Document ID: EPA-HQ-OAR-2003-0053-2091
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2005-03-10T05:00Z

MEMORANDUM
TO:
Docket
FROM:
EPA
SUBJECT:
Emissions
in
Minnesota:
Additional
Analysis
DATE:
March
9,
2004
Following
the
CAIR
NODA,
Xcel
Energy
made
EPA
aware
of
emission
projections
of
SO
2
and
NO
x
produced
in
support
of
the
CAIR
Notice
of
Proposed
Rulemaking
that
did
not
exactly
reflect
projected
emissions
from
Xcel
units
in
Minnesota
because
of
an
agreement
with
the
State
to
reduce
emissions
from
various
electricity
generating
units
in
the
State
(
the
Metropolitan
Emission
Reduction
Proposal,
or
MERP).
EPA
has
tried
to
be
as
accurate
as
possible
in
its
modeling
underlying
the
CAIR
rule.
Part
of
this
effort,
as
explained
in
detail
in
the
preamble
to
the
final
rule,
was
to
use
the
Integrated
Planning
Model
(
IPM)
for
the
final
rule.
As
part
of
a
routine
model
update
to
IPM
to
best
reflect
available
data
and
information
and
in
response
to
comments
from
various
parties,
EPA
has
updated
the
inventory
of
EGUs,
made
revisions
to
several
model
assumptions,
and
incorporated
latest
emissions
estimates
reflecting
various
State
rules,
regulations,
and
NSR
settlements.
Along
with
new
economic
and
emissions
modeling
reflecting
these
updates,
EPA
has
redone
air
quality
modeling.
These
new
results
are
intended
to
reflect
what
EPA
projects
to
occur
in
the
future
with
and
without
CAIR.

In
evaluating
emissions
contributions
from
Minnesota,
EPA,
as
part
of
the
updated
analysis,
incorporated
the
MERP
which
requires
various
repowerings
and
retrofits
of
Xcel
Energy
units.
EPA
incorporated
these
updates
based
on
available
data.
However,
because
of
an
Xcel
Energy
comment
submitted
for
the
Clean
Air
Interstate
Rule,
EPA
has
discovered
that
there
appears
to
be
some
discrepancies
in
emissions
between
the
MERP
as
agreed
to
by
Xcel
and
Minnesota
and
how
EPA
accounted
for
the
MERP
in
IPM.
The
estimated
difference
in
emissions
in
2010
is
estimated
to
be
lower
by
roughly
16,500
tons
of
NO
x
and
5,800
tons
of
SO
2
when
fully
accounted
for,
based
upon
a
sensitivity
analysis
done
with
the
IPM
v2.1.9
base
case
that
incorporated
the
MERP
as
outlined
by
Xcel
Energy
(
please
see
docket
items
`
Base
Case
2004_
MN
Sensitivity'
and
`
Base
Case
2004_
MN
Sensitivity_
Emissions,'
which
provides
more
detail
regarding
the
analysis
that
EPA
performed).
Nevertheless,
EPA
has
concluded
that
although
differences
appear
to
exist,
they
are
not
large
enough
to
impact
EPA's
test
for
Minnesota's
significant
contribution
to
a
downwind
nonattainment
area,
and
is
therefore
finalizing
CAIR
with
Minnesota
as
part
of
the
program.
Specifically,
EPA
has
incorporated
the
revised
estimates
described
in
the
comment
into
our
data
base
and
reassessed
Minnesota's
contribution
based
on
these
estimates.
Our
conclusion
is
that
Minnesota's
contribution
remains
significant.

Incorporation
of
the
revised
emission
estimates
from
several
Xcel
facilities
in
Minnesota
is
expected
to
result
in
somewhat
lower
2010
Base
Case
NO
x
and
SO
2
emissions
estimates.
Emissions
of
NO
x
are
expected
to
be
roughly
16,500
tons
lower
and
emissions
of
SO
2
are
expected
to
be
5,800
tons
lower
than
EPA
modeled,
according
to
the
aforementioned
EPA
analysis.
These
reductions
translate
into
a
4.6
percent
reduction
in
total
statewide
NO
x
and
a
4.3
percent
reduction
in
total
statewide
SO
2
emissions
in
Minnesota
in
2010.
In
view
of
these
reduced
emissions
estimates,
EPA
performed
two
analyses
to
estimate
whether
the
lower
emissions
estimates
would
drop
Minnesota's
downwind
estimated
contribution
below
the
PM2.5
significance
threshold
of
0.2
µ
g/
m3.
EPA's
zero­
out
modeling
for
Minnesota
without
the
reductions
reflecting
the
Xcel
comment
shows
that
Minnesota's
maximum
contribution
is
0.21
µ
g/
m3
to
Cook
County,
Illinois
(
See
Appendix
H
of
the
CAIR
Final
Air
Quality
Modeling
Technical
Support
Document).
Our
analyses
of
the
effects
of
the
emissions
changes
on
the
maximum
contribution
are
as
follows:

°
Analysis
1:
We
reduced
the
maximum
PM2.5
contribution
by
the
larger
of
the
percent
reduction
in
NO
x
and
SO
2
emissions
(
i.
e.,
the
4.6
percent
reduction
in
NO
x).
The
maximum
PM2.5
contribution
after
making
this
adjustment
is
0.2
µ
g/
m3.

Calculation
of
Impact:
Minnesota's
maximum
contribution
based
on
CAIR
modeling:
0.21
µ
g/
m3
Reduction
of
contribution
by
4.6
percent:
[
0.21
­
(
0.21
x
.046)]
=
0.20
µ
g/
m3
°
Analysis
2:
We
reduced
the
sulfate
and
nitrate
portions
of
the
maximum
PM2.5
contribution
by
the
corresponding
reductions
in
SO
2
and
NO
x
emissions.
Specifically,
the
sulfate
portion
(
including
sulfate,
ammonium,
and
particle­
bound
water)
was
reduced
by
the
4.3
percent
reduction
in
SO
2
emissions
and
the
nitrate
portion
was
reduced
by
the
4.6
percent
reduction
in
NO
x
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.

Calculation
of
Impact:

Modeled
Contribution
(
µ
g/
m3)
Adjustment
Factor
Adjusted
Contribution
(
µ
g/
m3)

Sufate1
0.090
­
4.3
%
0.086
Nitrate
0.120
­
4.6
%
0.114
PM2.5
0.210
NA
0.200
1.
Includes
sulfate
and
associated
particle
bound
water
and
ammonium.

Thus,
our
analyses
indicate
that
Minnesota
makes
a
significant
contribution
to
PM2.5
nonattainment,
even
accepting
and
accounting
for
all
of
the
emissions
reductions
set
out
in
the
Xcel
comments.