1
Summary
of
the
Updated
Analysis
of
the
CAIR
"
Better­
than­
BART"
Test
EPA
had
previously
made
a
determination
that
compliance
with
the
CAIR,
if
achieved
by
power
plants
under
the
model
cap­
and­
trade
program,
is
anticipated
to
satisfy
the
best
available
retrofit
technology
(
BART)
requirements
for
those
sources
as
a
"
better
than
BART"
alternative.
EPA
used
CAIR
and
BART
emissions
and
air
quality
modeling
data
to
complete
a
"
better­
than­
BART"
analysis.
We
modeled
2015
emissions
resulting
from
implementation
of
CAIR
in
combination
with
BART
outside
the
CAIR
region
(
CAIR
+
BART),
as
well
as
from
BART
on
a
nationwide
basis,
in
the
absence
of
CAIR
(
nationwide
BART).
Application
of
the
better
than
BART
test
showed
that
CAIR
+
BART
was
indeed
better
than
nationwide
BART.

Since
the
better
than
BART
modeling
was
completed,
several
changes
were
made
to
the
CAIR
region
and
to
the
presumed
BART
control
levels.
We
therefore
redid
the
emission
projections
to
see
if
the
changes
could
possibly
affect
the
Better
than
BART
demonstration.

Most
significantly,
the
final
CAIR
included
AR,
DE,
and
NJ
only
for
purposes
of
Nox
contribution
to
ozone,
whereas
the
modeling
had
been
based
on
the
inclusion
of
these
States
for
SO2
contribution
to
PM
as
well.
The
new
emission
projections
are
based
on
the
application
of
CAIR
only
for
ozone
in
these
States.

For
nationwide
BART,
for
SO2
the
old
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
current
intention
for
the
presumptive
controls
in
the
final
BART
guidelines.
For
Nox,
the
old
projections
were
based
on
an
assumed
emission
rate
of
0.2
lbs/
mmBTU
at
all
BART
eligible
EGUs
nationwide.
The
new
projections
are
based
on
the
assumption
of
combustion
controls
on
all
BART
eligible
units
except
cyclones
which
have
SCR,
and
the
operation
of
all
existing
SCR
and
SNCRs
annually,
instead
of
just
in
the
ozone
season.
Finally
for
both
pollutants,
the
threshold
for
application
of
controls
was
increased
to
200
MW,
to
better
reflect
the
presumption
we
anticipate
to
be
included
in
the
final
BART
guidelines.

I.
"
BETTER
THAN
BART"
TEST
PRESENTED
IN
FINAL
CAIR
A.
Emissions
projections
Table
1
shows
the
nationwide
total
EGU
SO
2
and
NO
x
emissions
for
the
modeled
2015
base
case,
CAIR
+
BART
case,
and
nationwide
BART
case.
1The
ambient
data
from
2001
was
used
because
2001
was
the
base
year
for
the
air
quality
modeling.

2
Table
1.
EGU
SO
2
and
NO
x
Emissions­
Modeled
Scenarios
(
in
thousands
of
tons
per
year)

2015
Base
Case
EGU
Emissions
2015
Modeled
CAIR
+
BART
2015
Modeled
Nationwide
BART
Additional
Reduction
from
CAIR
+
BART
(
Nationwide
BART­
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
table
above,
for
SO
2,
the
modeled
CAIR
+
BART
would
achieve
2.4
million
tons
more
reductions
than
modeled
nationwide
BART
in
2015.
For
NO
x,
the
CAIR
+
BART
policy
was
projected
to
result
in
about
638,000
tons
more
emissions
reductions
than
the
modeled
BART
nationwide
policy
in
2015.

B.
Modeling
Results
Using
these
emissions,
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
(
determined
from
2001
ambient
data)
at
the
116
Class
I
areas
which
have
complete
ambient
data
for
20011.

We
then
applied
the
two
prong
better
than
BART
test
which
was
defined
in
the
proposed
BART
rule.
Under
the
first
prong,
visibility
must
not
decline
at
any
Class
I
area,
as
determined
by
comparing
the
predicted
visibility
impacts
at
each
affected
Class
I
area
under
the
(
CAIR)
trading
program
with
future
base
case
visibility
conditions.
Under
the
second
prong,
overall
visibility,
as
measured
by
the
average
improvement
at
all
affected
Class
I
areas,
must
be
better
under
the
trading
program
than
under
source­
specific
BART.
The
future
year
air
quality
modeling
results
were
used
to
make
this
demonstration.

The
visibility
impacts
of
the
CAIR
+
BART
scenario
were
compared
to
base
case
2015
visibility
conditions
(
without
CAIR
or
BART)
to
determine
whether
the
CAIR
resulted
in
a
degradation
of
visibility
at
any
Class
I
area.
We
also
compared
these
visibility
impacts
with
the
visibility
impacts
of
nationwide
BART
implementation,
to
assess
whether
the
proposed
CAIR
would
result
in
greater
average
visibility
improvement
than
nationwide
BART.
3
The
modeled
effects
of
the
emissions
reductions
on
visibility
are
expressed
in
terms
of
expected
future
visibility
impairment
on
the
20%
best
and
20%
worst
days
(
in
deciviews).
The
modeling
results
show
that
the
CAIR
+
BART
case
will
not
result
in
degradation
of
visibility
on
the
20%
best
and
the
20%
worst
days,
compared
to
the
2015
base
case
conditions,
at
any
of
the
116
Class
I
areas
considered.
In
each
of
the
116
areas
 
the
25
within
the
CAIR
region
and
the
91
outside
of
it
 
visibility
is
expected
to
improve
or
at
worst
remain
unchanged
(
compared
to
2015
base
case
visibility).

For
Class
I
areas
in
the
proposed
CAIR
region,
our
analysis
indicates
that
CAIR
+
BART
emissions
reductions
in
the
East
produce
greater
visibility
improvements
than
nationwide
BART.
Specifically,
for
the
29
Eastern
Class
I
areas
analyzed,
the
average
visibility
improvement
on
the
20
percent
worst
days
expected
as
a
result
of
the
CAIR
+
BART
is
1.6
deciviews
(
dv),
and
the
average
degree
of
improvement
predicted
for
nationwide
BART
is
0.7
dv.
The
average
visibility
improvement
on
the
20
percent
best
days
expected
as
a
result
of
the
CAIR
+
BART
is
0.4
deciviews
(
dv),
and
the
average
degree
of
improvement
predicted
for
nationwide
BART
is
0.2
dv.

On
a
national
basis,
the
visibility
modeling
shows
that
for
the
116
class
I
areas
evaluated,
the
average
visibility
improvement,
on
the
20
percent
worst
days
was
0.5
dv
for
the
CAIR
+
BART
scenario
and
0.2
dv
for
the
nationwide
BART
scenario.
The
average
nationwide
visibility
improvement
on
the
20%.
best
days,
in
2015
was
0.1
dv
under
the
CAIR
+
BART
scenario,
and
also
0.1
dv
under
the
nationwide
BART
approach
Both
programs
achieve
a
small,
but
essentially
equal
improvement
in
average
visibility
on
the
20%
best
days.

II.
CHECK
ON
BETTER
THAN
BART
TEST
BASED
ON
UPDATED
EMISSIONS
PROJECTIONS
A.
Updated
Emission
Projections
The
updated
CAIR
+
BART
emissions
are
slightly
higher
than
the
modeled
CAIR
+
BART
emissions,
but
the
difference
between
the
CAIR
+
BART
and
nationwide
BART
scenarios
are
even
larger
compared
to
the
original
determination.
Table
2
shows
the
updated
CAIR
+
BART
and
nationwide
BART
emissions
totals.

Table
2.
"
Updated"
EGU
SO
2
and
NO
x
Emissions
(
in
thousands
of
tons
per
year)

2015
Base
Case
EGU
Emissions
Updated
2015
CAIR
+
BART
Updated
2015
Nationwide
BART
Additional
Reduction
from
updated
CAIR
+
BART
(
Nationwide
BART­
CAIR/
BART)

Nationwide
SO2
9,084
5,042
7,953
2,911
Nationwide
NOx
3,721
2,000
2,738
738
2The
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.
Since
there
are
no
Class
I
areas
in
Connecticut,
we
would
expect
this
small
increase
in
NO
x
to
have
little
or
no
impact
on
visibility
in
any
Class
I
area.

3The
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
SO
2
and
100,000
tons
of
NO
x.

4
As
can
be
seen
in
the
table
above,
for
SO
2,
the
updated
CAIR
+
BART
achieves
about
2.9
million
tons
more
reductions
than
updated
nationwide
BART
in
2015.
For
NO
x,
the
updated
CAIR
+
BART
policy
is
projected
to
result
in
about
738,000
tons
more
emissions
reductions
than
the
updated
BART
nationwide
policy
in
2015.

Also,
the
difference
in
emissions
between
the
updated
CART
+
BART
and
nationwide
BART
scenarios
is
larger
than
the
difference
between
the
modeled
(
i.
e.,
CAIR
NFR)
CAIR
+
BART
and
nationwide
BART
scenarios.
The
delta
between
the
updated
CAIR
+
BART
and
nationwide
BART
scenarios
is
now
larger
by
485,000
tons
of
SO
2
reduction
and
l02,000
tons
of
NO
x
reduction.

B.
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
SO
2
or
NO
x
(
except
for
a
very
small
~
1,000
ton
increase
in
NOx
in
Connecticut.
2).
That
is
consistent
with
the
modeled
CAIR
+
BART
case
in
which
no
degradation
was
found.
Consequently
we
expect
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
modeled
CAIR
+
BART
was
much
greater
(
on
the
20%
worst
visibility
days)
than
the
nationwide
BART
case.
In
the
modeled
scenario,
the
larger
visibility
improvement
from
CAIR
+
BART
was
achieved
by
reducing
SO
2
emissions
by
an
additional
~
2.4
million
tons
per
year
compared
to
nationwide
BART
and
NO
x
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
SO
2
and
738,000
tons
of
NO
X
3).
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
5
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.
It
does
not
appear
that
the
differences
in
geographic
distribution
resulted
in
clusters
of
nearby
States
being
skewed
in
one
direction
or
another.
(
A
spreadsheet
containing
the
State­
by­
State
numbers
is
attached).
This,
combined
with
the
fact
that
the
second
prong
is
based
on
average
overall
improvement
and
the
fact
that
the
new
projections
show
that
the
difference
between
CAIR
and
BART
reductions
is
even
greater
than
previously
estimated,
allows
us
to
state
with
a
high
degree
of
confidence
that
the
updated
CAIR
+
BART
scenario
passes
the
second
prong
of
the
better
than
BART
test.

In
concluding
that
both
prongs
of
the
better
than
BART
test
would
be
passed
using
the
updated
emissions,
we
believe
that
the
better
than
BART
determination
for
the
updated
CAIR
+
BART
case
can
be
confirmed
without
completing
further
air
quality
modeling.
