Document ID: EPA-HQ-OAR-2003-0053-2216
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2005-12-02T05:00Z

C.
PM2.5
Modeling
for
Minnesota
One
petitioner
asserts
that
EPA's
modeling
to
determine
whether
emissions
from
Minnesota
significantly
contribute
to
downwind
nonattainment
of
the
PM2.5
NAAQS
failed
to
take
into
account
certain
emission
reductions
required
by
State
programs.
Petitioner
asserts
that
if
these
reductions
had
been
properly
included
in
the
modeling
done
for
CAIR,
the
modeling
might
show
that
the
state
of
Minnesota
does
not
significantly
contribute
to
downwind
nonattainment
of
the
PM2.5
NAAQS.
The
petitioner
also
asked
EPA
to
stay
implementation
of
the
CAIR
in
Minnesota.

The
Agency
is
not
taking
action
on
the
request
for
a
stay
at
this
time.

The
Agency
agrees
that
EPA's
modeling
of
the
contribution
of
emissions
from
Minnesota
to
downwind
PM2.5
nonattainment
for
the
final
CAIR
did
not
fully
account
for
the
effects
on
future
year
emissions
of
certain
State
control
programs.
In
order
to
ensure
that
all
parties
have
ample
opportunity
to
comment
on
all
aspects
of
this
issue,

EPA
is
reconsidering
the
air
quality
modeling
inputs
for
Minnesota.

Using
the
corrected
inputs
described
below,
EPA
recently
remodeled
the
PM2.5
contributions
from
emissions
in
Minnesota.
In
this
analysis,
EPA
used
the
same
PM2.5
modeling
platform
that
was
used
for
the
final
CAIR
modeling.
This
modeling
platform
is
described
in
the
CAIR
Air
Quality
Modeling
Technical
Support
Document
("
Technical
Support
Document
for
the
Final
Clean
Air
Interstate
Rule,

Air
Quality
Modeling,"
March
2005,
OAR­
2003­
0053­
2123).

The
EPA
is
not
taking
comment
on
the
modeling
platform
itself,
only
on
the
corrected
2010
emissions
inputs
for
Minnesota,
as
described
below.

The
result
of
the
revised
2010
Minnesota
PM2.5
contribution
modeling
is
that
Minnesota
contributes
a
maximum
of
0.20
µ
g/
m3
to
PM2.5
nonattainment
in
Chicago,
IL.

This
result
confirms
the
findings
from
the
CAIR
PM2.5
contribution
modeling
that
emissions
in
Minnesota
make
a
significant
contribution
to
PM2.5
nonattainment
in
Chicago,

IL.
The
2010
emissions
inputs
used
in
the
revised
Minnesota
modeling
and
the
revised
contributions
to
each
downwind
nonattainment
receptor
county
can
be
found
in
the
CAIR
docket.

The
following
discussion
provides
background
on
the
corrected
emissions
inputs
for
Minnesota
and
on
air
quality
analyses
that
the
Agency
conducted
prior
to
finalizing
CAIR.

The
emissions
for
the
electric
power
sector
used
in
EPA's
contribution
modeling
for
the
final
CAIR
were
derived
from
the
Integrated
Planning
Model
(
IPM).
The
IPM
is
designed
to
forecast
the
projected
impact
of
environmental
polices
on
the
electric
power
sector.
The
Agency
updated
its
IPM
modeling
for
the
final
CAIR.
As
part
of
a
routine
model
update
to
the
IPM
and
in
response
to
comments
from
various
parties,
EPA
updated
the
inventory
of
EGUs,
made
revisions
to
several
model
assumptions,
and
added
various
State
rules,
regulations,
and
New
Source
Review
settlements
to
best
reflect
available
data
and
information.

In
that
IPM
update
for
the
final
CAIR,
the
Agency
included
emission
reduction
actions
that
are
required
by
Minnesota
for
certain
units,
based
on
the
data
available.

However,
as
discussed
in
the
Response
to
Comments
document
(
RTC)
for
the
final
CAIR
("
Corrected
Response
to
Significant
Public
Comments
on
the
Proposed
Clean
Air
Interstate
Rule,"
March
2005,
corrected
April
2005,
OAR­

2003­
0053­
2172)
as
well
as
in
a
memorandum
to
the
CAIR
docket
entitled
"
Emissions
in
Minnesota:
Additional
Analysis"
(
OAR­
2003­
0053­
2091)("
Minnesota
memorandum"),
the
Agency
discovered
that
there
may
be
some
discrepancies
between
how
the
Agency
represented
the
Minnesota
emission
reductions
in
the
final
CAIR
IPM
update
and
how
the
reductions
would
be
implemented.
The
Agency
revised
its
IPM
model
to
better
reflect
the
emission
reductions
from
those
Minnesota
units
and
conducted
revised
emissions
modeling
using
the
IPM
(
in
the
memorandum
mentioned
above
the
revised
emissions
modeling
is
described
as
a
sensitivity
analysis.)
The
revised
emissions
modeling
(
sensitivity
analysis)
resulted
in
somewhat
lower
NOx
and
SO2
emission
projections
for
Minnesota
in
the
base
case,

compared
to
the
emissions
modeling
done
for
the
final
CAIR.

The
revised
emissions
modeling
was
discussed
in
the
RTC
for
the
final
CAIR
and
in
the
Minnesota
memorandum.

Specifically,
that
revised
IPM
modeling
projects
statewide
utility
NOx
emissions
roughly
16,500
tons
lower
and
SO2
emissions
about
5,800
tons
lower
than
the
emissions
modeling
used
in
the
final
CAIR.
These
revised
NOx
and
SO2
emission
projections
result
in
lower
total
NOx
and
SO2
emissions
of
4.6
percent
and
4.3
percent,
respectively,

than
the
emission
projections
used
in
the
final
CAIR
modeling.

In
order
to
account
for
these
revised
emission
projections,

the
Agency
performed
two
analyses
to
estimate
whether
air
quality
modeling
based
on
the
lower
emission
projections
would
show
that
Minnesota's
downwind
contribution
was
below
the
PM2.5
significance
threshold
of
0.2
µ
g/
m3.
The
EPA's
modeling
of
Minnesota
for
the
final
CAIR
showed
that
Minnesota's
maximum
downwind
contribution
is
0.21
µ
g/
m3
to
Cook
County,
Illinois.
The
Agency's
analyses
of
the
effects
of
the
lower
emission
projections
on
Minnesota's
maximum
contribution,
which
were
presented
in
the
RTC
for
the
final
CAIR
and
the
Minnesota
Memorandum,
are
summarized
below:

 
Analysis
1:
We
reduced
the
maximum
PM2.5
contribution
by
the
larger
of
the
percent
reduction
in
NOx
and
SO2
emissions
(
i.
e.,
the
4.6
percent
reduction
in
NOx).
The
maximum
PM2.5
contribution
after
making
this
adjustment
is
0.2
µ
g/
m3.

 
Analysis
2:
We
reduced
the
sulfate
and
nitrate
portions
of
the
maximum
PM2.5
contribution
by
the
corresponding
reductions
in
SO2
and
NOx
emissions.
Specifically,
the
sulfate
portion
(
including
sulfate,
ammonium,
and
particle­
bound
water)
was
reduced
by
the
4.3
percent
reduction
in
SO2
emissions
and
the
nitrate
portion
was
reduced
by
the
4.6
percent
reduction
in
NOx
emissions.

We
then
recalculated
the
maximum
contribution
using
these
lower
components.
The
result
is
that
the
adjusted
maximum
PM2.5
contribution
is
0.2
µ
g/
m3.

Thus,
the
analyses
presented
in
the
RTC
and
the
Minnesota
memorandum
indicate
that
Minnesota
makes
a
significant
contribution
to
PM2.5
nonattainment,
even
after
considering
the
lower
emissions
levels
in
the
revised
emissions
modeling.
1
Although
the
Agency's
analyses
of
downwind
impacts
from
Minnesota
which
were
based
on
the
revised
emissions
modeling
(
and
presented
in
the
RTC
and
the
Minnesota
memorandum)
indicate
that
the
State
makes
a
significant
contribution
to
downwind
PM2.5
nonattainment,
the
Agency
acknowledges
that
it
did
not
at
that
time
conduct
air
quality
modeling
based
on
the
revised
emissions
modeling.

However,
as
discussed
above,
the
Agency
has
now
remodeled
the
PM2.5
contribution
from
emissions
in
Minnesota
and
the
results
of
that
revised
modeling
confirm
that
emissions
in
Minnesota
make
a
significant
contribution
to
PM2.5
nonattainment
in
Chicago,
IL.
This
revised
PM2.5
1
Although
the
petition
acknowledges
that
the
Agency
revised
its
IPM
emissions
analysis
to
reflect
emission
reductions
at
certain
Minnesota
units,
it
states
incorrectly
that
"
EPA
subsequently
learned
that
emission
levels
in
the
IPM
sensitivity
analysis
were
overstated
by
an
additional
16,500
tons
of
annual
NOx
emissions
and
5,800
tons
of
annual
SO2
emissions"
(
petition,
p.
7).
As
discussed
above,
the
emission
projections
in
EPA's
revised
IPM
modeling
(
the
sensitivity
analysis)
were
in
fact
lower
by
16,500
tons
of
annual
NOx
emissions
and
5,800
tons
of
SO2
emissions
than
the
emission
projections
in
EPA's
modeling
for
the
final
CAIR.
For
the
same
reason,
the
petition
is
incorrect
in
stating
(
p.
7)
that
EPA
failed
to
consider
these
emission
reductions
in
its
analysis.
contribution
modeling
used
the
same
modeling
platform
as
EPA
used
for
the
final
CAIR
modeling
coupled
with
the
revised
emissions
inputs
for
Minnesota
discussed
above.

This
modeling
also
includes
revised
inputs
for
the
State
of
Delaware,
based
on
comments
received
in
response
to
our
proposal
to
add
New
Jersey
and
Delaware
to
the
CAIR
region
for
PM2.5
(
70
FR
25408,
May
12,
2005,
docket
ID
OAR­
2003­

0053).
EPA
is
taking
comment
only
on
the
revised
inputs
for
Minnesota
discussed
above.