry-bottom wall-fired.........  Bituminous............              0.39
                                Sub-bituminous........              0.23
                                Lignite...............              0.29
Tangential-fired..............  Bituminous............              0.28
                                Sub-bituminous........              0.15
                                Lignite...............              0.17
Cell Burners..................  Bituminous............              0.40
                                Sub-bituminous........              0.45
Dry-turbo-fired...............  Bituminous............              0.32
                                Sub-bituminous........              0.23
Wet-bottom tangential-fired...  Bituminous............              0.62
------------------------------------------------------------------------


             Table 3.--Average Cost-Effectiveness of NOX Controls for BART-Eligible Coal-Fired Units
----------------------------------------------------------------------------------------------------------------
                                                                                Number units    National average
                Unit type                              Coal type                 nation-wide         ($/ton)
----------------------------------------------------------------------------------------------------------------
Dry-bottom wall-fired....................  Bituminous.......................               114              1229
                                           Sub-bituminous...................                66               576
                                           Lignite..........................                 3              1296
Tangential-fired.........................  Bituminous.......................               105               567
                                           Sub-bituminous...................                72               281
                                           Lignite..........................                 9               614
Cell Burners.............................  Bituminous.......................                32              1287
                                           Sub-bituminous...................                 3              1021
Dry-turbo-fired..........................  Bituminous.......................                 7               775
                                           Sub-bituminous...................                 7               599
Wet-bottom...............................  Bituminous.......................                 6               378
Cyclones (with SCR)......................  All..............................                56               900
----------------------------------------------------------------------------------------------------------------

    The advanced combustion control technology we used in our analysis, 
ROFA, is recently available and has been demonstrated on a variety of 
unit types. It can achieve significantly lower NOX emission 
rates than conventional over-fire air and has been installed on a 
variety of coal-fired units including T-fired and wall-fired units. We 
expect that not only will sources have gained experience with and 
improved the performance of the ROFA technology by the time units are 
required to comply with any BART requirements, but that more 
refinements in combustion control technologies will likely have been 
developed by that time. As a result, we believe our analysis and 
conclusions regarding NOX limits are conservative.\66\ For 
those units that cannot meet the presumptive limits using current 
combustion control technology, States should carefully consider the use 
of advanced combustion controls such as ROFA in their BART 
determination.
---------------------------------------------------------------------------

    \66\ See Technical Support Document for BART NOX Limits for 
Electric Generating Units and Technical Support Document for BART 
NOX Limits for Electric Generating Units Excel Spreadsheet, 
Memorandum to Docket OAR 2002-0076, April 15, 2005.
---------------------------------------------------------------------------

    A detailed discussion of our analysis is in the docket.\67\ For 
data on emissions and existing control technology in use at the BART-
eligible EGUs, we used EPA's Clean Air Markets Division database.\68\
---------------------------------------------------------------------------

    \67\ Id.
    \68\ Reporting requirements for the Acid Rain Program and 
NOX SIP Call affected sources, see 40 CFR 75 subpart G 
(parts 7562-64), and EPA Clean Air Markets Division Web site, data 
and maps page (http://www.epa.gov/airmarkets).
---------------------------------------------------------------------------

C. Selective Catalytic Reduction (``SCR'') and Cyclone Units

    We also analyzed the installation of SCRs at BART-eligible EGUs, 
applying SCR to each unit and fuel type. The cost-effectiveness was 
generally higher than for current combustion control technology except 
for one unit type, cyclone units. Because of the relatively high 
NOX emission rates of cyclone units, SCR is more cost-
effective. Our analysis indicated that the cost-effectiveness of 
applying SCR on coal-fired cyclone units is typically less than $1500 a 
ton, and that the average cost-

[[Page 39136]]

effectiveness is $900 per ton.\69\ As a result, we are establishing a 
presumptive NOX limit for cyclone units based on the use of 
SCR. For other units, we are not establishing presumptive limits based 
on the installation of SCR. Although States may in specific cases find 
that the use of SCR is appropriate, we have not determined that SCR is 
generally cost-effective for BART across unit types.
---------------------------------------------------------------------------

    \69\ See Technical Support Document for BART NOX Limits for 
Electric Generating Units and Technical Support Document for BART 
NOX Limits for Electric Generating Units Excel Spreadsheet, 
Memorandum to Docket OAR 2002-0076, April 15, 2005.
---------------------------------------------------------------------------

Oil and Gas-Fired Units
    For oil-fired and gas-fired units, we believe that installation of 
current combustion control technology is highly cost-effective and 
should be considered in determining BART for these sources. We 
performed an analysis of BART-eligible oil and gas-fired units similar 
to the analysis done for coal-fired units. Our analysis indicated that 
a number of units can make significant reductions in NOX 
emissions which are cost-effective through the application of current 
combustion control technology.\70\ However, for a number of units, the 
use of combustion controls does not appear to be cost-effective. As a 
result, we determined that it would be inappropriate to establish a 
general presumption regarding likely BART limits. As a result, the 
guidelines only indicate that States should consider the installation 
of current combustion control technology on oil and gas-fired units.
---------------------------------------------------------------------------

    \70\ Id.
---------------------------------------------------------------------------

IV. How Does Today's Rule Affect States Options for Using Alternative 
Strategies in Lieu of Source-by-Source BART?

Background

    Over the past several years, there have been a number of rule 
makings and court decisions on the subject of BART and BART-alternative 
programs. In order to understand today's actions, it is useful to again 
review the regulatory and litigation history, with a specific focus on 
BART-alternative issues.
    As noted in part I of this preamble, the 1999 regional haze rule 
included provisions for BART, codified at 40 CFR 51.308(e), and in 
definitions that appear in 40 CFR 51.301. Among these provisions was 
section 308(e)(2), allowing States to implement cap and trade programs, 
or other alternative programs, in lieu of BART. Section 308(e)(2) 
provided that trading program alternatives must be demonstrated to 
achieve greater reasonable progress than BART, and provided the general 
parameters for making this demonstration. Of particular relevance, 
section 308(e)(2) directed States, in the course of estimating 
emissions reductions anticipated from source-by-source BART, to 
determine what comprises BART based on the four non-visibility factors, 
and then estimate visibility improvements based on the application of 
BART to all sources subject to BART. In other words, section 308(e)(2) 
indicated that states should use what has since been termed a ``group 
BART'' approach to estimating the source-by-source BART benchmark, for 
comparison to the alternative program. Section (e)(2) did not prescribe 
the specific criteria to be used to compare the progress estimated from 
source-by-source BART to that anticipated from the trading program. The 
preamble discussion indicated that the comparison should be based on 
both emission reductions and visibility improvement, but did not 
provide further specificity. See 64 FR at 35741-35743.
    Specific criteria for making the comparison to programs was 
proposed in the BART Guidelines (40 CFR 51 App. Y) in 2001. These 
criteria--sometimes referred to as the ``better-than-BART test'' 
consist of the following. First, if the geographic distribution of 
emissions reductions from the two programs is expected to be similar, 
the comparison can be made based on emissions alone. Second, if the 
distribution of emissions reductions is anticipated to be significantly 
different, then a two-pronged visibility improvement test is employed. 
The first prong is that the alternative program must not result in a 
degradation of visibility at any Class I area. The second prong is that 
the alternative program must result in greater visibility improvement 
overall, based on an average across all affected Class I areas. See 66 
FR 38133.
    In 2002, the D.C. Circuit decided American Corn Growers. The court 
in that decision invalidated ``the BART provisions'' on the basis that 
EPA had improperly constrained State authority by requiring them to 
bifurcate visibility from the other statutory factors when making BART 
determinations, and by specifying that visibility impairment should be 
considered on a group basis when determining whether a BART eligible 
source is subject to BART. 291 F.3d 1, 8.
    Because EPA's policy of allowing alternative programs to BART was 
not at issue in American Corn Growers, the decision contained no 
discussion of how such alternative programs would be compared to BART--
neither the step of estimating emissions from source-by-source BART, 
nor the criteria for the actual comparison (i.e., the test). Therefore, 
EPA interpreted the court's vacature of the BART provisions to apply to 
the source-by-source BART regulations under 40 CFR 51.308(e)(1). 
Accordingly, in our May 2004 reproposal of the BART guidelines, we did 
not propose any changes in section 308(e)(2), and we retained the 
section on trading programs in the guidelines (Appendix Y) as that 
section was proposed in 2001.
    In June 2004, in the Supplemental Notice of Proposed Rulemaking 
(SNPR) for the Clean Air Interstate Rule (CAIR), we proposed to 
conclude that the CAIR will achieve greater reasonable progress than 
would BART for SO2 and NOX at BART-eligible EGUs 
in CAIR affected States and therefore may be treated as a program in 
lieu of BART for those sources. In doing so, we discussed regional haze 
rule section 308(e)(2) as precedent for the policy of allowing trading 
programs to substitute for BART.\71\ However, noting that the CAIR 
trading program affected only one category of BART-eligible sources 
(EGUs), rather than all BART-eligible categories as envisioned for 
State-developed BART-alternative programs under section 308(e)(2), we 
proposed adding a 308(e)(3) applicable only to CAIR. This section would 
provide that states that comply with the CAIR by subjecting EGUs to the 
EPA administered cap and trade program may consider BART satisfied for 
NOX and SO2 from BART-eligible EGUs. In the CAIR 
SNPR and supporting documentation,\72\ we provided analyses 
demonstrating that CAIR would achieve greater emission reductions than 
BART, and would make greater reasonable progress according to the two-
pronged visibility test previously proposed in the BART guidelines.
---------------------------------------------------------------------------

    \71\ Section 308(e)(2) was based, in turn, on the precedent set 
by our interpretation of CAA 169A(b)(2) in a single BART-source 
context--see 64 FR 35739, citing Central Arizona Water Conservation 
District, 990 F.2d 1531 (1993).
    \72\ ``Supplemental Air Quality Modeling Technical Support 
Document (TSD) for the Clean Air Interstate Rule (CAIR), May, 
2004.'' http://www.epa.gov/cair/pdfs/saqmtsd.pdf.
---------------------------------------------------------------------------

    In February 2005, in CEED v. EPA, the D.C. Circuit invalidated a 
BART-alternative program developed by the Western Regional Air 
Partnership (WRAP), which was also based on a requirement of group-BART 
analysis in setting source-by-source benchmark. It is important to note 
that the two-pronged better-than-BART test was not

[[Page 39137]]

at issue in CEED, as neither the States nor EPA had employed that test 
in determining that the WRAP's program achieved greater progress than 
BART. The issue on which the court based its decision was not how the 
two programs were compared, but how States were required to estimate 
reductions from source-by-source BART in order to make the comparison. 
The implications of this case to today's action are discussed in more 
detail below.
    Finally, on March 10, 2005 we promulgated the final CAIR. In the 
final CAIR, we presented refined and updated analyses continuing to 
show that CAIR makes greater progress than BART. We concluded at that 
time that we should defer a final ``better than BART'' determinations 
until (1) the source-by-source BART guidelines for EGU were 
promulgated, and (2) the criteria for comparing alternatives to BART 
were also finalized. We are taking both of those actions today, and, as 
explained below, are therefore also making our final determination that 
CAIR achieves greater progress than BART and may be used by States as a 
BART substitute.

Final Criteria for Comparing Visibility Progress of an Alternative 
Program to BART

    Proposed Rule. As noted, the criteria for determining if an 
alternative measure achieves greater reasonable progress than BART 
(also known as the ``better than BART'' test or the two- pronged 
visibility test) were first proposed in the 2001 BART guideline 
proposal and reproposed in the identical form in the 2004 BART 
guidelines reproposal. The test appeared as an element of the 
guideline's overview of the steps involved in developing a trading 
program consistent with regional haze rule section 308(e)(2).
    Specifically, the guidelines provided that States could first look 
at the geographic distribution of emissions under the trading program. 
``If [the] distribution of emissions is not substantially different 
than under BART, and greater emissions reductions are achieved, then 
the trading program would presumptively achieve ``greater reasonable 
progress.'' (69 FR at 25231). If the distribution of emissions is 
expected to be different, then States are directed to conduct an air 
quality modeling study. The guidelines then provide that

``[t]he modeling study would demonstrate ``greater reasonable 
progress'' if both of the following two criteria are met:

--Visibility does not decline in any Class I area, and
--Overall improvement in visibility, determined by comparing the 
average differences over all affected Class I areas

Comments Received

    Several commenters stated that the trading criteria contained in 
the proposed BART guidelines were, along with other parts of the 
guidelines, beyond EPA's authority to impose under the CAA.
    Several State commenters asked for clarification of what should be 
considered a significantly different geographic distribution of 
emission reductions, for purposes of proceeding to the two-pronged 
visibility test.
    One comment, submitted by environmental groups in response to our 
preliminary application of the two-pronged test to the CAIR in the CAIR 
rulemaking, goes to the permissibility of that test in general and is 
therefore relevant to the finalization of the test. Specifically, these 
commenters stated that because section 169A(b)(2)(A) requires BART for 
an eligible source which may reasonably be anticipated to cause or 
contribute to any impairment of visibility in any Class I area, EPA is 
without basis in law or regulation to base a better-than-BART 
determination on an analysis that uses averaging of visibility 
improvement across different Class I areas.
    Final Action. We are amending the regional haze rule to incorporate 
the two- prong visibility test as it was previously proposed in the 
BART guideline proposals. Specifically, we are adding the test to the 
rule provisions at section 51.308(e)(3).
    The EPA has the authority to prescribe this methodology under its 
general rulemaking authority provided by CAA section 301(a), and under 
CAA sections 169A(4) and 169(e). The latter provisions require EPA to 
promulgate regulations to assure reasonable progress towards the 
national visibility goal and to assure compliance with the requirements 
of section 169A, which include the requirements for BART under section 
169A(b)(2)(A), and to promulgate such measures as may be necessary to 
carry out these regulations. The EPA has determined that source-by-
source BART need not be required when it is not necessary to meet 
reasonable progress because greater progress can be achieved by an 
alternative means. The D.C. Circuit in CEED upheld this interpretation 
of the BART provisions' relationship to the broader reasonable progress 
requirements of the Act. 398 F.3d at 660. In order to assure that such 
alternative programs meet the reasonable progress goals of the CAA, EPA 
has the authority, and perhaps a duty, to promulgate regulations 
governing how that determination is made.
    Moreover, these requirements for making the ultimate comparison 
between an alternative program and BART do not affect in any way how 
states make BART determinations or how they determine which sources are 
subject to BART. It is in those areas where the Act and legislative 
history indicate that Congress evinced a special concern with insuring 
that States would be the decision makers. Nothing in American Corn 
Growers or CEED suggests that those cases rendered EPA's rulemaking 
authority under section 169A(a)(4) completely inoperable in any BART 
context.
    With respect to the use of average overall improvement, we 
explained in the CAIR NFR preamble that we disagree with comments that 
CAA section 169A(b)(2)'s requirement of BART for sources reasonably 
anticipated to contribute to impairment at any Class I area means that 
an alternative to the BART program must be shown to create improvement 
at each and every Class I Area. Even if a BART alternative is deemed to 
satisfy BART for regional haze purposes, based on average overall 
improvement as opposed to improvement at each and every Class I Area, 
CAA section 169A(b)(2)'s trigger for BART based on impairment at any 
Class I area remains in effect, because a source may become subject to 
BART based on ``reasonably attributable visibility impairment'' at any 
area. See 40 CFR 51.302. In addition, within a regional haze context, 
not every measure taken is required to achieve a visibility improvement 
at every class I area. BART is one component of long term strategies to 
make reasonable progress, but it is not the only component. The 
requirement that the alternative achieves greater progress based on the 
average improvement at all Class I areas assures that, by definition, 
the alternative will achieve greater progress overall. Though there may 
be cases where BART could produce greater improvement at one or more 
class I areas, the no-degradation prong assures that the alternative 
will not result in worsened conditions anywhere than would otherwise 
exist, and the possibility of BART for reasonably attributable 
visibility protects against any potential ``hot spots.'' Taken 
together, the EPA believes these factors make a compelling case that 
the proposed test properly defines ``greater reasonable progress.'' The 
EPA anticipates that regional haze implementation plans will also 
contain measures addressing other sources as

[[Page 39138]]

necessary to make progress at every mandatory Federal Class I area.
    We are therefore finalizing the test criteria in the same form in 
which they were proposed as part of the BART guidelines. We also 
recognize that the test criteria leave some terms and conditions 
undefined, and we believe States and Tribes should retain the 
discretion to reasonably interpret and apply these terms as appropriate 
to the context of the particular program at issue.
    First, in the proposed test we did not specify the time period 
which should serve as the starting point for comparison under the first 
prong. That is, we did not specify whether potential degradation should 
be determined in relation to visibility conditions existing at the time 
of the proposed program, or in relation to base case visibility 
projections for the time of program implementation. While either option 
is, we believe, reasonable, in this rulemaking we have used the future 
projected base case, for the following reasons.
    The underlying purpose of both prongs of the test is to assess 
whether visibility conditions at Class I areas would be better with the 
alternative program in place than they would without it. The first 
prong ensures that the program does not cause a decline in visibility 
at any particular Class I area. It addresses the possibility that the 
alternative program might allow local increases in emissions which 
could result in localized degradation. The second prong assesses 
whether the alternative program produces greater visibility improvement 
in the aggregate than would source specific BART.
    In both cases, the logical reference point is visibility conditions 
as they are expected to be at the time of program implementation but in 
the absence of the program. This insures that the visibility 
improvements or degradations determined are due to the programs being 
compared--source-specific BART and the cap-and-trade alternative--and 
not to other extrinsic factors. For example, if large increases in wild 
land fires are expected, due to accumulation of fuel from past forest 
management practices, a degradation of visibility from current 
conditions may be expected. It would be irrational to disapprove an 
alternative program because of a modeled degradation from current 
conditions, where that degradation is actually anticipated because of 
smoke from such fires--sources which are not subject to the CAA BART 
provisions. By comparing the alternative to future projected baseline 
conditions, such extrinsic variables are accounted for. We are thus 
able to ascertain (to the extent possible where future projections are 
concerned) whether visibility under the alternative would decline at 
any Class I area, all other things being equal.
    Therefore, in applying the test to the CAIR, we used the future 
(2015) projected baseline. We believe, however, that States should have 
discretion in determining the most appropriate baseline for this prong 
of the test, as long as the State's method is reasonable.
    Second, although the proposed test indicated that dispersion 
modeling should be used to determine visibility differences for the 
worst and best 20 percent of days, the guideline did not specify the 
relationship between the worst and best days and the two prongs of the 
test. We believe that each prong of the test should ideally be based on 
an examination of both the worst and best 20 percent of days. Thus, 
under the first prong, visibility must not decline at any one Class I 
area on either the best 20 percent or the worst 20 percent days \73\ as 
a result of implementing the alternative program; and, under the second 
prong both the best and worst days should be considered in determining 
whether the alternative program produces greater average improvement.
---------------------------------------------------------------------------

    \73\ The regional haze rule requires States to establish 
reasonable progress goals for each Class I area that provide for 
improvement in visibility for the most impaired days and ensure no 
degradation in visibility for the most impaired days. The reasonable 
progress test in the regional haze rule remains as a separate test 
from better than BART. The SIPs must contain measures to achieve the 
reasonable progress goal; such measures could include not only 
stationary source programs such as BART but also programs to address 
emissions from other types of sources. The no degradation (on the 20 
percent best days) component of the reasonable progress test must 
still be applied to the final future year emissions control 
strategy. This does not directly impact the conclusions of the 
better than BART test.
---------------------------------------------------------------------------

    Third, the proposed guidelines did not define ``affected'' Class I 
areas for purposes of the comparison. In applying the test to the CAIR, 
we considered all federal mandatory Class I areas in the contiguous 48 
States for which data was available. The principal Class I areas 
affected by the CAIR are those in the eastern U.S., therefore we 
calculated average improvement separately for the eastern areas, but 
also considered affects at all Class I areas nationally. We believe 
this was appropriate for a federally mandated program of the scope and 
magnitude of the CAIR. However, this may not be necessary for every 
BART-alternative program developed by States in the future, especially 
if proposed programs are limited to smaller geographic areas or are 
limited to source categories having significantly less widespread 
impacts than EGUs. In such circumstances, it may be reasonable for the 
States and Tribes involved to develop criteria for ``affected'' Class I 
areas. For example, the affected region could be considered to be the 
States and Tribes involved in the trading program as well as 
immediately adjacent States, or Class I areas within adjacent States 
that are within some defined distance of participating States.
    With respect to comments on the degree of difference in the 
geographic distribution of emissions necessary to trigger application 
of the two prong test, we believe it is not necessary for EPA to define 
that in the rule. For our CAIR analysis, we explained in the SNPR that 
the fact that CAIR would produce greater emissions reductions than BART 
in most States, but less reductions than BART in a few States, was 
sufficient reason to employ the two pronged visibility test, 69 FR 
32704. For other programs developed by States, a State would have the 
ability to make a reasonable decision as to whether there was a 
sufficient basis to make the demonstration that an alternative program 
would be better than BART based on modeling of the emissions 
distributions alone, or whether the State should proceed with the two-
pronged visibility test. The State's discretion is subject as always to 
the condition that it must be reasonably exercised, and must be 
supported by adequate documentation of the analyses.
    Finally, on a related issue, we note that in a separate rule making 
to follow soon after today's action, we will be soliciting comments on 
whether there might be other means of demonstrating that an alternative 
program makes greater reasonable progress than BART, in addition to the 
two-pronged visibility test we are finalizing in today's action. Such 
other means might take into account additional policy considerations, 
as well as the relative degree of visibility improvement of the two 
programs.

C. Final Determination That CAIR Makes Greater Reasonable Progress Than 
BART

    Proposal. As noted in the background section above, in both the 
CAIR SNPR, and NFR, we discussed the proposed approach of allowing 
States to treat CAIR as an in-lieu-of BART program for EGUs in CAIR-
affected States. In both actions, we presented analyses based on 
emission projections and air quality modeling showing that CAIR will 
achieve greater reasonable progress

[[Page 39139]]

towards the national visibility goal than would BART for affected EGUs. 
These analyses were conducted according to the criteria for making such 
``better than BART'' determinations which had been proposed in the BART 
guidelines, and which have now been finalized in the regional haze rule 
at 40 CFR 51.308(e)(3), as discussed above in section IV.B. Below, we 
briefly recap these prior analyses. See 69 FR 32684, 32702-32707 and 70 
FR 25162, 25299-25304 and associated Technical Support Documents \74\ 
for full details.
---------------------------------------------------------------------------

    \74\ Supplemental Air Quality Modeling Technical Support 
Document (TSD) for the Clean Air Interstate Rule (CAIR), May, 2004. 
http://www.epa.gov/cair/pdfs/saqmtsd.pdf; Demonstration that CAIR 
Satisfies the `Better-than-BART' Test as proposed in the Guidelines 
for Making BART Determinations, EPA Docket Number OAR-2003-0054-
YYYY, March 2005. http://www.epa.gov/cair/pdfs/finaltech04.pdf.
---------------------------------------------------------------------------

Scenarios Examined
    The CAIR is applicable to 28 States and the District of Columbia 
and requires levels of SO2 and NOX emissions 
reductions based on those achievable on a highly cost effective basis 
from EGUs. BART, on the other hand, is applicable nationwide and covers 
25 additional industrial categories, as well as EGUs, of a certain 
vintage. In our comparison, we sought to determine whether the CAIR cap 
and trade program for EGUs will achieve greater reasonable progress 
than would BART for EGUs only. Therefore, the relevant scenarios to 
examine were (1) SO2 and NOX emissions from all 
EGUs nationwide after the application of BART controls to all BART-
eligible EGUs (``nationwide BART''), and (2) SO2 and 
NOX emissions from all EGUs nationwide after the emissions 
reductions attributable to CAIR in the CAIR region and application of 
BART controls to all BART-eligible EGUS outside the CAIR region (``CAIR 
+ BART''). The latter scenario reflects the fact that source-by-source 
BART would remain a federal requirement outside the CAIR region, unless 
and until it is replaced by some other state or federally required 
program. Thus, in order to more accurately project CAIR emissions, it 
is necessary to impose BART controls outside the CAIR region, to 
account for potential load and emission shifting among EGUs.
    In addition to these two scenarios, a third was used--the future 
base case in the absence of either program. This third scenario was 
used to ensure that CAIR would not cause degradation from otherwise 
existing conditions. See section IV.B above for a discussion of why the 
future baseline is an appropriate comparison point for the first prong 
of the ``better than BART'' test.
    At the SNPR stage, a ``CAIR + BART'' scenario was not available, as 
the only projections available at that time had been developed for 
other purposes. Thus, the ``CAIR'' scenario used then, which was based 
on the Clear Skies proposal, was imperfect for purposes of this 
analysis in that it assumed SO2 reductions on a nationwide 
basis (rather than in the CAIR region only) and assumed NOX 
reductions requirements in a slightly different geographic region than 
covered by the proposed CAIR.
    For the CAIR NFR, we redid the emissions projections for both the 
Nationwide BART and CAIR + BART in the West scenarios. For the former, 
we increased the number of BART-eligible units included by lowering the 
assumed threshold for BART applicability from 250 MW capacity for both 
NOX and SO2 to 100 MW for SO2 and 25 
MW for NOX, and by reviewing the list of potentially BART-
eligible EGUs. For the latter scenario, we produced emissions 
projections based on application of CAIR-level emission reductions in 
the States proposed for inclusion in the CAIR in the SNPR.
    Emission Projections. For the analyses in both the SNPR and NFR, we 
used the Integrated Planning Model (IPM) to estimate emissions expected 
from the scenarios described above. Tables 1 and 2 present the results 
from the SNPR and NFR, respectively.

                         Table 1.--EGU SO2 and NOX Emissions--as Projected in CAIR SNPR
                                         [In thousands of tons per year]
----------------------------------------------------------------------------------------------------------------
                                                                                                   Additional
                                                                                2015 Modeled     reduction from
                                           2015 Base case     2015 ``CAIR''     nationwide e        ``CAIR''
                                            EGU emissions                           Bart        (nationwide BART
                                                                                                 minus ``CAIR'')
----------------------------------------------------------------------------------------------------------------
Nationwide SO2..........................             9,081             5,260             7,012             1,752
Nationwide NOX..........................             3,950             2,248             2,781               533
----------------------------------------------------------------------------------------------------------------


                          Table 2.--EGU SO2 and NOX Emissions--as Projected in CAIR NFR
                                         [In thousands of tons per year]
----------------------------------------------------------------------------------------------------------------
                                                                                                   Additional
                                                                                                 reduction from
                                           2015 Base case   2015 CAIR + BART   2015 Nationwide     CAIR + BART
                                            EGU emissions                           BART        (nationwide BART
                                                                                                minus CAIR+BART)
----------------------------------------------------------------------------------------------------------------
Nationwide SO2..........................             9,084             4,735             7,162             2,427
Nationwide NOX..........................             3,721             1,816             2,454               638
----------------------------------------------------------------------------------------------------------------

    As can be seen in the numbers in the right-most column, CAIR 
produced far superior emission reductions to nationwide BART, and the 
superiority of CAIR over BART increased between the SNPR and NFR 
projections, when the scenarios were corrected to more accurately 
reflect the anticipated reality in 2015.
    Air Quality Modeling Results. The proposed ``better-than-BART'' 
test provided that if the distribution of emission reductions is 
substantially the same under the alternative program as under BART, 
then the demonstration can be made simply by comparing emission 
reductions. If, however, the distribution is significantly different,

[[Page 39140]]

then visibility modeling is required in order to apply the two pronged 
test previously described. As noted above, CAIR emission reductions 
were vastly greater than those under BART. However, because there were 
some differences in the geographic distribution of reductions on a 
state-by-state basis, in order to be conservative we conducted air 
quality modeling and evaluated CAIR under the two pronged test.
    Specifically, using the above emissions projections, we completed 
numerous air quality modeling runs and postprocessing calculations to 
determine the impacts of emissions and emissions control strategies on 
visibility in Class I areas. We quantified the impacts of the CAIR and 
BART controls on visibility impairment by comparing the results of the 
future-year (2015) base case model runs with the results of the CAIR + 
BART and nationwide BART control strategy model runs. We quantified 
visibility impacts on the 20 percent best and 20 percent worst 
visibility days.
    For the SNPR modeling, we used the Regional Modeling System for 
Aerosols and Deposition (REMSAD) model to calculate these visibility 
impacts. This modeling used base year meteorology from 1996. Complete 
year ambient monitoring data, which is necessary to model future 
improvements in visibility, was available for 1996 from Inter-agency 
Monitoring of Protected Visual Environments (IMPROVE) monitors located 
at 44 Class I areas--13 within the CAIR region and 31 outside of it.
    For the NFR modeling, we used the Community Multiscale Air Quality 
(CMAQ) model. The base year meteorology used in the CMAQ modeling was 
2001. This later base year enabled us to look at more Class I areas, 
because there were more IMPROVE monitors which had complete year data 
for 2001 than there had been in 1996. Specifically, 81 of the 110 
IMPROVE sites have complete ambient air quality data for 2001. 
Moreover, because in some cases a given IMPROVE monitor is designated 
as representing more than one Class I area, these 81 sites are 
representative of 116 Class I areas. Twenty nine of the 116 are in the 
East (east of 100 degrees longitude) and 87 are in the West.
    Using the modeling results, we then applied the two prong better 
than BART test which had been defined in the proposed BART rule. As 
explained above, under the first prong, visibility must not decline at 
any Class I area, as determined by comparing the predicted visibility 
impacts at each affected Class I area under the (CAIR) trading program 
with future base case visibility conditions. Under the second prong, 
overall visibility, as measured by the average improvement at all 
affected Class I areas, must be better under the trading program than 
under source-specific BART. The future year air quality modeling 
results were used to make this demonstration.
    The visibility impacts of the CAIR + BART scenario were compared to 
base case 2015 visibility conditions (without CAIR or BART) to 
determine whether the CAIR resulted in a degradation of visibility at 
any Class I area. We also compared these visibility impacts with the 
visibility impacts of nationwide BART implementation, to assess whether 
the proposed CAIR would result in greater average visibility 
improvement than nationwide BART.
    The CAIR passed the first prong by not causing a degradation of 
visibility at any Class I area, either in the West or nationally. This 
was true in both the SNPR and NFR modeling. The visibility projections 
for each Class I area are presented in the respective TSD's.\75\
---------------------------------------------------------------------------

    \75\ See Footnote [74], Supra.
---------------------------------------------------------------------------

    The overall results are presented in tables 3 and 4 below, 
representing the SNPR and NFR modeling respectively.

 Table 3.--Average Visibility Improvement in 2015 vs. 2015 Base Case (Deciviews) as Modeled Using REMSAD in CAIR
                                                      SNPR
----------------------------------------------------------------------------------------------------------------
                                                         ``CAIR'' Scenario                Nationwide BART
                  Class I areas                  ---------------------------------------------------------------
                                                     East \76\       National          East          National
----------------------------------------------------------------------------------------------------------------
20 percent Worst Days...........................             2.0             0.7             1.0             0.4
20 percent Best Days............................             0.7             0.2             0.4             0.1
----------------------------------------------------------------------------------------------------------------


  Table 4.--Average Visibility Improvement in 2015 vs. 2015 Base Case (Deciviews) as Modeled Using CMAQ in CAIR
                                                       NFR
----------------------------------------------------------------------------------------------------------------
                                                        CAIR + BART in West               Nationwide BART
                  Class I Areas                  ---------------------------------------------------------------
                                                     East \76\       National          East          National
----------------------------------------------------------------------------------------------------------------
20 percent Worst Days...........................             1.6             0.5             0.7             0.2
20 percent Best Days............................             0.4             0.1             0.2             0.1
----------------------------------------------------------------------------------------------------------------

    As can be see from the tables, although the models produced 
different absolute values, in both cases CAIR produced significantly 
greater visibility improvement than nationwide BART. For example, 
looking at the 20 percent worst days at Eastern Class I areas (the 
areas most influenced by the CAIR, since it is an eastern program), in 
both cases the visibility improvements from CAIR were at least twice as 
great as under nationwide BART (i.e., in the SNPR, 2.0 deciviews 
compared to 1.0 deciviews improvement, and in the NFR, 1.6 deciviews 
compared to 0.7 deciviews improvement).
---------------------------------------------------------------------------

    \76\ Eastern Class I areas are those in the CAIR affected 
states, except areas in west Texas which are considered western and 
therefore included in the national average, plus those in New 
England
---------------------------------------------------------------------------

    This historical overview is given in the interest of providing a 
more complete understanding of the analyses presented at various stages 
in the CAIR rule making progress. In the end, however, it is the 
analyses presented in the CAIR NFR on which we are basing our 
determination that CAIR makes greater reasonable progress towards the 
national visibility goals than does nationwide BART. Therefore, these 
NFR results are examined more closely in the ``Final Action'' section 
below, in light of additional emissions projections we

[[Page 39141]]

have conducted to insure that changes to the CAIR and BART rules made 
subsequent to the CAIR NFR do not affect that determination.
Comments Received and EPA's Responses
    Although many comments were received regarding our proposal to 
determine that CAIR makes greater reasonable progress than BART, nearly 
all of them related either to the terms of the test itself, or to 
policy and legal implications of allowing CAIR required reductions to 
substitute for source-by-source BART. These are addressed in sections B 
(above ) and D (below) respectively. One commenter asserted, with 
respect to modeling presented in the SNPR, that the improvement of CAIR 
compared to source-specific BART is so slight it may be potentially 
within the margin of error, and therefore insufficient for the better 
than BART demonstration, or for assuring that no hot spots will occur.
    The EPA disagrees that the difference between CAIR and BART in the 
SNPR visibility projections was not significant. The visibility results 
presented in the NFR continue to show that the CAIR cap and trade 
program with BART in the non-CAIR region provides considerably more 
visibility improvement compared to nationwide BART (for EGUs only). The 
NFR modeling results show that the average visibility improvement from 
CAIR on the 20 percent worst days at 29 Eastern Class I areas is 1.6 
deciviews (dv) compared to only a 0.7 dv improvement from nationwide 
BART controls. In the ``better than BART'' TSD we have provided 
modeling results for 116 individual Class I areas. The modeling shows 
that CAIR will not create any ``hot spots.'' On the 20 percent worst 
days, all of the Eastern Class I areas show more visibility improvement 
under CAIR+BART than under BART alone. In many of the Western Class I 
areas, nationwide BART and CAIR + BART in the West provide about the 
same visibility benefits. (This is to be expected, since the CAIR is 
only applicable in the East.) While the visibility benefits are similar 
in the West (outside of the CAIR region), they are clearly not similar 
in the East, where the CAIR is predicted to achieve twice as much 
visibility improvement compared to BART.
    Final action. The CAIR vs. BART comparison presented in the CAIR 
NFR was developed while both rules were under development and therefore 
subject to change. Since the emissions projections and air quality 
modeling presented in the CAIR NFR was completed, several changes were, 
in fact, made to the CAIR region. In addition, since that time our 
assumptions regarding the likely maximum BART emission reductions from 
EGUs also changed. Therefore, we recalculated the emission projections 
to see if the rule changes could possibly affect the determination that 
CAIR will achieve greater reasonable progress than BART.
    Most significantly, the final CAIR included Arkansas, Delaware, and 
New Jersey only for purposes of significant contribution to ozone non-
attainment by summertime NOX emissions, whereas our modeling 
had been based on the assumption that these States would be included 
for contribution to PM2.5 non-attainment by SO2 
and NOX emissions. The new emission projections are based on 
the application of CAIR only for ozone in these States.
    With respect to the nationwide BART, for SO2 the NFR 
projections assumed the application of a 90 percent control or 0.10 
lbs/mmBtu at uncontrolled EGUs greater than 100 MW. In the new 
projections, the control assumptions were changed to 95 percent or 0.15 
lbs/mmbtu, to reflect the presumptive control levels in the final BART 
guidelines. For NOX, the NFR projections were based on an 
assumed emission rate of 0.2 lbs/mmBTU at all BART eligible EGUs 
nationwide. The new projections are based on the assumption of 
combustion controls on all BART eligible units except cyclones which 
have SCR, and the operation of all existing SCR and SNCRs annually, 
instead of just in the ozone season. Finally for both pollutants, the 
threshold for application of controls was increased to 200 MW, to 
better reflect the presumptions included in the final BART guidelines.
    We used IPM to project 2015 emissions given these new parameters. 
The results are presented in Table 5 below, which also includes the 
CAIR NFR projections (as reported in Table 2) for the reader's 
convenience.

       Table 5.--EGU SO2 and NOX Emissions--as Projected in CAIR NFR and as Projected in Subsequent Update
                                         (In thousands of tons per year)
----------------------------------------------------------------------------------------------------------------
                                                                                                   Additional
                                                                                                 reduction from
                                                            2015 CAIR + BART   2015 Nationwide     CAIR + BART
                                                                                    BART        (nationwide BART
                                                                                                minus CAIR+BART)
----------------------------------------------------------------------------------------------------------------
CAIR NFR:
    Nationwide SO2........................................             4,735             7,162             2,427
    Nationwide NOX........................................             1,816             2,454               638
Updated Projections:
    Nationwide SO2........................................             5,042             7,953             2,911
    Nationwide NOX........................................             2,000             2,738               738
----------------------------------------------------------------------------------------------------------------

    The updated emissions estimates for both the BART and CAIR with 
BART in the West scenarios are slightly higher than the NFR emissions 
estimates, but the difference between the CAIR + BART and nationwide 
BART scenarios are even larger compared to the NFR determination. For 
SO2, the updated CAIR + BART achieves about 2.9 million tons 
more reductions than updated nationwide BART in 2015. For 
NOX, the updated CAIR + BART policy is projected to result 
in about 738,000 tons more emissions reductions than the updated BART 
nationwide policy in 2015. The difference between the updated CAIR + 
BART and nationwide BART scenarios is now larger by 484,000 tons of 
SO2 reduction (i.e., 2,911,000 - 2,427,000) and 100,000 tons 
of NOX reduction (i.e. 738,000 - 638,000).
Implications of New Emission Projections for the Two-Pronged Test
    The first prong of the better than BART test specifies that no 
degradation of visibility can occur at any Class I area. In order to be 
sure that Class I areas do not experience a degradation in

[[Page 39142]]

visibility, we examined the updated State by State emissions estimates. 
Compared to the 2015 base case, in the updated CAIR + BART case, there 
are no individual Statewide increases in either SO2 or 
NOX (except for a very small 1,000 ton increase in 
NOX in Connecticut and 2,000 ton increase in SO2 
in New Jersey).\77\ That is consistent with the NFR CAIR + BART case in 
which no degradation was found. Consequently we have determined that no 
degradation would occur under the updated CAIR + BART emissions 
scenario.
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    \77\ The 1,000 ton per year increase in NOX in 
Connecticut represents approx. 0.003 percent of the total EGU 
NOX in the 2015 base case and the 2,000 ton per year 
increase in SO2 in New Jersey represents approx. 0.0005 
percent of the total EGU SO2 . Since the impacts on 
visibility from EGU SO2 and NOX are generally 
regional in nature, we would expect this small increase to have 
little or no impact on visibility in any Class I area.
---------------------------------------------------------------------------

    The second prong of the better than BART test specifies a greater 
average visibility improvement from the CAIR trading program (CAIR + 
BART). The average visibility improvement from the NFR CAIR + BART case 
was much greater (on the 20 percent worst visibility days) than the 
nationwide BART case. In the scenario we modeled for the NFR, the 
larger visibility improvement from CAIR + BART was achieved by reducing 
SO2 emissions by an additional 2.4 million tons per year 
compared to nationwide BART and NOX emissions by an 
additional 638,000 tons per year compared to natiowide BART.
    In the updated scenario, the emissions difference between the CAIR 
+ BART and nationwide BART cases are even larger (2.9 million tons of 
SO2 and 738,000 tons of NOX).\78\ The 
distribution of emission reductions changed somewhat in the new 
projections--that is, some States saw a larger difference between CAIR 
and BART, while in other States the difference was smaller. The largest 
change was in Kentucky, where the new projections showed that emission 
reductions from CAIR were even greater than those from BART by an 
additional 200,000 tons per year. Among States where the change between 
projections went the other direction--that is, showing that BART 
reductions were closer to CAIR reductions than previously projected--
the greatest changes were in Alabama and Pennsylvania, where the 
difference between the programs decreased by 46,000 and 45,000 tons, 
respectively.
---------------------------------------------------------------------------

    \78\ The difference between the updated CAIR + BART and 
nationwide BART scenarios is larger than the difference between the 
modeled CAIR + BART and nationwide BART scenarios. The ``difference 
of the differences'' is 485,000 tons of SO2 and 100,000 
tons of NOX.
---------------------------------------------------------------------------

    Perhaps more importantly, in the new projections, there are fewer 
States in which BART reductions are greater than CAIR reductions. In 
the NFR projections, there were 12 States \79\ where nationwide BART 
SO2 reductions were greater than CAIR + BART reductions.\80\ 
In those 12 States, BART emissions achieved approx. 686,000 more tons 
of SO2 reduction compared to CAIR + BART. In the rest of the 
States, CAIR + BART achieved an additional 3.1 million tons per year of 
SO2 reduction compared to BART. All told, the modeling 
showed that visibility improvement was greater under the CAIR than 
under BART on an overall average basis, both at eastern Class I areas 
and at all Class I areas nationally. In the new projections, CAIR + 
BART achieved an additional 3.4 million tons per year of SO2 
reduction compared to BART in 39 of the 48 States. In the remaining 9 
States \81\ BART achieved approx. 472,000 more tons of SO2 
reduction compared to CAIR + BART in the west.\82\
---------------------------------------------------------------------------

    \79\ California, Delaware, Florida, Georgia, Iowa, Louisiana, 
Michigan, Mississippi, Missouri, North Carolina, Texas, and 
Wisconsin.
    \80\ There were also four States where BART NOX 
emissions reductions were slightly higher than CAIR + BART (a total 
of 4,000 tons per year). Those States are Connecticut, Delaware, New 
Jersey, and Oklahoma.
    \81\ Alabama, Louisiana, Michigan, Mississippi, Missouri, New 
Jersey, North Carolina, Texas, Wisconsin.
    \82\ We performed a similar analysis using projections including 
the Clean Air Mercury Rule, CAMR, which was promulgated after the 
CAIR NFR. The CAMR emission projections show slight additional 
emission reductions of SO2 and NOX as compared 
to the projections CAIR + BART without CAMR, and are nearly 
identical in terms of geographic distribution. Therefore CAIR + BART 
+ CAMR, like CAIR + BART, passes the two-pronged test for 
demonstrating greater reasonable progress than BART. This is 
discussed in more detail in the TSD accompanying today's action.
---------------------------------------------------------------------------

    Due to the fact that the new projections show that the difference 
between CAIR and BART reductions is even greater than previously 
estimated, and the visibility improvements due to CAIR + BART were 
previously modeled to be much larger than BART, we can state with a 
high degree of confidence that the updated CAIR + BART scenario passes 
the second prong of the better than BART test.

D. Revision to Regional Haze Rule To Allow CAIR States To Treat CAIR as 
a BART-Substitute for EGUs

    In the SNPR, we proposed that States which adopt the CAIR cap and 
trade program for SO2 and NOX would be allowed to 
treat the participation of EGUs in this program as a substitute for the 
application of BART controls for these pollutants at affected EGUs. To 
implement this, we proposed an amendment to the Regional Haze Rule 
which would add a subpart 40 CFR 51.308(e)to read as follows:

    A State that opts to participate in the Clean Air Interstate 
Rule cap-and-trade program under part 96 AAA-EEE need not require 
affected BART-eligible EGUs to install, operate, and maintain BART. 
A State that chooses this option may also include provisions for a 
geographic enhancement to the program to address the requirement 
under Sec.  51.302(c) related to BART for reasonably attributable 
impairment from the pollutants covered by the CAIR cap and trade 
program.\83\
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    \83\ A geographic enhancement is a method, procedure, or process 
to allow a broad regional strategy, such as the CAIR cap & trade 
program, to accommodate BART for reasonably attributable impairment. 
For example, it could consist of a methodology for adjusting 
allowance allocations at a source which is required to install BART 
controls.

    We proposed that this would be codified at 40 CFR 51.308(e)(3); 
however, that section now incorporates the ``better than BART'' test as 
discussed above. In today's action, as described below we are 
finalizing this provision of the rule, where it will be codified as 
section 308(e)(4).
    The EPA's authority to treat emissions reductions required by the 
CAIR as satisfying BART was not affected by CEED. As noted, the D.C. 
Circuit in CEED upheld the proposition that EPA can approve 
implementation plans which rely on alternative strategies to BART, as 
long as greater reasonable progress is achieved. CEED, 398 F.3d at 660. 
Moreover, the CAIR program is not infected in any way with the ``group 
BART'' methodology held invalid by the court. That is because CAIR 
emission reductions levels were not based on the invalid ``group-BART'' 
approach or any other assumptions regarding BART, but were developed 
for other reasons. Specifically, the CAIR was developed to assist with 
attainment of the NAAQS for PM2.5 and ozone. Had EPA not 
performed the comparison of CAIR to BART for visibility progress 
purposes, the CAIR emission reduction requirements would remain 
unchanged. Therefore, EPA is not imposing an invalid BART requirement 
on States, but rather allowing States, at their option, to utilize the 
CAIR cap and trade program as a means to satisfy BART for affected 
EGUs.
    We received numerous comments on this proposal, which are 
summarized along with our responses in the CAIR NFR preamble at 70 FR 
25300-25302 and in the Response to Comment document. To summarize our 
responses to some of the most important comments:

[[Page 39143]]

    (1) We note that we are not constraining the discretion of States 
to determine which sources are subject to BART and to make BART 
determinations. CAIR-affected States are not required to accept our 
determination that CAIR may substitute for BART. Under the amended 
rule, States simply have the option of accepting this determination.
    (2) The EPA does not believe that anything in the CAA or relevant 
case law prohibits a State from considering emissions reductions 
required to meet other CAA requirements when determining whether source 
by source BART controls are necessary to make reasonable progress. 
Whatever the origin of the emission reduction requirement, the relevant 
question for BART purposes is whether the alternative program makes 
greater reasonable progress. As discussed above, EPA has determined 
that CAIR does so with respect to SO2 and NOX 
from EGUs in the CAIR region.
    Moreover, the fact that BART and CAIR originate from different 
provisions of the CAA does not mean that CAIR and BART emissions 
reductions would be additive if BART-eligible EGUs in the CAIR program 
were required to install and operate BART. Such source specific control 
requirements would simply result in a redistribution of emission 
reductions, as other EGUs could buy the excess allowances generated by 
the installation of controls at BART units. The net result would be the 
same level of emission reductions, but at a higher total cost, because 
the ability of the market to find the most cost effective emission 
reductions would be constrained.
    (3) Although regional haze rule section 308(e)(2) is not directly 
applicable, as the CAIR is covered by the special provision newly 
codified at section 308(e)(4), this determination is consistent with 
the policy contained in section 308(e)(2) requiring in-lieu of BART 
programs be based on emissions reductions ``surplus to reductions 
resulting from measures adopted to meet requirements as of the baseline 
date of the SIP.'' The baseline date for regional haze SIPs is 
2002;\84\ therefore CAIR reductions are surplus to requirements as of 
that year.
---------------------------------------------------------------------------

    \84\ See Memorandum from Lydia Wegman and Peter Tsirigotis, 2002 
Base Year Emission Inventory SIP Planning: 8-hr Ozone, PM2.5, and 
Regional Haze Programs, November 8, 2002. http://www.epa.gov/ttn/oarpg/t1/ memoranda/2002bye--gm.pdf.
---------------------------------------------------------------------------

    (4) We agree with commenters that it was premature to make a final 
determination whether CAIR makes greater reasonable progress than BART 
in the final CAIR because at that time the BART guidelines and the 
criteria for making such determinations had not been finalized. In 
today's action, both those rule makings are complete and therefore such 
a determination is ripe.
    (5) We disagree with commenters who thought that CAIR should be 
considered ``better than BART'' regardless of whether a State 
participates in the cap and trade program. Our demonstration that CAIR 
makes greater reasonable progress than BART is based only on an 
examination of emissions reductions from EGUs under both programs. The 
CAIR emissions projections and modeling assumes that EGU emissions will 
be capped at the levels specified in the CAIR. Therefore, States that 
choose to meet their CAIR emission reduction requirements in a manner 
other than through the participation of EGUs in the CAIR cap and trade 
program would have to develop an appropriate demonstration that the 
measures they employ make greater reasonable progress than would BART 
for any affected source categories, if the State wanted its CAIR-
required reductions to substitute for source-by-source BART.
    (6) We disagree with commenters who asserted that CAIR should 
satisfy BART for States that are subject to CAIR only for ozone season 
NOX. We explained in the final CAIR preamble that a State 
subject to CAIR for NOX purposes only would have to make a 
supplementary demonstration that BART has been satisfied for 
SO2, as well as for NOX on an annual basis. We 
wish to clarify here that a State which is only subject to CAIR for 
NOX, but which also chooses to participate in the CAIR 
trading program for both SO2 and NOX, may 
consider BART to be satisfied for both SO2 and 
NOX from EGUs. Because we modeled these States as 
controlling for both SO2 and NOX in the CAIR NFR, 
our better than BART demonstration presented in that action would be 
valid in that scenario. Conversely, if such States choose to 
participate only in the ozone season NOX trading program, 
the updated projections presented in today's action demonstrate that 
BART would be satisfied for NOX, but such states would still 
need to address BART for SO2 emissions from EGUs.
    (7) We noted in the final CAIR preamble that although we believe it 
is unlikely that a State or FLM will find it necessary to certify 
reasonably attributable visibility impairment at any Class I area, as a 
legal matter that possibility exists. That is, the determination that 
CAIR makes greater reasonable progress than BART is made in the context 
of BART for regional haze under CAA 169B, and does not preclude a 
finding of reasonably attributable impairment under CAA 169A. The CAIR 
cap and trade program does not include geographic enhancements to 
accommodate the situation where BART is required based on reasonable 
attribution at a source which participates in the trading program, but 
States retain the discretion to include such enhancements in their 
SIPs.
    (8) Our determination that CAIR makes greater reasonable progress 
than BART for EGUs is not a determination that CAIR satisfies all 
reasonable progress requirements in CAIR affected States. Each State, 
whether in the CAIR region or not, is required to set reasonable 
progress goals for each Class I area within the State as required in 
regional haze rule section 308(d)(1), and to develop long term 
strategies, considering all anthropogenic sources of visibility 
impairing pollutants, as required by section 308(d)(3).
    In setting the reasonable progress goals, the State is to consider 
the amount of visibility improvement needed to achieve a uniform rate 
of progress towards natural background conditions in the year 2064. 
(This uniform rate of progress is sometimes referred to as the default 
glide-path). The State is also to consider the statutory reasonable 
progress factors contained in CAA section 169A(g)(1).\85\
---------------------------------------------------------------------------

    \85\ Similar to the BART factors, the reasonable progress 
factors are: the cost of compliance, the time necessary for 
compliance, the energy and nonair quality environmental impacts of 
compliance, and the remaining useful life of any existing sources 
subject to such requirements.
---------------------------------------------------------------------------

    In doing so, we anticipate that States will take into account the 
degree to which CAIR emissions reductions are projected to bring 
visibility conditions at its Class I areas in line with the default 
glide path. In some States, the improvements expected from CAIR, 
combined with the application of the reasonable progress factors to 
other source sectors, may result in a determination that few additional 
emissions reductions are reasonable for the first long term strategy 
period. Nonetheless, each State is required to set its reasonable 
progress goals as provided by the regional haze rule and cannot assume 
that CAIR will satisfy all of its visibility-related obligations.

V. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

    Under Executive Order 12866 (58 FR 51735, October 4, 1993), EPA 
must determine whether the regulatory action is ``significant'' and, 
therefore, subject to Office of Management and Budget

[[Page 39144]]

(OMB) review and the requirements of the Executive Order. The Order 
defines ``significant regulatory action'' as one that is likely to 
result in a rule that may:
    (1) Have an annual effect on the economy of $100 million or more or 
adversely affect in a material way the economy, a sector of the 
economy, productivity, competition, jobs, the environment, public 
health or safety, or State, local, or Tribal governments or 
communities;
    (2) Create a serious inconsistency or otherwise interfere with an 
action taken or planned by another agency;
    (3) Materially alter the budgetary impacts of entitlements, grants, 
user fees, or loan programs or the rights and obligations of recipients 
thereof; or
    (4) Raise novel legal or policy issues arising out of legal 
mandates, the President's priorities, or the principles set forth in 
the Executive Order.
    Pursuant to the terms of Executive Order 12866, it has been 
determined that this rule is a ``significant regulatory action,'' thus 
EPA has submitted this rule to OMB for review. The drafts of the rules 
submitted to OMB, the documents accompanying such drafts, written 
comments thereon, written responses by EPA, and identification of the 
changes made in response to OMB suggestions or recommendations are 
available for public inspection at EPA's Air and Radiation Docket and 
Information Center (Docket Number OAR-2002-0076). The EPA has prepared 
the document entitled ``Regulatory Impact Analysis of the Final Clean 
Visibility Interstate Rule or Guidelines for Best Available Retrofit 
Technology Determinations Under the Regional Haze Regulations'' (RIA) 
to address the requirements of this executive order.
1. What Economic Analyses Were Conducted for the Rulemaking?
    The analyses conducted for this final rule provide several 
important analyses of impacts on public welfare. These include an 
analysis of the social benefits, social costs, and net benefits of 
three possible regulatory scenarios that States may follow to implement 
the BART rule and guidelines. The economic analyses also address issues 
involving requirements of the Paperwork Reduction Act (PRA), potential 
small business impacts, unfunded mandates (including impacts for Tribal 
governments), environmental justice, children's health, energy impacts, 
and other statutory and executive order requirements.
2. What Are the Benefits and Costs of This Rule?
    The benefit-cost analysis shows that substantial net economic 
benefits to society are likely to be achieved due to reductions in 
emissions resulting from this rule. The results detailed below show 
that this rule would be beneficial to society, with annual net benefits 
(benefits less costs) ranging from approximately $1.9 to $12.0 billion 
in 2015. These alternative net benefits estimates reflect differing 
assumptions about State actions taken to implement BART and about the 
social discount rate used to estimate the annual value of the benefits 
and costs of the rule. All amounts are reflected in 1999 dollars. The 
range of benefits and costs reported for the BART represent estimates 
of EPA's assessment of State actions that will likely be taken to 
comply with the BART rule and guidelines.
a. Control Scenarios
    Today's rule sets forth presumptive requirements for States to 
require EGUs to reduce SO2 and NOX emissions for 
units greater than 200 megawatts (MW) in capacity at plants greater 
than 750 MW in capacity that significantly contribute to visibility 
impairment in Federal Class I areas (national parks). The analysis 
conducted in the RIA presents alternative control scenarios of possible 
additional controls for EGUs located at plants less than 750 MW in 
capacity. The EPA also calculated the amount of SO2 and 
NOX emissions reductions for several illustrative scenarios 
that reflect alternative State actions regulating industries with non-
EGU sources. The analyses conducted include three regulatory 
alternative scenarios that States may choose to follow to comply with 
BART. The alternatives include three scenarios of increasing 
stringency--Scenario 1, Scenario 2, and Scenario 3. A brief discussion 
of the these alternatives for the EGUs and all other sources follows. 
More details of the alternative control scenarios and associated 
control costs are discussed in the RIA.
i. Electric Generating Units
    In the revised BART guidelines, we have included presumptive 
control levels for SO2 and NOX emissions from 
coal-fired electric generating units greater than 200 megawatts (MW) in 
capacity at plants greater than 750 MW in capacity. Given the 
similarities of these units to other BART-eligible coal-fired units 
greater than 200 MW at plants 750 MW or less, EPA's guidance suggests 
that States control such units at similar levels for BART. The 
guidelines would require 750 MW power plants to meet specific control 
levels of either 95 percent control or controls of 0.15 lbs/MMBtu, for 
each EGU greater than 200 MW, unless the State determines that an 
alternative control level is justified based on a careful consideration 
of the statutory factors.\86\ Thus, for example, if the source 
convincingly demonstrates unique circumstances affecting its ability to 
cost-effectively reduce its emissions, the State may take that into 
account in determining whether the presumptive levels of control are 
appropriate for the facility. For an EGU greater than 200 MW in size, 
but located at a power plant smaller than 750 MW in size, States may 
also find that such controls are cost-effective when taking into 
consideration the costs of compliance in the BART analysis in applying 
the five factor test for the BART determination. In our analysis we 
have assumed that no additional controls will occur where units have 
existing scrubbers and that no controls will occur for oil-fired units. 
While these levels may represent current control capabilities, we 
expect that scrubber technology will continue to improve and control 
costs will continue to decline.
---------------------------------------------------------------------------

    \86\ These levels are commonly achievable by flue gas 
desulfurization controls (``scrubbers'').
---------------------------------------------------------------------------

    For NOX, for those large EGUs that have already 
installed selective catalytic reduction (SCR) or selective non-
catalytic reduction (SNCR) during the ozone season, States should 
require the same controls for BART. However, those controls should be 
required to operate year-round for BART. For sources currently using 
SCR or SNCR for part of the year, states should presume that the use of 
those same controls year-round is highly cost-effective. For other 
sources, the guidelines establish presumptive emission levels that vary 
depending largely upon boiler type and fuel burned. For coal-fired 
cyclone units with a size greater than 200 MW, our analysis assumes 
these units will install SCR. For all other coal-fired units, our 
analysis assumed these units will install current combustion control 
technology. In addition, we assume no additional controls for oil and/
or gas-fired steam units.
    We present alternative regulatory scenarios. Scenario 2 represents 
our application of the presumptive limits described above to all BART 
eligibility EGUs greater than 200 MW. For Scenario 1, we assume that 
only 200 MW BART-eligible EGUs located at facilities above 750 MW 
capacity will comply with the SO2 requirements and 
NOX controls. In this scenario, no

[[Page 39145]]

facilities less than 750 MW capacity are assumed to install BART 
controls. For Scenario 1, we assume that units with existing SCRs will 
operate those SCR units year round annually. In contrast in Scenario 3, 
we analyzed SO2 controls equivalent to 95 percent reductions 
or 0.1 lbs per MMBtu on all previously uncontrolled units. 
NOX controls for this most stringent scenario presume SCRs 
will be installed on all units greater than 100 MW capacity and 
combustion controls will be installed on units greater than 25 MW but 
less than 100 MW capacity. The EPA analyzed the costs of each BART 
scenario using the Integrated Planning Model (IPM). The EPA has used 
this model extensively in past rulemakings to analyze the impacts of 
regulations on the power sector.
    The analysis presented assumes that BART-eligible EGUs affected by 
the Clean Air Interstate Rule (70 FR 25162) have met the requirements 
of this rule. Thus, no additional controls for EGUs beyond CAIR are 
anticipated or modeled for the 28 State plus District of Columbia CAIR 
region. In addition, we are assuming no additional SO2 
controls for sources located in States of Arizona, Utah, Oregon, 
Wyoming, and New Mexico or Tribal lands located in these States due to 
agreements made with the Western Regional Air Partnership (WRAP).
ii. Sources Other Than Electric Generating Units
    As previously discussed there are 25 source categories potentially 
subject to BART in addition to EGUs (referred to as non-EGU source 
categories) as defined by the CAA. The EPA evaluated a set of 
SO2 and NOX emission control technologies 
available for these source categories and estimated the associated 
costs of control using AirControlNET. The control scenarios evaluated 
reflect control measure cost caps of up to $1,000 per ton (Scenario 1), 
$4,000 per ton (Scenario 2), and $10,000 per ton (Scenario 3). The EPA 
also conducted a cost analysis for control costs of up to $2,000 per 
ton and $3,000 per ton, and the results of this analysis are presented 
in the RIA. The analysis consists of applying SO2 and 
NOX controls to each non-EGU source category up to the 
specified cost per ton ``cap'' in each scenario. These cost per ton 
caps are specified in average cost terms. As control stringency is 
increased, the marginal costs are also estimated for each non-EGU 
source category. The scenarios examined are based on the costs of 
technologies such as scrubbers for SO2 control, and varying 
types of technologies for NOX control. Scrubbers are the 
most common type of SO2 control for most non-EGU sources for 
each scenario, while combustion controls such as low NOX 
burners (LNB) and post-combustion controls such as selective 
noncatalytic reduction (SNCR) and selective catalytic reduction (SCR) 
are commonly applicable to most of the non-EGU source categories. 
Combustion controls are commonly applied as part of Scenario 1, while 
SNCR and SCR are more commonly applied either by themselves or in 
combination with combustion controls as part of Scenarios 2 and 3. 
Analyses are not available for 8 of the 25 non-EGU source categories, 
because there are no available control measures for these sources or 
there are no sources in these categories included in the non-EGU 
emissions data utilized in these analyses. All of these results are 
estimated using a nationwide database of BART-eligible non-EGU sources 
that is based on information collected from Regional Planning 
Organizations (RPOs) in the fall of 2004.
b. Baseline and Year of Analysis
    The final rule sets forth the guidelines for States and Tribes for 
meeting the BART requirements under the CAA and the Regional Haze Rule. 
The Agency considered all promulgated CAA requirements and known State 
actions in the baseline used to develop the estimates of benefits and 
costs for this rule including the recently promulgated Clean Air 
Interstate Rule (70 FR 25162) and the proposal to include New Jersey 
and Delaware in the final CAIR region for fine particulate matter (70 
FR 25408). However, EPA did not include within the baseline the actions 
States may take to implement the ozone and PM2.5 NAAQS 
standards nor the recently promulgated Clean Air Mercury Rule. No 
additional SO2 controls were assumed for any EGUs within the 
five WRAP States of Utah, Arizona, Wyoming, Oregon or New Mexico that 
have existing agreements to achieve reduction goals.
    In the analysis, the controls and reductions are assumed to be 
required in 2015, a date that is generally consistent with the expected 
timing of the rule. States must submit SIPs relevant to the BART 
requirements in January 2008. After approval of the SIP, there is a 5 
year compliance date. Thus, controls are likely to be installed and in 
operation by the end of 2013 or the beginning of 2014 to comply with 
the rule. In addition, EPA had existing inventories, modeling, and base 
case runs for 2015 to use for the analysis. The year 2015 is used in 
this analysis. All estimates presented in this report represent 
annualized estimates of the benefits and costs of BART in 2015 rather 
than the net present value of a stream of benefits and costs in these 
particular years of analysis.
c. Cost Analysis and Economic Impacts
    For the affected region, the projected annual private incremental 
costs of BART to the power industry (EGU source category) range from 
$253 to $896 million in 2015 depending upon the scenario evaluated. 
These costs represent the private compliance cost to the electric 
generating industry of reducing NOX and SO2 
emissions that EPA believes States may require to comply with BART.
    In estimating the net benefits of regulation, the appropriate cost 
measure is ``social costs.'' Social costs represent the welfare costs 
of the rule to society. These costs do not consider transfer payments 
(such as taxes) that are simply redistributions of wealth. The social 
costs of this rule for the EGU sector only are estimated to range from 
approximately $119 to $567 million in 2015 assuming a 3 percent 
discount rate. These EGU sector costs become $141 to $688 million in 
2015 assuming a 7 percent discount rate.
    Overall, the impacts of the BART are modest, particularly in light 
of the large benefits we expect. Retail electricity prices are 
projected to increase roughly 0.1 percent with BART in the 2015 
timeframe under Scenario 2. Coal-fired generation, as well as coal 
production and natural gas-fired generation are projected to remain 
essentially unchanged as a result of this rule. It is also not expected 
that BART will change the composition of new generation built to meet 
growth in electricity demand. BART is also not expected to impact coal 
or natural gas prices.
    For today's rule, EPA analyzed the costs for the EGU source 
category using the Integrated Planning Model (IPM). The IPM is a 
dynamic linear programming model that can be used to examine the 
economic impacts of air pollution control policies for SO2 
and NOX throughout the contiguous U.S. for the entire power 
system. Documentation for IPM can be found in the docket for this 
rulemaking or at http://www.epa.gov/airmarkets/epa-ipm.
    The EPA also conducted an analysis of State actions in requiring 
emission controls for BART eligible sources in the non-EGU source 
categories. For the nation, the projected annual private incremental 
costs range from $150 million to $2.24 billion for industries with 
affected non-EGU sources. This cost range results from different 
assumptions about possible actions

[[Page 39146]]

States may take to comply with BART and alternative discount rates of 3 
and 7 percent. The non-EGU private incremental control cost estimates 
are assumed to approximate the social costs of the rule for the non-EGU 
sector. The EPA analyzed the costs to non-EGUs sources using 
AirControlNET. The AirControlNET is a software tool that can be used to 
estimate the private costs and emission reductions of air pollution 
control policies for SO2, NOX, and other criteria 
pollutants throughout the contiguous U.S. for all manufacturing 
industries and many other industries. Documentation for AirControlNET 
can be found in the docket for this rulemaking or at http://www.epa.gov/ttn/ecas/AirControlNET.htm.
    In summary, the EPA estimates that the annual social costs of this 
rule for the EGU and non-EGU source categories range from approximately 
$0.3 to $2.9 billion annually, based on alternative scenarios of State 
actions in response to the BART rule and guidelines assuming 3 or 7 
percent discount rates. Estimates are reflected in 1999 dollars.
d. Human Health Benefit Analysis
    Our analysis of the health and welfare benefits associated with 
this rule are presented in this section. Briefly, the analysis projects 
major benefits from implementation of the rule in 2015. As described 
below, thousands of deaths and other serious health effects would be 
prevented. We are able to monetize annual benefits ranging from 
approximately $2.2 to $14.3 billion in 2015. This range reflects 
different assumptions about States actions in response to the BART rule 
and the applicable discount rate (3 percent or 7 percent).
    Table IV-1 presents the primary estimates of reduced incidence of 
PM- and visibility-related health effects for 2015 for the regulatory 
control strategy the EPA expects States may follow to comply with BART. 
In 2015 for Scenario 2, we estimate that PM-related annual benefits 
include approximately 1,600 fewer premature fatalities, 890 fewer cases 
of chronic bronchitis, 2,200 fewer non-fatal heart attacks, 2300 fewer 
hospitalizations (for respiratory and cardiovascular disease combined--
admissions and emergency room visits) and result in significant 
reductions in days of restricted activity due to respiratory illness 
(with an estimate of one million fewer cases) and approximately 170,000 
fewer work-loss days. We also estimate substantial health improvements 
for children from reduced upper and lower respiratory illness, acute 
bronchitis, and asthma attacks.
    Ozone health-related benefits are expected to occur during the 
summer ozone season (usually ranging from May to September in the 
Eastern U.S.). Since we did not conduct ozone modeling for this 
rulemaking, we are unable to quantify or monetize the ozone related 
benefits that will likely result from BART.
    Table IV-2 presents the estimated monetary value of reductions in 
the incidence of health and welfare effects. Annual PM-related health 
benefits and visibility benefits are estimated to range from 
approximately $2.2 to $14.3 billion annually. This range of estimates 
reflects different scenarios about States actions in response to the 
BART rule and the applicable discount rate (3 percent or 7 percent). 
Estimated annual visibility benefits in southeastern and southwestern 
Class I areas range from approximately $80 million to $420 million 
annually in 2015. All monetized estimates are stated in 1999$. These 
estimates account for growth in real gross domestic product (GDP) per 
capita between the present and 2015. As the table indicates, total 
benefits are driven primarily by the reduction in premature fatalities 
each year. Reductions in premature mortality account for over 90 
percent of total benefits.
    Table IV-3 presents the total monetized net benefits for 2015. This 
table also indicates with a ``B'' those additional health and 
environmental benefits of the rule that we were unable to quantify or 
monetize. These effects are additive to the estimate of total benefits. 
A listing of the benefit categories that could not be quantified or 
monetized in our benefit estimates are provided in Table IV-4. We are 
not able to estimate the magnitude of these unquantified and 
unmonetized benefits. While EPA believes there is considerable value to 
the public for the PM-related benefit categories that could not be 
monetized, we believe these benefits may be small relative to those 
categories we were able to quantify and monetize. In contrast, EPA 
believes the monetary value of the ozone-related premature mortality 
benefits could be substantial, but we were unable to estimate the 
benefits for this rulemaking.
e. Quantified and Monetized Welfare Benefits
    Only a subset of the expected visibility benefits--those for Class 
I areas in the southeastern and southwestern U.S. are included in the 
monetary benefits estimates we project for this rule. We believe the 
benefits associated with these non-health benefit categories are likely 
significant. For example, we are able to quantify significant 
visibility improvements in Class I areas in the Northeast and Midwest, 
but are unable at present to place a monetary value on these 
improvements. Similarly, we anticipate improvement in visibility in 
residential areas where people live, work and recreate in the nation 
for which we are currently unable to monetize benefits. For the Class I 
areas in the southeastern and southwestern U.S., we estimate annual 
benefits ranging from $80 to $420 million beginning in 2015 for 
visibility improvements. The value of visibility benefits in areas 
where we were unable to monetize benefits could also be substantial.

Table IV-1.--Clean Air Visibility Rule: Estimated Reduction in Incidence of Adverse Health Effects in 2015 \a,b\
----------------------------------------------------------------------------------------------------------------
                                                                             Incidence reduction
                       Health Effect                       -----------------------------------------------------
                                                               Scenario 1        Scenario 2        Scenario 3
----------------------------------------------------------------------------------------------------------------
PM-Related Endpoints:
    Premature mortality \c\
        Adult, age 30 and over............................               400             1,600             2,300
        Infant, age <1 year...............................                 1                 4                 5
    Chronic bronchitis (adult, age 26 and over)...........               230               890             1,300
    Non-fatal myocardial infarction (adults, age 18 and                  570             2,200             3,000
     older)...............................................
    Hospital admissions--respiratory (all ages) \d\.......               140               510               720
    Hospital admissions--cardiovascular (adults, age >18)                120               450               640
     \e\..................................................
    Emergency room visits for asthma (age 18 years and                   370             1,300             1,800
     younger).............................................
    Acute bronchitis (children, age 8-12).................               550             2,100             3,000

[[Page 39147]]

 
    Lower respiratory symptoms (children, age 7-14).......             6,600            25,000            36,000
    Upper respiratory symptoms (asthmatic children, age 9-             5,000            19,000            27,000
     18)..................................................
    Asthma exacerbation (asthmatic children, age 6-18)....             8,100            31,000            44,000
    Work loss days (adults, age 18-65)....................            44,000           170,000           240,000
    Minor restricted-activity days (MRADs) (adult age, 18-           260,000         1,000,000        1,400,000
     65)..................................................
----------------------------------------------------------------------------------------------------------------
\a\ Incidences are rounded to two significant digits. These estimates represent benefits from BART nationwide.
  The modeling used to derive these incidence estimates assumes the final CAIR program in the baseline including
  the CAIR promulgated rule and the proposal to include SO2 and annual NOX controls for New Jersey and Delaware.
  Modeling used to develop these estimates assumes annual SO2 and NOX controls for Arkansas for CAIR resulting
  in a slight understatement of the reported benefits and costs for BART. The recently promulgated CAMR has not
  been considered in the baseline for BART.
\b\ Ozone benefits are expected for BART, but are not estimated for this analysis.
\c\ Adult premature mortality based upon studies by Pope et al., 2002. Infant premature mortality is based upon
  studies by Woodruff, Grillo, and Schoendorf, 1997.
\d\ Respiratory hospital admissions for PM include admissions for chronic obstructive pulmonary disease (COPD),
  pneumonia, and asthma.
\e\ Cardiovascular hospital admissions for PM include total cardiovascular and subcategories for ischemic heart
  disease, dysrhythmias, and heart failure.


 Table IV-2. Estimated Monetary Value of Reductions in Incidence of Health and Welfare Effects for the Clean Air
                                             Visibility Rule in 2015
                                           [In millions of 1999$] a,b
----------------------------------------------------------------------------------------------------------------
                                                             Scenario 1         Scenario 2         Scenario 3
----------------------------------------------------------------------------------------------------------------
Health Effects:
    Premature mortality c,d
        Adult >30 years
            3 percent discount rate....................         $2,330             $9,180            $13,000
            7 percent discount rate....................          1,960              7,730             10,900
        Infant <1 year.................................              6.12              23.8               34.2
    Chronic bronchitis (adults, 26 and over)...........             90.5              353                498
    Nonfatal acute myocardial infarctions
        3 percent discount rate........................             49.3              189                264
        7 percent discount rate........................             45.8              175                245
    Hospital admissions for respiratory causes.........              1.07               4.03               5.65
    Hospital admissions for cardiovascular causes......              2.6               10.0               14.1
    Acute bronchitis (children, age 8-12)..............              0.207              0.79               1.12
    Lower respiratory symptoms (children, 7-14)........              0.109              0.415              0.587
    Upper respiratory symptoms (asthma, 9-11)..........              0.137              0.523              0.74
    Emergency Room Visits for Asthma (age 18 years and               0.106              0.362              0.51
     younger)..........................................
    Asthma exacerbations...............................              0.367              1.4                1.98
    Work loss days.....................................              5.56              22.4               31.5
    Minor restricted-activity days (MRADs).............             13.8               54.1               76.3
Welfare Effects:
    Recreational visibility, 81 Class I areas..........             84                239                416
                                                        --------------------
    Monetized Total \e\
        Base Estimate:
            3 percent discount rate....................        2,600+B           10,100+B           14,300+B
            7 percent discount rate....................        2,200+B            8,600+B          12,200+B
----------------------------------------------------------------------------------------------------------------
\a\ Monetary benefits are rounded to three significant digits. These estimates are nationwide with the exception
  of visibility benefits. Visibility benefits relate to Class I areas in the southeastern and southwestern
  United States. Ozone benefits are expected for BART, but have not been estimated for this analysis. The
  benefit estimates assume the final CAIR program in the baseline that includes the CAIR promulgated rule and
  the proposal to include SO2 and annual NOX controls for New Jersey and Delaware. Modeling used to develop the
  CAIR baseline estimates assumes annual SO2 and NOX controls for Arkansas resulting in a slight understatement
  of the reported benefits and costs for BART. The recently promulgated CAMR is not considered in the baseline
  for BART.
\b\ Monetary benefits adjusted to account for growth in real GDP per capita between 1990 and the analysis year
  of 2015.
\c\ Valuation assumes discounting over the SAB-recommended 20-year segmented lag structure described in Chapter
  4. Results show 3 percent and 7 percent discount rates consistent with EPA and OMB guidelines for preparing
  economic analyses (U.S. EPA, 2000; OMB, 2003).
\d\ Adult premature mortality based upon studies by Pope et al., 2002. Infant premature mortality based upon
  studies by Woodruff, Grillo, and Schoendorf, 1997.
\e\ B represents the monetary value of health and welfare benefits not monetized. A detailed listing is provided
  in Table IV-4. Totals rounded to nearest $100 million, and totals may not sum due to rounding.


   Table IV-3.--Summary of Annual Benefits, Costs, and Net Benefits of the Clean Air Visibility Rule in 2015 a
                                               [Billions of 1999$]
----------------------------------------------------------------------------------------------------------------
                           Description                              Scenario 1      Scenario 2      Scenario 3
----------------------------------------------------------------------------------------------------------------
Social costs b

[[Page 39148]]

 
    3 percent discount rate.....................................            $0.4            $1.4            $2.3
    7 percent discount rate.....................................             0.3             1.5             2.9
Social benefits c, d, e
    3 percent discount rate.....................................         2.6 + B        10.1 + B        14.3 + B
    7 percent discount rate.....................................         2.2 + B         8.6 + B        12.2 + B
Health-related benefits:
    3 percent discount rate.....................................             2.5             9.8            13.9
    7 percent discount rate.....................................             2.1             8.4            11.8
Visibility benefits.............................................            0.08            0.24            0.42
Net benefits (benefits-costs) e, f
    3 percent discount rate.....................................         2.2 + B         8.7 + B        12.0 + B
    7 percent discount rate.....................................         1.9 + B         7.1 + B        9.3 + B
----------------------------------------------------------------------------------------------------------------
a All estimates are rounded to three significant digits and represent annualized benefits and costs anticipated
  for the year 2015. Estimates assume a complete CAIR program in the baseline including the CAIR promulgated
  rule and the proposal to include SO2 and annual NOX controls for New Jersey and Delaware. Modeling used to
  develop the CAIR baseline estimates assumes annual SO2 and NOX controls for Arkansas resulting in a slight
  understatement of the reported benefits and costs for BART. The recently promulgated CAMR is not considered in
  the baseline for BART.
b Note that costs are the annualized total costs of reducing pollutants including NOX and SO2 for the EGU source
  category in areas outside the CAIR region and excluding additional SO2 controls for the WRAP 309 States of UT,
  AZ, WY, OR or NM and include costs for non-EGU sources nationwide. The discount rate used to conduct the
  analysis impacts the control strategies chosen for the non-EGU source category resulting in greater level of
  controls under the 3 percent discount rate for Scenario 1.
c As this table indicates, total benefits are driven primarily by PM-related health benefits. The reduction in
  premature fatalities each year accounts for over 90 percent of total monetized benefits in 2015. Benefit
  estimates in this table are nationwide (with the exception of visibility) and reflect NOX and SO2 reductions.
  Ozone benefits are expected to occur for this rule, but are not estimated in this analysis. Visibility
  benefits represent benefits in Class I areas in the southeastern and southwestern United States.
d Not all possible benefits or disbenefits are quantified and monetized in this analysis. B is the sum of all
  unquantified benefits and disbenefits. Potential benefit categories that have not been quantified and
  monetized are listed in Table IV-4.
e Valuation assumes discounting over the SAB-recommended 20-year segmented lag structure described in Chapter 4.
  Results reflect 3 percent and 7 percent discount rates consistent with EPA and OMB guidelines for preparing
  economic analyses (U.S. EPA, 2000; OMB, 2003).
f Net benefits are rounded to the nearest $100 million. Columnar totals may not sum due to rounding.


   Table IV-4.--Unquantified and Nonmonetized Effects of the Clean Air
                             Visibility Rule
------------------------------------------------------------------------
                                       Effects not included in primary
         Pollutant/effect                  estimates--changes in:
------------------------------------------------------------------------
Ozone--Health a...................   Premature mortality b.
                                     Chronic respiratory damage.
                                     Premature aging of the
                                     lungs.
                                     Nonasthma respiratory
                                     emergency room visits.
                                     Increased exposure to Uvb.
                                     Hospital Admissions :
                                     respiratory.
                                     Emergency room visits for
                                     asthma.
                                     Minor restricted activity
                                     days.
                                     School loss days.
                                     Asthma attacks.
                                     Cardiovascular emergency
                                     room visits.
                                     Acute respiratory symptoms.
Ozone--Welfare....................   Yields for:
                                     --Commercial forests,
                                     --Fruits and vegetables, and
                                     --Commercial and noncommercial
                                     crops.
                                     Damage to urban ornamental
                                     plants.
                                     Recreational demand from
                                     damaged forest aesthetics.
                                     Ecosystem functions.
                                     Increased exposure to UVb.
PM--Health c......................   Premature mortality: short-
                                     term exposuresd.
                                     Low birth weight.
                                     Pulmonary function.
                                     Chronic respiratory
                                     diseases other than chronic
                                     bronchitis.
                                     Nonasthma respiratory
                                     emergency room visits.
                                     Exposure to UVb (+/-) e.
PM--Welfare.......................   Visibility in many Class I
                                     areas.
                                     Residential and
                                     recreational visibility in non-
                                     Class I areas.
                                     Soiling and materials
                                     damage.
                                     Ecosystem functions.
                                     Exposure to UVb (+/-)e.
Nitrogen and Sulfate Deposition--    Commercial forests due to
 Welfare.                            acidic sulfate and nitrate
                                     deposition.
                                     Commercial freshwater
                                     fishing due to acidic deposition.
                                     Recreation in terrestrial
                                     ecosystems due to acidic
                                     deposition.
                                     Existence values for
                                     currently healthy ecosystems.

[[Page 39149]]

 
                                     Commercial fishing,
                                     agriculture, and forests due to
                                     nitrogen deposition.
                                     Recreation in estuarine
                                     ecosystems due to nitrogen
                                     deposition.
                                     Ecosystem functions.
                                     Passive fertilization due
                                     to nitrogen deposition.
Mercury Health g..................   Incidence of neurological
                                     disorders.
                                     Incidence of learning
                                     disabilities.
                                     Incidence of developmental
                                     delays.
                                     Potential reproductive
                                     effectsf.
                                     Potential cardiovascular
                                     effectsf, including:
                                     --Altered blood pressure regulation
                                     f
                                     --Increased heart rate variability
                                     f
                                     --Incidence of myocardial
                                     infarction f
Mercury Deposition Welfare g......   Impacts on birds and
                                     mammals (e.g., reproductive
                                     effects).
                                     Impacts to commercial,
                                     subsistence, and recreational
                                     fishing.
------------------------------------------------------------------------
a In addition to primary economic endpoints, there are a number of
  biological responses that have been associated with ozone health
  effects including increased airway responsiveness to stimuli,
  inflammation in the lung, acute inflammation and respiratory cell
  damage, and increased susceptibility to respiratory infection. The
  public health impact of these biological responses may be partly
  represented by our quantified endpoints.
b Premature mortality associated with ozone is not currently included in
  the primary analysis. Recent evidence suggests that short-term
  exposures to ozone may have a significant effect on daily mortality
  rates, independent of exposure to PM. EPA is currently conducting a
  series of meta-analyses of the ozone mortality epidemiology
  literature. EPA will consider including ozone mortality in primary
  benefits analyses once a peer-reviewed methodology is available.
c In addition to primary economic endpoints, there are a number of
  biological responses that have been associated with PM health effects
  including morphological changes and altered host defense mechanisms.
  The public health impact of these biological responses may be partly
  represented by our quantified endpoints.
d While some of the effects of short term exposures are likely to be
  captured in the estimates, there may be premature mortality due to
  short term exposure to PM not captured in the cohort study upon which
  the primary analysis is based.
e May result in benefits or disbenefits. See discussion in Section 5.3.4
  for more details.
f These are potential effects as the literature is insufficient.
g Mercury emission reductions are not anticipated for BART for the EGU
  source category due to the cap-and-trade program promulgated for the
  Clean Air Mercury Rule (March 2005); however, the geographic location
  of mercury reductions may change as a result of this rule. EPA
  believes any such effects for these sources would be minimal. Mercury
  reductions are expected for the non-EGU source categories. The mercury
  reduction for BART from the non-EGU source categories is expected to
  be small in comparison to reductions resulting from the recently
  promulgated Clean Air Interstate Rule and the Clean Air Mercury Rule
  (March 2005).

3. How Do the Benefits Compare to the Costs of This Final Rule?
    In estimating the net benefits of regulation, the appropriate cost 
measure is ``social costs.'' Social costs represent the welfare costs 
of the rule to society. The social costs of this rule for the EGU and 
non-EGU sector sources are estimated to range from approximately $0.3 
to $2.9 billion in 2015. This range depends upon the control scenario 
assumed and applicable discount rates of 3 percent and 7 percent. The 
net benefits (social benefits minus social costs) of the rule range 
from approximately $1.9 + B billion or $12.0 + B billion depending upon 
the scenario evaluated and the applicable discount rate (3 and 7 
percent) annually in 2015. Implementation of the rule is expected to 
provide society with a substantial net gain in social welfare based on 
economic efficiency criteria.
    There is uncertainty surrounding the actions States are likely to 
take to comply with the BART guidelines. States will determine BART-
eligible sources based upon CAA criteria, determine those BART-eligible 
sources reasonably anticipated to cause or contribute to visibility 
impairment in Class I areas and then apply a 5 factor test for BART 
determinations. The range of estimated benefits, costs, and resulting 
net benefits for BART reflects the uncertainty concerning States 
responses to BART and represents EPA's best estimates of the benefit-
cost outcomes of alternative compliance scenarios.
    The annualized cost of BART, as quantified here, is EPA's best 
assessment of the cost of actions States are likely to take to comply 
with the rule. The EGU portion of these costs are generated from 
rigorous economic modeling of changes in the power sector due to the 
BART rule and guidelines. This type of analysis using IPM has undergone 
peer review and been upheld in Federal courts. The direct cost 
includes, but is not limited to, capital investments in pollution 
controls, operating expenses of the pollution controls, investments in 
new generating sources, and additional fuel expenditures. The EPA 
believes that these costs reflect, as closely as possible, the 
additional costs of the BART rule and guidelines to industry. However, 
there may exist certain costs that EPA has not quantified in these 
estimates. These costs may include costs of transitioning to the BART, 
such as the costs associated with the retirement of smaller or less 
efficient EGUs, employment shifts as workers are retrained at the same 
company or re-employed elsewhere in the economy. Costs may be 
understated since an optimization model was employed that assumes cost 
minimization, and the regulated community may not react in the same 
manner to comply with the rule. Although EPA has not quantified these 
potential additional costs, the Agency believes that they are small 
compared to the quantified costs of the program on the power sector. 
The annualized cost estimates presented are the best and most accurate 
based upon available information.
    The non-EGU portion of these costs are generated from extensive 
cost modeling based on applying illustrative regulatory scenarios to 
the non-EGU source categories. These costs represent potential impacts 
to non-EGU sources from State-imposed BART requirements. The direct 
cost includes, but is not limited to, capital investments in pollution 
controls, operating and maintenance expenses of the pollution controls, 
and additional fuel expenditures. The EPA believes that these costs 
reflect, as closely as possible, the potential additional costs of the 
BART rule and guidelines to industries with non-EGU sources. However, 
there

[[Page 39150]]

may exist certain costs that EPA has not quantified in these estimates. 
These costs may include costs of transitioning to the BART rule and 
guidelines, such as the costs associated with the retirement of smaller 
or less efficient non-EGUs, employment shifts as workers are retrained 
at the same company or re-employed elsewhere in the economy, and costs 
associated with applying both SO2 and NOX 
controls at one facility at the same time. Costs may be understated 
since the non-EGU cost modeling presumed a least-cost approach, and the 
potentially regulated community may not react in the same manner to 
comply with the rules. Although EPA has not quantified these costs, the 
Agency believes that they are small compared to the quantified costs of 
the program on industries with potentially affected non-EGU sources. 
The annualized cost estimates presented are the best and most accurate 
based upon available information. In a separate analysis, EPA estimates 
the indirect costs and impacts of higher electricity prices and costs 
applicable to the non-EGU sectors on the entire economy [see Regulatory 
Impact Analysis for the Final Clean Visibility Rule, Appendix A (June 
2005)].
    The costs presented here are EPA's best estimate of the direct 
private costs of the BART rule and guidelines. For purposes of benefit-
cost analysis of this rule, EPA has also estimated the additional costs 
of BART using alternate discount rates for calculating the social 
costs, parallel to the range of discount rates used in the estimates of 
the benefits of BART (3 percent and 7 percent). Using these alternate 
discount rates, the social costs of BART range from $0.3 to $2.9 
billion in 2015. (Note the portion of these annual costs associated 
with non-EGU sources represents incremental private cost estimates that 
are used as a proxy for the social costs of the rule.)
    Every benefit-cost analysis examining the potential effects of a 
change in environmental protection requirements is limited to some 
extent by data gaps, limitations in model capabilities (such as 
geographic coverage), and uncertainties in the underlying scientific 
and economic studies used to configure the benefit and cost models. 
Gaps in the scientific literature often result in the inability to 
estimate quantitative changes in health and environmental effects. Gaps 
in the economics literature often result in the inability to assign 
economic values even to those health and environmental outcomes that 
can be quantified. While uncertainties in the underlying scientific and 
economics literatures (that may result in overestimation or 
underestimation of benefits) are discussed in detail in the economic 
analyses and its supporting documents and references, the key 
uncertainties which have a bearing on the results of the benefit-cost 
analysis of this rule include the following:
     Uncertainty concerning actions States will undertake to 
comply with BART;
     EPA's inability to quantify potentially significant 
benefit categories;
     Uncertainties in population growth and baseline incidence 
rates;
     Uncertainties in projection of emissions inventories and 
air quality into the future;
     Uncertainty in the estimated relationships of health and 
welfare effects to changes in pollutant concentrations including the 
shape of the C-R function, the size of the effect estimates, and the 
relative toxicity of the many components of the PM mixture;
     Uncertainties in exposure estimation; and
     Uncertainties associated with the effect of potential 
future actions to limit emissions.
    Despite these uncertainties, we believe the benefit-cost analysis 
provides a reasonable indication of the expected economic benefits of 
the rulemaking in future years under a set of reasonable assumptions.
    In valuing reductions in premature fatalities associated with PM, 
we used a value of $5.5 million per statistical life. This represents a 
central value consistent with a range of values from $1 to $10 million 
suggested by recent meta-analyses of the wage-risk value of statistical 
life (VSL) literature.\87\
---------------------------------------------------------------------------

    \87\ Mrozek, J.R. and L.O. Taylor, What determines the value of 
a life? A Meta Analysis, Journal of Policy Analysis and Management 
21 (2), pp. 253-270.
---------------------------------------------------------------------------

    The benefits estimates generated for this rule are subject to a 
number of assumptions and uncertainties, that are discussed throughout 
the Regulatory Impact Analysis document [Regulatory Impact Analysis for 
the Final Clean Air Visibility Rule (April 2005)]. As Table IV-2 
indicates, total benefits are driven primarily by the reduction in 
premature fatalities each year. Elaborating on the previous uncertainty 
discussion, some key assumptions underlying the primary estimate for 
the premature mortality category include the following:
    (1) EPA assumes inhalation of fine particles is causally associated 
with premature death at concentrations near those experienced by most 
Americans on a daily basis. Plausible biological mechanisms for this 
effect have been hypothesized for the endpoints included in the primary 
analysis and the weight of the available epidemiological evidence 
supports an assumption of causality.
    (2) EPA assumes all fine particles, regardless of their chemical 
composition, are equally potent in causing premature mortality. This is 
an important assumption, because the proportion of certain components 
in the PM mixture produced via precursors emitted from EGUs may differ 
significantly from direct PM released from automotive engines and other 
industrial sources, but no clear scientific grounds exist for 
supporting differential effects estimates by particle type.
    (3) EPA assumes the C-R function for fine particles is 
approximately linear within the range of ambient concentrations under 
consideration. In the PM Criteria Document, EPA recognizes that for 
individuals and specific health responses there are likely threshold 
levels, but there remains little evidence of thresholds for PM-related 
effects in populations.\88\ Where potential threshold levels have been 
suggested, they are at fairly low levels with increasing uncertainty 
about effects at lower ends of the PM2.5 concentration 
ranges. Thus, EPA estimates include health benefits from reducing the 
fine particles in areas with varied concentrations of PM, including 
both regions that are in attainment with fine particle standard and 
those that do not meet the standard.

    \88\ U.S. EPA. (2004). Air Quality Criteria for Particulate 
Matter. Research Triangle Park, NC: National Center for 
Environmental Assessment-RTP Office; Report No. EPA/600/P-99/002aD.
---------------------------------------------------------------------------

The EPA recognizes the difficulties, assumptions, and inherent 
uncertainties in the overall enterprise. The analyses upon which the 
BART rule and guidelines are based were selected from the peer-reviewed 
scientific literature. We used up-to-date assessment tools, and we 
believe the results are highly useful in assessing this rule.
    There are a number of health and environmental effects that we were 
unable to quantify or monetize. A complete benefit-cost analysis of 
BART requires consideration of all benefits and costs expected to 
result from the rule, not just those benefits and costs which could be 
expressed here in dollar terms. A listing of the benefit categories 
that were not quantified or monetized in our estimate are provided in 
Table IV-4. These effects are denoted by ``B'' in Table IV-3 above, and 
are additive to the estimates of benefits.

[[Page 39151]]

4. What Are the Unquantified and Unmonetized Benefits of BART Emissions 
Reductions?
    Important benefits beyond the human health and welfare benefits 
resulting from reductions in ambient levels of PM2.5 and 
ozone are expected to occur from this rule. These other benefits occur 
both directly from NOX and SO2 emissions 
reductions, and indirectly through reductions in co-pollutants such as 
mercury. These benefits are listed in Table IV-4. Some of the more 
important examples include: Reductions in NOX and 
SO2 emissions required by BART will reduce acidification 
and, in the case of NOX, eutrophication of water bodies. 
Reduced nitrate contamination of drinking water is another possible 
benefit of the rule. This final rule will also reduce acid and 
particulate deposition that cause damages to cultural monuments, as 
well as, soiling and other materials damage.
    To illustrate the important nature of benefit categories we are 
currently unable to monetize, we discuss two categories of public 
welfare and environmental impacts related to reductions in emissions 
required by BART: reduced acid deposition and reduced eutrophication of 
water bodies.
a. What Are the Benefits of Reduced Deposition of Sulfur and Nitrogen 
to Aquatic, Forest, and Coastal Ecosystems?
    Atmospheric deposition of sulfur and nitrogen, more commonly known 
as acid rain, occurs when emissions of SO2 and 
NOX react in the atmosphere (with water, oxygen, and 
oxidants) to form various acidic compounds. These acidic compounds fall 
to earth in either a wet form (rain, snow, and fog) or a dry form 
(gases and particles). Prevailing winds can transport acidic compounds 
hundreds of miles, across State borders. Acidic compounds (including 
small particles such as sulfates and nitrates) cause many negative 
environmental effects, including acidification of lakes and streams, 
harm to sensitive forests, and harm to sensitive coastal ecosystems.
i. Acid Deposition and Acidification of Lakes and Streams
    The extent of adverse effects of acid deposition on freshwater and 
forest ecosystems depends largely upon the ecosystem's ability to 
neutralize the acid. The neutralizing ability [key indicator is termed 
Acid Neutralizing Capacity (ANC)] depends largely on the watershed's 
physical characteristics: geology, soils, and size. Waters that are 
sensitive to acidification tend to be located in small watersheds that 
have few alkaline minerals and shallow soils. Conversely, watersheds 
that contain alkaline minerals, such as limestone, tend to have waters 
with a high ANC. Areas especially sensitive to acidification include 
portions of the Northeast (particularly, the Adirondack and Catskill 
Mountains, portions of New England, and streams in the mid-Appalachian 
highlands) and southeastern streams.
ii. Acid Deposition and Forest Ecosystem Impacts
    Current understanding of the effects of acid deposition on forest 
ecosystems focuses on the effects of ecological processes affecting 
plant uptake, retention, and cycling of nutrients within forest 
ecosystems. Recent studies indicate that acid deposition is at least 
partially responsible for decreases in base cations (calcium, 
magnesium, potassium, and others) from soils in the northeastern and 
southeastern United States. Losses of calcium from forest soils and 
forested watersheds have now been documented as a sensitive early 
indicator of soil response to acid deposition for a wide range of 
forest soils in the United States.
    In red spruce stands, a clear link exists between acid deposition, 
calcium supply, and sensitivity to abiotic stress. Red spruce uptake 
and retention of calcium is impacted by acid deposition in two main 
ways: leaching of important stores of calcium from needles and 
decreased root uptake of calcium due to calcium depletion from the soil 
and aluminum mobilization. These changes increase the sensitivity of 
red spruce to winter injuries under normal winter conditions in the 
Northeast, result in the loss of needles, slow tree growth, and impair 
the overall health and productivity of forest ecosystems in many areas 
of the eastern United States. In addition, recent studies of sugar 
maple decline in the Northeast demonstrate a link between low base 
cation availability, high levels of aluminum and manganese in the soil, 
and increased levels of tree mortality due to native defoliating 
insects.
    Although sulfate is the primary cause of base cation leaching, 
nitrate is a significant contributor in watersheds that are nearly 
nitrogen saturated. Base cation depletion is a cause for concern 
because of the role these ions play in surface water acid 
neutralization and their importance as essential nutrients for tree 
growth (calcium, magnesium and potassium).
    This regulatory action will decrease acid deposition in the 
transport region and is likely to have positive effects on the health 
and productivity of forest systems in the region.
iii. Coastal Ecosystems
    Since 1990, a large amount of research has been conducted on the 
impact of nitrogen deposition to coastal waters. Nitrogen is often the 
limiting nutrient in coastal ecosystems. Increasing the levels of 
nitrogen in coastal waters can cause significant changes to those 
ecosystems. In recent decades, human activities have accelerated 
nitrogen nutrient inputs, causing excessive growth of algae and leading 
to degraded water quality and associated impairments of estuarine and 
coastal resources.
    Atmospheric deposition of nitrogen is a significant source of 
nitrogen to many estuaries. The amount of nitrogen entering estuaries 
due to atmospheric deposition varies widely, depending on the size and 
location of the estuarine watershed and other sources of nitrogen in 
the watershed. There are a few estuaries where atmospheric deposition 
of nitrogen contributes well over 40 percent of the total nitrogen 
load; however, in most estuaries for which estimates exist, the 
contribution from atmospheric deposition ranges from 15-30 percent. The 
area of the country with the highest air deposition rates (30 percent 
deposition rates) includes many estuaries along the northeast seaboard 
from Massachusetts to the Chesapeake Bay and along the central Gulf of 
Mexico coast.
    In 1999, National Oceanic and Atmospheric Administration (NOAA) 
published the results of a 5-year national assessment of the severity 
and extent of estuarine eutrophication. An estuary is defined as the 
inland arm of the sea that meets the mouth of a river. The 138 
estuaries characterized in the study represent more than 90 percent of 
total estuarine water surface area and the total number of U.S. 
estuaries. The study found that estuaries with moderate to high 
eutrophication represented 65 percent of the estuarine surface area.
    Eutrophication is of particular concern in coastal areas with poor 
or stratified circulation patterns, such as the Chesapeake Bay, Long 
Island Sound, and the Gulf of Mexico. In such areas, the 
``overproduced'' algae tends to sink to the bottom and decay, using all 
or most of the available oxygen and thereby reducing or eliminating 
populations of bottom-feeder fish and shellfish, distorting the normal 
population balance between different aquatic organisms, and in extreme 
cases, causing dramatic fish kills. Severe and persistent 
eutrophication often directly impacts human activities. For example,

[[Page 39152]]

fishery resource losses can be caused directly by fish kills associated 
with low dissolved oxygen and toxic blooms. Declines in tourism occur 
when low dissolved oxygen causes Noxious smells and floating mats of 
algal blooms create unfavorable aesthetic conditions. Risks to human 
health increase when the toxins from algal blooms accumulate in edible 
fish and shellfish, and when toxins become airborne, causing 
respiratory problems due to inhalation. According to the NOAA report, 
more than half of the nation's estuaries have moderate to high 
expressions of at least one of these symptoms'an indication that 
eutrophication is well developed in more than half of U.S. estuaries.
    This rule is anticipated to reduce nitrogen deposition in the 
nation. Thus, reductions in the levels of nitrogen deposition will have 
a positive impact upon current eutrophic conditions in estuaries and 
coastal areas in the country.
5. Are There Health or Welfare Disbenefits of the BART That Have Not 
Been Quantified?
    In contrast to the additional benefits of the rule discussed above, 
it is also possible that this rule will result in disbenefits in some 
areas of the region. Current levels of nitrogen deposition in these 
areas may provide passive fertilization for forest and terrestrial 
ecosystems where nutrients are a limiting factor and for some 
croplands.
    The effects of ozone and PM on radiative transfer in the atmosphere 
can also lead to effects of uncertain magnitude and direction on the 
penetration of ultraviolet light and climate. Ground level ozone makes 
up a small percentage of total atmospheric ozone (including the 
stratospheric layer) that attenuates penetration of ultraviolet--b 
(UVb) radiation to the ground. The EPA's past evaluation of the 
information indicates that potential disbenefits would be small, 
variable, and with too many uncertainties to attempt quantification of 
relatively small changes in average ozone levels over the course of a 
year (EPA, 2005a). The EPA's most recent provisional assessment of the 
currently available information indicates that potential but 
unquantifiable benefits may also arise from ozone-related attenuation 
of UVb radiation (EPA, 2005b). Sulfate and nitrate particles also 
scatter UVb, which can decrease exposure of horizontal surfaces to UVb, 
but increase exposure of vertical surfaces. In this case as well, both 
the magnitude and direction of the effect of reductions in sulfate and 
nitrate particles are too uncertain to quantify (EPA, 2004). Ozone is a 
greenhouse gas, and sulfates and nitrates can reduce the amount of 
solar radiation reaching the earth, but EPA believes that we are unable 
to quantify any net climate-related disbenefit or benefit associated 
with the combined ozone and PM reductions in this rule.

B. Paperwork Reduction Act

    Today's rule clarifies, but does not modify the information 
collection requirements for BART. Therefore, this action does not 
impose any new information collection burden. However, the OMB has 
previously approved the information collection requirements contained 
in the existing regulations [40 CFR Part 51] under the provisions of 
the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. and has assigned 
OMB control number 2060-0421, EPA ICR number 1813.04. A copy of the OMB 
approved Information Collection Request (ICR) may be obtained from 
Susan Auby, Collection Strategies Division; U.S. Environmental 
Protection Agency (2822T); 1200 Pennsylvania Ave., NW, Washington, DC 
20460 or by calling (202) 566-1672.
    Burden means the total time, effort, or financial resources 
expended by persons to generate, maintain, retain, or disclose or 
provide information to or for a Federal agency. This includes the time 
needed to review instructions; develop, acquire, install, and utilize 
technology and systems for the purposes of collecting, validating, and 
verifying information, processing and maintaining information, and 
disclosing and providing information; adjust the existing ways to 
comply with any previously applicable instructions and requirements; 
train personnel to be able to respond to a collection of information; 
search data sources; complete and review the collection of information; 
and transmit or otherwise disclose the information.
    An agency may not conduct or sponsor, and a person is not required 
to respond to a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for EPA's 
regulations in 40 CFR are listed in 40 CFR part 9.

C. Regulatory Flexibility Act

    EPA has determined that it is not necessary to prepare a regulatory 
flexibility analysis in connection with this final rule.
    For purposes of assessing the impacts of today's rule on small 
entities, small entity is defined as: (1) A small business as defined 
by the Small Business Administrations' regulations at 13 CFR 121.201; 
(2) a small governmental jurisdiction that is a government of a city, 
county, town, school district or special district with a population of 
less than 50,000; and (3) a small organization that is any not-for-
profit enterprise which is independently owned and operated and is not 
dominant in its field.
    Table IV-5 lists potentially impacted BART industry source 
categories and the current applicable small business criteria 
established by the Small Business Administration.

            Table IV-5. Potentially Affected BART Source Categories and Small Business Size Standards
----------------------------------------------------------------------------------------------------------------
               NAICS \a\                         Description                       Size standard \b\
----------------------------------------------------------------------------------------------------------------
221112 \c,d\..........................  Fossil fuel-fired electric     electric output <= 4 million megawatt
                                         utility steam generating       hours.
                                         units.
212112................................  Bituminous Coal Underground    500 Employees.
                                         Mining.
311221................................  Wet Corn Milling.............  750 Employees.
311311................................  Sugarcane Mills..............  500 Employees.
311313................................  Beet Sugar Manufacturing.....  750 Employees.
31214.................................  Distilleries.................  750 Employees.
321212................................  Softwood Veneer and Plywood    500 Employees.
                                         Manufacturing.
322121................................  Paper (except Newsprint)       750 Employees.
                                         Mills (pt).
325188................................  All Other Basic Inorganic      1,000 Employees.
                                         Chemical Manufacturing (pt).
325221................................  Cellulosic Organic Fiber       1,000 Employees.
                                         Manufacturing.
325222................................  Noncellulosic Organic Fiber    1,000 Employees.
                                         Manufacturing.
325182................................  Carbon Black Manufacturing     500 Employees.
                                         (pt).
327213................................  Glass Container Manufacturing  750 Employees.
327212................................  Other Pressed and Blown Glass  750 Employees.
                                         and Glassware Manufacturing.

[[Page 39153]]

 
32731.................................  Cement Manufacturing.........  750 Employees.
32741.................................  Lime Manufacturing...........  500 Employees.
331111................................  Iron and Steel Mills.........  1,000 Employees.
331315................................  Aluminum Sheet, Plate, and     750 Employees.
                                         Foil Manufacturing.
331319................................  Other Aluminum Rolling and     750 Employees.
                                         Drawing.
22121.................................  Natural Gas Distribution.....  500 Employees.
----------------------------------------------------------------------------------------------------------------
\a\ North American Industry Classification System.
\b\ Small Business Administration Size Criteria.
\c\ Include NAICS categories for source categories that own and operate electric generating units only.
\d\ Federal, State, or local government-owned and operated establishments are classified according to the
  activity in which they are engaged.

    After considering the economic impacts of today's final rule on 
small entities, EPA has concluded that this action will not have a 
significant economic impact on a substantial number of small entities. 
This final rule will not impose any direct requirements on small 
entities. The rule would apply to States, not to small entities.
    Courts have interpreted the RFA to require a regulatory flexibility 
analysis only when small entities will be subject to the requirements 
of the rule. See Motor and Equip. Mfrs. Ass'n v. Nichols, 142 F. 3d 449 
(D.C. Cir., 1998); United Distribution Cos. v. FERC, 88 F. 3d 1105, 
1170 (D.C. Cir., 1996); Mid-Tex Elec. Co-op, Inc. v. FERC, 773 F . 2d 
327, 342 (D.C. Cir., 1985) (agency's certification need only consider 
the rule's impact on entities subject to the rule).
    BART requirements in the regional haze rule require BART 
determinations for a select list of major stationary sources defined by 
section 169A(g)(7) of the CAA. However, as noted in the proposed and 
final regional haze rules, the State's determination of BART for 
regional haze involves some State discretion in considering a number of 
factors set forth in section 169A(g)(2), including the costs of 
compliance.
    Further, the final regional haze rule allows States to adopt 
alternative measures in lieu of requiring the installation and 
operation of BART at these major stationary sources. As a result, the 
potential consequences of the BART provisions of the regional haze rule 
(as clarified in today's rule) at specific sources are speculative. Any 
requirements for BART will be established by State rulemakings. The 
States would accordingly exercise substantial intervening discretion in 
implementing the BART requirements of the regional haze rule and 
today's guidelines.
    EPA has undertaken an illustrative analysis to assess the potential 
small business impacts of BART based upon EPA's assessment of the 
actions States may take to comply with the BART rule and guidelines.
    For this final rule, the engineering analysis conducted for the 
rulemaking identified 491 EGU units potentially affected by the outcome 
of this rule. Using unit ORIS \89\ numbers and the Energy Information 
Administration's publicly available 2002 electric generator databases 
(Form EIA 860 and Form EIA 861), we identified utility names, nameplate 
capacity for affected units, and net electricity generation potentially 
affected by this rule. After identifying these units, we excluded units 
that are located in CAIR regions in order to identify those units most 
likely affected by the BART regulatory program. After an assessment of 
the ownership of these remaining units, we identified 2 potentially 
affected small entities in the EGU sector. We used a cost-to-sales 
approach (comparison of expected annual costs of emission controls to 
annual sales revenue or government entity budgets for the affected 
small entity) to assess the potential impacts of BART for these 
affected entities. Using data from the cost analysis, EPA found one of 
these small entities may experience a cost-to-sales ratio of 3 percent 
of sales. The other affected small entity in the EGU sector does not 
face additional compliance costs associated with the rule.
---------------------------------------------------------------------------

    \89\ An ORIS code is a 4 digit number assigned by the Energy 
Information Administration (EIA) at the U.S. Department of Energy to 
power plants owned by utilities.
---------------------------------------------------------------------------

    The engineering analysis conducted for the rulemaking identified 
over 2,000 records associated with affected non-EGU units (all source 
categories listed in table IV-5 other than EGUs--NAICS 221112) 
potentially affected by the rule. Using publicly available sales and 
employment databases, plant names, and locations, we identified 279 
entities and potential owners. In order to classify affected ultimate 
entities as small or large, EPA collected information on facility 
names, parent company sales, and parent company employment data. Data 
were compared with the appropriate size standard and entities were 
classified as small or large according to Small Business 
Administration's definitions. For example, ultimate parent companies of 
cement producers with employment exceeding 750 employees were 
classified as large companies. This process identified 36 small 
companies and 195 large companies potentially impacted as a result 
promulgating this rule. The remaining 48 entities were either 
government-owned (25 entities, primarily state universities) or parent 
ownership could not be definitively identified using available 
databases (23 entities).
    Using the cost-to-sales approach described above, EPA found that 
five non-EGU source category small entities may potentially be affected 
at or above 3 percent. Two entities may be affected between one and 
three percent, and the remaining small entity cost-to-sales ratios are 
below one percent. The median cost-to-sales ratio for non-EGU source 
category small entities is estimated to be 0.3 percent and could 
potentially range from 0 to 20 percent. As previously discussed this 
analysis is illustrative and based upon EPA's assessment of actions 
States are likely to take as a result of the BART rule and guidelines 
promulgated today.

D. Unfunded Mandates Reform Act

    Title II of the Unfunded Mandates Reform Act of 1995 (Public Law 
104-4) establishes requirements for Federal agencies to assess the 
effects of their regulatory actions on State, local, and Tribal 
governments and the private sector. Under section 202 of UMRA, 2 U.S.C. 
1532, EPA generally must prepare a written statement, including a cost-
benefit analysis, for any proposed or final rule that ``includes any 
Federal mandate that may result in the expenditure by State, local, and 
tribal governments, in the aggregate, or by the private sector, of 
$100,000,000 or more * * * in any one year.'' A ``Federal

[[Page 39154]]

mandate'' is defined under section 421(6), 2 U.S.C. 658(6), to include 
a ``Federal intergovernmental mandate.'' A ``Federal intergovernmental 
mandate,'' in turn, is defined to include a regulation that ``would 
impose an enforceable duty upon State, local, or tribal governments,'' 
section 421(5)(A)(I), 2 U.S.C. 658(5)(A)(I). A ``Federal private sector 
mandate'' includes a regulation that ``would impose an enforceable duty 
upon the private sector,'' with certain exceptions, section 421(7)(A), 
2 U.S.C. 658(7)(A).
    Before promulgating an EPA rule for which a written statement is 
needed under section 202 of UMRA, section 205, 2 U.S.C. 1535, of UMRA 
generally requires EPA to identify and consider a reasonable number of 
regulatory alternatives and adopt the least costly, most cost 
effective, or least burdensome alternative that achieves the objectives 
of the rule.The RIA prepared by EPA and placed in the docket for this 
rulemaking is consistent with the requirements of section 202 of the 
UMRA. Furthermore, EPA is not directly establishing any regulatory 
requirements that may significantly or uniquely affect small 
governments, including tribal governments. Thus, EPA is not obligated 
to develop under section 203 of the UMRA a small government agency 
plan. Further, EPA carried out consultations with the governmental 
entities affected by this rule in a manner consistent with the 
intergovernmental consultation provisions of section 204 of the UMRA.
    The EPA also believes that today's rule meets the UMRA requirement 
in section 205 to select the least costly and burdensome alternative in 
light of the statutory mandate for BART. As explained above, we are 
promulgating the BART rule and guidelines following the D.C. Circuit's 
remand of the BART provisions in the 1999 regional haze rule. The 1999 
regional haze rule provides substantial flexibility to the States, 
allowing them to adopt alternative measures such as a trading program 
in lieu of requiring the installation and operation of BART. The 
provisions governing such alternative measures were affected by a more 
recent decision of the D.C. Circuit and will be revised in a separate 
rulemaking process. Today's rule will not restrict the ability of the 
States to adopt such alternatives measures once those revisions to the 
regional haze rule have been made final. This will provide an 
alternative to BART that gives States the ability to choose the least 
costly and least burdensome alternative. Today's rule also allows 
States affected by the Clean Air Interstate Rule to utilize emission 
reductions achieved by EGUs under that rule to satisfy BART 
requirements for those sources. This will provide those States with 
another cost effective and less burdensome alternative to BART.
    The EPA is not reaching a final conclusion as to the applicability 
of UMRA to today's rulemaking action. The reasons for this are 
discussed in the 1999 regional haze rule (64 FR 35762) and in the 2001 
BART guidelines proposal (66 FR 38111-38112). Notwithstanding this, the 
discussion in chapter 9 of the RIA constitutes the UMRA statement that 
would be required by UMRA if its statutory provisions applied. 
Consequently, we continue to believe that it is not necessary to reach 
a conclusion as to the applicability of the UMRA requirements.

E. Executive Order 13132: Federalism

    Executive Order 13132, entitled Federalism (64 FR 43255, August 10, 
1999), requires EPA to develop an accountable process to ensure 
``meaningful and timely input by State and local officials in the 
development of regulatory policies that have federalism implications.'' 
Such policies are defined in the Executive Order to include regulations 
that have ``substantial direct effects on the States, on the 
relationship between the national government and the States, or on the 
distribution of power and responsibilities among the various levels of 
government.'' Under section 6 of Executive Order 13132, EPA may not 
issue a regulation that has federalism implications, that imposes 
substantial direct compliance costs, and that is not required by 
statute, unless the Federal government provides the funds necessary to 
pay the direct compliance costs incurred by State and local 
governments, or EPA consults with State and local officials early in 
the process of developing the regulation. The EPA also may not issue a 
regulation that has federalism implications and that preempts State law 
unless EPA consults with State and local officials early in the process 
of developing the regulation.
    We have concluded that today's action, promulgating the BART 
guidelines, will not have federalism implications, as specified in 
section 6 of the Executive Order 13132 (64 FR 43255, August 10, 1999) 
because it will not have substantial direct effects on the States, nor 
substantially alter the relationship or the distribution of power and 
responsibilities between the States and the Federal government. 
Nonetheless, we consulted with a wide scope of State and local 
officials, including the National Governors Association, the National 
League of Cities, the National Conference of State Legislatures, the U. 
S. Conference of Mayors, the National Association of Counties, the 
Council of State Governments, the International City/County Management 
Association, and the National Association of Towns and Townships during 
the course of developing this rule.

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

    Executive Order 13175, entitled ``Consultation and Coordination 
with Indian Tribal Governments'' (65 FR 67249, November 9, 2000), 
requires EPA to develop an accountable process to ensure ``meaningful 
and timely input by Tribal officials in the development of regulatory 
policies that have Tribal implications.''
    This rule does not have Tribal implications as defined by Executive 
Order 13175. It does not have a substantial direct effect on one or 
more Indian Tribes. Furthermore, this rule does not affect the 
relationship or distribution of power and responsibilities between the 
Federal government and Indian Tribes. The CAA and the TAR establish the 
relationship of the Federal government and Tribes in developing plans 
to address air quality issues, and this rule does nothing to modify 
that relationship. This rule does not have Tribal implications, and 
Executive Order 13175 does not apply to this rulemaking.

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

    Executive Order 13045, ``Protection of Children from Environmental 
Health Risks and Safety Risks'' (62 FR 19885, April 23, 1997) applies 
to any rule that (1) is determined to be ``economically significant'' 
as defined under Executive Order 12866 and (2) concerns an 
environmental health or safety risk that EPA has reason to believe may 
have a disproportionate effect on children. If the regulatory action 
meets both criteria, Section 5-501 of the Order directs the Agency to 
evaluate the environmental health or safety effects of the planned rule 
on children and to explain why the planned regulation is preferable to 
other potentially effective and reasonably feasible alternatives 
considered by the Agency.
    EPA interprets Executive Order 13045 as applying only to those 
regulatory actions that are based on health and safety risks, such that 
the analysis required under section 5-501 of the

[[Page 39155]]

Order has the potential to influence the regulation. The BART rule and 
guidelines are not subject to the Executive Order because the rule and 
guidelines do not involve decisions on environmental health or safety 
risks that may disproportionately affect children. The EPA believes 
that the emissions reductions from the control strategies considered in 
this rulemaking will further improve air quality and will further 
improve children's health.

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

    We have conducted a Regulatory Impact Analysis for this rule, that 
includes an analysis of energy impacts and is contained in the docket 
(Docket No. OAR-2002-0076). This rule is not a ``significant energy 
action'' as defined in Executive Order 13211, ``Actions Concerning 
Regulations That Significantly Affect Energy Supply, Distribution, or 
Use'' (66 FR 28355 (May 22, 2001)) because it is not likely to have a 
significant adverse effect on the supply, distribution, or use of 
energy. This rule is not a ``significant energy action,'' because it 
will have less than a 1 percent impact on the cost of energy production 
and does not exceed other factors described by OMB that may indicate a 
significant adverse effect. (See, ``Guidance for Implementing E.O. 
13211,'' OMB Memorandum 01-27 (July 13, 2001) http://www.whitehouse.gov/omb/memoranda/m01-27.html.) Specifically, the 
presumptive requirements for EGUs for this rule, when fully 
implemented, are expected have a 0.25 percent impact on the cost of 
energy production for the nation in 2015. States must use the 
guidelines in making BART determinations for power plants with a 
generating capacity in excess of 750 MW. Our analysis evaluates the 
impact of the presumptive requirements for these sources and does not 
consider any possible additional controls for EGU sources or non-EGU 
sources that States may require. Although States may choose to use the 
guidelines in establishing BART limits for non-EGUs , ultimately States 
will determine the sources subject to BART and the appropriate level of 
control for such sources.
    We are finalizing today's rule following the D.C. Circuit's remand 
of the BART provisions in the 1999 regional haze rule. The 1999 
regional haze rule provides substantial flexibility to the States, 
allowing them to adopt alternative measures such as a trading program 
in lieu of requiring the installation and operation of BART. The 
provisions governing such alternative measures were affected by a more 
recent decision of the D.C. Circuit and will be revised in a separate 
rulemaking process. This rulemaking will not restrict the ability of 
the States to adopt alternative measures once those revisions to the 
regional haze rule have been made final. This will provide an 
alternative to BART that reduces the overall cost of the regulation and 
its impact on the energy supply. Today's rule also allows States 
affected by the Clean Air Interstate Rule to utilize emission 
reductions achieved by EGUs under that rule to satisfy BART 
requirements for those sources. This will provide those States with 
another cost effective and less burdensome alternative to BART. The 
BART rule itself offers flexibility by offering the choice of meeting 
SO2 requirements between an emission rate and a removal 
rate.
    For a State that chooses to require case-by-case BART, today's rule 
would establish presumptive levels of controls for SO2 and 
NOX for certain EGUs that the State finds are subject to 
BART. Based on its consideration of various factors set forth in the 
regulations; however, a State may conclude that a different level of 
control is appropriate. The States will accordingly exercise 
substantial intervening discretion in implementing the final rule. 
Additionally, we have assessed that the compliance dates for the rule 
will provide adequate time for EGUs to install the required emission 
controls.

I. National Technology Transfer and Advancement Act

    Section 12(d) of the National Technology Transfer Advancement Act 
of 1995 (NTTAA), Public Law 104-113, section 12(d)(15 U.S.C. 272 note) 
directs EPA to use voluntary consensus standards (VCS) in its 
regulatory activities unless to do so would be inconsistent with 
applicable law or otherwise impractical. Voluntary consensus standards 
are technical standards (e.g., materials specifications, test methods, 
sampling procedures, and business practices) that are developed or 
adopted by VCS bodies. The NTTAA directs EPA to provide Congress, 
through OMB, explanations when the EPA decides not to use VCS.
    This action does not involve technical standards; thus, EPA did not 
consider the use of any VCS.

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

    Executive Order 12898, ``Federal Actions to Address Environmental 
Justice in Minority Populations and Low-Income Populations,'' requires 
federal agencies to consider the impact of programs, policies, and 
activities on minority populations and low-income populations. 
According to EPA guidance,\90\ agencies are to assess whether minority 
or low-income populations face risks or a rate of exposure to hazards 
that are significant and that ``appreciably exceed or is likely to 
appreciably exceed the risk or rate to the general population or to the 
appropriate comparison group.'' (EPA, 1998)
---------------------------------------------------------------------------

    \90\ U.S. Environmental Protection Agency, 1998. Guidance for 
Incorporating Environmental Justice Concerns in EPA's NEPA 
Compliance Analyses. Office of Federal Activities, Washington, D.C., 
April, 1998.
---------------------------------------------------------------------------

    In accordance with Executive Order 12898, the Agency has considered 
whether this rule may have disproportionate negative impacts on 
minority or low income populations. Negative impacts to these sub-
populations that appreciably exceed similar impacts to the general 
population are not expected because the Agency expects this rule to 
lead to reductions in air pollution emissions and exposures generally.

K. Congressional Review Act

    The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the 
Small Business Regulatory Enforcement Fairness Act of 1996, generally 
provides that before a rule may take effect, the agency promulgating 
the rule must submit a rule report, which includes a copy of the rule, 
to each House of the Congress and to the Comptroller General of the 
United States. The EPA will submit a report containing this rule and 
other required information to the U.S. Senate, the U.S. House of 
Representatives, and the Comptroller General of the United States prior 
to publication of the rule in the Federal Register. A major rule cannot 
take effect until 60 days after it is published in the Federal 
Register. This action is a ``major rule'' as defined by 5 U.S.C. 
804(2).

List of Subjects in 40 CFR Part 51

    Environmental protection, Air pollution control, Administrative 
practice and procedure, Intergovernmental relations, Lead, Nitrogen 
dioxide, Ozone, Particulate matter, Reporting and recordkeeping

[[Page 39156]]

requirements, Sulfur oxides, Volatile organic compounds.

    Dated: June 15, 2005.
Stephen L. Johnson,
Administrator.

0
For the reasons set forth in the preamble, part 51 of chapter I of 
title 40 of the Code of Federal Regulations is amended as follows:

PART 51--REQUIREMENTS FOR PREPARATION, ADOPTION, AND SUBMITTAL OF 
IMPLEMENTATION PLANS

0
1. The authority citation for part 51 continues to read as follows:

    Authority: 23 U.S.C. 101; 42 U.S.C. 7410-7671q.


0
2. Section 51.302 is amended by revising paragraph (c)(4)(iii) to read 
as follows:


Sec.  51.302  Implementation control strategies for reasonably 
attributable visibility impairment.

* * * * *
    (c) * * *
    (4) * * *
    (iii) BART must be determined for fossil-fuel fired generating 
plants having a total generating capacity in excess of 750 megawatts 
pursuant to ``Guidelines for Determining Best Available Retrofit 
Technology for Coal-fired Power Plants and Other Existing Stationary 
Facilities'' (1980), which is incorporated by reference, exclusive of 
appendix E to the Guidelines, except that options more stringent than 
NSPS must be considered. Establishing a BART emission limitation 
equivalent to the NSPS level of control is not a sufficient basis to 
avoid the analysis of control options required by the guidelines. This 
document is EPA publication No. 450/3-80-009b and has been approved for 
incorporation by reference by the Director of the Federal Register in 
accordance with 5 U.S.C. 552(a) and 1 CFR part 51. It is for sale from 
the U.S. Department of Commerce, National Technical Information 
Service, 5285 Port Royal Road, Springfield, Virginia 22161. It is also 
available for inspection from the National Archives and Records 
Administration (NARA). For information on the availability of this 
material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/index.html.
* * * * *

0
3. Section 51.308 is amended by revising paragraph (b), removing and 
reserving paragraph (c), revising paragraphs (e)(1)(ii), (e)(3), and 
(e)(4), and adding paragaphs (e)(5) and (6) to read as follows:


Sec.  51.308  Regional haze program requirements.

* * * * *
    (b) When are the first implementation plans due under the regional 
haze program? Except as provided in Sec.  51.309(c), each State 
identified in Sec.  51.300(b)(3) must submit, for the entire State, an 
implementation plan for regional haze meeting the requirements of 
paragraphs (d) and (e) of this section no later than December 17, 2007.
    (c) [Reserved]
* * * * *
    (e) * * *
    (1) * * *
    (ii) A determination of BART for each BART-eligible source in the 
State that emits any air pollutant which may reasonably be anticipated 
to cause or contribute to any impairment of visibility in any mandatory 
Class I Federal area. All such sources are subject to BART.
    (A) The determination of BART must be based on an analysis of the 
best system of continuous emission control technology available and 
associated emission reductions achievable for each BART-eligible source 
that is subject to BART within the State. In this analysis, the State 
must take into consideration the technology available, the costs of 
compliance, the energy and nonair quality environmental impacts of 
compliance, any pollution control equipment in use at the source, the 
remaining useful life of the source, and the degree of improvement in 
visibility which may reasonably be anticipated to result from the use 
of such technology.
    (B) The determination of BART for fossil-fuel fired power plants 
having a total generating capacity greater than 750 megawatts must be 
made pursuant to the guidelines in appendix Y of this part (Guidelines 
for BART Determinations Under the Regional Haze Rule).
    (C) Exception. A State is not required to make a determination of 
BART for SO2 or for NOX if a BART-eligible source 
has the potential to emit less than 40 tons per year of such 
pollutant(s), or for PM10 if a BART-eligible source emits 
less than 15 tons per year of such pollutant.
* * * * *
    (3) A State which opts under 40 CFR 51.308(e)(2) to implement an 
emissions trading program or other alternative measure rather than to 
require sources subject to BART to install, operate, and maintain BART 
may satisfy the final step of the demonstration required by that 
section as follows: If the distribution of emissions is not 
substantially different than under BART, and the alternative measure 
results in greater emission reductions, then the alternative measure 
may be deemed to achieve greater reasonable progress. If the 
distribution of emissions is significantly different, the State must 
conduct dispersion modeling to determine differences in visibility 
between BART and the trading program for each impacted Class I area, 
for the worst and best 20 percent of days. The modeling would 
demonstrate ``greater reasonable progress'' if both of the following 
two criteria are met:
    (i) Visibility does not decline in any Class I area, and
    (ii) There is an overall improvement in visibility, determined by 
comparing the average differences between BART and the alternative over 
all affected Class I areas.
    (4) A State that opts to participate in the Clean Air Interstate 
Rule cap-and-trade and trade program under part 96 AAA-EEE need not 
require affected BART-eligible EGU's to install, operate, and maintain 
BART. A State that chooses this option may also include provisions for 
a geographic enhancement to the program to address the requirement 
under Sec.  51.302(c) related to BART for reasonably attributable 
impairment from the pollutants covered by the CAIR cap-and-trade 
program.
    (5) After a State has met the requirements for BART or implemented 
emissions trading program or other alternative measure that achieves 
more reasonable progress than the installation and operation of BART, 
BART-eligible sources will be subject to the requirements of paragraph 
(d) of this section in the same manner as other sources.
    (6) Any BART-eligible facility subject to the requirement under 
paragraph (e) of this section to install, operate, and maintain BART 
may apply to the Administrator for an exemption from that requirement. 
An application for an exemption will be subject to the requirements of 
Sec.  51.303(a)(2)-(h).
* * * * *

0
4. Appendix Y to Part 51 is added to read as follows:

Appendix Y to Part 51--Guidelines for BART Determinations Under the 
Regional Haze Rule

Table of Contents

I. Introduction and Overview
    A. What is the purpose of the guidelines?
    B. What does the CAA require generally for improving visibility?
    C. What is the BART requirement in the CAA?
    D. What types of visibility problems does EPA address in its 
regulations?

[[Page 39157]]

    E. What are the BART requirements in EPA's regional haze 
regulations?
    F. What is included in the guidelines?
    G. Who is the target audience for the guidelines?
    H. Do EPA regulations require the use of these guidelines?
II. How to Identify BART-eligible Sources
    A. What are the steps in identifying BART-eligible sources?
    1. Step 1: Identify emission units in the BART categories
    2. Step 2: Identify the start-up dates of the emission units
    3. Step 3: Compare the potential emissions to the 250 ton/yr 
cutoff
    4. Final step: Identify the emission units and pollutants that 
constitute the BART-eligible source.
III. How to Identify Sources ``Subject to BART''
IV. The BART Determination: Analysis of BART Options
    A. What factors must I address in the BART Analysis?
    B. What is the scope of the BART review?
    C. How does a BART review relate to maximum achievable control 
technology (MACT) standards under CAA section 112?
    D. What are the five basic steps of a case-by-case BART 
analysis?
    1. Step 1: How do I identify all available retrofit emission 
control techniques?
    2. Step 2: How do I determine whether the options identified in 
Step 1 are technically feasible?
    3. Step 3: How do I evaluate technically feasible alternatives?
    4. Step 4: For a BART review, what impacts am I expected to 
calculate and report? What methods does EPA recommend for the 
impacts analyses?
    a. Impact analysis part 1: how do I estimate the costs of 
control?
    b. What do we mean by cost effectiveness?
    c. How do I calculate average cost effectiveness?
    d. How do I calculate baseline emissions?
    e. How do I calculate incremental cost effectiveness?
    f. What other information should I provide in the cost impacts 
analysis?
    g. What other things are important to consider in the cost 
impacts analysis?
    h. Impact analysis part 2: How should I analyze and report 
energy impacts?
    i. Impact analysis part 3: How do I analyze ``non-air quality 
environmental impacts?''
    j. Impact analysis part 4: What are examples of non-air quality 
environmental impacts?
    k. How do I take into account a project's ``remaining useful 
life'' in calculating control costs?
    5. Step 5: How should I determine visibility impacts in the BART 
determination?
    E. How do I select the ``best'' alternative, using the results 
of Steps 1 through 5?
    1. Summary of the impacts analysis
    2. Selecting a ``best'' alternative
    3. In selecting a ``best'' alternative, should I consider the 
affordability of controls?
    4. SO2 limits for utility boilers
    5. NOX limits for utility boilers
V. Enforceable Limits/Compliance Date

I. Introduction and Overview

A. What is the purpose of the guidelines?

    The Clean Air Act (CAA), in sections 169A and 169B, contains 
requirements for the protection of visibility in 156 scenic areas 
across the United States. To meet the CAA's requirements, we 
published regulations to protect against a particular type of 
visibility impairment known as ``regional haze.'' The regional haze 
rule is found in this part at 40 CFR 51.300 through 51.309. These 
regulations require, in 40 CFR 51.308(e), that certain types of 
existing stationary sources of air pollutants install best available 
retrofit technology (BART). The guidelines are designed to help 
States and others (1) identify those sources that must comply with 
the BART requirement, and (2) determine the level of control 
technology that represents BART for each source.

B. What does the CAA require generally for improving visibility?

    Section 169A of the CAA, added to the CAA by the 1977 
amendments, requires States to protect and improve visibility in 
certain scenic areas of national importance. The scenic areas 
protected by section 169A are ``the mandatory Class I Federal Areas 
* * * where visibility is an important value.'' In these guidelines, 
we refer to these as ``Class I areas.'' There are 156 Class I areas, 
including 47 national parks (under the jurisdiction of the 
Department of Interior--National Park Service), 108 wilderness areas 
(under the jurisdiction of the Department of the Interior--Fish and 
Wildlife Service or the Department of Agriculture--U.S. Forest 
Service), and one International Park (under the jurisdiction of the 
Roosevelt-Campobello International Commission). The Federal Agency 
with jurisdiction over a particular Class I area is referred to in 
the CAA as the Federal Land Manager. A complete list of the Class I 
areas is contained in 40 CFR 81.401 through 81.437, and you can find 
a map of the Class I areas at the following Internet site: http://www.epa.gov/ttn/oarpg/t1/fr_notices/classimp.gif.
    The CAA establishes a national goal of eliminating man-made 
visibility impairment from all Class I areas. As part of the plan 
for achieving this goal, the visibility protection provisions in the 
CAA mandate that EPA issue regulations requiring that States adopt 
measures in their State implementation plans (SIPs), including long-
term strategies, to provide for reasonable progress towards this 
national goal. The CAA also requires States to coordinate with the 
Federal Land Managers as they develop their strategies for 
addressing visibility.

C. What is the BART requirement in the CAA?

    1. Under section 169A(b)(2)(A) of the CAA, States must require 
certain existing stationary sources to install BART. The BART 
provision applies to ``major stationary sources'' from 26 identified 
source categories which have the potential to emit 250 tons per year 
or more of any air pollutant. The CAA requires only sources which 
were put in place during a specific 15-year time interval to be 
subject to BART. The BART provision applies to sources that existed 
as of the date of the 1977 CAA amendments (that is, August 7, 1977) 
but which had not been in operation for more than 15 years (that is, 
not in operation as of August 7, 1962).
    2. The CAA requires BART review when any source meeting the 
above description ``emits any air pollutant which may reasonably be 
anticipated to cause or contribute to any impairment of visibility'' 
in any Class I area. In identifying a level of control as BART, 
States are required by section 169A(g) of the CAA to consider:
    (a) The costs of compliance,
    (b) The energy and non-air quality environmental impacts of 
compliance,
    (c) Any existing pollution control technology in use at the 
source,
    (d) The remaining useful life of the source, and
    (e) The degree of visibility improvement which may reasonably be 
anticipated from the use of BART.
    3. The CAA further requires States to make BART emission 
limitations part of their SIPs. As with any SIP revision, States 
must provide an opportunity for public comment on the BART 
determinations, and EPA's action on any SIP revision will be subject 
to judicial review.

D. What types of visibility problems does EPA address in its 
regulations?

    1. We addressed the problem of visibility in two phases. In 
1980, we published regulations addressing what we termed 
``reasonably attributable'' visibility impairment. Reasonably 
attributable visibility impairment is the result of emissions from 
one or a few sources that are generally located in close proximity 
to a specific Class I area. The regulations addressing reasonably 
attributable visibility impairment are published in 40 CFR 51.300 
through 51.307.
    2. On July 1, 1999, we amended these regulations to address the 
second, more common, type of visibility impairment known as 
``regional haze.'' Regional haze is the result of the collective 
contribution of many sources over a broad region. The regional haze 
rule slightly modified 40 CFR 51.300 through 51.307, including the 
addition of a few definitions in Sec.  51.301, and added new 
Sec. Sec.  51.308 and 51.309.

E. What are the BART requirements in EPA's regional haze 
regulations?

    1. In the July 1, 1999 rulemaking, we added a BART requirement 
for regional haze. We amended the BART requirements in 2005. You 
will find the BART requirements in 40 CFR 51.308(e). Definitions of 
terms used in 40 CFR 51.308(e)(1) are found in 40 CFR 51.301.
    2. As we discuss in detail in these guidelines, the regional 
haze rule codifies and clarifies the BART provisions in the CAA. The 
rule requires that States identify and list ``BART-eligible 
sources,'' that is, that States identify and list those sources that 
fall within the 26 source categories, were put in place during the 
15-year window of time from 1962 to 1977, and have potential

[[Page 39158]]

emissions greater than 250 tons per year. Once the State has 
identified the BART-eligible sources, the next step is to identify 
those BART-eligible sources that may ``emit any air pollutant which 
may reasonably be anticipated to cause or contribute to any 
impairment of visibility.'' Under the rule, a source which fits this 
description is ``subject to BART.'' For each source subject to BART, 
40 CFR 51.308(e)(1)(ii)(A) requires that States identify the level 
of control representing BART after considering the factors set out 
in CAA section 169A(g), as follows:

--States must identify the best system of continuous emission 
control technology for each source subject to BART taking into 
account the technology available, the costs of compliance, the 
energy and non-air quality environmental impacts of compliance, any 
pollution control equipment in use at the source, the remaining 
useful life of the source, and the degree of visibility improvement 
that may be expected from available control technology.

    3. After a State has identified the level of control 
representing BART (if any), it must establish an emission limit 
representing BART and must ensure compliance with that requirement 
no later than 5 years after EPA approves the SIP. States may 
establish design, equipment, work practice or other operational 
standards when limitations on measurement technologies make emission 
standards infeasible.

F. What is included in the guidelines?

    1. The guidelines provide a process for making BART 
determinations that States can use in implementing the regional haze 
BART requirements on a source-by-source basis, as provided in 40 CFR 
51.308(e)(1). States must follow the guidelines in making BART 
determinations on a source-by-source basis for 750 megawatt (MW) 
power plants but are not required to use the process in the 
guidelines when making BART determinations for other types of 
sources.
    2. The BART analysis process, and the contents of these 
guidelines, are as follows:
    (a) Identification of all BART-eligible sources. Section II of 
these guidelines outlines a step-by-step process for identifying 
BART-eligible sources.
    (b) Identification of sources subject to BART. As noted above, 
sources ``subject to BART'' are those BART-eligible sources which 
``emit a pollutant which may reasonably be anticipated to cause or 
contribute to any impairment of visibility in any Class I area.'' We 
discuss considerations for identifying sources subject to BART in 
section III of the guidance.
    (c) The BART determination process. For each source subject to 
BART, the next step is to conduct an analysis of emissions control 
alternatives. This step includes the identification of available, 
technically feasible retrofit technologies, and for each technology 
identified, an analysis of the cost of compliance, the energy and 
non-air quality environmental impacts, and the degree of visibility 
improvement in affected Class I areas resulting from the use of the 
control technology. As part of the BART analysis, the State should 
also take into account the remaining useful life of the source and 
any existing control technology present at the source. For each 
source, the State will determine a ``best system of continuous 
emission reduction'' based upon its evaluation of these factors. 
Procedures for the BART determination step are described in section 
IV of these guidelines.
    (d) Emissions limits. States must establish emission limits, 
including a deadline for compliance, consistent with the BART 
determination process for each source subject to BART. 
Considerations related to these limits are discussed in section V of 
these guidelines.

G. Who is the target audience for the guidelines?

    1. The guidelines are written primarily for the benefit of 
State, local and Tribal agencies, and describe a process for making 
the BART determinations and establishing the emission limitations 
that must be included in their SIPs or Tribal implementation plans 
(TIPs). Throughout the guidelines, which are written in a question 
and answer format, we ask questions ``How do I * * *? '' and answer 
with phrases ``you should * * *, you must * * * '' The ``you'' means 
a State, local or Tribal agency conducting the analysis. We have 
used this format to make the guidelines simpler to understand, but 
we recognize that States have the authority to require source owners 
to assume part of the analytical burden, and that there will be 
differences in how the supporting information is collected and 
documented. We also recognize that data collection, analysis, and 
rule development may be performed by Regional Planning 
Organizations, for adoption within each SIP or TIP.
    2. The preamble to the 1999 regional haze rule discussed at 
length the issue of Tribal implementation of the requirements to 
submit a plan to address visibility. As explained there, 
requirements related to visibility are among the programs for which 
Tribes may be determined eligible and receive authorization to 
implement under the ``Tribal Authority Rule'' (``TAR'') (40 CFR 49.1 
through 49.11). Tribes are not subject to the deadlines for 
submitting visibility implementation plans and may use a modular 
approach to CAA implementation. We believe there are very few BART-
eligible sources located on Tribal lands. Where such sources exist, 
the affected Tribe may apply for delegation of implementation 
authority for this rule, following the process set forth in the TAR.

H. Do EPA regulations require the use of these guidelines?

    Section 169A(b) requires us to issue guidelines for States to 
follow in establishing BART emission limitations for fossil-fuel 
fired power plants having a capacity in excess of 750 megawatts. 
This document fulfills that requirement, which is codified in 40 CFR 
51.308(e)(1)(ii)(B). The guidelines establish an approach to 
implementing the requirements of the BART provisions of the regional 
haze rule; we believe that these procedures and the discussion of 
the requirements of the regional haze rule and the CAA should be 
useful to the States. For sources other than 750 MW power plants, 
however, States retain the discretion to adopt approaches that 
differ from the guidelines.

II. How to Identify BART-Eligible Sources

    This section provides guidelines on how to identify BART-
eligible sources. A BART-eligible source is an existing stationary 
source in any of 26 listed categories which meets criteria for 
startup dates and potential emissions.

A. What are the steps in identifying BART-eligible sources?

    Figure 1 shows the steps for identifying whether the source is a 
``BART-eligible source:''
    Step 1: Identify the emission units in the BART categories,
    Step 2: Identify the start-up dates of those emission units, and
    Step 3: Compare the potential emissions to the 250 ton/yr 
cutoff.
    Figure 1. How to determine whether a source is BART-eligible:
    Step 1: Identify emission units in the BART categories

Does the plant contain emissions units in one or more of the 26 
source categories?
     [rtarr2] No [rtarr2] Stop
     [rtarr2] Yes [rtarr2] Proceed to Step 2

    Step 2: Identify the start-up dates of these emission units

Do any of these emissions units meet the following two tests?
    In existence on August 7, 1977
     AND
    Began operation after August 7, 1962
     [rtarr2] No [rtarr2] Stop
     [rtarr2] Yes [rtarr2] Proceed to Step 3

    Step 3: Compare the potential emissions from these emission 
units to the 250 ton/yr cutoff

    Identify the ``stationary source'' that includes the emission 
units you identified in Step 2.
    Add the current potential emissions from all the emission units 
identified in Steps 1 and 2 that are included within the 
``stationary source'' boundary.
    Are the potential emissions from these units 250 tons per year 
or more for any visibility-impairing pollutant?
     [rtarr2] No [rtarr2] Stop
     [rtarr2] Yes [rtarr2] These emissions units comprise the 
``BART-eligible source.''

1. Step 1: Identify Emission Units in the BART Categories

    1. The BART requirement only applies to sources in specific 
categories listed in the CAA. The BART requirement does not apply to 
sources in other source categories, regardless of their emissions. 
The listed categories are:
    (1) Fossil-fuel fired steam electric plants of more than 250 
million British thermal units (BTU) per hour heat input,
    (2) Coal cleaning plants (thermal dryers),
    (3) Kraft pulp mills,
    (4) Portland cement plants,
    (5) Primary zinc smelters,
    (6) Iron and steel mill plants,
    (7) Primary aluminum ore reduction plants,

[[Page 39159]]

    (8) Primary copper smelters,
    (9) Municipal incinerators capable of charging more than 250 
tons of refuse per day,
    (10) Hydrofluoric, sulfuric, and nitric acid plants,
    (11) Petroleum refineries,
    (12) Lime plants,
    (13) Phosphate rock processing plants,
    (14) Coke oven batteries,
    (15) Sulfur recovery plants,
    (16) Carbon black plants (furnace process),
    (17) Primary lead smelters,
    (18) Fuel conversion plants,
    (19) Sintering plants,
    (20) Secondary metal production facilities,
    (21) Chemical process plants,
    (22) Fossil-fuel boilers of more than 250 million BTUs per hour 
heat input,
    (23) Petroleum storage and transfer facilities with a capacity 
exceeding 300,000 barrels,
    (24) Taconite ore processing facilities,
    (25) Glass fiber processing plants, and
    (26) Charcoal production facilities.
    2. Some plants may have emission units from more than one 
category, and some emitting equipment may fit into more than one 
category. Examples of this situation are sulfur recovery plants at 
petroleum refineries, coke oven batteries and sintering plants at 
steel mills, and chemical process plants at refineries. For Step 1, 
you identify all of the emissions units at the plant that fit into 
one or more of the listed categories. You do not identify emission 
units in other categories.

    Example:  A mine is collocated with an electric steam generating 
plant and a coal cleaning plant. You would identify emission units 
associated with the electric steam generating plant and the coal 
cleaning plant, because they are listed categories, but not the 
mine, because coal mining is not a listed category.

    3. The category titles are generally clear in describing the 
types of equipment to be listed. Most of the category titles are 
very broad descriptions that encompass all emission units associated 
with a plant site (for example, ``petroleum refining'' and ``kraft 
pulp mills''). This same list of categories appears in the PSD 
regulations. States and source owners need not revisit any 
interpretations of the list made previously for purposes of the PSD 
program. We provide the following clarifications for a few of the 
category titles:
    (1) ``Steam electric plants of more than 250 million BTU/hr heat 
input.'' Because the category refers to ``plants,'' we interpret 
this category title to mean that boiler capacities should be 
aggregated to determine whether the 250 million BTU/hr threshold is 
reached. This definition includes only those plants that generate 
electricity for sale. Plants that cogenerate steam and electricity 
also fall within the definition of ``steam electric plants''. 
Similarly, combined cycle turbines are also considered ``steam 
electric plants'' because such facilities incorporate heat recovery 
steam generators. Simple cycle turbines, in contrast, are not 
``steam electric plants'' because these turbines typically do not 
generate steam.

    Example: A stationary source includes a steam electric plant 
with three 100 million BTU/hr boilers. Because the aggregate 
capacity exceeds 250 million BTU/hr for the ``plant,'' these boilers 
would be identified in Step 2.

    (2) ``Fossil-fuel boilers of more than 250 million BTU/hr heat 
input.'' We interpret this category title to cover only those 
boilers that are individually greater than 250 million BTU/hr. 
However, an individual boiler smaller than 250 million BTU/hr should 
be subject to BART if it is an integral part of a process 
description at a plant that is in a different BART category--for 
example, a boiler at a Kraft pulp mill that, in addition to 
providing steam or mechanical power, uses the waste liquor from the 
process as a fuel. In general, if the process uses any by-product of 
the boiler and the boiler's function is to serve the process, then 
the boiler is integral to the process and should be considered to be 
part of the process description.
    Also, you should consider a multi-fuel boiler to be a ``fossil-
fuel boiler'' if it burns any amount of fossil fuel. You may take 
federally and State enforceable operational limits into account in 
determining whether a multi-fuel boiler's fossil fuel capacity 
exceeds 250 million Btu/hr.
    (3) ``Petroleum storage and transfer facilities with a capacity 
exceeding 300,000 barrels.'' The 300,000 barrel cutoff refers to 
total facility-wide tank capacity for tanks that were put in place 
within the 1962-1977 time period, and includes gasoline and other 
petroleum-derived liquids.
    (4) ``Phosphate rock processing plants.'' This category 
descriptor is broad, and includes all types of phosphate rock 
processing facilities, including elemental phosphorous plants as 
well as fertilizer production plants.
    (5) ``Charcoal production facilities.'' We interpret this 
category to include charcoal briquet manufacturing and activated 
carbon production.
    (6) ``Chemical process plants.'' and pharmaceutical 
manufacturing. Consistent with past policy, we interpret the 
category ``chemical process plants'' to include those facilities 
within the 2-digit Standard Industrial Classification (SIC) code 28. 
Accordingly, we interpret the term ``chemical process plants'' to 
include pharmaceutical manufacturing facilities.
    (7) ``Secondary metal production.'' We interpret this category 
to include nonferrous metal facilities included within SIC code 
3341, and secondary ferrous metal facilities that we also consider 
to be included within the category ``iron and steel mill plants.''
    (8) ``Primary aluminum ore reduction.'' We interpret this 
category to include those facilities covered by 40 CFR 60.190, the 
new source performance standard (NSPS) for primary aluminum ore 
reduction plants. This definition is also consistent with the 
definition at 40 CFR 63.840.

2. Step 2: Identify the Start-Up Dates of the Emission Units

    1. Emissions units listed under Step 1 are BART-eligible only if 
they were ``in existence'' on August 7, 1977 but were not ``in 
operation'' before August 7, 1962.

What does ``in existence on August 7, 1977'' mean?

    2. The regional haze rule defines ``in existence'' to mean that:
    ``the owner or operator has obtained all necessary 
preconstruction approvals or permits required by Federal, State, or 
local air pollution emissions and air quality laws or regulations 
and either has (1) begun, or caused to begin, a continuous program 
of physical on-site construction of the facility or (2) entered into 
binding agreements or contractual obligations, which cannot be 
canceled or modified without substantial loss to the owner or 
operator, to undertake a program of construction of the facility to 
be completed in a reasonable time.'' 40 CFR 51.301.
    As this definition is essentially identical to the definition of 
``commence construction'' as that term is used in the PSD 
regulations, the two terms mean the same thing. See 40 CFR 
51.165(a)(1)(xvi) and 40 CFR 52.21(b)(9). Under this definition, an 
emissions unit could be ``in existence'' even if it did not begin 
operating until several years after 1977.

    Example: The owner of a source obtained all necessary permits in 
early 1977 and entered into binding construction agreements in June 
1977. Actual on-site construction began in late 1978, and 
construction was completed in mid-1979. The source began operating 
in September 1979. The emissions unit was ``in existence'' as of 
August 7, 1977.

    Major stationary sources which commenced construction AFTER 
August 7, 1977 (i.e., major stationary sources which were not ``in 
existence'' on August 7, 1977) were subject to new source review 
(NSR) under the PSD program. Thus, the August 7, 1977 ``in 
existence'' test is essentially the same thing as the identification 
of emissions units that were grandfathered from the NSR review 
requirements of the 1977 CAA amendments.
    3. Sources are not BART-eligible if the only change at the plant 
during the relevant time period was the addition of pollution 
controls. For example, if the only change at a copper smelter during 
the 1962 through 1977 time period was the addition of acid plants 
for the reduction of SO2 emissions, these emission 
controls would not by themselves trigger a BART review.

What does ``in operation before August 7, 1962'' mean?

    An emissions unit that meets the August 7, 1977 ``in existence'' 
test is not BART-eligible if it was in operation before August 7, 
1962. ``In operation'' is defined as ``engaged in activity related 
to the primary design function of the source.'' This means that a 
source must have begun actual operations by August 7, 1962 to 
satisfy this test.

    Example: The owner or operator entered into binding agreements 
in 1960. Actual on-site construction began in 1961, and construction 
was complete in mid-1962. The source began operating in September 
1962. The emissions unit was not ``in operation'' before August 7, 
1962 and is therefore subject to BART.

What is a ``reconstructed source?'

    1. Under a number of CAA programs, an existing source which is 
completely or

[[Page 39160]]

substantially rebuilt is treated as a new source. Such 
``reconstructed'' sources are treated as new sources as of the time 
of the reconstruction. Consistent with this overall approach to 
reconstructions, the definition of BART-eligible facility (reflected 
in detail in the definition of ``existing stationary facility'') 
includes consideration of sources that were in operation before 
August 7, 1962, but were reconstructed during the August 7, 1962 to 
August 7, 1977 time period.
    2. Under the regional haze regulations at 40 CFR 51.301, a 
reconstruction has taken place if ``the fixed capital cost of the 
new component exceeds 50 percent of the fixed capital cost of a 
comparable entirely new source.'' The rule also states that ``[a]ny 
final decision as to whether reconstruction has occurred must be 
made in accordance with the provisions of Sec. Sec.  60.15 (f)(1) 
through (3) of this title.'' ``[T]he provisions of Sec. Sec.  
60.15(f)(1) through (3)'' refers to the general provisions for New 
Source Performance Standards (NSPS). Thus, the same policies and 
procedures for identifying reconstructed ``affected facilities'' 
under the NSPS program must also be used to identify reconstructed 
``stationary sources'' for purposes of the BART requirement.
    3. You should identify reconstructions on an emissions unit 
basis, rather than on a plantwide basis. That is, you need to 
identify only the reconstructed emission units meeting the 50 
percent cost criterion. You should include reconstructed emission 
units in the list of emission units you identified in Step 1. You 
need consider as possible reconstructions only those emissions units 
with the potential to emit more than 250 tons per year of any 
visibility-impairing pollutant.
    4. The ``in operation'' and ``in existence'' tests apply to 
reconstructed sources. If an emissions unit was reconstructed and 
began actual operation before August 7, 1962, it is not BART-
eligible. Similarly, any emissions unit for which a reconstruction 
``commenced'' after August 7, 1977, is not BART-eligible.

How are modifications treated under the BART provision?

    1. The NSPS program and the major source NSR program both 
contain the concept of modifications. In general, the term 
``modification'' refers to any physical change or change in the 
method of operation of an emissions unit that results in an increase 
in emissions.
    2. The BART provision in the regional haze rule contains no 
explicit treatment of modifications or how modified emissions units, 
previously subject to the requirement to install best available 
control technology (BACT), lowest achievable emission rate (LAER) 
controls, and/or NSPS are treated under the rule. As the BART 
requirements in the CAA do not appear to provide any exemption for 
sources which have been modified since 1977, the best interpretation 
of the CAA visibility provisions is that a subsequent modification 
does not change a unit's construction date for the purpose of BART 
applicability. Accordingly, if an emissions unit began operation 
before 1962, it is not BART-eligible if it was modified between 1962 
and 1977, so long as the modification is not also a 
``reconstruction.'' On the other hand, an emissions unit which began 
operation within the 1962-1977 time window, but was modified after 
August 7, 1977, is BART-eligible. We note, however, that if such a 
modification was a major modification that resulted in the 
installation of controls, the State will take this into account 
during the review process and may find that the level of controls 
already in place are consistent with BART.

3. Step 3: Compare the Potential Emissions to the 250 Ton/Yr Cutoff

    The result of Steps 1 and 2 will be a list of emissions units at 
a given plant site, including reconstructed emissions units, that 
are within one or more of the BART categories and that were placed 
into operation within the 1962-1977 time window. The third step is 
to determine whether the total emissions represent a current 
potential to emit that is greater than 250 tons per year of any 
single visibility impairing pollutant. Fugitive emissions, to the 
extent quantifiable, must be counted. In most cases, you will add 
the potential emissions from all emission units on the list 
resulting from Steps 1 and 2. In a few cases, you may need to 
determine whether the plant contains more than one ``stationary 
source'' as the regional haze rule defines that term, and as we 
explain further below.

What pollutants should I address?

    Visibility-impairing pollutants include the following:
    (1) Sulfur dioxide (SO2),
    (2) Nitrogen oxides (NOX), and
    (3) Particulate matter.
    You may use PM10 as an indicator for particulate 
matter in this intial step. [Note that we do not recommend use of 
total suspended particulates (TSP) as in indicator for particulate 
matter.] As emissions of PM10 include the components of 
PM2.5 as a subset, there is no need to have separate 250 
ton thresholds for PM10 and PM2.5; 250 tons of 
PM10 represents at most 250 tons of PM2.5, and 
at most 250 tons of any individual particulate species such as 
elemental carbon, crustal material, etc.
    However, if you determine that a source of particulate matter is 
BART-eligible, it will be important to distinguish between the fine 
and coarse particle components of direct particulate emissions in 
the remainder of the BART analysis, including for the purpose of 
modeling the source's impact on visibility. This is because although 
both fine and coarse particulate matter contribute to visibility 
impairment, the long-range transport of fine particles is of 
particular concern in the formation of regional haze. Thus, for 
example, air quality modeling results used in the BART determination 
will provide a more accurate prediction of a source's impact on 
visibility if the inputs into the model account for the relative 
particle size of any directly emitted particulate matter (i.e. 
PM10 vs. PM2.5).
    You should exercise judgment in deciding whether the following 
pollutants impair visibility in an area:
    (4) Volatile organic compounds (VOC), and
    (5) Ammonia and ammonia compounds.
    You should use your best judgment in deciding whether VOC or 
ammonia emissions from a source are likely to have an impact on 
visibility in an area. Certain types of VOC emissions, for example, 
are more likely to form secondary organic aerosols than others.\1\ 
Similarly, controlling ammonia emissions in some areas may not have 
a significant impact on visibility. You need not provide a formal 
showing of an individual decision that a source of VOC or ammonia 
emissions is not subject to BART review. Because air quality 
modeling may not be feasible for individual sources of VOC or 
ammonia, you should also exercise your judgement in assessing the 
degree of visibility impacts due to emissions of VOC and emissions 
of ammonia or ammonia compounds. You should fully document the basis 
for judging that a VOC or ammonia source merits BART review, 
including your assessment of the source's contribution to visibility 
impairment.
---------------------------------------------------------------------------

    \1\ Fine particles: Overview of Atmospheric Chemistry, Sources 
of Emissions, and Ambient Monitoring Data, Memorandum to Docket OAR 
2002-006, April 1, 2005.
---------------------------------------------------------------------------

What does the term ``potential'' emissions mean?

    The regional haze rule defines potential to emit as follows:

    ``Potential to emit'' means the maximum capacity of a stationary 
source to emit a pollutant under its physical and operational 
design. Any physical or operational limitation on the capacity of 
the source to emit a pollutant including air pollution control 
equipment and restrictions on hours of operation or on the type or 
amount of material combusted, stored, or processed, shall be treated 
as part of its design if the limitation or the effect it would have 
on emissions is federally enforceable. Secondary emissions do not 
count in determining the potential to emit of a stationary source.

The definition of ``potential to emit'' means that a source which 
actually emits less than 250 tons per year of a visibility-impairing 
pollutant is BART-eligible if its emissions would exceed 250 tons 
per year when operating at its maximum capacity given its physical 
and operational design (and considering all federally enforceable 
and State enforceable permit limits.)

    Example: A source, while operating at one-fourth of its 
capacity, emits 75 tons per year of SO2. If it were 
operating at 100 percent of its maximum capacity, the source would 
emit 300 tons per year. Because under the above definition such a 
source would have ``potential'' emissions that exceed 250 tons per 
year, the source (if in a listed category and built during the 1962-
1977 time window) would be BART-eligible.

How do I identify whether a plant has more than one ``stationary 
source?''

    1. The regional haze rule, in 40 CFR 51.301, defines a 
stationary source as a ``building, structure, facility or 
installation which emits or may emit any air pollutant.'' \2\

[[Page 39161]]

The rule further defines ``building, structure or facility'' as:
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    \2\ Note: Most of these terms and definitions are the same for 
regional haze and the 1980 visibility regulations. For the regional 
haze rule we use the term ``BART-eligible source'' rather than 
``existing stationary facility'' to clarify that only a limited 
subset of existing stationary sources are subject to BART.

all of the pollutant-emitting activities which belong to the same 
industrial grouping, are located on one or more contiguous or 
adjacent properties, and are under the control of the same person 
(or persons under common control). Pollutant-emitting activities 
must be considered as part of the same industrial grouping if they 
belong to the same Major Group (i.e., which have the same two-digit 
code) as described in the Standard Industrial Classification Manual, 
1972 as amended by the 1977 Supplement (U.S. Government Printing 
---------------------------------------------------------------------------
Office stock numbers 4101-0066 and 003-005-00176-0, respectively).

    2. In applying this definition, it is necessary to determine 
which facilities are located on ``contiguous or adjacent 
properties.'' Within this contiguous and adjacent area, it is also 
necessary to group those emission units that are under ``common 
control.'' We note that these plant boundary issues and ``common 
control'' issues are very similar to those already addressed in 
implementation of the title V operating permits program and in NSR.
    3. For emission units within the ``contiguous or adjacent'' 
boundary and under common control, you must group emission units 
that are within the same industrial grouping (that is, associated 
with the same 2-digit SIC code) in order to define the stationary 
source.\3\ For most plants on the BART source category list, there 
will only be one 2-digit SIC that applies to the entire plant. For 
example, all emission units associated with kraft pulp mills are 
within SIC code 26, and chemical process plants will generally 
include emission units that are all within SIC code 28. The ``2-
digit SIC test'' applies in the same way as the test is applied in 
the major source NSR programs.\4\
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    \3\ We recognize that we are in a transition period from the use 
of the SIC system to a new system called the North American Industry 
Classification System (NAICS). For purposes of identifying BART-
eligible sources, you may use either 2-digit SICS or the equivalent 
in the NAICS system.
    \4\ Note: The concept of support facility used for the NSR 
program applies here as well. Support facilities, that is facilities 
that convey, store or otherwise assist in the production of the 
principal product, must be grouped with primary facilities even when 
the facilities fall wihin separate SIC codes. For purposes of BART 
reviews, however, such support facilities (a) must be within one of 
the 26 listed source categories and (b) must have been in existence 
as of August 7, 1977, and (c) must not have been in operation as of 
August 7, 1962.
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    4. For purposes of the regional haze rule, you must group 
emissions from all emission units put in place within the 1962-1977 
time period that are within the 2-digit SIC code, even if those 
emission units are in different categories on the BART category 
list.

    Examples: A chemical plant which started operations within the 
1962 to 1977 time period manufactures hydrochloric acid (within the 
category title ``Hydrochloric, sulfuric, and nitric acid plants'') 
and various organic chemicals (within the category title ``chemical 
process plants''). All of the emission units are within SIC code 28 
and, therefore, all the emission units are considered in determining 
BART eligibility of the plant. You sum the emissions over all of 
these emission units to see whether there are more than 250 tons per 
year of potential emissions.
    A steel mill which started operations within the 1962 to 1977 
time period includes a sintering plant, a coke oven battery, and 
various other emission units. All of the emission units are within 
SIC code 33. You sum the emissions over all of these emission units 
to see whether there are more than 250 tons per year of potential 
emissions.

4. Final Step: Identify the Emissions Units and Pollutants That 
Constitute the BART-Eligible Source

    If the emissions from the list of emissions units at a 
stationary source exceed a potential to emit of 250 tons per year 
for any visibility-impairing pollutant, then that collection of 
emissions units is a BART-eligible source.

    Example: A stationary source comprises the following two 
emissions units, with the following potential emissions:
Emissions unit A
    200 tons/yr SO2
    150 tons/yr NOX
    25 tons/yr PM
Emissions unit B
    100 tons/yr SO2
    75 tons/yr NOX
    10 tons/yr PM

For this example, potential emissions of SO2 are 300 
tons/yr, which exceeds the 250 tons/yr threshold. Accordingly, the 
entire ``stationary source'', that is, emissions units A and B, may 
be subject to a BART review for SO2, NOX, and 
PM, even though the potential emissions of PM and NOX at 
each emissions unit are less than 250 tons/yr each.
    Example: The total potential emissions, obtained by adding the 
potential emissions of all emission units in a listed category at a 
plant site, are as follows:

200 tons/yr SO2
150 tons/yr NOX
25 tons/yr PM

    Even though total emissions exceed 250 tons/yr, no individual 
regulated pollutant exceeds 250 tons/yr and this source is not BART-
eligible.

Can States establish de minimis levels of emissions for pollutants at 
BART-eligible sources?

    In order to simplify BART determinations, States may choose to 
identify de minimis levels of pollutants at BART-eligible sources 
(but are not required to do so). De minimis values should be 
identified with the purpose of excluding only those emissions so 
minimal that they are unlikely to contribute to regional haze. Any 
de minimis values that you adopt must not be higher than the PSD 
applicability levels: 40 tons/yr for SO2 and 
NOX and 15 tons/yr for PM10. These de minimis 
levels may only be applied on a plant-wide basis.

III. How to Identify Sources ``Subject to BART''

    Once you have compiled your list of BART-eligible sources, you 
need to determine whether (1) to make BART determinations for all of 
them or (2) to consider exempting some of them from BART because 
they may not reasonably be anticipated to cause or contribute to any 
visibility impairment in a Class I area. If you decide to make BART 
determinations for all the BART-eligible sources on your list, you 
should work with your regional planning organization (RPO) to show 
that, collectively, they cause or contribute to visibility 
impairment in at least one Class I area. You should then make 
individual BART determinations by applying the five statutory 
factors discussed in Section IV below.
    On the other hand, you also may choose to perform an initial 
examination to determine whether a particular BART-eligible source 
or group of sources causes or contributes to visibility impairment 
in nearby Class I areas. If your analysis, or information submitted 
by the source, shows that an individual source or group of sources 
(or certain pollutants from those sources) is not reasonably 
anticipated to cause or contribute to any visibility impairment in a 
Class I area, then you do not need to make BART determinations for 
that source or group of sources (or for certain pollutants from 
those sources). In such a case, the source is not ``subject to 
BART'' and you do not need to apply the five statutory factors to 
make a BART determination. This section of the Guideline discusses 
several approaches that you can use to exempt sources from the BART 
determination process.

A. What Steps Do I Follow To Determine Whether a Source or Group of 
Sources Cause or Contribute to Visibility Impairment for Purposes 
of BART?

1. How Do I Establish a Threshold?

    One of the first steps in determining whether sources cause or 
contribute to visibility impairment for purposes of BART is to 
establish a threshold (measured in deciviews) against which to 
measure the visibility impact of one or more sources. A single 
source that is responsible for a 1.0 deciview change or more should 
be considered to ``cause'' visibility impairment; a source that 
causes less than a 1.0 deciview change may still contribute to 
visibility impairment and thus be subject to BART.
    Because of varying circumstances affecting different Class I 
areas, the appropriate threshold for determining whether a source 
``contributes to any visibility impairment'' for the purposes of 
BART may reasonably differ across States. As a general matter, any 
threshold that you use for determining whether a source 
``contributes'' to visibility impairment should not be higher than 
0.5 deciviews.
    In setting a threshold for ``contribution,'' you should consider 
the number of emissions sources affecting the Class I areas at issue 
and the magnitude of the individual sources' impacts.\5\ In general, 
a larger number of sources causing impacts in a Class I area may 
warrant a lower contribution threshold. States remain free to use a 
threshold lower than 0.5 deciviews if they conclude that the

[[Page 39162]]

location of a large number of BART-eligible sources within the State 
and in proximity to a Class I area justify this approach.\6\
---------------------------------------------------------------------------

    \5\ We expect that regional planning organizations will have 
modeling information that identifies sources affecting visibility in 
individual class I areas.
    \6\ Note that the contribution threshold should be used to 
determine whether an individual source is reasonably anticipated to 
contribute to visibility impairment. You should not aggregate the 
visibility effects of multiple sources and compare their collective 
effects against your contribution threshold because this would 
inappropriately create a ``contribute to contribution'' test.
---------------------------------------------------------------------------

2. What Pollutants Do I Need to Consider?

    You must look at SO2, NOX, and direct 
particulate matter (PM) emissions in determining whether sources 
cause or contribute to visibility impairment, including both 
PM10 and PM2.5. Consistent with the approach 
for identifying your BART-eligible sources, you do not need to 
consider less than de minimis emissions of these pollutants from a 
source.
    As explained in section II, you must use your best judgement to 
determine whether VOC or ammonia emissions are likely to have an 
impact on visibility in an area. In addition, although as explained 
in Section II, you may use PM10 an indicator for 
particulate matter in determining whether a source is BART-eligible, 
in determining whether a source contributes to visibility 
impairment, you should distinguish between the fine and coarse 
particle components of direct particulate emissions. Although both 
fine and coarse particulate matter contribute to visibility 
impairment, the long-range transport of fine particles is of 
particular concern in the formation of regional haze. Air quality 
modeling results used in the BART determination will provide a more 
accurate prediction of a source's impact on visibility if the inputs 
into the model account for the relative particle size of any 
directly emitted particulate matter (i.e. PM10 vs. 
PM2.5).

3. What Kind of Modeling Should I Use To Determine Which Sources and 
Pollutants Need Not Be Subject to BART?

    This section presents several options for determining that 
certain sources need not be subject to BART. These options rely on 
different modeling and/or emissions analysis approaches. They are 
provided for your guidance. You may also use other reasonable 
approaches for analyzing the visibility impacts of an individual 
source or group of sources.

Option 1: Individual Source Attribution Approach (Dispersion 
Modeling)

    You can use dispersion modeling to determine that an individual 
source cannot reasonably be anticipated to cause or contribute to 
visibility impairment in a Class I area and thus is not subject to 
BART. Under this option, you can analyze an individual source's 
impact on visibility as a result of its emissions of SO2, 
NOX and direct PM emissions. Dispersion modeling cannot 
currently be used to estimate the predicted impacts on visibility 
from an individual source's emissions of VOC or ammonia. You may use 
a more qualitative assessment to determine on a case-by-case basis 
which sources of VOC or ammonia emissions may be likely to impair 
visibility and should therefore be subject to BART review, as 
explained in section II.A.3. above.
    You can use CALPUFF \7\ or other appropriate model to predict 
the visibility impacts from a single source at a Class I area. 
CALPUFF is the best regulatory modeling application currently 
available for predicting a single source's contribution to 
visibility impairment and is currently the only EPA-approved model 
for use in estimating single source pollutant concentrations 
resulting from the long range transport of primary pollutants.\8\ It 
can also be used for some other purposes, such as the visibility 
assessments addressed in today's rule, to account for the chemical 
transformation of SO2 and NOX.
---------------------------------------------------------------------------

    \7\ The model code and its documentation are available at no 
cost for download from http://www.epa.gov/scram001/tt22.htm#calpuff.
    \8\ The Guideline on Air Quality Models, 40 CFR part 51, 
appendix W, addresses the regulatory application of air quality 
models for assessing criteria pollutants under the CAA, and 
describes further the procedures for using the CALPUFF model, as 
well as for obtaining approval for the use of other, nonguideline 
models.
---------------------------------------------------------------------------

    There are several steps for making an individual source 
attribution using a dispersion model:
    1. Develop a modeling protocol. Some critical items to include 
in the protocol are the meteorological and terrain data that will be 
used, as well as the source-specific information (stack height, 
temperature, exit velocity, elevation, and emission rates of 
applicable pollutants) and receptor data from appropriate Class I 
areas. We recommend following EPA's Interagency Workgroup on Air 
Quality Modeling (IWAQM) Phase 2 Summary Report and Recommendations 
for Modeling Long Range Transport Impacts \9\ for parameter settings 
and meteorological data inputs. You may use other settings from 
those in IWAQM, but you should identify these settings and explain 
your selection of these settings.
---------------------------------------------------------------------------

    \9\ Interagency Workgroup on Air Quality Modeling (IWAQM) Phase 
2 Summary Report and Recommendations for Modeling Long Range 
Transport Impacts, U.S. Environmental Protection Agency, EPA-454/R-
98-019, December 1998.
---------------------------------------------------------------------------

    One important element of the protocol is in establishing the 
receptors that will be used in the model. The receptors that you use 
should be located in the nearest Class I area with sufficient 
density to identify the likely visibility effects of the source. For 
other Class I areas in relatively close proximity to a BART-eligible 
source, you may model a few strategic receptors to determine whether 
effects at those areas may be greater than at the nearest Class I 
area. For example, you might chose to locate receptors at these 
areas at the closest point to the source, at the highest and lowest 
elevation in the Class I area, at the IMPROVE monitor, and at the 
approximate expected plume release height. If the highest modeled 
effects are observed at the nearest Class I area, you may choose not 
to analyze the other Class I areas any further as additional 
analyses might be unwarranted.
    You should bear in mind that some receptors within the relevant 
Class I area may be less than 50 km from the source while other 
receptors within that same Class I area may be greater than 50 km 
from the same source. As indicated by the Guideline on Air Quality 
Models, 40 CFR part 51, appendix W, this situation may call for the 
use of two different modeling approaches for the same Class I area 
and source, depending upon the State's chosen method for modeling 
sources less than 50 km. In situations where you are assessing 
visibility impacts for source-receptor distances less than 50 km, 
you should use expert modeling judgment in determining visibility 
impacts, giving consideration to both CALPUFF and other appropriate 
methods.
    In developing your modeling protocol, you may want to consult 
with EPA and your regional planning organization (RPO). Up-front 
consultation will ensure that key technical issues are addressed 
before you conduct your modeling.
    2. With the accepted protocol and compare the predicted 
visibility impacts with your threshold for ``contribution.'' You 
should calculate daily visibility values for each receptor as the 
change in deciviews compared against natural visibility conditions. 
You can use EPA's ``Guidance for Estimating Natural Visibility 
Conditions Under the Regional Haze Rule,'' EPA-454/B-03-005 
(September 2003) in making this calculation. To determine whether a 
source may reasonably be anticipated to cause or contribute to 
visibility impairment at Class I area, you then compare the impacts 
predicted by the model against the threshold that you have selected.
    The emissions estimates used in the models are intended to 
reflect steady-state operating conditions during periods of high 
capacity utilization. We do not generally recommend that emissions 
reflecting periods of start-up, shutdown, and malfunction be used, 
as such emission rates could produce higher than normal effects than 
would be typical of most facilities. We recommend that States use 
the 24 hour average actual emission rate from the highest emitting 
day of the meteorological period modeled, unless this rate reflects 
periods start-up, shutdown, or malfunction. In addition, the monthly 
average relative humidity is used, rather than the daily average 
humidity--an approach that effectively lowers the peak values in 
daily model averages.
    For these reasons, if you use the modeling approach we 
recommend, you should compare your ``contribution'' threshold 
against the 98th percentile of values. If the 98th percentile value 
from your modeling is less than your contribution threshold, then 
you may conclude that the source does not contribute to visibility 
impairment and is not subject to BART.

Option 2: Use of Model Plants To Exempt Individual Sources With 
Common Characteristics

    Under this option, analyses of model plants could be used to 
exempt certain BART-eligible sources that share specific 
characteristics. It may be most useful to use this type of analysis 
to identify the types of small sources that do not cause or 
contribute to visibility impairment for purposes of BART, and thus 
should not be subject to a BART review. Different Class I areas may 
have different characteristics, however, so

[[Page 39163]]

you should use care to ensure that the criteria you develop are 
appropriate for the applicable cases.
    In carrying out this approach, you could use modeling analyses 
of representative plants to reflect groupings of specific sources 
with important common characteristics. Based on these analyses, you 
may find that certain types of sources are clearly anticipated to 
cause or contribute to visibility impairment. You could then choose 
to categorically require those types of sources to undergo a BART 
determination. Conversely, you may find based on representative 
plant analyses that certain types of sources are not reasonably 
anticipated to cause or contribute to visibility impairment. To do 
this, you may conduct your own modeling to establish emission levels 
and distances from Class I areas on which you can rely to exempt 
sources with those characteristics. For example, based on your 
modeling you might choose to exempt all NOX-only sources 
that emit less than a certain amount per year and are located a 
certain distance from a Class I area. You could then choose to 
categorically exempt such sources from the BART determination 
process.
    Our analyses of visibility impacts from model plants provide a 
useful example of the type of analyses that can be used to exempt 
categories of sources from BART.\10\ In our analyses, we developed 
model plants (EGUs and non-EGUs), with representative plume and 
stack characteristics, for use in considering the visibility impact 
from emission sources of different sizes and compositions at 
distances of 50, 100 and 200 kilometers from two hypothetical Class 
I areas (one in the East and one in the West). As the plume and 
stack characteristics of these model plants were developed 
considering the broad range of sources within the EGU and non-EGU 
categories, they do not necessarily represent any specific plant. 
However, the results of these analyses are instructive in the 
development of an exemption process for any Class I area.
---------------------------------------------------------------------------

    \10\ CALPUFF Analysis in Support of the June 2005 Changes to the 
Regional Haze Rule, U.S. Environmental Protection Agency, June 15, 
2005, Docket No. OAR-2002-0076.
---------------------------------------------------------------------------

    In preparing our analyses, we have made a number of assumptions 
and exercised certain modeling choices; some of these have a 
tendency to lend conservatism to the results, overstating the likely 
effects, while others may understate the likely effects. On balance, 
when all of these factors are considered, we believe that our 
examples reflect realistic treatments of the situations being 
modeled. Based on our analyses, we believe that a State that has 
established 0.5 deciviews as a contribution threshold could 
reasonably exempt from the BART review process sources that emit 
less than 500 tons per year of NOX or SO2 (or 
combined NOX and SO2), as long as these 
sources are located more than 50 kilometers from any Class I area; 
and sources that emit less than 1000 tons per year of NOX 
or SO2 (or combined NOX and SO2) 
that are located more than 100 kilometers from any Class I area. You 
do, however, have the option of showing other thresholds might also 
be appropriate given your specific circumstances.

Option 3: Cumulative Modeling To Show That No Sources in a State 
Are Subject to BART

    You may also submit to EPA a demonstration based on an analysis 
of overall visibility impacts that emissions from BART-eligible 
sources in your State, considered together, are not reasonably 
anticipated to cause or contribute to any visibility impairment in a 
Class I area, and thus no source should be subject to BART. You may 
do this on a pollutant by pollutant basis or for all visibility-
impairing pollutants to determine if emissions from these sources 
contribute to visibility impairment.
    For example, emissions of SO2 from your BART-eligible 
sources may clearly cause or contribute to visibility impairment 
while direct emissions of PM2.5 from these sources may 
not contribute to impairment. If you can make such a demonstration, 
then you may reasonably conclude that none of your BART-eligible 
sources are subject to BART for a particular pollutant or 
pollutants. As noted above, your demonstration should take into 
account the interactions among pollutants and their resulting 
impacts on visibility before making any pollutant-specific 
determinations.
    Analyses may be conducted using several alternative modeling 
approaches. First, you may use the CALPUFF or other appropriate 
model as described in Option 1 to evaluate the impacts of individual 
sources on downwind Class I areas, aggregating those impacts to 
determine the collective contribution of all BART-eligible sources 
to visibility impairment. You may also use a photochemical grid 
model. As a general matter, the larger the number of sources being 
modeled, the more appropriate it may be to use a photochemical grid 
model. However, because such models are significantly less sensitive 
than dispersion models to the contributions of one or a few sources, 
as well as to the interactions among sources that are widely 
distributed geographically, if you wish to use a grid model, you 
should consult with the appropriate EPA Regional Office to develop 
an appropriate modeling protocol.

IV. The BART Determination: Analysis of BART Options

    This section describes the process for the analysis of control 
options for sources subject to BART.

A. What factors must I address in the BART review?

    The visibility regulations define BART as follows:
    Best Available Retrofit Technology (BART) means an emission 
limitation based on the degree of reduction achievable through the 
application of the best system of continuous emission reduction for 
each pollutant which is emitted by . . . [a BART-eligible source]. 
The emission limitation must be established, on a case-by-case 
basis, taking into consideration the technology available, the costs 
of compliance, the energy and non-air quality environmental impacts 
of compliance, any pollution control equipment in use or in 
existence at the source, the remaining useful life of the source, 
and the degree of improvement in visibility which may reasonably be 
anticipated to result from the use of such technology.
    The BART analysis identifies the best system of continuous 
emission reduction taking into account:
    (1) The available retrofit control options,
    (2) Any pollution control equipment in use at the source (which 
affects the availability of options and their impacts),
    (3) The costs of compliance with control options,
    (4) The remaining useful life of the facility,
    (5) The energy and non-air quality environmental impacts of 
control options
    (6) The visibility impacts analysis.

B. What is the scope of the BART review?

    Once you determine that a source is subject to BART for a 
particular pollutant, then for each affected emission unit, you must 
establish BART for that pollutant. The BART determination must 
address air pollution control measures for each emissions unit or 
pollutant emitting activity subject to review.

    Example: Plantwide emissions from emission units within the 
listed categories that began operation within the ``time window'' 
for BART \11\ are 300 tons/yr of NOX, 200 tons/yr of 
SO2, and 150 tons/yr of primary particulate. Emissions 
unit A emits 200 tons/yr of NOX, 100 tons/yr of 
SO2, and 100 tons/yr of primary particulate. Other 
emission units, units B through H, which began operating in 1966, 
contribute lesser amounts of each pollutant. For this example, a 
BART review is required for NOX, SO2, and 
primary particulate, and control options must be analyzed for units 
B through H as well as unit A.
---------------------------------------------------------------------------

    \11\ That is, emission units that were in existence on August 7, 
1977 and which began actual operation on or after August 7, 1962.
---------------------------------------------------------------------------

C. How does a BART review relate to Maximum Achievable Control 
Technology (MACT) Standards under CAA section 112, or to other 
emission limitations required under the CAA?

    For VOC and PM sources subject to MACT standards, States may 
streamline the analysis by including a discussion of the MACT 
controls and whether any major new technologies have been developed 
subsequent to the MACT standards. We believe that there are many VOC 
and PM sources that are well controlled because they are regulated 
by the MACT standards, which EPA developed under CAA section 112. 
For a few MACT standards, this may also be true for SO2. 
Any source subject to MACT standards must meet a level that is as 
stringent as the best-controlled 12 percent of sources in the 
industry. Examples of these hazardous air pollutant sources which 
effectively control VOC and PM emissions include (among others) 
secondary lead facilities, organic chemical plants subject to the 
hazardous organic NESHAP (HON), pharmaceutical production 
facilities, and equipment leaks and wastewater operations at 
petroleum refineries. We believe that, in many cases, it will be 
unlikely that States will identify emission controls more stringent 
than the MACT standards without

[[Page 39164]]

identifying control options that would cost many thousands of 
dollars per ton. Unless there are new technologies subsequent to the 
MACT standards which would lead to cost-effective increases in the 
level of control, you may rely on the MACT standards for purposes of 
BART.
    We believe that the same rationale also holds true for emissions 
standards developed for municipal waste incinerators under CAA 
section 111(d), and for many NSR/PSD determinations and NSR/PSD 
settlement agreements. However, we do not believe that technology 
determinations from the 1970s or early 1980s, including new source 
performance standards (NSPS), should be considered to represent best 
control for existing sources, as best control levels for recent 
plant retrofits are more stringent than these older levels.
    Where you are relying on these standards to represent a BART 
level of control, you should provide the public with a discussion of 
whether any new technologies have subsequently become available.

D. What Are the Five Basic Steps of a Case-by-Case BART Analysis?

    The five steps are:
    STEP 1--Identify All \12\ Available Retrofit Control 
Technologies,
---------------------------------------------------------------------------

    \12\ In identifying ``all'' options, you must identify the most 
stringent option and a reasonable set of options for analysis that 
reflects a comprehensive list of available technologies. It is not 
necessary to list all permutations of available control levels that 
exist for a given technology--the list is complete if it includes 
the maximum level of control each technology is capable of 
achieving.
---------------------------------------------------------------------------

    STEP 2-- Eliminate Technically Infeasible Options,
    STEP 3-- Evaluate Control Effectiveness of Remaining Control 
Technologies,
    STEP 4-- Evaluate Impacts and Document the Results, and
    STEP 5--Evaluate Visibility Impacts.

1. STEP 1: How do I identify all available retrofit emission control 
techniques?

    1. Available retrofit control options are those air pollution 
control technologies with a practical potential for application to 
the emissions unit and the regulated pollutant under evaluation. Air 
pollution control technologies can include a wide variety of 
available methods, systems, and techniques for control of the 
affected pollutant. Technologies required as BACT or LAER are 
available for BART purposes and must be included as control 
alternatives. The control alternatives can include not only existing 
controls for the source category in question but also take into 
account technology transfer of controls that have been applied to 
similar source categories and gas streams. Technologies which have 
not yet been applied to (or permitted for) full scale operations 
need not be considered as available; we do not expect the source 
owner to purchase or construct a process or control device that has 
not already been demonstrated in practice.
    2. Where a NSPS exists for a source category (which is the case 
for most of the categories affected by BART), you should include a 
level of control equivalent to the NSPS as one of the control 
options.\13\ The NSPS standards are codified in 40 CFR part 60. We 
note that there are situations where NSPS standards do not require 
the most stringent level of available control for all sources within 
a category. For example, post-combustion NOX controls 
(the most stringent controls for stationary gas turbines) are not 
required under subpart GG of the NSPS for Stationary Gas Turbines. 
However, such controls must still be considered available 
technologies for the BART selection process.
---------------------------------------------------------------------------

    \13\ In EPA's 1980 BART guidelines for reasonably attributable 
visibility impairment, we concluded that NSPS standards generally, 
at that time, represented the best level sources could install as 
BART. In the 20 year period since this guidance was developed, there 
have been advances in SO2 control technologies as well as 
technologies for the control of other pollutants, confirmed by a 
number of recent retrofits at Western power plants. Accordingly, EPA 
no longer concludes that the NSPS level of controls automatically 
represents ``the best these sources can install.'' Analysis of the 
BART factors could result in the selection of a NSPS level of 
control, but you should reach this conclusion only after considering 
the full range of control options.
---------------------------------------------------------------------------

    3. Potentially applicable retrofit control alternatives can be 
categorized in three ways.
     Pollution prevention: use of inherently lower-emitting 
processes/practices, including the use of control techniques (e.g. 
low-NOX burners) and work practices that prevent 
emissions and result in lower ``production-specific'' emissions 
(note that it is not our intent to direct States to switch fuel 
forms, e.g. from coal to gas),
     Use of (and where already in place, improvement in the 
performance of) add-on controls, such as scrubbers, fabric filters, 
thermal oxidizers and other devices that control and reduce 
emissions after they are produced, and
     Combinations of inherently lower-emitting processes and 
add-on controls.
    4. In the course of the BART review, one or more of the 
available control options may be eliminated from consideration 
because they are demonstrated to be technically infeasible or to 
have unacceptable energy, cost, or non-air quality environmental 
impacts on a case-by-case (or site-specific) basis. However, at the 
outset, you should initially identify all control options with 
potential application to the emissions unit under review.
    5. We do not consider BART as a requirement to redesign the 
source when considering available control alternatives. For example, 
where the source subject to BART is a coal-fired electric generator, 
we do not require the BART analysis to consider building a natural 
gas-fired electric turbine although the turbine may be inherently 
less polluting on a per unit basis.
    6. For emission units subject to a BART review, there will often 
be control measures or devices already in place. For such emission 
units, it is important to include control options that involve 
improvements to existing controls and not to limit the control 
options only to those measures that involve a complete replacement 
of control devices.

    Example: For a power plant with an existing wet scrubber, the 
current control efficiency is 66 percent. Part of the reason for the 
relatively low control efficiency is that 22 percent of the gas 
stream bypasses the scrubber. A BART review identifies options for 
improving the performance of the wet scrubber by redesigning the 
internal components of the scrubber and by eliminating or reducing 
the percentage of the gas stream that bypasses the scrubber. Four 
control options are identified: (1) 78 percent control based upon 
improved scrubber performance while maintaining the 22 percent 
bypass, (2) 83 percent control based upon improved scrubber 
performance while reducing the bypass to 15 percent, (3) 93 percent 
control based upon improving the scrubber performance while 
eliminating the bypass entirely, (this option results in a ``wet 
stack'' operation in which the gas leaving the stack is saturated 
with water) and (4) 93 percent as in option 3, with the addition of 
an indirect reheat system to reheat the stack gas above the 
saturation temperature. You must consider each of these four options 
in a BART analysis for this source.

    7. You are expected to identify potentially applicable retrofit 
control technologies that represent the full range of demonstrated 
alternatives. Examples of general information sources to consider 
include:
     The EPA's Clean Air Technology Center, which includes 
the RACT/BACT/LAER Clearinghouse (RBLC);
     State and Local Best Available Control Technology 
Guidelines--many agencies have online information--for example South 
Coast Air Quality Management District, Bay Area Air Quality 
Management District, and Texas Natural Resources Conservation 
Commission;
     Control technology vendors;
     Federal/State/Local NSR permits and associated 
inspection/performance test reports;
     Environmental consultants;
     Technical journals, reports and newsletters, air 
pollution control seminars; and
     The EPA's NSR bulletin board--http://www.epa.gov/ttn/nsr;
     Department of Energy's Clean Coal Program--technical 
reports;
     The NOX Control Technology ``Cost Tool''--
Clean Air Markets Division Web page--http://www.epa.gov/airmarkets/arp/nox/controltech.html;
     Performance of selective catalytic reduction on coal-
fired steam generating units--final report. OAR/ARD, June 1997 (also 
available at http://www.epa.gov/airmarkets/arp/nox/controltech.html);
     Cost estimates for selected applications of 
NOX control technologies on stationary combustion 
boilers. OAR/ARD June 1997. (Docket for NOX SIP Call, A-
96-56, item II-A-03);
     Investigation of performance and cost of NOX 
controls as applied to group 2 boilers. OAR/ARD, August 1996. 
(Docket for Phase II NOX rule, A-95-28, item IV-A-4);
     Controlling SO2 Emissions: A Review of 
Technologies. EPA-600/R-00-093, USEPA/ORD/NRMRL, October 2000; and
     The OAQPS Control Cost Manual.
    You are expected to compile appropriate information from these 
information sources.
    8. There may be situations where a specific set of units within 
a fenceline constitutes the

[[Page 39165]]

logical set to which controls would apply and that set of units may 
or may not all be BART-eligible. (For example, some units in that 
set may not have been constructed between 1962 and 1977.)
    9. If you find that a BART source has controls already in place 
which are the most stringent controls available (note that this 
means that all possible improvements to any control devices have 
been made), then it is not necessary to comprehensively complete 
each following step of the BART analysis in this section. As long 
these most stringent controls available are made federally 
enforceable for the purpose of implementing BART for that source, 
you may skip the remaining analyses in this section, including the 
visibility analysis in step 5. Likewise, if a source commits to a 
BART determination that consists of the most stringent controls 
available, then there is no need to complete the remaining analyses 
in this section.

2. STEP 2: How do I determine whether the options identified in Step 1 
are technically feasible?

    In Step 2, you evaluate the technical feasibility of the control 
options you identified in Step 1. You should document a 
demonstration of technical infeasibility and should explain, based 
on physical, chemical, or engineering principles, why technical 
difficulties would preclude the successful use of the control option 
on the emissions unit under review. You may then eliminate such 
technically infeasible control options from further consideration in 
the BART analysis.

In general, what do we mean by technical feasibility?

    Control technologies are technically feasible if either (1) they 
have been installed and operated successfully for the type of source 
under review under similar conditions, or (2) the technology could 
be applied to the source under review. Two key concepts are 
important in determining whether a technology could be applied: 
``availability'' and ``applicability.'' As explained in more detail 
below, a technology is considered ``available'' if the source owner 
may obtain it through commercial channels, or it is otherwise 
available within the common sense meaning of the term. An available 
technology is ``applicable'' if it can reasonably be installed and 
operated on the source type under consideration. A technology that 
is available and applicable is technically feasible.

What do we mean by ``available'' technology?

    1. The typical stages for bringing a control technology concept 
to reality as a commercial product are:
     Concept stage;
     Research and patenting;
     Bench scale or laboratory testing;
     Pilot scale testing;
     Licensing and commercial demonstration; and
     Commercial sales.
    2. A control technique is considered available, within the 
context presented above, if it has reached the stage of licensing 
and commercial availability. Similarly, we do not expect a source 
owner to conduct extended trials to learn how to apply a technology 
on a totally new and dissimilar source type. Consequently, you would 
not consider technologies in the pilot scale testing stages of 
development as ``available'' for purposes of BART review.
    3. Commercial availability by itself, however, is not 
necessarily a sufficient basis for concluding a technology to be 
applicable and therefore technically feasible. Technical 
feasibility, as determined in Step 2, also means a control option 
may reasonably be deployed on or ``applicable'' to the source type 
under consideration.
    Because a new technology may become available at various points 
in time during the BART analysis process, we believe that guidelines 
are needed on when a technology must be considered. For example, a 
technology may become available during the public comment period on 
the State's rule development process. Likewise, it is possible that 
new technologies may become available after the close of the State's 
public comment period and before submittal of the SIP to EPA, or 
during EPA's review process on the SIP submittal. In order to 
provide certainty in the process, all technologies should be 
considered if available before the close of the State's public 
comment period. You need not consider technologies that become 
available after this date. As part of your analysis, you should 
consider any technologies brought to your attention in public 
comments. If you disagree with public comments asserting that the 
technology is available, you should provide an explanation for the 
public record as to the basis for your conclusion.

What do we mean by ``applicable'' technology?

    You need to exercise technical judgment in determining whether a 
control alternative is applicable to the source type under 
consideration. In general, a commercially available control option 
will be presumed applicable if it has been used on the same or a 
similar source type. Absent a showing of this type, you evaluate 
technical feasibility by examining the physical and chemical 
characteristics of the pollutant-bearing gas stream, and comparing 
them to the gas stream characteristics of the source types to which 
the technology had been applied previously. Deployment of the 
control technology on a new or existing source with similar gas 
stream characteristics is generally a sufficient basis for 
concluding the technology is technically feasible barring a 
demonstration to the contrary as described below.

What type of demonstration is required if I conclude that an option is 
not technically feasible?

    1. Where you conclude that a control option identified in Step 1 
is technically infeasible, you should demonstrate that the option is 
either commercially unavailable, or that specific circumstances 
preclude its application to a particular emission unit. Generally, 
such a demonstration involves an evaluation of the characteristics 
of the pollutant-bearing gas stream and the capabilities of the 
technology. Alternatively, a demonstration of technical 
infeasibility may involve a showing that there are unresolvable 
technical difficulties with applying the control to the source 
(e.g., size of the unit, location of the proposed site, operating 
problems related to specific circumstances of the source, space 
constraints, reliability, and adverse side effects on the rest of 
the facility). Where the resolution of technical difficulties is 
merely a matter of increased cost, you should consider the 
technology to be technically feasible. The cost of a control 
alternative is considered later in the process.
    2. The determination of technical feasibility is sometimes 
influenced by recent air quality permits. In some cases, an air 
quality permit may require a certain level of control, but the level 
of control in a permit is not expected to be achieved in practice 
(e.g., a source has received a permit but the project was canceled, 
or every operating source at that permitted level has been 
physically unable to achieve compliance with the limit). Where this 
is the case, you should provide supporting documentation showing why 
such limits are not technically feasible, and, therefore, why the 
level of control (but not necessarily the technology) may be 
eliminated from further consideration. However, if there is a permit 
requiring the application of a certain technology or emission limit 
to be achieved for such technology, this usually is sufficient 
justification for you to assume the technical feasibility of that 
technology or emission limit.
    3. Physical modifications needed to resolve technical obstacles 
do not, in and of themselves, provide a justification for 
eliminating the control technique on the basis of technical 
infeasibility. However, you may consider the cost of such 
modifications in estimating costs. This, in turn, may form the basis 
for eliminating a control technology (see later discussion).
    4. Vendor guarantees may provide an indication of commercial 
availability and the technical feasibility of a control technique 
and could contribute to a determination of technical feasibility or 
technical infeasibility, depending on circumstances. However, we do 
not consider a vendor guarantee alone to be sufficient justification 
that a control option will work. Conversely, lack of a vendor 
guarantee by itself does not present sufficient justification that a 
control option or an emissions limit is technically infeasible. 
Generally, you should make decisions about technical feasibility 
based on chemical, and engineering analyses (as discussed above), in 
conjunction with information about vendor guarantees.
    5. A possible outcome of the BART procedures discussed in these 
guidelines is the evaluation of multiple control technology 
alternatives which result in essentially equivalent emissions. It is 
not our intent to encourage evaluation of unnecessarily large 
numbers of control alternatives for every emissions unit. 
Consequently, you should use judgment in deciding on those 
alternatives for which you will conduct the detailed impacts 
analysis (Step 4 below). For example, if two or more control 
techniques result in control levels that are essentially identical, 
considering the uncertainties of emissions factors and other 
parameters

[[Page 39166]]

pertinent to estimating performance, you may evaluate only the less 
costly of these options. You should narrow the scope of the BART 
analysis in this way only if there is a negligible difference in 
emissions and energy and non-air quality environmental impacts 
between control alternatives.

3. STEP 3: How do I evaluate technically feasible alternatives?

    Step 3 involves evaluating the control effectiveness of all the 
technically feasible control alternatives identified in Step 2 for 
the pollutant and emissions unit under review.
    Two key issues in this process include:
    (1) Making sure that you express the degree of control using a 
metric that ensures an ``apples to apples'' comparison of emissions 
performance levels among options, and
    (2) Giving appropriate treatment and consideration of control 
techniques that can operate over a wide range of emission 
performance levels.

What are the appropriate metrics for comparison?

    This issue is especially important when you compare inherently 
lower-polluting processes to one another or to add-on controls. In 
such cases, it is generally most effective to express emissions 
performance as an average steady state emissions level per unit of 
product produced or processed.
    Examples of common metrics:
     Pounds of SO2 emissions per million Btu heat 
input, and
     Pounds of NOX emissions per ton of cement 
produced.

How do I evaluate control techniques with a wide range of emission 
performance levels?

    1. Many control techniques, including both add-on controls and 
inherently lower polluting processes, can perform at a wide range of 
levels. Scrubbers and high and low efficiency electrostatic 
precipitators (ESPs) are two of the many examples of such control 
techniques that can perform at a wide range of levels. It is not our 
intent to require analysis of each possible level of efficiency for 
a control technique as such an analysis would result in a large 
number of options. It is important, however, that in analyzing the 
technology you take into account the most stringent emission control 
level that the technology is capable of achieving. You should 
consider recent regulatory decisions and performance data (e.g., 
manufacturer's data, engineering estimates and the experience of 
other sources) when identifying an emissions performance level or 
levels to evaluate.
    2. In assessing the capability of the control alternative, 
latitude exists to consider special circumstances pertinent to the 
specific source under review, or regarding the prior application of 
the control alternative. However, you should explain the basis for 
choosing the alternate level (or range) of control in the BART 
analysis. Without a showing of differences between the source and 
other sources that have achieved more stringent emissions limits, 
you should conclude that the level being achieved by those other 
sources is representative of the achievable level for the source 
being analyzed.
    3. You may encounter cases where you may wish to evaluate other 
levels of control in addition to the most stringent level for a 
given device. While you must consider the most stringent level as 
one of the control options, you may consider less stringent levels 
of control as additional options. This would be useful, particularly 
in cases where the selection of additional options would have widely 
varying costs and other impacts.
    4. Finally, we note that for retrofitting existing sources in 
addressing BART, you should consider ways to improve the performance 
of existing control devices, particularly when a control device is 
not achieving the level of control that other similar sources are 
achieving in practice with the same device. For example, you should 
consider requiring those sources with electrostatic precipitators 
(ESPs) performing below currently achievable levels to improve their 
performance.

4. STEP 4: For a BART review, what impacts am I expected to calculate 
and report? What methods does EPA recommend for the impacts analysis?

    After you identify the available and technically feasible 
control technology options, you are expected to conduct the 
following analyses when you make a BART determination:

    Impact analysis part 1: Costs of compliance,
    Impact analysis part 2: Energy impacts, and
    Impact analysis part 3: Non-air quality environmental impacts.
    Impact analysis part 4: Remaining useful life.

In this section, we describe how to conduct each of these three 
analyses. You are responsible for presenting an evaluation of each 
impact along with appropriate supporting information. You should 
discuss and, where possible, quantify both beneficial and adverse 
impacts. In general, the analysis should focus on the direct impact 
of the control alternative.

a. Impact analysis part 1: how do I estimate the costs of control?

    1. To conduct a cost analysis, you:
    (1) Identify the emissions units being controlled,
    (2) Identify design parameters for emission controls, and
    (3) Develop cost estimates based upon those design parameters.
    2. It is important to identify clearly the emission units being 
controlled, that is, to specify a well-defined area or process 
segment within the plant. In some cases, multiple emission units can 
be controlled jointly. However, in other cases, it may be 
appropriate in the cost analysis to consider whether multiple units 
will be required to install separate and/or different control 
devices. The analysis should provide a clear summary list of 
equipment and the associated control costs. Inadequate documentation 
of the equipment whose emissions are being controlled is a potential 
cause for confusion in comparison of costs of the same controls 
applied to similar sources.
    3. You then specify the control system design parameters. 
Potential sources of these design parameters include equipment 
vendors, background information documents used to support NSPS 
development, control technique guidelines documents, cost manuals 
developed by EPA, control data in trade publications, and 
engineering and performance test data. The following are a few 
examples of design parameters for two example control measures:

------------------------------------------------------------------------
            Control device               Examples of design  parameters
------------------------------------------------------------------------
Wet Scrubbers.........................  Type of sorbent used (lime,
                                         limestone, etc.).
                                        Gas pressure drop.
                                        Liquid/gas ratio.
Selective Catalytic Reduction.........  Ammonia to NOX molar ratio.
                                        Pressure drop.
                                        Catalyst life.
------------------------------------------------------------------------

    4. The value selected for the design parameter should ensure 
that the control option will achieve the level of emission control 
being evaluated. You should include in your analysis documentation 
of your assumptions regarding design parameters. Examples of 
supporting references would include the EPA OAQPS Control Cost 
Manual (see below) and background information documents used for 
NSPS and hazardous pollutant emission standards. If the design 
parameters you specified differ from typical designs, you should 
document the difference by supplying performance test data for the 
control technology in question applied to the same source or a 
similar source.
    5. Once the control technology alternatives and achievable 
emissions performance levels have been identified, you then develop 
estimates of capital and annual costs. The basis for equipment cost 
estimates also should be documented, either with data supplied by an 
equipment vendor (i.e., budget estimates or bids) or by a referenced 
source (such as the OAQPS Control Cost Manual, Fifth Edition, 
February 1996, EPA 453/B-96-001).\14\ In order to maintain and 
improve consistency, cost estimates should be based on the OAQPS 
Control Cost Manual, where possible.\15\ The Control Cost Manual 
addresses most control technologies in sufficient detail for a BART 
analysis. The cost analysis should also take into account any site-
specific design or other conditions identified above that affect the 
cost of a particular BART technology option.
---------------------------------------------------------------------------

    \14\ The OAQPS Control Cost Manual is updated periodically. 
While this citation refers to the latest version at the time this 
guidance was written, you should use the version that is current as 
of when you conduct your impact analysis. This document is available 
at the following Web site: http://www.epa.gov/ttn/catc/dir1/cs1ch2.pdf.
    \15\ You should include documentation for any additional 
information you used for the cost calculations, including any 
information supplied by vendors that affects your assumptions 
regarding purchased equipment costs, equipment life, replacement of 
major components, and any other element of the calculation that 
differs from the Control Cost Manual.

---------------------------------------------------------------------------

[[Page 39167]]

b. What do we mean by cost effectiveness?

    Cost effectiveness, in general, is a criterion used to assess 
the potential for achieving an objective in the most economical way. 
For purposes of air pollutant analysis, ``effectiveness'' is 
measured in terms of tons of pollutant emissions removed, and 
``cost'' is measured in terms of annualized control costs. We 
recommend two types of cost-effectiveness calculations--average cost 
effectiveness, and incremental cost effectiveness.

c. How do I calculate average cost effectiveness?

    Average cost effectiveness means the total annualized costs of 
control divided by annual emissions reductions (the difference 
between baseline annual emissions and the estimate of emissions 
after controls), using the following formula:

Average cost effectiveness (dollars per ton removed) = Control 
option annualized cost \16\
---------------------------------------------------------------------------

    \16\ Whenever you calculate or report annual costs, you should 
indicate the year for which the costs are estimated. For example, if 
you use the year 2000 as the basis for cost comparisons, you would 
report that an annualized cost of $20 million would be: $20 million 
(year 2000 dollars).

Baseline annual emissions--Annual emissions with Control option
    Because you calculate costs in (annualized) dollars per year ($/
yr) and because you calculate emissions rates in tons per year 
(tons/yr), the result is an average cost-effectiveness number in 
(annualized) dollars per ton ($/ton) of pollutant removed.

d. How do I calculate baseline emissions?

    1. The baseline emissions rate should represent a realistic 
depiction of anticipated annual emissions for the source. In 
general, for the existing sources subject to BART, you will estimate 
the anticipated annual emissions based upon actual emissions from a 
baseline period.
    2. When you project that future operating parameters (e.g., 
limited hours of operation or capacity utilization, type of fuel, 
raw materials or product mix or type) will differ from past 
practice, and if this projection has a deciding effect in the BART 
determination, then you must make these parameters or assumptions 
into enforceable limitations. In the absence of enforceable 
limitations, you calculate baseline emissions based upon 
continuation of past practice.
    3. For example, the baseline emissions calculation for an 
emergency standby generator may consider the fact that the source 
owner would not operate more than past practice of 2 weeks a year. 
On the other hand, baseline emissions associated with a base-loaded 
turbine should be based on its past practice which would indicate a 
large number of hours of operation. This produces a significantly 
higher level of baseline emissions than in the case of the 
emergency/standby unit and results in more cost-effective controls. 
As a consequence of the dissimilar baseline emissions, BART for the 
two cases could be very different.

e. How do I calculate incremental cost effectiveness?

    1. In addition to the average cost effectiveness of a control 
option, you should also calculate incremental cost effectiveness. 
You should consider the incremental cost effectiveness in 
combination with the average cost effectiveness when considering 
whether to eliminate a control option. The incremental cost 
effectiveness calculation compares the costs and performance level 
of a control option to those of the next most stringent option, as 
shown in the following formula (with respect to cost per emissions 
reduction):

Incremental Cost Effectiveness (dollars per incremental ton removed) 
= (Total annualized costs of control option) - (Total annualized 
costs of next control option) / (Control option annual emissions) - 
(Next control option annual emissions)

    Example 1:  Assume that Option F on Figure 2 has total 
annualized costs of $1 million to reduce 2000 tons of a pollutant, 
and that Option D on Figure 2 has total annualized costs of $500,000 
to reduce 1000 tons of the same pollutant. The incremental cost 
effectiveness of Option F relative to Option D is ($1 million - 
$500,000) divided by (2000 tons - 1000 tons), or $500,000 divided by 
1000 tons, which is $500/ton.
    Example 2:  Assume that two control options exist: Option 1 and 
Option 2. Option 1 achieves a 1,000 ton/yr reduction at an 
annualized cost of $1,900,000. This represents an average cost of 
($1,900,000/1,000 tons) = $1,900/ton. Option 2 achieves a 980 tons/
yr reduction at an annualized cost of $1,500,000. This represents an 
average cost of ($1,500,000/980 tons) = $1,531/ton. The incremental 
cost effectiveness of Option 1 relative to Option 2 is ($1,900,000 - 
$1,500,000) divided by (1,000 tons - 980 tons). The adoption of 
Option 1 instead of Option 2 results in an incremental emission 
reduction of 20 tons per year at an additional cost of $400,000 per 
year. The incremental cost of Option 1, then, is $20,000 per ton - 
11 times the average cost of $1,900 per ton. While $1,900 per ton 
may still be deemed reasonable, it is useful to consider both the 
average and incremental cost in making an overall cost-effectiveness 
finding. Of course, there may be other differences between these 
options, such as, energy or water use, or non-air environmental 
effects, which also should be considered in selecting a BART 
technology.

    2. You should exercise care in deriving incremental costs of 
candidate control options. Incremental cost-effectiveness 
comparisons should focus on annualized cost and emission reduction 
differences between ``dominant'' alternatives. To identify dominant 
alternatives, you generate a graphical plot of total annualized 
costs for total emissions reductions for all control alternatives 
identified in the BART analysis, and by identifying a ``least-cost 
envelope'' as shown in Figure 2. (A ``least-cost envelope'' 
represents the set of options that should be dominant in the choice 
of a specific option.)

[[Page 39168]]

[GRAPHIC] [TIFF OMITTED] TR06JY05.000

    Example:  Eight technically feasible control options for 
analysis are listed. These are represented as A through H in Figure 
2. The dominant set of control options, B, D, F, G, and H, represent 
the least-cost envelope, as we depict by the cost curve connecting 
them. Points A, C and E are inferior options, and you should not use 
them in calculating incremental cost effectiveness. Points A, C and 
E represent inferior controls because B will buy more emissions 
reductions for less money than A; and similarly, D and F will buy 
more reductions for less money than C and E, respectively.

    3. In calculating incremental costs, you:
    (1) Array the control options in ascending order of annualized 
total costs,
    (2) Develop a graph of the most reasonable smooth curve of the 
control options, as shown in Figure 2. This is to show the ``least-
cost envelope'' discussed above; and
    (3) Calculate the incremental cost effectiveness for each 
dominant option, which is the difference in total annual costs 
between that option and the next most stringent option, divided by 
the difference in emissions, after controls have been applied, 
between those two control options. For example, using Figure 2, you 
would calculate incremental cost effectiveness for the difference 
between options B and D, options D and F, options F and G, and 
options G and H.
    4. A comparison of incremental costs can also be useful in 
evaluating the viability of a specific control option over a range 
of efficiencies. For example, depending on the capital and 
operational cost of a control device, total and incremental cost may 
vary significantly (either increasing or decreasing) over the 
operational range of a control device. Also, the greater the number 
of possible control options that exist, the more weight should be 
given to the incremental costs vs. average costs. It should be noted 
that average and incremental cost effectiveness are identical when 
only one candidate control option is known to exist.
    5. You should exercise caution not to misuse these techniques. 
For example, you may be faced with a choice between two available 
control devices at a source, control A and control B, where control 
B achieves slightly greater emission reductions. The average cost 
(total annual cost/total annual emission reductions) for each may be 
deemed to be reasonable. However, the incremental cost (total annual 
costA - B/total annual emission 
reductionsA - B) of the additional emission reductions to 
be achieved by control B may be very great. In such an instance, it 
may be inappropriate to choose control B, based on its high 
incremental costs, even though its average cost may be considered 
reasonable.
    6. In addition, when you evaluate the average or incremental 
cost effectiveness of a control alternative, you should make 
reasonable and supportable assumptions regarding control 
efficiencies. An unrealistically low assessment of the emission 
reduction potential of a certain technology could result in inflated 
cost-effectiveness figures.

f. What other information should I provide in the cost impacts 
analysis?

    You should provide documentation of any unusual circumstances 
that exist for the source that would lead to cost-effectiveness 
estimates that would exceed that for recent retrofits. This is 
especially important in cases where recent retrofits have cost-
effectiveness values that are within what has been considered a 
reasonable range, but your analysis concludes that costs for the 
source being analyzed are not considered reasonable. (A reasonable 
range would be a range that is consistent with the range of cost 
effectiveness values used in other similar permit decisions over a 
period of time.)

    Example:  In an arid region, large amounts of water are needed 
for a scrubbing system. Acquiring water from a distant location 
could greatly increase the cost per ton of emissions reduced of wet 
scrubbing as a control option.

g. What other things are important to consider in the cost impacts 
analysis?

    In the cost analysis, you should take care not to focus on 
incomplete results or partial calculations. For example, large 
capital costs for a control option alone would not preclude 
selection of a control measure if large emissions reductions are 
projected. In such a case, low or reasonable cost effectiveness 
numbers may validate the option as an appropriate BART alternative 
irrespective of the large capital costs. Similarly, projects with 
relatively low capital costs may not be cost effective if there are 
few emissions reduced.

h. Impact analysis part 2: How should I analyze and report energy 
impacts?

    1. You should examine the energy requirements of the control 
technology and determine whether the use of that technology results 
in energy penalties or benefits. A source owner may, for example, 
benefit from the combustion of a concentrated gas stream rich in 
volatile organic compounds; on the other hand, more often extra fuel 
or electricity is required to power a control

[[Page 39169]]

device or incinerate a dilute gas stream. If such benefits or 
penalties exist, they should be quantified to the extent 
practicable. Because energy penalties or benefits can usually be 
quantified in terms of additional cost or income to the source, the 
energy impacts analysis can, in most cases, simply be factored into 
the cost impacts analysis. The fact of energy use in and of itself 
does not disqualify a technology.
    2. Your energy impact analysis should consider only direct 
energy consumption and not indirect energy impacts. For example, you 
could estimate the direct energy impacts of the control alternative 
in units of energy consumption at the source (e.g., BTU, kWh, 
barrels of oil, tons of coal). The energy requirements of the 
control options should be shown in terms of total (and in certain 
cases, also incremental) energy costs per ton of pollutant removed. 
You can then convert these units into dollar costs and, where 
appropriate, factor these costs into the control cost analysis.
    3. You generally do not consider indirect energy impacts (such 
as energy to produce raw materials for construction of control 
equipment). However, if you determine, either independently or based 
on a showing by the source owner, that the indirect energy impact is 
unusual or significant and that the impact can be well quantified, 
you may consider the indirect impact.
    4. The energy impact analysis may also address concerns over the 
use of locally scarce fuels. The designation of a scarce fuel may 
vary from region to region. However, in general, a scarce fuel is 
one which is in short supply locally and can be better used for 
alternative purposes, or one which may not be reasonably available 
to the source either at the present time or in the near future.
    5. Finally, the energy impacts analysis may consider whether 
there are relative differences between alternatives regarding the 
use of locally or regionally available coal, and whether a given 
alternative would result in significant economic disruption or 
unemployment. For example, where two options are equally cost 
effective and achieve equivalent or similar emissions reductions, 
one option may be preferred if the other alternative results in 
significant disruption or unemployment.

i. Impact analysis part 3: How do I analyze ``non-air quality 
environmental impacts?''

    1. In the non-air quality related environmental impacts portion 
of the BART analysis, you address environmental impacts other than 
air quality due to emissions of the pollutant in question. Such 
environmental impacts include solid or hazardous waste generation 
and discharges of polluted water from a control device.
    2. You should identify any significant or unusual environmental 
impacts associated with a control alternative that have the 
potential to affect the selection or elimination of a control 
alternative. Some control technologies may have potentially 
significant secondary environmental impacts. Scrubber effluent, for 
example, may affect water quality and land use. Alternatively, water 
availability may affect the feasibility and costs of wet scrubbers. 
Other examples of secondary environmental impacts could include 
hazardous waste discharges, such as spent catalysts or contaminated 
carbon. Generally, these types of environmental concerns become 
important when sensitive site-specific receptors exist or when the 
incremental emissions reductions potential of the more stringent 
control is only marginally greater than the next most-effective 
option. However, the fact that a control device creates liquid and 
solid waste that must be disposed of does not necessarily argue 
against selection of that technology as BART, particularly if the 
control device has been applied to similar facilities elsewhere and 
the solid or liquid waste is similar to those other applications. On 
the other hand, where you or the source owner can show that unusual 
circumstances at the proposed facility create greater problems than 
experienced elsewhere, this may provide a basis for the elimination 
of that control alternative as BART.
    3. The procedure for conducting an analysis of non-air quality 
environmental impacts should be made based on a consideration of 
site-specific circumstances. If you propose to adopt the most 
stringent alternative, then it is not necessary to perform this 
analysis of environmental impacts for the entire list of 
technologies you ranked in Step 3. In general, the analysis need 
only address those control alternatives with any significant or 
unusual environmental impacts that have the potential to affect the 
selection of a control alternative, or elimination of a more 
stringent control alternative. Thus, any important relative 
environmental impacts (both positive and negative) of alternatives 
can be compared with each other.
    4. In general, the analysis of impacts starts with the 
identification and quantification of the solid, liquid, and gaseous 
discharges from the control device or devices under review. 
Initially, you should perform a qualitative or semi-quantitative 
screening to narrow the analysis to discharges with potential for 
causing adverse environmental effects. Next, you should assess the 
mass and composition of any such discharges and quantify them to the 
extent possible, based on readily available information. You should 
also assemble pertinent information about the public or 
environmental consequences of releasing these materials.

j. Impact analysis part 4: What are examples of non-air quality 
environmental impacts?

    The following are examples of how to conduct non-air quality 
environmental impacts:
    (1) Water Impact
    You should identify the relative quantities of water used and 
water pollutants produced and discharged as a result of the use of 
each alternative emission control system. Where possible, you should 
assess the effect on ground water and such local surface water 
quality parameters as ph, turbidity, dissolved oxygen, salinity, 
toxic chemical levels, temperature, and any other important 
considerations. The analysis could consider whether applicable water 
quality standards will be met and the availability and effectiveness 
of various techniques to reduce potential adverse effects.
    (2) Solid Waste Disposal Impact
    You could also compare the quality and quantity of solid waste 
(e.g., sludges, solids) that must be stored and disposed of or 
recycled as a result of the application of each alternative emission 
control system. You should consider the composition and various 
other characteristics of the solid waste (such as permeability, 
water retention, rewatering of dried material, compression strength, 
leachability of dissolved ions, bulk density, ability to support 
vegetation growth and hazardous characteristics) which are 
significant with regard to potential surface water pollution or 
transport into and contamination of subsurface waters or aquifers.
    (3) Irreversible or Irretrievable Commitment of Resources
    You may consider the extent to which the alternative emission 
control systems may involve a trade-off between short-term 
environmental gains at the expense of long-term environmental losses 
and the extent to which the alternative systems may result in 
irreversible or irretrievable commitment of resources (for example, 
use of scarce water resources).
    (4) Other Adverse Environmental Impacts
    You may consider significant differences in noise levels, 
radiant heat, or dissipated static electrical energy of pollution 
control alternatives. Other examples of non-air quality 
environmental impacts would include hazardous waste discharges such 
as spent catalysts or contaminated carbon.

k. How do I take into account a project's ``remaining useful life'' in 
calculating control costs?

    1. You may decide to treat the requirement to consider the 
source's ``remaining useful life'' of the source for BART 
determinations as one element of the overall cost analysis. The 
``remaining useful life'' of a source, if it represents a relatively 
short time period, may affect the annualized costs of retrofit 
controls. For example, the methods for calculating annualized costs 
in EPA's OAQPS Control Cost Manual require the use of a specified 
time period for amortization that varies based upon the type of 
control. If the remaining useful life will clearly exceed this time 
period, the remaining useful life has essentially no effect on 
control costs and on the BART determination process. Where the 
remaining useful life is less than the time period for amortizing 
costs, you should use this shorter time period in your cost 
calculations.
    2. For purposes of these guidelines, the remaining useful life 
is the difference between:
    (1) The date that controls will be put in place (capital and 
other construction costs incurred before controls are put in place 
can be rolled into the first year, as suggested in EPA's OAQPS 
Control Cost Manual); you are conducting the BART analysis; and
    (2) The date the facility permanently stops operations. Where 
this affects the BART determination, this date should be assured by 
a federally- or State-enforceable restriction preventing further 
operation.
    3. We recognize that there may be situations where a source 
operator intends to shut down a source by a given date, but wishes 
to retain the flexibility to continue

[[Page 39170]]

operating beyond that date in the event, for example, that market 
conditions change. Where this is the case, your BART analysis may 
account for this, but it must maintain consistency with the 
statutory requirement to install BART within 5 years. Where the 
source chooses not to accept a federally enforceable condition 
requiring the source to shut down by a given date, it is necessary 
to determine whether a reduced time period for the remaining useful 
life changes the level of controls that would have been required as 
BART.
    If the reduced time period does change the level of BART 
controls, you may identify, and include as part of the BART emission 
limitation, the more stringent level of control that would be 
required as BART if there were no assumption that reduced the 
remaining useful life. You may incorporate into the BART emission 
limit this more stringent level, which would serve as a contingency 
should the source continue operating more than 5 years after the 
date EPA approves the relevant SIP. The source would not be allowed 
to operate after the 5-year mark without such controls. If a source 
does operate after the 5-year mark without BART in place, the source 
is considered to be in violation of the BART emissions limit for 
each day of operation.

5. Step 5: How should I determine visibility impacts in the BART 
determination?

    The following is an approach you may use to determine visibility 
impacts (the degree of visibility improvement for each source 
subject to BART) for the BART determination. Once you have 
determined that your source or sources are subject to BART, you must 
conduct a visibility improvement determination for the source(s) as 
part of the BART determination. When making this determination, we 
believe you have flexibility in setting absolute thresholds, target 
levels of improvement, or de minimis levels since the deciview 
improvement must be weighed among the five factors, and you are free 
to determine the weight and significance to be assigned to each 
factor. For example, a 0.3 deciview improvement may merit a stronger 
weighting in one case versus another, so one ``bright line'' may not 
be appropriate. [Note that if sources have elected to apply the most 
stringent controls available, consistent with the discussion in 
section E. step 1. below, you need not conduct, or require the 
source to conduct, an air quality modeling analysis for the purpose 
of determining its visibility impacts.]
    Use CALPUFF,\17\ or other appropriate dispersion model to 
determine the visibility improvement expected at a Class I area from 
the potential BART control technology applied to the source. 
Modeling should be conducted for SO2, NOX, and 
direct PM emissions (PM2.5 and/or PM10). If 
the source is making the visibility determination, you should review 
and approve or disapprove of the source's analysis before making the 
expected improvement determination. There are several steps for 
determining the visibility impacts from an individual source using a 
dispersion model:
---------------------------------------------------------------------------

    \17\ The model code and its documentation are available at no 
cost for download from http://www.epa.gov/scram001/tt22.htm#calpuff.
---------------------------------------------------------------------------

     Develop a modeling protocol.
    Some critical items to include in a modeling protocol are 
meteorological and terrain data, as well as source-specific 
information (stack height, temperature, exit velocity, elevation, 
and allowable and actual emission rates of applicable pollutants), 
and receptor data from appropriate Class I areas. We recommend 
following EPA's Interagency Workgroup on Air Quality Modeling 
(IWAQM) Phase 2 Summary Report and Recommendations for Modeling Long 
Range Transport Impacts \18\ for parameter settings and 
meteorological data inputs; the use of other settings from those in 
IWAQM should be identified and explained in the protocol.
---------------------------------------------------------------------------

    \18\ Interagency Workgroup on Air Quality Modeling (IWAQM) Phase 
2 Summary Report and Recommendations for Modeling Long Range 
Transport Impacts, U.S. Environmental Protection Agency, EPA-454/R-
98-019, December 1998.
---------------------------------------------------------------------------

    One important element of the protocol is in establishing the 
receptors that will be used in the model. The receptors that you use 
should be located in the nearest Class I area with sufficient 
density to identify the likely visibility effects of the source. For 
other Class I areas in relatively close proximity to a BART-eligible 
source, you may model a few strategic receptors to determine whether 
effects at those areas may be greater than at the nearest Class I 
area. For example, you might chose to locate receptors at these 
areas at the closest point to the source, at the highest and lowest 
elevation in the Class I area, at the IMPROVE monitor, and at the 
approximate expected plume release height. If the highest modeled 
effects are observed at the nearest Class I area, you may choose not 
to analyze the other Class I areas any further as additional 
analyses might be unwarranted.
    You should bear in mind that some receptors within the relevant 
Class I area may be less than 50 km from the source while other 
receptors within that same Class I area may be greater than 50 km 
from the same source. As indicated by the Guideline on Air Quality 
Models, this situation may call for the use of two different 
modeling approaches for the same Class I area and source, depending 
upon the State's chosen method for modeling sources less than 50 km. 
In situations where you are assessing visibility impacts for source-
receptor distances less than 50 km, you should use expert modeling 
judgment in determining visibility impacts, giving consideration to 
both CALPUFF and other EPA-approved methods.
    In developing your modeling protocol, you may want to consult 
with EPA and your regional planning organization (RPO). Up-front 
consultation will ensure that key technical issues are addressed 
before you conduct your modeling.
     For each source, run the model, at pre-control and 
post-control emission rates according to the accepted methodology in 
the protocol.
    Use the 24-hour average actual emission rate from the highest 
emitting day of the meteorological period modeled (for the pre-
control scenario). Calculate the model results for each receptor as 
the change in deciviews compared against natural visibility 
conditions. Post-control emission rates are calculated as a 
percentage of pre-control emission rates. For example, if the 24-hr 
pre-control emission rate is 100 lb/hr of SO2, then the 
post control rate is 5 lb/hr if the control efficiency being 
evaluated is 95 percent.
     Make the net visibility improvement determination.
    Assess the visibility improvement based on the modeled change in 
visibility impacts for the pre-control and post-control emission 
scenarios. You have flexibility to assess visibility improvements 
due to BART controls by one or more methods. You may consider the 
frequency, magnitude, and duration components of impairment. 
Suggestions for making the determination are:
     Use of a comparison threshold, as is done for 
determining if BART-eligible sources should be subject to a BART 
determination. Comparison thresholds can be used in a number of ways 
in evaluating visibility improvement (e.g. the number of days or 
hours that the threshold was exceeded, a single threshold for 
determining whether a change in impacts is significant, or a 
threshold representing an x percent change in improvement).
     Compare the 98th percent days for the pre- and post-
control runs.
    Note that each of the modeling options may be supplemented with 
source apportionment data or source apportionment modeling.

E. How do I select the ``best'' alternative, using the results of 
Steps 1 through 5?

1. Summary of the Impacts Analysis

    From the alternatives you evaluated in Step 3, we recommend you 
develop a chart (or charts) displaying for each of the alternatives:
    (1) Expected emission rate (tons per year, pounds per hour);
    (2) Emissions performance level (e.g., percent pollutant 
removed, emissions per unit product, lb/MMBtu, ppm);
    (3) Expected emissions reductions (tons per year);
    (4) Costs of compliance--total annualized costs ($), cost 
effectiveness ($/ton), and incremental cost effectiveness ($/ton), 
and/or any other cost-effectiveness measures (such as $/deciview);
    (5) Energy impacts;
    (6) Non-air quality environmental impacts; and
    (7) Modeled visibility impacts.

2. Selecting a ``best'' alternative

    1. You have discretion to determine the order in which you 
should evaluate control options for BART. Whatever the order in 
which you choose to evaluate options, you should always (1) display 
the options evaluated; (2) identify the average and incremental 
costs of each option; (3) consider the energy and non-air quality 
environmental impacts of each option; (4) consider the remaining 
useful life; and (5) consider the modeled visibility impacts. You 
should provide a justification for adopting the technology that you 
select as the ``best'' level of control, including an explanation of 
the

[[Page 39171]]

CAA factors that led you to choose that option over other control 
levels.
    2. In the case where you are conducting a BART determination for 
two regulated pollutants on the same source, if the result is two 
different BART technologies that do not work well together, you 
could then substitute a different technology or combination of 
technologies.

3. In selecting a ``best'' alternative, should I consider the 
affordability of controls?

    1. Even if the control technology is cost effective, there may 
be cases where the installation of controls would affect the 
viability of continued plant operations.
    2. There may be unusual circumstances that justify taking into 
consideration the conditions of the plant and the economic effects 
of requiring the use of a given control technology. These effects 
would include effects on product prices, the market share, and 
profitability of the source. Where there are such unusual 
circumstances that are judged to affect plant operations, you may 
take into consideration the conditions of the plant and the economic 
effects of requiring the use of a control technology. Where these 
effects are judged to have a severe impact on plant operations you 
may consider them in the selection process, but you may wish to 
provide an economic analysis that demonstrates, in sufficient detail 
for public review, the specific economic effects, parameters, and 
reasoning. (We recognize that this review process must preserve the 
confidentiality of sensitive business information). Any analysis may 
also consider whether other competing plants in the same industry 
have been required to install BART controls if this information is 
available.

4. Sulfur dioxide limits for utility boilers

    You must require 750 MW power plants to meet specific control 
levels for SO2 of either 95 percent control or 0.15 lbs/
MMBtu, for each EGU greater than 200 MW that is currently 
uncontrolled unless you determine that an alternative control level 
is justified based on a careful consideration of the statutory 
factors. Thus, for example, if the source demonstrates circumstances 
affecting its ability to cost-effectively reduce its emissions, you 
should take that into account in determining whether the presumptive 
levels of control are appropriate for that facility. For a currently 
uncontrolled EGU greater than 200 MW in size, but located at a power 
plant smaller than 750 MW in size, such controls are generally cost-
effective and could be used in your BART determination considering 
the five factors specified in CAA section 169A(g)(2). While these 
levels may represent current control capabilities, we expect that 
scrubber technology will continue to improve and control costs 
continue to decline. You should be sure to consider the level of 
control that is currently best achievable at the time that you are 
conducting your BART analysis.
    For coal-fired EGUs with existing post-combustion SO2 
controls achieving less than 50 percent removal efficiencies, we 
recommend that you evaluate constructing a new FGD system to meet 
the same emission limits as above (95 percent removal or 0.15 lb/
mmBtu), in addition to the evaluation of scrubber upgrades discussed 
below. For oil-fired units, regardless of size, you should evaluate 
limiting the sulfur content of the fuel oil burned to 1 percent or 
less by weight.
    For those BART-eligible EGUs with pre-existing post-combustion 
SO2 controls achieving removal efficiencies of at least 
50 percent, your BART determination should consider cost effective 
scrubber upgrades designed to improve the system's overall 
SO2 removal efficiency. There are numerous scrubber 
enhancements available to upgrade the average removal efficiencies 
of all types of existing scrubber systems. We recommend that as you 
evaluate the definition of ``upgrade,'' you evaluate options that 
not only improve the design removal efficiency of the scrubber 
vessel itself, but also consider upgrades that can improve the 
overall SO2 removal efficiency of the scrubber system. 
Increasing a scrubber system's reliability, and conversely 
decreasing its downtime, by way of optimizing operation procedures, 
improving maintenance practices, adjusting scrubber chemistry, and 
increasing auxiliary equipment redundancy, are all ways to improve 
average SO2 removal efficiencies.
    We recommend that as you evaluate the performance of existing 
wet scrubber systems, you consider some of the following upgrades, 
in no particular order, as potential scrubber upgrades that have 
been proven in the industry as cost effective means to increase 
overall SO2 removal of wet systems:
    (a) Elimination of Bypass Reheat;
    (b) Installation of Liquid Distribution Rings;
    (c) Installation of Perforated Trays;
    (d) Use of Organic Acid Additives;
    (e) Improve or Upgrade Scrubber Auxiliary System Equipment;
    (f) Redesign Spray Header or Nozzle Configuration.
    We recommend that as you evaluate upgrade options for dry 
scrubber systems, you should consider the following cost effective 
upgrades, in no particular order:
    (a) Use of Performance Additives;
    (b) Use of more Reactive Sorbent;
    (c) Increase the Pulverization Level of Sorbent;
    (d) Engineering redesign of atomizer or slurry injection system.
    You should evaluate scrubber upgrade options based on the 5 step 
BART analysis process.

5. Nitrogen oxide limits for utility boilers

    You should establish specific numerical limits for 
NOX control for each BART determination. For power plants 
with a generating capacity in excess of 750 MW currently using 
selective catalytic reduction (SCR) or selective non-catalytic 
reduction (SNCR) for part of the year, you should presume that use 
of those same controls year-round is BART. For other sources 
currently using SCR or SNCR to reduce NOX emissions 
during part of the year, you should carefully consider requiring the 
use of these controls year-round as the additional costs of 
operating the equipment throughout the year would be relatively 
modest.
    For coal-fired EGUs greater than 200 MW located at greater than 
750 MW power plants and operating without post-combustion controls 
(i.e. SCR or SNCR), we have provided presumptive NOX 
limits, differentiated by boiler design and type of coal burned. You 
may determine that an alternative control level is appropriate based 
on a careful consideration of the statutory factors. For coal-fired 
EGUs greater than 200 MW located at power plants 750 MW or less in 
size and operating without post-combustion controls, you should 
likewise presume that these same levels are cost-effective. You 
should require such utility boilers to meet the following 
NOX emission limits, unless you determine that an 
alternative control level is justified based on consideration of the 
statutory factors. The following NOX emission rates were 
determined based on a number of assumptions, including that the EGU 
boiler has enough volume to allow for installation and effective 
operation of separated overfire air ports. For boilers where these 
assumptions are incorrect, these emission limits may not be cost-
effective.

[[Page 39172]]



 Table 1.--Presumptive NOX Emission Limits for BART-Eligible Coal-Fired
                               Units.\19\
------------------------------------------------------------------------
                                                         NOX presumptive
           Unit type                   Coal type           limit  (lb/
                                                           mmbtu) \20\
------------------------------------------------------------------------
Dry-bottom wall-fired.........  Bituminous............              0.39
                                Sub-bituminous........              0.23
                                Lignite...............              0.29
Tangential-fired..............  Bituminous............              0.28
                                Sub-bituminous........              0.15
                                Lignite...............              0.17
Cell Burners..................  Bituminous............              0.40
                                Sub-bituminous........              0.45
Dry-turbo-fired...............  Bituminous............              0.32
                                Sub-bituminous........              0.23
Wet-bottom tangential-fired...  Bituminous............              0.62
------------------------------------------------------------------------

    Most EGUs can meet these presumptive NOX limits 
through the use of current combustion control technology, i.e. the 
careful control of combustion air and low-NOX burners. 
For units that cannot meet these limits using such technologies, you 
should consider whether advanced combustion control technologies 
such as rotating opposed fire air should be used to meet these 
limits.
---------------------------------------------------------------------------

    \19\ No Cell burners, dry-turbo-fired units, nor wet-bottom 
tangential-fired units burning lignite were identified as BART-
eligible, thus no presumptive limit was determined. Similarly, no 
wet-bottom tangential-fired units burning sub-bituminous were 
identified as BART-eligible.
    \20\ These limits reflect the design and technological 
assumptions discussed in the technical support document for 
NOX limits for these guidelines. See Technical Support 
Document for BART NOX Limits for Electric Generating Units and 
Technical Support Document for BART NOX Limits for Electric 
Generating Units Excel Spreadsheet, Memorandum to Docket OAR 2002-
0076, April 15, 2005.
---------------------------------------------------------------------------

    Because of the relatively high NOX emission rates of 
cyclone units, SCR is more cost-effective than the use of current 
combustion control technology for these units. The use of SCRs at 
cyclone units burning bituminous coal, sub-bituminous coal, and 
lignite should enable the units to cost-effectively meet 
NOX rates of 0.10 lbs/mmbtu. As a result, we are 
establishing a presumptive NOX limit of 0.10 lbs/mmbtu 
based on the use of SCR for coal-fired cyclone units greater than 
200 MW located at 750 MW power plants. As with the other presumptive 
limits established in this guideline, you may determine that an 
alternative level of control is appropriate based on your 
consideration of the relevant statutory factors. For other cyclone 
units, you should review the use of SCR and consider whether these 
post-combustion controls should be required as BART.
    For oil-fired and gas-fired EGUs larger than 200MW, we believe 
that installation of current combustion control technology to 
control NOX is generally highly cost-effective and should 
be considered in your determination of BART for these sources. Many 
such units can make significant reductions in NOX 
emissions which are highly cost-effective through the application of 
current combustion control technology.\21\
---------------------------------------------------------------------------

    \21\ See Technical Support Document for BART NOX Limits for 
Electric Generating Units and Technical Support Document for BART 
NOX  Limits for Electric Generating Units Excel Spreadsheet, 
Memorandum to Docket OAR 2002-0076, April 15, 2005.
---------------------------------------------------------------------------

V. Enforceable Limits/Compliance Date

    To complete the BART process, you must establish enforceable 
emission limits that reflect the BART requirements and require 
compliance within a given period of time. In particular, you must 
establish an enforceable emission limit for each subject emission 
unit at the source and for each pollutant subject to review that is 
emitted from the source. In addition, you must require compliance 
with the BART emission limitations no later than 5 years after EPA 
approves your regional haze SIP. If technological or economic 
limitations in the application of a measurement methodology to a 
particular emission unit make a conventional emissions limit 
infeasible, you may instead prescribe a design, equipment, work 
practice, operation standard, or combination of these types of 
standards. You should consider allowing sources to ``average'' 
emissions across any set of BART-eligible emission units within a 
fenceline, so long as the emission reductions from each pollutant 
being controlled for BART would be equal to those reductions that 
would be obtained by simply controlling each of the BART-eligible 
units that constitute BART-eligible source.
    You should ensure that any BART requirements are written in a 
way that clearly specifies the individual emission unit(s) subject 
to BART regulation. Because the BART requirements themselves are 
``applicable'' requirements of the CAA, they must be included as 
title V permit conditions according to the procedures established in 
40 CFR part 70 or 40 CFR part 71.
    Section 302(k) of the CAA requires emissions limits such as BART 
to be met on a continuous basis. Although this provision does not 
necessarily require the use of continuous emissions monitoring 
(CEMs), it is important that sources employ techniques that ensure 
compliance on a continuous basis. Monitoring requirements generally 
applicable to sources, including those that are subject to BART, are 
governed by other regulations. See, e.g., 40 CFR part 64 (compliance 
assurance monitoring); 40 CFR 70.6(a)(3) (periodic monitoring); 40 
CFR 70.6(c)(1) (sufficiency monitoring). Note also that while we do 
not believe that CEMs would necessarily be required for all BART 
sources, the vast majority of electric generating units potentially 
subject to BART already employ CEM technology for other programs, 
such as the acid rain program. In addition, emissions limits must be 
enforceable as a practical matter (contain appropriate averaging 
times, compliance verification procedures and recordkeeping 
requirements). In light of the above, the permit must:
     Be sufficient to show compliance or noncompliance 
(i.e., through monitoring times of operation, fuel input, or other 
indices of operating conditions and practices); and
     Specify a reasonable averaging time consistent with 
established reference methods, contain reference methods for 
determining compliance, and provide for adequate reporting and 
recordkeeping so that air quality agency personnel can determine the 
compliance status of the source; and
     For EGUS, specify an averaging time of a 30-day rolling 
average, and contain a definition of ``boiler operating day'' that 
is consistent with the definition in the proposed revisions to the 
NSPS for utility boilers in 40 CFR Part 60, subpart Da.\22\ You 
should consider a boiler operating day to be any 24-hour period 
between 12:00 midnight and the following midnight during which any 
fuel is combusted at any time at the steam generating unit. This 
would allow 30-day rolling average emission rates to be calculated 
consistently across sources.

    \22\ 70 FR 9705, February 28, 2005.
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[FR Doc. 05-12526 Filed 7-5-05; 8:45 am]
BILLING CODE 6560-50-P