August
31,
2005
Mr.
Larry
Wallace
Air
Quality
Strategies
and
Standards
Office
of
Air
Quality
Planning
and
Standards
US
EPA,
C504­
02
RTP,
NC
27511
RE:
Comments
on
Staff
Paper
on
Exceptional
and
Natural
Events
for
the
PM
Standards.

Dear
Mr.
Wallace:

Thank
you
for
the
opportunity
to
review
and
comment
on
the
8/
11/
05
draft
Staff
Work
Paper
on
the
Use
of
Air
Quality
Data
Related
to
Exceptional
and
Natural
Events
for
the
Particulate
Matter
Standards.

When
flagging
data,
we
would
prefer
to
have
two
options.
The
first
option
would
be
to
flag
data
for
which
we
would
ask
for
Regional
Office
concurrence.
The
second
option
would
be
to
flag
data,
but
would
not
ask
for
Regional
Office
concurrence.
The
first
option
would
apply
to
data
that
could
affect
the
State
or
National
PM
standards.
For
the
second
option,
the
flags
would
be
for
informational
purposes
only.
These
would
be
cases
where
we
want
to
alert
the
data
users
and
analysts
about
some
abnormal
phenomenon
occurring
during
the
monitoring
period.

The
level
of
documentation
required
to
substantiate
an
exceptional
or
natural
event
should
not
be
so
extensive
that
it
deters
agencies
from
requesting
EPA
concurrence.
The
staff
paper
lists
4
possible
steps:
an
analysis
showing
that
the
measured
value
is
due
to
event,
an
estimation
of
the
portion
of
the
measured
value
that
is
due
to
event,
an
identification
of
the
area
influenced
by
the
event,
and
a
comparison
of
the
historical
data
with
the
measured
value
for
that
site.
These
steps
seem
reasonable,
as
long
as
the
required
documentation
is
not
too
extensive.
Many
State,
local
and
Tribal
agencies
do
not
have
sufficient
resources
to
perform
an
extensive
analysis
for
one
data
point
(
PM
measurement)
and
would
simply
not
request
concurrence
if
the
required
analysis
is
too
burdensome.
It
would
also
be
very
helpful
if
some
examples
of
the
required
analyses
were
included
with
the
final
documentation.

Modeling
is
also
listed
as
a
way
to
determine
the
relative
contribution
of
the
event.
In
our
opinion,
the
only
modeling
that
would
make
sense
would
be
a
trajectory
analysis
used
to
show
the
source(
s)
of
the
emissions
and
the
location(
s)
of
the
impacts.
Quantifying
pollutant
concentrations
downwind
would
be
very
difficult
because
emission
rates
for
exceptional
and
natural
events
are
usually
not
well
known.
Regional
Office
concurrence
policies
should
also
be
consistent
across
all
Regions,
and
the
document
should
include
guidance
for
the
Regional
Office
reviewers
to
follow.
We
believe
that
the
degree
of
public
process
suggested
in
the
staff
paper
is
excessive.
Publishing
the
event
documentation
in
newspapers
and/
or
having
public
hearings
is
more
appropriate
for
regulation
development
or
plan
development.
Simply
flagging
air
quality
data
does
not
constitute
the
same
imperative.
For
this
level,
we
believe
that
posting
the
event
documentation
on
our
web
site
and
requesting
public
comments
would
be
adequate
public
notification.
If
EPA
were
to
publish
its
flagging
concurrences
in
the
Federal
Register,
that
would
also
allow
additional
public
comment.

The
staff
paper
recommends
that
the
only
data
to
be
flagged
would
be
data
that
have
an
impact
on
the
National
annual
or
24­
hour
standards.
California
particulate
standards
are
more
stringent
than
the
national
standards,
and
we
may
wish
to
flag
data
at
levels
above
the
State
standards
but
below
the
national
standards
when
appropriate.

The
staff
paper
recommends
that
the
documentation
be
sent
to
the
EPA
Regional
Office
no
later
than
60
days
following
the
end
of
the
quarter
in
which
the
event
occurred.
We
believe
this
time
period
is
too
short.
Sample
values
are
often
not
available
until
30
days
after
they
are
collected.
An
additional
30
to
60
days
are
needed
to
review
and
edit
the
data
before
inputting
the
data
into
EPA's
AQS
database.
If
the
data
to
be
flagged
were
sampled
near
the
end
of
the
quarter,
State,
local,
and
Tribal
agencies
would
not
have
sufficient
time
to
prepare
the
documentation
required
to
meet
the
60
day
deadline.
A
more
realistic
time
period
would
be
180
days
after
the
end
of
the
quarter.

We
appreciate
the
opportunity
to
make
comments.
If
you
wish
to
discuss
these
comments,
please
call
Dick
Duker
of
my
staff
at
(
415)
749­
4655.

Sincerely
Gary
Kendall
Director,
Technical
Services
Division
