
1
6560­
50­
P
ENVIRONMENTAL
PROTECTION
AGENCY
40
CFR
Part
51
[
FRL­
xxxx­
x]

RIN:
2060­
xxxxx
Regional
Haze
Regulations
and
Guidelines
for
Best
Available
Retrofit
Technology
(
BART)
Determinations
AGENCY:
Environmental
Protection
Agency
(
EPA).

ACTION:
Final
Rule.

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
2
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
[
insert
date
60
days
after
publication
in
the
Federal
Register].
3
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
Kaufman.
Kathy@
epa.
gov
or
Todd
Hawes
at
919­
541­
5591
or
by
e­
mail
Hawes.
Todd@
epa.
gov.

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.
4
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
to
the
Visibility
Regulations
D.
Changes
to
the
BART
Guidelines
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
5
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,
6
(
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),
to
require
the
use
of
Appendix
Y
in
establishing
BART
emission
limits,
and
(
5)
revised
regulatory
language
at
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
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
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
1
See,
e.
g.
CAA
Section
169A(
a)(
1).

7
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.

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
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.
8
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
"
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).
2
American
Corn
Growers
et
al.
v.
EPA,
291
F.
3d
1
(
2002).

9
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
for
States
to
use
in
identifying
their
BART­
eligible
sources,
in
identifying
which
of
those
sources
must
undergo
a
detailed
BART
analysis
(
i.
e.,
which
are
"
sources
subject
to
BART"),

and
in
conducting
the
technical
analyses
of
possible
controls
in
light
of
the
statutory
factors
listed
above
("
the
BART
determination").

American
Corn
Growers
v.
EPA
In
response
to
challenges
to
the
regional
haze
rule
by
various
petitioners,
the
D.
C.
Circuit
in
American
Corn
Growers2,
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.

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
3
CAA
Sections
169A(
b)(
2)
&
(
g)(
7).

10
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.

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
4
See
66
FR
35737­
35743
for
a
discussion
of
the
rationale
for
the
BART
requirements
in
the
1999
regional
haze
rule.

11
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
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.
While
rejecting
industry's
other
challenges,
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
12
held
that
the
method
that
we
had
prescribed
for
determining
which
eligible
sources
are
subject
to
BART
illegally
constrained
the
authority
Congress
had
conferred
on
the
States.
Id.
However,
the
court
expressly
declined
to
hold
that
the
general
collective
contribution
approach
to
determining
BART
applicability
was
necessarily
inconsistent
with
the
CAA,
were
it
not
for
the
infringement
on
State
authority.
Id.
at
9.
Rather,
the
court
stated
that
the
collective
contribution
approach
may
have
been
acceptable
if
EPA
had
allowed
for
a
State
exemption
process
based
on
an
individualized
contribution
determination.
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.

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
13
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.
3rd
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
processes
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
has
been
designed
to
address
the
holding
of
American
Corn
Growers
by
eliminating
the
previous
constraint
on
State
discretion,
as
explained
in
further
detail
in
sections
II.
D.
and
III
below.

2.
Consideration
of
Anticipated
Visibility
Improvements
in
BART
Determinations
14
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
would
be
accomplished
by
listing
the
visibility
improvement
factor
with
the
other
statutory
BART
determination
factors
in
section
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.

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,
No.
03­
1222,(
D.
C.
Cir.
Feb.
18,
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
169A(
b)(
2)
as
allowing
for
non­
BART
alternatives
where
those
alternatives
are
demonstrated
to
make
greater
progress
than
15
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)
required
that
visibility
improvements
under
source­
specific
BART
 
the
benchmark
for
comparison
to
the
alternative
program
 
must
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,
and
the
consequent
need
to
revise
§
308(
e)(
2),
we
are
removing
the
section
of
the
BART
guidelines
addressing
alternative
programs
from
today's
rulemaking.
We
remain
committed
to
providing
States
with
the
flexibility
to
address
BART
16
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.

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
SO2
and
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.
This
section
gives
a
brief
overview
of
the
relationship
between
BART
and
the
CAIR,
in
those
States
to
which
the
CAIR
applies.
For
a
more
thorough
discussion,
5
http://
www.
epa.
gov/
cair/
pdfs/
cair_
final_
preamble.
pdf.

6
"
Demonstration
that
CAIR
Satisfies
the
'
Better­
than­
BART'
Test
As
proposed
in
the
Guidelines
for
Making
BART
Determinations,"
at
http://
www.
epa.
gov/
cair/
pdfs/
finaltech04.
pdf.

17
see
section
IX.
C
of
the
CAIR
preamble5
and
the
associated
Technical
Support
Document.
6
In
the
CAIR
Notice
of
Proposed
Rulemaking
(
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
to
affected
EGUs.
(
See
69
FR
32684,
32702­
707,
June
10,
2004).

We
presented
emissions
and
air
quality
modeling
results
which
demonstrated
that
the
CAIR
would
achieve
greater
emission
reductions
and
greater
visibility
improvement
than
would
BART.
The
emissions
modeling
was
based
on
the
application
of
the
2004
proposed
presumptive
BART
control
levels
to
BART­
eligible
EGUs.
Using
this
modeling,
we
applied
the
proposed
test
(
also
contained
in
the
2004
proposed
BART
Guidelines)
for
determining
whether
a
trading
program
or
other
alternative
method
achieves
greater
reasonable
progress
than
BART
and
can
therefore
be
used
in
lieu
of
BART.
(
This
is
referred
to
in
shorthand
as
the
"
better
than
BART"
test.
In
brief,
the
test
requires
that
the
alternative
program
does
not
result
in
visibility
18
degradation
at
any
Class
I
area,
and
achieves
a
greater
overall
improvement
in
visibility,
on
average,
at
all
affected
Class
I
areas).

We
noted
that,
based
on
this
preliminary
analysis,
it
appeared
that
CAIR
would
pass
this
"
better
than
BART"
test
and
therefore
be
an
acceptable
alternative
to
BART
for
SO2
and
NOx
at
EGUs
in
affected
States.
However,
we
also
noted
that
because
the
emissions
scenarios
available
at
that
time
were
developed
for
other
purposes,
they
did
not
precisely
match
the
geographic
scope
of
CAIR
reductions
as
proposed,

and
did
not
account
for
the
fact
that
BART
would
continue
to
be
in
effect
outside
of
the
CAIR
region.
We
therefore
committed
to
refining
the
analysis
for
the
final
rule.

In
the
CAIR
Notice
of
Final
Rulemaking
(
NFR),
we
presented
and
discussed
that
refined
analysis.
The
analysis
was
improved
from
the
SNPR
version
by:
correcting
the
geographic
distribution
of
Nox
and
SO2
emission
reduction
requirements
to
reflect
those
contained
in
the
proposal;

increasing
the
number
of
Class
I
areas
represented
from
44
to
116;
adding
a
scenario
consisting
of
CAIR
reductions
in
the
CAIR­
affected
States
plus
BART­
reductions
in
the
remaining
States
(
excluding
Alaska
and
Hawaii);
and
improving
the
BART
control
assumptions
by
increasing
the
7
Specifically,
in
the
SNPR
analysis,
controls
were
"
required"
(
i.
e.,
assumed
by
the
model)
for
BART­
eligible
EGUs
greater
than
250
MW
capacity,
for
both
NOx
and
SO2.
In
the
NFR,
BART
controls
were
assumed
for
SO2
for
all
BARTeligible
EGU
units
greater
than
100
MW,
and
NOx
controls
for
all
BART­
eligible
EGU
units
greater
than
25
MW.

19
number
of
BART­
eligible
units
included.
7
As
in
the
SNPR,

the
analysis
examined
projected
improvements
on
both
the
20%

worst
(
most
impaired)
days
and
the
20%
best
(
least
impaired)

days.

This
updated
visibility
analysis
reaffirmed
that
under
the
proposed
two­
pronged
test,
CAIR
controls
are
"
better
than
BART"
for
EGUs.
The
modeling
predicts
that
the
CAIR
cap
and
trade
program
will
not
result
in
degradation
of
visibility
at
any
of
the
116
Class
I
areas
considered.
With
respect
to
the
proposed
requirement
for
greater­

averageimprovement
the
modeling
indicated
that
the
CAIR
emissions
reductions
in
the
east
produce
significantly
greater
visibility
improvements
than
source­
specific
BART.

Specifically,
for
the
29
eastern
Class
I
areas
analyzed,
the
average
visibility
improvement,
on
the
20
percent
worst
days,
expected
solely
as
a
result
of
the
CAIR
applied
in
the
East
and
BART
applied
in
the
West
is
1.6
dv,
as
compared
to
the
average
degree
of
improvement
predicted
for
nationwide
source­
specific
BART
of
0.7
dv.

Similarly,
on
a
national
basis,
the
visibility
modeling
showed
that
for
all
116
Class
I
areas
evaluated,
the
average
20
visibility
improvement,
on
the
20
percent
worst
days,
in
2015
was
0.5
dv
under
the
CAIR
cap
and
trade
program
in
the
east
and
BART
in
the
west,
but
only
0.2
deciviews
under
the
nationwide
source­
specific
BART
approach.

The
modeling
showed
similar
results
for
the
20
percent
best
visibility
days,
although
there
is
less
visibility
improvement
on
the
best
days
compared
to
the
worst
days.

For
the
29
eastern
Class
I
areas
analyzed,
the
average
visibility
improvement,
on
the
20
percent
best
days,

expected
solely
as
result
of
the
CAIR
applied
in
the
east
and
BART
applied
in
the
west
is
0.4
dv,
as
compared
to
the
average
degree
of
improvement
predicted
for
nationwide
source­
specific
BART
of
0.2
dv.
On
a
national
basis,
the
visibility
modeling
showed
that
for
all
116
class
I
areas
evaluated,
the
average
visibility
improvement,
on
the
20
percent
best
days,
in
2015
was
0.1
dv
under
both
the
CAIR
cap
and
trade
program
in
the
east
and
BART
in
the
west,
and
under
the
nationwide
source­
specific
BART
approach.

Despite
this
demonstration,
we
concluded
that
it
was
premature
to
make
a
final
determination
regarding
the
sufficiency
of
the
CAIR
as
a
BART
alternative,
primarily
because
(
1)
the
guidelines
for
source­
specific
BART
determinations
in
response
to
American
Corn
Growers
had
not
been
finalized,
and
(
2)
there
was
now
a
need
to
revise
the
Regional
Haze
Rule
and
the
guidelines
for
BART­
alternative
21
programs
in
response
to
the
recently
decided
case
of
CEED
v.

EPA.
We
noted
that
the
source­
specific
BART
guidelines
would
be
finalized
on
or
before
April
15,
2005,
and
that
further
rule
changes
controlling
BART­
alternative
programs
would
be
proposed
soon
thereafter,
in
order
to
revise
the
portions
of
the
regional
haze
rule
invalidated
by
CEED
v.

EPA.

Today's
action
finalizes
the
source
specific­
BART
guidelines
under
regional
haze
rule
section
308(
e)(
1).
We
remain
committed
to
conducting
a
separate
rule
making
in
the
near
future
to
revise
section
308(
e)(
2)
and
establish
criteria
for
determining
whether
alternative
programs
may
substitute
for
BART,
in
accordance
with
the
decision
in
CEED
v.
EPA.
As
we
also
noted
in
the
CAIR,
we
can
foresee
no
circumstances
under
which
BART
for
EGUs
could
produce
greater
visibility
improvement
than
the
CAIR,
but
we
must
continue
to
defer
a
final
determination
until
an
analysis
can
be
conducted
under
the
provisions
established
by
this
subsequent
rule
making.

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,
22
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.

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
BARTeligible
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
timeconsuming
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
8
64
FR
335740,
July
1,
1999.
The
regional
haze
rule
discusses
at
length
why
we
believe
that
States
should
draw
this
conclusion.
64
FR
35739­
40.

23
reasonably
be
anticipated
to
cause
or
contribute
to
any
visibility
impairment."
The
first
two
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."
8
States
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.

This
option
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]
9
CAA
§
169A(
b)(
2)(
A).

10
See
64
FR
35714,
35721.
See
also
July
29,
1997
memorandum
to
the
regional
haze
docket
A­
95­
38,
"
Supporting
24
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
to
force
States
to
conduct
individualized
analysis
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."
9
In
this
respect,
we
believe
that
it
is
important
to
note
that
the
court
in
American
Corn
Growers
expressly
declined
to
hold
that
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
would
be
consistent
with
the
CAA
and
the
findings
of
the
D.
C.
Circuit.

We
believe
there
is
ample
technical
evidence
supporting
a
finding
by
a
State
that
all
BART­
eligible
sources
within
the
State
are
subject
to
BART,
without
further
analysis
at
that
stage
in
the
process.
10
Any
Information
for
Proposed
Applicability
of
Regional
Haze
Regulations,"
by
Richard
Damberg,
EPA,
Office
of
Air
Quality
Planning
and
Standards.

25
potential
for
inequity
towards
sources
would
be
addressed
at
the
BART
determination
stage,
which
contains
an
individualized
consideration
of
a
source's
contribution
in
establishing
BART
emission
limits.

States
also
have
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
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
collectively
pose
a
measurable
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
26
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.
This
approach
is
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.

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.

States
may
also
choose
to
use
other,
less
resource­
intensive
methods
of
assessing
a
source's
individualized
contribution
to
regional
haze
visibility
impairment.

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
27
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
provide
a
way
for
States
to
take
into
account
the
degree
of
improvement
in
visibility
that
would
result
from
imposition
of
BART
on
each
individual
source.

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
nitrogen
oxides
(
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
EPA
approved
model
to
predict
visibility
impacts.
Scenarios
would
be
run
for
the
pre­
controlled
and
post­
controlled
emission
rates
for
each
of
the
BART
control
options
under
review.
The
maximum
hourly
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
28
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
29
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
30
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
31
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
32
reading
of
the
Act
indicates
that
Congress
intended
the
guidelines
to
be
mandatory
only
with
respect
to
750
megawatt
powerplants.
Thus,
while
we
agree
with
the
State
agency
comments
noting
the
strong
policy
reasons
in
support
of
covering
all
categories
in
order
to
establish
consistency
across
States
in
how
BART
determinations
are
made,
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
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
33
Section
II
of
the
BART
guidelines
contains
a
step­

bystep
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
emissin
units
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.
34
(
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.
35
Further,
the
comments
recommended
that
we
use
definitions
in
the
NSPS
for
primary
aluminum
plants
to
describe
the
BARTeligible
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
36
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
37
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
38
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,
the
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
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
39
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
40
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
BARTeligible
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
11
See
http://
www.
epa.
gov/
Region7/
programs/
artrd/
air/
nsr/
nsrmemos/
t
urbines.
pdf
41
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."
11
42
(
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.
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.
For
example,
43
pulp
and
paper
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
the
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
and
should
not
be
prematurely
ruled
out.

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
12
However,
sources
reconstructed
after
1977,
which
reconstruction
had
gone
through
NSR/
PSD
permitting,
would
not
be
BART­
eligible.

44
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.

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.
12
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
45
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.

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
46
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
47
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
13
See
CAA
section
193.

48
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.
13
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
49
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.

We
agree
with
commenters
that
the
definition
of
"

BARTeligible
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.

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
50
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.
51
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
52
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
BARTeligible
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
53
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:
sulfur
dioxide
(
SO2),
nitrogen
oxides
(
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
54
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
55
a
certain
time
frame.
The
regional
haze
rule
(
64
FR
3714,

July
1,
1999)
contains
definitions
that
are
relevant
to
the
determination
of
the
emissions
units
that
comprise
a
"
stationary
source."
First,
the
regulations
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
56
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
14
See
http://
wrapair.
org/
forums/
ioc/
meetings/
030728/
index.
html
57
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
concern14,
and
2003
direction
to
policy­
makers
from
the
(
specifically
presentation
by
John
Vimont,
National
Park
Service).

15
NARSTO
(
2004)
Particulate
Matter
Assessment
for
Policy
Makers:
A
NARSTO
Assessment.
P.
McMurry,
M.
Shepherd,
and
J.
Vickery,
eds.
Cambridge
University
Press,
Cambridge,
England.
ISBN
0
52
184287
5.

58
North
American
Research
Strategy
for
Tropospheric
Ozone
(
NARSTO)
15
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.

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
visibilityreducing
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
59
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.
The
guideline
continues
to
recommend
that
States
use
PM10
as
the
indicator
for
particulate
matter
for
the
applicability
step,
i.
e.
in
determining
whether
a
source
is
BART­
eligible.
We
disagree
with
comments
that
the
coarse
fraction
of
PM
does
not
contribute
to
visibility
impairment;
wWhile
it
is
always
necessary
to
assess
PM2.5
impacts,
we
agree
with
commenters
16
See
Fine
particles:
Overview
of
Atmospheric
Chemistry,
Sources
of
Emissions,
and
Ambient
Monitoring
Data,
Memorandum
to
Docket
OAR
2002­
0076,
April
1,
2005.

17
These
methods
are
described
at
the
following
website:
http://
vista.
cira.
colostate.
edu/
improve/
Tools/
ReconBext/
reco
nBext.
htm
.

18
Grand
Canyon
Visibility
Transport
Commission,
Recommendations
for
Improving
Western
Vistas,
Report
to
the
U.
S.
EPA,
June
10,
1996.

60
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.
16
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.
17
We
do
recognize
that
coarse
PM
is
likely
to
contribute
more
to
regional
haze
in
arid
areas
than
humid
areas.
Thus,
wWe
believe
that,
as
the
Grand
Canyon
Visibility
Transport
Commission
(
GCTVC)
recognized,
18
States
in
the
arid
West,
in
particular,
shouldwill
need
to
take
the
coarse
fraction
of
particulate
matter
into
account
in
determining
whether
a
source
meets
the
threshold
for
BART
applicability.
More
humid
Eastern
states
may
not
need
to
account
for
the
coarse
fraction
for
purposes
of
regional
haze.

However,
bBecause
long­
range
transport
of
fine
particles
is
of
particular
concern
in
the
formation
of
61
regional
haze,
we
also
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).

The
acceptability
of
existing
stationary
source
test
methods
for
regional
haze
SIPs
depends
upon
what
is
measured
under
your
current
test
methods
for
particulate
matter.

YourStates
will
need
to
take
care
to
consider
whether
their
current
test
methods
for
measuring
particulate
matter
emissions
from
stationary
sources
may
not
be
acceptable
for
regional
haze
SIP
purposes
if
these
methods
ignore
account
for
the
condensible
fraction
of
particulate
matter,
and
consider
revising.
More
specifically,
for
purposed
of
makig
a
BART
determination,
a
test
method
that
ignores
a
significant
fraction
of
emissions
may
artificially
limit
the
control
measures
considered
in
the
BART
analysis.
Therefore
you
should
revise
any
such
stationary
source
test
methods
to
ensure
that
you
account
for
the
condensible
fraction
of
particulate
emissions.
See
the
source
testing
technical
support
document
(
TSD)
in
the
docket
for
this
rule,
which
19
Fine
particles:
Overview
of
Source
Testing
Approaches,
Memorandum
to
Docket
OAR
2002­
0076,
April
1,
2005.

20
See
Fine
particles:
Overview
of
Atmospheric
Chemistry,
Sources
of
Emissions,
and
Ambient
Monitoring
Data,
Memorandum
to
Docket
OAR
2002­
0076,
April
1,
2005.

62
discusses
test
methods
for
particulate
matter
in
more
detail.
19
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
ample
scientific
data
illustrating
that
ammonia
in
the
atmosphere
can
be
a
precursor
to
the
formation
of
particles
such
as
ammonium
sulfate
and
ammonium
nitrate;
20
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
does
contribute
to
visibility
impairment
in
a
specific
instance
can
be
a
difficult
one.

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
63
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
BARTeligible
Thus,
while
we
believe
ammonia
can
contribute
to
visibility
impairment,
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
will
be
left
up
to
the
State
to
make
a
reasoned
determination.

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.
21
Ibid.

64
Current
scientific
and
technical
information
clearly
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.
21
However,
while
significant
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.

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
22
Ibid.

65
state
of
knowledge
in
this
area
is
complex
and
rapidly
evolving.
Monitoring
data
in
the
East22
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.

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
court
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
66
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
§
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
BARTeligible

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
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
67
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
emissions
limitations
in
State
permits,
which
are
enforceable
under
State
law,
in
determining
a
source's
"
potential
to
emit."
As
we
have
not
yet
undertaken
such
a
rulemaking,
the
guidelines
continue
to
refer
to
the
existing
regulatory
definition
of
"
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
68
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
BARTeligibility
69
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.
We
have
added
language
to
the
guidelines,
at
the
BART
determination
step,
encouraging
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.

Step
4:
Identify
the
emission
units
and
pollutants
that
constitute
the
BART­
eligible
source.

Background.
The
final
step
in
identifying
a
"

BARTeligible
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
visibilityimpairing
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
visibilityimpairing
pollutant
emitted
from
this
collection
of
emissions
units.
70
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"

visibilityimpairing
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
71
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
72
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
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
at
least
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
of
contribute
to
any
impairment
of
visibility"
in
any
of
the
Class
I
areas
covered
by
the
73
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
distinction
between
these
two
interpretations
of
this
provision
is
unlikely
to
be
significant
in
practice,
however,
as
one
of
the
factors
to
be
taken
into
account
in
making
a
BART
74
determination
is
the
degree
of
visibility
improvement
resulting
from
the
use
of
controls.

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
should
be
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
75
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
costeffective
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
23
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).

76
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.'"
23
The
ability
to
create
de
minimis
exemptions
24
Id.

77
from
a
statute
is
a
tool
to
be
used
in
implementing
the
legislative
design.
24
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.

Although
as
discussed
above,
it
is
not
possible
based
on
the
information
before
us
to
assume
that
emissions
of
250
tons
per
year
of
a
visibility­
impairing
pollutant
do
not
cause
or
contribute
to
visibility
impairment,
we
do
believe
it
would
be
permissible
for
States
to
create
de
minimis
levels
at
a
much
lower
level.
If
a
State
were
to
undertake
78
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
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
allow
the
States
this
flexibility.

The
de
minimis
levels
we
provide
for
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
costeffective
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.
79
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.
States
can
accordingly
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
are
suggesting
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.
84
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
85
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
86
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
87
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
BARTeligible
sources,
several
commenters
stated
that
the
third
option
contained
burdensome
modeling
requirements,
and
that
States
need
a
more
flexible,
straightforward,
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
25
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.

88
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.
25
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
89
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.

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.
90
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).
26
Grand
Canyon
Visibility
Transport
Commission,
Recommendations
for
Improving
Western
Vistas,
Report
to
the
U.
S.
EPA,
June
10,
1996.

91
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,
26
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.

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
92
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
those
small
sources
that
cannot
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
27
[
insert
reference
to
Mark's
docket
memo]

93
emissions,
stack
heights
and
plume
characteristics,
and
develop
"
composite
model
plants."
Based
on
CALPUFF
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
cannot
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
of
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.
27
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
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
combined
Nox
and
SO2
that
are
located
more
than
100
kilometers
from
any
Class
I
area.

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
94
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
BARTeligible
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
28
Reference
modeling
TSD
95
being
modeled.
28
A
summary
of
the
more
significant
elements
and
their
implications
is
provided
below.

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
96
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.

Although
the
results
of
our
model
plant
may
be
useful
in
assessing
the
likely
impacts
of
similarly
configured
sources,

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
29
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.

97
State.
A
State
with
a
sufficiently
large
number
of
BART­
eligible
sources
could
also
make
such
a
showing
using
a
photochemical
grid
model.
29
We
agree
with
commenters
who
pointed
out
that
the
option
of
allowing
a
State
to
demonstrate
that
the
full
group
of
BARTeligible
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
30
Guidance
for
Estimating
Natural
Visibility
Conditions
Under
the
Regional
Haze
Rule
(
U.
S.
EPA.
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.

31
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,
p.
24­
D2
("
changes
in
light
extinction
of
5%
will
evoke
a
just
noticeable
change
in
most
landscapes").
Converting
a
5%
change
in
light
extinction
to
a
change
in
deciviews
yields
a
change
of
approximately
0.5
deciviews.

98
an
individual
source
could
be
considered
to
cause
visibility
impairment
in
a
Class
I
area.
We
proposed
a
0.5
deciview
change
(
delta­
deciview),
relative
to
natural
background
conditions30,
as
a
numerical
threshold
for
making
this
determination.
We
noted
that
a
0.5
deciview
change
in
visibility
is
linked
to
"
perceptibility,"
or
a
just
noticeable
change
in
most
landscapes.
31
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
32
Ibid.

33
Henry,
R.
C.
"
Just­
Noticeable
Differences
in
Atmospheric
Haze",
Journal
of
the
Air
&
Waste
Management
Association,
52:
1238­
1243,
October
2002.

99
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.
32
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
deciview33.

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
100
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
BARTeligible
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.
101
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
34
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.

105
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.
34
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.

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
35
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
(
0.5
deciviews
or
lower).

106
to
"
cause"
visibility
impairment,
and
a
change
of
0.5
deciviews
to
"
contribute"
to
impairment.
35
In
a
regulatory
context,
we
believe
that
a
State's
decision
as
to
an
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
for
two
reasons.
First,

studies
suggest
that
0.5
deciviews
represents
a
level
of
visibility
impairment
which
can
be
perceived
in
some
but
not
all
situations.
A
source
whose
emissions
are
predicted
to
result
in
36
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.

107
perceptible
or
nearly
perceptible
results
should
clearly
be
considered
to
contribute
to
impairment.
Second,
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.
36
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
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.
108
We
would
note
that
under
this
guidance,
States
would
have
discretion
in
setting
the
threshold
for
"
contributes
to"
based
on
modeled
impacts
of
sources.
Consistent
with
the
American
Corn
Growers
decision,
we
are
not
requiring
States
to
find
sources
subject
to
BART
regardless
of
their
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
109
roughly
the
same
degree
of
change
of
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
110
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.
For
two
reasons,
however,
we
have
concluded
that
the
98th
percentile
is
appropriate
in
this
case.

First,
Congress
established
a
very
low
threshold
for
determining
whether
a
source
should
be
subject
to
BART
review
 
whether
it
"
may
reasonably
be
anticipated
to
contribute
to
any
impairment
of
visibility."
The
use
of
90th
percentile
value
would
effectively
disregard
visibility
effects
that
are
predicted
to
occur
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.

We
recognize
that
the
use
of
the
98th
percentile
of
modeled
visibility
values
would
appear
to
disregard
as
many
as
7
days
per
year
from
consideration.
On
the
other
hand,
there
are
other
features
of
our
recommended
modeling
approach
that
are
likely
to
111
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.
In
our
judgement,
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
uncertain
assumptions
in
the
model.

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
37
H.
R.
Rep.
No.
95­
294
at
204
(
1077).

112
particle
precursors,
such
as
SO2
or
NOx,
are
dispersed,
they
react
in
the
atmosphere
with
other
pollutants
to
form
visibilityimpairing
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."
37
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.

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
38
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.

39
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.

113
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.
38
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
PLUVUEII39,
to
determine
whether
a
source's
emissions
are
below
a
level
that
would
be
reasonably
anticipated
114
to
cause
or
contribute
to
visibility
impairment
in
any
Class
I
area.

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
40
The
model
code
and
its
documentation
are
available
at
no
cost
for
download
from
http://
www.
epa.
gov/
scram001/
tt22.
htm#
calpuff.

115
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
purposes40.

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
116
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
BARTeligible
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
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
41
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.

117
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
(
40
CFR
Part
51,
Appendix
W,
April
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.
41
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
42
CALPUFF
Analysis
in
Support
of
the
Regional
Haze
Rule,
U.
S.
Environmental
Protection
Agency,
April
15,
2005,
Docket
No.
OAR­
2002­
0076.

43
Ibid.

118
determination
that
it
would
not
be
appropriate
in
the
rulemaking
revising
Appendix
W
to
approve
CALPUFF
for
use
in
modeling
secondary
emissions.

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.
42
In
fact,
we
anticipate
that
most
of
these
plants
are
predicted
to
have
much
higher
maximum
impacts.
43
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
low
triggering
threshold
in
the
Act
does
not
119
require
the
degree
of
certainty
in
the
results
of
the
model
that
might
be
required
for
other
regulatory
purposes.

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
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
best
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
120
each
factor.
American
Corn
Growers
v.
EPA
[
cite
to
dissent,
fn.

10].
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
individualized
showings
that
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
44For
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.

121
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
and
such
use
has
been
approved
by
the
appropriate
EPA
regional
offices.
However,

to
date,
regional
models
have
not
been
evaluated
for
single
source
applications.
Their
use
may
be
more
appropriate
in
the
cumulative
modeling
options
Options
1
and
2
discussed
above44.
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
in
Appendix
W,
section
3.2.

The
Use
of
Natural
Conditions
in
Determining
Visibility
Impacts
for
Reasonable
Progress
and
Comparison
to
Threshold
values
45
Guidance
for
Estimating
Natural
Visibility
Conditions
Under
the
Regional
Haze
Rule
(
U.
S.
EPA.
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.

122
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
implement
the
CAA
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.
45
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.

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
123
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,

realworld
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
124
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%
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
46
See
also
our
explanation
of
the
CAA
goal
provided
in
the
regional
haze
rule
at
64
FR
126.

125
visibility
conditions.
46
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.

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".
Congress
used
sweeping
terms
(
cause
or
contribute
to
any
impairment
at
any
Class
I
area)
to
describe
the
low
triggering
threshold
for
BART
review.
Using
existing
conditions
as
the
baseline
for
single
source
visibility
impact
determinations
would
be
fundamentally
at
odds
with
the
low
triggering
threshold
for
BART
review,
because
it
would
create
the
following
untenable
paradox:
the
dirtier
the
existing
air,
the
less
likely
it
would
be
that
any
control
is
required
from
any
one
source.
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
126
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.

We
also
believe
that
using
existing
visibility
conditions
rather
than
natural
background
conditions
as
the
reference
point
for
determining
whether
a
BART­
eligible
source
is
subject
to
BART
would
be
inconsistent
with
the
analytical
framework
suggested
by
the
American
Corn
Growers
decision.
In
that
decision,
the
D.
C.

Circuit
held
that
EPA
may
not
require
states,
in
the
course
of
determining
whether
a
BART
eligible
source
is
subject
to
BART
(
or
in
the
course
of
evaluating
visibility
improvements
as
one
of
the
five
factors
for
determining
what
BART
is)
to
also
consider
visibility
improvement
from
the
application
of
controls
to
all
other
BART
eligible
sources.
In
other
words,
the
court
held
that
visibility
benefits
of
controlling
emissions
from
the
source
in
question
should
be
considered
in
isolation,
without
regard
to
the
potential
benefits
from
reducing
emission
at
other
BART­
eligible
units.
If
the
benefits
of
controlling
emissions
from
other
sources
are
not
to
be
considered
in
determining
BART,
neither
47
Guidance
for
Estimating
Natural
Visibility
Conditions
Under
the
Regional
Haze
Rule
(
U.
S.
EPA.
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.

127
should
the
detrimental
affects
of
emissions
from
other
sources
be
allowed
to
mask
the
potential
benefits
from
controlling
emissions
at
the
source
in
question.
Otherwise,
a
skewed
framework
is
created,
in
which
the
State
could
never
require
BART
at
any
source,
because
by
artificially
assuming
that
no
other
reductions
would
occur
elsewhere,
it
would
become
impossible
to
show
that
controlling
any
one
source
would
produce
benefits.
The
most
equitable
way
to
escape
this
conundrum
is
to
evaluate
each
source's
impact
without
regard
to
other
sources
 
in
other
words,

as
it
would
be
against
natural
background
conditions.

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
guidance47,
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
128
visibility
baseline
for
the
20%
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.

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,

sourcespecific
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.
129
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
48Interagency
Workgroup
on
Air
Quality
Modelig
(
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.

130
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
Impacts48,
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
131
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.

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
132
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
a
modeling
protocols
should
be
required
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
proposal,
we
believe
that
potential
uncertainties
in
model
performance
may
be
greater
at
distances
greater
than
200
km
for
a
source.
However,
a
mechanism
(
i.
e.
a
modeling
protocol)
is
needed
in
all
modeling
situations
to
ensure
that
the
model
and
the
BART
exemption
test
are
applied
consistently
and
equitably
across
BART­
eligible
sources
nationwide.
A
modeling
protocol
for
all
cases
will
ensure
agreement
on
the
databases
used,
and
the
modeling
techniques
and
the
overall
technical
approach
used
prior
to
the
actual
analyses.
Thus,
misunderstandings
concerning
model
results
will
be
mitigated,
and
this
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
of
the
model.
Such
coordination
may
relieve
the
administrative
burden
of
examining
and
approving
a
protocol
for
each
separate
BART­
eligible
source.
A
protocol
developed
by
and
acceptable
to
all
stakeholders
would
expedite
the
modeling
process
and
further
ensure
nationwide
consistency
in
application
of
the
model.
133
Coordinated
efforts
could
help
develop
standardized
data
sets
to
provide
the
added
benefit
of
reducing
the
cost
and
time
needed
for
a
modeling
analysis
and
facilitating
comparability
between
individual
analyses.
A
centralized
regional
database,
accessible
on
a
web
site,
may
provide
quality­
assured
upper
air,
surface,

precipitation,
monitoring,
land
use,
and
terrain
data
already
in
model­
ready
format.
Some
of
the
RPOs,
for
instance,
have
developed
data
sets
for
model
inputs
that
can
be
used
by
States,

further
reducing
time
and
cost
constraints
while
standardizing
the
model
input
requirements.
The
use
of
predefined
receptor
networks
developed
by
the
FLMs
can
also
relieve
resource
constraints.

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
a
modeling
protocol
should
provide
flexibility
to
States
for
setting
up
and
running
the
model,
as
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.
49
http://
www.
src.
com/
calpuff/
calpuff1.
htm.

134
For
example,
in
a
particular
area
a
State
may
have
available
ammoniaemissions
data,
that
is
more
representative
of
the
modeling
domain,
which
may
supplement
the
model
defaults.
States
should
work
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
website49
also
has
a
series
of
frequently
asked
questions
with
answers
to
assist
users
in
tailoring
model
applications.

We
agree
that
we
should
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).

We
believe,
however,
that
EPA
should
have
final
approval
of
State
protocols
so
that
the
model,
and
the
BART
control
decision
which
depends,
in
part,
on
the
model
results,
is
applied
equitably
across
all
regions.
EPA
approval
will
help
ensure
that
vastly
different
modeling
results
are
not
produced
for
modeled
BARTeligible
sources
that
have
similar
emission
configurations
and
operate
under
comparable
geophysical
and
meteorological
conditions.
50Analysis
in
Support
of
Changes
to
the
Regional
Haze
Rule,
U.
S.
Environmental
Protection
Agency,
April
15,
2005,
Docket
No.
OAR­
2002­
0076.

135
In
the
protocol
approval
process,
we
support
the
idea
of
designing
example
runs,
as
we
have
done
in
our
example
analysis
for
EGUs50,
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
approved,
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.

As
models
are
revised
and
advances
in
science
are
incorporated
into
the
models,
we
can
make
certain
that
revisions
136
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
and
approval
process.
We
expect
a
similar
protocol
development
and
approval
process
for
other
models
that
may
be
used,
once
those
models
are
developed
to
predict
and
track
single
source
impacts,

demonstrate
acceptable
model
performance,
and
are
approved
by
us
for
use.
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
51
CALPUFF
Analysis
in
Support
of
the
Regional
Haze
Rule,
U.
S.
Environmental
Protection
Agency,
April
15,
2005,
Docket
No.
OAR­
2002­
0076.

137
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
approach51.
While
we
are
not
adopting
in
the
guideline
any
specific
alternative
to
modeling
for
large
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
138
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.

E.
The
BART
Determination
Prcess
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
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
stepby
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?
139
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
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
continue
to
believe
that
States
need
not
consider
technologies
to
be
"
commericially
available"
if
they
are
only
in
the
pilot
test
phase
as
of
the
date
the
State
conducts
its
public
comment
period.
We
140
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.
What
is
meant
by
"
ranking
of
all
technically
feasible
control
options"
in
step
2
of
the
BART
determination?

Comments.
The
comments
on
this
section
of
the
guidelines,
as
proposed
in
2001
and
reproposed
in
2004,
generally
were
directed
at
issues
related
to
sources
emitting
more
than
one
pollutant.

While
our
proposed
guidelines
call
for
a
separate
ranking
for
each
pollutant,
a
number
of
comments
suggested
approaches
for
considering
combinations
of
pollutants
in
developing
a
ranking
of
control
measures.
Some
comments
recommended
that
the
guidelines
consider
control
measures
favorably
if
the
total
visibility
impairing
pollutant
reduction
is
greater
than
for
a
technology
reducing
emissions
of
only
one
pollutant.
Other
comments
suggested
developing
a
weighting
approach.
In
this
approach,
a
method
would
be
developed
under
which
emissions
of
pollutants
with
greater
contributions
to
light
extinction
would
be
given
a
greater
weight
than
emissions
of
other
pollutants.

Final
rule.
We
agree
with
comments
that
there
could
be
situations
where
the
control
technology
selected
as
BART
could
involve
judgments
on
controls
for
a
combination
of
pollutants.

Nonetheless,
we
continue
to
believe
that
the
most
practical
approach
to
taking
this
into
account
as
a
general
matter
is
to
begin
with
a
separate
ranking
for
each
pollutant.
We
do
not
141
believe
that
it
would
be
feasible
to
develop
a
weighted
ranking
system
given
the
regional
differences
in
contributions
to
extinction
from
various
constituents.
As
noted
above,
however,

States
may
find
that
it
is
appropriate
to
place
greater
overall
emphasis
on
controlling
emissions
of
direct
PM,
SO2,
and
NOx
than
on
controlling
emissions
of
VOCs
and
ammonia.

32.
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
Air
Pollution
Control
Cost
Manual
(
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
minor
changes
to
how
it
was
proposed.
We
believe
that
the
Control
Cost
Manual
provides
a
good
reference
tool
for
cost
calculations
and
it
serves
to
provide
for
consistency.
If
142
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
to
that
available
from
using
the
methods
in
the
Control
Cost
Manual.

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
143
individual
units
in
order
to
respond
to
SIP
requirements
in
an
efficient
manner
(
from
the
State's
perspective).
This
also
mirrors
how
we
used
cost
information
in
setting
the
presumptive
limits
for
EGUs
described
earlier.

43.
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.
144
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
and
that
the
effects
of
remaining
useful
life
on
costs
may
not
be
disregarded.
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.

54.
How
should
"
visibility
impacts"
be
considered
in
step
5
of
the
BART
determination?

Background.
The
fifth
statutory
factor
addresses
the
degree
of
improvement
in
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
EPAapproved
model,
to
estimate,
in
deciviews,
a
BART
source's
145
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
146
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
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
147
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
148
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%
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
149
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
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
52
Pitchford,
M.
and
Malm,
W.,
"
Development
and
Applications
of
a
Standard
Visual
Index,"
Atmospheric
150
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)
52
and
Henry
Environment,
V.
28,
no.
5,
March
1994.

53
Henry,
R.
C.
"
Just­
Noticeable
Differences
in
Atmospheric
Haze",
Journal
of
the
Air
&
Waste
Management
Association,
52:
1238­
1243,
October
2002.

151
(
2002)
53
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.

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
costeffectiveness
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
152
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
(
i.
e.
the
expected
improvement
may
be
less
than
or
equal
to
0.5
deciviews),
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

thanperceptible
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.

We
disagree
that
actual
emission
rates
should
be
used
to
predict
visibility
impacts.
A
source
may
be
operating
at
its
full
permitted
level
at
any
time,
and
visibility
impairment
is
appropriately
measured
against
that
allowable
emission
rate
(
hourly),
as
visitors
may
experience
visibility
in
Class
I
areas
at
any
time.
Although
we
are
not
requiring
States
to
use
allowable
emission
rates
to
predict
the
anticipated
future
153
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
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.
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
worst
24­

hour
average
actual
emission
rate,
for
the
most
recent
three
or
five
year
period
of
meteorological
data,
to
characterize
the
maximum
potential
benefit.

We
do
not
believe
that
using
the
maximum
24­
hour
average
over
the
meteorological
period
modeled
(
three
or
five
years)
is
too
restrictive
in
determining
if
a
BART­
eligible
source
is
subject
to
a
BART
review,
or
for
evaluating
the
degree
of
visibility
improvement
expected
from
BART
reductions.
A
scenic
vista
is
observed
instantaneously,
which
may
suggest
an
even
shorter
averaging
time
for
estimating
impairment;
models,
however,
must
154
account
for
chemical
transformations
and
long
range
transport
which
occur
over
time.
A
24­
hour
averaging
time
may
be
the
most
practical
way
to
simulate
chemical
and
physical
processes,
but
we
do
agree
that
averaging
times
of
even
1
hour
have
merit.
[
insert
information
regarding
modeling
meteorology]
In
response
to
the
comment
about
reliance
on
monitoring
rather
than
modeling
receptors,
a
monitoring
site
may
not
coincide
with
the
location
of
the
maximum
modeled
impact
in
a
Class
I
area.
Consequently,
we
believe
that
sole
reliance
on
monitored
data
to
assess
maximum
visibility
impacts
is
not
appropriate.
In
addition,
monitoring
data
may
not
be
useful
for
predicting
future
visibility
impacts.

We
agree
with
commenters
that
the
difference
between
the
preand
post­
control
scenarios
on
the
average
of
the
20
percent
worst
modeled
days
may
not
be
the
best
approach
in
determining
visibility
improvement.
The
importance
of
an
average
as
a
data
point
can
depend
on
the
variation
in
the
data
as
a
whole.
In
other
words,
there
may
be
a
few
days
of
very
high
impairment
in
a
Class
I
area,
but
many
days
of
lower
impairment.
The
average
would
tend
towards
the
lower
values,
but
that
is
not
meaningful
to
an
observer
that
may
be
experiencing
impairment
on
one
of
the
worst
days.
Also,
average
visibility
is
considered
uniformly
across
the
Class
I
area,
and
in
this
context,
it
is
an
average
due
to
the
pollutant
contributions
of
all
sources
around
the
Class
I
area
(
not
the
average
due
just
to
one
source,
and
the
average
of
the
20%
worst
modeled
days
would
be
of
minimal
value).

Because
each
Class
I
area
is
unique,
we
believe
States
should
have
155
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.
Although
the
analysis
using
the
20
percent
average
worst
modeled
days
(
pre­
and
post­
control)
may
not
capture
the
data
maxima,
its
use
may
be
reasonable
in
evaluating
the
fifth
factor
as
part
of
its
BART
determination.
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
is
not
necessarily
based
on
a
one­
time
test
for
a
maximum
24­
hour
impact.

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.
components
of
impairment
when
making
the
visibility
improvement
determination;
both
"
average"
and
"
peak"
tests
are
crucial
in
making
the
assessment.

We
agree
with
the
suggestion
that
the
use
of
a
comparison
threshold,
as
is
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
should
have
flexibility
in
setting
absolute
thresholds,
54CALPUFF
Analysis
in
Support
of
the
Regional
Haze
Rule,
U.
S.
Environmental
Protection
Agency,
April
15,
2005,
Docket
No.
OAR­
2002­
0076.

55
Ibid.

156
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
deciview
improvement
may
merit
a
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
source54,
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)
55.

Other
ways
that
visibility
improvement
may
be
assessed
to
inform
the
control
decisions
would
be
to
examine
distributions
of
157
the
hourly
or
daily
impacts,
compare
the
hourly
values
to
thresholds,
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.

65.
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,
which
was
the
preferred
approach,
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
158
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
and
rank
all
of
the
options
in
order
of
control
effectiveness
and
to
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
as
to
the
basis
for
rejecting
the
other
more
stringent
control
technologies
identified
in
the
BART
determination
were
rejected.
159
In
selecting
a
"
best"
alternative,
the
proposed
guidelines
included
a
discussion
on
whether
the
affordability
of
controls
should
be
considered.
We
noted
in
the
guidelines
that,
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,
EPA
is
unlikely
to
accept
as
BART
any
analysis
that
preserves
a
source's
uncontrolled
status.

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

bycase
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
160
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
noted
decided
that
States
should
retain
the
discretion
to
evaluate
control
options
in
whatever
order
they
choose,
so
long
as
the
State
fully
documents
its
analysis
of
the
CAA
factors.
If
it
chooses
a
control
alternative
other
than
the
"
best"
emissions
control,
it
should
document
its
justification,
based
on
the
factors,
for
not
choosing
each
available
more
stringent
option.
We
do
not
agree
with
commenters
who
asserted
that
the
method
for
assessing
BART
controls
for
existing
sources
should
consider
all
of
the
statutory
161
factors.
must
differ
from
the
method
of
assessing
controls
for
new
sources;
so
long
as
the
factors
are
analyzed
properly,
there
is
no
inherent
need
for
a
different
process.

7.
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
162
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.
163
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
164
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
or
greater
SO2
removal,
or
an
emission
rate
of
0.15
lb
SO2/
mmBtu
or
lower,
unless
a
State
determines
that
an
alternative
control
level
is
justified
based
on
a
careful
consideratino
of
the
statutory
factors.
For
NOx,
we
are
establishing
a
set
of
BART
presumptive
emission
limits
for
coalfired
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
165
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.
evidence
before
it.
Our
intent
is
that
a
State
will
face
a
high
hurdle
if
it
chooses
to
justify
a
BART
determination
less
than
these
requirements
for
a
power
plant
greater
than
750
MW
in
size.

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.

evidence
before
it.
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
visibility
impact
and
56Summary
of
Technical
Analyses
for
the
Proposed
Rule,
Mark
Evangelista,
U.
S.
Environmental
Protection
Agency,
April
12,
2004,
Docket
No.
OAR­
2002­
0076.

166
cost­
effectiveness
analyses
we
have
performed
since
proposal
of
the
guidelines
in
2004.

g.
Visibility
Analysis
for
SO2
and
NOx
emissions
from
EGUs
In
the
2004
reproposal,
our
preliminary
CALPUFF
modeling56
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.

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
57
CALPUFF
Analysis
in
Support
of
the
Regional
Haze
Rule,
U.
S.
Environmental
Protection
Agency,
April
15,
2005,
Docket
No.
OAR­
2002­
0076.

58
Reference
Mark's
new
TSD
167
than
a
change
of
2
or
3
deciviews57.
Our
modeling
examples58
included
scenarios
that
were
was
representative
of
a
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.
Such
levels
of
emissions
are
well
below
those
that
may
be
expected
of
an
uncontrolled
200
MW
EGU.
Not
only
were
the
maxima
considerable,
but
tThe
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
50km
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.

substantial.
Furthermore,
when
this
same
source
was
modeled
with
SO2
emissions
of
1,000
TPY
(
which
is
a
reduction
of
90
percent
­

see
run
#
5),
the
source
was
still
a
significant
contributor
to
visibility
impairment,
even
though
maximum
visibility
was
very
much
improved.

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
168
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,
after
submitting
an
approved
modeling
protocol,
that
it
should
not
be
subject
to
BART
(
based
on
its
visibility
effectsimpacts).
Based
on
our
modeling
results,
we
believe
that
such
a
showing
would
be
extremely
difficult
for
these
large
EGUs.

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
750MW,
we
are
establishing
a
presumptive
BART
limits
of
95
percent
or
greater
SO2
removal,
or
an
emission
rate
of
0.15
lb
SO2/
mmBtu
or
lower.
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
costeffective
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
59
Technical
Support
Document
for
BART
SO2
Limits
for
Electric
Generating
Units,
Memorandum
to
Docket
OAR
2002­
0076,
April
1,
2005.

169
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.
59
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
uniqueextreme
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%
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
60
Ibid.

61
PQA
Analysis
170
and
EGUs
burning
low
sulfur
or
lignite
coals
achieving
these
SO2
limits
at
reasonable
cost.
60
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
ton61.

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%,
not
all
units
can
do
so.
The
individual
units
that
currently
achieve
greater
than
95%
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
62
Ibid.

171
consider
whether
more
(
or
less)
stringenta
different
level
of
controls
are
is
appropriate
in
a
particular
case.
If,
upon
closer
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
existing
SO2
controls,
and
(
2)

coalfired
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.
62
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
63
Ibid.

172
historical
Acid
Rain
emissions
data.
Our
analysis
is
described
in
detail
in
the
TSD.
63
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.

Unit
Capacity
(
MW)
Tons
(
K)
of
SO2
Emitted
in
2001
%
of
BART
Eligible
Coal­
fired
Unit's
2001
Emissions
Calculated
Average
Cost
Effectiveness
for
MW
Grouping
($/
ton
SO2
removed)
%
of
Estimated
Removable
BART
SO2
Emissions
From
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%
173
All
Units
6707
100%
984
100%

BART
Units
(>
200MW)
6246
92.2%
919
91.9%

Figure
1.

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
strongly
encourage
recommend
States
to
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
174
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
suit
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
oilfired
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
175
limitation.
Of
the
74
BART­
eligible
oil­
burning
EGUs,
32
currently
have
sulfur
fuel
oil
restrictions
of
less
than
1%,
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
1
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
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).
176
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.

(
No
commenters
took
issue
with
the
idea
of
running
existing
SCRs
or
SNCRs
year­
round.
Some
commenters
supported
year­
round
operation
of
these
controls.)
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
64
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.

177
units64
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.

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.
178
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.

Boiler
Type
Number
Number
Number
All
units
Units
>
200
MW
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
coalfired
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
65
The
current
combustion
control
technology
EPA
analyzed
for
cyclone
units
is
coal
reburning.

179
cost­
effective
than
current
combustion
control
technology;
65
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.

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,
and
expect
that
for
many
EGUs,
States
will
establish
BART
limits
at
least
as
stringent
as
these.
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
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,
66
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
wetbottom
units
burning
sub­
bituminous
were
identified
as
BARTeligible

67
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.

180
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.

Table
2.
Presumptive
NOx
emission
limits
for
BART­
eligible
coal­
fired
units66
Unit
type
Coal
type
NOx
presumptive
limit
(
lb/
mmbtu)
67
Dry­
bottom
wallfired
Bituminous
0.39
Sub­
bituminous
0.23
Lignite
0.29
Tangential­
fired
Bituminous
0.28
181
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
BARTeligible
coal­
fired
units.

Unit
type
Coal
type
#
units
nation­
wide
National
Average
($/
ton)

Dry­
bottom
wall­
fired
Bituminous
114
1229
Sub­
bituminous
66
576
Lignite
3
1296
Tangentia
l­
fired
Bituminous
105
567
Sub­
bituminous
72
281
Lignite
9
614
Cell
Burners
Bituminous
32
1287
Sub­
bituminous
3
1021
Dry­
turbofired
Bituminous
7
775
Sub­
bituminous
7
599
Wet­
bottom
Bituminous
6
378
Cyclones
(
with
SCR)
All
56
900
68
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.

69
Id.

182
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.
68
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.

A
detailed
discussion
of
our
analysis
is
in
the
docket.
69
For
data
on
emissions
and
existing
control
technology
in
use
at
the
70
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
Website,
data
and
maps
page
(
www.
epa.
gov/
airmarkets).

71
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.

183
BART­
eligible
EGUs,
we
used
EPA's
Clean
Air
Markets
Division
database.
70
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
costeffectiveness
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
costeffectiveness
is
$
900
per
ton.
71
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.

Oil
and
Gas­
fired
Units
72
Id.

184
For
oil­
fired
and
gas­
fired
units,
we
recommend
that
States
consider
requiring
these
units
to
installbelieve
that
installation
of
current
combustion
control
technology
is
highly
cost­
effective
and
should
be
considered
in
determining
BART
for
these
sources.
but
we
are
not
establishing
a
presumption
for
these
units.
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.
72
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
carefully
consider
the
installation
of
current
combustion
control
technology
on
oil
and
gas­
fired
units.

IV.
How
does
today's
rule
affect
States
options
for
using
alternative
strategies
in
lieu
of
source­
by­
source
BART?

A.
Background
Over
the
past
several
years,
there
have
been
a
number
of
rule
makings
and
court
decisions
on
the
subject
of
BART
and
BART­
185
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
(
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
(
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
(
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
186
reductions
and
visibility
improvement,
but
did
not
provide
further
specificity.
See
64
FR
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.
73
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).

187
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

bysource
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.
73
However,

noting
that
the
CAIR
trading
program
affected
only
one
category
of
BART­
eligible
sources
(
EGUs),
rather
than
all
BART­
eligible
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
188
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,
74
we
provided
analyses
demonstrating
that
CAIR
would
achieve
greater
emission
reductions
than
BART,
and
would
make
greater
reasonable
progress
according
to
the
twopronged
visibility
test
previously
proposed
in
the
BART
guidelines.

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
betterthan
BART
test
was
not
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
189
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.

B
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,
66
FR
38108,
July
20,
2001,
and
reproposed
in
the
identical
form
in
the
2004
BART
guidelines
reproposal.
69
FR
25184,
May
5,
2004.
The
test
appeared
as
an
element
of
the
190
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
191
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
§
301(
a),
and
under
CAA
§
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
169A(
b)(
2)(
A)
and
to
promulgate
such
measures
as
may
be
192
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
v.

EPA
upheld
this
interpretation
of
the
BART
provisions'

relationship
to
the
broader
reasonable
progress
requirements
of
the
Act.
Slip.
Op.
at
13.
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
v.
EPA
suggests
that
those
cases
rendered
EPA's
rulemaking
authority
under
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
§
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
193
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
§
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
nodegradation
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
necessary
to
make
progress
at
every
mandatory
federal
Class
I
area.
194
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
usedthe
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
no
harm
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
195
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
be
worse
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
75
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
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%
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.

196
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%
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%
of
days.

Thus,
under
the
first
prong,
visibility
must
not
degrade
at
any
one
Class
I
area
on
either
the
best
20%
or
the
worst
20%
days75
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.

Third,
the
proposed
guidelines
did
not
define
"
affected"

Class
I
areas
for
purposes
of
the
comparison.
In
applying
the
197
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
BARTalternative
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
198
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
76
"
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"
http://
www.
epa.
gov/
cair/
pdfs/
finaltech04.
pdf.

199
showing
that
CAIR
will
achieve
greater
reasonable
progress
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
 
707
and
70
FR
25162,
25299
 
304
and
associated
Technical
Support
Documents76
for
full
details.

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
77
200
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)
.77
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
201
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
SO
2
and
NO
x
Emissions­
as
Projected
in
CAIR
SNPR
(
in
thousands
of
tons
per
year)

2015
Base
Case
EGU
Emissions
2015
"
CAIR"
2015
Modeled
Nationwide
BART
Additional
Reduction
from
"
CAIR"
(
Nationwide
BART
minus
"
CAIR")

Nationwide
SO2
9,081
5,260
7,012
1,752
Nationwide
NOx
3,950
2,248
2,781
533
202
Table
2.
EGU
SO
2
and
NO
x
Emissions­
as
Projected
in
CAIR
NFR
(
in
thousands
of
tons
per
year)

2015
Base
Case
EGU
Emissions
2015
CAIR
+
BART
2015
Nationwide
BART
Additional
Reduction
from
CAIR
+
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.

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%
best
and
20%
worst
visibility
days.

For
the
SNPR
modeling,
we
used
the
Regional
Modeling
System
for
Aerosols
and
Deposition
(
REMSAD)
model
to
calculate
these
203
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,
78
See
Footnote
[
5],
Supra.

204
must
be
better
under
the
trading
program
than
under
sourcespecific
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.
78
The
overall
results
are
presented
in
tables
3
and
4
below,

representing
the
SNPR
and
NFR
modeling
respectively.
79
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.

205
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
East79
National
East
National
20%
Worst
Days
2.0
0.7
1.0
0.4
20%
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
East8
National
East
National
20%
Worst
Days
1.6
0.5
0.7
0.2
20%
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%
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,
206
and
in
the
NFR,
1.6
deciviews
compared
to
0.7
deciviews
improvement).

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
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.
207
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%
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%
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
208
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
thatthese
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%
control
or
0.10
lbs/
mmBtu
at
uncontrolled
EGUs
greater
than
100
MW.
In
the
new
projections,
the
control
assumptions
were
changed
to
95%
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
209
increased
to
200
MW,
to
better
reflect
the
presumptionsincluded
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)

2015
CAIR
+
BART
2015
Nationwide
BART
Additional
Reduction
from
CAIR
+
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
80The
1,000
ton
per
year
increase
in
NO
x
in
Connecticut
represents
~
0.003%
of
the
total
EGU
NO
x
in
the
2015
base
case
and
the
2,000
ton
per
year
increase
in
SO
2
in
New
Jersey
represents
~
0.0005%
of
the
total
EGU
SO
2
.
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.

210
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
l00,000
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
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).
80
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.

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%
worst
81The
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.

211
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).
81
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.
82
California,
Delaware,
Florida,
Georgia,
Iowa,
Louisiana,
Michigan,
Mississippi,
Missouri,
North
Carolina,
Texas,
and
Wisconsin.

83
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.

84
Alabama,
Louisiana,
Michigan,
Mississippi,
Missouri,
New
Jersey,
North
Carolina,
Texas,
Wisconsin
212
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
States82
where
nationwide
BART
SO2
reductions
were
greater
than
CAIR
+
BART
reductions.
83
In
those
12
States,
BART
emissions
achieved
~
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,
there
are
only
9
States84
in
which
BART
reductions
are
greater
under
nationwide
BART
than
CAIR
+
BART
in
the
West.
In
those
9
States,
BART
emissions
achieved
~
472,000
more
tons
of
SO2
reduction
compared
to
CAIR
+
BART.
In
the
rest
of
the
States,
85
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.

213
CAIR
+
BART
achieved
an
additional
3.4
million
tons
per
year
of
SO2
reduction
compared
to
BART.
85
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
86A
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.

214
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
§
51.302(
c)
related
to
BART
for
reasonably
attributable
impairment
from
the
pollutants
covered
by
the
CAIR
cap
and
trade
program.
86
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
v.
EPA.
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
v.
EPA,
Slip.
Op.
at
13.
Moreover,
the
CAIR
program
is
not
infected
in
any
way
with
the
"
group
BART"

methodology
held
invalid
by
the
court.
That
is
because
CAIR
215
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:

(
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
216
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
308(
e)(
4),
this
determination
is
consistent
with
the
policy
contained
in
308(
e)(
2)
requiring
inlieu
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
87
See
"
2002
Base
Year
Emission
Inventory
SIP
Planning:
8­
hr
Ozone,
PM2.5,
and
Regional
Haze
Programs,"
November
8,
2002,
Guidance
Memorandum,
http://
www.
epa.
gov/
ttn/
oarpg/
t1/
memoranda/
2002bye_
gm.
pdf
217
haze
SIPs
is
200287;
therefore
CAIR
reductions
are
surplus
to
requirements
as
of
that
year.

(
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
218
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
88Similar
to
the
BART
factors,
the
reasonable
progress
factors
are:
the
cost
of
compliance,
the
time
necessary
for
compliance,
the
energy
and
nonair
quality
environmental
219
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
§
308(
d)(
1),
and
to
develop
long
term
strategies,
considering
all
anthropogenic
sources
of
visibility
impairing
pollutants,
as
required
by
§
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
§
169A(
g)(
1).
88
impacts
of
compliance,
and
the
remaining
useful
life
of
any
existing
sources
subject
to
such
requirements.

220
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.
