III.
HOW
TO
IDENTIFY
SOURCES
"
SUBJECT
TO
BART"

Once
you
have
compiled
your
list
of
BART­
eligible
sources,

you
need
to
determine
whether
(
1)
to
make
BART
determinations
for
all
of
them
or
(
2)
to
consider
exempting
some
of
them
from
BART
because
they
may
not
reasonably
be
anticipated
to
cause
or
contribute
to
any
visibility
impairment
in
a
Class
I
area.
If
you
decide
to
make
BART
determinations
for
all
the
BART­
eligible
sources
on
your
list,
you
should
work
with
your
regional
planning
organization
(
RPO)
to
show
that,
collectively,
they
cause
or
contribute
to
visibility
impairment
in
at
least
one
Class
I
area.

You
should
then
make
individual
BART
determinations
by
applying
the
five
statutory
factors
discussed
in
Section
IV
below.

On
the
other
hand,
you
also
may
choose
to
perform
an
initial
examination
to
determine
whether
a
particular
BART­
eligible
source
or
group
of
sources
causes
or
contributes
to
visibility
impairment
in
nearby
Class
I
areas.
If
your
analysis,
or
information
submitted
by
the
source,
shows
that
an
individual
source
or
group
of
sources
(
or
certain
pollutants
from
those
sources)
is
not
reasonably
anticipated
to
cause
or
contribute
to
any
visibility
impairment
in
a
Class
I
area,
then
you
do
not
need
to
make
BART
determinations
for
that
source
or
group
of
sources
(
or
for
certain
pollutants
from
those
sources).
In
such
a
case,

the
source
is
not
"
subject
to
BART"
and
you
do
not
need
to
apply
the
five
statutory
factors
to
make
a
BART
determination.
This
section
of
the
Guideline
discusses
several
approaches
that
you
can
use
to
exempt
sources
from
the
BART
determination
process.

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

1.
How
Do
I
Establish
a
Threshold?

One
of
the
first
steps
in
determining
whether
sources
cause
or
contribute
to
visibility
impairment
for
purposes
of
BART
is
to
establish
a
threshold
(
measured
in
deciviews)
against
which
to
measure
the
visibility
impact
of
one
or
more
sources.
A
single
source
that
is
responsible
for
a
1.0
deciview
change
or
more
should
be
considered
to
"
cause"
visibility
impairment;
a
source
that
causes
less
than
a
1.0
deciview
change
may
still
contribute
to
visibility
impairment
and
thus
be
subject
to
BART.

Because
of
varying
circumstances
affecting
different
Class
I
areas,
the
appropriate
threshold
for
determining
whether
a
source
"
contributes
to
any
visibility
impairment"
for
the
purposes
of
BART
may
reasonably
differ
across
States.
As
a
general
matter,

any
threshold
that
you
use
for
determining
whether
a
source
"
contributes"
to
visibility
impairment
should
not
be
higher
than
0.5
deciviews.

In
setting
a
threshold
for
"
contribution,"
you
should
consider
the
number
of
emissions
sources
affecting
the
Class
I
areas
at
issue
and
the
magnitude
of
the
individual
sources'
1
We
expect
that
regional
planning
organizations
will
have
modeling
information
that
identifies
sources
affecting
visibility
in
individual
class
I
areas.
impacts.
1
In
general,
a
larger
number
of
sources
causing
impacts
in
a
Class
I
area
may
warrant
a
lower
contribution
threshold.

States
remain
free
to
use
a
threshold
lower
than
0.5
deciviews
if
they
conclude
that
the
location
of
a
large
number
of
BARTeligible
sources
within
the
State
and
in
proximity
to
a
Class
I
area
justify
this
approach.

2.
What
Pollutants
Do
I
Need
to
Consider?

You
must
look
at
SO2,
NOx,
and
direct
particulate
matter
(
PM)
emissions
in
determining
whether
sources
cause
or
contribute
to
visibility
impairment,
including
both
PM10
and
PM2.5.

Consistent
with
the
approach
for
identifying
your
BART­
eligible
sources,
you
do
not
need
to
consider
less
than
de
minimis
emissions
of
these
pollutants
from
a
source.

As
explained
in
Section
II,
you
must
use
your
best
judgement
to
determine
whether
VOC
or
ammonia
emissions
are
likely
to
have
an
impact
on
visibility
in
an
area.
In
addition,
you
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,
you
should
distinguish
between
the
fine
and
coarse
particle
components
of
direct
particulate
emissions.
Although
both
fine
and
coarse
particulate
matter
contribute
to
visibility
impairment,
the
longrange
transport
of
fine
particles
is
of
particular
concern
in
the
formation
of
regional
haze.
Air
quality
modeling
results
used
in
the
BART
determination
will
provide
a
more
accurate
prediction
of
a
source's
impact
on
visibility
if
the
inputs
into
the
model
account
for
the
relative
particle
size
of
any
directly
emitted
particulate
matter
(
i.
e.
PM10
vs.
PM2.5).

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

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

Option
1:
Individual
Source
Attribution
Approach
(
Dispersion
Modeling)

You
can
use
dispersion
modeling
to
determine
that
an
individual
source
cannot
reasonably
be
anticipated
to
cause
or
contribute
to
visibility
impairment
in
a
Class
I
area
and
thus
is
not
subject
to
BART.
Under
this
option,
you
can
analyze
an
individual
source's
impact
on
visibility
as
a
result
of
its
emissions
of
SO2,
NOx
and
direct
PM
emissions.
Dispersion
modeling
cannot
currently
be
used
to
estimate
the
predicted
impacts
on
visibility
from
an
individual
source's
emissions
of
VOC
or
ammonia.
You
may
use
a
more
qualitative
assessment
to
determine
on
a
case­
by­
case
basis
which
sources
of
VOC
or
ammonia
2
The
model
code
and
its
documentation
are
available
at
no
cost
for
download
from
http://
www.
epa.
gov/
scram001/
tt22.
htm#
calpuff.

3
The
Guideline
on
Air
Quality
Models
addresses
the
regulatory
application
of
air
quality
models
for
assessing
criteria
pollutants
under
the
CAA,
and
describes
further
the
procedures
for
using
the
CALPUFF
model,
as
well
as
for
obtaining
approval
for
the
use
of
other,
nonguideline
models.
emissions
may
be
likely
to
impair
visibility
and
should
therefore
be
subject
to
BART
review,
as
explained
in
section
II.
A.
3.
above.

You
can
use
CALPUFF2,
or
another
EPA
approved
model,
to
predict
the
visibility
impacts
from
a
single
source
at
a
Class
I
area.
CALPUFF
is
the
best
regulatory
modeling
application
currently
available
for
predicting
a
single
source's
contribution
to
visibility
impairment
and
is
currently
the
only
EPA­
approved
model
for
use
in
estimating
single
source
pollutant
concentrations
resulting
from
the
long
range
transport
of
primary
pollutants.
3
It
can
also
be
used
for
some
other
purposes,
such
as
the
visibility
assessments
addressed
in
today's
rule,
to
account
for
the
chemical
transformation
of
SO2
and
NOx.

There
are
several
steps
for
making
an
individual
source
attribution
using
a
dispersion
model:

!
Develop
a
modeling
protocol.

Some
critical
items
to
include
in
the
protocol
are
the
meteorological
and
terrain
data
that
will
be
used,
as
well
as
the
source­
specific
information
(
stack
height,
temperature,
exit
velocity,
elevation,
and
emission
rates
of
applicable
pollutants)
4
Interagency
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.
and
receptor
data
from
appropriate
Class
I
areas.
We
recommend
following
EPA's
Interagency
Workgroup
on
Air
Quality
Modeling
(
IWAQM)
Phase
2
Summary
Report
and
Recommendations
for
Modeling
Long
Range
Transport
Impacts4
for
parameter
settings
and
meteorological
data
inputs.
You
may
use
other
settings
from
those
in
IWAQM,
but
you
should
identify
these
settings
and
explain
your
selection
of
these
settings.

One
important
element
of
the
protocol
is
in
establishing
the
receptors
that
will
be
used
in
the
model.
The
receptors
that
you
use
should
be
located
in
the
nearest
Class
I
area
with
sufficient
density
to
identify
the
likely
visibility
effects
of
the
source.

For
other
Class
I
areas
in
relatively
close
proximity
to
a
BARTeligible
source,
you
may
model
a
few
strategic
receptors
to
determine
whether
effects
at
those
areas
may
be
greater
than
at
the
nearest
Class
I
area.
For
example,
you
might
chose
to
locate
receptors
at
these
areas
at
the
closest
point
to
the
source,
at
the
highest
and
lowest
elevation
in
the
Class
I
area,
at
the
IMPROVE
monitor,
and
at
the
approximate
expected
plume
release
height.
If
the
highest
modeled
effects
are
observed
at
the
nearest
Class
I
area,
you
may
choose
not
to
analyze
the
other
Class
I
areas
any
further,
as
additional
analyses
might
be
unwarranted.
You
should
bear
in
mind
that
some
receptors
within
the
relevant
Class
I
area
may
be
less
than
50
km
from
the
source
while
other
receptors
within
that
same
Class
I
area
may
be
greater
than
50
km
from
the
same
source.
As
indicated
by
the
Guideline
on
Air
Quality
Models,
this
situation
may
call
for
the
use
of
two
different
modeling
approaches
for
the
same
Class
I
area
and
source,
depending
upon
the
State's
chosen
method
for
modeling
sources
less
than
50
km.
In
situations
where
you
are
assessing
visibility
impacts
for
source­
receptor
distances
less
than
50
km,
you
should
use
expert
modeling
judgment
in
determining
visibility
impacts,
giving
consideration
to
both
CALPUFF
and
other
EPA­
approved
methods.

In
developing
your
modeling
protocol,
you
may
want
to
consult
with
EPA
and
your
regional
planning
organization
(
RPO).

Up­
front
consultation
will
ensure
that
key
technical
issues
are
addressed
before
you
conduct
your
modeling.

!
Run
the
model
in
accordance
with
the
accepted
protocol
and
compare
the
predicted
visibility
impacts
with
your
threshold
for
"
contribution."

You
should
calculate
daily
visibility
values
for
each
receptor
as
the
change
in
deciviews
compared
against
natural
visibility
conditions.
You
can
use
EPA's
"
Guidance
for
Estimating
Natural
Visibility
Conditions
Under
the
Regional
Haze
Rule,"
EPA­
454/
B­
03­
005
(
September
2003)
in
making
this
calculation.
To
determine
whether
a
source
may
reasonably
be
anticipated
to
cause
or
contribute
to
visibility
impairment
at
Class
I
area,
you
then
compare
the
impacts
predicted
by
the
model
against
the
threshold
that
you
have
selected.

The
emissions
estimates
used
in
the
models
are
intended
to
reflect
steady­
state
operating
conditions
during
periods
of
high
capacity
utilization.
We
do
not
generally
recommend
that
emissions
reflecting
periods
of
start­
up,
shutdown,
and
malfunction
be
used,
as
such
emission
rates
could
produce
higher
than
normal
effects
than
would
be
typical
of
most
facilities.
In
addition,
the
monthly
average
relative
humidity
is
used,
rather
than
the
daily
average
humidity
 
an
approach
that
effectively
lowers
the
peak
values
in
daily
model
averages.

For
these
reasons,
if
you
use
the
modeling
approach
we
recommend,
you
should
compare
your
"
contribution"
threshold
against
the
98th
percentile
of
values.
If
the
98th
percentile
value
from
your
modeling
is
less
than
your
contribution
threshold,
then
you
may
conclude
that
the
source
does
not
contribute
to
visibility
impairment
and
is
not
subject
to
BART.

Option
2:
Use
of
Model
Plants
to
Exempt
Individual
Sources
with
Common
Characteristics.

Under
this
option,
analysis
of
model
plants
could
be
used
to
exempt
certain
BART­
eligible
sources
that
share
specific
characteristics.
It
may
be
most
useful
to
use
this
type
of
analysis
to
identify
the
types
of
small
sources
that
do
not
cause
or
contribute
to
visibility
impairment
for
purposes
of
BART,
and
5
[
insert
reference
to
Mark's
docket
memo]
thus
should
not
be
subject
to
a
BART
review.
Different
Class
I
areas
may
have
different
characteristics,
however,
so
you
should
use
care
to
ensure
that
the
criteria
you
develop
are
appropriate
for
the
applicable
cases.

In
carrying
out
this
approach,
you
could
use
modeling
analyses
of
representative
plants
to
reflect
groupings
of
specific
sources
with
important
common
characteristics.
Based
on
these
analyses,
you
may
find
that
certain
types
of
sources
are
clearly
anticipated
to
cause
or
contribute
to
visibility
impairment.
You
could
then
choose
to
categorically
require
those
types
of
sources
to
undergo
a
BART
determination.
Conversely,

you
may
find
based
on
representative
plant
analyses
that
certain
types
of
sources
are
not
reasonably
anticipated
to
cause
or
contribute
to
visibility
impairment.
To
do
this,
you
may
conduct
your
own
modeling
to
establish
emission
levels
and
distances
from
Class
I
areas
on
which
you
can
rely
to
exempt
sources
with
those
characteristics.
For
example,
based
on
your
modeling
you
might
choose
to
exempt
all
NOx­
only
sources
that
emit
less
than
a
certain
amount
per
year
and
are
located
a
certain
distance
from
a
Class
I
area.
You
could
then
choose
to
categorically
exempt
such
sources
from
the
BART
determination
process.

Our
analyses
of
visibility
impacts
from
model
plants
provide
a
useful
example
of
the
type
of
analyses
that
can
be
used
to
exempt
categories
of
sources
from
BART.
5
In
our
analysis,
we
developed
model
plants
(
EGUs
and
non­
EGUs),
with
representative
plume
and
stack
characteristics,
for
use
in
considering
the
visibility
impact
from
emission
sources
of
different
sizes
and
compositions
at
distances
of
50,
100
and
200
kilometers
from
two
hypothetical
Class
I
areas
(
one
in
the
East
and
one
in
the
West).

Since
the
plume
and
stack
characteristics
of
these
model
plants
were
developed
considering
the
broad
range
of
sources
within
the
EGU
and
non­
EGU
categories,
they
do
not
necessarily
represent
any
specific
plant.
However,
the
results
of
these
analyses
are
instructive
in
the
development
of
an
exemption
process
for
any
Class
I
area.

In
preparing
our
analysis,
we
have
made
a
number
of
assumptions
and
exercised
certain
modeling
choices;
some
of
these
have
a
tendency
to
lend
conservatism
to
the
results,
overstating
the
likely
effects,
while
others
may
understate
the
likely
effects.
On
balance,
when
all
of
these
factors
are
considered,

we
believe
that
our
examples
reflect
realistic
treatments
of
the
situations
being
modeled.
Based
on
our
analysis,
we
believe
that
a
State
that
has
established
0.5
deciviews
as
a
contribution
threshold
could
reasonably
exempt
from
the
BART
review
process
sources
that
emit
less
than
500
tons
per
year
of
Nox
or
SO2
(
or
combined
Nox
and
SO2),
as
long
as
these
sources
are
located
more
than
50
kilometers
from
any
Class
I
area;
and
sources
that
emit
less
than
1000
tons
per
year
of
Nox
or
SO2
(
or
combined
Nox
and
SO2)
that
are
located
more
than
100
kilometers
from
any
Class
I
area.

Option
3:
Cumulative
Modeling
to
Show
that
No
sources
in
a
State
are
subject
to
BART
You
may
also
submit
to
EPA
a
demonstration,
based
on
an
analysis
of
overall
visibility
impacts,
that
emissions
from
BART­
eligible
sources
in
your
State,
considered
together,
are
not
reasonably
anticipated
to
cause
or
contribute
to
any
visibility
impairment
in
a
Class
I
area
and
thus
no
source
should
be
subject
to
BART.
You
may
do
this
on
a
pollutant
by
pollutant
basis
or
for
all
visibility­
impairing
pollutants
to
determine
if
emissions
from
these
sources
contribute
to
visibility
impairment.

For
example,
emissions
of
SO2
from
your
BART­
eligible
sources
may
clearly
cause
or
contribute
to
visibility
impairment,

while
direct
emissions
of
PM2.5
from
these
sources
may
not
contribute
to
impairment.
If
you
can
make
such
a
demonstration,

then
you
may
reasonably
conclude
that
none
of
your
BART­
eligible
sources
are
subject
to
BART
for
a
particular
pollutant
or
pollutants.
As
noted
above,
your
demonstration
should
take
into
account
the
interactions
among
pollutants
and
their
resulting
impacts
on
visibility
before
making
any
pollutant­
specific
determinations.

Analyses
may
be
conducted
using
several
alternative
modeling
approaches.
First,
you
may
use
the
CALPUFF
or
another
EPAapproved
model
as
described
in
Option
1
to
evaluate
the
impacts
of
individual
sources
on
downwind
Class
I
areas,
aggregating
those
impacts
to
determine
the
collective
contribution
of
all
BART­
eligible
sources
to
visibility
impairment.
You
may
also
use
a
photochemical
grid
model.
As
a
general
matter,
the
larger
the
number
of
sources
being
modeled,
the
more
appropriate
it
may
be
to
use
a
photochemical
grid
model.
However,
because
such
models
are
significantly
less
sensitive
than
dispersion
models
to
the
contributions
of
one
or
a
few
sources,
as
well
as
to
the
interactions
among
sources
that
are
widely
distributed
geographically,
if
you
wish
to
use
a
grid
model,
you
should
consult
with
the
appropriate
EPA
Regional
Office
to
develop
an
appropriate
modeling
protocol.
