NATIONAL
EMISSION
STANDARDS
FOR
HAZARDOUS
AIR
POLLUTANTS
(
NESHAP)
FOR
THE
MERCURY
CELL
CHLOR­
ALKALI
CHLORINE
PRODUCTION
INDUSTRY:

Summary
of
Public
Comments
and
Responses
EPA
453/
R­
03­
012
August
2003
National
Emission
Standards
for
Hazardous
Air
Pollutants
(
NESHAP)
for
the
Mercury
Cell
Chlor­
Alkali
Chlorine
Production
Industry:
Summary
of
Public
Comments
and
Responses
By:
EC/
R
Incorporated
Durham,
North
Carolina
Prepared
for:
Iliam
Rosario
Emission
Standards
Division
Contract
No.
68­
D­
01­
055
Work
Assignment
No.
1­
04
U.
S.
Environmental
Protection
Agency
Office
of
Air
Quality
Planning
and
Standards
Emission
Standards
Division
Metals
Group
Research
Triangle
Park,
North
Carolina
v
Disclaimer
This
report
is
issued
by
the
Office
of
Air
Quality
Planning
and
Standards,
U.
S.
Environmental
Protection
Agency.
Mention
of
trade
names
and/
or
commercial
products
is
not
intended
to
constitute
endorsement
or
recommendation
for
use.
Copies
of
this
report
are
available
free
of
charge
to
Federal
employees,
current
contractors
and
grantees,
and
nonprofit
organizations
 
as
supplies
permit
 
from
the
Library
Services
Office
(
C267­
01),
U.
S.
Environmental
Protection
Agency,
Research
Triangle
Park,
NC
27711,
(
919­
541­
2777)
or,
for
a
nominal
fee,
from
the
National
Technical
Information
Service,
5285
Port
Royal
Road,
Springfield,
Virginia
22161,
(
703­
487­
4650).
vi
vii
ENVIRONMENTAL
PROTECTION
AGENCY
National
Emission
Standards
for
Hazardous
Air
Pollutants
for
the
Mercury
Cell
Chlor­
Alkali
Chlorine
Production
Industry
 
Background
Information
for
Promulgated
Standards
Prepared
by:

_____________________________________
_______________________
Steve
Fruh
(
Date)
Group
Leader,
Metals
Group
Emission
Standards
Division
U.
S.
Environmental
Protection
Agency
Research
Triangle
Park,
NC
27711
1.
The
final
National
Emission
Standards
for
Hazardous
Air
Pollutants
(
NESHAP)
will
regulate
emissions
of
hazardous
air
pollutants
from
mercury
cell
chlor­
alkali
chlorine
production
operations.
Only
those
operations
that
are
part
of
major
sources
under
section
112(
d)
of
the
Clean
Air
Act
as
amended
in
1990
will
be
regulated.

2.
Copies
of
this
document
have
been
sent
to
the
following
Federal
Departments:
Labor,
Health
and
Human
Services,
Defense,
Transportation,
Agriculture,
Commerce,
Interior,
and
Energy;
the
National
Science
Foundation;
and
the
Council
on
Environmental
Quality;
members
of
the
State
and
Territorial
Air
Pollution
Program
administrators;
the
Association
of
Local
Air
Pollution
Control
Officials;
EPA
Regional
Administrators;
and
other
interested
parties.

3.
For
additional
information
contact:

Mr.
Iliam
Rosario
Metals
Group
(
C439­
02)
U.
S.
Environmental
Protection
Agency
Research
Triangle
Park,
NC
27711
Telephone:
(
919)
541­
5430
4.
Paper
copies
of
this
document
may
be
obtained
from:

National
Technical
Information
Services
(
NTIS)
5285
Port
Royal
Road
Springfield,
VA
22161
Telephone:
(
703)
487­
4650
viii
U.
S.
EPA
Library
Services
Office
(
C267­
01)
U.
S.
Environmental
Protection
Agency
Research
Triangle
Park,
NC
27711
5.
Electronic
copies
of
this
document
may
be
obtained
from
the
EPA's
OAR
Technology
Transfer
Network
website
(
TTNWeb).

The
TTNWeb
is
a
collection
of
related
Web
sites
containing
information
about
many
areas
of
air
pollution
science,
technology,
regulation,
measurement,
and
prevention.
The
TTNWeb
is
directly
accessible
from
the
Internet
via
the
World
Wide
Web
at
the
following
address:

http://
www.
epa.
gov/
ttn
ix
TABLE
OF
CONTENTS
1.0
SUMMARY
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1
1.1
BACKGROUND
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1
1.2
SIGNIFICANT
COMMENTS
AND
CHANGES
SINCE
PROPOSAL
.
.
.
.
.
.
.
.
1
2.0
SUMMARY
OF
PUBLIC
COMMENTS
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
7
2.1
GENERAL
COMMENTS
ON
THE
PROPOSED
RULE
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
7
2.2
APPLICABILITY
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
10
2.2.1
Comments
on
Title
V
Permitting
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
10
2.2.2
Comments
Regarding
the
HAP
addressed
by
the
Proposed
Rule
.
.
.
.
.
.
13
2.3
COMPLIANCE
DATE
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
28
2.4
EMISSION
LIMITATIONS
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
29
2.5
WORK
PRACTICE
STANDARDS
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
43
2.5.1
Format
of
Fugitive
Standard
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
43
2.5.2
Comments
on
Work
Practice
Tables
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
49
2.5.3
Cell
room
monitoring
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
58
2.6
TEST
METHODS,
PROCEDURES,
AND
REQUIREMENTS
.
.
.
.
.
.
.
.
.
.
.
.
61
2.7
CONTINUOUS
COMPLIANCE
DEMONSTRATION
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
65
2.8
RECORDKEEPING
AND
REPORTING
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
71
2.9
DEFINITIONS
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
73
2.10
ECONOMIC
AND
BENEFITS
ANALYSIS
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
74
x
1
1.0
SUMMARY
1.1
BACKGROUND
On
July
3,
2002,
the
U.
S.
Environmental
Protection
Agency
(
EPA)
proposed
national
emission
standards
for
hazardous
air
pollutants
(
NESHAP)
for
mercury
emissions
from
mercury
cell
chlor­
alkali
plants
(
67
FR
44672)
under
the
authority
of
section
112
of
the
Clean
Air
Act
(
CAA).
Public
comments
were
requested
on
the
proposal
in
the
Federal
Register.
Six
letters
were
received
from
industry
representatives,
governmental
entities,
and
environmental
groups
during
the
public
comment
period.
A
list
of
the
commenters,
their
affiliations,
and
the
EPA
docket
number
assigned
to
their
correspondence
is
presented
in
table
1­
1.

The
written
comments
that
were
submitted,
along
with
responses
to
these
comments,
are
summarized
in
section
2..
0
of
this
document.
The
summary
of
comments
and
responses
serves
as
the
basis
for
the
revisions
made
to
the
NESHAP
between
proposal
and
promulgation.

1.2
SIGNIFICANT
COMMENTS
AND
CHANGES
SINCE
PROPOSAL
In
response
to
comments
received
on
the
proposed
standards,
several
changes
have
been
made
to
the
final
rule.
While
several
of
these
changes
are
clarifications
designed
to
make
the
Agency's
intent
clearer,
EPA
has
made
a
number
of
more
substantive
changes
to
the
final
rule
in
direct
response
to
comments
received.
A
summary
of
the
changes
made
since
the
proposal
are
described
in
the
following
sections.
Detailed
Agency
responses
to
public
comments
and
the
revised
analysis
for
the
final
rule
are
contained
in
section
2
of
this
document.

The
proposed
rule
contained
a
compliance
date
2
years
from
the
date
that
the
final
rule
would
appear
in
the
Federal
Register.
In
the
final
rule,
the
compliance
date
has
been
changed
to
3
years
from
the
date
of
publication
of
the
final
rule
in
the
Federal
Register.
However,
unlike
the
proposed
rule,
which
would
have
required
that
performance
tests
be
conducted
within
180
days
after
the
compliance
date,
the
final
rule
requires
that
all
performance
tests
be
conducted
on
or
before
the
compliance
date.
2
TABLE
1­
1.
LIST
OF
COMMENTERS
ON
PROPOSED
NATIONAL
EMISSIONS
STANDARDS
FOR
HAZARDOUS
AIR
POLLUTANTS
Docket
Numbera
Commenter
and
Affiliation
IV­
D­
01
Mr.
Arthur
E.
Dungan
Vice
President
­
Safety,
Health
and
Environment
The
Chlorine
Institute,
Inc.
200
l
Street,
N.
W.
Washington,
DC
20036­
4919
IV­
D­
02
Ms.
Cynthia
Sarthou
Executive
Director
Gulf
Restoration
Network
Mr.
Barry
Kohl
Conservation
Chair
Louisiana
Audubon
Council
Ms.
Norma
Gavin
President
League
of
Women
Voters
of
Louisiana
IV­
D­
03
Mr.
David
C.
Foerter
Deputy
Director
Institute
of
Clean
Air
Companies
(
ICAC)
1660
L
Street
NW,
Suite
1100
Washington,
DC
20036­
5603
IV­
D­
04
Mr.
Robert
G.
Smerko
President
The
Chlorine
Institute,
Inc.
Washington,
DC
20036­
4919
IV­
D­
05
Mr.
Samuel
Z.
Chamberlain
Vice
President
Environment,
Health
&
Safety
Pioneer
Americas
LLC
IV­
D­
06
Mr.
Neil
S.
Kagan
Senior
Counsel
National
Wildlife
Federation
213
West
Liberty
Street,
Suite
200
Ann
Arbor,
MI
48104
TABLE
1­
1.
LIST
OF
COMMENTERS
ON
PROPOSED
NATIONAL
EMISSIONS
STANDARDS
FOR
HAZARDOUS
AIR
POLLUTANTS
(
continued)

Docket
Numbera
Commenter
and
Affiliation
3
IV­
D­
07
Mr.
Steven
F.
Faeth
Law
Department
PPG
Industries
Inc.
One
PPG
Place
Pittsburgh,
PA
15272
Comment
Letters
Received
After
the
Close
of
the
Comment
Period
IV­
G­
01
Ms.
Linda
E.
Greer
Senior
Scientist
Mr.
Jon
P.
Devine,
Jr.
Senior
Attorney
Natural
Resources
Defense
Council
IV­
G­
02
Mr.
Jon
P.
Devine,
Jr.
Senior
Attorney
Natural
Resources
Defense
Council
4
For
mercury
cell
chlor­
alkali
production
facilities
affected
sources,
the
proposed
rule
included
a
single
emission
limitation
that
covered
all
mercury
emissions
from
the
two
point
sources
associated
with
chlorine
production
in
mercury
cells:
the
by­
product
hydrogen
stream
and
the
end
box
ventilation
system
vent.
The
format
of
this
limitation
was
total
grams
of
mercury
per
Megagram
of
chlorine
production
(
g
Hg/
Mg
Cl
2).
For
the
initial
compliance
determination,

the
aggregate
mercury
emissions
from
all
hydrogen
by­
product
streams
and
all
end
box
ventilation
system
vents
were
divided
by
the
chlorine
production
for
the
same
period
and
compared
with
the
applicable
emission
limitation.
Continuous
compliance
would
have
then
been
demonstrated
by
continuously
monitoring
the
mercury
concentration
in
each
stream
and
comparing
the
daily
average
mercury
concentration
against
a
level
determined
during
the
initial
compliance
test.

Commenters
objected
to
this
daily
averaging
period
for
compliance
purposes
when
the
emission
limitations
were
based
on
annual
average
emissions
and
chlorine
production.
In
response
to
these
comments,
we
have
written
the
averaging
time
for
continuous
compliance
as
a
52­
week
period.

Further,
as
discussed
more
below,
rather
than
establishing
surrogate
mercury
concentration
operating
limits
for
each
vent,
continuous
compliance
is
determined
by
a
direct
comparison
of
the
emissions
per
unit
of
chlorine
production
(
g
Hg/
Mg
Cl
2)
for
each
52­
week
compliance
period
and
the
emission
limitation.
This
is
a
rolling
average
compliance
period
that
is
determined
each
week.

That
means
a
compliance
determination
is
required
each
week
for
the
previous
52­
week
period.

In
addition
to
the
averaging
time
for
the
by­
product
hydrogen/
end
box
ventilation
system
vent,
we
changed
the
value
of
the
emission
limitation
for
plants
with
end
box
ventilation
systems
from
the
proposed
limit
of
0.067
g
Hg/
Mg
Cl
2
to
0.076
g
Hg/
Mg
Cl
2.
The
proposed
limit
of
0.033
g
Hg/
Mg
Cl
2
for
plants
without
end
box
ventilation
systems
is
retained
in
the
final
rule.

In
the
final
rule,
we
have
written
the
method
for
determining
continuous
compliance
for
the
point
sources
of
emissions
in
both
types
of
affected
sources
covered
by
the
rule
(
by­
product
hydrogen
streams
and
end
box
ventilation
system
vents
at
mercury
cell
chlor­
alkali
production
facilities
and
mercury
thermal
recovery
unit
vents
at
mercury
recovery
facilities).
In
the
proposed
rule,
performance
tests
would
have
been
required
to
determine
initial
compliance
with
the
applicable
emission
limitation.
The
proposed
rule
also
would
have
required
that
the
mercury
concentration
of
each
vent
be
monitored
during
these
performance
tests,
and
that
a
mercury
concentration
operating
limit
be
established
for
each
vent
based
on
the
monitoring
results
5
obtained
during
the
test.
Compliance
with
the
emission
limitation
would
have
then
been
determined
by
comparing
the
results
of
the
continuous
monitoring
of
mercury
concentration
against
the
established
operating
limits.
There
were
several
comments
received
on
this
approach.

In
response
to
these
comments,
continuous
compliance
in
the
final
rule
is
determined
via
a
direct
comparison
of
emissions
to
the
emission
limitation
rather
than
using
mercury
concentration
operating
limits
as
a
surrogate.
For
by­
product
hydrogen
streams
and
end
box
ventilation
system
vents,
the
aggregate
mercury
emissions
will
be
determined,
divided
by
the
corresponding
chlorine
production,
and
compared
with
the
emission
limitation
for
each
52­
week
compliance
period
(
as
discussed
above).
For
mercury
thermal
recovery
unit
vents,
the
measured
mercury
concentration
will
be
directly
compared
against
the
emission
limitations
(
which
are
in
units
of
milligrams
of
mercury
per
dry
standard
cubic
meter,
or
mg/
dscm).
Also,
the
final
rule
contains
two
options
for
measuring
the
mercury
emissions
for
continuous
compliance:
continuous
mercury
emission
monitoring
systems,
and
periodic
sampling
using
EPA
reference
methods
or
approved
alternative
methods.

The
proposed
work
practice
provisions
included
a
cell
room
monitoring
program,
which
would
have
required
that
the
mercury
concentration
be
monitored
in
the
cell
room
and
corrective
action
taken
when
a
plant­
specific
action
level
was
exceeded.
The
final
rule
retains
the
cell
room
monitoring
program,
but
it
is
as
an
alternative
to
the
work
practices.
The
optional
cell
room
monitoring
provisions
in
the
final
rule
are
more
detailed
and
prescriptive
than
the
requirements
in
the
proposed
rule,
and
the
final
rule
requires
the
preparation
and
submittal
of
site­
specific
cell
room
monitoring
plans.
Since
the
cell
room
monitoring
program
was
made
optional,
the
final
rule
requires
(
if
optional
cell
room
monitoring
is
not
chosen)
the
owner
or
operator
to
institute
a
floor­
level
mercury
vapor
measurement
program.
This
program
is
designed
to
limit
the
amount
of
mercury
vapor
in
the
cell
room
environment
through
periodic
measurement
of
mercury
vapor
levels.

The
final
rule
also
requires
that
the
owner
of
each
mercury
cell
chlor­
alkali
plant
report
the
mass
of
virgin
mercury
added
to
the
cells.
Initial
compliance
with
this
requirement
is
demonstrated
by
reporting
the
mass
of
mercury
added
to
cells
for
the
5
years
preceding
the
compliance
date.
This
is
a
requirement
requested
by
commenters.
6
7
2.0
SUMMARY
OF
PUBLIC
COMMENTS
A
total
of
nine
written
comments
were
received
on
the
proposed
standards,
two
of
which
were
received
well
after
the
close
of
the
public
comment
period.
The
following
sections
provide
a
summary
of
these
comments,
as
well
as
the
Agency's
responses
to
these
comments.
For
the
purpose
of
orderly
presentation,
the
comments
have
been
categorized
under
the
following
topics:

°
General
Comments
on
the
Proposed
Rule
°
Applicability
°
Compliance
Date
°
Emission
Limitations
°
Work
Practice
Standards
°
Test
Methods,
Procedures,
and
Requirements
°
Continuous
Compliance
Demonstration
°
Recordkeeping
and
Reporting
°
Definitions
°
Economic
and
Benefits
Analysis
2.1
GENERAL
COMMENTS
ON
THE
PROPOSED
RULE
Comment:
Commenters
IV­
D­
02
and
IV­
D­
03
supported
the
proposed
standards.
One
commenter
(
IV­
D­
02)
noted
that
the
proposed
rule
will
benefit
public
health
and
produce
much
needed
reductions
in
mercury
releases
in
the
State
of
Louisiana
and
nationwide.
Another
commenter
(
IV­
D­
03)
supported
EPA's
basic
reliance
on
proven,
cost
effective,
and
readily
available
air
pollution
control
and
monitoring
technologies.

Response:
We
appreciate
the
commenters'
support
and
are
finalizing
work
on
this
source
category
with
the
goals
of
benefitting
public
health
and
relying
on
proven
technologies
in
mind,
as
well
as
meeting
the
requirements
of
the
CAA.

Comment:
One
commenter
(
IV­
D­
03)
supported
EPA's
emission
limits
as
proposed,

stating
that
such
limits
are
needed
to
achieve
the
emission
reductions
of
1,225
pounds
per
year
relative
to
actual
emissions
and
the
7,500
pounds
per
year
relative
to
potential
emissions
that
would
result
from
a
relatively
few
facilities.
The
commenter
agreed
that
it
is
feasible
and
costeffective
to
achieve
the
proposed
mercury
emission
limits
for
facilities
with
and
without
end­
box
ventilation
systems
using
existing
control
and
upgraded
technologies,
including
new
and
upgraded
installations
of
carbon
adsorbers
and
scrubbers.
Specifically,
the
commenter
supported
EPA's
proposed
conclusions
that
retrofit
control
equipment
is
practical
and
reasonable
and
that
reliance
on
beyond­
the­
floor
control
options
is
warranted.
8
Response:
We
appreciate
the
commenter's
support
and
agree
that
the
application
of
control
technologies
and
the
use
of
work
practice
standards
can
reduce
the
emissions
of
mercury
to
the
environment.

Comment:
A
commenter
that
submitted
comments
after
the
close
of
the
comment
period
(
IV­
G­
01)
believed
that
EPA
missed
the
opportunity
to
eliminate
significant
industrial
mercury
emissions
by
not
banning,
or
even
significantly
reducing,
mercury
emissions
and
they
recommended
that
EPA
re­
define
MACT
to
ban
the
use
of
mercury
cell
technology.
The
commenter
explained
a
ban
of
mercury
cells
would
be
easily
achievable
because
the
majority
of
the
chlorine
production
industry
already
uses
other,
superior
technologies
such
as
membrane
cells
and
diaphragm
cells.
The
commenter
noted
that
the
mercury
cell
chlor­
alkali
industry
is
in
a
demise,
citing
the
fact
that
only
ten
plants
currently
exist,
down
from
30
in
1970,
and
that
these
plants
are
each
approaching
the
end
of
their
useful
life
because
they
were
built
in
the
1960'
s.
The
commenter
further
noted
that
each
company
which
operates
a
mercury
cell
plant
also
produces
chlorine
via
other,
cleaner,
more
efficient
methods.
The
commenter
concluded
that
EPA
should
have
required
a
phase­
out
of
mercury
cell
chlor­
alkali
production
to
expedite
the
elimination
of
mercury
emissions
from
this
industry
rather
than
propose
a
weak
regulation
with
many
gaps
and
loopholes.

The
commenter
asserted
that
there
is
an
urgent
need
to
reduce
the
amount
of
mercury
used
and
released
into
the
environment
because
mercury
is
a
"
notorious
neurotoxin"
which
has
a
particularly
negative
effect
on
the
neurological
development
of
fetuses
and
young
children.
The
commenter
explained
that
methyl
mercury,
which
is
the
most
toxic
form,
is
produced
by
bacteria
from
the
metallic
form
in
which
it
is
typically
emitted
and
that
the
most
significant
route
of
exposure
to
methyl
mercury
is
through
consumption
of
fish
which
have
bioaccumulated
the
toxin
via
the
food
chain.
The
commenter
cited
strong
recommendations
by
various
organizations
that
women
of
childbearing
age
and
children
under
six
years
of
age
should
avoid
certain
seafood,
as
well
as
studies
on
the
relatively
high
amounts
of
methyl
mercury
in
newborns
and
women
of
childbearing
age,
as
examples
of
the
widespread
consensus
that
existing
levels
of
mercury
in
the
environment
pose
serious
harm.

The
commenter
stated
that
EPA
could
still
ban
the
mercury
cell
process
by
setting
MACT
above
the
floor.
The
commenter
estimated
that
a
reasonable
total
cost
for
MACT
which
would
9
still
be
cost­
effective
according
to
EPA
guidelines
would
be
$
1.5
billion,
based
on
an
analysis
of
other
MACT
standards.
The
commenter
estimated
that
the
cost
to
convert
all
mercury
cell
plants
to
other
technologies
would
be
approximately
$
920
million
and
concluded
that
this
above­

thefloor
cost
was
justifiable,
especially
given
the
beneficial
non­
air
quality
health
and
environmental
impacts
that
would
result.

Finally,
the
commenter
cited
a
lack
of
confidence
that
the
mercury
cell
process
could
be
adequately
controlled
as
a
reason
to
ban
the
use
of
the
mercury
cell
process.
The
commenter
explained
that
EPA
had
been
unable
to
accurately
quantify
fugitive
emissions,
which
are
the
largest
source
of
mercury
emissions
from
mercury
cell
chlor­
alkali
plants,
and
consequently
unable
to
issue
a
numerical
emission
limitation.
The
commenter
complained
that
the
work
practice
requirements
which
are
proposed
instead
to
address
fugitive
emissions
are
too
weak
and
rely
on
vague
practices
and
undefined
time
scales.
Taking
into
account
EPA's
insistence
that
these
requirements
could
not
be
changed,
the
commenter
concluded
that
the
proposed
rule
offered
very
limited
protection
of
public
health
and
the
environment.

Response:
While
the
facts
cited
by
the
regarding
the
demise
of
the
mercury
cell
chloralkali
industry
are
correct,
we
disagree
with
the
with
their
arguments
that
the
rule
should
ban
mercury
cell
chlor­
alkali
plants.
We
do
believe,
however,
that
the
final
rule
contains
a
means
of
"
phasing
out"
mercury
cell
technology
by
not
allowing
prohibiting
mercury
emissions
from
new
or
reconstructed
sources.
This
effectively
bans
the
construction
of
new
mercury
cell
plants,
as
well
as
the
reconstruction
of
existing
mercury
cell
plants.

We
agree
with
the
commenter's
evaluation
of
the
health
effects
of
mercury.
However,

these
significant
effects
do
not
provide
a
legal
justification
for
banning
all
mercury
cell
chlor­
alkali
plants
under
section
112(
d).

We
do
not
believe
that
the
commenter's
point
that
the
mercury
cell
process
should
be
banned
because
it
is
cost
effective
to
do
so
is
entirely
accurate.
First,
the
commenter
did
not
provide
any
basis
for
their
cost
estimates
so
we
could
not
verify
these
costs.
Further,
we
do
not
believe
that
"
conversion"
accurately
describes
the
replacement
of
a
mercury
cell
plant
to
another
technology.
There
is
little
salvageable
from
a
mercury
cell
plant
that
can
be
used
in
the
construction
of
a
membrane
cell
plant,
so
the
demolition
of
the
mercury
cell
plant
followed
by
the
construction
of
a
membrane
cell
plant
is
a
more
accurate
characterization.
10
We
believe
the
commenter's
final
argument
is
not
supported
by
the
statutory
authority
provided
in
section
112(
d)(
2),
which
is
the
basis
for
the
final
rule.
In
general,
section
112(
d)(
2)

requires
that
level
of
control
for
the
entire
industry
be
established
based
on
the
best
controlled
facilities.
The
fact
that
there
is
there
is
inadequate
control
would
lead
to
less
stringent,
not
more
stringent,
standards.
We
do
acknowledge
that
we
are
unable
to
issue
a
numerical
emission
limitation
for
fugitive
emissions,
as
discussed
in
section
2.5.1.
However,
we
disagree
that
the
work
practice
standards
are
too
weak
and
rely
on
vague
practices
and
undefined
time
scales.

Rather,
we
believe
that
they
will
be
effective
practices
to
identify
and
correct
sources
of
fugitive
mercury
emissions.

In
conclusion,
we
did
not
take
the
commenter's
suggestion
and
ban
the
use
of
mercury
cell
technology.
We
believe
that
the
final
rule
will
achieve
real
reductions
in
mercury
emissions
and
will
provide
public
health
and
environmental
benefits.

2.2
APPLICABILITY
2.2.1
Comments
on
Title
V
Permitting
Comment:
Three
commenters
(
IV­
D­
04,
IV­
D­
05,
IV­
D­
07)
disagreed
with
the
proposed
requirements
for
all
mercury
cell
chlor­
alkali
plants
to
obtain
a
title
V
permit,
including
area
sources.
The
commenters
requested
that
this
provision
be
deleted
from
the
final
rule.
The
commenters
stated
that
most
facilities
affected
by
the
proposal
are
minor
sources
of
HAP
emissions
and
maintained
that
requiring
minor
source
facilities
to
obtain
title
V
permits
would
impose
a
burdensome
paperwork
requirement
(
including
duplicative
reporting
and
recordkeeping)

that
would
yield
no
environmental
benefit.
According
to
commenter
IV­
D­
05,
dropping
the
title
V
permit
requirement
would
not
lessen
any
substantive
requirements
for
monitoring,

recordkeeping,
or
operation
of
any
and
all
air
pollution
control
devices.
Commenters
IV­
D­
04
and
IV­
D­
07
noted
that
the
CAA
allows
EPA
to
exempt
certain
sources
from
obtaining
a
title
V
permit
".
.
.
if
the
Administrator
finds
that
compliance
with
such
requirements
is
impracticable,

infeasible,
or
unnecessarily
burdensome
.
.
.."

Commenter
IV­
D­
07
noted
that
in
previously
promulgated
area
source
MACT
standards
(
e.
g.,
Dry
Cleaning
MACT
and
Halogenated
Solvent
Cleaning
MACT),
EPA
identified
area
sources
as
being
subject
to
title
V
permitting.
However,
EPA
allowed
the
permitting
authorities
to
defer
area
sources
from
title
V
permitting
requirements
until
December
9,
2004.
11
In
contrast,
Commenter
IV­
G­
1
(
which
submitted
comments
after
the
close
of
the
comment
period)
supported
the
proposed
requirement
to
require
all
affected
sources
to
obtain
title
V
permits.
The
commenter
argued
that
title
V
permits
are
needed
because
they
consolidate
sources'
applicable
requirements
in
a
single
place.
The
commenter
further
noted
that
".
.
.
given
the
detailed
work
practice
requirements,
it
is
reasonable
to
expect
significant
source­
specific
tailoring
of
the
standard
for
each
plant's
individual
configuration."
See,
e.
g.,
67
FR
44706­
07.

The
commenter
also
stated
that
requiring
title
V
permits
of
area
sources
of
mercury
is
especially
appropriate
because
a
small
quantity
of
mercury
is
as
toxic
as
a
far
greater
amounts
of
other
HAP.

Response:
Section
502(
a)
of
the
CAA
requires
any
source,
including
an
area
source,

subject
to
standards
or
regulations
under
section
112
of
the
CAA
to
operate
in
compliance
with
a
title
V
permit
after
the
effective
date
of
any
title
V
permits
program.
Section
502(
a)
states
that
the
Administrator
may
promulgate
regulations
to
exempt
one
or
more
source
categories,
in
whole
or
in
part,
from
the
requirements
of
the
section
if
the
Administrator
finds
that
compliance
with
title
V
requirements
is
impracticable,
infeasible,
or
unnecessarily
burdensome
on
such
categories.

The
Administrator
may
not
exempt
any
major
source
from
the
requirements
of
title
V.

Three
commenters
disagreed
that
area
sources
under
the
final
rule
should
be
required
to
obtain
title
V
permits.
In
order
to
exempt
area
sources
under
the
final
rule
from
title
V
requirements,
the
test
in
section
502(
a)
of
the
CAA
must
be
met.
Specifically,
the
Administrator
must
make
a
finding
that
title
V
requirements
are
impracticable,
infeasible,
or
unnecessarily
burdensome
for
the
source
category
or
categories
in
question.
Commenters
may
provide
data
which
would
help
the
Administrator
make
such
a
finding,
but
the
commenters
who
were
opposed
to
area
sources
being
permitted
under
the
final
rule
did
not
provide
any
such
data.
Commenters
providing
supporting
data
for
their
arguments
is
consistent
with
what
the
Agency
stated
in
its
final
rule
for
the
Municipal
Solid
Waste
Landfills
NESHAP
in
reference
to
the
test
in
section
502(
a)
of
the
CAA:
"
If
commenters
choose
to
try
and
meet
this
test
when
commenting
on
a
proposed
section
111
or
112
standard,
they
must
submit
comments
which
document
in
detail
the
ways
in
which
the
title
V
requirements
are
impracticable,
infeasible,
or
unnecessarily
burdensome
for
the
source
category
in
question."
(
See
footnote
1
68
FR
2227,
2234,
January
16,
2003).

In
terms
of
the
commenters'
concern
about
title
V
adding
duplicative
recordkeeping
and
reporting
requirements,
the
only
potential
duplicative
requirement
that
we
are
aware
of
is
in
12
relation
to
deviation
reporting
under
the
semiannual
compliance
report
required
by
§
63.8254
of
the
final
rule
and
the
semiannual
monitoring
report
required
by
40
CFR
70.6(
a)(
3)(
iii)(
A)
or
40
CFR
71.6(
a)(
3)(
iii)(
A).
However,
this
potential
duplication
was
addressed
by
§
63.8254(
d)
in
the
proposed
rule
and
this
has
been
clarified
in
the
final
rule.

As
to
the
deferral
for
area
sources
subject
to
the
Dry
Cleaning
MACT
and
the
Halogenated
Solvent
Cleaning
MACT,
the
area
sources
subject
to
these
MACT
standards
were
deferred
from
title
V
permitting
until
December
9,
2004
(
64
FR
69637,
December
14,
1999).

This
deferral
was
granted
in
part
because
of
the
concern
that
area
sources
would
not
be
able
to
obtain
the
technical
and
procedural
assistance
from
permitting
authorities
needed
to
file
timely
and
complete
title
V
applications
given
that
permitting
authorities
would
be
focused
on
the
permitting
of
major
sources.
However,
as
the
title
V
program
is
no
longer
in
its
initial
stages
and
the
initial
permitting
of
existing
major
sources
is
nearing
completion,
we
would
not
be
justified
in
granting
a
deferral
to
area
under
the
final
rule
for
the
same
reason.

In
terms
of
the
commenter
who
supported
the
permitting
of
affected
sources
under
the
final
rule,
we
agree
that
the
consolidation
of
requirements
in
a
title
V
permit
is
one
of
the
ways
that
title
V
helps
assure
compliance
with
all
applicable
requirements.
As
this
commenter
also
pointed
out,
title
V
permits
clarify
which
requirements
in
standards
apply
to
a
source
where
requirements
may
vary
due
to
various
factors,
e.
g.,
design
of
the
facility.
Additionally,
the
title
V
regulations
at
40
CFR
part
70
and
40
CFR
part
71
help
a
source
assure
compliance
with
its
applicable
requirements
by
requiring
that
a
source
self­
certify
to
compliance
initially
and
annually,

by
requiring
that
a
source
promptly
report
deviations
from
its
permit
requirements,
and
by
requiring
that
a
permit
contain
monitoring
requirements.
It
is
also
important
to
note
that
the
title
V
permitting
process
provides
an
opportunity
for
the
public
to
comment
on
whether
a
source
is
complying
with
its
applicable
requirements.
In
short,
title
V
permits
can
enhance
the
effectiveness
of
rules
such
as
the
final
rule,
and
EPA,
therefore,
disagrees
that
there
are
no
environmental
benefits
to
requiring
title
V
permits
for
area
sources.

In
conclusion,
as
the
test
in
section
502(
a)
of
the
CAA
has
not
been
met,
EPA
has
retained
the
requirement
in
the
final
rule
that
affected
sources
subject
to
the
final
rule
must
obtain
title
V
permits.
Therefore,
whether
an
affected
source
under
the
final
rule
is
a
part
of
a
major
or
area
source,
the
major/
area
source
is
required
to
obtain
a
title
V
permit.
13
2.2.2
Comments
Regarding
the
HAP
addressed
by
the
Proposed
Rule
We
divided
the
chlorine
production
category
into
two
subcategories:
mercury
cell
chloralkali
plants,
and
chlorine
production
plants
that
do
not
rely
upon
mercury
cells
for
chlorine
production
(
diaphragm
cell
chlor­
alkali
plants,
membrane
cell
chlor­
alkali
plants,
etc).
On
July
3,

2002,
we
issued
separate
proposals
to
address
the
emissions
of
mercury
from
the
mercury
cell
chlor­
alkali
plant
subcategory
sources
(
67
FR
44672)
and
the
emissions
of
chlorine
and
HCl
from
both
the
non­
mercury
cell
chlorine
production
subcategory
sources
and
the
mercury
cell
chloralkali
subcategory
sources
(
67
FR
44713).
Specifically,
we
proposed
a
rule
for
mercury
emissions
from
mercury
cell
chlor­
alkali
plants,
and
we
proposed
not
to
regulate
chlorine
and
HCl
emissions
from
mercury
cell
chlor­
alkali
plants
and
non­
mercury
cell
chlorine
production
plants
under
our
authority
in
section
112(
d)(
4)
of
the
CAA.

Comments
were
received
regarding
the
proposed
action
not
to
regulate
chlorine
and
HCl
emissions
(
see
Air
Docket
OAR­
2002­
0016
or
Air
Docket
A­
2002­
09).
The
aspects
of
these
comments
related
to
the
mercury
cell
chlor­
alkali
plant
subcategory
can
be
generally
classified
into
two
basic
categories:
our
statutory
authority
under
section
112(
d)(
4);
and
the
site­
specific
risk
assessments
that
formed
the
basis
for
our
decision.

2.2.2.1
Comments
Related
to
the
Section
112(
d)(
4)
Authority
Comment:
Several
comments
were
received
related
to
our
decision
not
to
regulate
chlorine
and
HCl
emissions
from
chlorine
production
under
the
authority
of
section
112(
d)(
4).

Some
commenters
supported
this
decision
and
stated
the
interpretation
of
our
authority
under
section
112(
d)(
4)
was
appropriate
and
supported
by
the
legislative
history.
In
contrast,
other
commenters
disagreed
with
EPA's
interpretation
of
section
112(
d)(
4).
Finally,
some
of
the
commenters
stated
that
EPA
should
use
its
authority
under
section
112(
c)(
9)(
B)(
ii).

Five
commenters
(
IV­
D­
01,
IV­
D­
02,
IV­
D­
03,
IV­
D­
04,
IV­
D­
05)
supported
EPA's
decision
not
to
regulate
chlorine
and
HCl
emissions
from
non­
mercury
cell
chlorine
production
plants
under
the
authority
of
section
112(
d)(
4).
One
commenter
(
IV­
D­
01)
stated
that
EPA
conducted
an
appropriate
analysis
to
determine
that
human
exposures
from
ambient
concentrations
are
well
below
threshold
values
with
an
ample
margin
of
safety.
According
to
another
commenter
(
IV­
D­
04),
any
further
regulation
of
chlorine
and
HCl
emissions
from
the
chlorine
production
industry
would
have
no
environmental
benefits,
but
would
result
in
costs
for
14
monitoring,
recordkeeping,
and
reporting
efforts
to
certify
compliance
with
any
requirements.

The
commenter
(
IV­
D­
04)
was
concerned
that
a
regulation
would
also
stretch
EPA's
limited
resources
in
monitoring
for
compliance.
Three
commenters
(
IV­
D­
02,
IV­
D­
03,
IV­
D­
05)
stated
that
EPA's
interpretation
of
their
authority
under
section
112(
d)(
4)
was
supported
by
the
legislative
history,
which
emphasizes
that
Congress
included
section
112(
d)(
4)
in
the
CAA
to
prevent
unnecessary
regulation
of
source
categories.
One
commenter
(
IV­
D­
02)
agreed
that
under
section
112(
d)(
4),
once
EPA
establishes
that
a
pollutant
has
a
health
threshold
and
that
exposure
to
that
pollutant's
emissions
are
below
the
health
threshold,
EPA
should
refrain
from
setting
MACT
standards
for
that
pollutant.
The
commenter
further
suggested
that
EPA
should
use
section
112(
d)(
4)
whenever
setting
emission
standards
under
section
112(
d).

Three
commenters
(
IV­
D­
06,
IV­
D­
07,
and
IV­
D­
08)
disagreed
with
EPA's
interpretation
of
section
112(
d)(
4).
They
did
not
believe
that
section
112(
d)(
4)
could
be
used
as
an
alternative
to
setting
MACT
standards
under
section
112(
d)(
3).
One
commenter
(
IV­
D­
06)
noted
that
the
phrase
"
in
lieu
of"
was
not
included
in
the
section
112(
d)(
4)
provisions
and
that
its
absence
was
intentional.
In
support
of
their
claim,
the
commenter
pointed
to
section
112(
d)(
5),
which
does
contain
the
phrase
"
in
lieu
of."
The
commenter
(
IV­
D­
06)
interpreted
section
112(
d)(
4)
to
mean
that
health­
based
thresholds
can
be
considered
when
establishing
the
degree
of
MACT
requirements,
but
not
in
place
of
the
requirement
to
establish
a
MACT
floor
pursuant
to
section
112(
d)(
3).

The
commenter
(
IV­
D­
06)
also
pointed
to
the
provisions
of
section
112(
c)(
2)
which
require
the
Administrator
to
establish
NESHAP
for
listed
source
categories
and
subcategories.

The
commenter
was
concerned
that
EPA
evaluated
emissions
from
chlorine
production
plants
and
concluded
that
since
they
do
not
pose
a
threat
to
human
health
and
the
environment,
the
Administrator
is
relieved
of
her
responsibilities
to
establish
a
MACT
standard.
The
commenter
maintained
that
this
position
is
not
supported
by
section
112(
c)(
2).

The
commenter
also
referred
to
section
112(
d)(
1),
stating
that
EPA
did
not
have
the
authority
to
"
make
a
determination
of
no
regulation
for
a
listed
source
category
or
pollutant."

Finally,
the
commenter
referred
to
section
112(
d)(
3),
which
contains
the
MACT
floor
provisions.
According
to
the
commenter,
the
intent
of
the
NESHAP
program
is
to
develop
a
MACT
floor,
and
EPA
is
not
fulfilling
the
requirements
of
the
CAA
by
not
performing
such
an
15
analysis.
The
commenter
stated
that
a
majority
of
facilities
identified
in
the
analysis
have
adequate
controls
due
to
State
regulations
and
these
controls
should
be
incorporated
into
the
MACT
floor
evaluation.
The
commenter
was
particularly
concerned
that
by
not
developing
a
MACT
floor,
no
new­
source
MACT
standards
were
created.
The
commenter
requested
that
EPA
perform
a
MACT
floor
analysis
and
develop
a
NESHAP
for
new
sources.

Two
of
the
commenters
(
IV­
D­
03,
IV­
D­
05)
stated
that
EPA
should
support
its
decision
not
to
regulate
the
chlorine
production
source
category
by
citing
the
provisions
of
section
112(
c)(
9)(
B)(
ii)
in
addition
to
the
provisions
of
section
112(
d)(
4).
The
commenters
stated
that
the
evaluation
performed
by
EPA
would
also
be
sufficient
for
deleting
sources
under
section
112(
c)(
9)(
B)(
ii)
and
that
EPA's
proposal
to
not
regulate
chlorine
production
is
similar
to
deleting
a
subcategory
of
the
Chlorine
Production
source
category.
Therefore,
in
addition
to
using
the
authority
under
section
112(
d)(
4),
the
commenters
suggested
that
EPA
delete
the
subcategory
using
the
authority
under
section
112(
c)(
9)(
B)(
ii)
to
avoid
any
uncertainty
over
the
use
of
its
authority
under
section
112(
d)(
4).

Response:
The
EPA
has
the
authority
under
CAA
section
112(
d)(
4)
to
decide
not
to
establish
a
NESHAP
for
chlorine
and
HCl
emissions
from
certain
chlorine
production
facilities.

We
have
decided
to
limit
our
use
of
section
112(
d)(
4)
to
the
emissions
of
chlorine
and
HCl
from
sources
within
the
mercury
cell
chlor­
alkali
subcategory.
While
we
have
decided
to
establish
no
standards
for
the
emissions
of
these
two
HAP
from
sources
in
the
mercury
cell
chlor­
alkali
plant
subcategory,
we
are
establishing
standards
for
the
mercury
emissions
from
the
sources
within
that
subcategory.
As
explained
elsewhere
in
today's
Federal
Register,
we
have
decided
to
delete
the
non­
mercury
cell
chlorine
production
plants
subcategory
under
CAA
section
112(
c)(
9)(
B)(
ii).

The
only
HAP
emitted
by
the
non­
mercury
cell
chlorine
production
sources
are
chlorine
and
HCl.

Contrary
to
other
commenters
claims
that
our
use
of
section
112(
d)(
4)
is
inappropriate,

both
the
statutory
language
and
the
legislative
history
of
the
provision
support
our
decision
not
to
set
limitations
for
chlorine
and
HCl
emissions
from
sources
in
the
mercury
cell
chlor­
alkali
plant
subcategory.
The
language
of
section
112(
d)(
4)
provides
the
Agency
with
ample
discretion
to
utilize
a
risk­
based
approach
in
determining
whether
to
establish
emission
standards
for
those
HAP
where
we
determine
that
the
HAP
are
"
threshold
pollutants"
and
that
the
standard
(
or
no
standard)
will
achieve
an
"
ample
margin
of
safety."
16
The
statutory
language
in
section
112(
d)(
4)
is
ambiguous.
Thus,
under
the
Supreme
Court's
decision
in
Chevron
v.
NRDC,
467
U.
S.
837
(
1984),
the
Agency
has
the
discretion
to
interpret
the
language
to
allow
us
to
establish
NESHAP
that
do
set
limitations
on
certain
HAP
emitted
from
sources
("
when
establishing
standards")
but
to
also
decide
not
to
set
limitations
on
other
HAP
emitted
from
these
same
sources
if
the
other
HAP
are
threshold
pollutants
and
the
risk
from
the
emissions
are
so
low
that
no
standard
for
that
second
set
of
HAP
is
necessary
to
protect
the
public
and
the
environment
with
"
an
ample
margin
of
safety."

This
approach
is
consistent
with
prior
decisions
EPA
has
made
in
the
context
of
two
other
NESHAP.
First,
in
the
NESHAP
for
combustion
sources
at
pulp
mills
(
40
CFR
part
63,
subpart
MM),
we
chose
not
to
set
a
standard
for
HCl
emissions
from
recovery
furnaces,
while
we
did
set
standards
for
other
HAP
emitted
from
the
same
sources
within
the
category.
We
explained
this
decision
in
the
preamble
to
the
proposed
MACT
standard
and
received
no
adverse
comment
on
the
approach
(
63
FR
18754,
18765­
68,
April
15,
1998).
Second,
we
proposed
to
set
no
standard
under
section
112(
d)(
4)
for
HCl
emitted
from
lime
kilns,
while
we
also
proposed
to
set
standards
for
other
HAP
emitted
by
these
same
sources
(
67
FR
78046
December
20,
2002).
We
also
received
no
adverse
comment
on
that
proposed
decision.
While
we
originally
proposed
to
utilize
section
112(
d)(
4)
to
set
no
standard
for
chlorine
and
HCl
from
chlorine
production
sources
in
a
separate
notice
of
the
Federal
Register
(
67
FR
44713,
July
3,
2002),
we
made
it
clear
that
the
proposed
use
of
section
112(
d)(
4)
would
apply
to
emissions
of
these
two
HAP
from
mercury
cell
chlor­
alkali
sources
(
as
well
as
the
emissions
of
chlorine
and
HCl
from
other
chlorine
production
sources).

We
do
not
agree
that
Congress'
use
of
the
phrase
"
in
lieu
of"
in
CAA
section
112(
d)(
5)
so
clearly
restricts
any
possible
interpretation
of
CAA
section
112(
d)(
4)
such
that
some
form
of
a
MACT
standard
must
always
be
set
even
when
the
criteria
of
section
112(
d)(
4)
are
met.
Instead,

we
interpret
that
Congress
enacted
section
112(
d)(
4)
to
provide
EPA
with
the
discretion
to
take
risk
into
account
and
decide
that
standards
need
not
be
set
when
the
HAP
are
threshold
pollutants
and
levels
being
emitted
are
below
the
threshold
value
with
an
ample
margin
of
safety.
Moreover,

in
each
case
where
we
have
exercised
authority
under
section
112(
d)(
4),
we
have
established
standards
in
each
category
(
or
subcategory,
as
here)
for
those
pollutants
that
do
not
satisfy
the
threshold
pollutant
and
ample
margin
of
safety
statutory
criteria.
17
We
also
disagree
with
the
commenter
who
argued
that
the
provision
in
section
112(
c)(
2),

which
requires
the
Administrator
to
establish
emission
standards
for
listed
categories
and
subcategories,
has
much
bearing
on
our
use
of
section
112(
d)(
4)
in
this
circumstance.
By
setting
a
standard
for
the
emission
of
mercury
from
the
mercury
cell
chlor­
alkali
plant
subcategory,
we
are
fulfilling
our
obligations
under
section
112(
c)(
2).
As
stated
earlier,
we
have
utilized
the
same
approach
in
our
other
uses
of
section
112(
d)(
4),
e.
g.,
HCl
emissions
from
combustion
sources
at
pulp
mills
and
lime
production
sources.

The
statutory
language
in
section
112(
d)(
1)
and
(
3)
does
not
prevent
us
from
deciding
that
no
emission
standard
is
necessary
for
a
particular
threshold
pollutant
which
is
being
emitted
at
levels
well
below
the
ample
margin
of
safety
when
we
are
also
establishing
standards
for
HAP
emitted
from
sources
in
that
same
category
or
subcategory.
This
approach
to
our
use
of
section
112(
d)(
4)
is
consistent
with
the
statutory
language
of
section
112(
d)(
1)
and
(
3).
We
are
establishing
emission
standards
for
the
listed
category
or
subcategory,
but
are
deciding
that
no
MACT
floor
need
be
established
and
no
emission
standard
set
for
those
HAP
that
meet
the
criteria
of
"
threshold
pollutant"
and
"
ample
margin
of
safety."

With
regard
to
the
concerns
the
commenter
raised
about
the
failure
to
set
a
standard
for
new
sources,
our
review
of
the
mercury
cell
subcategory
indicates
that
no
new
mercury
cell
chloralkali
plants
will
be
constructed.
Given
that
our
emission
standard
for
new
sources
in
the
mercury
cell
chlor­
alkali
subcategory
prohibits
the
emission
of
mercury,
we
do
not
believe
any
new
sources
using
mercury
cells
for
chlorine
production
will
ever
be
constructed
(
or
reconstructed).

Therefore,
this
no­
mercury
emissions
requirement
in
the
final
rule
will,
in
effect,
also
ensure
that
there
are
no
chlorine
or
HCl
emissions
from
new
mercury
cell
facilities.

In
response
to
other
commenters'
suggestion
that
we
utilize
the
authority
of
section
112(
c)(
9)(
B)(
ii)
to
delete
the
chlorine
production
category,
we
have
decided
to
exercise
our
authority
under
that
statutory
provision
for
the
non­
mercury
cell
chlorine
production
subcategory.

That
decision
is
discussed
in
a
separate
notice
in
today's
Federal
Register.
However,
we
are
not
deleting
the
mercury
cell
chlor­
alkali
plant
subcategory
because
the
sources
within
the
category
also
emit
mercury,
and
we
are
establishing
emissions
standards
for
mercury
emissions
in
today's
final
rule.
18
Comment:
Some
commenters
(
IV­
D­
07,
IV­
D­
08)
concluded
that
we
did
not
establish
either
cancer
or
noncancer
thresholds
for
HCl
and
chlorine
and,
therefore,
it
is
illegal
for
EPA
to
attempt
to
use
section
112(
d)(
4)
to
set
standards.

Response:
The
"
threshold
level"
in
section
112(
d)(
4)
refers
to
the
level
of
concentration
of
a
chemical
under
which
no
health
effects
are
expected
from
exposure,
although
this
term
is
not
defined
in
section
112.
Further,
section
112
does
not
address
the
process
that
must
be
followed
to
"
establish"
a
threshold
level.

The
reference
concentration
(
RfC)
is
a
"
long­
term"
threshold,
defined
as
an
estimate
of
a
daily
inhalation
exposure
that,
over
a
lifetime,
would
not
likely
result
in
the
occurrence
of
noncancer
health
effects
in
humans.
We
have
determined
that
the
RfC
for
HCl
of
20
micrograms
per
cubic
meter
(

g/
m3)
is
an
appropriate
threshold
value
for
assessing
risk
to
humans
associated
with
exposure
to
HCl
through
inhalation
http://
www.
epa.
gov/
iris/
subst/
0396.
htm).

In
cases
where
we
have
not
studied
a
chemical
itself,
we
rely
on
the
studies
of
other
governmental
agencies,
such
as
the
Agency
for
Toxic
Substances
and
Disease
Registry
(
ATSDR)

or
the
Office
of
Health
Hazard
Assessment
of
California's
Environmental
Protection
Agency
(
CAL
EPA),
for
RfC
values.
The
CAL
EPA
developed
an
RfC
value
of
0.2

g/
m3
for
chlorine
based
on
a
large
inhalation
study
with
rats.

Acute
exposure
guideline
level
(
AEGL)
toxicity
values
are
estimates
of
adverse
health
effects
due
to
a
single
exposure
lasting
8
hours
or
less.
The
confidence
in
the
AEGL
(
a
qualitative
rating
or
either
low,
medium,
or
high)
is
based
on
the
number
of
studies
available
and
the
quality
of
the
data.
Consensus
toxicity
values
for
effects
of
acute
exposures
have
been
developed
by
several
different
organizations,
and
we
are
beginning
to
develop
such
values.
A
national
advisory
committee
organized
by
EPA
has
developed
AEGL's
for
priority
chemicals
for
30­
minute,
1­
hour,
4­
hour,
and
8­
hour
airborne
exposures.
They
have
also
determined
the
levels
of
these
chemicals
at
each
exposure
duration
that
will
protect
against
discomfort
(
AEGL1),

serious
effects
(
AEGL2),
and
life­
threatening
effects
or
death
(
AEGL3).
Hydrogen
chloride
has
been
assigned
AEGL
values
(
65
FR
39264,
June
23,
2000),
including
the
1­
hour,
AEGL1
of
2,700

g/
m3
used
in
our
revised
analysis.
Chlorine
has
also
been
assigned
AEGL
values
(
62
FR
58840),
including
the
1­
hour
AEGL1
of
1,500

g/
m3
used
in
our
revised
analysis.
19
We
maintain
that
the
listing
of
health
thresholds
by
EPA
and
other
organizations
in
the
public
domain
as
discussed
above
has
"
established"
health
thresholds
for
HCl
and
chlorine.

Further,
the
recognition
of
these
levels
by
EPA,
ASTDR,
and
CAL
EPA
indicates
that
chlorine
and
HCl
are
threshold
pollutants.

Moreover,
we
provided
the
public
an
opportunity
to
comment
on
the
thresholds
for
chlorine
and
HCl
that
we
used
in
our
original
analysis
for
the
proposed
action
(
67
FR
44716).

We
used
the
same
threshold
level
for
HCl
for
both
the
proposed
and
final
NESHAP
for
the
pulp
and
paper
mill
category.
We
have
also
used
the
same
threshold
for
HCl
in
the
proposed
and
final
NESHAP
for
lime
production
(
67
FR
78046;
final
action
is
anticipated
in
August
2003).
There
is
no
requirement
in
section
112(
d)(
4)
that
EPA
develop
or
finalize
a
threshold
for
a
particular
HAP
in
a
certain
manner.
The
thresholds
we
have
used
for
both
HCl
and
chlorine
are
consistent
with
the
statutory
language
in
section
112(
d)(
4).

2.2.2.2
Comments
Related
to
the
Risk
Assessment
Comment:
In
the
analysis
for
the
proposed
action
(
67
FR
44713),
we
used
the
HCl
RfC
to
determine
the
long­
term
health
effects
of
chlorine
emissions,
since
chlorine
photolyzes
very
quickly
to
HCl
in
sunlight.
Two
commenters
(
IV­
D­
03,
IV­
D­
05)
supported
this
methodology
and
stated
that
our
decision
was
based
on
sound
scientific
knowledge
of
the
pollutants
of
concern.

In
contrast,
two
other
commenters
(
IV­
D­
06,
IV­
D­
07)
did
not
agree
with
our
use
of
the
HCl
RfC
as
a
threshold
level
for
chlorine.
The
commenters
stated
that
not
all
of
the
annual
chlorine
emissions
can
be
considered
as
HCl
and,
therefore,
the
chlorine
exposure
was
underestimated.
The
commenters
argued
that
chlorine
emissions
will
not
undergo
photolysis
to
convert
to
HCl
when
there
is
not
bright
sunshine
(
i.
e.,
at
night
or
on
cloudy
days).

Response:
The
widely
accepted
fact
that
chlorine
is
photolyzed
in
sunlight
formed
the
basis
for
the
assumption
in
the
original
risk
assessment
that
chronic
exposure
to
chlorine
would
not
occur.
As
a
result
of
this
comment,
we
re­
examined
the
literature
on
the
atmospheric
fate
of
chlorine
to
validate
our
original
assumption.

The
additional
information
obtained
from
the
literature
confirmed
our
earlier
information.

There
are
several
different
pathways
that
molecular
chlorine
can
take,
including
photolysis
(
reaction
with
light),
reactions
with
hydroxyl
radicals,
reactions
with
oxygen
atoms,
and
reactions
with
water
vapor.
Each
pathway
results
in
different
amounts
of
Cl
2
being
removed
from
the
20
troposphere,
and
different
pathways
are
predominant
at
different
times
of
the
day.
However,

photolysis
is
the
primary
pathway.

Therefore,
this
information
did
not
fundamentally
change
the
assumption
made
in
the
original
risk
assessment,
which
was
that
on
a
long­
term
basis,
individuals
will
be
exposed
more
to
HCl
formed
from
the
photolysis
of
chlorine
than
to
chlorine.
However,
the
commenters
are
correct
that
there
will
be
situations
where
individuals
will
be
exposed
to
chlorine.
Therefore,
in
addition
to
the
assessment
where
we
considered
only
acute
exposure
to
chlorine,
we
concluded
that
it
was
appropriate
to
consider
the
effects
of
chronic
exposure
to
chlorine
emissions
from
chlor­
alkali
plants.
In
order
to
provide
an
upper
bound
estimate
of
the
chronic
risks
to
compare
with
the
lower
bound
estimates
assuming
that
all
chlorine
was
converted
to
HCl,
we
conducted
modeling
assuming
that
no
chlorine
is
photolyzed.

In
general,
we
consider
an
exposure
concentration
which
is
below
the
RfC
concentration
(
what
we
call
a
hazard
quotient
of
less
than
1)
to
be
"
safe."
This
is
based
on
the
definition
of
RfC.
The
RfC
is
a
peer
reviewed
value
defined
as
an
estimate
(
with
uncertainty
spanning
perhaps
an
order
of
magnitude)
of
a
daily
inhalation
exposure
to
the
human
population
(
including
sensitive
subgroups)
that
is
likely
to
be
without
appreciable
risk
of
deleterious
noncancer
effects
during
a
life
time
(
i.
e.,
70
years).

As
discussed
above,
we
conducted
additional
modeling
for
major
source
facilities
within
the
subcategory
using
the
same
model
used
for
the
proposed
action
(
ISCST3)
to
estimate
chronic
chlorine
exposure
using
the
assumption
that
no
chlorine
is
photolyzed
to
HCl.
The
hazard
quotients
resulting
from
this
additional
modeling
defined
the
upper
bound
of
our
risk
assessment.

The
highest
upper­
bound
hazard
quotient
estimated
by
the
model
is
just
over
0.3.
(
For
more
details
regarding
this
revised
risk
assessment,
refer
to
table
2
of
the
responses
to
comment
document,
available
in
the
docket.)
Given
the
health
protective
assumptions
used
in
this
analysis,

the
value
of
0.3
represents
a
hypothetical
exposure
that
is
well
above
what
we
would
expect
actual
exposures
to
be.
This
is
because
chlorine
is
converted
to
HCl
in
the
presence
of
sunlight
within
a
few
minutes.
In
addition,
the
hazard
quotient
of
0.3,
which
results
from
this
exposure
scenario
is
well
below
the
safe
value
of
1.
Thus,
we
have
concluded
that,
even
assuming
that
some
chronic
exposure
to
chlorine
may
occur,
that
none
of
the
major
sources
included
in
this
21
subcategory
will
have
emissions
of
chlorine
or
HCl
that
exceed
a
level
of
exposure
which
is
adequate
to
protect
public
health
and
the
environment
with
an
ample
margin
of
safety.

Comment:
Two
commenters
(
IV­
D­
06,
IV­
D­
07)
did
not
support
EPA's
use
of
the
AEGL2
for
use
as
a
short­
term
exposure
limit
for
chlorine
and
HCl.
One
commenter
(
IV­
D­
07)

stated
that
the
AEGL2
values
would
not
sufficiently
protect
public
health
because
they
would
allow
emissions
at
levels
that
cause
"
discomfort,"
and
according
to
the
commenter,
discomfort
is
an
adverse
health
effect.
The
commenter
also
complained
that
EPA
did
not
explain
why
it
chose
to
use
AEGL2
rather
than
AEGL1
or
AEGL3.
The
commenter
explained
that
although
emissions
from
chlorine
plants
did
not
exceed
AEGL2
values,
the
emissions
may
exceed
AEGL1
values,
and
if
they
did,
the
proposed
action
would
not
meet
the
statutory
requirements.
Another
commenter
(
IV­
D­
06)
stated
that
AEGL
limits
are
not
appropriate
for
assessing
daily
human
exposure
scenarios
because
they
were
developed
for
emergency
planning.
The
commenter
recommended
that
EPA
use
the
American
Conference
of
Governmental
Industrial
Hygienists
(
ACGIH),
which
has
a
1­
hour
Short
Term
Exposure
Limit
(
STEL)
similar
to
the
AEGL1
value
of
1
part
per
million
(
ppm),
for
chlorine,
and
is
used
to
protect
against
eye
and
mucous
membrane
irritation.
The
commenter
stressed
that
EPA
must
use
conservative
benchmarks
before
concluding
that
an
ample
margin
of
safety
exists.

Response:
The
AEGL
values
represent
short­
term
threshold
or
ceiling
exposure
values
intended
for
the
protection
of
the
general
public,
including
susceptible
or
sensitive
individuals,
but
not
hypersusceptible
or
hypersensitive
individuals.
The
AEGL
values
represent
biological
reference
values
for
this
defined
human
population
and
consist
of
three
biological
endpoints
for
each
of
four
different
exposure
periods
of
30
minutes,
l
hour,
4
hours,
and
8
hrs.

As
utilized
in
the
proposed
action,
the
AEGL2
1­
hour
concentrations
for
chlorine
and
HCl
are
5,800

g/
m3
and
33,000

g/
m3,
respectively.

The
1­
hour
AEGL1
concentration
for
chlorine
is
2,900

g/
m3
and
the
corresponding
value
for
HCl
is
2,700

g/
m3.
The
ACGIH
short
term
exposure
limit
(
STEL)
for
chlorine,
which
is
1
ppm
is
approximately
equal
to
the
AEGL1
value
of
2,900

g/
m3.

Although
we
stand
by
our
original
analysis,
which
used
the
AEGL2
level,
we
have
incorporated
the
commenter's
suggested
use
of
the
AEGL1
values
(
possibly
with
a
safety
factor)

for
determining
whether
an
ample
margin
of
safety
has
been
obtained.
Therefore,
we
simply
22
compared
the
short
term
(
1­
hour
average)
modeling
results
from
the
original
acute
risk
assessment
to
the
AEGL1
values.
These
results
were
obtained
by
modeling
the
maximum
allowable
hourly
emissions
reported
in
the
section
114
responses
for
each
of
the
sources.
For
plants
that
did
not
report
fugitive
emissions,
fugitive
emissions
were
estimated
using
worst­
case
emission
factors.

The
maximum
modeled
1­
hour
chlorine
concentration
for
two
of
the
three
plants
with
the
mercury
cell
chlor­
alkali
process
is
less
than
5
percent
of
the
AEGL­
1
(
and
ACGIH)
value
for
chlorine.
Further,
the
highest
modeled
concentration
for
any
plant,
155

g/
m3,
is
less
than
6
percent
of
the
AEGL1
values.
The
highest
modeled
1­
hour
HCl
concentration
for
any
plant,

32

g/
m3,
is
less
than
2
percent
of
the
AEGL1
value
for
HCl.
Furthermore,
all
of
the
mercury
cell
chlor­
alkali
facilities
also
produce
chlorine
using
a
non­
mercury
chlorine
production
process
(
i.
e.,

diaphragm
cells).
The
modeled
emissions
represent
chlorine
and
HCl
emissions
from
both
processes.
Therefore,
the
chlorine
and
HCl
emissions
from
the
mercury
cell
chlor­
alkali
process
would
be
even
lower.

Based
on
this
comparison,
we
conclude
that
the
chlorine
and
HCl
emissions
from
mercury
cell
chlor­
alkali
production
plants
do
not
represent
an
unsafe
level
of
acute
exposure.
We
further
maintain
that,
along
with
the
chlorine
exposure
assessment,
this
proves
that
an
ample
margin
of
safety
is
provided
with
no
additional
control.

Comment:
Two
commenters
(
IV­
D­
03,
IV­
D­
05)
supported
EPA's
method
of
selecting
a
risk
assessment
approach
to
meet
the
unique
needs
of
the
chlorine
production
industry.
The
commenters
agreed
that
the
risk
assessment
methodology
should
not
be
interpreted
as
a
standardized
approach
that
would
set
a
precedent
for
how
EPA
will
apply
CAA
section
112(
d)(
4)

in
future
cases.
Furthermore,
the
commenters
(
IV­
D­
03,
IV­
D­
05)
stated
that
the
degree
of
conservatism
built
into
all
aspects
of
the
risk
assessment
conducted
for
the
chlorine
production
source
category
could
vary
greatly
in
future
risk
assessments
for
other
source
categories.
The
commenters
(
IV­
D­
03,
IV­
D­
05)
stressed
that
the
conservative
assumptions
made
in
the
health
effects
assessment,
emissions
estimates,
and
exposure
assessment
were
appropriate
for
the
proposed
action.

In
contrast,
one
commenter
(
IV­
D­
07)
stated
that
the
risk
assessment
fell
short
of
the
Agency's
prior
practice.
According
to
the
commenter,
whenever
EPA
has
made
determinations
23
to
regulate
a
specific
pollutant
based
on
health
considerations
(
e.
g.,
national
ambient
air
quality
standards
(
NAAQS)
for
ozone
and
PM),
the
Agency
evaluated
health
effects
and
exposure
in
great
detail.
The
commenter
contended
that
in
this
case,
EPA
appears
to
be
content
with
"
the
bare
and
unsupported
assumptions
about
what
health
levels
are
safe."
The
commenter
argued
that
it
was
not
appropriate
for
EPA
to
use
a
rigorous
approach
when
setting
standards
and
a
more
cursory
approach
when
making
a
decision
not
to
regulate.

Response:
We
disagree
with
the
commenter
IV­
D­
07'
s
characterization
of
the
assessment
that
forms
the
basis
for
this
decision,
and
we
strongly
dispute
the
characterization
of
the
assessment
as
"
bare
and
unsupported."
As
discussed
elsewhere
in
this
preamble,
we
maintain
that
the
RfC
and
AEGL
values
used
as
benchmarks
for
this
assessment
are
scientifically
sound
and
appropriate.
The
emissions
data
and
other
inputs
used
for
this
analysis,
which
were
provided
by
the
industry
and
checked
by
our
staff,
are
representative
of
the
industry.

In
this
assessment,
the
predicted
health
effects
estimated,
using
very
conservative
inputs
and
assumptions,
were
well
below
the
recognized
health
thresholds.
While
our
approach
in
this
particular
action
may
not
be
the
same
as
an
approach
for
a
NAAQS,
we
believe
that
it
has
been
certainly
more
than
"
cursory."
We
have
looked
at
emissions
and
exposure
data
for
each
of
the
major
sources
in
the
subcategory.
We
have
established
hazard
indices
for
chlorine
and
HCl
for
each
major
source
in
the
subcategory.
We
performed
a
qualitative
ecological
assessment.

Moreover,
in
response
to
comment
received,
we
have
revised
our
analyses
and
taken
into
account
comments
that
we
have
received
when
performing
these
reassessments.
We
will
base
each
risk
assessment
for
this
and
future
regulatory
action
on
sound
scientific
principles.

Comment:
In
the
proposed
action,
the
risk
assessment
modeling
was
conducted
by
placing
receptors
at
the
geographic
center
of
census
blocks
within
2
kilometers
of
the
site
and
in
the
population­
weighted
centers
of
census
block
groups
or
census
tracks
out
to
50
kilometers.

Two
commenters
(
IV­
D­
06,
IV­
D­
07)
did
not
agree
with
this
methodology
for
determining
receptor
location
for
threshold
pollutants.
The
commenters
were
concerned
that
people
closer
to
the
facilities
would
be
harmed
by
emissions
from
chlorine
facilities.
One
commenter
(
IV­
D­
07)

did
not
support
EPA's
use
of
receptors
placed
at
the
center
of
census
blocks
within
2
kilometers
of
the
site
and
in
the
population­
weighted
centers
of
census
block
groups
or
census
tracks
out
to
50
kilometers.
The
commenter
felt
that
it
was
more
appropriate
to
measure
the
exposure
of
the
24
most
exposed
individual
(
e.
g.,
someone
living
at
the
fence
line
of
a
facility
or
directly
downwind).

The
commenter
maintained
that
EPA
must
set
section
112(
d)(
4)
standards
at
levels
that
allow
no
risk
or
adverse
health
effects.
According
to
the
commenter,
EPA's
conclusion
that
most
people
would
not
be
harmed
by
emissions
from
chlorine
facilities
does
not
satisfy
the
requirements
of
section
112(
d)(
4).

One
commenter
(
IV­
D­
06)
stated
that
EPA's
methodology
would
be
more
appropriate
for
cancer
causing
agent,
where
the
risk
is
based
on
probabilities
of
health
effects.
The
commenter
argued
that
for
noncancer
(
i.
e.,
threshold
pollutants)
compounds,
placing
the
receptors
at
the
center
of
census
tracks
would
not
properly
identify
the
highest
impacts
close
to
the
facility.
They
felt
that
it
was
more
appropriate
to
measure
the
exposure
of
the
most
exposed
individual
(
e.
g.,

someone
living
at
the
fence
line
of
a
facility
or
directly
downwind).

Response:
We
certainly
agree
with
the
commenters
that
the
greatest
impacts
will
likely
occur
near
the
facility
for
this
source
subcategory.
However,
we
do
not
agree
with
the
commenters
that
our
approach
fails
to
meet
statutory
requirements.
We
do
not
feel
that
considering
an
"
ample
margin
of
safety"
means
that
we
must
demonstrate
no
risk
or
adverse
health
effects
for
a
theoretical
person
living
at
the
fence
line.
Rather,
it
is
appropriate
to
assess
the
risks
at
locations
where
people
most
likely
reside.
A
census
block
is
the
smallest
geographic
unit
for
which
the
Census
Bureau
tabulates
100
percent
data.
While
census
blocks
in
rural
areas
may
be
larger,
many
blocks
correspond
to
individual
city
blocks
in
more
populated
areas.
The
commenter
is
correct
in
that
an
individual
could
live
closer
to
the
plant
than
the
center
of
the
census
block
and
our
approach
would
have
slightly
underestimated
risk.
It
is
just
as
likely,

however,
that
the
closest
individual
could
live
farther
from
the
plant
than
the
center
of
the
census
block
causing
our
risk
estimates
to
be
slightly
overestimated.
By
placing
receptors
at
the
center
of
populated
census
blocks
on
all
sides
of
a
facility,
we
have
evaluated
people
living
"
downwind."

In
conclusion,
we
continue
to
feel
that
placing
a
receptor
in
the
geographic
center
of
populated
census
blocks
near
a
facility
is
a
well
established
approach
to
exposure
modeling
which
results
in
a
reasonable
approximation
of
estimating
the
risks
where
people
actually
live,
and
we
maintain
that
this
methodology
is
appropriate
for
actions
taken
under
the
authority
of
section
112(
d)(
4).

Comment:
One
commenter
(
IV­
D­
06)
stated
that
all
chlorine
emissions
from
chlorine
production
facilities
that
are
collocated
with
other
source
categories
need
to
be
reviewed
as
a
25
whole
when
evaluating
public
health
risk,
adverse
environmental
effects,
and
possible
control
strategies.
The
commenter
stressed
that
other
sources
of
chlorine
and
HCl
should
be
included
in
the
risk
assessment
under
section
112(
d)(
4).
The
commenter
was
concerned
that
not
accounting
for
all
chlorine
and
HCl
emissions
from
a
facility
would
provide
the
community
with
a
false
sense
of
assurance
of
protection
and
is
not
consistent
with
the
legislative
intent
of
the
CAA
to
consider
cumulative
HAP
exposure
issues
through
an
integrated
approach
under
section
112(
d),
112(
f),

and
112(
k).
Therefore,
the
commenter
requested
that
EPA
evaluate
the
potential
for
adverse
health
and
environmental
impacts
using
conservative
risk
assessment
methodology
that
incorporates
all
known
chlorine
and
HCl
emissions
from
a
contiguous
facility.

Response:
Section
112
of
the
CAA
requires
us
to
list
categories
and
subcategories
of
major
sources
and
area
sources
of
HAP
and
to
establish
NESHAP
for
the
listed
source
categories
and
subcategories.
In
directing
us
how
to
establish
MACT
emission
limits,
section
112(
d)(
3)
of
the
CAA
requires
us
to
set
the
emission
limitation
at
a
level
that
assures
that
all
major
sources
achieve
the
level
of
control
at
least
as
stringent
as
that
already
achieved
by
the
better­
controlled
and
lower­
emitting
sources
in
each
source
category
or
subcategory.
Therefore,
the
entire
MACT
program
is
structured
on
a
source
category­
specific
basis.
All
MACT
standards
developed
to
date
have
addressed
emissions
from
specific
source
categories.

There
are
instances
where
mercury
cell
chlor­
alkali
facilities
are
collocated
with
other
source
categories.
However,
based
on
the
risk
assessment
for
chlorine
and
HCl
emissions
from
mercury
cell
chlor­
alkali
plants,
the
predicted
impacts
from
chlorine
and
HCl
at
these
plants
are
extremely
low.
We
believe
that
the
human
health
and
environmental
impacts
from
all
sources
in
the
subcategory
even
when
collocated
with
other
chlorine
and
HCl
emissions
will
still
be
within
an
ample
margin
of
safety
to
protect
the
public
health,
and
will
not
cause
adverse
environmental
effects.
Moreover,
as
indicated
in
the
preamble
to
the
proposed
action,
most
major
processes
at
the
sites
where
mercury
cell
chlor­
alkali
facilities
are
located
are
subject
to,
or
will
be
subject
to,

NESHAP
to
reduce
HAP
emissions
(
67
FR
44714,
July
3,
2002).
Therefore,
it
would
be
inappropriate
to
include
emissions
from
those
sources
in
an
assessment
for
the
mercury
cell
chloralkali
subcategory
conducted
under
the
authority
of
section
112(
d)(
4).

Comment:
Two
commenters
(
IV­
D­
06,
IV­
D­
07)
stated
that
the
environmental
effects
analysis
was
not
adequate.
One
commenter
(
IV­
D­
06)
stated
that
potential
ecological
effects
of
26
HCl
emissions
have
not
been
properly
referenced.
One
commenter
(
IV­
D­
07)
stated
that
EPA's
proposed
action
falls
short
of
its
obligation
to
protect
against
environmental
effects.
According
to
the
commenter,
EPA
has
understated
its
statutory
obligation
in
the
proposed
action.
The
commenter
referred
to
the
legislative
history,
which
indicates
that
CAA
section
112(
d)(
4)
requires
standards
that
"
would
not
result
in
adverse
environmental
effects
which
would
otherwise
be
reduced
or
eliminated."
The
commenter
listed
the
several
shortcomings
in
the
EPA's
environmental
assessment.

The
commenter
concluded
that
although
EPA
acknowledged
that
it
had
an
obligation
to
ensure
that
any
standards
set
under
section
112(
d)(
4)
did
not
have
any
adverse
environmental
effects,
the
Agency
did
not
properly
consider
the
issue.
Therefore,
the
commenter
stated
that
EPA
could
not
promulgate
standards
under
section
112(
d)(
4)
without
contravening
the
CAA.

Response:
While
CAA
section
112(
d)(
4)
makes
no
mention
of
environmental
effects,
we
took
the
potential
of
such
adverse
effects
into
account
when
we
issued
our
proposed
action.
The
level
of
our
analysis
at
proposal
was
adequate
to
satisfy
the
requirements
of
section
112(
d)(
4).

The
commenters
did
not
suggest
that
they
believed
there
was
the
potential
for
adverse
environmental
effects
from
HCl
or
chlorine
emissions
from
mercury
cell
chlor­
alkali
plants.
Were
there
any
evidence
that
such
adverse
effects
were
likely,
or
even
possible,
we
would
have
conducted
a
more
intensive
ecological
risk
assessment.

The
commenters
are
correct,
however,
that
we
did
not
discuss
the
ecological
effects
of
chlorine.
This
was
because,
as
was
stated
in
the
proposal
preamble,
we
did
not
perform
a
separate
evaluation
of
chronic
chlorine
exposure
because
chlorine
is
converted
to
HCl
in
the
atmosphere
so
rapidly.

Atmospheric
exposure
is
the
primary
pathway
for
environmental
effects
from
chlorine
emissions.
However,
since
most
chlorine
is
converted
to
HCl,
studies
have
focused
on
the
effects
of
HCl
on
vegetation.
Although
plant
exposures
to
elevated
levels
of
chlorine
can
cause
plant
injury,
it
tends
to
be
converted
to
other,
less
toxic
forms
rather
rapidly
in
plants
and
may
not
result
in
the
direct
accumulation
of
toxic
pollutant
residuals
important
in
the
food
chain.

Plant
studies
have
found
foliar
damage
due
to
chlorine
emissions,
decreased
levels
of
chlorphyll
a
and
b,
decreased
leaf
areas,
obvious
chlorosis,
and
a
decline
in
fruit
production
due
to
chlorine
emissions.
27
There
is
evidence
of
effects
to
animals
due
to
accidental
and/
or
catastophic
exposures,
but
the
chlorine
concentrations
of
these
exposures
are
unknown.
However,
there
are
no
data
on
exposure
to
historic
or
atmospheric
concentrations.

More
information
is
available
on
the
effects
of
chlorine
from
aquatic
exposures.
However,

there
is
no
evidence
that
suggests
that
emissions
of
chlorine
from
industrial
sources
in
the
air
contribute
significantly
to
aquatic
concentrations
of
chlorine.

One
study
reported
a
significant
decrease
in
phytoplankton
activity
following
exposure
to
0.1
ppm
chlorine
in
cooling
tower
water.
Additional
laboratory
studies
showed
that
continuous
exposure
to
0.002
milligrams
per
liter
(
mg/
L)
total
residual
chlorine
(
TRC)
resulted
in
depressed
algal
biomass
in
naturally­
derived
microcosms.

When
exposed
continuously
for
96
hours
to
0.05
mg/
L
TRC,
the
Eurasian
water
milfoil
showed
a
significant
reduction
in
shoot
and
dry
weights,
shoot
length,
and
chlorophyll
content.

Aquatic
invertebrates
are
very
sensitive
to
chlorine
and
reaction
products
of
chlorine,
with
early
life
stages
showing
the
most
sensitivity.
For
example,
free
chlorine,
monochloramine,
and
dichloroamine
have
been
shown
to
reduce
the
rate
of
oyster
larvae
survival.
Many
studies
have
been
performed,
and
the
results
are
highly
variable
depending
on
the
chlorine
species,
the
lifestage
of
the
invertebrate,
and
other
factors
such
as
salinity.
The
most
sensitive
aquatic
species
appears
to
be
molluscan
larvae,
with
lethal
concentration
50%
(
LC
50)
of
0.005
mg/
L.
Sublethal
effects
have
also
been
studied,
including
reduced
growth,
reduced
motility,
and
reproductive
failure.

The
effects
on
fish
also
vary
depending
on
the
life
stage
and
fish
species
and
environmental
factors,
such
as
the
pH,
temperature,
and
type
of
chlorine
species.
Larval
stages
are
more
susceptible
to
effects,
and
freshwater
species
are
more
sensitive
than
marine
species.
Free
chlorine
is
generally
more
toxic
than
residual
chlorine;
where
the
form
of
chlorine
is
dependent
on
the
pH
of
the
water.
Sublethal
effects
such
as
avoidance,
reduction
of
diversity
in
chlorinated
effluents,
reduction
or
elimination
of
spawning,
abnormal
larvae,
reduced
oxygen
consumption,

and
gill
damage
have
been
noted.
Many
LC
50
values
were
reported,
ranging
from
0.08
mg/
L
after
24
hours
of
exposure
to
TRC
to
2.4
mg/
L
after
0.5
hours
of
exposure
to
TRC.

Acute
and
chronic
exposures
to
predicted
chlorine
and
HCl
concentrations
around
the
sources
are
not
expected
to
result
in
adverse
toxicity
effects.
These
pollutants
are
not
persistent
in
the
environment.
The
chlorine
and
HCl
emitted
should
not
significantly
contribute
to
aquatic
28
chlorine
concentrations
and
are
not
likely
to
accumulate
in
the
soil.
Chlorine
rapidly
converts
to
HCl
in
the
atmosphere,
and
chlorine
and
HCl
are
not
believed
to
result
in
biomagnification
or
bioaccumulation
in
the
environment.
Therefore,
we
do
not
feel
there
will
be
adverse
ecological
effects
due
to
chlorine
and
HCl
emissions
from
mercury
cell
chlor­
alkali
plants.

2.3
COMPLIANCE
DATE
Comment:
Three
commenters
(
IV­
D­
04,
IV­
D­
05,
IV­
D­
07)
requested
an
extension
of
the
compliance
date,
which
EPA
proposed
to
be
2
years
from
the
effective
date
of
the
final
rule.

Commenters
IV­
D­
04
and
IV­
D­
07
recommended
that
the
compliance
date
should
be
changed
to
3
years
after
promulgation.
The
commenters
stated
that
affected
facilities
are
being
required
to
install
costly,
complex
control
and
monitoring
equipment,
as
well
as
establish
additional
operating
and
maintenance
procedures
at
their
facilities
in
order
to
ensure
compliance
with
the
emission
limitations
and
work
practice
requirements
of
the
proposed
rule.
The
commenters
believed
that
2
years
was
not
a
sufficient
period
of
time
to
complete
such
tasks,
specifically
the
continuous
monitoring
requirements.
The
commenter
further
argued
that
other
MACT
standards,
most
notably
the
Hazardous
Organic
NESHAP
(
HON)
and
the
Hazardous
Waste
Combustor
MACT
standard,
included
a
three
year
compliance
schedule,
and
that
this
time
period
was
more
appropriate
for
the
proposed
standard
as
well.

Commenter
IV­
D­
05
argued
that
EPA
should
extend
the
compliance
date
to
allow
facilities
to
manage
the
high
costs
of
installing
the
control
methods
required
by
the
NESHAP.

Response:
We
agree
that
since
the
existing
sources
are
required
to
install
complex
monitoring
equipment
and
to
establish
additional
operating
and
maintenance
procedures,
it
is
reasonable
to
allow
more
time
than
the
proposed
2­
year
compliance
period.
Section
63.6(
c)(
1)
of
the
NESHAP
General
Provisions
states
that
".
.
.
in
no
case
will
the
compliance
date
.
.
.
exceed
3
years
after
the
effective
date
of
.
.
.."
Therefore,
the
final
rule
specifies
that
the
compliance
date
for
existing
sources
is
3
years
after
the
effective
date
of
the
final
rule.
[
The
compliance
date
for
new
and
reconstructed
sources
is
the
effective
date
of
the
final
rule.
EPA
does
not
expect,

however
that
any
new
mercury
cell
chlorine
production
plants
have
been
or
will
be
constructed
since
the
proposed
rule
was
issued.]

2.4
EMISSION
LIMITATIONS
29
Comment:
Two
commenters
(
IV­
D­
06,
IV­
G­
01)
were
concerned
about
subcategories
that
impacted
the
emission
limitations,
although
these
concerns
were
on
different
levels.

Commenter
IV­
D­
06
commented
on
the
establishment
of
different
emission
limitations
for
similar
emission
point
types,
while
commenter
IV­
G­
01
(
which
submitted
comments
after
the
close
of
the
comment
period)
expressed
concerns
about
the
subcategorization
of
mercury
cell
chlor­
alkali
plants
from
other
types
of
chlor­
alkali
plants.

Commenter
IV­
D­
06
recommended
that
EPA
reconsider
the
subcategories
and
avoid
creating
too
many
small
subcategories.
The
commenter
argued
that
although
the
Act
allows
EPA
to
distinguish
among
classes,
types
and
sizes
of
sources,
the
proposed
rule's
subcategorization
disaggregated
the
chlorine
source
category
too
much.
The
commenter
also
maintained
that
the
proposed
subcategorization
scheme
undermines
an
intent
of
CAA
section
112
of
reducing
HAP
emissions.
The
commenter
was
particularly
concerned
with
the
subcategories
that
contained
less
than
five
sources
(
e.
g.,
plants
without
end­
box
ventilation
systems,
plants
with
oven­
type
thermal
recovery
units,
and
plants
with
non­
oven­
type
thermal
recovery
units).

The
commenter
further
argued
that
for
plants
with
and
without
end­
box
ventilation
systems,
eliminating
end­
box
ventilation
systems
is
"
technically
feasible."
According
to
the
commenter,
some
plants
currently
operate
without
end­
box
ventilation
systems,
and
plants
with
end­
box
ventilation
systems
could
replace
them
with
equipment
that
does
not
require
end­
box
ventilation
systems.
According
to
the
commenter,
EPA's
justification
for
making
the
distinction
between
plants
with
and
without
end­
box
ventilation
systems
appeared
to
be
based
on
the
costs
associated
with
changing
a
plant's
equipment.
The
commenter
maintained
that
the
Act
does
not
authorize
EPA
to
consider
costs
when
developing
subcategories
(
and
may
consider
costs
only
later,
when
deciding
whether
to
establish
standards
beyond
the
MACT
floor).
Therefore,
the
commenter
concluded
that
EPA
had
considered
costs
out
of
order
and
undermined
the
minimum
stringency
requirements
of
the
Act.

Commenter
IV­
G­
01
recommended
that
EPA
redefine
MACT
to
ban
the
use
of
mercury
cell
technology.
The
commenter
explained
that
this
would
be
easily
achievable
because
the
majority
of
the
chlorine
production
industry
already
uses
other,
superior
technologies
such
as
membrane
cells
and
diaphragm
cells.
The
commenter
claimed
that
EPA
abused
its
authority
to
establish
subcategories
of
emission
sources
by
creating
a
subcategory
of
"
mercury
cell
chlor­
alkali
30
plants"
within
the
chlorine
production
source
category
which
limits
the
pool
of
facilities
upon
which
the
MACT
floor
is
based
to
those
who
create
dangerous
pollution,
as
opposed
to
those
industry
leaders
that
use
non­
polluting
and
readily
available
equipment.

The
commenter
further
listed
a
lack
of
confidence
that
the
mercury
cell
process
could
be
adequately
controlled.
The
commenter
explained
that
the
work
practice
requirements
which
are
proposed
to
address
fugitive
emissions,
the
largest
of
emissions
from
this
process
are
too
weak.

Finally,
he
commenter
stated
that
converting
all
mercury
cell
plants
to
membrane
cells
would
still
be
cost­
effective,
and
that
their
estimate
of
the
cost
to
convert
all
mercury
cell
plants
to
other
technologies
($
920
million)
was
justifiable
given
the
significant
threat
to
public
health
and
the
environment
posed
by
mercury.

Response:
Although
there
are
some
facilities
that
operate
sealed
end
boxes
without
endbox
ventilation
systems,
we
do
not
agree
with
the
commenter
that
it
would
be
technically
feasible
for
facilities
that
use
open
end­
boxes
to
convert
to
a
closed
end­
box
system.
According
to
the
industry,
the
two
existing
facilities
that
operate
without
end­
box
ventilation
systems
had
sealed
end­
boxes
incorporated
into
the
original
design
of
the
cell,
which
resulted
in
no
need
for
ventilation
systems.
We
did
not
consider
costs
when
making
this
decision,
but
based
our
decision
on
cell
design
and
emission
profile
(
facilities
that
do
not
have
end­
boxes
have
inherently
lower
emissions
than
those
with
end­
boxes
due
to
the
absence
of
that
emission
point)
when
establishing
MACT
for
mercury
cells.
Therefore,
we
believe
that
it
was
appropriate
to
establish
MACT
for
mercury
cells
with
closed
end­
box
systems
despite
the
fact
that
there
are
only
two
facilities
with
this
type
of
system.

For
facilities
with
mercury
recovery
processes,
we
identified
two
different
technologies
for
mercury
thermal
recovery
units:
oven­
type
and
non­
oven­
type
units.
Oven­
type
units
are
batch
ovens
that
heat
mercury
wastes
to
a
temperature
of
about
1,000oF
for
24
to
48
hours,
depending
on
the
type
of
waste.
Non­
oven­
type
units
are
rotary
kilns
into
which
mercury
wastes
are
fed
at
regular
intervals
(
usually
about
every
5
minutes)
and
fired
at
a
temperatures
of
approximately
1,300oF,
with
a
residence
time
of
about
3
hours.
In
addition
to
differences
related
to
operating
temperature
and
residence
time,
there
are
significant
differences
in
the
volumetric
flowrates
produced
by
the
oven
and
non­
oven
units.
The
volumetric
flowrate
from
an
oven­
type
unit
is
more
than
an
order
of
magnitude
lower
than
that
of
an
non­
oven­
type
unit.
The
differences
31
between
these
two
types
of
units
have
an
impact
on
mercury
concentration
and
mass
flow
rate,
as
well
as
factors
that
affect
mercury
loading
to
the
recovery
system.
Based
on
these
technical
and
operational
differences
between
the
types
of
mercury
thermal
recovery
units,
and
their
potential
effect
on
emissions
characteristics
and
control
device
applicability,
we
believe
that
it
was
appropriate
to
distinguish
between
oven­
type
and
non­
oven­
type
recovery
units
for
the
purpose
of
establishing
MACT
for
mercury
recovery
plants.

We
wish
to
point
out
that
in
all
cases
the
proposed
standards
are
at
beyond­
the­
floor
levels.
We
believe
that
the
commenter's
(
IV­
D­
06)
primary
concern
is
that
source
categories
with
small
numbers
of
sources
leads
to
establishing
standards
that
do
not
achieve
emission
reductions
beyond
the
status
quo.
When
standards
are
set
at
beyond­
the­
floor
levels,
this
concern
is
addressed.

Finally,
we
disagree
with
the
commenter
(
IV­
G­
01)
that
we
abused
our
authority
to
create
subcategories
by
subcategorizing
the
chlorine
production
industry
and
only
including
mercury
cell
plants
in
the
MACT
floor
analysis.
It
is
our
general
policy
to
subcategorize
when
there
are
technical
distinctions
among
classes,
types,
or
sizes
of
sources,
and
manufacturing
processes
of
sources,
that
would
impact
setting
an
appropriate
emission
limit
even
when
creating
the
subcategories
leads
to
some
with
a
small
number
of
sources.
This
policy
is
supported
by
the
broad
discretion
provided
to
the
Agency
to
establish
subcategories
under
CAA
section
112(
c),

the
legislative
history,
and
EPA's
prior
rulemakings.
In
the
House
Debate
on
H.
R.
3030,

Congressman
Bliley
discussed
the
need
to
allow
EPA
to
create
subcategories
of
sources
under
section
112:

Furthermore,
it
is
apparent
that
if
the
title
III
MACT
requirements
are
to
work
sensibly,
it
is
important
that
the
appropriate
control
measure
be
employed
in
light
of
the
nature
of
the
facility
to
be
regulated.
Some
industries
have
processes
that
are
central
to
given
subcategories
of
the
industry.
In
my
view,
the
other
body
employed
the
proper
approach
and
degree
of
flexibility
wherein
it
recognized
.
.
.
that
"
The
Administrator
may
consider
the
type
of
process
employed
in
making
decisions
on
subcategories
and
standards."
Of
course,
there
is
nothing
in
the
language
of
H.
R.
3030
that
would
prevent
such
an
interpretation.
Indeed
such
an
interpretation
and
use
of
subcategorization
is
vital
to
prevent
the
cost­
ineffective
application
of
a
MACT
which
is
inappropriate
to
the
kind
of
process
that
is
integral
to
a
source.

House
Debate
(
May
23,
1990),
reprinted
in
A
Legislative
History
of
the
Clean
Air
Act
Amendments
of
1990,
Comm.
Print
S.
Prt.
103­
38
(
1993)
("
Legis.
Hist.")
at
2725.
The
senate
32
debate
over
the
conference
bill
echoes
this
notion
that
EPA
should
use
subcategorization
to
ensure
that
the
technology­
based
MACT
standards
are
"
appropriate"
for
the
particular
process
or
technology
used
at
a
source.
See
Senate
Debate
(
Oct.
27,
1990),
reprinted
in
Legis.
Hist.
at
1029
(
Sen.
Baucus
explaining,
"[
T]
he
bill
directs
the
EPA
to
list
categories
and
subcategories
for
these
major
sources
so
that
MACT
is
appropriately
applied.").
In
contrast
to
what
commenters
have
asked
for
(
the
closure
of
mercury
cell
chlor
alkali
sources),
Congress
specified
that
"
MACT
is
not
intended
.
.
.
to
drive
sources
to
the
brink
of
shutdown."
2
Legis.
Hist.,
at
3352.

In
general,
EPA
has
previously
taken
the
position
that
subcategorization
is
appropriate
where
types
of
emissions
and/
or
type
of
operation
make
use
of
the
same
air
pollution
control
technology
infeasible.
The
Agency's
rulemakings
reflect
this
general
understanding
and
provide
criteria
for
subcategorization
that
focus
on
the
appropriateness
of
applying
similar
technologybased
requirements
at
different
sources.
The
EPA
has
explained:

In
general,
we
make
the
decision
to
establish
subcategories
within
a
source
category
as
part
of
the
process
of
developing
a
MACT
standard
applicable
to
that
category.
In
establishing
subcategories,
we
typically
consider
factors
such
as
process
operations,
emission
characteristics,
control
device
applicability,
and
opportunities
for
pollution
prevention.

(
64
FR
56493,
56495,
Oct.
20,
1999,
"
Notice
of
Complete
Petition
for
Two
Piece
Can
Subcategory
Delisting.")

The
criteria
EPA
has
described
for
establishing
subcategories
all
relate
to
the
ability
of
different
sources
to
apply
similar
controls.
More
recently,
in
December
2000,
EPA
noted:

In
developing
standards
under
section
112(
d)
to
date,
the
EPA
has
based
subcategorization
on
considerations
such
as:
the
size
of
a
facility;
the
type
of
fuel
used
at
the
facility;
and
the
plant
type.
The
EPA
also
may
consider
other
relevant
factors
such
as
geographic
conditions
in
establishing
subcategories.

(
65
FR
79825,
79830,
Dec.
20,
2000,
"
Regulatory
Finding
on
the
Emissions
of
Hazardous
Air
Pollutants
From
Electric
Utility
Steam
Generating
Units";
see
also
64
FR
56494,
"
In
establishing
subcategories,
EPA
considers
factors
such
as
process
operations
(
type
of
process,
raw
materials,

chemistry/
formulation
data,
associated
equipment,
and
final
products);
emission
characteristics
(
amount
and
type
of
HAP);
control
device
applicability;
and
opportunities
for
pollution
prevention.
The
EPA
may
also
look
at
existing
regulations
or
guidance
from
States
and
other
regulatory
agencies
in
determining
subcategories.")
33
We
feel
that
the
subcategorization
scheme
it
has
used
for
this
category
of
sources
(
as
described
above
and
in
the
proposed
rule)
is
consistent
with
the
statute,
the
legislative
history,
and
EPA's
past
implementation
of
section
112(
c)
and
the
MACT
program.
The
HAP
emitted
by
the
two
subcategories
(
mercury
cell
chlor­
alkali
plants
and
non­
mercury
cell
chlorine
production)

plants
are
different
 
­
while
plants
in
both
categories
emit
chlorine
and
HCl,
only
plants
in
the
mercury
cell
subcategory
emit
mercury.
The
processes
used
to
produce
chlorine
that
the
plants
in
the
two
subcategories
used
are
generally
different
(
because
of
the
use
of
the
mercury
cells).
Thus,

no
change
was
made
in
response
to
this
comment
and
the
final
rule
does
not
ban
mercury
cells
(
except
the
final
rule
does
prohibit
the
emission
of
mercury
from
new
sources).

With
regard
to
the
cost
effectiveness
of
a
ban
of
mercury
cell
chlor­
alkali
facilities,
the
commenter
did
not
provide
any
basis
for
their
estimate
so
we
could
not
verify
these
costs.

Further,
we
do
not
feel
that
"
conversion"
accurately
describes
the
replacement
of
a
mercury
cell
plant
to
another
technology.
There
is
little
salvageable
from
a
mercury
cell
plant
that
can
be
used
in
the
construction
of
a
membrane
cell
plant,
so
the
demolition
of
the
mercury
cell
plant
followed
by
the
construction
of
a
membrane
cell
plant
is
a
more
accurate
characterization.

Therefore,
we
did
not
promulgate
a
final
rule
that
requires
non­
mercury
technology
for
chlorine
production.

Comment:
A
commenter
that
submitted
comments
after
the
close
of
the
comment
period
(
IV­
G­
01)
urged
the
EPA
to
ban
the
use
of
thermal
recovery
units
since
they
emit
mercury
and
there
exist
alternative,
non­
thermal
technologies
for
recovering
mercury
from
wastes
which
have
no
mercury
emissions.

Response:
As
explained
in
the
preamble
for
the
proposed
rule,
(
67
FR
44689),
we
considered
requiring
non­
thermal
technology
for
new
sources.
However,
unlike
thermal
recovery
units
which
are
capable
of
treating
a
variety
of
waste
types,
the
chemical
recovery
and
the
purification
still
processes
have
limited
application.
Both
are
suitable
to
treating
only
certain
waste
types,
K106
wastes
for
the
former
and
end­
box
residues
for
the
latter.
Plants
using
these
nonthermal
recovery
processes
transfer
their
remaining
wastes
off­
site
for
treatment,
which
typically
involves
thermal
recovery.
Given
this
limitation,
we
concluded
that
these
nonthermal
recovery
processes
did
not
qualify
as
a
suitable
basis
for
new
source
MACT.
This
same
rationale
34
explains
why
we
reject
the
commenter's
suggestion
to
require
non­
thermal
technology
for
existing
sources.

Comment:
One
commenter
(
IV­
D­
06)
stated
that
the
proposed
rule
violates
the
CAA
because
the
Agency
did
not
establish
standards
for
some
parts
of
chlor­
alkali
plants
that
emit
mercury.
The
commenter
noted
that
under
the
proposed
rule,
EPA
defined
two
affected
sources:

mercury
cell
chlor­
alkali
production
facilities
and
mercury
recovery
facilities.
The
commenter
did
not
agree
with
EPA's
determination
that
within
mercury
cell
chlor­
alkali
production
facilities,

chlorine
purification,
brine
preparation
and
wastewater
treatment
operations
should
not
be
subject
to
emission
standards
because
they
have
low
mercury
air
emissions.
Similarly,
the
commenter
did
not
agree
with
the
EPA's
decision
not
to
regulate
chemical
mercury
recovery
and
recovery
in
batch
purification
stills
at
mercury
recovery
facilities.
According
to
the
commenter,
the
CAA
does
not
allow
the
Agency
to
exempt
certain
classes,
types
and
sizes
of
sources
from
emission
standards,
unless
EPA
finds
no
potential
for
emissions.
Therefore,
the
commenter
stated
that
EPA
had
a
legal
obligation
to
establish
standards
that
cover
all
mercury­
emitting
parts
of
chloralkali
facilities,
and
the
Agency
must
re­
visit
and
set
emission
standards
for
the
parts
of
the
production
and
recovery
facilities
with
low
mercury
emissions.

Another
commenter
(
IV­
G­
01),
which
submitted
commenters
after
the
close
of
the
comment
period,
urged
EPA
to
set
limits
on
or
eliminate
mercury
contamination
in
caustic
so
that
caustic
purchasers
will
not
be
additional
sources
of
mercury
emissions.

Response:
During
development
of
the
proposed
rule,
we
did
not
receive
any
data
to
indicate
that
mercury
was
emitted
from
chlorine
purification,
brine
preparation,
product
caustic,

or
wastewater
treatment
operations,
and
our
knowledge
of
the
process
indicated
that
any
potential
emissions
would
be
very
limited
(
67
FR
44674).
Furthermore,
we
did
not
receive
any
data
indicating
that
control
measures
designed
to
reduce
HAP
were
in
use
at
existing
facilities
that
had
these
units.
The
same
holds
true
for
chemical
mercury
recovery
and
recovery
in
batch
purification
stills
at
mercury
recovery
facilities.
Therefore,
with
no
reported
emissions
and
process
evidence
that
any
emissions
would
be
very
limited,
we
concluded
that
there
was
no
potential
for
emissions.
Adding
to
this
the
existence
of
a
MACT
floor
of
no
control
(
because
none
are
controlled),
we
did
not
to
regulate
these
processes.
35
The
commenters
did
not
provide
emissions
data
that
would
indicate
that
these
sources
emit
significant
amounts
of
mercury,
or
emit
mercury
at
all.
Therefore,
the
final
rule
does
not
contain
standards
for
mercury
emissions
from
chlorine
purification,
brine
preparation,
wastewater
treatment
operations,
product
caustic,
chemical
mercury
recovery
and
recovery
in
batch
purification
stills.

We
point
out
that
the
final
rule
does
contain
very
stringent
emission
limitations
for
all
point
sources
that
have
been
demonstrated
to
be
sources
of
mercury
emissions.
Further,
the
work
practice
requirements
in
the
final
rule
address
fugitive
mercury
emissions
in
the
chlorine
purification,
brine
preparation,
wastewater
treatment
areas,
as
well
as
areas
where
chemical
mercury
recovery
processes
and
batch
purification
stills
are
located.

Comment:
One
commenter
(
IV­
D­
06)
stated
that
when
establishing
MACT
for
the
proposed
subcategories,
EPA
should
not
rely
on
worst
case
data.
The
commenter
indicated
that
it
was
not
appropriate
for
EPA
to
have
averaged
the
emission
levels
from
all
sources
in
each
source
category.
According
to
the
commenter,
one
court
did
approve
the
practice
of
using
"
worst
case"
data,
but
its
approval
was
in
the
context
of
source
categories
that
had
more
than
30
sources.
Thus,
the
risk
of
"
formalizing
the
status
quo"
was
lower
and
the
technique
was
more
reasonable.

The
commenter
stated
that
given
the
risk
of
formalizing
the
status
quo
emission
levels
when
subcategories
with
very
few
source
occur,
EPA
should
reconsider
alternatives
for
beyond­

thefloor
standards.
The
commenter
stated
that
more
stringent
beyond­
the­
floor
standards
are
more
consistent
with
the
CAA's
purpose
of
reducing
emissions.

Response:
We
are
unclear
what
the
commenter
means
by
relying
on
"
worst
case"
data,
as
the
commenter
did
not
refer
to
a
specific
emission
unit
or
data
set.
In
two
cases
we
did
use
the
highest
values
from
given
data
sets
and
perhaps
this
was
considered
using
worst
case
data
by
the
commenter.
In
setting
an
outlet
concentration
standard
for
mercury
thermal
recovery
units
(
67
FR
44687
and
44688),
we
evaluated
data
sets
and
established
representative
outlet
concentration
values
by
averaging
the
highest
values
from
those
data
sets.
As
stated
in
the
proposal
preamble
(
67
FR
44687,
section
III.
D.
3),
we
evaluated
several
options
for
how
to
use
the
provided
data
to
establish
a
numerical
emission
limit
(
i.
e.,
outlet
concentration).
In
order
to
account
for
variability
in
outlet
mercury
concentrations
due
to
processing
different
wastes,
normal
variation
in
36
recovery/
control
equipment
performance,
and
to
account
for
our
inability
to
correlate
waste
type
processed
to
emissions,
we
chose
to
use
the
highest
values
from
individual
data
sets
to
establish
a
numerical
emission
limit.
We
believe
that
it
was
appropriate
to
utilize
these
values
to
represent
the
level
of
control
achieved
by
the
best
controlled
plant.
Selection
of
a
lower
concentration
would
result
in
this
best­
controlled
plant
being
out
of
compliance
at
times.
For
instance,
if
we
had
selected
the
median
concentration,
the
plant
would
be
out
of
compliance
half
the
time.

The
commenter
did
not
provide
any
specific
and/
or
technical
information
to
lead
us
to
reconsider
our
initial
decisions.
Therefore,
no
change
will
be
made
in
response
to
this
comment.

The
commenter
expressed
concern
that
using
worst
case
data
risks
formalizing
the
status
quo
emission
level.
It
should
be
noted
that
in
both
cases
the
standard
was
set
at
a
beyond­

thefloor
level.
For
oven
type
mercury
thermal
recovery
units,
the
decision
to
set
standards
beyondthe
floor
will
result
in
lower
emission
levels
at
two
out
of
three
plants
using
oven
type
units.
For
non­
oven
type
units,
the
decision
to
set
standards
beyond­
the­
floor
will
result
in
lower
emission
levels
at
two
out
of
three
plants.
Therefore,
we
do
not
believe
the
standards
set
for
mercury
thermal
recovery
units
have
formalized
the
status
quo
emission
level.

Furthermore,
section
112(
d)(
1)
of
the
Act
allows
us
to
distinguish
among
classes,
types,

and
sizes
of
sources
when
establishing
the
standards
for
a
particular
source
category,
without
specifying
a
minimum
number
of
sources
to
be
considered
in
establishing
the
MACT
floor.

Therefore,
we
believe
that
it
was
appropriate
to
establish
MACT
for
the
identified
subcategories
regardless
of
the
number
of
facilities
within
the
subcategory.
No
change
was
made
in
response
to
this
comment.

Comment:
Commenter
IV­
D­
06
stated
that
the
EPA's
exclusion
of
data
from
one
of
the
plants
using
non­
oven­
type
mercury
thermal
recovery
units
was
arbitrary
and
capricious.

According
to
the
commenter,
EPA
excluded
data
from
one
plant
with
a
rotary
kiln
because
the
data
were
unreliable,
because
the
company
took
a
cautious
approach,
and
because
the
data
were
significantly
lower
than
data
submitted
by
other
plants.
The
commenter
maintained
that
EPA
needed
to
offer
better
reasoning
to
support
and
establish
that
the
data
are
unreliable.

Response:
During
the
development
of
the
emissions
limit
for
non­
oven­
type
mercury
thermal
recovery
units,
we
evaluated
the
mercury
recovery/
control
systems
operated
at
three
facilities.
Data
from
one
facility
(
PPG,
Lake
Charles,
LA)
was
based
on
a
company­
developed
1Memorandum,
from
Bhatia,
K.,
EC/
R
Incorporated,
to
Rosario,
I.,
EPA/
OAQPS/
ESD//
MG.
June
27,
2001.
Attachment
B.
Summary
of
Information
on
Mercury
Thermal
Recovery
Unit
at
PPG's
Lake
Charles,
Louisiana
Plant.
EPA
Air
Docket
A­
2000­
02,
Number
II­
B­
17.

37
procedure
derived
from
an
Occupational
Safety
and
Health
Administration
(
OSHA)
method
for
determining
worker
exposure.
The
average
measured
mercury
concentration
for
the
PPG
facility
was
an
order
of
magnitude
lower
than
averages
from
the
other
two
facilities,
and
the
minimum
measured
value
was
two
orders
of
magnitude
lower
than
the
minimum
values
for
the
other
two
facilities.
In
determining
which
data
to
use
to
develop
the
MACT
floor,
we
concluded
that
the
data
from
the
PPG
facility
underestimated
emissions
and
thus
overstated
the
performance
of
the
mercury
recovery/
control
system.
Therefore,
we
rejected
this
data
to
determine
the
MACT
floor.

The
commenter
has
not
provided
technical
meritous
arguments
(
e.
g.,
comments
on
the
OSHA
procedures
or
comments
on
the
relative
magnitude
of
the
rejected
data
compared
to
other
data)
that
would
lead
us
to
reconsider
our
decision
to
not
use
the
data
in
question.
Furthermore,

we
utilized
a
statistical
test
(
i.
e.,
Rosner's
Test)
to
determine
that
the
data
points
were
outliers.

Therefore,
we
are
not
making
any
changes
to
our
original
decision.

However,
we
would
like
to
reiterate
why
we
did
not
use
these
data
because
we
believe
the
commenter
has
slightly
mischaracterized
our
rationale.
Specifically,
the
commenter
stated
that
we
rejected
the
data
because
the
company
used
a
cautious
approach.
We
do
not
want
that
statement
to
be
interpreted
by
the
public
to
mean
that
we
rejected
the
data
because
conservative
procedures
were
used
because
that
is
not
the
case.
The
company
providing
the
data
cautioned
us
that
the
procedures
used
provide
credible
information
on
relative
changes
in
performance,
but
they
do
not
necessarily
produce
accurate
information
on
actual
mercury
releases.
Personnel
from
our
Emission
Measurement
Center
(
EMC)
reviewed
the
method
and
concluded
that
"...
it
should
not
be
considered
to
be
a
quantitative
procedure
that
can
measure
absolute
mercury
emissions
for
inventory
purposes."
1
In
light
of
these
statements
and
our
observations
that
the
data
were
uncharacteristically
low
with
no
apparent
performance
related
reasons
for
the
low
values,
we
decided
to
not
use
the
data.

Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
did
not
agree
with
the
proposed
"
beyond­
the­
floor"
limitations.
They
stated
that
there
is
no
justification
for
EPA
to
set
emission
2
Hazardous
Air
Pollutant
Emissions
from
Mercury
Cell
Chlor­
Alkali
Plants
­
Background
Information
for
Proposed
Standards.
EPA­
453/
R­
02­
007.
U.
S.
Environmental
Protection
Agency,
Office
of
Air
Quality
Planning
and
Standards,
Research
Triangle
Park,
North
Carolina.
February
2002.
Chapter
6.
[
Air
Docket
A­
2000­
32
Item
Number
II­
A­
02]

3
Memorandum.
Bhatia,
K.,
EC/
R
Incorporated,
to
Rosario,
I.,
U.
S.
Environmental
Protection
Agency.
Impacts
Calculations
for
Mercury
Cell
Chlor­
Alkali
Plant
NESHAP
Regulatory
Alternatives.
December
14,
2001.
[
Air
Docket
A­
2000­
32
Item
Number
II­
B­
24]

4U.
S.
Environmental
Protection
Agency,
Office
of
Air
Quality
Planning
and
Standards,
Emissions
Standards
Division.
OAQPS
Control
Cost
Manual,
Fifth
Edition
(
EPA­
453/
B­
96­
001).
Chapter
4.
February
1996.

38
limits
beyond
the
floor,
as
proposed.
The
commenters
stressed
that
EPA
is
required
to
assess
the
cost­
benefit
relationship
when
considering
"
beyond­
the­
MACT­
floor"
limitations.
According
to
the
commenters,
the
Agency
has
not
set
forth
an
accurate
basis
for
costs
associated
with
meeting
the
MACT
floor
or
cost/
benefits
associated
with
meeting
the
"
beyond­
the­
MACT­
floor"
emission
limitations.

Another
commenter
(
IV­
G­
1),
which
submitted
comments
after
the
close
of
the
comment
period,
strongly
endorsed
EPA's
determination
that
beyond­
the­
floor
control
is
merited
for
this
industry
sector.

Response:
We
disagree
with
the
first
two
commenters'
assertions
that
we
did
not
have
a
justification
for
going
beyond
the
floor,
and
that
we
did
not
have
an
accurate
basis
for
costs
associated
with
meeting
the
MACT
floor
or
meeting
beyond­
the­
floor
emission
limitations.
We
conducted
a
very
detailed
plant­
specific
cost
impacts
analysis2,3
based
on
information
and
procedures
contained
in
the
EPA
OAQPS
Control
Cost
Manual4
and
vendor
quotations.
All
of
this
information
was
available
in
the
docket.
However,
the
commenter
did
not
provide
any
specific
comments
on
this
detailed
analysis
or
any
specific
data
or
rationale
to
refute
our
cost
analysis.
Therefore,
we
stand
by
our
original
analysis
and
have
not
made
any
changes
to
the
cost
impacts
approach.
Based
on
our
analysis,
we
concluded
that
the
costs/
benefits
of
going
beyond
the
floor
are
warranted.
Given
the
persistent
nature
of
mercury
in
the
environment
and
its
associated
health
and
welfare
impacts,
we
continue
to
believe
that
the
additional
emission
reductions
that
will
be
achieved
by
the
beyond­
the­
floor
option
are
warranted
considering
the
associated
costs.
39
Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
were
concerned
with
the
proposed
mercury
emission
limitation,
which
has
a
daily
averaging
period.
According
to
the
commenters,

the
Agency
developed
the
proposed
standard
using
annual
average
emissions
and
actual
annual
production
and
then
interpolated
to
a
daily
limit
without
regard
to
statistical
error.

Therefore,
the
commenters
requested
an
annual
average
emission
rate
limit.
The
commenters
proposed
adding
together
the
previous
365
days
emission
totals
and
dividing
by
the
annual
production
capacity.
This
annual
emission
rate
would
then
be
compared
to
the
MACT
limitation.
The
commenters
maintained
that
this
approach
would
be
more
consistent
with
the
data
used
to
develop
the
MACT
standard
and
would
result
in
the
emission
reductions
MACT
is
designed
to
achieve.
The
commenters
stated
that
their
proposed
averaging
period
would
require
facilities
to
react
proactively
to
forestall
statistically
significant
increases
in
emissions,
without
having
to
respond
to
natural
variations
in
data.

As
an
alternative
to
the
annual
averaging
period,
the
commenters
stated
that
if
single
value
daily
limits
are
established,
they
should
be
set
at
not
less
than
two
times
the
annual
limit
divided
by
365
(
days).
To
support
the
use
of
a
variability
factor,
the
commenters
provided
three
arguments.
First,
the
proposed
limits
were
based
on
annual
chlorine
production
capacity.

Second,
the
commenters
were
concerned
about
how
to
address
the
daily
limits
during
days
when
the
plant
is
not
producing
chlorine.
The
commenters
maintained
that
mercury
is
still
emitted
from
facilities
that
are
temporarily
not
producing
chlorine.
Finally,
the
commenters
stated
that
the
limited
data
set
used
to
develop
the
proposed
limit
does
not
reflect
variability
associated
with
dayto
day
operation,
including
variability
in
performance
of
control
devices
and
monitoring
systems.

The
commenters
reasoned
that
for
a
commonly
used
default
coefficient
of
variation
(
CV)
of
0.6,

even
with
ten
representative
samples,
the
multiplier
is
3.0
(
the
commenters
referred
to
the
TSD
for
Water
Quality
Based
Toxics
Control,
EPA/
505/
2­
90­
001).
Therefore,
using
a
multiplier
of
2.0
is
more
than
protective
when
setting
emission
limitations
that
must
be
met
every
day.
The
commenters
recommended
that
EPA
should
subject
this
limited
data
set
to
a
statistical
method
of
characterizing
the
99th
percent
confidence
level
that
the
data
will
fall
below
a
stated
value.

Response:
While
not
stated,
we
assume
that
the
commenters
are
referring
to
the
proposed
by­
product
hydrogen/
end­
box
ventilation
limit.
The
commenters
are
correct
in
that
the
normalized
mercury
emissions
used
to
establish
the
standards
were
based
on
annual
average
40
emissions
and
annual
actual
chlorine
production.
Therefore,
the
commenters'
concerns
about
the
variability
of
the
control
systems
and
the
ability
to
comply
on
a
daily
basis
with
this
limit
have
merit.
We
considered
the
two
options
offered
by
the
commenters
(
365
day
compliance
period
and
adjustments
to
account
for
daily
variations).

We
do
not
believe
that
it
would
be
appropriate
to
apply
a
generic
multiplier
from
other
industries
to
the
limit
for
mercury
cell
chlor­
alkali
plants.
In
addition,
mercury
cell
data
were
not
available
to
assess
the
variability
in
emissions
from
these
emission
points.
Therefore,
we
concluded
that
the
emission
limitation
should
reflect
an
annual
average.
This
would
be
consistent
with
the
data
used
to
create
the
emission
limitation
and
would
allow
for
short­
term
variations
in
operations
and
control
device
performance.

The
final
rule
is
allowing
weekly
monitoring/
testing
as
an
alternative
method
to
determine
continuous
compliance
with
the
emission
limitations.
This
is
discussed
in
more
detail
in
section
2.7
of
this
document.
Therefore,
in
order
to
be
consistent
with
this
continuous
compliance
approach,
we
concluded
that
the
by­
product
hydrogen/
end­
box
ventilation
emission
limitation
final
rule
should
be
annualized
on
a
52­
week
rolling
basis.
Specifically,
the
final
rule
requires
that
mercury
emissions
from
all
by­
product
hydrogen
streams
and
end­
box
ventilation
system
vents
not
exceed
0.076
grams
Hg/
Mg
Cl
2
for
any
consecutive
52­
week
period.

We
do
not
believe
the
concerns
raised
by
commenters
apply
to
the
proposed
emission
limitation
for
mercury
thermal
recovery
unit
vents
which
were
based
on
short­
term
performance
tests
or
periodic
sampling.
Therefore,
no
changes
were
made
to
the
limit
for
mercury
thermal
recovery
unit
vents
in
response
to
this
comment.

Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
were
concerned
that
the
very
low
emission
limits
required
by
EPA's
beyond­
the­
floor
determination
cannot
be
obtained
by
the
industry
as
a
whole.
Specifically,
the
commenters
stated
that
the
Agency
lacks
high
quality
point
source
emission
data
upon
which
to
base
their
"
beyond­
the­
floor"
limits.
According
to
the
commenters,
the
mercury
emission
limitations
for
hydrogen
vent
gas
streams
are
based
on
the
limited
data
provided
by
a
single
facility
in
Maine
that
has
been
closed
for
nearly
2
years.
The
commenters
maintained
that
for
all
of
the
eleven
plants
combined
(
ten
affected
plants
plus
the
closed
Maine
plant),
there
was
very
little
high
quality
point
source
emission
data.
Due
to
the
significant
chance
that
the
data
used
to
develop
the
standard
are
biased
and
quantitatively
non­
41
representative,
the
commenters
stated
that
the
Agency
was
not
justified
in
moving
beyond
the
floor
to
the
most
stringent
value
ever
obtained
by
the
industry.

The
commenters
further
argued
that
EPA's
conclusion
that
the
"
beyond­
the­
floor"
emission
limitations
can
be
met
with
existing,
commercially
available
control
equipment
is
not
supported
and
thereby
seriously
flawed.
The
commenters
pointed
out
that
EPA
presented
no
data
in
the
preamble
or
elsewhere
in
support
of
their
decision
that
the
proposed
standards
could
be
met
with
commercially
available
control
systems.

Response:
First,
we
disagree
with
the
commenters'
assertions
that
we
did
not
have
justification
for
going
beyond
the
floor,
and
that
we
did
not
have
an
accurate
basis
for
costs
associated
with
meeting
the
MACT
floor
or
meeting
beyond­
the­
floor
emission
limitations.
We
conducted
a
very
detailed
plant­
specific
cost
impacts
analysis
which
is
available
in
the
docket.

The
commenters
did
not
provide
any
specific
comments
on
this
detailed
analysis
or
any
specific
data
or
rationale
to
refute
our
cost
analysis.
Therefore,
we
stand
by
our
original
analysis
and
have
not
made
any
changes
to
the
cost
impacts
approach.
Based
on
our
analysis,
we
concluded
that
the
costs/
benefits
of
going
beyond
the
floor
are
warranted.
Given
the
persistent
nature
of
mercury
in
the
environment
and
its
associated
health
and
welfare
impacts,
we
continue
to
feel
that
the
additional
emission
reductions
that
will
be
achieved
by
the
beyond­
the­
floor
option
are
warranted
considering
the
associated
costs.

In
the
proposal
preamble
(
67
FR
44682)
we
acknowledged
that
there
was
uncertainty
associated
with
the
level
of
control
associated
with
the
beyond­
the­
floor
option
proposed
because
the
molecular
sieve
adsorption
control
technology
is
no
longer
commercially
available
and
because
the
plant
representing
this
level
of
control
is
no
longer
operating.
We
did
not
receive
any
comments
indicating
that
the
molecular
sieve
control
technology
is
commercially
available.

Further,
since
the
plant
has
closed
we
were
unable
to
obtain
additional
information
to
further
scrutinize
the
data
to
ensure
that
it
was
not
biased
and
quantitatively
non­
representative.

Therefore,
we
have
concluded
that
we
cannot
fully
demonstrate
that
the
proposed
beyond­

thefloor
standard
is
achievable
using
commercially
available
technology.

However,
in
the
proposal
preamble
(
67
FR
44682),
we
acknowledged
that
there
was
uncertainty
associated
with
the
level
of
control
associated
with
the
level
of
control
associated
with
the
beyond­
the­
floor
option
proposed
because
the
molecular
sieve
adsorption
control
technology
5
Memorandum.
Bhatia,
K.,
EC/
R
Incorporated,
to
Rosario,
I.,
U.
S.
Environmental
Protection
Agency.
Background
on
Vent
Control
System
Enhancements
to
Meet
Regulatory
Alternatives
for
Existing
Mercury
Emission
Sources
at
Mercury
Cell
Chlor­
Alkali
Plants.
September
26,
2001.
[
Air
Docket
A­
2000­
32
Item
Number
II­
B­
22]

42
is
no
longer
commercially
available,
and
because
the
plant
representing
this
level
of
control
is
no
longer
operating.
We
did
not
receive
any
comments
indicating
that
the
molecular
sieve
control
technology
is
commercially
available.
Further,
since
the
plant
has
closed
we
were
unable
to
obtain
additional
information
to
further
scrutinize
the
data
to
ensure
that
they
were
not
biased
and
quantitatively
non­
representative.
Therefore,
we
have
concluded
that
we
cannot
fully
demonstrate
that
the
proposed
beyond­
the­
floor
standard
is
achievable
using
commercially
available
technology.

In
the
proposal
preamble,
we
also
stated
that
we
were
retaining
the
option
of
setting
the
standard
at
the
next
lowest
normalized
emission
value
of
0.076
grams
Hg/
Mg
Cl
2
for
plants
with
end­
box
ventilation
systems.
The
plant
with
this
emissions
level
controls
its
by­
product
hydrogen
system
with
a
series
of
iodine
and
potassium
iodide
impregnated
carbon
adsorbers,
and
their
endbox
ventilation
system
vent
with
a
condenser
and
demister.
These
are
commercially
available
technologies.
Further,
in
the
documentation
for
the
proposed
standard,
we
determined
on
a
plantspecific
basis
which
commercially
available
technologies
could
be
made
to
comply
with
the
proposed
standard.
5
The
commenters
provided
no
comment
on
why
the
application
of
the
very
specific
application
of
these
technologies
could
not
achieve
the
emission
limitations.

The
emissions
estimates
for
the
facility
with
normalized
emissions
of
0.076
grams
Hg/
Mg
Cl
2
are
based
on
weekly
testing
using
methods
that
are
modifications
of
EPA
Methods
101A
and
102.
The
primary
difference
between
the
methods
used
by
the
facility
and
the
EPA
Reference
Methods
is
that
the
sampling
is
not
isokinetic.
We
discussed
our
opinion
that
data
obtained
using
this
type
of
modified
method
were
acceptable
to
use
in
MACT
standards
in
the
proposal
BID
(
page
7­
10).
Therefore,
it
can
be
considered
that
the
emission
estimates
used
to
establish
the
level
of
0.076
g
Hg/
Mg
Cl
2
are
based
on
weekly
performance
tests.
We
hardly
consider
such
data
to
be
of
low
quality.
Therefore
for
the
final
rule,
we
have
selected
the
0.076
g
Hg/
Mg
Cl
2
beyond­
the­
floor
option
as
MACT
for
plants
with
end­
box
ventilation
systems.
43
For
the
by­
product
hydrogen
stream
for
plants
without
end­
box
ventilation
systems
and
mercury
thermal
recovery
unit
vents,
there
were
no
questions
raised
regarding
the
availability
of
the
control
techniques
used
at
the
lowest
emitting
plants
that
formed
the
basis
for
the
proposed
emission
limitations.
Further,
at
proposal,
we
examined
the
data
used
to
establish
the
emission
limitations
and
determined
that
they
were
of
adequate
quality
to
be
used
to
establish
standards.

Therefore,
the
final
rule
retains
the
proposed
emission
limitations
for
these
emission
sources.

2.5
WORK
PRACTICE
STANDARDS
2.5.1
Format
of
Fugitive
Standard
Comment:
One
commenter
(
IV­
D­
06)
recommended
that
EPA
establish
numerical
standards
for
fugitive
emissions.
The
commenter
maintained
that,
absent
published
information
on
good
mass
balance
analyses
performed
at
chlor­
alkali
facilities,
one
can
only
assume
that
significant
mercury
losses
are
occurring
through
fugitive
emissions.
Accordingly,
the
commenter
felt
it
is
crucial
that
the
EPA
step
up
efforts
to
address
all
potential
release
routes
from
such
facilities,
including
fugitive
emissions.

Another
commenter
(
IV­
G­
01),
which
submitted
comments
after
the
close
of
the
comment
period,
expressed
the
view
that
the
mercury
consumed
cannot
be
accounted
for
in
material
balances.
This
commenter
asserted
that
the
proposed
rule
failed
to
address
the
majority
of
the
true
annual
mercury
emissions
from
the
mercury
cell
chlor­
alkali
industry.
The
commenter
explained
that
the
mercury
used
in
this
industry
is
not
incorporated
into
final
products
or
consumed
in
the
process,
so
all
mercury
purchased
is
used
to
replenish
mercury
that
has
been
lost
from
the
manufacturing
process.
The
commenter
compared
the
amount
of
mercury
purchased
by
the
industry
in
1994
(
136
tons)
to
EPA's
estimate
of
annual
emissions
(
22,
200
pounds
or
11.1
tons)
and
concluded
that
the
proposed
rule
fails
to
account
for
nearly
90
percent
of
the
true
mercury
emissions
from
this
industry.
The
commenter
drew
this
conclusion
based
on
the
assumption
that
most
of
the
mercury
would
be
released
to
the
air
rather
than
transferred
off­
site
as
solid
waste
or
accumulated
in
on­
site
tanks
and
ponds.
The
commenter
noted
that
EPA's
estimate
of
annual
emissions
was
based
on
outdated
and
inadequate
estimates
of
fugitive
emissions
which
were
based
on
short­
term
measurements
taken
when
fugitive
emissions
were
non­
representatively
low.
44
Commenter
IV­
D­
06
recommended
that
EPA
require
both
monitoring
of
fugitive
emissions
from
cell
rooms
and
waste
storage
areas
and
establish
a
reduction
goal
for
such
emissions.

According
to
the
commenter,
technologies
are
available
to
quantify
airborne
mercury
concentrations
continuously,
and
in
combination
with
estimates
of
air
flow
rates,
estimates
of
fugitive
loss
rates
under
selected
conditions
could
be
made
and
could
serve
as
the
basis
for
reduction
targets.

Commenter
IV­
G­
01
urged
the
EPA
to
require
each
mercury
cell
chlor­
alkali
facility
to
report
their
annual
consumption
of
mercury
as
an
indicator
of
total
mercury
loss.
The
commenter,
which
did
not
submit
comments
until
after
the
end
of
the
comment
period,

acknowledged
that
the
mercury
could
be
released
into
the
environment
through
other
pathways
(
e.
g.,
solid
waste)
but
stated
that
this
would
provide
an
upper­
bound
estimate
of
annual
mercury
emissions.
The
commenter
argued
that
this
information
would
compensate
for
the
current
lack
of
data
regarding
fugitive
emissions
and
encourage
facilities
to
be
more
aggressive
in
their
leak
inspection
programs
once
they
realize
the
magnitude
of
the
emissions.

Response:
The
commenter
maintains
that
we
should
establish
numerical
standards
for
fugitive
emissions
based
primarily
on
their
assumption
that
significant
emissions
are
occurring
through
fugitive
emissions.
This
conclusion
is
reached
because
of
the
lack
of
good
mass
balance
analyses,
or
as
the
second
commenter
points
out,
the
inability
of
mercury
cell
chlor­
alkali
plants
to
account
for
all
the
mercury
consumed.

The
issue
of
unaccounted
for
mercury
has
been
the
subject
of
intense
scrutiny
from
other
groups
within
EPA
and
the
industry.
As
part
of
the
Great
Lakes
Binational
Toxics
Strategy,

mercury
cell
chlorine
producers
report
annually
the
total
mercury
consumption
for
the
industry.

From
the
baseline
consumption
of
160
tons
per
year
(
tpy)
for
the
years
1990­
1995,
the
industry
reported
an
81
percent
reduction
in
2001
(
30
tpy).
One
of
the
commenters
characterized
the
2001
consumption
as
an
outlier,
but
the
79
tpy
consumed
in
2000
still
represents
a
significant
decrease
from
the
baseline
level.

Even
with
this
decrease
in
consumption,
significant
mercury
remains
unaccounted
for
by
the
industry.
The
mercury
releases
reported
to
the
air,
water,
and
solid
wastes
in
the
2000
Toxics
Release
Inventory
(
TRI)
totaled
around
14
tons.
This
leaves
around
65
tons
of
consumed
mercury
that
is
not
accounted
for
in
the
year
2000.
45
While
it
may
appear
to
the
commenters
that
the
discrepancy
in
the
mercury
material
balance
is
the
result
of
fugitive
emissions,
there
is
little
empirical
evidence
to
support
this
conclusion.
The
commenters
did
not
provide
any
emissions
data
to
support
their
assertion.
Industry
claims
that
mercury
which
condenses
and
accumulates
in
pipes,
tanks,
and
other
plant
equipment
makes
up
a
large
component
of
the
unaccounted
for
mercury.
While
the
commenters
completely
discount
this
claim
by
the
industry,
it
is
relevant
to
consider
the
very
high
density
of
mercury.
For
instance,
the
65
tons
of
unaccounted
for
mercury
in
2000
averages
just
over
7
tons
per
plant.
One
gallon
or
mercury
weighs
around
113
pounds,
meaning
that
around
124
gallons
of
mercury
would
be
unaccounted
for
per
plant.
This
is
a
very
small
percentage
(
less
than
2
percent)
of
the
amount
of
mercury
typically
on
site
at
most
facilities.
However,
the
industry
is
also
unable
to
fully
substantiate
their
theory.
Therefore,
the
fate
of
all
the
mercury
consumed
at
mercury
cell
chloralkali
plants
remains
somewhat
of
an
enigma.

We
agree
that
work
practice
standards
should
only
be
set
when
it
is
not
feasible
to
prescribe
or
enforce
an
emission
standard.
Indeed,
our
reasons
for
establishing
work
practices
instead
of
numerical
limits
are
based
on
factors
associated
with
the
practicality
and
feasibility
of
setting
a
realistic
limit
against
which
compliance
can
be
measured
and
enforced.

First,
data
are
not
available
to
establish
a
numerical
emission
standard
for
fugitive
emissions.
As
stated
in
the
proposal
preamble
(
67
FR
44680),
emissions
data
for
fugitives
from
cell
rooms
and
waste
storage
areas
are
very
limited
to
nonexistent.
Second,
we
do
not
agree
with
the
commenter's
implication
that
available
measurement
technologies
could
support
enforcing
a
numerical
emission
standard
for
the
following
reasons:

°
mercury
emission
monitors
have
not
been
used
to
monitor
fugitive
emissions
at
mercury
chlor­
alkali
facilities
for
compliance
demonstrations;
°
the
variability
in
the
number
of
and
location
of
exhaust
vents
at
each
facility
affects
the
amount
of
air
moved
through
the
cell
rooms
and
thus
affects
the
mass
emission
rate
of
the
fugitives;
and
°
the
variability
of
the
cell
room
roof
configuration
affects
the
feasibility
of
using
the
continuous
emissions
monitors
at
each
facility.

Therefore,
numerical
emission
limitations
for
fugitive
emissions
from
the
cell
room
and
other
areas
is
"
not
feasible,"
as
defined
in
CAA
section
112(
h)(
2)(
B).
Thus,
the
final
rule
retains
the
work
practice
elements
of
the
proposed
rule.
We
have
modified
certain
work
practice
standards,

as
explained
in
another
response.
46
However,
in
response
to
the
concerns
about
unaccounted
for
mercury,
we
added
a
provision
in
the
final
rule
that
requires
each
facility
to
record
and
report
the
mass
of
mercury
added
to
cells
each
year.
In
addition,
we
are
requiring
facilities
to
demonstrate
initial
compliance
with
this
provision
by
providing
their
mass
of
mercury
added
to
cells
for
the
five
years
prior
to
the
compliance
date.
This
will
establish
a
baseline
for
the
mass
of
mercury
being
added
to
cells
for
each
facility.
Since
the
industry
as
a
whole
has
been
providing
this
data
as
a
part
of
the
Great
Lakes
Binational
Toxics
Strategy
since
1996,
we
believe
this
data
is
readily
available.
While
there
are
no
mercury
consumption
reduction
targets
in
the
final
rule,
we
believe
that
reporting
the
mass
of
mercury
added
to
cells
on
a
plant­
specific
basis
will
encourage
additional
action
to
identify
unaccounted
for
mercury
and
reduce
mercury
consumption.

Comment:
A
commenter
that
submitted
comments
well
after
the
close
of
the
comment
period
(
IV­
G­
02)
expressed
the
opinion
that
there
was
a
fundamental
flaw
in
the
proposed
rule
because
the
proposal
will
weaken
existing
sources'
obligations
to
limit
mercury
emissions
from
the
cell
room.
They
cited
42
U.
S.
C.
§
7412(
d)(
7),
which
prohibits
emission
standards
from
weakening
existing
standards.
This
commenter
summarized
the
40
CFR
part
61
mercury
NESHAP,
which
requires
mercury
cell
chlor­
alkali
plants
to
not
emit
more
than
2,300
grams
per
day
(
g/
day)
of
mercury
from
the
entire
facility,
including
the
cell
room,
the
by­
product
hydrogen
streams,
the
end­
box
ventilation
system
vents,
and
other
sources
of
mercury.
The
commenter
stated
that
even
if
emissions
from
all
other
points
were
zero,
emission
from
the
cell
room
cannot
exceed
2,300
g/
day.
The
commenter
acknowledged
that
an
owner
or
operator
may
forego
cell
room
emission
testing
and
assume
that
cell
room
emissions
are
1,300
g/
day,
but
pointed
out
that
complying
with
these
work
practices
does
not
absolve
the
owner
or
operator
of
the
obligation
to
meet
the
applicable
numeric
emission
standard.

The
commenter
contrasted
this
with
the
proposed
rule,
which
established
numerical
emission
standards
for
by­
product
hydrogen
streams,
end­
box
ventilation
systems,
and
mercury
thermal
recovery
unit
vents,
but
not
for
cell
room
fugitive
emissions.
The
commenter
claimed
that
emissions
from
the
cell
room
will
be
able
to
exceed
2,300
g/
day
so
long
as
the
work
practices
are
followed,
when
the
existing
part
61
mercury
NESHAP
prohibits
such
a
result.

The
commenter
concluded
that
it
is
not
sufficient
to
say
that
the
work
practices
that
have
been
proposed
are
more
stringent
than
the
existing
requirements,
because
neither
the
existing
nor
47
proposed
work
practices
by
themselves
require
any
given
numeric
level
to
be
achieved.
They
argued
that
the
existing
numeric
limit
provides
EPA
and
the
public
with
an
enforceable
limit
of
performance
to
which
owners
and
operators
can
be
held.
The
commenter
went
on
to
indicate
that
such
a
numerical
standard
is
particularly
necessary,
as
plants
are
currently
emitting
far
more
than
2,300
g/
day
of
mercury.
To
support
this
assertion,
the
commenter
provided
information
indicating
that
mercury
cell
plants
add
much
more
mercury
to
their
cells
than
2,300
g/
day,
and
they
concluded
that
cell
room
emissions
is
a
very
likely
way
that
mercury
is
lost.
In
conclusion,

the
commenter
stated
that
it
would
be
inappropriate
for
EPA
to
rely
entirely
on
a
work
practice
standard
and
eliminate
stricter
provisions
that
would
enable
the
Agency
to
insist
that
facilities
keep
their
emissions
below
a
set
level.

Response:
The
commenter
summarized
the
40
CFR
part
61
mercury
NESHAP
accurately,

with
one
exception.
Paragraph
§
61.53(
c)(
1),
which
contains
requirements
for
stack
sampling
to
determine
emission
levels
for
cell
room
ventilation
systems
at
mercury
chlor­
alkali
plants,
states:

Stationary
sources
using
mercury
chlor­
alkali
cells
may
test
cell
room
emissions
in
accordance
with
paragraph
(
c)(
2)
of
this
section
or
demonstrate
compliance
with
paragraph
(
c)(
4)
of
this
section
and
assume
ventilation
emissions
of
1,300
grams
per
day
of
mercury.

Further,
§
61.53(
c)(
4)
states:

An
owner
or
operator
may
carry
out
approved
design,
maintenance,
and
housekeeping
practices.
A
list
of
approved
practices
is
provided
in
Appendix
A
of
"
Review
of
National
Emission
Standards
for
Mercury,"
EPA­
450/
3­
84­
014a,
December
1984.
Copies
are
available
from
EPA's
Central
Docket
Section,
Docket
item
number
A­
84­
41,
III­
B­
1.

Therefore,
if
an
owner
or
operator
meets
the
prescribed
work
practice
standards,
they
can
assume
a
mercury
emission
rate
from
the
cell
room
of
1,300
g/
day.

While
the
final
rule
does
not
retain
the
numerical
emission
limitation
from
the
part
61
Mercury
NESHAP,
the
requirements
in
the
final
rule
for
fugitive
mercury
emissions
from
the
cell
room
are
far
more
stringent
than
the
design,
maintenance,
and
housekeeping
practices
allowed
by
the
Mercury
NESHAP
in
lieu
of
meeting
the
numerical
limit.
In
addition,
the
Mercury
NESHAP
contained
only
18
work
practice
requirements
as
compared
to
the
more
than
80
design,
operation,

maintenance,
inspection,
and
required
actions
for
repair
contained
in
tables
1
through
4
to
the
final
rule.
The
work
practice
standards
specify
the
equipment
and
areas
to
be
inspected
along
48
with
the
frequency
of
the
inspections
and
conditions
that
trigger
corrective
action.
Response
time
intervals
for
when
the
corrective
actions
must
occur
are
also
specified.
Furthermore,
some
types
of
inspections
are
required
at
more
frequent
intervals
than
required
by
the
Mercury
NESHAP
(
e.
g.,
inspecting
decomposers
for
hydrogen
leaks
twice
per
day
rather
than
once
each
day).
In
addition,
the
detailed
recordkeeping
procedures
and
reporting
provisions
are
more
fully
developed
than
those
in
the
Mercury
NESHAP,
as
well
as
requirements
for
storage
of
mercury­
containing
wastes.

Finally,
the
work
practice
standards
contain
a
requirement
for
owners
and
operators
to
develop
and
implement
a
plan
for
the
routine
washdown
of
accessible
surfaces
in
the
cell
room
and
other
areas.
The
standards
establish
the
duty
for
owners
or
operators
to
prepare
and
implement
a
written
plan
for
washdowns
and
specify
elements
to
be
addressed
in
the
plan.
A
requirement
for
washdowns
is
an
important
part
of
an
overall
approach
to
reducing
cell
room
fugitive
emissions.

Along
with
a
floor­
level
periodic
mercury
monitoring
program
(
discussed
later),
not
only
will
the
work
practice
standards
in
the
final
rule
result
in
reduced
mercury
fugitive
emissions
(
and,

therefore,
mercury
consumption),
but
provide
much
more
enforceable
provisions
so
that
an
inspector
can
verify
that
they
are
being
met.

In
addition,
we
have
calculated
emission
reductions
for
the
final
rule.
Assuming
that
every
facility
is
complying
with
the
1,000
g/
day
limit
from
point
sources
(
this
value
assumes
that
1,300
g/
day
of
the
2,300
g/
day
facility
limit
are
being
used
for
fugitive
emissions),
we
estimate
that
baseline
emissions
from
all
nine
existing
facilities
(
relative
to
the
Mercury
NESHAP)
are
3,285
kg/
yr.
We
estimate
that
annual
emissions
after
the
application
of
MACT
to
be
217
kg/
yr.

Therefore
the
final
rule
will
result
in
emission
reductions
of
3,068
kg/
yr,
or
approximately
93
percent
from
the
existing
Mercury
NESHAP.
This
supports
our
position
that
we
are
not
setting
a
standard
that
allows
backsliding.
Therefore,
once
the
final
rule
compliance
date
ensues,

sources
subject
to
the
provisions
of
the
final
rule
will
no
longer
be
subject
to
the
Mercury
NESHAP.

Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
05)
generally
supported
the
proposed
increase
in
inspections,
documentation,
and
notifications,
and
the
accelerated
repair
requirements.

However,
one
commenter
(
IV­
D­
05)
recommended
that
EPA
maintain
the
proposed
rule's
49
standards
for
inspections
and
wash­
downs,
but
reduce
the
frequency
and
degree
of
recordkeeping
mandated
to
document
compliance.

Response:
We
thank
the
commenters
for
their
support
of
the
proposed
work
practice
standards.
However,
without
specific
examples
of
requested
changes
or
rationale
for
why
Commenter
IV­
D­
05
finds
the
proposed
recordkeeping
requirements
too
detailed
and
onerous,

we
are
not
led
to
reconsider
the
proposed
requirements
and
no
changes
to
these
provisions
have
been
made.
In
order
to
ensure
that
the
work
practices
achieve
emission
reductions,
we
believe
that
it
the
recordkeeping
provisions
are
appropriate.

2.5.2
Comments
on
Work
Practice
Tables
Comment:
One
commenter
(
IV­
D­
07)
stated
that
EPA
should
clarify
Item
1.
a
of
Table
1
(
Work
Practice
Standards
­
Design,
Operation
and
Maintenance
Requirements)
to
identify
that
it
only
applies
to
new
construction
or
re­
construction
of
existing
operations.
The
commenter
recommended
that
EPA
modify
this
item
as
follows:

"
a.
For
new
or
reconstructed
sources,
Cconstruct
each
cell
room
interior
using
materials
that
are.
.
.
"

Response:
We
agree
with
the
commenter
that
there
the
language
contained
in
Item
1.
a
of
Table
1
(
Work
Practice
Standards
­
Design,
Operation
and
Maintenance
Requirements)
is
confusing.
However,
the
language
suggested
by
the
commenter
implies
that
this
item
applies
to
new
or
reconstructed
affected
sources,
which
are
prohibited
by
the
standard.
Therefore,
in
order
to
address
the
commenter's
concerns
and
to
clarify
Item
1.
a
of
Table
1,
we
have
made
the
following
modification
for
the
final
rule:

a.
For
new
or
modified
cell
rooms,
Cconstruct
each
cell
room
interior
using
materials
that
are...

By
specifying
that
this
item
applies
only
to
new
or
modified
cell
rooms,
we
are
clarifying
that
this
requirement
does
not
apply
to
new
or
reconstructed
affected
sources.

Comment:
One
commenter
(
IV­
D­
07)
stated
that
although
the
primary
purpose
of
cell
rooms
is
to
house
the
mercury
cells,
frequently
cell
room
buildings
contain
cell
maintenance
areas
at
one
end.
Therefore,
the
commenter
was
concerned
that
the
maintenance
part
of
the
building
that
houses
the
cells
would
be
considered
part
of
the
cell
room.
The
commenter
maintained
that
the
wording
of
Item
1.
d
of
Table
1
(
Work
Practice
Standards
­
Design,
Operation
and
Maintenance
Requirements)
could
be
interpreted
by
an
inspector
to
require
all
the
maintenance
50
area
activities
to
be
relocated.
The
commenter
recommended
that
Item
1.
d
be
modified
as
follows:

"
d.
Minimize
the
number
of
items
stored
beneath
the
cells
in
each
cell
room.

Response:
The
purpose
of
this
item
is
to
ensure
that
items
stored
in
cell
rooms
will
not
inhibit
the
cleanup
of
mercury
spills
and
to
prevent
these
items
from
becoming
contaminated
with
mercury
due
to
spills.
We
believe
that
keeping
the
area
around
and
beneath
the
cells
free
of
miscellaneous
items
will
achieve
this
goal.
Therefore,
to
address
the
commenter's
concerns
about
portions
of
the
cell
room
being
used
as
maintenance
areas,
we
have
modified
Item
1.
d
of
Table
1
as
follows:

d.
Minimize
the
number
of
items
stored
around
and
beneath
the
cells
in
each
cell
room.

Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
suggested
that
EPA
modify
Item
2.
b(
1)

in
Table
1
(
Work
Practice
Standards
­
Design,
Operation
and
Maintenance
Requirements)
by
deleting
the
example
("
e.
g.,
removing
bolts
from
a
side
panel...")
because
it
is
not
practicable
to
remove
the
electrolyzer
side
panel
bolts
until
after
the
electrolyzer
has
cooled
and
the
mercury
removed.

Response:
We
have
reassessed
the
practicality
of
removing
the
bolts
from
the
side
panel,

and
we
agree
that
it
is
difficult
to
remove
the
electrolyzer
side
panel
bolts
before
the
electrolyzer
has
cooled
and
the
mercury
is
removed.
Thus,
we
are
deleting
the
example
phrase
from
Item
2.
b.(
1)
in
Table
1.

Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
requested
that
Items
2.
b(
2),
2.
c,
2.
d,
and
2.
e
in
Table
1
(
Work
Practice
Standards
­
Design,
Operation
and
Maintenance
Requirements)
be
modified
by
adding
the
words
"
when
possible"
at
the
end
of
each
requirement.
The
commenters
explained
that
in
some
cases,
these
requirements
cannot
be
implemented.

Response:
The
proposed
standards
in
table
1
(
Items
2.
b(
2),
2.
c,
2.
d,
and
2.
e
would
have
required
facilities
to
perform
several
activities
when
opening
electrolyzers
to
minimize
mercury
emissions,
such
as
keeping
the
bottom
covered
using
an
aqueous
solution.
We
agree
with
the
commenter
that
it
may
not
be
possible
to
take
the
specified
actions
in
all
situations.
For
example,

due
to
the
design
of
different
electrolyzers,
it
may
not
be
possible
to
ensure
that
an
aqueous
liquid
covers
or
flows
over
the
bottom
during
a
side­
panel
change.
Therefore,
we
have
added
the
phrase
"
when
possible"
as
suggested
by
the
commenter.
However,
we
think
that
it
is
important
to
51
document
why
it
is
not
possible,
so
we
have
added
an
item
to
Table
9
of
the
final
rule
(
Table
8
of
the
proposed
rule)
requiring
records
to
document
when
these
actions
are
not
possible.

Comment:
One
commenter
(
IV­
D­
07)
stated
that
EPA
should
combine
Items
4.
a
and
4.
b
in
Table
1
(
Work
Practice
Standards
­
Design,
Operation
and
Maintenance
Requirements)
into
one
Item
(
4.
a)
as
follows:

"
a.
To
prevent
mercury
buildup
after
[
DATE
OF
PUBLICATION
OF
THE
FINAL
RULE
IN
THE
FEDERAL
REGISTER],
equip
each
new
process
line
and
piping
system
with
smooth
interiors
and
adequate
low
point
drains
or
mercury
knock­
out
pots
to
avoid
liquid
mercury
buildups
within
the
pipe
and
to
facilitate
mercury
collection
and
recovery.

Response:
We
agree
with
the
commenter
that
Items
4.
a
and
4.
b
are
redundant
and
have
combined
these
two
items
into
one
item
(
4.
a)
as
suggested
by
the
commenter.

Comment:
One
commenter
(
IV­
D­
07)
stated
that
they
believed
that
EPA
intended
for
Item
5.
a
in
Table
1
(
Work
Practice
Standards
­
Design,
Operation
and
Maintenance
Requirements)
to
apply
to
concrete
floors.
Therefore,
the
commenter
recommended
the
following
modification
to
Item
5.
a:
"
a.
Maintain
a
coating
on
concrete
cell
room
floors..."

Response:
It
was
not
our
intent
to
specify
the
type
of
floor
on
which
coatings
must
be
maintained.
The
intention
of
this
item
was
to
ensure
that
all
cell
room
floors
are
coated
with
a
mercury
resistant
coating
to
facilitate
detection
of
a
liquid
mercury
spill
and
accumulation.

Therefore,
we
have
not
made
any
changes
to
Item
5.
a
of
Table
1.

Comment:
One
commenter
(
IV­
D­
07)
stated
that
Item
5.
c
in
Table
1
(
Work
Practice
Standards
­
Design,
Operation
and
Maintenance
Requirements)
was
not
required
as
long
as
the
requirements
specified
in
Item
5.
d
of
Table
1
are
met
(
i.
e.,
"
maintain
a
layer
of
aqueous
liquid
on
liquid
mercury
in
trenches...").
Therefore
the
commenter
recommended
that
Item
5.
c
be
deleted.

Response:
We
agree
with
the
commenter
that
the
requirements
in
Item
5.
d
of
Table
1
are
sufficient
for
preventing
or
minimizing
mercury
emissions
from
mercury
contained
in
troughs
or
trenches.
However,
in
order
to
prevent
and
minimize
mercury
emissions
from
mercury
spills
on
a
cell
room
floor,
we
believe
it
is
necessary
to
require
that
the
entire
cell
room
floor
must
be
maintained
to
prevent
mercury
accumulation
in
the
corners.
Therefore,
we
have
modified
Item
5.
c
as
follows:

c.
Maintain
the
cell
room
floor
troughs
and
trenches
to
prevent
mercury
accumulation
in
the
corners.
6
A.
Hartman,
EC/
R
to
Docket.
Cleanup
of
Mercury
Spills.
August
12,
1999.
(
EPA
Air
Docket
A­
2000­
32,
Item
II­
B­
8).

52
Comment:
One
commenter
(
IV­
D­
07)
did
not
agree
that
the
work
practice
standards
need
to
specify
that
the
aqueous
layer
be
replenished
at
least
once
per
day
as
specified
in
Item
5.
d
of
Table
1
(
Work
Practice
Standards
­
Design,
Operation
and
Maintenance
Requirements).

According
to
the
commenter,
sufficient
control
of
mercury
vapors
is
achieved
as
long
as
a
facility
is
required
to
maintain
a
layer
of
aqueous
liquid
on
liquid
mercury
contained
in
trenches
or
drains.

Therefore,
the
commenter
requested
that
EPA
delete
the
last
part
of
the
sentence
in
Item
5.
d
of
Table
1
and
modify
the
statement
to
read:
"
Maintain
a
layer
of
aqueous
liquid
on
liquid
mercury
contained
in
trenches
or
drains."

Response:
We
disagree
with
the
commenter
that
simply
maintaining
an
aqueous
liquid
on
liquid
mercury
contained
in
trenches
or
drains
would
sufficiently
control
mercury
vapors
without
being
replenished.
If
the
pool
of
water
covering
the
mercury
is
saturated
with
mercury
vapor
and
the
air
above
it
is
well
below
saturation,
the
mercury
vapor
would
have
a
strong
tendency
to
escape
the
pool.
6
Therefore,
we
have
not
removed
the
requirement
to
replenish
the
aqueous
liquid
on
a
daily
basis.

Comment:
Commenter
IV­
D­
04
suggested
that
the
words
"
leak
tight"
be
deleted
after
the
first
word
in
Item
7.
b
in
Table
1
(
Work
Practice
Standards
­
Design,
Operation
and
Maintenance
Requirements).
In
addition,
the
commenter
requested
that
EPA
add
"
in
good
condition"
after
the
words
"
caustic
system
piping"
and
end
the
sentence
there
(
i.
e.,
delete
phrase
beginning
"
except...").
The
commenter
stated
that
these
changes
maintain
continuity
between
section
7.
b
and
all
other
sections
of
Table
1.
The
commenter
explained
that
other
sections
of
Table
1
list
work
practices
which
limit
leaks
or
emissions
to
the
extent
possible,
and
other
tables
mandate
actions
to
be
taken
in
the
event
of
a
leak.
If
prescribed
actions
are
not
taken
in
a
timely
manner,

then
a
violation
of
a
work
practice
has
occurred.
The
commenter
argued
that
only
Section
7.
b
mandates
that
no
leaks
ever
occur,
and
the
fact
of
a
leak
in
and
of
itself
would
be
considered
a
violation
of
a
work
practice.
Thus,
the
commenter's
suggested
changes
would
make
the
requirements
for
handling
a
leak
in
caustic
system
piping
consistent
with
the
requirements
for
handling
leaks
in
other
piping
systems.
53
Response:
We
agree
with
the
commenter
that
the
proposed
language
could
be
interpreted
to
forbid
any
leaks
and
that
was
not
our
intent.
Thus,
we
are
making
certain
changes
to
this
language.
We
are
deleting
the
phrase
"
leak­
tight"
and
adding
the
phrase
"
in
good
condition"
as
suggested
by
the
commenter.
However,
we
are
not
deleting
the
phrase
beginning
with
"
except,"

instead
we
are
clarifying
it's
intent.

It
was
our
intent
to
require
that
the
connections
between
the
decomposer
and
its
corresponding
cell
components
be
maintained
to
minimize
leaks
to
the
greatest
extent
possible.

Therefore,
in
order
to
ensure
these
conditions
without
completely
forbidding
leaks,
we
believe
it
is
necessary
to
specify
that
these
connections
be
kept
closed
or
tight
unless
maintenance
activities
require
opening
or
loosening
of
these
connections.
The
commenter's
suggestion
to
delete
the
phrase
"
leak­
tight"
and
add
the
phrase
"
in
good
condition"
by
itself
will
not
ensure
these
that
leaks
will
be
minimized
to
the
greatest
extent
possible.
As
such,
we
have
modified
Item
7.
b
of
Table
1
of
the
final
rule
to
read
as
follows:

Maintain
connections
between
the
decomposer
and
the
corresponding
cell
components,
hydrogen
system
piping,
and
caustic
system
piping
in
good
condition
and
keep
the
connections
closed/
tight
except
when
maintenance
activities
require
opening/
loosening
these
connections.

Comment:
One
commenter
(
IV­
D­
07)
stated
that
the
work
practice
requirement
in
Item
7.
d.
1
of
Table
1
(
Work
Practice
Standards
­
Design,
Operation
and
Maintenance
Requirements)
is
confusing.
According
to
the
commenter,
part
of
the
requirement
states
"...
that
meets
the
requirements
listed
below
for
closed
containers..."
but
there
does
not
appear
to
be
any
requirements
for
closed
containers
"
listed
below."
The
commenter
assumed
that
EPA
intended
to
refer
to
the
requirements
defined
in
Items
9
and
10
of
Table
1.
Therefore,
the
commenter
recommended
that
EPA
clarify
the
language
in
Item
7.
d.(
1)
as
follows:

"...
fill
the
decomposer
with
an
aqueous
liquid
or
drain...
into
a
container
that
meets
the
requirements
listed
below
for
closed
containers
in
Table
1,
Items
9
or
10."

Response:
We
agree
with
the
commenter
that
the
statement
"...
a
container
that
meets
the
requirements
listed
below
for
closed
containers..."
in
Item
7.
d(
1)
of
Table
1
is
confusing.

Furthermore,
it
was
not
our
intention
to
specify
that
the
liquid
mercury
in
the
decomposer
should
be
drained
into
a
container
meeting
only
the
closed
container
requirements.
In
fact,
because
of
the
short­
term
need
for
mercury
to
be
removed
from
the
decomposer
for
maintenance,
we
believe
54
that
it
is
appropriate
to
allow
open­
top
containers
meeting
the
requirements
in
Item
9.
Therefore
we
have
modified
Item
7.
d(
1)
to
refer
to
Items
9
(
requirements
for
"
Containers
holding
liquid
mercury")
and
10
of
Table
1
(
requirements
for
"
Containers
used
to
store
liquid
mercury")
as
follows:

"...
fill
the
decomposer
with
an
aqueous
liquid
or
drain...
into
a
container
that
meets
the
requirements
listed
below
for
closed
containers
in
Table
1,
Items
9
or
10."

Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
requested
that
the
words
"...
collect
the
liquid
mercury
from
the
container
in
accordance
with
the
requirements
of
Table
4
in
this
subpart..."
be
deleted
from
Item
9
in
Table
1
(
Work
Practice
Standards
­
Design,
Operation
and
Maintenance
Requirements).
The
commenters
stated
that
there
is
no
good
reason
to
collect
small
amounts
of
mercury
on
a
daily
basis.
The
commenters
maintained
that
such
daily
collections
would
increase
the
handling
of
mercury
and
hence
the
potential
for
emissions.

Response:
We
believe
that
the
commenters
have
misunderstood
the
intent
of
Item
9
in
Table
1.
Item
9
does
not
require
the
daily
collection
of
liquid
mercury.
Instead,
Item
9
requires
that
aqueous
layer
holding
liquids
be
replenished
at
least
once
per
day.
It
was
our
intent
that
the
phrase
"
and
collect
liquid
mercury
from
the
container
in
accordance
with
the
requirements
in
Table
4
to
this
subpart"
would
be
understood
to
mean
that
liquid
mercury
should
be
collected
from
these
containers
as
needed
or
as
required
by
operating
practices.
To
address
the
commenters'
confusion,
we
are
adding
language
to
Item
9
of
Table
1
of
the
final
rule
as
follows
(
see
italics):

Maintain
a
layer
of
aqueous
liquid
over
liquid
mercury
containers
in
each
open­
top
container.
Replenish
the
aqueous
layer
holding
liquid
at
least
once
per
day
and,
when
necessitated
by
operating
procedures
or
observation,
collect
the
liquid
mercury
from
the
container
in
accordance
with
the
requirements
of
Table
4
to
this
subpart.

Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
recommended
that
EPA
delete
Table
4
(
Work
Practice
Standards
­
Requirements
for
Mercury
Liquid
Collection),
because
the
goal
should
be
to
minimize
the
handling
of
mercury.
The
commenters
believe
that
Table
3
(
Work
Practice
Standards
­
Required
Actions
for
Liquid
Mercury
Spills
and
Accumulations
and
Hydrogen
and
Mercury
Vapor
Leaks)
prescribes
the
needed
actions
sufficiently.

Response:
We
disagree
with
the
commenters
that
Table
3
addresses
the
same
situations
as
does
Table
4,
and
we
are
not
deleting
Table
4.
Table
3
addresses
spills
of
liquid
mercury,
55
unplanned/
un­
designed
accumulations
of
liquid
mercury,
hydrogen
vapor
leaks,
and
mercury
vapor
leaks;
all
four
of
these
situations
involve
accidental
and/
or
unintentional
outcomes
of
operations.
Table
4
addresses
the
collection
of
liquid
mercury
from
equipment
designed
to
temporarily
store,
collect,
or
accumulate
liquid
mercury.
Table
3
assumes
that
the
liquid
mercury
is
where
it
should
not
be
(
e.
g.,
on
the
floor),
while
Table
4
describes
the
periodic
collection
of
liquid
mercury
from
equipment
expected
to
have
accumulations
of
liquid
mercury.
Contrary
to
the
commenters'
interpretation,
we
do
not
believe
compliance
with
the
provisions
in
Table
4
result
in
any
unnecessary
handling
of
mercury.
Instead
these
provisions
only
address
how
to
collect
mercury
when
such
expected
accumulations
of
liquid
mercury
inevitably
occur
as
a
result
of
the
manufacturing
process.

Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
suggested
that
EPA
replace
the
word
"
store"
in
Item
11.
c.,
Table
1
(
Work
Practice
Standards
­
Design,
Operation
and
Maintenance
Requirements),
with
"
collect"
and
delete
the
word
"
wastes."
In
addition,
the
commenters
recommended
that
after
the
word
"
containing,"
EPA
should
add
the
phrase
"
materials
in
process
vessels
or...."
The
commenters
reasoned
that
the
materials
are
not
yet
wastes,
and
in
some
cases,

process
vessels
are
used.

Response:
We
agree
that
the
commenters'
suggested
changes
more
clearly
communicate
our
intent
for
caustic
systems.
Furthermore,
since
we
have
deleted
Table
5
of
the
proposed
rule
(
see
later
comment),
we
have
added
a
reference
to
the
applicable
RCRA
requirements
in
Table
1.

Therefore,
Item
11.
c.
of
Table
1
of
the
final
rule
now
reads:

Collect
solids
and
liquids
from
back­
flushing
each
primary
caustic
filter
and
collect
these
mercury­
containing
materials
in
process
vessels
or
in
accordance
with
the
requirements
in
40
CFR
part
265,
subpart
I
and
CC.

Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
suggested
that,
where
applicable,
timing
requirements
for
Table
2
(
Work
Practice
Standards
­
Required
Inspections)
should
be
changed
in
from
"
at
least
once
each
12
hours"
to
"
at
least
twice
daily."
Due
to
operational
issues,
the
commenters
reasoned
that
some
inspections
might
be
delayed
to
be
beyond
12
hours
apart
and
that
such
a
delay
should
not
constitute
a
violation.

Response:
We
agree
with
the
commenters
that
our
intent
would
be
more
clearly
communicated
if
the
reference
to
"
at
least
once
each
12
hours"
was
changed.
Our
intent
was
that
these
inspections
occur
once
each
half­
day
or
twice
daily.
A
similar
confusion
does
not
exist
56
when
the
terms
"
month",
"
3
months",
or
"
6
months"
are
used
because
it
is
commonly
understood
what
starting
point
and
ending
point
are
covered
by
these
terms
(
e.
g.,
the
1st
through
the
31st
or
January
through
June).
Therefore,
we
are
changing
the
language
of
Table
2
to
use
the
terms
"
half­
day"
and
"
day"
to
replace
the
terms
"
12
hours"
and
"
24
hours"
respectively,
relying
on
the
common
understanding
that
day
represents
each
calendar
day
beginning
at
12:
00
a.
m.
and
ending
at
11:
59
p.
m.

Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
suggested
that
Table
5
(
Work
Practice
Standards
­
Requirements
for
Handling
and
Storage
of
Mercury
Containing
Wastes)
duplicates
or
modifies
practices
that
are
required
by
RCRA.
The
commenters
recommended
that
EPA
delete
the
table
because
RCRA
regulations
adequately
address
these
issues.
The
commenters
also
suggested
that
Items
6
and
7
of
Table
8
(
Required
Records
for
Work
Practice
Standards)

duplicate
or
modify
practices
that
are
required
by
RCRA
and
should
be
deleted
as
well
to
avoid
conflicting
regulations.

Response:
Mercury
cell
chlor­
alkali
facilities
are
subject
to
RCRA
requirements
under
40
CFR
parts
268,
subparts
C
and
E;
262,
subpart
C;
265,
subparts
I
and
CC.
Under
CFR
part
265,

subparts
I
and
CC
facilities
are
required
to
store
mercury
wastes
in
containers
that
are
kept
closed
at
all
times
except
when
wastes
are
being
added
or
removed.
We
agree
with
the
commenters
that
the
requirements
contained
in
Table
5
of
the
proposed
rule
duplicate,
and
do
not
add
to,
the
requirements
already
in
effect
for
chlor­
alkali
facilities
under
RCRA.
We
will
remove
Table
5
(
Work
Practice
Standards
 
Requirements
for
Handling
and
Storage
of
Mercury
Containing
Wastes)
and
strike
the
requirements
of
Items
6
and
7
of
Table
9
(
Required
Records
for
Work
Practice
Standards)
of
the
final
rule
(
Table
8
of
the
proposed
rule).

Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
recommended
that
the
term
"
castings"

should
be
deleted
from
Table
6
(
Required
Elements
of
Washdown
Plans)
of
the
proposed
rule,

because
it
is
a
term
that
is
unfamiliar
to
the
industry.
In
addition,
the
commenters
requested
that
a
new
item,
"
Thermal
Treatment
Units,"
be
added
to
the
washdown
plan.

Response:
We
agree
with
the
commenters
and
have
removed
the
term
"
castings"
from
Table
7
of
the
final
rule
(
Table
6
of
the
proposed
rule).
In
addition,
we
have
added
Thermal
Treatment
Units
as
an
item
of
equipment
that
should
be
included
in
Table
7
of
the
final
rule
(
Table
57
6
of
the
proposed
rule),
since
these
areas
are
potential
locations
where
mercury
could
accumulate
on
the
floor.

Comment:
One
commenter
(
IV­
D­
07)
requested
modifications
to
Item
1
of
Table
8
(
Required
Records
for
Work
Practice
Standards)
due
to
the
nature
of
cell
room
operations
and
to
provide
some
flexibility
in
their
compliance
activities.
The
commenter
requested
that
the
language
"
Date
and
time
the
inspection
was
conducted"
be
revised
to
"
Date
and
shift
or
time
the
inspection
was
conducted."
According
to
the
commenter,
inspections
may
occur
during
the
conduct
of
other
activities
and
the
specific
time
the
inspection
occurred
may
not
be
readily
known.

Response:
Some
of
the
inspections
required
under
Table
2
must
occur
twice
daily
(
e.
g.,
end
box
inspections).
Requiring
the
time
of
the
inspection,
rather
than
just
the
shift,
allows
inspectors
to
accurately
determine
whether
the
required
inspections
were
conducted
at
the
appropriate
time.

Inspectors
would
not
be
able
to
determine
whether
two
inspections
were
in
fact
conducted
between
12:
00
a.
m.
and
11:
59
p.
m.
if
only
the
shift
was
recorded.
We
believe
that
it
is
not
overly
burdensome
to
require
the
specific
time
to
be
recorded
when
an
inspection
is
conducted
and
therefore,
we
have
not
made
the
suggested
modifications
to
Item
1
of
Table
9
of
the
final
rule
(
Table
8
of
the
proposed
rule).

Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
recommended
that
EPA
replace
the
word
"
weight"
with
the
word
"
amount"
in
Item
4.
b.
of
Table
8
(
Required
Records
for
Work
Practice
Standards).
The
commenters
explained
that
it
is
not
practicable
to
weigh
very
small
amounts
of
mercury
(
e.
g.,
a
few
drops).

Response:
We
agree
with
the
commenters
that
in
some
instances
weight
of
the
liquid
mercury
will
be
difficult
to
determine.
However,
since
liquid
mercury
has
a
high
density,
the
weight
of
a
few
drops
of
mercury
is
not
insignificant.
We
also
believe
that
it
is
more
clear
to
require
an
estimate
of
weight
rather
than
an
estimate
of
"
amount."

2.5.3
Cell
room
monitoring
Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
disagreed
with
EPA's
proposal
to
institute
a
continuous
mercury
monitoring
program
whereby
owners
and
operators
would
be
required
to
continuously
monitor
mercury
concentration
in
the
upper
portion
of
each
cell
room
and
take
corrective
actions
when
elevated
mercury
vapor
levels
are
detected.
Under
the
proposed
program,
results
would
be
used
to
determine
relative
changes
in
mercury
vapor
levels
rather
than
58
compliance
with
a
cell
room
emission
or
operating
limit.
The
commenters
stated
that
they
believed
that
the
proposed
monitoring
program
was
seriously
flawed
and
should
be
deleted
from
the
final
rule.
The
commenters
noted
that
periodic
monitoring
done
in
various
areas
of
the
cell
room
(
as
currently
practiced
to
ensure
compliance
with
the
Occupational
Safety
&
Health
Administration
(
OSHA)
permissible
exposure
limits)
was
an
appropriate
substitute.
The
commenters
stated
that
cell
room
monitoring
is
redundant
to
the
housekeeping
requirements
and
that
the
work
practices
required
in
Tables
1­
5
allow
for
sufficient
opportunity
to
quickly
detect
abnormal
sources
of
mercury
emissions.

In
contrast,
one
commenter
who
submitted
comments
after
the
close
of
the
comment
period
(
IV­
G­
1)
"
enthusiastically"
supported
the
proposed
cell
room
monitoring
program.
Nonetheless,

the
commenters
felt
that
it
was
unwise
for
the
EPA
to
allow
each
owner/
operator
to
set
his/
her
own
cell
room
action
level.
They
claimed
that
this
strategy
will
allow
more
fugitive
releases
than
necessary
and
was
incompatible
with
the
Clean
Air
Act.

Three
commenters
(
IV­
D­
04,
IV­
D­
05,
IV­
D­
07)
stated
that
they
would
not
be
opposed
to
the
continuous
mercury
monitoring
program
if
the
technology
were
field
demonstrated.
The
commenters
argued
that
the
technology
to
continuously
monitor
for
fugitive
mercury
emissions
is
not
proven,
and
in
fact,
the
commenters
were
aware
of
only
two
attempts
to
continuously
monitor
cell
rooms:
at
a
facility
formerly
operating
in
Maine,
and
a
two­
week
testing
program
performed
at
a
facility
in
Augusta,
Georgia
in
February
2000.
According
to
the
commenters,
the
State
of
Maine
questioned
whether
the
monitoring
program
at
the
Maine
facility
was
representative
of
cell
room
emissions
and
EPA
declined
to
comment
on
the
validity
of
the
program
being
performed
at
the
facility.
With
respect
to
the
testing
program,
the
commenters
stated
that
a
two­
week
testing
program
does
not
show
that
monitoring
on
a
long­
term
basis
is
feasible.
The
commenters
noted
that
the
testing
program
was
performed
by
approximately
30
expert
scientists
highly
knowledgeable
in
performing
such
tests
and
keeping
the
equipment
operational
during
the
test
period.

Two
commenters
(
IV­
D­
04,
IV­
D­
07)
stated
that
they
would
be
willing
to
assist
in
the
development
of
an
appropriate
evaluation
program
for
monitoring
cell
room
mercury
concentration.
Three
commenters
(
IV­
D­
04,
IV­
D­
05,
IV­
D­
07)
recommended
that
the
regulation
should
be
sufficiently
flexible
to
allow
for
a
variety
of
ways
to
implement
the
7J.
S.
Kinsey.
Characterization
of
Mercury
Emissions
at
a
Chlor­
Alkali
Plant,
Volumes
I
and
II.
U.
S.
Environmental
Protection
Agency,
National
Risk
Management
Research
Laboratory.
Research
Triangle
Park,
NC.
Publication
EPA­
600/
R­
02­
007a
and
EPA­
600/
R­
02­
007b.
January
2002..

59
monitoring.
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
suggested
that
such
flexibility
should
allow
for
no,
or
only
partial,
implementation
of
the
continuous
monitoring
program
if
testing
should
prove
to
be
less
than
wholly
successful.
The
commenters
noted
that
if
the
testing
proves
to
be
successful
and
the
monitoring
is
required,
the
regulation
should
allow
for
a
substantial
reduction
in
the
frequency
of
inspections
(
Tables
1­
5)
and
the
complete
elimination
of
some
inspections.

Commenter
IV­
D­
05
stated
that
the
rule
should
either
require
continuous
monitoring
or
detailed
work
practice
standards
but
not
both.
The
commenter
argued
that
cell
room
designs
vary
greatly.
Given
this
variability,
the
commenter
urged
EPA
to
enable
facilities
to
select
the
appropriate
compliance
strategy
for
individual
circumstances.

Response:
The
issues
raised
by
the
commenters
can
be
summarized
in
two
issues.
First,

they
question
the
technical
feasibility
of
the
cell
room
monitoring
program
for
all
facilities.

Second,
they
point
out
that
requiring
compliance
with
both
the
detailed
work
practices
and
the
cell
room
monitoring
program
is
redundant.

With
regard
to
technical
feasibility,
a
cell
room
mercury
monitoring
system
was
tested
in
2000
at
a
mercury
cell
facility
in
August,
Georgia,
7
that
demonstrated
that
the
monitoring
technology
can
be
effectively
installed
and
operated
in
mercury
cell
chlor­
alkali
plant
cell
rooms,

and
this
technology,
along
with
other
measures,
can
be
an
effective
mechanism
to
identify
leaking
equipment
and
other
problems
that
result
in
fugitive
mercury
emissions
from
the
cell
room.

We
acknowledge
that
this
success,
which
occurred
in
a
limited
and
very
controlled
situation
for
a
short
time
period,
does
not
necessarily
prove
that
similar
monitoring
at
every
mercury
cell
room
would
prove
to
be
an
effective
long­
term
method
to
reduce
mercury
fugitive
emissions.
In
fact,
the
design
and
operation
of
the
Augusta
facility
probably
represented
the
optimum
circumstances
for
a
mercury
cell
room
monitoring
program
to
be
successful.
We
are
aware
that
the
cell
room
designs
vary
greatly
and
recognize
that
the
design
affects
the
location
and
number
of
monitors
necessary
to
accurately
monitor
each
individual
cell
room.
In
addition,
depending
on
the
60
design
of
the
roof,
it
may
be
possible
that
installation
of
monitors
that
adequately
monitor
mercury
concentration
would
not
even
be
possible.

Even
with
these
limitations,
a
well
designed
and
implemented
cell
room
monitoring
program
can
effectively
reduce
mercury
fugitive
emissions
on
a
long­
term
basis.
Therefore,
we
included
this
concept
in
the
final
rule.

However,
we
do
agree
with
the
commenters
that
a
comprehensive
continuous
cell
room
monitoring
program
should
be
sufficient
to
reduce
fugitive
mercury
emissions
from
the
cell
room
without
imposing
the
overlapping
requirements
of
the
detailed
work
practices.
Therefore,
we
have
concluded
that
it
is
appropriate
to
allow
facilities
to
implement
the
continuous
cell
room
monitoring
program
as
an
alternative
to,
and
not
in
addition
to,
the
work
practice
requirements.

In
the
final
rule,
facilities
are
given
the
option
to
implement
the
continuous
cell
room
monitoring
program
in
lieu
of
the
work
practice
requirements.
We
do,
however,
feel
there
is
a
need
to
outline
more
specifically
the
elements
that
must
be
included
in
the
cell
room
monitoring
program
to
ensure
that
it
provides
at
least
the
same
level
of
control
as
the
work
practices
and
cell
room
monitoring
program
would
have
provided
together.
Therefore,
there
are
more
prescriptive
requirements
in
the
final
rule
for
the
cell
room
monitoring
plan
option.
The
final
rule
dictates
how
the
action
level
is
to
be
established,
what
measures
must
be
followed
when
the
action
level
is
exceeded,
and
what
records
must
be
kept.

Although
the
continuous
cell
room
monitoring
provisions
are
optional,
some
mercury
monitoring
to
detect
elevated
mercury
levels
in
the
cell
room
is
appropriate.
Therefore,
we
have
included
a
periodic
monitoring
program
to
be
performed
throughout
the
cell
room
as
a
substitute
for
continuous
monitoring.
The
final
rule
contains
a
floor­
level
periodic
monitoring
program
as
part
of
the
work
practice
standards.

2.6
TEST
METHODS,
PROCEDURES,
AND
REQUIREMENTS
Comment:
In
a
previous
comment
(
see
section
2.2
of
this
document),
two
commenters
(

IVD
04,
IV­
D­
07)
requested
that
we
remove
the
title
V
requirements
for
mercury
cell
chlor­
alkali
facilities.
Therefore,
the
commenters
requested
that
§
63.8231
be
revised
to
remove
the
reference
to
the
title
V
permit
such
that
subsequent
performance
testing
be
required
to
be
conducted
no
less
frequently
than
every
two
and
a
half
years.
61
Response:
As
stated
in
our
response
to
the
comment
in
section
2.2
of
this
document,
we
have
retained
the
requirement
to
obtain
a
title
V
permit
in
the
final
rule.
The
final
rule
contains
two
compliance
options.
The
first
option
is
to
operate
mercury
continuous
emission
monitors
that
continuously
measure
mercury
emissions
and
compare
them
to
the
units
of
the
standard.

After
the
initial
performance
test
and
CEM
performance
evaluation,
the
final
rule
does
not
require
owners
and
operators
to
conduct
subsequent
performance
tests
under
this
option.
The
second
option
is
to
conduct
performance
tests
weekly.
Obviously
if
a
plant
is
conducting
performance
tests
weekly
there
is
no
need
for
subsequent
performance
tests.
Therefore,
we
have
deleted
§
63.8231.

Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
were
concerned
that
some
of
the
performance
tests
required
by
EPA
to
demonstrate
initial
compliance
with
emission
limits
do
not
reflect
the
actual
operating
conditions
of
the
units.
For
example,
the
commenters
pointed
to
§
63.8232(
f),
which
requires
operators
of
mercury
thermal
recovery
unit
vents
to
use,
during
test
runs,
only
mercury­
containing
wastes
that
result
in
the
highest
mercury
concentration
in
the
vent.

The
commenters
noted
that
in
actual
practice
there
is
very
little
correlation
between
the
type
of
wastes
processed
and
the
mercury
in
the
vent.
The
commenters
recommended
that
EPA
delete
§
63.8232(
f)
from
the
proposed
rule.
The
commenters
also
mentioned
that
there
were
similar
examples
of
inappropriate
test
method
revisions
in
§
63.8232(
d)
and
(
e)
but
did
not
provide
examples.

Response:
In
the
preamble
to
the
proposed
rule,
we
stated
that
we
were
unable
to
develop
a
correlation
between
the
type
of
wastes
being
processed
and
the
outlet
mercury
concentration
(
see
III.
D.
3,
67
FR
44686).
It
was
our
intent
to
obligate
owners
and
operators
to
process
mercury­
containing
wastes
that
result
in
the
highest
mercury
vent
concentration
during
performance
testing
to
present
the
most
challenging
control
situation
during
the
test.
We
believed
that
requiring
facilities
to
determine
which
mercury
waste
would
provide
the
highest
outlet
mercury
concentration
would
have
achieved
this
goal.
However,
based
on
the
comments
received,
our
evaluation
of
these
comments,
and
given
our
decisions
regarding
continuous
and
periodic
monitoring
(
see
section
2.7
of
this
document),
we
have
concluded
that
it
is
appropriate
for
owners
and
operators
to
operate
their
thermal
recovery
units
in
such
a
way
that
represents
normal
operation.
This
is
consistent
with
§
63.7(
e)
of
the
General
Provisions,
and
as
such,
we
62
believe
that
§
63.8232(
f)
is
unnecessary.
Therefore,
we
have
deleted
§
63.8232(
f)
as
proposed
for
the
final
rule.

Comment:
Three
commenters
(
IV­
D­
04,
IV­
D­
05,
IV­
D­
07)
were
concerned
that
EPA
had
not
subjected
the
test
run
procedures
and
analytical
methods
proposed
in
§
63.8232(
c)

through
(
f)
to
a
separate
notice
and
comment
process
to
assure
their
validity
for
chlor­
alkali
producers.
The
commenters
urged
EPA
to
subject
these
test
methods
to
the
full
notice
and
comment
procedure
that
the
Agency
has
typically
used
to
validate
new
test
methods
and
procedures.
Therefore,
the
commenter
suggested
that
EPA
delete
proposed
§
63.8232(
f)
and
eliminate
or
modify
§
63.8232(
c).
The
commenters
indicated
that
they
were
willing
to
work
with
EPA
to
assess
and
validate
revisions
to
test
procedures
to
incorporate
into
the
proposed
NESHAP.

Response:
The
procedures
required
in
§
63.8232(
c)
through
(
f)
are
not
modifications
to
the
reference
test
methods
in
Appendix
A
of
40
CFR
part
61
and
therefore
are
not
subject
to
the
separate
notice
and
comment
procedure
for
modifications
to
test
methods.
The
proposed
provisions
in
§
63.8232(
c)
through
(
f)
were
requirements
for
how
these
reference
methods
are
to
be
applied
for
this
particular
rule,
and
it
is
entirely
appropriate
and
necessary
for
individual
rules
to
contain
such
provisions.
With
regard
to
notice
and
comment,
the
proposal
provided
the
public
ample
opportunity
to
comment
on
these
requirements
on
how
to
apply
the
reference
test
methods
for
subpart
IIIII.
As
discussed
below,
comments
were
received
on
the
specific
requirements
in
§
63.8232(
c)
through
(
f)
and
we
have
made
changes
in
the
final
rule
in
response
to
these
comments.
The
fact
that
a
number
of
commenters
have
suggested
modifications
and
changes
to
the
proposed
provisions
test
methods
affirms
that
adequate
notice
and
opportunity
to
comment
has
already
been
provided.

Comment:
Commenters
IV­
D­
04,
IV­
D­
05,
and
IV­
D­
07
objected
to
the
proposed
requirements
in
§
63.8232(
c),
which
required
facilities
to
conduct
test
runs
that
(
1)
include
sample
times
which
last
at
least
two
hours
and
(
2)
generate
field
samples
with
mercury
concentrations
at
least
two
times
the
limit
of
detection
for
the
analytical
method.
According
to
the
commenters,
the
currently
approved
test
method
has
no
requirement
to
generate
samples
with
mercury
concentrations
at
least
twice
the
detection
limit.
The
commenters
noted
that
in
practice,
many
operators
may
not
initially
detect
mercury
in
their
test
runs
because
the
stacks
and
vents
typically
63
emit
very
low
amounts
of
mercury.
Therefore,
to
obtain
a
sample
that
contains
an
amount
of
mercury
at
least
double
the
method's
limit
of
detection
could
require
facilities
to
extend
their
sampling
times
by
a
factor
of
three
to
four
times
with
no
guarantee
of
collecting
a
valid
sample
until
after
the
analyses
have
been
performed.
The
commenters
stated
that
there
appears
to
be
no
technical
justification
for
requiring
a
sample
containing
twice
the
detection
limit
for
the
analytical
method.
In
addition,
the
commenters
argued
that
the
cost
of
conducting
such
tests
could
also
be
several
much
higher
than
a
regular
test,
and
may
have
to
be
performed
two
or
more
times
to
obtain
a
valid
test.
The
commenters
noted
that
these
uncertainties
and
costs
underscore
the
fact
that
no
chlor­
alkali
facility
has
used
this
type
of
extended
testing
procedure.
The
commenters
recommended
that
EPA
eliminate
or
modify
Section
63.8232(
c).

Response:
During
the
development
of
the
proposed
rule,
we
collected
numerous
test
reports
from
mercury
cell
chlor­
alkali
plants.
Most
of
these
tests
were
conducted
in
a
manner
that
resulted
in
a
quantifiable
measurement
(
i.
e.,
a
measurement
above
the
detection
limit
of
the
analytical
method),
even
for
those
situations
where
the
mercury
emissions
were
very
low.

However,
there
were
tests,
typically
those
conducted
in
the
late
1980s,
that
reported
mercury
emissions
below
the
detection
limit.
This
alerted
us
to
the
possibility
that
tests
conducted
using
Methods
101,
101A,
and
102
could
result
in
"
non­
detects."

We
believe
that
compliance
should
be
determined
using
actual
measured
values
whenever
feasible
and
reasonable.
This
was
the
basis
for
the
proposed
requirement
to
obtain
a
sample
at
least
twice
the
detection
limit.
However,
the
commenters
raise
valid
points
and
it
is
not
our
desire
to
include
requirements
that
impose
unreasonable
testing
burdens
on
the
industry.
Therefore,
we
provided
an
alternatives
to
the
proposed
requirement
(
at
least
two
hours
and
twice
the
detection
limit)
in
the
final
rule.
Specifically,
this
alternative
is
that
the
sampling
time
and
sampling
volume
for
each
run
must
be
at
least
2
hours
and
1.70
dscm
(
60
dscf),
respectively.
This
volumetric
requirement,
which
was
developed
assuming
the
volumetric
flow
for
a
typical
Method
5
sampling
train,
was
added
to
provide
a
definitive
end­
point
to
the
test
while
still
helping
to
ensure
that
a
measurable
amount
is
collected.
If
these
two
minimum
sampling
requirements
are
met
and
the
results
are
still
below
the
analytical
laboratory's
detection
limit,
the
reported
analytical
detection
limit
can
be
used
to
calculate
the
sample
concentration
value
and,
in
turn,
the
emission
rate
in
the
units
of
the
standard.
64
Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
indicated
that
the
hydrogen
and
end­
box
emission
limitations
should
be
based
on
chlorine
capacity
and
not
actual
production
as
proposed.

The
commenters
also
proposed
that
the
rule
clarify
how
the
annual
chlorine
capacity
is
defined.

This
commenters
suggested
that
annual
chlorine
capacity
(
tons
per
year)
be
defined
as
follows:

AnnualChlorine
Capacity
ton
per
year
DailyChlorineCapacity
of
cell
rated
electricalcurrent
ton
Number
of
cells
days
yr
(
)
@
(
)
*
*
=
maximum
365
According
to
the
commenters,
each
facility
would
provide
EPA
with
documentation
and
updated
information
concerning
its
chlorine
capacity.
The
commenters
recommended
that
§
63.8246(
a)(
2)

be
modified
and
§
63.8246(
a)(
3)
should
be
deleted
to
address
these
comments.

Response:
When
developing
the
form
of
the
standard,
we
determined
that
the
large
variation
within
the
source
category
among
the
plants
in
terms
of
production
and
mercury
emissions
potential,
any
equitable
assessment
of
MACT
should
account
for
this
disparity.
We
selected
chlorine
produced
by
weight
as
the
uniform
parameter
for
our
analysis
for
the
following
reasons:
(
1)
chlorine
is
the
primary
product
generated;
(
2)
chlorine
production
can
be
accurately
determined;
and
(
3)
chlorine
and
hydrogen
are
generated
in
the
same
stoichiometric
quantities
(
i.
e.,
one
molecule
of
hydrogen
is
produced
for
each
molecule
of
chlorine
produced).
The
data
provided
to
us
by
the
industry
and
used
to
determine
the
emission
limitations
for
hydrogen
and
end­
box
were
in
terms
of
actual
annual
production,
not
production
capacity.
Therefore,
using
production
capacity
would
bias
the
emissions
per
mass
of
chlorine
production
low,
thus
not
resulting
an
appropriate
measure
against
the
emission
limitation
as
it
was
developed.

As
discussed
below
in
section
2.7,
the
averaging
period
for
compliance
with
the
emission
limitation
for
by­
product
hydrogen
streams
and
end­
box
ventilation
system
vents
has
been
changed
to
52
weeks.
The
rule
is
not
specific
regarding
the
method
that
must
be
used
to
determine
the
chlorine
production
for
the
52­
week
period.
Rather,
the
rule
requires
that
each
source
develop
a
site­
specific
monitoring
plan
that
includes
a
description
of
how
they
will
measure
or
otherwise
determine
chlorine
production.
This
provision
is
not
meant
to
impose
any
additional
burden
on
affected
sources,
as
we
believe
that
all
plants
accurately
determine
chlorine
production.
This
simply
requires
that
their
methodology
be
submitted
to
the
designated
authority.
65
The
final
rule
does
retain
the
proposed
equation
on
how
to
calculate
short­
term
chlorine
production
for
the
initial
performance
test.
This
calculation
is
based
on
the
average
cell
line
current
load
during
the
test.

2.7
CONTINUOUS
COMPLIANCE
DEMONSTRATION
Comment:
Three
commenters
(
IV­
D­
04,
IV­
D­
05,
IV­
D­
07)
questioned
EPA's
intent
in
establishing
emission
limitations
based
on
the
initial
performance
test.
These
commenters
felt
that
the
proposed
standards
amounted
to
changing
the
emission
limit
based
on
the
emissions
observed
during
the
performance
test
which
amounted
to
ignoring
the
emission
limit
established
through
the
rulemaking
process.
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
stated
that
the
amount
of
mercury
emissions
measured
during
the
initial
compliance
performance
test
should
be
used
only
to
verify
compliance
with
the
MACT
standards,
and
not
to
establish
new
emission
limits.
The
commenters
were
concerned
that
the
emission
limits
would
become
floating
limits
based
on
the
most
recent
performance
test,
as
opposed
to
being
MACT
standards.
The
commenters
stated
that
they
were
not
aware
of
any
other
MACT
standard
that
has
been
written
specifically
in
this
manner,
and
they
seriously
questioned
EPA's
rationale
relating
to
this
portion
of
the
proposal.

The
commenters
indicated
that
variations
around
the
concentrations,
above
and
below,

measured
during
the
performance
test
can
be
expected.
Treatment
systems
employed
to
obtain
compliance
(
e.
g.,
carbon)
would
be
expected
to
show
some
slight
deterioration
after
a
period
of
operation.
Therefore,
a
performance
test
conducted
just
after
a
carbon
change
would
result
in
an
unrealistically
low
operating
limit.
Finally,
the
commenters
were
concerned
that
different
facilities
would
have
different
operating
limits,
depending
on
variables
like
the
type
of
control
equipment
installed,
the
operating
conditions
on
the
day
of
the
emission
test
(
i.
e.,
mercury
volatility
changes
significantly
with
temperature),
and
other
factors.

Commenter
IV­
D­
05
was
concerned
that,
given
the
wide
variability
in
emission
constituents,
operators
would
not
be
able
to
assure
that
their
facilities
will
consistently
emit
within
the
limits
established
during
an
ideally
controlled
initial
performance
test.

Two
commenters
(
IV­
D­
04,
IV­
D­
07)
acknowledged
that
other
MACT
standards
require
the
gathering
of
data
for
surrogate
parameters
(
e.
g.,
scrubber
liquor
pH,
scrubber
liquor
flow)

when
direct
measurement
of
a
control
parameter
is
not
required
or
feasible.
These
surrogate
parameters
are
used
to
establish
performance
requirements
for
the
control
device.
The
66
commenters
argued
that
in
these
cases,
the
direct
measurement
of
a
specific
control
parameter
may
not
have
been
required
(
in
fact,
such
is
the
case
with
the
current
Mercury
NESHAP).
The
commenters
went
on
to
say
that
in
cases
where
performance
requirements
based
on
surrogate
parameters
were
established
during
the
performance
test,
the
emission
limitation
was
not
modified
to
reflect
the
actual
emissions
experience
during
the
test.
However,
the
commenters
stated
that
they
felt
that
this
is
exactly
what
is
required
under
the
proposed
rule.

The
commenters
(
IV­
D­
04,
IV­
D­
05,
IV­
D­
07)
stated
that
they
do
not
believe
that
the
provisions
proposed
under
§
63.8190
are
consistent
with
other
MACT
standards
or
the
CAA
and
requested
that
the
Agency
delete
§
63.8190(
b)(
1)
and
(
2),
as
well
as
all
references
to
this
section
throughout
the
proposed
regulation,
including:
deleting
§
63.8236(
a)(
2)
and
(
b)(
2));
deleting
§
63.8256(
b)(
2);
and
modifying
the
language
in
§
63.8254(
b)(
8)
to
eliminate
the
reference
to
a
sitespecific
monitoring
plan
and
to
refer
to
the
emission
limit.

Commenter
IV­
D­
05
argued
that
EPA's
required
installation
of
instruments
directly
in
the
vent
stream
to
continuously
monitor
actual
concentration
of
mercury
and,
therefore,
actual
mercury
emissions,
means
that
there
is
no
need
to
rely
on
operating
parameters
which
have
been
calculated
for
only
one
set
of
conditions.
The
commenter
acknowledged
that
EPA
may
have
sought
to
instill
flexibility
in
the
proposed
rule,
but
maintained
that
this
concept
of
establishing
mercury
concentration
limits
during
the
performance
test
would
impose
unrealistic
emission
limits
that
would
vary
widely
between
facilities.

One
commenter
(
IV­
D­
07)
recommended
that
EPA
allow
facilities
to
propose,
in
lieu
of
continuos
monitoring,
their
own
periodic
monitoring
program.
The
commenter
stated
that
because
of
the
way
a
nonregenerable
carbon
adsorption
system
works,
continuous
monitoring
is
not
necessary
and
is
impractical.

One
commenter
(
IV­
D­
04)
was
concerned
about
the
cost­
benefits
of
continuous
monitoring
systems
(
CMS)
in
the
by­
product
hydrogen,
end­
box
ventilation
system,
and
mercury
thermal
recovery
unit
vent
streams.
According
to
the
commenter,
the
types
of
control
devices
likely
to
be
used
for
controlling
mercury
emissions
from
these
streams
(
i.
e.,
carbon
or
molecular
sieve
units)

have
very
good
performance
characteristics
and
are
not
likely
to
incur
short­
term
upsets.
The
commenter
noted
that
performance
is
subject
to
normal
variations,
and
the
ability
of
these
systems
to
absorb
mercury
does
degrade
over
time.
The
commenter
stated
that
before
emissions
reach
the
67
permit
limits
due
to
reduced
performance,
the
beds
must
be
replaced.
The
commenter
requested
that
in
lieu
of
CMS,
facilities
should
be
allowed
to
rely
on
the
known
capability
of
the
systems
to
operate
reliably.
The
commenter
stated
that
the
Agency
could
delete
the
requirement
for
CMS
without
any
real
harm
to
the
environment.

Response:
In
general,
we
disagree
with
the
premise
of
the
commenter's
argument.
The
proposed
rule
would
have
required
that
continuous
compliance
for
each
vent
be
determined
by
monitoring
mercury
concentration
as
an
operating
limit.
The
measured
concentrations
would
not
have
been
used
to
compare
directly
with
the
emission
limitations.
Rather,
they
would
have
provided
an
indication
that
the
control
device
was
performing
in
a
manner
consistent
with
the
operation
during
the
initial
performance
test.
Therefore,
the
proposed
requirements
to
establish
operating
limits
would
have
established
emission
limitations,
or
resulted
in
changing
emission
limits,
based
on
the
initial
performance
test.

However,
we
do
acknowledge
that
there
is
a
difference
in
a
mercury
concentration
operating
limit
and
an
operating
limit
based
on
surrogate
parameters
because
the
mercury
concentration
is
obviously
a
direct
measure
of
mercury
emissions.
In
fact,
we
agree
with
the
point
made
by
commenter
IV­
D­
05'
s
that
there
is
no
need
to
rely
on
operating
parameters
when
a
direct
measurement
of
emissions
is
being
required.

As
discussed
at
length
in
the
proposal
preamble
(
67
FR
44690),
we
considered
requiring
mercury
continuous
emission
monitors
(
CEM)
that
would
directly
measure
in
units
of
the
standard.
Although
monitoring
that
directly
measures
compliance
is
preferred,
we
decided
to
propose
mercury
concentration
operating
limits
based
on
the
uncertainties
associated
with
the
cost
and
reliability
of
the
mercury
monitoring
devices.
Commenters
did
not
provide
any
information
to
alleviate
these
concerns.
In
fact,
as
discussed
in
the
subsequent
comment,
they
shared
our
basic
concerns
even
if
the
monitoring
devices
were
only
used
for
operating
limits.

We
weighed
the
comments
related
to
the
mercury
concentration
operating
limits
against
the
concerns
associated
with
using
mercury
concentration
monitors
as
CEM.
Our
preference
continues
to
be
to
require
mercury
CEM.
With
sufficient
evaluation,
analysis,
and
refinement,
the
industry
will
find
these
devices
acceptable.
However,
we
could
not
require
these
devices
in
the
final
rule
without
a
fallback
alternative
if
sources
found
that
these
monitoring
devices
were
not
acceptable
for
use
within
the
industry.
8
Hazardous
Air
Pollutant
Emissions
from
Mercury
Cell
Chlor­
Alkali
Plants.
Background
Information
Document
for
Proposed
Standards.
EPA­
453/
R­
02/
007.
U.
S.
Environmental
Protection
Agency,
Research
Triangle
Park,
North
Carolina.
February
2002.
Page
7­
10.
[
Air
Docket
A­
2000­
32
Item
Number
II­
A­
02]

68
During
the
development
of
the
proposed
standards,
we
learned
that
many
mercury
cell
chlor­
alkali
facilities
conducted
periodic
(
e.
g.,
weekly,
monthly)
tests
to
determine
the
mercury
content
in
vent
streams.
This
is
done
to
assess
control
device
performance
or,
for
the
by­
product
hydrogen
stream,
to
ensure
product
quality.
These
tests
are
not
typically
conducted
using
EPAapproved
test
methods,
but
are
usually
conducted
using
modified
methods.
These
methods
were
discussed
in
the
Background
Information
Document
for
the
proposed
standards.
8
Since
this
periodic
testing
is
already
being
conducted
at
many
mercury
cell
plants,
we
evaluated
whether
a
continuous
compliance
option
could
be
included
in
the
final
rule
based
on
such
periodic
testing.

Since
such
testing
directly
measures
mercury
emissions,
we
concluded
that
it
would
be
an
acceptable
alternative
to
mercury
CEM.
The
only
question
was
how
often
such
testing
would
be
needed
to
ensure
continuous
compliance
with
the
emission
limitations.
Daily
testing
would
certainly
be
adequate,
but
we
were
concerned
about
the
costs
and
burden
associated
with
365
tests
each
year
for
each
process
vent.

The
most
common
final
control
device
is
(
or
will
be)
nonregenerative
carbon
adsorption.

These
fixed
bed
carbon
devices
can
operate
for
long
periods
of
time
before
a
carbon
change
is
needed.
The
carbon
replacement
frequency
is
often
more
than
a
year.
Weekly
testing
would
be
more
than
sufficient
to
represent
the
emissions
for
the
entire
week
and
to
indicate
when
breakthrough
(
i.
e.,
the
point
at
which
the
carbon
has
become
saturated
with
mercury
emissions)
is
approaching.
Because
breakthrough
does
not
occur
instantaneously,
but
is
slowly
approached
over
time,
weekly
testing
is
sufficient
to
detect
the
point
at
which
breakthrough
is
approaching.

However,
there
is
the
possibility
that
non­
carbon
devices
such
as
condensers,
absorbers,
or
regenerative
molecular
sieves
could
be
used
as
the
final
control
device
to
comply
with
the
emission
limits
in
the
final
rule.
Since
improper
operation
of
these
devices
could
result
in
higher
emissions
for
shorter
periods,
we
had
concerns
about
utilizing
weekly
testing
for
these
devices.

However,
we
concluded
that
if
parametric
monitoring
of
surrogate
parameters
(
e.
g.,
condenser
69
temperature)
were
conducted
to
ensure
consistent
and
proper
operation
of
these
devices,
weekly
testing
would
be
acceptable.

Therefore,
the
final
rule
includes
two
options
for
continuous
compliance
for
the
by­
product
hydrogen
stream,
the
end­
box
ventilation
system
vent,
and
the
mercury
thermal
recovery
unit
vent.
The
first
option
is
continuous
emissions
monitoring
using
a
mercury
continuous
emissions
monitoring
system.
The
second
is
periodic
testing
using
Method
101,
101A,
or
102
or
an
approved
alternative
method.
Specifically,
this
second
option
requires
that
at
least
three
acceptable
test
runs
be
conducted
each
week.
As
part
of
the
periodic
testing
option,
if
the
final
control
device
is
not
a
nonregenerative
carbon
adsorber,
surrogate
parameter
monitoring
is
required.

Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
were
concerned
with
EPA's
proposed
requirements
for
the
installation
of
continuous
monitoring
systems
(
CMS)
for
monitoring
mercury
emissions
from
by­
product
hydrogen,
end­
box
ventilation
system,
and
mercury
thermal
recovery
unit
vent
streams.
The
commenters
were
concerned
that
not
only
had
the
technology
not
been
demonstrated,
but
also
that
it
might
not
be
possible
to
develop
such
monitoring
systems
within
the
next
few
years.
Furthermore,
the
commenters
were
seriously
concerned
whether
such
CMS
could
be
installed
and
operated
in
hydrogen
streams
even
if
the
technology
could
be
demonstrated
for
non­
flammable
streams.
The
commenters
explained
that
hydrogen
is
highly
flammable
and
any
CMS
used
in
a
hydrogen
stream
would
need
to
be
designed
to
prevent
explosions.
Therefore,

according
to
the
commenters,
the
regulation
needs
to
be
flexible
enough
to
allow
for
the
possibility
that
CMS
cannot
be
developed
for
some
or
all
of
these
streams.

One
commenter
(
IV­
D­
04),
a
trade
association,
indicated
that
one
of
their
member
companies
is
working
with
EPA
to
determine
whether
a
CMS
can
operate
in
the
by­
product
hydrogen,
end­
box
ventilation
system,
and
mercury
thermal
recovery
unit
vent
streams.
The
commenter
was
concerned
that
the
test
plan
is
insufficient
to
demonstrate
long­
term
plant
reliability.
In
particular,
the
commenter
doubted
that
the
test
program
could
be
implemented
and
assessed
sufficiently
soon
to
allow
for
operation
in
the
two­
year
schedule
required
by
the
proposed
regulation.
The
commenter
also
indicated
that
they
are
prepared
to
participate
in
a
program
to
assess
CMS
instrumentation
as
applied
to
chlor­
alkali
vent
gas
streams.
In
order
to
ensure
that
any
testing
program
is
comprehensive
and
reliable,
the
commenter
stated
that
a
70
minimum
of
three
years
would
be
necessary.
Therefore,
according
to
the
commenter,
the
regulation
needs
to
be
flexible
enough
to
allow
for
the
possibility
that
CMS
cannot
be
developed
for
some
or
all
of
these
streams.

Response:
As
discussed
in
responses
to
the
previous
comment
and
comments
in
section
2.3,

we
believe
that
changes
have
been
made
in
the
final
rule
to
address
these
concerns.
First,
the
compliance
date
has
been
extended
from
two
to
three
years
from
the
promulgation
date,
thus
allowing
more
time
for
evaluation
of
mercury
continuous
emission
montitors.
Second,
an
alternative
continuous
compliance
approach
based
on
periodic
testing
has
been
added
should
an
owner
or
operator
find
that
mercury
continuous
emission
monitors
are
not
feasible
for
their
situation.

Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
stated
that
if
the
CMS
technology
can
be
developed
and
the
Agency
determines
that
the
cost
is
reasonable,
use
of
a
redundant
control
system
should
be
allowed
in
lieu
of
a
CMS.
According
to
the
commenters,
a
redundant
system
(
e.
g.,
the
installation
of
a
second
carbon
bed
downstream
of
the
primary
carbon
bed)
would
be
more
economical
than
installation
and
maintenance
of
a
CMS
and
would
minimize
mercury
emissions
better.
The
commenters
stated
that
in
such
an
arrangement,
the
mercury
concentration
leaving
the
upstream
bed
would
meet
the
regulatory
requirements,
and
the
downstream
bed
would
be
the
redundant
treatment
unit.
The
commenters
recommended
that
by
periodically
checking
the
mercury
concentration
leaving
the
upstream
carbon
bed,
the
facility
can
ensure
compliance
with
the
regulation
because
the
downstream
unit
would
be
a
protective
device.

Response:
We
would
not
discourage
the
use
of
redundant
control
to
ensure
effective
control
of
the
mercury
emissions.
However,
given
our
decision
to
allow
weekly
testing
on
any
emission
stream,
we
do
not
feel
that
it
is
necessary
to
includes
provisions
for
less
frequent
monitoring
if
redundant
control
devices
are
present.

Comment:
One
commenter
(
IV­
D­
04)
stated
that
the
intent
of
the
data
collection
requirements
specified
in
§
63.8246(
a)(
1)
are
unclear.
According
to
the
commenter,
it
is
not
feasible
to
get
90
percent
operating
time
for
a
proven
system,
let
alone
the
unproven
systems
proposed
for
the
vent
streams
in
a
mercury
cell
chlor­
alkali
plant.
The
commenter
argued
that
for
a
proven
system,
achieving
a
75­
percent
on­
stream
time
represents
good
reliability.
Therefore,

the
commenter
proposed
that
the
rule
specify
a
75­
percent
operating
time
instead
of
90
percent.
71
Response:
We
agree
with
the
commenter
and
have
changed
the
minimum
data
requirements
to
75
percent.

2.8
RECORDKEEPING
AND
REPORTING
Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
suggested
changes
to
the
startup,

shutdown
and
malfunction
(
SSM)
provisions
in
§
63.8254(
c).
The
commenters
stated
that
they
believe
the
proposed
requirement
for
immediate
reporting
of
startup,
shutdown
or
malfunction
events
for
which
actions
were
taken
inconsistent
with
the
written
SSM
plan
is
overly
burdensome.

The
commenters
stated
that
this
requirement
was
removed
from
previous
batch
standards,

specifically
Subpart
JJJ
(
Polymer
&
Resin
IV,
Table
1)
and
Subpart
PPP
(
Polyether
Polyol,
Table
1).
According
to
the
commenters,
reporting
these
events
along
with
the
other
SSM
events
on
a
semi­
annual
basis
in
the
Compliance
Report
is
sufficient.

Response:
The
commenters
are
correct
that
the
Polymer
&
Resin
IV
and
Polyether
Polyol
rules
removed
the
requirement
for
immediate
reports
of
SSM
events
as
specified
by
63.10(
d)(
5)(
ii).
However,
the
rationale
for
removing
this
requirement
for
the
two
cited
rules
does
not
apply
to
this
rule,
and
the
requirement
for
immediate
reports
of
SSM
events
that
do
not
conform
to
the
SSM
plan
remains
unchanged.

The
Polymer
&
Resin
IV
and
Polyether
Polyol
rules
were
patterned
after
the
HON.
During
promulgation
and
litigation
of
the
two
cited
rules,
the
HON
itself
was
being
modified
and
several
changes
made
to
the
HON
were
brought
over
to
these
rules
to
maintain
consistency.
Dropping
the
requirement
for
immediate
reports
of
SSM
events
as
specified
by
63.10(
d)(
5)(
ii)
was
just
such
a
change.
The
comment
and
response
document
for
Polymer
&
Resin
IV
cites
to
an
intended
consistency
with
the
HON
rule
as
the
reason
for
the
change.
Since
development
of
the
Polymer
&
Resin
IV
and
Polyether
Polyol
rules,
the
EPA
has
developed
rules
with
the
HON
in
mind,
but
has
not
felt
obligated
to
maintain
complete
consistency.
While
the
requirement
for
immediate
reports
of
SSM
events
is
not
consistent
with
the
HON
or
the
cited
rules,
it
is
consistent
with
the
majority
of
rules
developed
since
those
rules.
A
quick
review
of
promulgated
rules
spanning
1999
to
2002
shows
that
requiring
immediate
reports
of
SSM
events
as
specified
by
63.10(
d)(
5)(
ii)
is
the
norm.
Further,
the
toxicity
of
mercury
warrants
more
immediate
attention
to
releases
rather
than
less.
72
Comment:
One
commenter
(
IV­
D­
07)
was
concerned
because
a
deviation
is
defined
to
include
SSM
events
that
fail
to
meet
the
emission
limits
or
work
practice
standards.
The
commenter
stated
that
they
believed
that
EPA
is
requiring
duplicative
reporting
for
SSM
events
because
these
events
are
considered
exceedances.
Therefore,
the
commenter
requested
that
EPA
make
the
following
revisions
to
§
§
63.8248,
63.8254,
and
63.8266:

§
63.8248
What
other
requirements
must
I
meet
to
demonstrate
continuous
compliance?

(
a)
Deviations.
You
must
report
each
instance
in
which
you
did
not
meet
each
emission
limitation
in
§
63.8190
that
applies
to
you.
This
includes
periods
of
startup,
shutdown,
and
malfunction.
You
must
also
report
each
instance...

§
63.8254
What
reports
must
I
submit
and
when?
***
(
b)
Compliance
report
contents.
***
(
8)
For
each
deviation
from
an
emission
limitation
(
emission
limit
and
operating
limit)
occurring
at
an
affected
source...
you
must
include
the
information
in
paragraphs
(
b)(
1)
through
(
4)
of
this
section
and
the
information
in
paragraphs
(
b)(
8)(
i)
through
(
xii)
of
this
section.
This
includes
periods
of
startup,
shutdown,
and
malfunction.

Deviation
means
any
instance
in
which
an
affected
source
subject
to
this
subpart,
or
an
owner
or
operator
of
such
a
source:
(
1)
Fails
to
meet
any
requirement
or
obligation
established
by
this
subpart
including,
but
not
limited
to,
any
emission
limitation
(
including
any
operating
limit)
or
work
practice
standard;
or
(
2)
Fails
to
meet
any
term
or
condition
that
is
adopted
to
implement
an
applicable
requirement
in
this
subpart
and
that
is
included
in
the
title
V
operating
permit
for
any
affected
source
required
to
obtain
such
a
permit;
or
.
(
3)
Fails
A
failure
to
meet
any
emission
limitation
(
including
any
operating
limit)
or
work
practice
standard
in
this
subpart
during
startup,
shutdown,
or
malfunction
is
not
considered
a
deviation
for
the
purposes
of
this
subpart.,
regardless
of
whether
or
not
such
failure
is
allowed
by
this
subpart.

Response:
We
do
not
agree
with
the
commenter
that
the
rule
requires
SSM
events
to
be
reported
twice.
The
only
time
SSM
events
are
required
to
be
reported
at
times
other
than
with
the
semiannual
compliance
report
is
when
actions
taken
during
startup,
shutdown,
or
malfunction
event
are
not
consistent
with
the
facility's
SSM
plan.
Therefore,
we
have
not
made
any
changes
to
the
final
rule
in
response
to
this
comment.
73
Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
suggested
that
an
exception
should
be
made
for
the
records
required
by
§
63.8258(
b)(
3).
The
commenters
recommended
that
to
avoid
burdensome
paperwork,
records
pertaining
to
any
required
CMS
need
only
be
retained
for
the
current
calendar
year
plus
one
year
due
to
the
large
volume
of
paper.

Response:
We
acknowledge
the
commenters'
point
that
records
of
continuous
monitoring
can
be
voluminous,
however,
the
option
to
keep
these
records
in
electronic
format
is
provided
in
the
proposed
rule.
Further,
we
feel
that
these
records
are
important
to
our
ability
to
ensure
compliance
with
the
rule.
Therefore,
we
are
not
making
any
change
related
to
records
for
continuous
monitoring
systems.
[
Note:
the
commenters
refer
to
§
63.8258(
b)(
3)
which
does
not
exist;
the
proper
references
are
§
§
63.8256(
b)(
3)
and
63.8258(
b)
which
specifies
how
long
the
records
must
be
kept.]

2.9
DEFINITIONS
Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
recommended
that
the
second
sentence
of
the
definition
for
"
Hydrogen
System"
should
be
modified
as
follows:
"
The
hydrogen
system
begins
at
the
decomposer
and
ends
just
downstream
of
the
last
control
device."
The
commenters
maintained
that
leaks
in
any
systems
downstream
of
the
last
control
device
do
not
matter.

According
to
the
commenters,
at
this
point,
it
is
acceptable
to
vent
the
hydrogen
stream
to
the
atmosphere
and
still
be
in
compliance
with
the
permit
requirements.

Response:
We
thank
the
commenters
for
this
suggested
clarification
and
have
changed
the
definition
of
"
hydrogen
system"
to
read
as
follows:

Hydrogen
system
means
all
vessels,
piping,
and
equipment
that
convey
a
by­
product
hydrogen
stream.
The
hydrogen
system
begins
at
the
decomposer
and
ends
at
the
point
just
downstream
of
the
last
control
device.
The
hydrogen
system
includes
all
control
devices.

Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
07)
requested
that
the
definition
of
"

byproduct
hydrogen
stream"
be
deleted
because
it
is
the
same
as
"
hydrogen
system".

Response:
The
commenters
did
not
offer
any
technical
reasons
for
deleting
the
definition
of
"
by­
product
hydrogen
stream."
We
do
not
see
any
possible
reason
for
deleting
this
definition,
as
we
see
them
as
very
different
concepts.
Therefore,
we
are
not
making
any
change
related
to
the
definition
of
these
two
terms.

2.10
ECONOMIC
AND
BENEFITS
ANALYSIS
74
Comment:
Two
commenters
(
IV­
D­
04,
IV­
D­
05)
stated
that
the
Agency's
estimation
of
the
costs
required
to
comply
with
both
the
floor
standard
and
the
"
beyond­
the­
floor"
standard
are
inaccurate.
According
to
one
commenter
(
IV­
D­
04),
EPA
estimated
that
it
will
cost
the
industry
approximately
$
660,000
in
total
to
install
controls
to
comply
with
the
MACT
floor.
Total
annual
operating
costs
for
all
the
affected
facilities
(
which
includes
debt
service
on
the
capital
cost
value)

were
estimated
to
be
$
570,000.
However,
the
commenter
noted
that
EPA
did
not
present
the
cost
bases
for
these
estimates
in
the
preamble.
The
commenter
estimated
that
it
will
cost
the
industry
millions
of
dollars
to
meet
the
required
floor
limitations.
Furthermore,
the
commenter
stated
that
EPA's
estimate
of
the
cost
to
meet
the
beyond
the
floor
limitation,
an
additional
$
210,000
in
capital
costs
($
150,000
in
operating
costs)
for
the
nine
affected
facilities,
is
inaccurate.
Again,
EPA
did
not
present
a
cost
basis
in
the
preamble
for
this
estimate.
The
commenter
maintained
that
the
costs
to
meet
the
"
beyond­
the­
floor"
value
are
likely
to
be
in
excess
of
the
$
15­
20,000
per
plant
value
presented
by
EPA.
Concluding
that
EPA
had
not
adequately
justified
setting
the
standards
at
beyond­
the­
floor
levels,
Commenter
IV­
D­
04
stated
that
the
standard
should
be
set
at
the
floor
levels.

Response:
The
commenter
has
not
provided
any
specific
data
or
rationale
to
refute
our
economic
analysis.
Therefore
we
stand
by
our
original
analysis
and
are
not
proposing
any
changes
to
the
economic
analysis.
We
believe
we
have
justified
setting
the
standards
at
beyondthe
floor
levels
and,
with
the
exception
of
the
hydrogen
by­
product
stream
and
end­
box
ventilation
system
vents,
we
are
not
changing
the
proposed
emission
limits.
In
response
to
the
commenter's
statement
that
the
basis
for
the
cost
estimates
were
not
presented
in
the
preamble,
it
has
been
EPA
policy
for
some
time
to
save
Federal
Register
printing
costs
by
presenting
the
bulk
of
the
rationale
and
basis
for
different
analyses
in
the
Background
Information
Document
(
BID).

The
basis
for
all
costs
included
in
the
economic
evaluation
are
presented
in
Section
6.0
of
the
BID.
The
BID
can
be
obtained
from
the
EPA.

Comment:
One
commenter
(
IV­
D­
05)
felt
that
the
proposed
NESHAP
drastically
understates
the
costs
that
facilities
will
likely
incur
to
comply.
The
commenter
has
already
committed
to
spend
$
2.3
million
dollars
to
change
out
hydrogen
coolers,
seal­
less
mercury
pumps,
and
upgrading
and
sealing
the
concrete
cell
support
beams.
Additional
projects
to
change
the
design
of
the
cell
end
boxes
and
nickel­
lining
the
decomposer
will
cost
approximately
75
$
780,000.
These
costs
do
not
account
for
the
additional
manpower
needed
to
provide
documentation
or
to
buy
the
types
of
sophisticated
instruments
and
monitors
needed
to
meet
many
of
the
proposed
NESHAP's
recordkeeping
and
monitoring
requirements.
The
commenter
is
anticipating
the
need
to
hire
5
additional
staff
at
a
cost
of
$
375,000
annually
to
fully
comply
with
the
inspection,
recordkeeping
and
leak­
response
requirements
in
the
NESHAP
proposal.

The
commenter
also
anticipates
approximately
$
100,000
in
capital
costs
for
the
purchase
and
installation
of
continuous
monitors
for
cell
point
sources,
and
approximately
$
200,000
for
the
cell
room
monitor
system.
Maintenance
and
calibration
costs
will
be
an
additional
cost,
which
the
commenter
could
not
accurately
predict
at
this
time.

Response:
We
believe
the
commenter
is
making
three
points
 
capital
costs
are
higher
than
estimated
by
the
EPA;
manpower
costs
for
ongoing
compliance
activities
are
higher
than
estimated;
and
costs
for
the
cell
room
continuous
mercury
monitoring
system
is
higher
than
estimated.

The
EPA
commends
the
commenter
for
updating
their
facility
with
the
purchase
of
new
hydrogen
coolers,
seal­
less
mercury
pumps,
and
the
upgrading
and
sealing
of
the
concrete
cell
support
beams.
However,
while
these
actions
will
improve
the
overall
environmental
performance
of
this
facility,
we
do
not
believe
that
these
actions
are
specifically
required
for
compliance
with
the
proposed
standards,
and
therefore
did
not
include
them
in
our
estimates
of
costs
for
the
standards.

Addressing
the
commenter's
estimated
costs
for
compliance
activities
related
to
recordkeeping
and
monitoring
activities,
we
provided
rationale
for
our
estimates
of
manpower
and
the
cost
of
that
manpower.
The
commenter
did
not
provide
rationale
for
the
projected
cost
of
5
additional
staff
at
an
annual
cost
of
$
375,000.
Nor
did
the
commenter
refute
our
rationale
or
estimates
for
manpower
costs.
Therefore,
we
do
not
see
the
need
to
reevaluate
our
original
estimates
of
manpower
costs.

Again,
the
commenter
provided
costs
for
a
mercury
cell
room
monitoring
system
but
did
not
provide
rationale
or
the
basis
for
the
provided
cost
estimate,
and
the
commenter
did
not
refute
the
rationale
or
costs
we
provided
as
part
of
proposing
the
standards.
Therefore,
we
do
not
see
the
need
to
reevaluate
our
original
estimates
for
the
mercury
cell
room
continuous
monitoring
system.
9Memorandum,
from
Bhatia,
K.,
EC/
R
Incorporated,
to
Rosario,
I.,
EPA/
OAQPS/
ESD//
MG.
September
26,
2001.
Background
on
Vent
Control
System
Enhancements
to
Meet
Regulatory
Alternatives
for
Existing
Mercury
Emission
Sources
at
Mercury
Cell
Chlor­
Alkali
Plants.
EPA
Air
Docket
A­
2000­
02,
Number
II­
B­
22.

76
Comment:
One
commenter
(
IV­
D­
04)
called
EPA's
claim
that
168
lb/
year
(
0.46
lb/
day)
of
mercury
would
be
collectively
reduced
from
the
nine
affected
plants
"
speculative."
The
commenter
noted
that
EPA's
statement
that
a
168
lb/
year
reduction
would
be
a
48
percent
incremental
reduction
from
the
floor
reductions
is
erroneous.
If
the
floor
option
results
in
an
actual
reduction
of
1,225
lb/
year
mercury
emissions,
than
reducing
another
168
lb/
year
is
only
an
incremental
reduction
of
14
percent,
not
48
percent.

Response:
We
feel
the
commenter's
primary
point
is
that
our
estimation
of
expected
emission
reductions
is
speculative.
We
strongly
disagree.
The
estimation
of
emission
reductions
is
based
on
allowable
emissions
under
the
Part
61
Mercury
NESHAP,
actual
emissions
reported
by
industry,
and
calculated
emission
rates
expressed
as
mass
mercury
emitted
per
mass
chlorine
produced.
Calculating
the
various
emission
reductions
is
a
simple
math
exercise.
The
portion
of
our
evaluation
that
is
subject
to
judgment
and
a
proper
understanding
of
technical
points
is
the
determination
of
what
controls
will
be
required
for
each
plant
in
order
to
achieve
the
specified
emission
limits.
The
selection
of
controls
for
each
plant
and
their
performance
is
documented
in
the
BID
and
in
a
memorandum
in
the
docket.
9
The
commenter
did
not
provide
comments
on
the
selection
of
controls
or
their
performance,
therefore
we
are
not
persuaded
to
reevaluate
this
portion
of
our
analysis.

Addressing
the
comment
about
incremental
emission
reduction,
the
commenter
has
misunderstood
our
calculation.
Incremental
emission
reduction
represents
the
emission
reduction
achieved
in
moving
from
the
floor
to
beyond­
the­
floor
level
of
control
divided
by
the
emissions
allowed
at
the
floor
level
of
control
or:

Incremental
Emission
Reduction
s
Floor
Emis
sions
*
100
168
lb
/
yr
350
lb
/
yr
*
100
48
%








=
77
When
this
calculation
is
performed,
the
result
is
an
incremental
emission
reduction
of
48
percent.

The
commenter
has
taken
the
incremental
emission
reduction
of
168
lb/
year
and
divided
it
by
the
emission
reductions
achieved
by
the
floor
level
of
control;
this
is
not
the
calculation
we
were
representing.

As
a
point
of
clarification,
the
168
lb/
year
represents
the
emission
reduction
for
hydrogen
streams
and
end­
box
ventilation
system
vents
only.
The
total
point
source
emission
reductions
achieved
in
moving
from
the
floor
level
of
control
to
beyond­
the­
floor
levels
is
194
lb/
year;
this
total
(
considering
rounding
errors)
includes
the
cited
168
lb/
year,
14
lb/
year
for
plants
without
end­
box
ventilation
systems,
and
13
lb/
year
for
mercury
thermal
recovery
unit
vents.
