SEQ CHAPTER \h \r 1 	6560-50-P

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2002-0051; FRL-    ]

RIN 2060-AJ78

National Emission Standards for Hazardous Air Pollutants

From the Portland Cement Manufacturing Industry

AGENCY:  Environmental Protection Agency (EPA).

ACTION:  Final Rule

SUMMARY:  On June 14, 1999, under the authority of section 112 of the
Clean Air Act (CAA), the EPA promulgated national emission standards for
hazardous air pollutants (NESHAP) for new and existing sources in the
portland cement manufacturing industry.  On December 15, 2000, the
United States Court of Appeals for the District of Columbia Circuit
(D.C. Circuit) remanded parts of the NESHAP for the portland cement
manufacturing industry to EPA to consider, among other things, setting
standards based on the performance of the maximum achievable control
technology (MACT) floor standards for hydrogen chloride (HCl), mercury,
and total hydrocarbons (THC), and metal hazardous air pollutants (HAP).

We published a proposed response to the court’s remand on December 2,
2005.  We received over 1700 comments on our proposed response.  This
action promulgates EPA’s final rule amendments in response to the
court’s remand and the comments received on the proposed amendments.

DATES: This final rule is effective on [INSERT DATE OF PUBLICATION IN
THE FEDERAL REGISTER]

ADDRESSES:  EPA has established a docket for this action under Docket ID
No. EPA-HQ-OAR-2002-0051.  All documents in the docket are listed on the
  HYPERLINK "http://www.regulations.gov"  www.regulations.gov  web site.
Although listed in the index, some information is not publicly
available, e.g., CBI or other information whose disclosure is restricted
by statute.  Certain other material, such as copyrighted material, is
not placed on the Internet and will be publicly available only in hard
copy form.  Publicly available docket materials are available either
electronically through   HYPERLINK "http://www.regulations.gov"
www.regulations.gov  or in hard copy at the EPA Docket, EPA/DC, EPA
West, Room 3334, 1301 Constitution Ave., NW, Washington, DC.  The Public
Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday,
excluding legal holidays.  The telephone number for the Public Reading
Room is<PHONE_NUMBER>, and the telephone number for the EPA Docket
Center is<PHONE_NUMBER>.

FOR FURTHER INFORMATION CONTACT:  Mr. Keith Barnett, EPA, Office of Air
Quality Planning and Standards, Sector Policies and Programs Division,
Metals and Minerals Group (D243-02), Research Triangle Park, NC 27711;
telephone number<PHONE_NUMBER>; facsimile number<PHONE_NUMBER>; e-mail
address<EMAIL_ADDRESS>

SUPPLEMENTARY INFORMATION:

I.   General Information

A.  Does this action apply to me?  Entities potentially affected by this
action are those that manufacture portland cement.  Regulated categories
and entities include:

Table 1.  Regulated Entities Table

Category	NAICS1	Examples of regulated entities

Industry	32731	Owners or operators of portland cement manufacturing
plants.

State	32731	Owners or operators of portland cement manufacturing plants.

Tribal associations	32731	Owners or operators of portland cement
manufacturing plants.

Federal agencies	None	None.

1 North American Industry Classification System

	This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be regulated by this
action.  This table lists the types of entities that may potentially be
regulated by this action.  To determine whether your facility is
regulated by this action, you should carefully examine the applicability
criteria in 40 CFR 63.1340 of the rule.  If you have questions regarding
the applicability of this action to a particular entity, consult the
person listed in the preceding FOR FURTHER INFORMATION CONTACT section.

B.  Judicial Review.  The NESHAP for the Portland Cement Manufacturing
Industry were proposed in December 2, 2005 (70 FR 72330).  This action
announces EPA(s final decisions on the NESHAP.  Under section 307(b)(1)
of the CAA, judicial review of the final NESHAP is available only by
filing a petition for review in the U.S. Court of Appeals for the
District of Columbia Circuit by [INSERT DATE 60 DAYS FROM DATE OF
PUBLICATION OF THIS FINAL RULE IN THE FEDERAL REGISTER].  Under section
307(d)(7)(B) of the CAA, only an objection to a rule or procedure raised
with reasonable specificity during the period for public comment can be
raised during judicial review.  Moreover, under section 307(b)(2) of the
CAA, the requirements established by the final NESHAP may not be
challenged separately in any civil or criminal proceeding brought to
enforce these requirements.

C.  How is this Document Organized?  The information presented in this
preamble is organized as follows:

I.  General Information

II.  Background

III.  Summary of the National Lime Association v. EPA Litigation

IV.  EPA's Final Action in Response to the Remand

A.  Determination of MACT for Mercury Emissions

B.  Determination of MACT for HCl Emissions

C.  Determination of MACT for THC Emissions

D.  Evaluation of a Beyond-the-floor Control Option for

    Non-Volatile HAP Metal Emissions

V.  Other Rule Changes

VI.  Responses to Major Comments

VII.  Summary of Environmental, Energy, and Economic Impacts

A.  What facilities are affected by the final amendments?

B.  What are the air quality impacts?

C.  What are the water quality impacts?

D.  What are the solid waste impacts?

E.  What are the energy impacts?

F.  What are the cost impacts?

G.  What are the economic impacts?

VIII.  Statutory and Executive Order Reviews

  SEQ CHAPTER \h \r 1 A.  Executive Order 12866, Regulatory Planning and
Review

B.  Paperwork Reduction Act

C.  Regulatory Flexibility Analysis

D.  Unfunded Mandates Reform Act

E.  Executive Order 13132, Federalism

F.  Executive Order 13175, Consultation and Coordination

    with Indian Tribal Governments

G.  Executive Order 13045, Protection of Children from

    Environmental Health Risks and Safety Risks

H.  Executive Order 13211, Actions that Significantly

    Affect Energy Supply, Distribution, or Use

I.  National Technology Transfer and Advancement Act

J.  Congressional Review Act

II.  Background

Section 112(d) of the CAA requires EPA to set emissions standards for
major stationary sources based on performance of the MACT.  The MACT
standards for existing sources must be at least as stringent as the
average emissions limitation achieved by the best performing 12 percent
of existing sources or the best performing five sources for source
categories with less than 30 sources (CAA section 112(d)(3)(A) and (B)).
 This level is called the MACT floor.  For new sources, MACT standards
must be at least as stringent as the control level achieved in practice
by the best controlled similar source (CAA section 112(d)(3)).  The EPA
also must consider more stringent "beyond-the-floor" control options.
When considering beyond-the-floor options, EPA must consider not only
the maximum degree of reduction in emissions of HAP, but must take into
account costs, energy, and nonair environmental impacts when doing so.

	On June 14, 1999 (64 FR 31898), in accordance with these provisions,
EPA published the final rule entitled “National Emission Standards for
Hazardous Air Pollutants From the Portland Cement Manufacturing
Industry” (40 CFR part 63, subpart LLL).

	The legacy public docket for the final rule is Docket No. A-92-53.  The
final rule provides protection to the public by requiring portland
cement manufacturing plants to meet emission standards reflecting the
performance of the MACT.  Specifically, the final rule established
MACT-based emission limitations for particulate matter (as a surrogate
for non-volatile HAP metals), dioxins/furans, and for greenfield new
sources, THC (as a surrogate for organic HAP).  We considered, but did
not establish limits for, THC for existing sources and HCl or mercury
for new or existing sources.    SEQ CHAPTER \h \r 1  In response to the
mandate of the District of Columbia Circuit arising from litigation
summarized below in this preamble, on December 2, 2005, we proposed
amendments addressing standards for these pollutants.  We received over
1700 comments on the proposed amendments.  Most of these comments
addressed the lack of a mercury emission limitation in the proposed
amendments.  Today’s final action reflects our consideration of these
comments.  	We have previously amended the Portland Cement NESHAP.
Consistent with the terms of a settlement agreement between the American
Portland Cement Alliance and EPA, EPA adopted final amendments and
certain interpretative clarifications to the rule on April 5, 2002 (76
FR 16614), July 5, 2002 (67 FR 44766), and December 6, 2002 (67 FR
72580).  These amendments generally relate to the rule’s
applicability, and to the performance testing, and monitoring provisions
of the rule.  In today’s action, we are also amending the rule to
re-insert two paragraphs relating to the applicability of the portland
cement new source performance standards that were deleted in error in a
previous amendment.

III.  Summary of the National Lime Association v. EPA Litigation

	Following promulgation of the NESHAP for portland cement manufacturing,
the National Lime Association and the Sierra Club filed petitions for
review of the standards in the D.C. Circuit.  The American Portland
Cement Alliance, although not a party to the litigation, filed a brief
with the court as amicus curiae.  The court denied essentially all of
the petition of the National Lime Association, but granted part of the
Sierra Club petition.    SEQ CHAPTER \h \r 1

	In National Lime Association v. EPA, 233 F. 3d 625 (D.C. Cir. 2000),
the court upheld EPA’s determination of MACT floors for particulate
matter (PM) (as a surrogate for non-volatile HAP metals) and for
dioxin/furan.  However, the court rejected EPA’s determination that it
need not determine MACT floors for the remaining HAP emitted by these
sources, namely, mercury, other organic HAP (for which THC are a
surrogate), and HCl (233 F. 3d at 633).  The court specifically rejected
the argument that EPA was excused from establishing floor levels because
no “technology-based pollution control devices” exist to control the
HAP in question (Id. at 634).  The court noted that EPA is also
specifically obligated to consider other pollution-reducing measures
including process changes, substitutions of materials inputs, or other
modifications (Id.).  The court remanded the rule to EPA to set MACT
floor emission standards for HCl, mercury, and THC.

	The Sierra Club also challenged EPA’s decision not to  set
beyond-the-floor emission limits for mercury, THC, and non-volatile HAP
metals (for which PM is a surrogate).  The court only addressed the
absence of beyond-the-floor emission limits for non-volatile HAP metals
since EPA was already being required to reconsider MACT floor emission
standards for mercury, THC, and HCl, and thus, by necessity, also must
consider whether to adopt beyond-the-floor standards for these HAP.  The
Sierra Club argued, and the court agreed, that in considering
beyond-the-floor standards for non-volatile HAP metals, EPA considered
cost and energy requirements but did not consider nonair quality health
and environmental impacts as required by the CAA (Id. at 634-35).  The
court also found EPA’s analysis of beyond-the-floor standards
deficient in its assertion that there were no data to support fuel
switching (switching to natural gas) as a viable option of reducing
emissions of non-volatile HAP metals (Id. at 635).

IV.  EPA's Final Action in Response to the Remand

Determination of MACT for Mercury Emissions

1.  Floor Determinations

	In developing the proposed amendments we systematically evaluated all
possible means of developing a quantified floor standard for mercury
emissions from these sources, including both back end technology-based
pollution control devices and front end feed and fuel control.  See
National Lime, 233 F. 3d at 634 (finding that EPA had erred in examining
only technological (i.e., back-end) controls in considering a level for
a mercury floor).  We also were unable to devise any type of work
practice standard that would result in mercury emissions reductions (70
FR 72332 – 72335, December 2, 2005).

	In response to comments on the proposed standards, we have performed
additional evaluations of potential floors for mercury emissions (and
also performed additional evaluations of beyond-the-floor options for
mercury control). We obtained additional mercury emissions test data
during and after the two comment periods for the proposed amendments and
once again evaluated setting a floor based on the median of the 12
percent of the kilns demonstrating the lowest mercury emissions in stack
tests.  We discuss each of these possibilities in turn below.

Control of Mercury in Primary Raw Materials and Fossil Fuels

         i.  Mercury Emission Levels Reflecting Raw Material and Fossil
Fuel Contributions are Inherently Site-Specific

As stated at proposal, mercury emissions come from the predominant input
to a cement kiln by volume: the limestone which is the chief raw
material for the kiln.  Small amounts of mercury also are found in other
raw material inputs to the process.  Fossil fuel, almost always coal, is
the other source of mercury emissions.  Mercury levels in limestone vary
enormously, both within a single quarry and between quarries, the result
being that a single source may be unable to replicate its own
performance in different tests, and could not duplicate a second
source’s performance since a kiln lacks access to any other kiln’s
limestone.  Mercury levels in coal likewise vary significantly, although
mercury emissions due to coal are normally swamped by the emissions
attributable to limestone (70 FR 72333-34).  We must, of course, account
for sources’ variability in establishing a MACT floor.  Mossville
Environmental Action Now v. EPA, 370 F. 3d 1232, 1241-42 (D.C. Cir.
2004).

In an attempt to quantify the potential variability, we looked to see if
there were facilities with multiple stack tests for mercury.  We do have
multiple test results for one of the lowest mercury emitters in the data
base.  During the first test with the raw mill on the facility was one
of the lower emitting facilities in the source category demonstrating
emissions of 7.8 µg/dscm (all test values are corrected to seven
percent oxygen).  During a second test eight years later (reflecting raw
materials from the same quarry) mercury emissions with the raw mill on
were 60 µg/dscm, a variability factor of roughly 8 times.  We could
identify no facility operational changes between the times of the two
tests that would account for this large difference in mercury emissions.

We also obtained data from a facility that was retested for mercury in
July 2005 within three months of an initial test.  With the raw mill on
mercury emissions averaged 0.00138 pounds per hour in the April test and
0.00901 pounds per hour in the July test, a variability factor of 7.
With the raw mill off emissions averaged 0.00823 pounds per hour in the
April test and 0.0189 pounds per hour in the July test.  We also noted
that during the April test mercury emissions with the raw mill off were
below mercury emissions with the raw mill on in the July test.  Because
it is known that when the raw mill is on the raw meal adsorbs mercury,
thereby reducing measured mercury emissions in the short term, we can
only assume that the uncontrolled variation in the mercury levels in the
raw materials – all of which come from the same quarry -- was so great
between the two tests that it negated the effect of the operating
condition of the raw mill.

We also assessed potential variability by examining  daily variations in
cement kilns’ raw materials and fuel mercury contents.  We obtained
data from an operating facility that analyzed samples of raw material
and fuel each day over a 30 day period.  We calculated average daily
emissions assuming all the mercury in the raw materials and fuel was
emitted.  The average daily emissions would vary from a low of 0.09 lb
to a maximum of 16.44 lb, or a factor of 183 (See Summary of Mercury
Test data in Docket 2002-0051).

These are enormous swings in variability.  Variability of emissions
based on the operation of air pollution controls are typically lower
that those shown above because air pollution controls are typically
designed to meet certain percent reduction or outlet emissions levels
and to account for variations in inlet conditions.  Moreover, it is
virtually certain that the variability reflected in these results fails
to cabin the total raw material and emissions variability experienced by
the plants in the source category, since we have only a handful of
results.  These data confirm our tentative conclusion at proposal that
constantly changing concentrations of mercury in kiln inputs leave no
reliable way to quantify that variability.  70 FR 72333.

In the proposed amendments we also evaluated requiring facilities to
switch from coal to natural gas as a method to reduce mercury emissions,
or requiring use of so-called clean coal (70 FR 72333-34).  We
tentatively concluded that this was not feasible on a national basis due
to insufficient supply and lack of infrastructure, and reiterate that
conclusion here.  One commenter noted that petroleum coke was another
fuel that is lower in mercury and is currently used as a cement kiln
fuel.  However, a mercury standard based on requiring fuel switching to
petroleum coke suffers from the same defects as requiring facilities to
switch to natural gas.  This fuel may not be available in all areas of
the country and there may not be sufficient availability of the fuel to
replace a significant percentage of the coal burned in cement kilns.
Petroleum coke is a byproduct of petroleum refining, therefore the
supply is limited by the demand for refined petroleum fuels.  Petroleum
coke has a low volatile matter content which can lead to ignition
problems if burned without a supplemental fuel.  It also typically has a
higher sulfur content than coal.  This can adversely affect kiln
refractory life and increase internal corrosion of the kiln shell.  As
previously noted, each individual facility has specific requirements for
raw material additives based on the chemical composition of its
limestone.  The minerals present in the coal ash fulfill part of those
requirements.  Therefore, replacing part or all of the coal currently
used at a facility with petroleum coke, which has almost no ash, may
force that the facility to incorporate additional raw material additives
containing mercury to compensate for the loss of the coal ash.

We thus adhere to the tentative conclusion reached at proposal: front
end feed and fuel control of cement kilns is inherently site specific,
and basing limits on kiln performance in individual performance tests
which reflect only those inputs will result in limitations that kilns
can neither duplicate (another kiln’s performance) nor replicate (its
own).

ii.	Implications of Permit Limits for Mercury

There are currently 19 cement kilns (out of 70 cement kilns for which we
reviewed permit requirements) that have limits for mercury.  At first
blush, it might be argued that these permit limits demonstrate that
variability of mercury emissions can be controlled, since sources must
comply with the limitations.  It might further be argued that these
permit limits are “emission limitations achieved”, the statutory
basis for establishing floors for existing sources under section
112(d)(3).  For new sources, the lowest permit limit is a measure of
performance of the “best controlled source” (the permit itself being
the means of control).  We have determined, however, that for most
facilities, the permit limit was established based on an estimate
provided by the facility of the annual amounts of mercury that would
enter the kiln with the raw materials and fuels.  One facility had a
mercury limit based on its estimated annual emission from an emissions
test, and one facility had a limit based on a State law.  We could find
no cases where a facility actually has had to take any steps, either
through the imposition of process changes or add-on controls, to reduce
its mercury emissions as a result of these permit limits.  See
“Summary of Cement Kiln Permit Data for Mercury” in the docket.

We considered the option of setting an emissions limit, either on a
pounds per year or a pound per ton of clinker basis, based on the median
of the top 12 percent of the 17 kilns with permit limitations.  However,
we repeat that none of the facilities with permit limits were required
to actually take action to reduce mercury emissions.  Their limits were
all based on site specific factors (expected maximum conceivable levels
of mercury emissions), and were set at a level that did not require the
imposition of add-on controls, feed or fuel substitution, or any other
constraint.  Any limit we set based on these permits would require that
at least some facilities apply beyond-the-floor control technology to
meet the limit since feed and fuel control via substitution is not
possible.  Such a standard would impermissibly apply beyond-the-floor
emission control without consideration of costs and other nonair
environmental impacts.

We also considered a limit where each facility would set their own site
specific limit based on the same procedures the facilities with permits
used: determining in the course of the permitting process what its
maximum conceivable mercury emissions are likely to be based on the
facility’s raw material and fuel inputs, and tacking on an additional
variability factor.  However, this would require that we set a separate
limit for each facility, with each facility being its own subcategory
(i.e. a different type of facility) based on its site specific raw
materials and fuels. See 70 FR 72334, alluding to this possibility. EPA
has great discretion in deciding whether or not to subcategorize within
a source category.  We do not believe a decision to individually
subcategorize is warranted considering the fact that the result will be
no discernable environmental benefit because conduct will be unaltered.
Chemical Mfr’s Ass’n v. EPA, 217 F. 3d 861, 866-67 (D.C. Cir. 2000)
(arbitrary and capricious for EPA to impose costly regulatory
obligations without some showing that the requirement furthers the Clean
Air Act’s environmental goals).

Therefore, we have determined that even though these permit limits
exist, they have not resulted in a quantifiable reduction of mercury
emissions.  Any option to develop a MACT floor for mercury with these
limits would either result in an unnecessarily complex rule with no
environmental benefit, or a rule which improperly imposes a de facto
beyond-the-floor standard without the required consideration of costs
and nonair quality impacts.

iii.	Why not Average the Performance Test Data?

      Some commenters stated that EPA must simply average the results of
the 12 per cent lowest mercury performance test data to establish the
floor for existing sources, and establish the new source performance
floor at the level of the lowest test result.  We rejected this approach
at proposal, and do so here, because it fails to account for the
variability of mercury levels in raw materials and fuels and hence
variability in performance.  See 70 FR 72335; see also 70 FR 59436 (Oct.
12, 2006).  The only way all kilns, including the kilns with the lowest
emission levels in individual tests, could meet this type of standard
continuously, as required, would be to install backend technology-based
control equipment. However, this would be a de facto beyond-the-floor
standard, adopted impermissibly because of failure to assess cost,
energy, and nonair environmental impacts.  See 70 FR 72335.

We are aware that in the case of the NESHAP for Industrial, Commercial,
and Institutional Boilers and Process Heaters (Boiler NESHAP), we used
short term emissions data and applied a variability factor to determine
a floor for mercury emissions (69 FR 55236, September 13, 2004).  We do
not believe that approach is applicable to the portland cement source
category.  First, in the case of the Boiler NESHAP the floor was based
on performance of a control technology, fabric filters, which means that
facilities were exercising some control over mercury emissions and
variability could be realistically cabined and qualified, so that an
emission limit could be replicable and duplicable.  Though the majority
of cement kilns also use fabric filters, the collected particulate in
this source category consists of product and, to some extent,
unprocessed raw materials.  As a result most of the collected
particulate is recycled back to the process, largely negating any impact
of the particulate control technology on mercury emissions.  Second, the
variabilities seen as a result of fuel inputs in the Boiler NESHAP are
much lower than the variabilities indicated in the portland cement
industry where the mercury fuel variability is a distant second to the
enormous variability of mercury in the raw materials.  We do not believe
the data exist to accurately quantify this variability.

Another option we considered was using long term data to set a floor.
However, to our knowledge, since continuous emission monitors for
mercury have not been demonstrated on cement kilns, and none currently
exist on cement kilns, there is no long term stack performance data on
mercury emissions from cement kilns that we could use to set a numerical
emissions limit.  The only available long term data of which we are
aware is from several facilities which have a requirement to perform
monthly analyses of composited daily samples of fuels and raw materials
to calculate a 12 month mercury emissions total.  However, all these
kilns are located in one state (Florida) with unrepresentatively low
levels of mercury in limestone (so far as we can determine). We do not
believe these data would be representative of the source category as a
whole.  More basically, basing a standard on one set of kilns’ raw
material inputs still suffers from the defect that no facility has
access to another’s raw materials.

b.	Floors for Facilities Using Utility Fly Ash as Raw Material

Some cement kilns use utility fly ash as an alternative raw material to
replace shale or clay.  These kilns replace a natural material, shale,
with a secondary material (i.e. a recycled air pollution control
residue), fly ash.  Approximately 34 cement manufacturing facilities are
currently using utility boiler fly ash as a feedstock.  We reviewed the
available data and have come to the conclusion that cement kilns using
fly ash are a different type of kiln, within the meaning of section 112
(d) (1) of the Act, and that for cement kilns currently using fly ash,
the current use would be considered the MACT floor.  Our reasoning is as
follows.

Use of fly ash can have an effect on mercury emissions since fly ash
contains mercury in varying amounts. As discussed below, mercury
emissions may be higher or lower depending on the amounts of mercury
involved vis-a-vis the raw materials that would otherwise be used (if
available).  But as also explained more fully below, some cement kilns
using fly ash do not have an alternative raw material source.  Given
that these kilns use a different raw material, not always replaceable,
and that the material affects mercury emissions, we believe that these
kilns are a separate kiln type, and hence a separate subcategory, for
purposes of mercury emissions.  For a similar conclusion see 64 FR at
52871 (Sept. 30, 1999) (cement kilns that choose to burn hazardous waste
in place of fossil fuels are a separate source category for MACT
purposes).

We attempted to determine if, in general, facilities that use fly ash
have higher emissions of mercury than those that do not.  An analysis of
data for the EPA’s toxic release inventory and the National Emissions
Inventory did not show differences significant enough that we could draw
any definitive conclusions.  We considered reviewing the available
mercury emissions test data to determine if we could discern a trend.
However, as previously discussed, we do not believe these data are
representative of long term mercury emissions.  We also attempted to
obtain data on the important issue of the amounts and mercury contents
of fly ash used relative to other raw materials.  These data apparently
do not exist with one exception (discussed in the next paragraph).  We
do know that the two highest mercury emitting facilities (in individual
performance tests) do not use fly ash.  Without data on the actual
mercury contributions of all materials, we do not believe we can draw
any valid general conclusions on the impact of the use of fly ash on
mercury emissions.

We do have detailed data from one facility that used fly ash where fifty
percent of the total mercury input to the kiln is in the fly ash.
However, even for this facility, we cannot accurately quantify the
impact on mercury emissions of the decision to replace the shale used at
this facility with fly ash because we have been unable to obtain data on
the mercury content of the shale the fly ash replaced.  We also have no
mercury analysis data from the time period when the facility used shale.

There are other factors to consider when we evaluate the environmental
effects - generally quite positive -- of substituting fly ash for shale
or clay.  First, fly ash in general has a lower organic material content
than shale or clay.  At the facility just mentioned, replacing the shale
with fly ash reduced emissions of THC from around 80 ppmv to 3 ppmv.
Because fly ash can reduce kiln fuel consumption, it reduces emissions
of SO2, NOx, and carbon monoxide.  Using fly ash as a kiln feed reduces
the landfill requirements for disposal of utility fly ash.  Use of fly
ash reduces cement plant power consumption because it is usually fine
enough that it can be added directly to the kiln rather then being
ground in a mill.  Use of fly ash also reduces fuel consumption because
compared to the raw materials it typically replaces it is already highly
calcined; it does not have the types of large crystals as the raw
materials it replaces (this improves burnability); some fly ashes have
lower metal alkali content, thus avoiding hard burning to drive off
alkali metals and reducing the need to operate the alkali bypass; it is
drier than quarried materials, thus saving fuel used to dry materials.
Many domestic cement plants have high pyrites in their quarry,
especially in the shale or clay. In most cases, this pyrite is the main
source of SO2 emissions from the kiln. Using fly ash can significantly
reduce the SO2 emissions that result from pyrite in the raw materials.

It should also be noted that there are at least two new facilities whose
permits specifically required use of fly ash as their alumina source, so
they have no source for shale or clay, the primary material alternatives
for alumina.  Finally, a facility that currently uses fly ash may not be
able to return to using the natural (i.e. primary) raw materials it
replaced.  For example, if the replaced raw materials were shale, the
shale quarry may now be closed and the facility may not have access to a
suitable shale supply.

Given the lack of any data to positively state the impact of fly ash on
mercury emissions for the source category in general, as well as the
positive environmental effects of using fly ash, there is no basis for a
floor standard based on substituting other potential raw materials (such
as shale or clay) for fly ash.  At the same time, we do not see any
means of identifying a floor for existing fly ash users based on
substituting different fly ash types reflecting different mercury
content.  The recycled fly ash is not fungible.  Cement kilns must
carefully select only fly ash with needed properties within a relatively
small tolerance.  Cement kilns also usually are limited to fly ash
available from boilers which are reasonably close to the kiln (typically
within a few hundred miles) or shipping expense becomes prohibitive.
The fly ash selection process is involved; it has taken years for kilns
to identify a suitable fly ash source.  Accordingly, we evaluate fly ash
like the other raw material inputs into cement kilns, and do not believe
that a floor based on control based on substitution of either raw
materials or other fly ash because the input is variable and
uncontrollable.  We discuss in section IV.A.2   below the one exception
to this conclusion for fly ash where the mercury content has been
artificially increased by sorbent injection.

c.	Control of Collected Particulate (Cement Kiln Dust)

There are two operation factors that impact measured mercury emissions
at the kiln stack.  These are the use of in-line raw mills and the
recycling of cement kiln dust (CKD).

Many (but not all) kiln systems have in-line raw mills.  In these
systems the kiln exhaust gas is routed through the raw mill to dry the
raw materials.  This process results in mercury contained in the flue
gas being adsorbed by the raw meal.  This results in an apparent
reduction if mercury emissions are being measured at the kiln stack.
However, the captured mercury is reintroduced into the kiln which
creates a recycle loop of mercury until the captured mercury eventually
escapes and is emitted to atmosphere.  Also, raw mills do not run
continuously.  When the raw mill is turned off, this effect of raw meal
adsorption of mercury is negated and mercury emissions appear to
increase.  However, the increase is actually mercury that would have
previously been emitted but was captured by the raw meal and returned to
the kiln.  The net effect is that an in-line raw mill does not increase
or reduce mercury emissions over the long term, it simply alters the
time at which the mercury is released.

Mercury is also adsorbed on the CKD collected in the particulate control
device, typically a fabric filter or an ESP.  Because the collected CKD
mainly consists of product, and sometimes small amounts of raw
materials, the collected CKD is recycled back to the kiln to the extent
possible.  The portion that cannot be recycled to the kiln is either
sent to a landfill, or used in some other manner (i.e. some type of
beneficial use).  Most facilities require that a portion of the CKD be
removed from the kiln system rather than returned to the kiln.  This is
done to bleed the kiln system of alkali materials that build up as they
circulate which would otherwise contaminate product and damage the kiln
lining.  This practice necessarily reduces the overall volume of mercury
emitted by cement kilns, as noted by several commenters, since the
entrained mercury in the CKD is no longer available for release from the
kiln.  The amount of reduction is kiln-specific, based on the level of
alkali materials in the kiln’s raw materials and required product
specifications, and therefore not quantifiable on a national basis.  Nor
would kiln-by-kiln site-specific emission standards be warranted, for
the same reasons that site-specific limits based on mercury levels on
raw material and fuel inputs are not justified.  EPA is instead
determining that a floor standard for both existing and new sources is
the work practice that cement kiln dust be removed from the kiln system
at the point that recirculation causes adverse effect on product.

d. Standards Based on Performance of Wet Scrubbers

There are at least five cement kilns that have limestone (wet) scrubbers
installed (as it happens) for control of SO2.  Commenters noted that
based on experience with utility boilers, as well as on general
engineering principles, there is reason to expect that the scrubbers
installed on cement kilns also remove mercury.

To our knowledge, we obtained all the available data on wet scrubber
controlled facilities after the comment period on the proposed
amendments.  This consists of data from 2004 and 2005 tests at two
facilities measured exclusively at the scrubber outlet.  These data
range from 0.42 to 30 µg/dscm.  Variability of mercury emissions at the
scrubber-equipped kilns for which we have multiple test data differs by
orders of magnitude.  These data fall within the range of test data from
all kilns (those with wet scrubbers and those without wet scrubbers).
We have no test data for mercury measured at the scrubber inlet.  As a
result, we cannot, on the basis of the current data, determine with
absolute certainty (though we believe it is reasonably certain) if the
outlet mercury emissions from the wet scrubber equipped kilns are a
result of mercury removal by the scrubber, or simply reflect the amounts
of mercury in the raw materials. We now discuss the implications of this
information for purposes of existing and new source floors.  Note that
the following discussion assumes the scrubbers remove mercury for reason
discusssed below, though we cannot not say with certainty how much.

First, there are an insufficient number of wet-scubber

equipped kilns on which to base an existing source floor.  The
scrubber-equipped kilns would represent the best performing sources
since data from other kilns simply reflect the mercury levels in kiln
inputs on the day of the test. There are 158 operating kilns, and the
information available to us indicates that only five of them are
equipped with wet scrubbers.  The median kiln of the top 12 percent
would, therefore, not be a scrubber equipped kiln.

However, for new sources mercury emissions would not be uncontrolled -
solely dependent on raw material mercury content -- but rather would
reflect performance of “the best controlled similar source” (section
112 (d)(3)).  A kiln so-equipped would thus have the best performance
over time, since variability in mercury attributable to raw material and
fuel inputs would be controlled in part.

There is a reasonable basis for finding that wet scrubbers remove
mercury from cement kiln emissions.  Wet scrubbers are known to remove
mercury in most utility boiler applications, removal rates in that
industry being documented from between 0 to 72 per cent of incoming
mercury. See Control of Mercury Emissions from Coal-Fired Electric
Utility Boilers:  Interim Report Including Errata available at
www.epa.gov/nrmrl/pubs/600r01109/600r01109.htm.  We have speciated
mercury test data on two kilns that indicate that there is a significant
amount of oxidized mercury in at least some cement kilns.  Oxidized
mercury is the type of mercury known to be removed by wet scrubbers.
The limited data we have from cement kilns equipped with wet scrubbers
is among the lowest end-of-stack mercury data in our data base (although
not the lowest), which could indicate that some removal mechanism is
involved.  An important caveat, however, is that these data are
exclusively end-of-stack, without paired inlet concentrations.  These
data thus do not with absolute certainty indicate that mercury removal
is occurring.

We estimated the performance of the best performing scrubber, and hence
the new source MACT floor, as follows.  We are setting a new source
mercury emissions limit of 41 µg/dscm (corrected to 7 percent oxygen)
using the following rationale.  First, we limited the analysis to data
from wet scrubber equipped kilns because, as just discussed, the wet
scrubber equipped kilns represent the best performing sources,
regardless of their actual outlet emissions levels.  Second we ranked
all the wet scrubber mercury emissions with the raw mill off.  We
believe this is appropriate because the condition of raw mill off
represents a normal operating mode for a cement kiln (albeit the
operating mode when mercury emissions would be highest, as discussed
above in section a.i).  We then took the mean raw mill off value for
mercury emissions from a cement kiln in our (limited) data base, and
added to it a variability factor to account for normal variation in
emissions.  This variability factor is the the standard deviation of the
data multiplied by 2.326 to produce the 99th confidence interval.  We
looked to all of the data, rather than data from a single kiln, because
there are too few data points from any one kiln to estimate that
kiln’s variability.  Given that variability is known to occur, we
believe that this is the best approximation of variability of the best
performing kiln presently available.

  The result of this analysis is a new source floor of 41 µg/dscm that
must be met continuously (raw mill on and raw mill off).  This is an
emissions limit that we believe will not be exceeded 99 percent of the
time by the best performing kiln whose performance is used to set the
standard.

Because of the limited performance data characterizing performance of
the lowest-emitting scrubber-equipped kiln, the rule also contains an
alternative new source mercury floor.   The best performing kiln is
equipped with a wet scrubber, although there could be questions about
its performance over time.  Therefore, if a new source installs a
properly designed and operated wet scrubber, and is unable to achieve
the 41 ug/dscm standard, then whatever emission level the source
achieves (over time, considering all normal sources of variability)
would become the floor for that source.  Based on the design of the wet
scrubber that is the basis of the new source floor, this would be a
packed bed or spray tower wet scrubber with a minimum liquid-to-gas
ratio of 30 gallons per thousand cubic feet of exhaust gas.

	In sum, we conclude that floors for mercury for all existing cement
kilns should be to remove accumulated mercury-containing cement kiln
dust from the system at the point product quality is adversely affected.
 The floor for new sources is to utilize this same work practice, and in
addition, to meet a standard of either 41 µg/dscm or a site-specific
limit based on performance of a properly designed and operated wet
scrubber.

	 As just explained, the mercury data on which the new source floor is
based are not only limited, but fail to definitively answer the critical
question of whether wet scrubbers are removing mercury,and to what
extent.  We are taking immediate steps to address this issue and augment
the data base.  In an action published elsewhere in today’s Federal
Register, we are ourselves granting reconsideration of the new source
standard adopted in this rule, both due to substantive issues relating
to performance of wet scrubbers and because information about their
performance in this industry has not been available for public comment.
We also initiated actions to obtain inlet and outlet test data for
cement kilns equipped with wet scrubbers in order to determine if these
controls remove mercury, and to what extent.  In addition, we are
committing to completing this reconsideration process within one year
from [INSERT DATE OF PUBLICATION IN THE FEDERAL REGISTER].

2.  Beyond-the-Floor Determinations

During development of the original NESHAP for portland cement
manufacturing, we conducted MACT floor and beyond-the-floor analyses for
kiln and in-line kiln/raw mill mercury emissions (63 FR 14182, March 24,
1998 and 64 FR 31898, June 14, 1999).  We also conducted a
beyond-the-floor analysis for mercury, based on the performance of
activated carbon injection with an additional PM control device.  Costs
for the system would include the cost of the carbon injection system and
an additional FF to collect the carbon separately from the CKD.  Based
on the low levels of mercury emissions from individual portland cement
kilns, as well as the high cost per ton of mercury removed by the carbon
injection/FF system, we determined that this beyond-the-floor option was
not justified (63 FR 14202, March 24, 1998).

At proposal, EPA again concluded tentatively that a beyond the floor
standard based on performance of activated carbon is not justified (70
FR 72335).  We have since reevaluated beyond-the-floor control options
for mercury emissions.  This evaluation included both process changes
and add-on control technology.

	There are two potential feasible process changes that have the
potential to affect mercury emissions.  These are removing CKD from the
kiln system and, for the subcategory of kilns that currently use fly ash
as a raw material, replacing the fly ash with a lower mercury raw
material.  Substituting raw materials or fossil fuels with lower-mercury
inputs could in theory reduce mercury emissions, but this alternative is
infeasible for the reasons explained at 70 FR 72333-34.

	Generally, once mercury enters a kiln system, it has five potential
fates:  it may remain unchanged and become part of the final product; it
may react with raw materials and exit the kiln in the clinker; it may
vaporize in the high temperature of the kiln and/or preheater; it may
condense or react with the cement kiln dust and be removed from the
system; or it may exit the kiln system in vapor form or be adsorbed to a
dust particle through

the stack.  In general, mercury in the fuel becomes volatilized near the
kiln’s combustion zone and

is carried toward the feed end of the system along with combustion
gases. Some of the mercury compounds pass through the entire system and
exit in vapor phase through a stack. However, as the flue gas cools,
some mercury may adsorb/condense onto dust particles in the cooler
regions

of the kiln system. Much of this dust containing condensed mercury would
then be captured by the PM control device and for most kiln systems,
returned to the kiln.

We evaluated requiring a facility to further reduce the recycling of CKD
beyond the wastage already needed to protect product quality – the
floor for both existing and new sources.  For a 600,000 ton per year
(tpy) kiln the estimated total annual cost would be $3.7 million just
for replacement of CKD (which is actually product) and disposal of
additional solid waste.  This cost does not account for the increased
raw materials costs and energy costs associated with reducing the
recycling of the CKD.  The mercury emissions reduction would range from
0.012 to 0.055 tons per year based on assumed CKD mercury concentrations
of 0.33 and 1.53 ppm respectively.  The cost per ton of mercury
reduction would range from $67 million to $308 million.  See Costs and
Impacts of Wasting Cement Kiln Dust or Replacing Fly Ash to Reduce
Mercury Emissions in docket EPA-HQ-OAR-2002-0051.  We note that the
median value for the mercury content of recycled CKD for one study was
only 0.053 ppm.  See the report Mercury and Lead Content in Raw
Materials in docket EPA-HQ-OAR-2002-0051.  This would indicate that for
the majority of the facilities the costs per ton would be even higher
that those presented above.  In addition, we estimate that wasting 50
percent of the recycled CKD would reduce the energy efficiency of the
process by six percent due to the need to process and calcine additional
feed to replace the wasted CKD.  It is possible that in some cases the
wasted cement kiln dust could be mixed with the cement product rather
than landfilled, or that some other beneficial use could be found.  This
would reduce the costs and non-air adverse impacts of this option.
However, there are currently barriers to directly mixing CKD with
clinker due to product quality and product specification issues.  We do
not have data available to evaluate the potential for beneficial use of
the CKD.  Based on these costs, the adverse energy impacts, and the
increased adverse waste disposal impacts (see 64 FR 45632, 45635-36
(Aug. 20, 1999) for examples of potential hazards to human health and
the environment posed by disposal of cement kiln dust), we do not
believe this beyond-the-floor option is justified and therefore are not
selecting it.

As previously noted, for the subcategory of facilities that use utility
boiler fly ash as a kiln feed we determined that the current use
represented the MACT floor.  We considered two beyond-the-floor options
for this subcategory.  One option was to ban the use of any fly ash if
it resulted in a mercury emissions increase over a raw material
baseline, and the second was to only ban the use of fly ash whose
mercury content had been artificially increased through the use of a
sorbent to capture mercury in the utility boiler flue gas.

 If we were to ban the use of utility boiler fly ash for any case where
it has been shown to increase mercury emissions from the kiln over a raw
material baseline, facilities would have to revert to using their
previous raw materials, or to find alternative raw materials that
provide the same elements as the fly ash.  As previously noted, if a
facility replaces their shale or clay with fly ash, the quarry for that
material may now be closed and it may not be possible to obtain the
previously used raw materials.  And for at least two new facilities, the
original raw materials used at startup will include fly ash, so there is
no previously used material with which to compare the mercury content of
the fly ash.  Due to the site specific costs associated with raw
materials, we don’t have any data to calculate the costs of the
beyond-the-floor option for the industry as a whole.  In one example, we
estimated the cost as approximately $136 million per ton of mercury
reduction. See Costs and Impacts of Wasting Cement Kiln Dust or
Replacing Fly Ash to Reduce Mercury Emissions in docket
EPA-HQ-OAR-2002-0051.   Also, this option would mean that all the fly
ash currently being used as a cement kiln feed would now potentially
have to be landfilled.  This would generate an additional 3 million tons
per year of solid waste.  There would also be adverse environmental air
and nonair environmental impacts associated with the additional raw
materials that would have to be mined.  In addition, the overall kiln
efficiencies (i.e. the amount of fuel required per ton of clinker
produced) at the facilities using fly ash would be expected to decrease
if the fly ash were replaced with shale or clay.  This decrease may be
as large as 10 percent (See Site Visit to Lafarge Cement in Alpena
Michigan in the docket).

Based on the cost, energy, and adverse nonair environmental impacts, we
believe that banning the current use of utility boiler fly ash is not
justified.

We also separately evaluated the use of fly ash from a utility boiler
where activated carbon, or some other type of sorbent injection, has
been used to collect mercury.  This practice does not currently occur,
but it could.  See 70 FR 72344 (voicing concern about potential for
increased mercury emissions from cement kilns were such fly ash to be
used).  The mercury concentration in this type of fly ash will vary
widely. However, full scale testing of fly ash from of utility boilers
using various sorbent injection processes has indicated there is a
potential for sorbent injection to significantly increase fly ash
mercury content (Characterization of Mercury-Enriched Coal Combustion
Residues form Electric Utilities Using Enhanced Sorbents for Mercury
Control in the docket).  Testing to date has shown increases of a factor
of 2 to 10, and in one case of a very low mercury fly ash the increase
was a factor of 70.

Data from 16 cement facilities currently using fly ash not reflecting
sorbed mercury showed mercury concentrations in the fly ash ranged from
0.002 ppm to 0.685 ppm with a median of 0.136 ppm.  Data on the fly ash
mercury content of currently operating utility boilers testing sorbent
injection showed levels ranging from 0.071 ppm up to 1.529 ppm with a
median level of 1.156 ppm, significantly higher than the fly ash
currently in use.  Therefore, we see a potential for fly ash with
enhanced mercury content due to sorbent injection to increase mercury
emissions from cement kilns, and for the increase to be much more
significant than emissions attributable to the current fly ash being
used.

We do not see a ban on the use of this type of fly ash as significantly
affecting the overall current beneficial uses of fly ash.  First, we do
not anticipate the widespread use of ACI in the utility industry until
2010 or later.  Therefore, both the cement industry and the utility
industry will have a significant amount of time to adjust to this
requirement.  Second, a utility boiler that decides to apply ACI for
mercury control has the option of collecting the fly ash from sorbent
injection systems separately from the rest of the facility’s fly ash.
Therefore, the utility boiler could continue to supply non-sorbent fly
ash to a cement kiln even after the application of ACI for mercury
control.  Finally, technology is being developed that would allow the
mineral-rich portion of fly ash to be separated from the high
carbon/high mercury portion.

Based on these factors, we are banning the use of utility boiler fly ash
in cement kilns where the fly ash mercury content has been increased
through the use of activated carbon or any other sorbent unless the
facility can demonstrate that the use of that fly ash will not result in
an increase in mercury emissions over baseline emissions (i.e. emissions
not using the mercury increased fly ash).  This requirement, adopted as
a beyond-the-floor control, applies to both existing and new sources.

We also reevaluated our analysis of potential control options based on
add-on control technology.  These were control options based on the use
of a limestone scrubber, and activated carbon injection.

As previously noted there are at least five cement kilns that have
limestone (wet) scrubbers.  As discussed in section IV.A.1.d above,
there is a reasonable basis for beleiving that the wet scrubbers remove
mercury.  There are no data available to allow us to definitively
estimate the percent reduction expected.  We performed a cost analysis
based on an assumed mercury removal efficiency of 42 percent, which is
transferred (solely for purposes of analysis) from performance of wet
scrubbers in the utility boiler category and represents the greatest
degree of removal one would expect to be consistently achieved for
portland cement kilns.  We also note that the wet scrubber will achieve
cobenefits of reducing SO2 and dioxins (although dioxin removal would be
relatively modest since any removal would be incremental to that
required by the existing MACT dioxin standard for portland cement
kilns).  The results of that analysis for an existing model large kiln
are as follows.

Table 1. Packed Bed Scrubber – Costs and Emission Reductions

Clinker Production

(tpy)	Total Annualized Cost

($/yr)	Emissions Reduction

SO2

(tpy)	D/F

(g/yr)	Hg

(lb/yr)

600,000	1,542,000	297	0.11	16.8 - 147

Based on this analysis the cost per ton of mercury removed ranges from
$21 million per ton to $184 million per ton, not at all cost effective.
In addition, a wet scrubber for a large kiln will generate approximately
50,000 tons per year of solid waste and require approximately 980,000
kWhr/year of electricity.

Based on the significant cost impacts per ton of emission reduction, and
the adverse energy and solid waste impacts, and the uncertainty of the
actual mercury emission reductions, we do not consider this control
option to be reasonable for existing sources.

	At proposal, EPA discussed and rejected a beyond-the- floor option
based on the use of activated carbon injection.  See 70 FR 72335.
Commenters noted that our costs for ACI had not been updated from the
costs calculated in development of the original NESHAP.  In response, we
have now updated our ACI costs based on more recent information.  The
total annualized costs for a large new or existing kiln ranges from
$510,000 to $676,000 per year.  Assuming an 80 percent reduction in
mercury emissions, the cost per ton of mercury removal ranged from $4
million to $42 million per ton for existing kilns.  The wide range in
cost per ton of removal is mainly influenced by the baseline mercury
emissions.  Based on the wide variation we have seen in actual mercury
emissions in this source category, the actual practice cost per ton
would also vary widely from site to site as shown above.

We also evaluated a beyond-the-floor option for new kilns based on
combining ACI and a wet scrubber.  The incremental cost of ACI in this
application is $9 to $89 million per ton of mercury removed, which we
regard as a very high cost.

Our cost estimates assumed 80 percent emissions reduction for mercury.
Though we are reasonably certain that ACI will remove mercury from
cement kiln exhaust gas, we have no data on the actual expected removal
efficiency.  Data are available for one emissions test on a cement kiln
burning hazardous waste.  In this test the mercury removal efficiency
averaged 89 percent removal.  However, the inlet mercury concentration
during the test varied from 65 to 267 µg/dscm.  A review of the data
for the individual test runs implies that the percent reduction
decreases as the inlet concentration decreases.  Almost all the NHW
cement kilns tested had mercury concentrations well below 65 µg/dscm.
Therefore, the long term performance of ACI on mercury emission is very
uncertain.  We also note that the application of ACI to a cement kiln
(either alone or in combination with a wet scrubber) will generate
approximately 1,600 tons per year of solid waste for a new or existing
large kiln.

	For existing sources we rejected a control option based on the
performance of ACI due to the significant cost per ton of mercury
removed, increased energy use, and the nonair environmental impacts.
For new sources we rejected the option based on the performance of ACI
combined with a wet scrubber due to the significant cost per ton of
mercury removed, increased energy use and the nonair environmental
impacts.  For new and existing sources we rejected this control option
due to the uncertainty of the actual performance levels achieved, which
leads to uncertainty of the actual cost per ton of mercury emissions
reduction.  We also note that the application of ACI potentially could
also result in a THC emission reduction of up to 117 tpy per kiln,
though in most cases the reduction would be approximately 30 tpy or
less.  This THC emissions reduction is based on an assumed control
efficiency of 50 percent.  We do not see these small THC emission
reductions (of which organic HAP are a small subset) to be a reason to
reconsider our decision that ACI is not justified as a beyond-the-floor
control option.

Finally, for greenfield new sources (sources being newly built at a site
without other cement kilns), we considered the option of requiring such
a kiln to be sited at a low-mercury quarry.  This concept has intuitive
appeal: such a new kiln is not tied to an existing source of limestone,
and so can choose where to be sited. The difficulty is in quantifying
this type of standard.  We cannot presently quantify what ‘high
mercury quarry’ or ‘low mercury quarry’ means, and cannot
responsibly select an arbitrary number that might make it impossible to
build a new cement kiln in major parts of the country.

3.  Conclusion

In sum, we conclude that the standards for mercury for all existing
cement kilns are to remove accumulated mercury-containing cement kiln
dust from the system at the point product quality is adversely affected.
 The standard for new sources is to utilize this same work practice, and
in addition, to meet a standard of either 41 µg/dscm or a site-specific
limit based on performance of a properly designed and operated wet
scrubber.

For purposes of the new source standard, a new source is any source
constructed or reconstructed after December 2, 2005, the date of
proposal for the amendments.  See the response to comment concerning new
sources in section VI for our rationale for use of the December 2005
proposal date.

	We are also using the discretion granted under section 112(i)(1) to
grant new sources three years from [INSERT THE DATE OF PUBLICATION OF
THE FINAL AMENDMENTS IN THE FEDERAL REGISTER] or startup, whichever is
later, to comply with the new source standards.  We have this discretion
whenever we promulgate a final standard that is more stringent than the
proposed standard, which is the case here.

We are also requiring that new sources demonstrate compliance by doing
mercury emission testing with the raw mill off and with the raw mill on.
 The reason to test under both conditions is that one other operation
factor affecting emissions is the recycling of CKD.  A facility could
cut off CKD recycling for purposes of meeting the emission limit during
testing with raw mill off, and then turn recycling back on after the
test which could result in the emissions limit being exceeded.  We could
simply limit CKD recycling to the level during the raw mill off test,
but we believe this would potentially and needlessly restrict the
ability of a facility to recycle CKD during raw mill on operation.
During the test under each condition, the facility must record the
amount of CKD recycle.  The amount of CKD recycle becomes an operating
limit not to be exceeded.

B.  Determination of MACT for HCl Emissions

	In developing the 1999 Portland Cement NESHAP we concluded that no
add-on air pollution controls were being used whose performance could be
used as a basis for the MACT floor for existing portland cement plants.
For new source MACT, we identified two kilns that were using alkaline
scrubbers for the control of sulfur dioxide (SO2) emissions.  But we
concluded that because these devices were operated only intermittently,
their performance could not be used as a basis for the MACT floor for
new sources.  Alkaline scrubbers were then considered for
beyond-the-floor controls.  Using engineering assessments from similar
technology operated on municipal waste combustors and medical waste
incinerators, we estimated costs and emissions reductions.  Based on the
costs of control and emissions reductions that would be achieved, we
determined that beyond-the-floor controls were not warranted (63 FR
14203, March 24, 1998).

	In the proposed amendments, we reexamined establishing a floor for
control of HCl emissions from new portland cement sources.  Since
promulgation of the NESHAP, wet scrubbers have been installed and are
operating at a minimum of five portland cement plants.  See section
IV.A.1.d above.  Based on the presence of continuously operated alkaline
scrubbers at portland cement plants, we proposed that the performance of
continuously operated alkaline scrubbers represents MACT for new
sources, and set proposed emissions levels of 15 ppmv at the control
device outlet, or a 90 percent HCl emissions reduction measured across
the scrubber.

	 We also reexamined the MACT floor for existing sources. The only
potential controls identified as a floor option was the operation of the
kiln and PM control device themselves.  Because the kiln and PM control
system contain large amounts of alkaline CKD, the kilns themselves
remove a significant amount of HCl (which reacts with the CKD and is
captured as particulate).  See 70 FR 72337 and 69 FR 21259 (April 20,
2004).  We proposed the operation of the kiln and PM control as a work
practice standard.

	We also evaluated requiring the use of an alkaline scrubber as a
beyond-the-floor control option for existing sources.  We did not
consider the costs and nonair environmental impacts reasonable for the
emissions reductions achieved.

We also solicited comment on adopting alternative risk-based emission
standards for HCl pursuant to section 112(d)(4) of the CAA (70 FR
72337).  We suggested two possible approaches for establishing such
standards.  Under the first approach an alternative risk-based standard
would be based on national exposure standards determined by EPA to
ensure protection of public health with an ample margin of safety and
that do not pose adverse environmental impacts.  For reasons discussed
below we have decided to adopt this approach.  Under the second
approach, which we are not adopting, site specific risk analyses would
be used to establish standards on a case-by case basis.

After careful consideration of the comments on the proposed amendments,
we are not regulating HCl emissions from cement kilns.   Under the
authority of section 112(d)(4) of the CAA, we have determined that no
further control is necessary because HCl is a “health threshold
pollutant,” and current HCl levels emitted from cement kilns would
provide “an ample margin of safety”, in protecting human health and
the environment.  The following explains the statutory basis for
considering health thresholds when establishing standards and the basis
for today’s decision, including a discussion of the risk assessment
conducted to support the ample margin of safety decision.

Section 112 of the CAA includes exceptions to the general statutory
requirement to establish emission standards based on MACT.  Of relevance
here, section 112(d)(4) allows us to develop risk-based standards for
HAP “for which a health threshold has been established” provided
that the standards achieve an “ample margin of safety.” Therefore,
we believe we have the discretion under section 112(d)(4) to develop
standards which may be less stringent than the corresponding
technology-based MACT standards for some categories emitting threshold
pollutants. See 67 FR 78054, December 20, 2002 and 63 FR 18765, April
15, 1998.

In evaluating potential standards for HCl for this source category, we
seek to assure that emissions from every source in the category result
in exposures not causing adverse effects, with an ample margin of
safety, even for an individual exposed at the upper end of the exposure
distribution.  The upper end of the exposure distribution is calculated
using the “high end exposure estimate,” defined as a plausible
estimate of individual exposure for those persons at the upper end of
the exposure distribution, conceptually above the 90th percentile, but
not higher than the individual in the population who has the highest
exposure.  We believe that assuring protection to persons at the upper
end of the exposure distribution is consistent with the “ample margin
of safety” requirement in section 112(d)(4).

Our decision not to develop standards for HCl from cement kilns is based
on the following.  First, we consider HCl to be a threshold pollutant.
See 63 FR 18767, 67 FR 78054, and 70 FR 59407, October 12, 2005.
Second, we have defined threshold values for HCl in the form of an
Inhalation Reference Concentration (RfC) and acute exposure guideline
level (AEGL).  Third, HCl is emitted from cement kilns in quantities
that result in human exposure in the ambient air at levels well below
these threshold values with an ample margin of safety.  Finally, there
are no adverse environmental effects associated with HCl emissions form
cement kilns.  The bases and supporting rationale for these conclusions
are as follows.

For the purposes of section 112(d)(4), several factors are considered in
our decision on whether a pollutant should be categorized as a health
threshold pollutant.  These factors include evidence and classification
of carcinogenic risk and evidence of noncarcinogenic effects.  For a
detailed discussion of factors that we consider in deciding whether a
pollutant should be categorized as a health threshold pollutant, please
see the April 15, 1998 Federal Register document (63 FR 18766).  In the
April 15, 1998 action cited above, we determined that HCl, a Group D
pollutant, is a health threshold pollutant for the purpose of section
112(d)(4) of the CAA (63 FR 18753).

The Portland Cement Association (PCA) conducted a risk assessment to
determine whether the emissions of HCl from cement kilns at the current
baseline levels resulted in exposures below the threshold values for
HCl.  We reviewed the risk assessment report prepared by the PCA and
believe that it uses a reasonable and conservative methodology, is
consistent with EPA methodology and practice, and reaches a reasonable
conclusion that current levels of HCl emissions from cement kilns would
be well under the threshold level of concern even for assumed worst-case
human receptors.

The PCA analysis evaluated long-term and short-term ambient air
concentrations resulting from emissions of hydrochloric acid (HCl) from
portland cement kilns in order to quantify potential non-cancer risks
associated with such emissions, as well as to characterize potential
ecological effects of those emissions. The approach is based on the
USEPA guidance document entitled “A Tiered Modeling Approach for
Assessing the Risks Due to Sources of Hazardous Air Pollutants” (USEPA
1992) (Tiered Modeling Approach)and is consistent with EPA risk
characterization guidance “Air Toxics Risk Assessment Reference
Library -Volume 2 - Facility-Specific Assessment” (USEPA, 2004).  The
PCA conducted dispersion modeling for 67 cement plants and 112 cement
kilns, representing about two-thirds of all operating cement plants in
the U.S., using stack parameter data provided by cement companies and
conservative assumptions regarding (among other factors) HCl stack
concentrations, operating conditions, receptor locations, and dispersion
characteristics.  The kilns for which data were provided cover a full
range of kiln types, operating conditions, and stack parameters. The
three-tiered modeling approach consists of:

• Tier 1 – Lookup tables

• Tier 2 – Screening dispersion modeling

• Tier 3 – Detailed dispersion modeling

The concentration estimates from each modeling tier should be more
accurate and less conservative than the previous one. As a result, the
level of complexity of the modeling and data input information required
for each tier is greater than for the previous tier.  If a plant showed
emissions below the threshold concentration in any tier, that plant was
not included in the next tier of modeling.

In order to evaluate potential health impacts it is necessary to
establish long and short term concentration threshold.  The 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 significant noncancer health effects in humans.  We have
determined that the RfC for HCl of 20 micrograms per cubic meter
(µg/m3) is an appropriate threshold value for assessing risk to humans
associated with exposure to HCl through inhalation (63 FR 18766, April
15, 1998).  Therefore, the PCA used this RfC as the threshold value in
their exposure assessment for HCl emitted from cement kilns.  To
evaluate potential short term health impacts the CalEPA REL of 2,100
µg/m3 was used as the AEGL.

The general approach was that actual release characteristics were used
for stack height, stack diameter, exit temperature, and exit velocity,
based on information provided by the individual facilities modeled to
the PCA.  The analyses performed under each tier assumed worst case
operating scenarios, such as maximum production rate and 24 hours per
day, 365 days per year operation, and that all kilns were located 10
meters from the property boundary line.  Hydrogen chloride emission
rates were assumed to be 130 ppmv for all kiln types.  This is an
extremely conservative number.  Hydrogen chloride emission rates are
below 10 ppmv at most facilities, and the highest value for which we
have data is below 45 ppmv.  In the Tier 2 analyses, worse case
metrological conditions were assumed.  Further, it is important to note
that these predicted impacts are located adjacent to facility property
lines, many times in locations where chronic exposure is not expected.
Impacts at potential residential locations would be expected to be
significantly below those presented in the analysis.

The PCA study generated estimates of both chronic (annual average) and
acute (one hour) concentrations for comparison to the relevant health
reference values or threshold levels.  Acute and chronic exposures were
compared to the CalEPA REL value of 2,100 µg/m3 for one-hour exposures
and the RfC of 20 µg/m3 for long-term continuous exposure,
respectively.

Noncancer risk assessments typically use a metric called the Hazard
Quotient (HQ) to assess risks of exposures to noncarcinogens.  The HQ is
the ratio of exposure (or modeled concentration) to the health reference
value or threshold level (i.e., RfC or REL).  HQ values less than 1
indicate that exposures are below the health reference value or
threshold level and are likely to be without appreciable risk of adverse
effects in the exposed population.  HQ values above 1 do not necessarily
imply that adverse effects will occur, but that the potential for risk
of such effects increases as HQ values exceed 1.

At this point, it should be noted that the potential for effects depends
on an individual’s total exposure to that chemical.  As a result,
exposure from all sources, not just the one in question, must be
evaluated.  To take background concentrations of HCl into consideration,
data were obtained from the EPA AirData data base
(http://www.epa.gov/air/data/index.html) for data collected in all
states for any year between 1957 and 2006.

Based on these data, a conservative estimate of the average background
concentration of HCl was assumed to be 5.774 μg/m3, the highest average
concentration at any location, which was used to evaluate long term
background conditions.  This value would equate to a HQ of 0.29.  The
maximum concentration detected, 23.7 μg/m3, was used as an estimate of
the maximum short term background concentration.  This would equate to
an  short term hazard quotient (HQst) of 0.01.

For the PCA assessment, if the HQ was found to be less than 0.71 (a
total of 1 including background) for any of the tiers using conservative
defaults and modeling assumptions, the analysis concluded with that
tier.  On the other hand, if the HQ exceeded 0.71, analysis proceeded to
subsequent tiers.  For the short term analysis, if the HQst was 0.99 or
less (a total of 1 including background), the analysis concluded with
that tier.

The tier 1 modeling resulted in an HQ above 0.71 for all facilities and
an HQst above 0.99 for most facilities.  Therefore, a Tier 2 analysis
was required.  In the Tier 2 analysis, all facilities except for eight
showed an HQ below 0.71, an HQst below 0.99.

For the eight facilities with an HQ above 0.71, additional data were
obtained on the actual HCl and stack moisture concentrations at these
facilities and the Tier 2 modeling analysis was rerun.  The refined Tier
2 analysis resulted in HQ values of 0.30 or less for all eight
facilities.

Thus, we have evaluated and are comfortable with PCA’s calculations
and feel confident that exposures to HCl emissions from the facilities
in question are unlikely to ever exceed an HQ or HQst of 1.0 considering
background concentrations.  Therefore, we believe that the predicted
exposures from these facilities should provide an ample margin of safety
to ensure that total exposures for nearby residents should not exceed
the short-term or long-term health based threshold levels or health
reference values, even when considering the possible contributions of
other sources of HCl.

The standards for emissions must also protect against significant and
widespread adverse environmental effects to wildlife, aquatic life, and
other natural resources.  The PCA did not conduct a formal ecological
risk assessment.  However, we have reviewed publications in the
literature to determine if there would be reasonable expectation for
serious or widespread adverse effects to natural resources.

We consider the following aspects of pollutant exposure and effects:
toxicity effects from acute and chronic exposures to expected
concentrations around the source (as measured or modeled), persistence
in the environment, local and long-range transport, and tendency for
biomagnification with toxic effects manifest at higher trophic levels.

No research has been identified for effects on terrestrial animal
species beyond that cited in the development of the HCl RfC.  Modeling
calculations indicate that there is little likelihood of chronic or
widespread exposure to HCl at concentrations above the threshold around
cement manufacturing plants.  Based on these considerations, we believe
that the RfC can reasonably be expected to protect against widespread
adverse effects in other animal species as well.

Plants also respond to airborne HCl levels.  Chronic exposure to about
600 µg/m3 can be expected to result in discernible effects, depending
on the plant species.  Plants respond differently to HCl as an anhydrous
gas than to HCl aerosols.  Relative humidity is important in plant
response; there appears to be a threshold of relative humidity above
which plants will incur twice as much damage at a given dose.  Effects
include leaf injury and decrease in chlorophyll levels in various
species given acute, 20minute exposures of 6,500 to 27,000 µg/ m3.  A
field study reports different sensitivity to damage of foliage in 50
species growing in the vicinity of an anhydrous aluminum chloride
manufacturer.  American elm, bur oak, eastern white pine, basswood, red
ash and several bean species were observed to be most sensitive.
Concentrations of HCl in the air were not reported.  Chloride ion in
whole leaves was 0.2 to 0.5 percent of dry weight; sensitive species
showed damage at the lower value, but tolerant species displayed no
injury at the higher value.  Injury declined with distance from the
source with no effects observed beyond 300 meters.  The maximum modeled
long-term HCl concentration (less than 100 µg/m3) is well below the 600
µg/m3 chronic threshold, and the maximum short-term HCl concentration
(less than 1600 µg/m3) is well below the 6,500 µg/m3 acute exposure
threshold.  Therefore, no adverse exposure effects are anticipated.

Prevailing meteorology strongly determines the fate of HCl in the
atmosphere.  However, HCl is not considered a strongly persistent
pollutant or one where long range transport is important in predicting
its ecological effects.  In the atmosphere, HCl can be expected to be
absorbed into aqueous aerosols, due to its great affinity for water, and
removed from the troposphere by rainfall.  In addition, HCl will react
with hydroxy ions to yield water plus chloride ions.  However, the
concentration of hydroxy ions in the troposphere is low, so HCl may have
a relatively long residence time in areas of low humidity.  No studies
are reported of HCl levels in ponds or other small water bodies or soils
near major sources of HCl emissions.  Toxic effects of HCl to aquatic
organisms would likely be due to the hydronium ion, or acidity.  Aquatic
organisms in their natural environments often exhibit a broad range of
pH tolerance.  Effects of HCl deposition to small water bodies and to
soils will primarily depend on the extent of neutralizing by carbonates
or other buffering compounds.  Chloride ions are essentially ubiquitous
in natural waters and soils so minor increases due to deposition of
dissolved HCl will have much less effect than the deposited hydronium
ions.  Deleterious effects of HCl on ponds and soils, where such effects
might be found near a major source emitting to the atmosphere, likely
will be local rather than widespread, as observed in plant foliage.

Effects of HCl on tissues are generally restricted to those immediately
affected and are essentially acidic effects.  The rapid solubility of
HCl in aqueous media releases hydronium ions, which can be corrosive to
tissue when above a threshold concentration.  The chloride ions may be
concentrated in some plant tissues, but may be distributed throughout
the organism, as most organisms have chloride ions in their fluids.
Leaves or other tissues exposed to HCl may show some concentration above
that of their immediate environment; that is, some degree of
bioconcentration can occur.  However, long-term storage in specific
organs and biomagnification of concentrations of HCl in trophic levels
of a food chain would not be expected.  Thus, the chemical nature of HCl
results in deleterious effects, that when present, are local rather than
widespread.

In conclusion, acute and chronic exposures to expected HCl
concentrations around cement kilns are not expected to result in adverse
toxicity effects.  Hydrogen chloride is not persistent in the
environment.  Effects of HCl on ponds and soils are likely to be local
rather than widespread.  Finally, HCl is not believed to result in
biomagnification or bioaccumulation in the environment.  Therefore, we
do not anticipate any adverse ecological effects from HCl.

The results of the exposure assessment showed that exposure levels to
baseline HCl emissions from cement production facilities are well below
the health threshold value.  Additionally, the threshold values, for
which the RfC and AEGL values were determined to be appropriate values,
were not exceeded when considering conservative estimates of exposure
resulting from cement kiln emissions as well as considering background
exposures to HCl and therefore, represent an ample margin of safety.
Furthermore, no significant or widespread adverse environmental effects
from HCl are anticipated.  Therefore, under authority of section
112(d)(4), we have determined that further control of HCl emissions from
new or existing cement manufacturing plants under section 112(d) is not
necessary.

C.  Determination of MACT for THC Emissions

	1.  Floor Determinations

	Total hydrocarbons (THC) serve as a surrogate for non-dioxin organic
HAP emissions for this source category.  During the development of the
1999 Portland Cement NESHAP, EPA identified no add-on air pollution
control technology being used in the portland cement industry whose
performance could be used as a basis for establishing a MACT floor for
controlling THC emissions from existing sources.  The EPA did identify
two kilns using a system consisting of a precalciner (with no
preheater), which essentially acts as an afterburner to combust organic
material in the feed.  The precalciner/no preheater system was
considered a possible basis for a beyond-the-floor standard for existing
kilns and as a possible basis for a MACT floor for new kilns.  However,
this system was found to increase fuel consumption relative to a
preheater/precalciner design, to emit six times as much SO2, two and one
half times as much oxides of nitrogen (NOx), and 1.2 times as much
carbon dioxide (CO2) as a preheater/precalciner kiln of equivalent
clinker capacity.  Taking into account the adverse energy and
environmental impacts, we determined that the precalciner/no preheater
design did not represent MACT (63 FR 14202, March 24, 1998).  We also
considered feed material selection for existing sources as a MACT floor
technology and concluded that this option is not available to existing
kilns, or to new kilns located at existing plants because these
facilities generally rely on existing raw material sources located close
to the source due to the cost of transporting the required large
quantities of feed materials.  However, for new greenfield kilns, feed
material selection as achieved through appropriate site selection and
feed material blending is demonstrated and is the basis for new source
MACT (63 FR 14202, March 24, 1998).

	In our proposed amendments we reexamined MACT for THC for both new and
existing facilities.  We proposed to transfer the standards for cement
kilns that fire hazardous waste (40 CFR 63.1220(a)(5)) in the Portland
Cement NESHAP.  Our rationale for transferring these standards was that
the THC and CO standards guarantee that the kiln will operate under good
combustion conditions and will minimize formation (and hence, emissions)
of non-dioxin organic HAP.  We believed that the control of THC
emissions from cement kilns which do not fire hazardous waste should be
no more difficult to control than emissions for kilns that do fire
hazardous waste because good combustion practices are maintainable by
either type of kiln, and the hazardous waste cement kilns would be the
more challenged in that regard.  Because we had no data upon which to
set a different standard, and because we believed these levels were
indicative of good combustion in any case, the tranbsfer of the
standards for cement kilns firing hazardous waste seemed appropriate.

We continue to believe that good combustion conditions are indicative of
the performance of the median of the best performing 12 percent of
existing sources for controlling non-dioxin organic HAP.  However, based
on comments received on the proposed amendments, and additional emission
data analysis, we believe our proposed quantified method of monitoring
good combustion, i.e. setting specific THC or CO levels, was flawed.

Industry commenters had noted that the majority of the THC emissions
from a cement kiln main stack result from the introduction of feed
materials into the cold end of the kiln.  These emissions are
essentially a function of the organic content of the raw materials, and
cannot be controlled using good combustion practices, which is the basis
of our MACT floor.  At proposal we agreed with this assessment (and
continue to agree with it), but believed that the fact that cement kilns
that burn hazardous waste can meet these standards indicated that the
proposed level could be met by all cement kilns under good combustion
conditions, even considering the fact that good combustion cannot
control THC or CO emissions emanating from organic materials in the
feed.  We also believed that by allowing a facility to monitor CO as a
surrogate for THC, we had provided sufficient flexibility to account for
variations in feed material organic content.

We have reevaluated these assumptions.  First, we obtained additional
THC emission data from several facilities.  These data demonstrate that
there are certain cement facilities where THC emissions, with no
indication of poor combustion practices, exceed 20 ppmv.  The data also
indicate that achieving the 100 ppmv CO level, even for cement kilns
with low organic content feed and good combustion conditions, is not
possible without use of a control device.  See Lehigh CO and THC data in
docket EPA-HQ-OAR-2002-0051.  Moreover, the analogy with hazardous
waste-burning cement kilns breaks down.  If a cement kiln that fires
hazardous waste cannot meet the THC or CO limits in the HWC NESHAP due
to organic materials in their feed, they can (and have) simply stopped
firing hazardous waste. This can either be done permanently, or
temporarily anytime the kiln operator notes that THC or CO emissions are
approaching the emission limits.  This option is not available to cement
kilns that do not fire hazardous waste; they cannot stop making cement
without ceasing business altogether.  This would mean that facilities
with higher levels of organic materials in the raw materials would be
forced to adopt some type of add-on control to meet the emissions
limits.  As we have previously stated, we believe this would result in
the imposition of a beyond-the-floor standard without the mandated
consideration of costs and other impacts.  See 70 FR 72335.

As a result, although we adhere to our approach at proposal that the
MACT floor for control of non-dioxin organic HAP at existing sources is
operating under good combustion conditions, we are adopting a different
means of demonstrating that good combustion conditions exist.

In the final amendments, we are requiring that existing kilns and
in-line kilns/raw mills must implement good combustion practices (GCP)
designed to minimize THC from fuel combustion.  Good combustion
practices include training all operators and supervisors to operate and
maintain the kiln, calciner, and pollution control systems in accordance
with good engineering practices. The training shall include both good
operating practices as well as operating the kiln, claciner, and
pollution control system in a manner to minimize excess emissions.

We have also reexamined the proposed MACT floor for new sources.  There
are currently two cement kilns with add-on controls which reduce
emissions of THC.  At one facility, activated carbon is injected into
the flue gas and collected in the PM control device.  The carbon adsorbs
some of the THC.  The collected carbon is then reinjected into the kiln
in a location that insures destruction of the collected THC.  However,
the THC emissions from this facility are the highest for any facility
for which we have data. Therefore, we do not consider this to represent
the best controlled source.  This same facility also has an alternative
control scheme for THC of a limestone scrubber followed by a
regenerative thermal oxidizer (RTO).  However, these control devices
have not operated continuously due to significant operation problems
caused by the site specific constituents in the flue gas. (See email
from Michael D. Maillard, Michigan Department of Environmental Quality
in docket EPA-HQ-OAQ-2002-0051.)  Because these controls have not been
demonstrated to have the ability to operate continuously, we cannot
consider them as the basis for a new source MACT floor (or an emission
standard, for that matter).

A second facility also has a limestone scrubber followed by an RTO.  In
this case the scrubber/RTO operates continuously and efficiently.  This
facility has been tested and showed VOC (essentially the same as THC)
emission levels of 4 ppmv (at 7 percent oxygen), and currently has a
permit limit for VOC of approximately 9 ppmv.  The RTO has a guaranteed
destruction efficiency of 98 percent of the combined emissions of CO and
THC. Based on this information we believe this facility is the best
controlled source, and that the performance of a limestone scrubber
followed by a RTO is the basis for new source MACT floor for non-dioxin
organic HAP, measured as THC. We explain below how we assess the
long-term performance capabilities of this control device considering
variable organic levels in raw materials and other process
variabilities.

We are retaining the proposed THC emission limit of 20 ppmv measured at
the main kiln stack as the MACT floor for all new or reconstructed kilns
and inline raw mill/kilns.  An alternative to the 20 ppmv floor level is
a facility may demonstrate a 98 percent reduction in THC emissions from
uncontrolled levels -- the level of emission reduction required by
permit for the best performing source in the category.  We have
determined that a 20 ppmv outlet emissions level and 98 percent
destruction efficiency represent the long term performance of an RTO
under the varying conditions typically encountered in industrial
applications.  See Thermal Incinerators and Flares in Docket
EPA-HQ-OAR-2002-0051.  As noted above, the one cement facility with an
RTO operating full-time has actual and permitted emission levels which
are below 20 ppmv.  However, the performance guarantee at this facility
is based on the combined emissions of CO and THC.  Therefore, all new
facilities could meet the permitted emission levels of the one facility
that has an RTO only if they all have the same levels of CO in the
exhaust gas.  We have no data to support that all new kilns will have
sufficient CO in the exhaust streams to guarantee that they can meet the
same level of performance as the one facility noted above.  The percent
reduction acheivable by an RTO is dependent on the inlet concentration
of organics.  See Thermal Incinerators and Flares in Docket
EPA-HQ-OAR-2002-0051.  Thus, we believe that a limit based on the
demonstrated performance of RTOs under a variety of circumstances is the
best measure of the long term performance of this device under the
circumstances likely to be encountered by new cement kilns, especially
varying levels of organics in the feed.

The original Portland Cement NESHAP contains a 50 ppmv THC emissions
limit for new greenfield kilns, kilns/inline raw mills, and raw
materials dryers.  There are no situations we can identify where a 50
ppmv limit would be more stringent than a 98 percent reduction limit.
Since this limit is less stringent than the floor based on performance
of an RTO, it is obviously not appropriate to retain it.  We are thus
finding that the floor for greenfield new sources (and all other new
sources) is 20 ppm/98% THC with one exception.  This new source limit
will, at least for some new facilities, require the application of a
back end control.  For this reason, we do not believe this limit should
be applied retroactively to new sources constructed prior to December 2,
2006, the date of proposal for the amendments.  See the response to
comment concerning new sources in section VI for our rationale for this
decision.  So for new sources constructed prior to December 2, 2006 we
are retaining the 50 ppmv THC limit.

2.  Beyond-the-floor Determinations

	We previously considered beyond-the-floor options for existing sources
of substituting raw materials with lower organic contents, but we
determined this beyond-the-floor option was not feasible (70 FR 72340).
We also considered a beyond-the-floor THC standard of 20 ppmv based on
the use of the scrubber/RTO control system.  Based on the available
data, we estimate that approximately 75 percent of existing kilns could
meet a 20 ppmv standard without the addition of controls.  For an
existing preheater/precalciner kiln that could not meet a 20 ppmv
standard without controls the capital cost would be approximately $10.7
million and the total annualized cost would be approximately $3.9
million.  The cost per ton of THC reduction would be in the area of
$20,000, assuming an inlet concentration of about 63 ppmv.  We estimate
that approximately 5 percent of the THC is actually organic HAP.
Therefore, the cost of organic HAP reduction would be $398,000 per ton.
In addition, the energy use for one large kiln to operate an RTO would
be approximately 99.7 billion Btu/yr.  Based on the costs and energy
impacts, we do not believe a beyond-the-floor standard is justified.

	We did not examine a beyond-the-floor regulatory option for new sources
because there are no controls that would, on average, generate a greater
THC reduction than a combination of a wet scrubber/RTO.  Thus, the floor
level is also new source MACT.

	3.	Conclusion

	The limit for new sources adopted here also applies to both area and
major new sources.  The application of this limit to area sources is a
result of the requirements of section 112(c)(6) which states that MACT
controls should be applied to HAP listed in section 112 (c)(6).
Therefore, polycyclic organic matter (for which THC is a surrogate) for
both area and major sources should be subject to MACT standards.  (See
63 FR 14193 – 14194).  For this reason, we are applying the 20 ppmv/98
percent reduction limit to both major and area sources.  We are also
applying the limit to raw materials dryers.  We anticipate that all new
kilns will be preheater/precalciner kilns with an inline raw mill (i.e.
there will be no separate dryer exhaust).  This is the design of the
kilns that form the basis of new source MACT for THC.  However, we see
no reason that the floor level of control should not apply in the case
where there is a separate raw material dryer.  We note that in the
original NESHAP, the 50 ppmv standard also applied to raw material
dryers.

	We are retaining our proposed requirement that compliance for a THC
standard will be demonstrated using a CEM and a 1-hour averaging period.
 See 70 FR 72340.  The previous 50 ppmv standard for new greenfield
sources was based on a monthly average.  We believe a monthly average
was appropriate for that standard (and are retaining monthly averaging
for kilns subject to that standard) because the standard’s basis is
selection of raw materials.  There can be significant short term
variations in raw materials, even if a facility can meet the standard in
the long term.  In the case of these final amendments the required level
of performance is based on an emissions control technology.  Therefore
we do not anticipate the same type of short term variability that
existed with the previous 50 ppmv standard.

	We are also using the discretion granted under section 112(i)(1) to
grant new sources three years from [INSERT THE DATE OF PUBLICATRION OF
THE FINAL AMENDMENTS IN THE FEDERAL REGISTER] or startup, whichever is
later, to comply with the new source standards.  We have this discretion
whenever we promulgate a final standard that is more stringent than the
proposed standard, which is the case here.

D.  Evaluation of a Beyond-the-floor Control Option for Non-Volatile HAP
Metal Emissions

	In our MACT determination for PM (the surrogate for non-volatile HAP
metals), we concluded that well-designed and properly operated fabric
filter (FF) or electrostatic precipitator (ESP) designed to meet the new
source performance standards (NSPS) for portland cement plants represent
the MACT floor technology for control of PM from kilns and in-line
kiln/raw mills.  Because no technologies were identified for existing or
new kilns that would consistently achieve lower emissions than the NSPS,
EPA concluded that there was no beyond-the-floor technology for PM
emissions (63 FR 14199, March 24, 1998).

	  SEQ CHAPTER \h \r 1 In National Lime Association v. EPA, the court
held that EPA had failed to adequately document that substituting
natural gas for coal was an infeasible control option, and also that EPA
had not assessed nonair environmental impacts when considering
beyond-the-floor standards for HAP metals (233 F. 3d at 634-35).  As a
result, the court remanded the beyond-the-floor determination for HAP
metals for further consideration by EPA.

	We presented our reexamination of a beyond-the-floor MACT control
standard for HAP metals in the preamble to the proposed amendments,
addressing the remand by showing that substitution of fuel or feed
materials are either technically infeasible or cost prohibitive and
therefore that a beyond-the-floor standard for HAP metals is not
reasonable.  (See 70 FR 72340-72341).  We received no data in the
comments on the proposed amendments that have altered our previous
analysis.  Therefore, we are not including a beyond-the-floor PM
standard in these final amendments.

V.  Other Rule Changes

	On April 5, 2002, we amended the introductory text of 40 CFR 63.1353(a)
to make it more clear that affected sources under the Portland Cement
NESHAP were not subject to 40 CFR part 60, subpart F (67 FR 16615, April
20, 2002).  In making this change, we inadvertently deleted paragraphs
(a)(1) and (2) of 40 CFR 63.1353.  The language in these paragraphs is
still necessary for determining the applicability of 40 CFR part 60,
subpart F.  We proposed to reinstate these paragraphs as originally
written in the final rule.  We received no comments on this issue and
are therefore reinstating the two paragraphs as proposed.

	In the proposed amendments we requested comment on amending language
published on April 5, 2002, whose purpose was to clarify that crushers
were not subject to this NESHAP.  The Portland Cement Association (PCA)
believed that there had been misinterpretation of the amended rule text.
 However, we explained in the proposed amendments that we believe the
PCA interpretation is not reasonable when reading the entire final
NESHAP.  However, we agreed that that the rule language as written is
conceivably open to more than one interpretation.  See 70 FR 72341.

	We proposed two resolutions to this issue.  They were:

	(1)  Changing the wording of 40 CFR 63.1340(c) to make it clear that
all raw materials storage and handling is covered by the NESHAP, but
that crushers (regardless of their location) are not.

	(2)  Including crushers as an affected source in the Portland Cement
NESHAP and incorporating the current requirements applicable to crushers
contained in 40 CFR part 60, subpart OOO (and correspondingly, exempting
crushers covered by the Portland Cement NESHAP from 40 CFR part 60,
subpart OOO).

	We received several comments from State and local agencies supporting
our contention that the intent of the rule language at issue was to
exclude crushers, and that our interpretation of the rule language was
correct.   We considered simply deleting the (potentially) confusing
language and adding clarifying language that a crusher located after raw
materials storage would be covered by this subpart.  However, we have
not been able to identify any facilities where the crusher is located
after raw materials storage.  In addition, we do not have data to
determine the impacts of adding coverage of this piece of equipment to
this subpart.  For that reason, we are modifying the language in
paragraph 63.1340(c) to state that crushers are not covered by this
subpart regardless of their location.  These are currently no
regulations that regulate existing crushers in this application.  New
crushers would potentially be subject to the requirements of 40 CFR 60
Subpart OOO.

VI.  Responses to Major Comments

This section presents a summary of responses to major comments.  A
summary of all comments received and our responses to those comments may
be found in Docket ID No. EPA-HQ-OAR-2002-0051.

Comment:  According to several commenters, EPA did not satisfy the
mandate issued by the DC Circuit Court of Appeals. On EPA’s analysis
of MACT for mercury, HCl, and THC; EPA’s beyond-the-floor analysis;
and the risk-based exemptions from HCl standards, one commenter states
they are unlawful, arbitrary, capricious, and irrelevant. These
commenters state that the court was clear in its directive to EPA that
the absence of technology-based pollution control devices for HCl,
mercury, and THC did not excuse EPA from setting emission standards for
those pollutants.

Response: Although we disagree with the premise of this comment, the
comment is moot because we are setting standards for all HAP which were
addressed by the court’s mandate.  We agree that the court stated the
absence of technology-based pollution control devices for HCl, mercury,
and THC did not excuse EPA from setting emission standards for those
pollutants.  In response to the court’s opinion, we have evaluated all
possibilities of setting standards, including technology based control,
fuel and raw materials changes, and process modifications.  We believe
this evaluation is what the court intended.  See 70 FR 72335.

Comment:  Regarding EPA’s rejection of beyond-the-floor standards for
each HAP, one commenter states that EPA’s reasoning is both unrelated
to the relevant statutory mandate and arbitrary and capricious, as well
as completely ignoring currently available control measures of which EPA
is aware and which would result in reductions of emissions of mercury,
HCl, THC and other HAPs.

Response:  Where we have rejected beyond-the-floor standards we have
evaluated all available control methods that have been demonstrated for
this source category.  We also evaluated control technologies that have
not been demonstrated, but that we have reason to believe may be
effective (such as ACI).  With one exception, which is banning the use
of fly ash with elevated mercury contents that result from sorbent
injection where such a practice would increase mercury emissions, in no
case did we find that the standard was justified (“achievable” in
the language of section 112 (d)(2)) taking into consideration costs,
energy, and nonair environmental impacts.

Comment:  According to one commenter, EPA’s refusal to set mercury
standards demonstrates contempt of court. The commenter states that
EPA’s reconsideration of MACT for mercury did not satisfy the
court’s directive to establish emissions standards and not just
reconsider the issue.

Citing the CAA’s requirements to set emission standards for each HAP
listed in 112(b) and, as directed in 112, for each category of sources
for the HAP applying the maximum achievable degree of reduction, the
commenter states that EPA’s decision to not set mercury emission
standards is unlawful.

Response:  This comment is moot, even accepting the commenter’s
premise (which EPA does not), since EPA is establishing standards (in
the sense the commenter uses the term) for each HAP covered by the
court’s mandate.

Comment:  The commenter states that EPA’s arguments for not setting
mercury standards are without merit and provides several justifications
for its view. First the commenter states that EPA’s arguments for not
setting mercury standard are irrelevant because EPA has a clear
statutory obligation to set mercury standard and any reason for not
doing so must be invalid.  Response:  this comment is now moot, as just
explained.

Second, according to the commenter, EPA’s view as to what is
achievable cannot replace the CAA requirement to set MACT floors
reflecting what the best performing sources are achieving. The commenter
states that the CAA mandates a floor reflecting the average emission
limitation achieved by the best performing 12 percent of the existing
sources (for which the Administrator has emissions information) and not
what EPA believes would be achievable. The commenter states that the
court expressly required EPA to set emission standards based on what the
best performers are actually achieving and not what EPA thinks is
achievable.  Response:  As Mossville and earlier cases make clear,
because MACT standards (based on floors or otherwise) must be met at all
times, the standards must reflect maximum possible variability (assuming
proper design and operation of the various control mechanisms).  See
discussion at 70 FR 72335 and 70 FR 59436.

Third, the commenter disagrees with EPA’s argument that the governing
case law (National Lime Ass’n and CKRC) did not involve facts where
the levels of performance tests are dependent entirely on composition of
raw materials and fuel and cannot be replicated or duplicated. The
commenter states that the governing case law addresses that exact issue:
 EPA’s decision not to set mercury standards; and fourth the commenter
claims EPA mistakenly cites the Copper Smelters (Sierra Club)and PVC
MACT cases (Mossville)as justification for its approach. According to
the commenter, these cases pertain to beyond-the-floor standards and do
not apply to floor standards, which require EPA to set floors at
emission levels that the best sources achieved, regardless of what EPA
thinks is achievable.

Response:  The commenter’s reading of Mossville is not correct.  The
case involved a floor standard.  See 370 F. 3d at 1240-42.  We explained
at proposal why we also believe the discussion of raw materials in
Sierra Club is also applicable to a floor determination.  See 70 FR at
72335 n. 4.

Fifth, regarding EPA’s argument that its emissions data do not reflect
performance over time, the commenter states that this merely relates to
the sufficiency of EPA’s data. The commenter states that EPA is
required to develop an approach to setting a floor standard, including
collecting more emissions data if needed.  Response:  First, floor
standards are to reflect the performance of sources “for which the
Administrator has emissions information” (section 112 (d) (3)), which
provision does not create an obligation to gather a specified amount of
information.  Second, not only must MACT standards, including standards
reflecting the MACT floor, reflect performance variability but EPA may
reasonably estimate what that variability can be, and is not limited to
stack emissions measured in single performance tests as the commenter
apparently believes.  See Mossville, 370 F. 3d at 1242 (setting standard
at a level slightly higher than the highest data point experienced by a
best performing source “reasonably estimates the performance of the
best … performing sources”).  Most basically, because MACT standards
must be met at all times, a standard must reflect performance
variability that occurs at all times, and this variability is simply not
accounted for in single stack test results for mercury from a cement
kiln.

Sixth, the commenter disagrees with EPA’s position that setting the
floor at emission levels achieved by the relevant best sources would
require kilns to install back-end controls, thus bypassing
beyond-the-floor requirements of achievability, considering cost and
other statutory factors. Contrary to EPA’s position, the commenter
argues that sources are using low mercury fuel and feed and some kilns
are using controls that reduce mercury emissions, albeit they may not be
doing so deliberately to reduce mercury emissions. According to the
commenter, whether the sources are achieving low mercury emissions
levels through deliberate measures or coincidentally is statutorily
irrelevant.

General Response:  We disagree with all the points raised in the comment
that EPA’s arguments for not setting mercury standards are without
merit.  As noted above, we believe we have met the court’s directive
by evaluating all available methods of mercury control, including
changes to fuels, raw materials, and process controls.  We do not agree
that the court directed us to set standards regardless of the facts, nor
do we agree that section 112(d)(3) of the CAA requires us to set floor
standards that cannot be met without requiring even the best performing
facilities to apply beyond-the-floor controls – controls not used by
any sources in the source category, even those which are ostensibly the
best performing (i.e. the lowest emitters in individual performance
tests).

	The commenter correctly noted that we are required to set standards
based on facilities for which the administrator has emissions
information.  However, as explained previously in the notice, the
emissions levels in the data available to the administrator are mainly
influenced by factors that are beyond the control of the facilities
tested, and the test results can neither be replicated by the individual
facilities nor duplicated by other facilities.  In addition, these are
short term data that we believe are not indicative of the sources’long
term emissions.  The commenter states that we should get better data.
However, they do not indicate how we would be able to perform this task
given the fact that there are no long term data available for mercury
emissions from cement kilns:  we know of no case where any cement
facility has applied mercury CEM technology, or gathered any long term
emissions data we could use to set a national standard.

The commenter further states that docket records for portland cement,
the hazardous waste standards, and electric utilities demonstrate that
various pollution controls have the ability to reduce mercury emissions.
 We agree with this comment in part.  We believe both ACI and wet
scrubbers will reduce mercury from cement kilns (and the floor for
mercury for new sources is based on performance of a wet scrubber).  We
did evaluate these controls as beyond-the-floor control options and
determined, based on what we consider reasonable assumptions of their
performance, that requiring facilities to apply these controls was not
achievable, within the meaning of section 112 (d) (2) of the Act, after
considering costs, energy impacts, and nonair environmental impacts.

	We also agree that fabric filters and ESPs can reduce mercury emissions
because there is some mercury retained in the collected CKD.  As
explained earlier, we agree that this forms the basis of a MACT floor
(and standard), although the degree of mercury reduction is
site-specific based on the rate of recycling per kiln.  Because the
amount of emission reduction associated with the practice is site
specific and not directly measurable, we are expressing the standard as
a work practice.  We also explained why requiring further reductions
based on more CKD wastage is not justified as a beyond-the-floor
standard based on considerations of cost and nonair adverse impacts
(increased waste generation and disposal), as well as increased energy
use.

	In no case did we find that any of the control options discussed by the
commenter could be considered as the basis for a MACT floor for new or
existing sources (with the two exceptions just noted) for reasons
previously discussed.

	We also note that the HWC NESHAP does have mercury limits.  However,
these limits are achieved by controlling the mercury input of the
hazardous waste feed.  Therefore, any comparison of the mercury limits
for cement kilns that burn hazardous waste with cement kilns that do not
is misplaced.

	The commenter notes that cement kilns are achieving superior mercury
emissions through a variety of different means, and further states that
whether they are doing this intentionally is legally irrelevant.  The
comment is correct that the reason for application of a particular
control technique is irrelevant.  National Lime, 233 F. 3d at 640.  But
the commenter fails to consider that even in the case where a facility
applies some type of control scheme, and that scheme happens to also
reduce a particular HAP, the facility still is still taking specific
actions that results in a reduction of the pollutant.  For example, a
facility that installs a thermal oxidizer to reduce total hydrocarbons
also reduces organic HAP, even though the thermal oxidizer may not have
been installed for purposes of HAP reduction   However, the facility is
still taking a specific action that reduces HAP emissions.  Also,
another facility can install a similar control device and expect to
achieve the same result.  Results thus can be duplicated from site to
site.

In the case of cement kilns, the “actions” being taken that in some
cases may reduce mercury emissions are the result of site specific
factors that cannot necessarily be duplicated elsewhere.  For example, a
facility A may achieve lower mercury emission that facility B simply
because the limestone quarry used by facility A has a lower mercury
content (at least on the day of the respective performance tests).
Facility A is not achieving a lower mercury emissions deliberately, but
it is still achieving a lower level.  However, because facility B does
not have access to facility A’s quarry, it would have to use some
other control technique to match facility A’s mercury emissions.  The
commenter never disputes that requiring facility B (and quite possibly
A) to match the performance will require installation of a control
device not used in the industry.  As explained at proposal and earlier
in the preamble, this amounts to an impermissible de facto
beyond-the-floor standard.

	The commenter also states that the best performing kilns are achieving
lower mercury emission using a variety of methods, but does not offer
any data or analysis as to what these methods are, or how other
facilities could duplicate the performance of the lower emitting
facilities without adding some type of back end controls.  In addition,
due to the wide variation in emissions level due to variations in raw
materials, we have no data to show conclusively that even if back end
controls were applied that kilns with higher mercury emissions due to
higher mercury contents in their limestone could achieve the same
emissions levels as facilities with naturally occurring low mercury
limestone used in the (one-time, snapshot) performance test.

Comment:  Regarding EPA’s rejection of a beyond-the-floor mercury
standard on the basis of low levels of mercury emissions and high costs
or reducing emissions, one commenter states that the CAA requires that
EPA’s standards must reflect the “maximum degree of reduction that
is achievable” considering the “cost of achieving such emission
reduction” and other enumerated statutory factors. According to the
commenter, the only relevant factors regarding the cost measures are: 1)
whether it is too costly to be “achievable”; and 2) whether it would
yield additional reductions, i.e., without the measure, the standard
would not reflect the “maximum” achievable degree of reduction. The
commenter states that EPA does not claim that the use of ACI would not
be achievable, only that ACI is not “justified.” This position,
according to the commenter, contravenes the CAA and exceeds EPA’s
authority and would allow EPA to avoid properly determining the maximum
degree of reduction achievable considering cost and the other enumerated
factors.

Response:  We disagree with the commenter’s interpretation.

The statute requires that EPA consider “the cost of achieving such
emission reduction” (section 112 (d)(2)) in determining the maximum
emission reduction achievable.  This language does not mandate a
specific method of taking costs into account, as the commenter would
have it, but rather leaves EPA with significant discretion as to how
costs are to be considered. See Husqvarna AB v. EPA, 254 F. 3d 195, 200
(D.C. Cir. 2001).  In that case, the court interpreted the requirement
in section 213 (a) (3) of the Act (which mirrors the language in section
112(d)(2))that nonroad engines “achieve the greatest degree of
emission reduction achievable through the application of [available]
technology … giving appropriate consideration to the cost of applying
such technology”, and held that this language “does not mandate a
specific method of cost analysis”.  The court therefore “f[ound]
reasonable the EPA’s choice to consider costs on the per ton of
emissions removed basis”.

	Moreover, where Congress intended that economic achievability be the
means of assessing the reasonableness of costs of technology-based
environmental standards, it says so explicitly.  See Clean Water Act
section 301 (b) (2) (A) (direct dischargers of toxic pollutants to
navigable waters must meet standards reflecting “best available
technology economically achievable” (emphasis added). There is no such
explicit directive in section 112 (d)(2).  EPA accordingly does not
accept the commenter’s interpretation.

Comment:  Several comments support EPA’s decision not to develop
either an existing or new source floor for mercury.  The commenters
state that an achievable floor cannot be developed because wide
variation in mercury concentrations in raw materials and fuels used by
cement kilns would make compliance impossible.  One commenter also
agrees with EPA’s statement that a national conversion of cement kilns
to natural gas is not possible due to serious supply problems and the
lack of an adequate natural gas infrastructure.

Response:  We agree with these comments insofar as they apply to floors
reflecting changes in raw material or fuel inputs.

Comment:  One commenter restates its original position that EPA’s
arguments regarding its inability to establish floors are irrelevant,
unlawful and arbitrary. The commenter states that evidence made
available since the original comment period closed confirms that 1) some
kilns perform better than others; 2) consistent and predictable
differences in emission levels can be attributed to differences in the
raw materials, fuel, kiln design and control technology; and 3)
additional measures for controlling mercury emissions are available to
kilns. The commenter states that there is evidence that a) some kilns
use raw materials that are consistently higher or lower in mercury than
other kilns as evidenced by a cement kiln in Tehachapi, CA that uses
limestone from a quarry adjacent to an abandoned mercury mine and
consistently reports high (2000 lb/yr) mercury emissions - other kilns
have consistently lower mercury levels because they use raw materials
with low mercury levels; b) there are many measures by which mercury
emissions can be reduced as exemplified by Holcim’s statement that
mercury emissions can be controlled by careful input control and EPA’s
acknowledgement that mercury emissions are affected by the use of
mercury-contaminated fly ash - as only 39 of 112 plants choose to use
fly ash, the commenter states that a plant’s deliberate choice about
using fly ash (as well as the choice by some to burn tires, or choosing
to burn a rank of coal lower in mercury, and use of by products from
steel mills and foundries and flue gas dryer sludge) results in
consistent and predictable differences in their mercury emissions; c)
wet kilns emit more mercury than dry kilns (twice as much according to
EPA), showing that the kiln design results in a consistent and
predictable difference in mercury emissions; and d) additional emissions
data confirm that some kilns are achieving consistently better emission
levels than others.

Several comments were received regarding the adequacy of the emissions
data used in EPA’s analyses. Several commenters state that EPA should
collect data on mercury emissions and then determine mercury limits
based on data. Recommendations for collecting additional data included
soliciting test data from State and local agencies. Several commenters
state that EPA should conduct a new MACT floor and beyond-the-floor
evaluation based on current and complete data - including data from
state and local agencies where cement plants are located - on mercury
emissions from portland cement plants. According to one commenter, EPA
explained that its decision not to set mercury standards was due to a
lack of emissions data while in reality it chose not to gather data
under an incorrect statutory interpretation that it did not have to set
standards if it believed there was no control technology available. The
commenter states that now EPA has access to more mercury emissions data
than it initially claimed including 1) TRI data based on mercury stack
monitoring by 35 plants and, 2) as indicated by EPA, data on mercury
content of coal fly ash, shale, and clay that is either already
available or can be easily obtained from existing sources – the
commenter notes that Florida DEP reports that kilns collect several
samples of the mercury levels in their raw materials on a daily basis.

Response:  We disagree that our arguments regarding the inability to
establish floors are irrelevant, unlawful and arbitrary.  We agree that
some kilns emit less mercury than others in individual performance
tests. The argument that these kilns consistently perform better over
time than other kilns is not correct, however, as shown in section
IV.A.1.a above, where we showed that one of the lowest emitting kilns in
a single test was one of the highest emitting in a later test due to raw
material mercury variability.  We thus do not believe it is appropriate
to use the term “perform better then others” because this implies
that the emission levels achieved are the result of some controllable
action or otherwise will perform over time at some predictable level.  A
facility cannot achieve a performance level similar to another facility
by varying its inputs because, as previously discussed, one facility
does not have access to another’s raw materials (or fuels), and
therefore cannot be expected to necessarily achieve the same mercury
emissions levels based on input control.  The commenter acknowledges
that facilities have significant variations in raw materials mercury
content.

	The commenter also notes that only some facilities choose to use fly
ash which results in predictable and consistent differences in mercury
emissions.  While the statement that only some facilities use fly ash is
correct, there are no data to indicate that the use of fly ash results
in consistent and predictable differences in mercury emissions.  All the
raw materials and fuels that enter the kiln affect mercury emissions.
The decision to use fly ash may or may not affect mercury emissions
based on the mercury content of the raw materials the fly ash replaces.
The only way to predict the impact on mercury emissions of fly ash for
the plant currently using this material would be to obtain long term
detailed raw materials and fuel analyses for every plant, including
analyses of the replaced materials.  However, in many cases the replaced
materials may no longer be available.  Neither are the data available
for the current materials being used.  In no way does the use of fly ash
make the mercury emissions any more consistent than for facilities not
using fly ash, or vice versa.  Al kilns are still subject to
uncontrollable variations in raw materials and fuels, of which fly ash
is only a small part.  In fact, the two facilities with the highest
measured mercury emissions do not use fly ash, and one of these
facilities, which happens to have 30 days of feed materials analyses for
mercury, shows significant variations in mercury emissions.  There are
no data to support any contention that using fly ash will inevitably
result in a mercury emissions increase at any specific site.

The commenter also stated that kiln design – wet versus dry -- affects
mercury emissions.  There are no data to support that statement, nor are
we aware of any reason a wet or dry kiln would perform differently with
respect to mercury emissions.  The information referred to by the
commenter is from the Toxic Release Inventory.  These data do not
differentiate between kilns that burn hazardous waste, which are a
different class of kiln subject to different regulations, and those that
do not.  Cement kilns that burn hazardous waste tend to be wet kilns and
also tend to have higher mercury emission than kilns that do not burn
hazardous waste, because of higher mercury levels in the hazardous waste
fuels burned by these kilns.  Therefore, the data cited by the commenter
do not support their conclusion.

	Several commenters also suggested that EPA collect additional emission
test data from State and local agencies.  We collected additional data,
and have begun the process of gathering more.  See section IV.A.1.b
above, and the separate notice in today’s Federal Register announcing
reconsideration of the new source standard for mercury.  We believe
these data conclusively show that the variations in raw materials
mercury content show that any mercury limit based on these data would
not be achievable on a continuous basis, even by the kilns that form the
basis of the floor, without the requirement of applying beyond-the-floor
back end control technology.  The TRI monitoring data referenced by one
commenter is actually short term tests.  To our knowledge, there are no
cement kilns using mercury continuous monitors.  The data the commenter
referenced from Florida are daily samples, but they are only analyzed on
a monthly basis.  In any case, any emission limit based on these data
would not solve the problem that other facilities do not have access to
the same raw materials.

Comment:  In commenting on the adequacy of EPA analysis of the MACT
floor for existing and new sources, several comments were received
recommending that EPA give further consideration to requiring the use of
emission control technology for reducing mercury emissions.

Several commenters state that EPA’s analysis should have considered