

[Federal Register: September 27, 2007 (Volume 72, Number 187)]
[Proposed Rules]
[Page 54875-54888]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr27se07-23]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2004-0022; FRL-8474-2]
RIN 2050-AG29


NESHAP: National Emission Standards for Hazardous Air Pollutants:
Standards for Hazardous Waste Combustors

AGENCY: Environmental Protection Agency (EPA).

ACTION: Solicitation of comment on legal analysis.

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SUMMARY: On October 12, 2005, pursuant to section 112(d) of the Clean
Air Act, EPA issued national emission standards for hazardous air
pollutants (NESHAP) emitted by various types of hazardous waste
combusters. EPA subsequently granted reconsideration petitions relating
to certain issues presented by the rules. 71 FR 14665, 52564, but has
not yet issued a final determination on reconsideration. Following the
close of the comment period on the proposed reconsideration rule, the
United States Court of Appeals for the District of Columbia Circuit has
issued several opinions construing section 112 (d) of the Clean Air
Act, and one of those opinions has called into question the legality of
some of the standards for hazardous waste combusters. This notice
discusses the standards that EPA promulgated in October 2005, and
specifically identifies which standards EPA believes are consistent
with the Act and caselaw, and which standards are not and need to be
reexamined through a subsequent rulemaking. With respect to those
standards EPA intends to retain, this notice indicates the portions of
the rationale upon which EPA intends to rely, and which portions EPA
would no longer rely upon as a justification for the October 2005
standards. EPA is seeking public comment on this analysis. EPA has also
placed edited versions of various support documents in the public
docket, edited to remove portions of the rationale on which EPA no
longer plans to rely, and seeks public comment on these edits.

DATES: Comments must be received on or before October 18, 2007.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2004-0022, by one of the following methods:
     http://www.regulations.gov: Follow the on-line instructions for

submitting comments.
     E-mail: a-and-r-docket@epa.gov.
     Fax: 202-566-1741.
     Mail: U.S. Postal Service, send comments to: Air and
Radiation Docket (2822T), Docket ID No. EPA-HQ-OAR-2004-0022, U.S.
Environmental Protection Agency, 1200 Pennsylvania Avenue, NW.,
Washington, DC 20460. Please include a total of two copies.
     Hand Delivery: In person or by courier, deliver comments
to: HQ EPA Docket Center, Public Reading Room, EPA West, Room 3334,
1301 Constitution Avenue, NW., Washington, DC 20004. Such deliveries
are only accepted during the Docket's normal hours of operation, and
special arrangements should be made for deliveries of boxed
information. Please include a total of two copies.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2004-0022. The EPA's policy is that all comments received will be
included in the public docket without change and may be made available
online at http://www.regulations.gov, including any personal information

provided, unless the comment includes information claimed to be
Confidential Business Information (CBI) or other information the
disclosure of which is restricted by

[[Page 54876]]

statute. Do not submit information that you consider to be CBI or
otherwise protected through http://www.regulations.gov or e-mail. The

http://www.regulations.gov Web site is an ``anonymous access'' system, which

means EPA will not know your identity or contact information unless you
provide it in the body of your comment. If you send an e-mail comment
directly to EPA without going through http://www.regulations.gov, your e-mail

address will be automatically captured and included as part of the
comment that is placed in the public docket and made available on the
Internet. If you submit an electronic comment, EPA recommends that you
include your name and other contact information in the body of your
comment and with any disk or CD-ROM you submit. If EPA cannot read your
comment due to technical difficulties and cannot contact you for
clarification, EPA may not be able to consider your comment. Electronic
files should avoid the use of special characters, any form of
encryption, and be free of any defects or viruses. For additional
information about EPA's public docket visit the EPA Docket Center
homepage at http://www.epa.gov/epahome/dockets.htm.

    Docket: All documents in the docket are listed in the
http://www.regulations.gov index. Although listed in the index, some

information is not publicly available, e.g., CBI or other information
the disclosure of which is restricted by statute. Certain other
material, such as copyrighted material, will be publicly available only
in hard copy. Publicly available docket materials are available either
electronically in http://www.regulations.gov or in hard copy at the HQ EPA

Docket Center, Public Reading Room, EPA West, Room 3334, 1301
Constitution Avenue, NW., Washington, DC 20004. 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
(202) 566-1744, and the telephone number for the HQ EPA Docket Center
is (202) 566-1742. A reasonable fee may be charged for copying docket
materials.

FOR FURTHER INFORMATION CONTACT: For more information on this notice,
contact Frank Behan at (703) 308-8476, or behan.frank@epa.gov, Office
of Solid Waste (5302P), U.S. Environmental Protection Agency, 1200
Pennsylvania Ave., NW., Washington, DC 20460.

SUPPLEMENTARY INFORMATION: Entities Potentially Affected by this
Action. Categories and entities potentially affected by this action
include:

------------------------------------------------------------------------
                                      NAICS      Potentially affected
              Category               code\a\           entities
------------------------------------------------------------------------
Petroleum and coal products              324  Any entity that combusts
 manufacturing.                                hazardous waste as
                                               defined in the final
                                               rule.
Chemical manufacturing.............      325
Cement and concrete product             3273
 manufacturing.
Other nonmetallic mineral product       3279
 manufacturing.
Waste treatment and disposal.......     5622
Remediation and other waste             5629
 management services.
------------------------------------------------------------------------
\a\ 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 impacted by this
action. This table lists examples of the types of entities EPA is now
aware could potentially be regulated by this action. Other types of
entities not listed could also be affected. To determine whether your
facility, company, business, organization, etc., is affected by this
action, you should examine the applicability criteria in 40 CFR
63.1200.\1\ If you have any questions regarding the applicability of
this action to a particular entity, consult the person listed in the
preceding FOR FURTHER INFORMATION CONTACT section.
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    \1\ Unless otherwise noted, all regulatory references in this
notice are to 40 CFR.
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    How Do I Obtain a Copy of this Document and Other Related
Information? In addition to being available in the docket, an
electronic copy of today's proposed rule will also be available on the
World Wide Web (WWW). Following the Administrator's signature, a copy
of this document may be posted on the WWW at http://www.epa.gov/hwcmact.
 This Web site also provides other information related to the

NESHAP for hazardous waste combustors including the NESHAP issued on
October 12, 2005 (70 FR 59402) and the two petition for reconsideration
notices published on March 23, 2006 (71 FR 14665) and September 6, 2006
(71 FR 52624).
    Preparation of Comments. Do not submit this information to EPA
through http://www.regulations.gov or e-mail. Clearly mark the part or all of

the information that you claim to be CBI. For CBI information in a disk
or CD-ROM that you mail to EPA, mark the outside of the disk or CD-ROM
as CBI and then identify electronically within the disk or CD-ROM the
specific information that is claimed as CBI. In addition to one
complete version of the comment that includes information claimed as
CBI, a copy of the comment that does not contain the information
claimed as CBI must be submitted for inclusion in the public docket.
Information so marked will not be disclosed except in accordance with
procedures set forth in 40 CFR part 2. Send or deliver information
identified as CBI to only the following address: Ms. LaShan Haynes,
RCRA Document Control Officer, EPA (Mail Code 5305P), Attention Docket
ID No. EPA-HQ-OAR-2004-0022, 1200 Pennsylvania Avenue, Washington DC,
20460. Clearly mark the part or all of the information that you claim
to be CBI.
    Tips for Preparing Your Comments. When submitting comments,
remember to:
     Identify the rulemaking by docket number and other
identifying information (subject heading, Federal Register date and
page number).
     Follow directions--The agency may ask you to respond to
specific questions or organize comments by referencing a Code of
Federal Regulations (CFR) part or section number.
     Explain why you agree or disagree; suggest alternatives
and substitute language for your requested changes.
     Describe any assumptions and provide any technical
information and/or data that you used.
     If you estimate potential costs or burdens, explain how
you arrived at your estimate in sufficient detail to allow it to be
reproduced.
     Provide specific examples to illustrate your concerns, and
suggest alternatives.
     Explain your views as clearly as possible.
     Make sure to submit your comments by the comment period
deadline identified.
    Organization of this Document. The information presented in this
notice is organized as follows:


[[Page 54877]]


I. Background
II. Consideration of Variability in Establishing MACT Floors
III. Discussion of Individual Standards
    A. Standards for Particulate Matter
    1. Standards for Incinerator, Cement Kilns, Lightweight
Aggregate Kilns, and Solid Fuel Boilers
    2. Standards for Liquid Fuel Boilers
    B. Standards for Semivolatile Metals and Low Volatility Metals
    1. Methodology to Establish Floor Levels
    2. Alternatives to the Particulate Matter Standard for
Incinerators, Liquid Fuel Boilers, and Solid Fuel Boilers
    3. Alternative Mercury, Semivolatile Metals, Low Volatile
Metals, and Total Chlorine Standards for Cement Kilns and
Lightweight Aggregate Kilns
    4. Alternative Mercury Standards for Cement Kilns and
Lightweight Aggregate Kilns Under the Interim Standards
    C. Standards for Total Chlorine
    1. Incinerators
    2. Cement Kilns
    3. Lightweight Aggregate Kilns
    4. Liquid Fuel Boilers
    5. Solid Fuel Boilers
    6. Hydrochloric Acid Production Furnaces
    D. Standards for Dioxins/Furans
    1. Incinerators
    2. Cement Kilns
    3. Lightweight Aggregate Kilns
    4. Liquid Fuel Boilers
    E. Non-Dioxin Organic HAP
    F. Mercury
    1. Incinerators
    2. Cement Kilns
    3. Lightweight Aggregate Kilns
    4. Liquid Fuel Boilers
    5. Solid Fuel Boilers
    G. Normalization
    H. Potential Implications to the Compliance Date Provisions If
Standards Are Remanded to EPA

I. Background

    The Hazardous Waste Combustor (HWC) Maximum Achievable Control
Technology (MACT) rule, 70 FR 59402 (October 12, 2005), adopts separate
standards for six source categories, the common link being that sources
in each category burn hazardous waste. These sources are incinerators,
cement kilns, lightweight aggregate kilns, solid fuel boilers, liquid
fuel boilers, and hydrochloric acid production furnaces. Liquid fuel
boilers are further subcategorized into those burning higher heating
value hazardous wastes and lower heating value hazardous wastes. The
following hazardous air pollutants (``HAP'') are regulated for each of
these source categories: dioxins and furans (``D/F''); semivolatile
metals (lead and cadmium) (``SVM''); low volatile metals (arsenic,
beryllium and chromium) (``LVM''); mercury, particulate matter (``PM'')
(as a surrogate for the remaining HAP metals (antimony, cobalt,
manganese, nickel, and selenium), and also to control HAP metals in all
inputs to the units which are not hazardous waste); hydrogen chloride/
chlorine (measured as total chlorine) (``TCl''); carbon monoxide/total
hydrocarbons (``CO/HC'') (as surrogates for non-dioxin organic HAP (and
in a few cases, dioxin as well); and destruction removal efficiency
(``DRE'') (an aspect of control of non-dioxin organic HAP, and in a few
cases, dioxin).
    On March 13, 2007, the United States Court of Appeals for the
District of Columbia Circuit (D.C. Circuit) issued its decision in
Sierra Club v. EPA, 479 F.3d 875 (2007) (``Brick MACT''). EPA has
reexamined the rule to determine if it is compliant with the statute
with respect to the issues discussed in the Court's opinion, and
specifically whether the MACT floors for each standard are compliant.
For the most part, EPA believes that they are. The basic reason, for
those standards EPA plans to retain, is that the rule identifies as
best performers--the best performing 12 per cent or best performing
five sources in smaller source categories for existing sources, and the
best controlled single source for new sources--those sources which are
likely to emit the least HAP over time, and reasonably estimates these
sources' level of performance. Put another way, the rule identifies as
best performers those emitting the least HAP considering variability
(i.e., their performance over time), and accounts for that variability
as much as possible in estimating these sources' level of performance.
See 70 FR at 59346 (``best performers are those that perform best over
time (i.e., day-in, day-out)'').
    The statute does not address the question of whether, in assessing
which sources perform best or are best controlled, emission levels
should be evaluated over time, or in a single test result. Nor does
Brick MACT, which states at 479 F.3d 880 that ``section [112(d)(3)]
requires floors based on the emission level actually achieved by the
best performers (those with the lowest emission levels)'', but does not
refer to a time period for measurement. The following example shows why
it is reasonable to determine which sources are the best performers by
accounting in the first instance for what their emissions are over
time. Assume that source A in a single test emitted 10 units of
cadmium, and source B emitted 15 units. However, assume further that
over time source A emits cadmium at a rate of 40 units and source B
emits cadmium at a rate of 25 (the difference being that source B's
performance is less variable). It is at the very least reasonable to
view source B as the better performer; over time it emits less cadmium
than source A. Indeed, given that the chief health risks of most HAP
emitted by Hazardous Waste Combustors results from chronic rather than
acute exposure (i.e., amount of repeated exposure over time as opposed
to single exposure incidents), floor standards based on evaluation of
sources' performance over time (i.e., standards which account for
sources' variability) best address the sources' ultimate impacts on
human health. See 70 FR at 59533-35 where EPA discusses human health
benefits of the standards considering reductions in chronic exposure to
HAP.

II. Consideration of Variability in Establishing MACT Floors

    EPA may consider variability in identifying best performers and
their level of performance. See 70 FR at 59436. See also Brick MACT,
479 F.3d at 881-82 (variability of best performing sources may be taken
into account in establishing MACT floors).
    EPA in this rule identified two types of variability, run-to-run
variability and test-to-test variability. Run-to-run variability
``encompasses variability in individual runs comprising the compliance
tests, and includes uncertainties in correlation of monitoring
parameters and emissions, and imprecision of stack test methods and
laboratory analyses.'' 70 FR at 59437. A shorthand description is that
this is within-test variability. EPA quantified run-to-run variability
using the statistical methodology set forth in Technical Support
Document (``TSD'') Vol. III section 7.2; \2\ see also 70 FR at 59437/1-
2, 59438, and 59439 explaining the reasonableness of this statistical
approach. The chief element of this quantification is simply the
standard deviation in the performance test data (standard deviation
being the usual statistical measure for assessing variation within a
data set by comparing a single result with the average of the data
comprising the data set). The result is an estimate of the value which
the source would achieve in 99 of 100 future tests if it replicated the
operating conditions of the compliance test. 70 FR at 59437; \3\ see
also 69 FR at 21232 and n. 69 (April 20, 2004).
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    \2\ USEPA, ``Technical Support Document for HWC MACT Standards,
Volume III: Selection of MACT Standards,'' (TSD Vol. III) September
2005. Unless otherwise specified, all TSD references in this notice
are to this document, which is available in the docket to the rule.
See docket items EPA-HQ-OAR-2004-0022-0453, 0457, 0459, and 0460.
    \3\ More precisely, this is a modified prediction limit that
ensures at the 95% confidence level that the average of the best
performing sources could achieve the emission level in 99 or 100
future test conditions based on a three-run average, assuming the
best performers could initially replicate the compliance test
conditions. TSD Vol. III at 7-7; 70 FR at 59437.

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[[Page 54878]]

    Existence of run-to-run variability is confirmed most evidently by
the wide variations within different runs of the best performers'
performance tests. Moreover, simply averaging these different run
results would lead to standards which not even the best of the best
performers would achieve over time. TSD Vol. III section 16.4.
Comparative test results of best performing sources (i.e., tests of the
same source at a different time) strongly suggest that run-to-run
variability can be appreciable (although not the only measure of
variability), since these sources have been shown consistently to emit
more than the averaged emissions from the performance test identifying
the source as best performing. See TSD Vol. III Tables 16-4, 16-5, 17-
1, 17-3. Failure to consider run-to-run variability could seriously
underestimate a source's emissions over time. See TSD Vol. III section
17.3.3, showing that even the lowest emitting Straight Emission sources
could have emissions higher than floor levels under a methodology that
considers run-to-run variability. EPA has comparative data from a
number of lowest emitting incinerators for PM in single test results.
In other tests, these same sources were typically unable to achieve the
same level of performance, sometimes emitting up to seven times more
PM. 69 FR at 21232 and n. 69 (April 20, 2004).
    Test-to-test variability results from variability in pollution
device control efficiencies over time (depending on multitudinous
factors, including for fabric filters the point in the maintenance
cycle at which the source is tested, and for electrostatic
precipitators variations in combustion gas moisture and particle
resistivity), as well as measurement variability resulting from
different sampling crews under different meteorological conditions and
different analytical laboratories. Id. and n. 63. A shorthand
description is that this is long-term variability. EPA demonstrated
generally that: (a) Test-to-test variability exists; (b) it is not
encompassed in EPA's statistical quantification of run-to-run
variability; (c) the amount of test-to-test variability can be
significant such that failing to account for it in some manner means
that the sources' performance over time can be seriously underestimated
(i.e., since their long-term variability would be ignored); and (d)
sources which are lowest emitting in single emission tests may not be
the lowest emitters over time due to their test-to-test variability. 70
FR at 59437-438 and TSD Vol. III chapters 16 and 17; see also 70 FR at
59439 explaining why total variability is not accounted for by
compliance test conditions.
    EPA was able to provide a quantitative estimate of test-to-test
variability in only one instance--where fabric filters are used to
capture particulate matter. See discussion of PM standards in section
III.A. below. In other instances, EPA accounted for test-to-test (i.e.,
long-term) variability in one of two ways: (a) Selecting as best
performers those which minimized their long-term (i.e., test-to-test)
variability by best controlling the aspects of performance (notably
removal efficiency evaluated systemwide and hazardous waste HAP
feedrate) within their control, or (b) using a surrogate for the HAP
where EPA could assess the long-term variability associated with
emissions of that surrogate, but could not otherwise assess long-term
variability.
    EPA also carefully assessed a floor methodology which simply
assumed that the lowest emitters in individual performance tests were
the best performers. The major problem with such a methodology is that
it ignores the sources' performance over time, leading to situations
where the sources' level of performance may be assessed improperly. See
TSD Vol. III chapters 16 and 17; 70 FR at 59442-446 (explaining why
lowest emitters in individual performance tests \4\ are not always the
best performers). EPA consequently used this methodology to identify
best performers and their level of performance when it was not possible
to assess sources' waste feedrate and systemwide removal efficiency.
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    \4\ The heading to this preamble section should have explicitly
included the words ``in individual performance tests'' in the
section title.
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III. Discussion of Individual Standards

A. Standards for Particulate Matter

1. Standards for Incinerator, Cement Kilns, Lightweight Aggregate
Kilns, and Solid Fuel Boilers
    EPA adopted standards for particulate matter (``PM'') for all of
the hazardous waste combuster source categories except for hydrochloric
acid production furnaces.\5\ Particulate Matter is a surrogate for the
HAP metals antimony, cobalt, manganese, nickel, and selenium, the HAP
metals not covered by the standards for semi-volatile and low-volatile
HAP metals (referred to as `nonenumerated metals' in this rulemaking).
See section III.B. below. In addition, as explained in section III.B.,
the PM standard also controls all non-mercury HAP metals (i.e., semi-
volatile, low volatility, and nonenumerated HAP metals) in all
nonhazardous waste inputs to HWCs. 70 FR at 59459. Since the PM
standards are measured by total end-of-stack output, these standards
account for all HAP metal input to hazardous waste combustion devices
(other than mercury). Id.
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    \5\ The alternative metal standards, in lieu of PM standards,
for incinerators, and liquid and solid fuel boilers are discussed in
section III.B discussing standards using the SRE Feed floor
methodology.
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    EPA used the Air Pollution Control Device methodology to establish
floors for PM. Under this methodology, EPA determined as a matter of
engineering judgment which devices best control PM emissions, ranked
these means of control, and selected as the best performers those with
the lowest PM emissions using the best control device. See TSD Vol. III
section 7.4; see also id. at 16-2 ranking PM control devices from best
to worst for each source category. The floor for each source category
was then established based on the average of these lowest emitting
sources' PM emissions (or the lowest emitter of these sources for the
new source floor).
    In most instances, the lowest emitters in the performance test used
for determining best performers were equipped with the best control
device--some type of fabric filter (``FF''). Occasionally, a lower PM
emitter in a single test was equipped with some other type of control
device, or, in the case of three incinerators, no control device, but
EPA ranked these sources as lower (i.e., worse) performing than FF-
equipped sources. EPA reevaluated carefully whether the lower ranking
of these sources, in some instances resulting in their omission from
the pool of best performers, is consistent with the holding of Brick
MACT, 479 F.3d at 882-83, as well as Cement Kiln Recycling Coalition v.
EPA, 255 F.3d 855, 863-65 (D.C. Cir. 2001), that floors are not to be
set only on performance of sources equipped with certain technology
unless that is the only factor affecting emissions, and that EPA must
consider all means of control when selecting best performers.
    EPA of course accepts these holdings, and believes its approach
here is consistent with the statute and applicable case law. EPA
selected as best performers (or as the best controlled source) those
sources it estimated to have the lowest PM emissions over time. EPA's
selection process has a reasoned basis. Sources equipped with control
devices other than FFs are likely to emit more over

[[Page 54879]]

time than they do in individual test conditions, even after adjusting
test results to account for run-to-run variability. (Put another way,
these sources' performance in individual test conditions are likely not
representative of what they will emit over time.) This is because test-
to-test variability, that is, long-term variability, has not been taken
into account. Since these other control devices are known to be more
variable and less efficient than FFs, TSD Vol. III pp. 16-3 to 4 and
11, failure to consider long-term variability (i.e., looking
exclusively at results of single performance tests) results in these
sources' performance not being fully characterized. Long-term
variability exists due to, among other things, variation over time in
control device performance and varying ash feed rates.\6\ EPA confirmed
in a series of analyses of HWCs that this test-to-test variability for
non-FF equipped devices both exists and is appreciable. See TSD Vol.
III section 16.5 showing among other things that ostensibly lowest
emitting, non-FF equipped sources in other tests (i.e., other occasions
when the same source was tested) were unable to duplicate (i.e.,
achieve): (a) Their own level of performance (i.e., their performance
in the other test), (b) their own performance adjusted to account for
run-to-run variability, (c) floors based on the average of the lowest
single test emitters' performance, (d) design level of the floor
actually adopted in the rule (i.e., the level sources would design to
in order to comply with the rule), and, in one case, (e) the floor
level established in the rule (i.e., the floor reflecting application
of the Air Pollution Control Device methodology). EPA further examined
whether this difference in performance resulted from legitimate
operating variability, rather than from differing ash feed rates, and
in the instance where direct comparison was possible, determined that
it did not. TSD Volume III pp. 16-15 through 17.
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    \6\ Ash content is an indicator of the noncombustible matter
(i.e., inorganic content, including metals) in the feed to the
source.
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    In contrast, EPA was able to quantify the long-term performance
(i.e., performance accounting for both run-to-run and test-to-test
variability) of HWC sources equipped with FFs. This is the only type of
air pollution control device for HWCs, and the only pollutant, for
which such a calculation is possible. The reason this quantification is
possible is that FFs are less variable than other control devices, and
perform relatively constantly regardless of input loadings. 70 FR at
59449. EPA thus developed a so-called Universal Variability Factor
algorithm for fabric filters, which is derived from the quantified
measure of the total variability (i.e., both run-to-run and long-term
test-to-test variability) of the FF-equipped hazardous waste combusters
identified as best performers based on the historical test conditions
for those sources. See TSD Vol. III section 5.3.
    As a result, for HWCs EPA has a considerably more reliable idea of
what fabric filter-equipped sources' actual performance for PM is over
time than for any other type of control device-equipped source (or for
sources without air pollution control devices). Second, as just noted
above, the record demonstrates that the performance data from sources
that emitted less PM in individual performance tests but are not
equipped with FFs significantly underestimates the amount of PM these
sources emit over time (i.e., fails to account for their long-term
variability). Third, over time, these emissions in some instances
exceed (i.e., are higher than) the lowest emitting FF-equipped sources,
even though emitting less in an individual performance test. 70 FR at
59448; TSD Vol. III section 16.5. Putting all this together, EPA
selected the lowest emitting FF-equipped sources as the best
performing. 70 FR at 59448.
    This approach is consistent with the statute and applicable case
law. EPA selected as best performers (or best controlled sources) those
sources it reasonably estimated to have the lowest PM emissions over
time. Performance of units equipped with fabric filters can be reliably
estimated over time--i.e., all of the variability can be quantified.
Performance of other units over time cannot be estimated as reliably
(the long-term variability cannot be quantified at all), but is known
to be less efficient and more variable. Short-term performance tests
thus demonstrably and dramatically understate the amount of PM (and HAP
metal) these sources emit, so that these units could (and demonstrably
do in some instances) emit more PM (and therefore more HAP metal) than
the lowest emitting FF-equipped sources notwithstanding lower PM
emissions in individual tests. The D.C. Circuit has held repeatedly
that EPA may use reasonable means to estimate the performance of best
performing sources, and may account for sources' variability in doing
so. CKRC, 255 F.3d at 865-66; Mossville, 370 F.3d at 1240, 1242;
National Lime Ass'n v. EPA, 627 F. 2d 416, 431 n. 46, 443 (D.C. Cir.
1980); see also Brick MACT, 479 F.3d at 881-82 (estimates of
variability are to be for the variability of the best performing
sources). EPA's approach here is consistent with these requirements.
    The D.C. Circuit has stressed in both Brick MACT and CKRC that
factors such as low HAP feed that influence emissions cannot be ignored
in assessing performance. 479 F.3d at 882-83; 255 F.3d at 864-65. EPA
thus carefully reexamined those instances where low PM emitters in
single tests were not equipped with any pollution control equipment so
that their emission levels necessarily reflected low ash inputs. There
are three incinerators that had lower PM emissions in single tests that
were lower than the worst of the lowest-emitting FF-equipped
incinerators on whose performance the floor standard is based. TSD Vol.
III App. F at APCD-INC-PM. EPA continues to believe that it properly
chose not to include these sources among the pool of best performers.
First, even in single test conditions, these sources' emissions were
not significantly lower (0.0018 to 0.0009 gr/dscf lower, that is,
roughly a 7-14% difference) than the average of the best performing 12%
of sources EPA identified as best performing using the Air Pollution
Control methodology. Id. These sources also emit more PM than all but
one of the best performing incinerators in EPA's pool of best
performers, and the difference in performance between these
uncontrolled sources and the last of the EPA pool is small, roughly a
factor of 2. Id. Since these devices lack any pollution control
equipment, their performance over time will be highly variable as ash
feedrates vary and their emissions could \7\ well exceed the emissions
of the sources comprising EPA's pool of best performing incinerators.
Second, and of at least equal importance, low ash feedrates are not a
guarantee of low HAP metal emissions. Low PM emissions from
uncontrolled sources could still reflect high metal HAP emissions
since, if the ash has high metal content, all of it would be emitted.
See 70 FR at 59449 (``ash feedrates are not reliable indicators of
nonmercury metal HAP feed control levels and are therefore
inappropriate parameters to assess in the MACT evaluation process. For
example, a source could reduce its ash feed input by reducing the
amount of silica in its feedstreams. This would not result in * * *
emission reductions of metal HAP''). In contrast, ``particulate matter
emissions from baghouses [e.g., FF-equipped units] are not
significantly affected by inlet particulate matter

[[Page 54880]]

loadings'', id., so that PM (and hence HAP metal emissions) from these
units will remain best controlled regardless of relative amounts fed to
the device. See also TSD Vol. III section 17.7 documenting that PM
emissions from FF-equipped sources are not affected appreciably by
inlet loadings. EPA is thus giving preference as best performers to
those incinerators we know are effectively controlling non-mercury
metal HAP because they are the lowest emitting of the most efficiently
controlled sources. Moreover, although a severable part of the
rationale, EPA believes it reasonable that most efficiently controlled
sources can be viewed as ``best performing'' and ``best controlled''
under appropriate circumstances. See discussion in section B.1 below.
---------------------------------------------------------------------------

    \7\ There are no comparative test data in the record for these
sources.
---------------------------------------------------------------------------

    EPA does, however, believe that certain parts of the justification
for the PM standards in the final rule are not proper after Brick MACT,
and EPA is no longer relying on them and will revise the record
accordingly. The principal revisions are to discussions relating to how
EPA considered raw material inputs in assessing which sources are best
performers. See Brick MACT, 479 F. 3d at 882-83. The specific
alterations EPA is contemplating (generally excising existing language)
are found in red line/strike out versions of the Preamble, Technical
Support Documents, and Response to Comment Document which EPA has
placed in the docket for this rule.
2. Standards for Liquid Fuel Boilers
    EPA's initial decision is not to defend the PM standard for liquid
fuel boilers (LFBs), and we thus contemplate requesting the Court to
remand the standard so that EPA can reexamine it. Most of the liquid
fuel boilers with lowest PM emissions are uncontrolled units with
extremely low ash feeds. TSD Vol. III App. F at APCD-LFB-PM. Unlike the
situation with incinerators, the difference in PM emissions between
these sources and those lowest-emitting LFBs equipped with FFs is
great, ranging from a factor of 6 (comparing lowest emitting FF-
equipped LFB with lowest emitting uncontrolled LFB) to over three
orders magnitude (comparing worst of the lowest emitting FF-equipped
LFB to lowest emitting uncontrolled LFB). Id. These uncontrolled
sources' emissions are also roughly an order of magnitude lower than
the promulgated floor based on performance of FF-equipped sources. Id.
There are also ten uncontrolled LFBs in the data base with lower PM
emissions than the lowest emitting FF-equipped LFB. Id. Under these
circumstances, EPA is less certain that these LFBs could emit more PM
over time than the FF-equipped sources EPA selected as best performers
and therefore will reexamine the standard with a view to amending it.
However, EPA notes further that this difference in emission levels
between controlled and uncontrolled sources suggests that
subcategorization may be appropriate. EPA intends to investigate that
possibility in subsequent rulemaking.

B. Standards for Semivolatile Metals and Low Volatility Metals

1. Methodology To Establish Floor Levels
    EPA used the so-called system removal efficiency/hazardous waste
feed control (``SRE Feed'') methodology to establish floor levels for
semivolatile metal HAP (``SVM''--lead and cadmium) and low volatile
metal HAP (``LVM''--arsenic, beryllium, and chromium) for all source
categories except hydrochloric acid production furnaces. Under this
methodology, best performers are ranked by hazardous waste feed rate of
metal HAP, and by system removal efficiency (the degree to which HAP
are removed from stack emissions across the entire system, be it by an
air pollution control device or by any other means). 70 FR at 59441.
Best performers are those with the best combination of hazardous waste
feed rate for the HAP at issue and system removal efficiency (i.e.,
lowest hazardous waste feed rate and best removal efficiency). EPA
assessed SVM and LVM separately, so that there are separate pools of
best performing sources for each of these HAP metal groups for each of
the source categories.
    Once best sources are identified by this methodology, EPA
calculated the floor (accounting for run-to-run variability) based on
the averaged emission levels of SVM or LVM from these best performing
sources (or for new sources, the SVM or LVM emission level of the
single best performer). For source categories where SVM and LVM
standards are normalized by hazardous waste heat input (cement kilns,
lightweight aggregate kilns, and the higher heating value hazardous
wastes subcategory for liquid fuel boiler), see 70 FR at 59451-53, the
standard is expressed exclusively in terms of SVM or LVM attributable
to hazardous waste inputs. For all source categories, total SVM and LVM
emissions are addressed and controlled by the PM standard.
    The SRE Feed methodology does not always identify the lowest
emitters of SVM or LVM in single tests as the best performers; it
identifies the lowest emitters as the sources with the best combination
of hazardous feed rate control and back end control (removal efficiency
across the entire system). Some of these sources were also the lowest
emitters in single test results, but were not in all cases. EPA
selected this methodology, rather than the so-called Straight Emissions
approach of simply identifying best performers as those with the lowest
emissions after accounting for run-to-run variability, because the SRE
Feed methodology better identifies who the lowest emitters will be over
time, and better assesses their performance (i.e., how much SVM or LVM
they will emit as they operate). 70 FR at 59441-442; TSD Vol. III at
17-1. SRE Feed best performers are likely to emit less of these metals
over time than sources identified as best under the Straight Emissions
methodology--averaged performance of lowest emitting sources in the
most recent performance test accounting for run-to-run variability (see
TSD Vol. III at section 7.2)--because the Straight Emissions
methodology (even after accounting for run-to-run variability) ignores
sources' long-term (test-to-test) variability, and so underestimates
(indeed, ignores) their performance over time. The SRE Feed methodology
accounts for test-to-test variability, albeit qualitatively. Id.\8\ For
the same reason, the SRE Feed methodology better estimates sources'
performance over time since it accounts in some measure for their long-
term variability instead of ignoring it. As discussed earlier, elements
of long-term variability include such things as chlorine feed rates
(since metals are more volatile in the chlorinated form), back-end
control devices' controllable operating parameters (e.g. ESP power
levels, pressure drop across baghouses, and other such operating
parameters), the matrix in which the metal is fed (solid, liquid,
pumpable) and the hazardous waste feedrate. TSD Vol. III at p. 17-5.
SRE Feed best performers are those that best control these and other
controllable parameters and therefore are less variable (i.e., are more
efficient at controlling SVM and LVM emissions), and therefore likely
to emit less SVM and LVM over time. Id. at p. 17-11. Put more broadly,
the methodology best evaluates the two things sources can do to control
SVM and LVM emissions: limit the feed rate of these HAP in hazardous
waste (since hazardous waste feed rate is controlled under RCRA rules),
and manage

[[Page 54881]]

controllable parameters to limit emissions across the entire system
(both through emission control device control and by any other means),
the result being that these sources are likely to emit less SVM and LVM
over time. 70 FR at 59441.
---------------------------------------------------------------------------

    \8\ See TSD Vol. III at 17-1 to 4 explaining why long-term
variability for SVM and LVM cannot be determined quantitatively,
even for sources equipped with baghouses (FFs).
---------------------------------------------------------------------------

    Data confirm that lowest emitters in single tests (i.e., performers
identified as best under the Straight Emissions methodology) can and do
emit more SVM and LVM over time than the sources EPA identified as best
performers using the SRE Feed methodology. See TSD Vol. III sections
17.2 and 17.3.1 and 17.3.2. Looking at all the data in the record where
there were multiple test results (i.e., tests conducted at different
times) from sources with the lowest SVM or LVM emissions in single
tests, EPA found that a) three of four of these sources emitted more
SVM or LVM in historical tests than allowed under the Straight
Emissions floor (i.e., average emissions (not considering run-to-run
variability) of SVM or LVM were higher than the average of the best
performers using the Straight Emissions methodology (which considers
run-to-run variability)) (id. Table 17-1); \9\ (b) 5 of 15 of these
sources were projected to emit more SVM or LVM than allowed under the
SRE Feed floor using the reasonable assumption that these sources fed
the same amount of LVM and SVM in hazardous waste as they did in the
performance test identifying them as a best performer (lowest emitter)
under the straight emission approach, but had the system removal
efficiency demonstrated in their other tests. Id. at Tables 17-2 and
17-3; \10\ and (c) 8 of 13 straight emission best performers would
exceed the SRE Feed floor if their system removal efficiency from all
tests (i.e., whether the system removal efficiency was higher or lower
than that demonstrated in the single performance test identifying it as
a best performer under the straight emissions methodology) were pooled
and applied to the hazardous waste federate for LVM or SVM used in the
single performance test identifying it as a best performer under the
straight emissions methodology. Id. at 17.3.2 and Tables 17-6 and 7. In
addition, most of the straight emissions best performers emitted more
SVM and LVM in previous performance tests than they did in the single
performance test identifying them as a straight emission best performer
(or were projected to do so under the same reasonable assumptions), and
often exceeded their earlier performance by wide margins (failing
routinely, for example, to achieve their own performance test results
adjusted upward to account for run-to-run variability, the Straight
Emissions approach floor level (which also accounts for run-to-run
variability), and the design level of the SRE Feed floor level). See
TSD Vol. III sections 17.2 and 17.3.1 and 17.3.2.
---------------------------------------------------------------------------

    \9\ It should be noted that source 3016 was feeding more LVM in
this test than in its most recent performance test, although the
source was operating within its permit limits, and so far as can be
determined was also otherwise properly designed and operated in this
test.
    \10\ EPA also showed that these sources were operating properly
in the tests where they removed SVM and LVM less efficiently. TSD
Vol. III at 17-14 to 15 and Tables 17-4 and 5.
---------------------------------------------------------------------------

    EPA's approach is consistent with the statute and with applicable
caselaw. EPA may consider variability in assessing sources'
performance, and it did so here for the evident reason that variability
is an aspect of a source's performance. CKRC, 255 F.3d at 865-66;
Mossville, 370 F.3d at 1242. Here, short-term and long-term variability
(i.e., run-to-run and test-to-test) in SVM and LVM performance
demonstrably exists. The SRE Feed methodology accounts for both types
of variability. The Straight Emissions methodology demonstrably does
not. The Straight Emissions methodology thus not only consistently
underestimates sources' performance, but identifies as best performers
those which may emit more SVM and LVM over time. For these reasons we
believe the record of this rulemaking demonstrates that the SRE Feed
methodology better accounts for variability, and hence performance,
than does the Straight Emissions approach (even with consideration of
run-to-run variability), and consequently, the SRE Feed methodology
more accurately identifies the best performing sources and their level
of performance.
    It is also no answer to say that the Straight Emissions best
performing sources could simply retrofit their devices to achieve over
time what they were able to achieve in a single performance test.
Section 112(d)(3) requires EPA to determine the best performers and
their level of performance based on sources as they now exist, not how
they might be retrofitted. Requiring even the pool of best performers
(i.e., those whose performance was measured at below the average of the
best performers) to retrofit to meet a floor level is a de facto beyond
the floor standard and therefore impermissible unless costs and other
factors under section (d)(2) factors are considered. 70 FR at 59445.
Moreover, a source so retrofitted would not be an existing source as
required by section 112(d)(3), but rather some hypothetical entity
which does not even presently exist. See 71 FR 14665 (March 23, 2006).
    As noted above, the SVM and LVM standards which are normalized by
hazardous waste thermal input apply only to SVM and LVM contributed by
the hazardous waste. MACT standards must address all HAP emitted by a
source, not just some portion of the HAP. Brick MACT, 479 F.3d at 882-
83 (raw material input contributions to HAP emissions must be addressed
by MACT floor). Although most SVM and LVM emitted by these sources
comes from the hazardous waste,\11\ hazardous waste is not the sole
input of these metals. However, all SVM and LVM emissions from these
sources is controlled by virtue of the PM standard. In addition,
although the SVM and LVM floor standards for cement kilns and
lightweight aggregate kilns are normalized by hazardous waste thermal
input, EPA also capped these standards by the interim standards for SVM
and LVM, which are standards that control all SVM and LVM emissions
emitted from the combustor, not just emissions of SVM and LVM from
hazardous waste.\12\ Moreover, there is strong direct correlation
between the control of total PM and control of metal HAP (including SVM
and LVM), so that emission limits reflecting best PM control will also
similarly control the total SVM and LVM. Sierra Club v. EPA (``Primary
Copper MACT''), 353 F.3d 976, 984-85 (D.C. Cir. 2004) (PM proper
surrogate for HAP metals ``even in light of the potential variability
of impurities in copper ore''). Furthermore, as a cross-check, EPA
determined that total SVM and LVM emissions from the sources EPA
identified as the PM best performers from these source categories are
generally comparable to (and often lower than) total SVM and LVM
emissions from the sources identified as best performers under EPA's
SRE Feed methodology.\13\ Thus, on the facts here, the thermally
normalized floors for SVM and LVM (i.e., the SVM and LVM standards for
cement kilns, lightweight aggregate kilns, and the higher heating value
hazardous wastes subcategory of liquid fuel boilers), in combination
with the PM standards, provide control of

[[Page 54882]]

SVM and LVM reflecting the average SVM and LVM emissions of the best
performing sources.
---------------------------------------------------------------------------

    \11\ See Source Data for Hazardous Waste Combustors, Source
Category Summary Sheets, at http://www.epa.gov/epaoswer/hazwaste/combust/finalmact/source.htm
.

    \12\ See 70 FR at 59457-458, Sec.  63.1220(a)(3)(ii),
(a)(4)(ii), (b)(3)(ii), and (b)(4)(ii), and Sec.  63.1221(a)(3)(ii),
(a)(4)(ii), (b)(3)(ii), and (b)(4)(ii).
    \13\ See note from Bob Holloway, USEPA, to Docket ID No. EPA-HQ-
OAR-2004-0022 entitled ``SVM/LVM Emissions from PM Best Performers
Are Generally Comparable to SVM/LVM Emissions from SVM/LVM Best
Performers,'' dated August 23, 2007.
---------------------------------------------------------------------------

    EPA further justified its use of the SRE Feed methodology on two
additional bases, both of which are severable from the analysis just
presented. First, EPA appropriately utilized the SRE Feed methodology
because the Straight Emissions approach would force some best-
controlled commercial hazardous waste treatment units to stop burning
hazardous waste (or to burn less waste), even though hazardous waste
must be treated before it can be land disposed under sections 3004(d),
(e), (g), and (m) of RCRA and combustion is the only means of
successfully treating the hazardous waste. 70 FR at 59442; TSD Vol. III
section 17.4. EPA noted further that the Clean Air Act requires that
EPA take into account RCRA requirements when issuing MACT standards for
hazardous waste combustion units.\14\ CAA section 112(n)(7). Although a
severable part of EPA's rationale, 70 FR at 59447/3, EPA continues to
believe that use of the Straight Emissions methodology is unreasonable
here because it could have significant adverse cross-media
environmental impacts by reducing the amount of needed, and statutorily
mandated hazardous waste treatment capacity. See id. at 59442 (``EPA
doubts that a standard which precludes effective treatment mandated by
a sister environmental statute must be viewed as a type of best
performance under section 112(d)''). EPA's concern here is not that
certain sources are unable to achieve a floor standard. See Brick MACT,
479 F.3d at 881-82. Rather, the concern is the adverse cross-media
environmental impact resulting from undermining ``the heart of RCRA's
hazardous waste management program'', the restrictions on land disposal
of untreated hazardous waste. Chemical Waste Management v. EPA, 976
F.2d 2, 23 (D.C. Cir. 1992). Section 112(n)(7) of the Clean Air Act
requires EPA to consider RCRA standards when adopting section 112(d)
standards for RCRA sources, and EPA's consideration of the issue here
reinforces the conclusion that the SRE Feed methodology is reasonable,
and the proper means here of assessing which sources are best, and
their level of performance, for SVM and LVM emissions.
---------------------------------------------------------------------------

    \14\ EPA investigated the possibility of subcategorizing by
commercial/non-commercial sources but found this undesirable because
it would lead to anomalously high floors for some subcategories due
to sparse available data. 70 FR at 59442 and n. 78.
---------------------------------------------------------------------------

    Second, as a legal matter, section 112(d)(3) does not specifically
address the question of whether ``best performing'' sources are those
with the lowest net emissions, or those which control HAP emissions the
most efficiently. 70 FR at 59443. EPA posited the example of whether a
source emitting 100 units of HAP and feeding 100 units of the HAP must
be considered better performing than a source emitting 101 units of the
HAP but feeding 10,000 units. Id. Indeed, floors for new sources are to
be based on the performance of the ``best controlled'' similar source.
Section 112(d)(3). In the example just given, a source with control
efficiency of 99.9 per cent can naturally be viewed as better
controlled than one with 0 per cent control efficiency. EPA's decision
to incorporate control efficiency (i.e., system removal efficiency)
into the SRE Feed methodology as one of the two factors used to
identify best performing/best controlled sources reasonably reflects
that the statute allows performance to be evaluated in terms of control
efficiency. See further discussion of this issue in the analysis of the
total chlorine emission standard for hydrochloric acid production
furnaces.
    EPA does, however, realize that certain parts of the justification
for the SVM and LVM standards in the final rule may not be consistent
with Brick MACT, and EPA is no longer relying on them. These relate
principally to how MACT standards reflect HAP metal inputs from
variable raw materials. The specific alterations EPA is contemplating
(generally excising existing language) are found in red line/strike out
versions of the Preamble, Technical Support Documents, and Response to
Comment Document which EPA has placed in the docket for this rule.
2. Alternatives to the Particulate Matter Standard for Incinerators,
Liquid Fuel Boilers, and Solid Fuel Boilers
    EPA promulgated alternatives to the PM standard for incinerators,
liquid fuel boilers, and solid fuel boilers.\15\ In the case of liquid
fuel boilers, separate alternatives to the PM standard were finalized
for each subcategory: those burning higher heating value hazardous
wastes and those burning lower heating value hazardous wastes. The
alternative to the PM standard allows sources to comply with standards
limiting emissions of all SVM and LVM metals, including the five
nonenumerated metal HAP not covered by the standards for SVM and LVM,
in lieu of complying with the PM standard. Under these alternatives,
the numerical emission limits for SVM and LVM HAP are identical to the
promulgated standards. However, for SVM, the alternative standard
applies not only to the combined emissions of lead and cadmium, but
also includes selenium, a semivolatile nonenumerated metal HAP; for
LVM, the standard applies to the combined emissions of arsenic,
beryllium, chromium, antimony, cobalt, manganese, and nickel, the
latter four being low volatile nonenumerated metal HAP.
---------------------------------------------------------------------------

    \15\ For incinerators, the alternative to the PM standard are
promulgated Sec. Sec.  63.1206(b)(14) and 63.1219(e). For the higher
and lower heating value hazardous wastes subcategories for the
liquid fuel boiler category, the alternatives are promulgated under
Sec.  63.1217(e)(2) and (e)(3). The alternative to the PM standard
is under Sec.  63.1216(e) for solid fuel boilers.
---------------------------------------------------------------------------

    As noted above, some SVM and LVM standards are normalized by
hazardous waste thermal input and apply only to SVM and LVM contributed
by the hazardous waste. For these standards, SVM and LVM emissions from
nonhazardous waste inputs is controlled by the PM standard. However, if
a source were to elect to comply with the alternative to the PM
standard, then the nonhazardous waste inputs would not be controlled
because, under the alternative, the source would not be required to
comply with a PM standard. In such instances, the alternative to the PM
standard would not address all HAP emitted by a source. This does not
appear to be consistent with the holding of Brick MACT that the
standard must apply to all HAP emitted. 479 F.3d at 882-83. Of the
source categories for which EPA promulgated alternatives to the PM
standard, the higher heating value hazardous wastes subcategory for
liquid fuel boilers is the only category for which SVM and LVM
standards normalized by hazardous waste thermal input were established.
Therefore, EPA believes (subject to comment) that it must reassess the
alternative to the PM standard for this subcategory (and intends to
seek remand of this standard). See Sec.  63.1217(e)(2)(ii) and
(e)(3)(ii).
3. Alternative Mercury, Semivolatile Metals, Low Volatile Metals, and
Total Chlorine Standards for Cement Kilns and Lightweight Aggregate
Kilns
    EPA promulgated provisions that allow cement kilns and lightweight
aggregate kilns to petition the Administrator for alternative mercury,
semivolatile metals, low volatile metals,

[[Page 54883]]

and total chlorine standards.\16\ 64 FR at 52962-967 and 70 FR at
59503-504. Under these provisions, the alternative standard was not
prescribed, and could take the form of an operating requirement, such
as a hazardous waste feedrate limitation of metals and chlorine or an
emission limitation, subject to approval by the Administrator. The rule
discusses two sets of circumstances under which a source could petition
for such an alternative standard. One reason is that the source cannot
achieve the standard due to contributions of metals and chlorine HAP in
the raw materials. The second reason is limited to mercury, and applies
in situations where a source cannot comply with the mercury standard
when mercury is not present in the raw materials at detectable levels
(e.g., the mercury emission standard could be exceeded by a source if
it assumed mercury is present in the raw materials at the detection
limit). These circumstances appear to be inappropriate bases for an
alternative standard after Brick MACT. Accordingly, EPA currently
intends to seek a remand of these alternative metals and total chlorine
standards and remove these provisions in a subsequent rulemaking.
---------------------------------------------------------------------------

    \16\ The alternative standard provisions are promulgated under
Sec.  63.1206(b)(9) for lightweight aggregate kilns and Sec.
63.1206(b)(10) for cement kilns.
---------------------------------------------------------------------------

4. Alternative Mercury Standards for Cement Kilns and Lightweight
Aggregate Kilns Under the Interim Standards
    EPA promulgated an alternative to the interim standards for mercury
for cement and lightweight aggregate kilns in 2002. Section
63.1206(b)(15) and 67 FR 6792 (February 13, 2002). Under this
alternative, sources are allowed to comply with a hazardous waste
maximum theoretical emissions concentration of mercury.\17\ This
alternative mercury standard does not address all mercury emitted by a
source, and, therefore, is not permissible in light of the holding of
Brick MACT that the standard must apply to all HAP emitted. 479 F.3d at
882-83. Accordingly, EPA currently intends to seek a remand of these
alternative standard provisions and remove them in a subsequent
rulemaking.
---------------------------------------------------------------------------

    \17\ Maximum theoretical emissions concentration (MTEC) is a
term to compare metals (and chlorine) feedrates across sources of
different sizes. MTEC is defined as the metals (or chlorine)
feedrate divided by the gas flow rate and is expressed in units of
ug/dscm.
---------------------------------------------------------------------------

C. Standards for Total Chlorine

    EPA established standards for total chlorine (TCl, which controls
emissions of both hydrochloric acid and chlorine) for all of the source
categories. For all of the source categories except HCl production
furnaces, EPA established floors using the SRE Feed methodology
described in the previous section. For HCl production furnaces, EPA
selected sources with the best removal efficiency as the best
performers. EPA believes that most of these standards are consistent
with the statute and applicable caselaw, although certain of the
standards probably are not.
1. Incinerators
    For hazardous waste incinerators, all of the best performers using
the SRE Feed methodology were also the lowest emitters using the
Straight Emissions methodology. Thus, choice of floor methodology is
not at issue here. However, EPA found that the analytic method used to
gather these data is biased below 20 ppmv. 70 FR at 59427-428. EPA's
determination of how to estimate these best performers' level of
performance is explained in detail in 71 FR at 52628-30 (Sept. 6,
2006). As there stated, this determination is consistent with Brick
MACT and all other applicable statutory and caselaw.
2. Cement Kilns
    EPA used the SRE Feed methodology to establish floors for new and
existing sources, but believed that the data did not fully reflect
variability that best performing kilns experience due to fluctuating
alkalinity levels within the kiln. Rather, the TCl emissions data
reflect the alkalinity of the limestone raw material used at the time
of performance tests. 70 FR at 59469-70, TSD Vol. III section 13.7.1.
To account for this variability, EPA assumed a 90 per cent system
removal efficiency for all cement kiln sources. The best performing
sources then effectively become the lowest chlorine feeders. Although
this assumed system removal efficiency has some factual basis, see
Table 1 at 70 FR 59470 showing that the median of the best performing
sources (Ash Grove) demonstrated removal efficiencies ranging from 85.1
to 98.8%, the standard reflects concerns relating to raw material
variability, and also may reflect a level that is achievable (albeit by
best performers) rather than actually achieved. Neither of these
rationales is permissible after Brick MACT, 479 F.3d at 880-81, 882-83.
Accordingly, subject to consideration of comments on this issue, EPA
currently intends to seek a remand on this standard and reexamine it in
a subsequent rulemaking. EPA notes further that the health-based
compliance alternatives for total chlorine under Sec.  63.1215 would
not be affected by this reexamination and thus would provide an
alternative means of demonstrating compliance.
3. Lightweight Aggregate Kilns
    Choice of a floor methodology for TCl is essentially academic for
existing lightweight aggregate kilns, since both the SRE/Feed and
Straight Thermal Emission (and Straight Mass Emission) methodologies
yield floor levels higher than the interim standard for these devices,
in which case the floor level is capped by the level of the interim
standard. 70 FR at 59457; see TSD Vol. III appendices C, D, and E for
data and calculations. The reason for this seeming anomaly in all the
methodologies is that EPA has little data from this source category
(and there are only a few sources to begin with), so that differences
in individual performance runs are magnified when the standard is
calculated. In addition, all of the data in the record came from tests
conducted before EPA adopted the interim standards. This is especially
relevant for this standard because the interim standard is a beyond-
the-floor standard. See generally TSD Vol. III chapter 19. The interim
standard thus remains the best measure of evaluating best performing
sources.
    However, for new sources, EPA noted only that the new source floor
calculated using the SRE Feed methodology would be less stringent than
the interim standard but did not closely examine whether the
methodology clearly identified the best controlled source. TSD Vol. III
section 12.6.3. EPA therefore intends to reexamine this standard in a
subsequent rulemaking, subject to consideration of comment (and to seek
remand of the standard).
4. Liquid Fuel Boilers
    a. Higher Heating Value Hazardous Wastes Subcategory. EPA believes
(subject to comment) that it must reassess this standard (for both new
and existing sources) since the standard applies only to TCl
attributable to hazardous waste inputs, and currently intends to seek
remand of the standard. See Sec.  63.1217(a)(6)(ii). This is not
permissible in light of the holding of Brick MACT that the standard
must apply to all HAP emitted, notwithstanding variable HAP levels in
raw materials. 479 F.3d at 881-82.
    b. Lower Heating Value Hazardous Wastes Subcategory. The SRE Feed
and Straight Emissions methodologies give

[[Page 54884]]

the same floor value for this subcategory, and the standard applies to
all TCl emissions from the boiler, not just those attributable to
hazardous waste. See Sec.  63.1217(a)(6)(i). The issue is how to
account for analytical bias at levels below 20 ppmv, and EPA's
resolution of the issue is explained at 71 FR at 52628-630. EPA does
not believe this approach raises issues under the statue, or under
Brick MACT or other applicable caselaw.
5. Solid Fuel Boilers
    The SRE Feed and Straight Emission methodologies give the same
floor level for both existing and new solid fuel boilers, so the issue
of appropriate floor methodology is academic. TSD Vol. III at App. E
and C.
6. Hydrochloric Acid Production Furnaces
    The TCl standard for this source category controls TCl emissions
and also serves as a surrogate for all metal HAP. TSD Vol. III sections
15.2 and 15.3. EPA selected as best performers sources with the best
TCl system removal efficiency (or, for new sources, the single source
with the best TCl system removal efficiency). The standard is then
expressed as a required degree of control: 99.923 percent for existing
sources (the average efficiency of the five best controlled sources),
99.987 percent for new sources (the control efficiency of the single
best controlled source). Id. section 15.3.
    EPA continues to believe that this standard is consistent with the
statute and applicable caselaw. First, the statutory language requiring
floors to be based on ``best controlled'' (new) /``best performing''
(existing) does not specify whether ``best'' is to be measured on
grounds of control efficiency or emission level. See Sierra Club v.
EPA, 167 F.3d 658, 661 (`` `average emissions limitation achieved by
the best performing 12 percent of units' * * * on its own says nothing
about how the performance of the best units is to be calculated''). The
requirement that the new source floor reflect ``emission control''
achieved in practice reinforces that the standard can be determined and
expressed in terms of control efficiency. Existing floors determined
and expressed in terms of control efficiency are likewise consistent
with the requirement that the floor for existing sources reflect
``average emission limitation achieved'', since ``emission limitation''
includes standards which limit the ``rate'' of emissions on a
continuous basis--exactly what the standards do here. CAA section
302(k). Moreover, where Congress wanted to express performance solely
in terms of numerical limits, rather than performance efficiency, it
said so explicitly. See CAA section 129(a)(4).
    The policy reason for EPA's interpretation here is that a standard
limiting volumetric TCl emissions means that less product is produced,
since these sources recover hydrogen chloride to produce hydrochloric
acid. TSD Vol. III at 15-6; 70 FR at 59450. EPA does not believe that
the MACT floor provisions should compel an otherwise best performing
source to limit the amount of product it produces. See 2 Legislative
History at 3352 (House Report) (``MACT is not intended to * * * drive
sources to the brink of shutdown'').
    Moreover, all that is at issue here is how to express the
performance of sources ranked as best performing under both EPA's
methodology and under the Straight Emissions methodology. This is
because, with one exception, the best performing sources are the same
under EPA's methodology as those identified as best performing under
the Straight Emissions methodology. TSD Vol. III App. C at E-HCLPF-CL
and App. E at SO-HCLPF-CL. The one exception is where EPA chose a
parallel test condition which exhibits more variability to characterize
the source's performance (source 855 condition 11 rather than condition
13), and consequently resulted in this source not being selected as a
best performer. Given this documented variability, this is a reasonable
choice. Thus, EPA is selecting as best performers those with the lowest
measured emissions of chlorine, but chose to express their performance
in terms of system removal efficiency to avoid impacts on amount of
product these best performing sources produce. EPA continues to regard
this choice as reasonable.
    EPA has carefully reexamined this standard in light of Brick MACT.
The opinion does not address the issue directly, since no standard
there was determined or expressed in terms of control efficiency.
Moreover, as noted above, unlike section 129, section 112 contains no
directive to express standards as numerical limits (see section
129(a)(4)), further supporting EPA's view that it could reasonably
choose to express this standard in per cent reduction terms. See also
section 112(i)(5)(A), which allows sources that achieve early
reductions based on measured rates of removal efficiency a reprieve
from MACT, a provision reasonably read to allow section 112(d)
performance to be expressed in terms of rate of removal efficiency.
    The opinion does hold, however, that different HAP levels in raw
materials could not justify a conclusion that floor standards were
unachievable, so that emissions attributable to raw material HAP had to
be accounted for in the standard. 479 F.3d at 882-883. The TCl standard
at issue here accounts for emissions from all HAP inputs, 70 FR at
59450, and so does not present this deficiency. Nor are the floor
standards designed to be achieved by all sources with a specific
emission control technology. 479 F.3d at 880-81. The removal efficiency
standard is not based on performance of any particular technology, and
simply is the averaged (or single best) efficiencies of the best
performing sources (after accounting for run-to-run variability).
    EPA, however, does not (subject to comment) believe that the
alternative standard of 150 ppmv by volume for existing sources
(section 63.1218 (a) (6) (i)) should be retained and EPA currently
intends to seek remand of this alternative standard. The standard
appears inconsistent with the SRE MACT standard, since it allows
sources to operate with less efficient system removals.
    EPA also recognizes that certain parts of the rationale for the
standard, generally related to whether standards are to reflect varying
raw material HAP inputs, do not appear to be consistent with Brick
MACT. EPA is making appropriate revisions to the key record documents,
which are available in red line strike out versions in the
administrative record.

D. Standards for Dioxins/Furans

    Polychlorinated dioxins and furans (D/F, or `dioxins') are
typically not present in any of the inputs to hazardous waste
combustion devices. Rather, they are formed post-combustion (often from
some type of chlorinated precursor, which precursor is itself typically
a product of incomplete combustion). 70 FR at 59461. As combustion
efficiency increases, complex organic molecules which can be D/F
precursors are oxidized to form carbon dioxide or carbon monoxide,
helping to minimize D/F formation and emission. Id. Different levels of
chlorine in waste or other inputs do not appreciably influence D/F
emission rates. TSD Vol. IV \18\ section 3.3 (documenting that D/F
formation and emission is ordinarily not dependent on feed levels of
chlorinated

[[Page 54885]]

materials); TSD Vol. III at 10-6. Nor does burning hazardous waste
generally have an appreciable impact on CDD formation and emissions, so
that it is technically appropriate in some instances to consider D/F
emission levels from sources which do not burn hazardous waste in
evaluating emission potential from those that do. TSD Vol. III at 11-4
and n. 72.
---------------------------------------------------------------------------

    \18\ USEPA, ``Technical Support Document for HWC MACT Standards,
Volume IV: Compliance with the HWC MACT Standards'' (TSD Vol. IV),
September 2005. See docket item EPA-HQ-OAR-2004-0022-0435.
---------------------------------------------------------------------------

    Precise formation and control mechanisms of D/Fs are thought to be
fairly well understood for systems with dry air pollution control
devices (or extensive ductwork containing particulates on surfaces,
such as for certain lightweight aggregate kilns). For these systems, D/
Fs are formed on particles entrained in the control device by surface-
catalyzed reactions where entrained particulate matter provides the
reaction surfaces.\19\ D/F formation can increase exponentially as gas
temperatures increase from 400 [deg]F to 750 [deg]F.\20\ Formation
mechanisms, or their degree, are less well understood for systems with
wet air pollution control or no air pollution control systems, making
it less certain how much D/F these sources may emit over time. TSD Vol.
III pp. 10-5 to 6.
---------------------------------------------------------------------------

    \19\ USEPA, ``Draft Technical Support Document for HWC MACT
Standards, Volume IV: Compliance with the HWC MACT Standards,''
March 2004, Section 3.0.
    \20\ To be clear, the dry air pollution control device does not
control D/F emission (except insofar as some of the formed dioxins/
furans adsorb to particulate which is collected). Rather, the inlet
to these devices serves as an agent for the actual formation of the
chemical, to the availability of a surface catalyzed reaction which
occurs under these conditions.
---------------------------------------------------------------------------

    EPA used the Straight Emissions methodology rather than the SRE
Feed methodology as the starting point for calculating floors for D/F
because dioxins/furans do not come from inputs (but rather are formed
post-combustion), so that it is not possible to calculate system
removal efficiencies (which is calculated from inputs and outputs).
However, for a number of the source categories where best performers do
not have dry air pollution control devices, EPA's professional judgment
was that this methodology did not give an accurate assessment of the
best performing sources' performance over time (i.e., the best
performers' variability). This is because there are myriad factors that
can affect D/F emissions for these sources \21\ and, unlike sources
equipped with a dry emission control device where gas temperature at
the inlet to the control device is generally the dominant factor
affecting D/F emissions),\22\ there is no generic, dominant factor
affecting emissions. In these instances, EPA consequently selected as
best performers those sources which best minimized the formation of
dioxin precursors by maintaining the most efficient combustion
conditions, as measured by carbon monoxide (CO) or total hydrocarbon
emissions (HC), as well as by destruction/removal of hardest-to-burn
hazardous waste constituents at an efficiency of 99.99 percent. The
floor standards for these sources consequently is either meeting a CO
standard of 100 ppmv or an HC standard of 10 ppmv, plus demonstrating a
destruction/removal efficiency (DRE) of 99.99 percent on the hardest-
to-combust hazardous constituents present in the hazardous waste. In
instances where the interim standard applied to such sources, EPA used
that standard as the measure of best performers' good combustion
instead of quantified CO/HC and destruction/removal efficiency.
---------------------------------------------------------------------------

    \21\ Factors that can affect D/F emissions from sources with a
wet control device or no control device include: Soot buildup on
boiler tubes and presence of metals in the feed that can catalyze D/
F formation reactions. 70 FR at 59502.
    \22\ For sources with dry emission control devices, D/F
emissions during the compliance tests EPA used to characterize
emissions would generally be at the upper end of the range of normal
operations. Because an operating limit is established on gas
temperature at the inlet to the control device based on levels
achieved during the compliance test, operators had the incentive to
maximize gas temperatures while still complying with the D/F
emission standard under part 266, subpart H (Sec.  266.104(e)).
---------------------------------------------------------------------------

    Our assessment of these standards, subject to comment, is:
1. Incinerators
    a. Dry Air Pollution Control Device Subcategory.\23\ EPA used the
Straight Emissions approach to establish floor levels for existing and
new sources for this subcategory. The existing source floor, calculated
in this manner, was slightly higher than the interim standard, so the
floor is capped at the level of the interim standard. TSD Vol. III p.
10-4. The standard for new sources is based on the performance of the
single lowest emitting source. Id. at 10-11. EPA believes this standard
to be consistent with the statute and all applicable caselaw.
---------------------------------------------------------------------------

    \23\ EPA explained a number of times that it did not
subcategorize incinerators by control device. Rather, the presence
or absence of a dry air pollution device relates to differences in
dioxin formation mechanisms and consequent dioxin emission levels.
See e.g. 70 FR at 59467.
---------------------------------------------------------------------------

    b. Incinerators with Wet Air Pollution Control Systems or No Air
Pollution Control Systems. For both new and existing sources, EPA
selected the interim standard as the floor standard. Id. at 10-6 and
10-11. EPA considered basing the floor on the performance of lowest
emitters in single tests, but these sources had strikingly varied
results in other tests, with one `best' performer (source 3016) having
emissions over 1000 times greater than its previous test, and well in
excess of the floor level established by EPA. TSD Vol. III at 10-6.\24\
Under these circumstances, EPA was unable to conclude that single test
results adequately represented the sources' performance over time
(i.e., their long term variability). TSD Vol. III at 10-6 (lowest
emitters in single tests would prove unable to duplicate their
performance in other tests due to their variability). Without a means
to assess long-term performance, EPA used the interim standard as the
measure of best performers' performance over time. Id. EPA continues to
believe that this is a reasonable estimate of best performance, and
that the standards are consistent with the statute and applicable
caselaw.
---------------------------------------------------------------------------

    \24\ See also Note from Bob Holloway, USEPA, to Docket ID No.
EPA-HQ-OAR-2004-0022 entitled ``Incinerators: Comparison of D/F
Emissions Variability for Best Performers and Other Sources with Wet
or No APCD,'' dated April 5, 2007.
---------------------------------------------------------------------------

2. Cement Kilns
    The calculated floor for existing cement kilns using the straight
emissions approach was slightly higher (less stringent) than the low
end of the interim standard (0.28 as opposed to 0.20 ng TEQ/dscm).
However, available historical D/F emissions data for cement kiln best
performers (other test conditions conducted at different times from
cement kiln sources identified as best performing, which test
conditions reflect temperature optimization) show that these sources
performance considering run-to-run variability exceeded both the floor
level calculated using the Straight Emissions methodology and the
interim standard.\25\ In light of this documented variability, EPA
considered the interim standard the more stringent and consequently
used the interim standard (0.20 ng TEQ/dscm or 0.40 ng TEQ/dscm and a
temperature of 400 [deg]F or less at the inlet of the dry air pollution
control device) as the floor. The calculated floor for new cement kilns
using the straight emissions approach was slightly higher (less
stringent) than one part of the interim standard for new cement kilns
(0.21 ng TEQ/dscm as opposed to 0.20 ng TEQ/dscm), and in addition, the
lowest emitter in a single test condition (source 323B3) exhibited
enormous variability in other

[[Page 54886]]

performance tests (see test condition 323C1; the other lowest emitters
likewise showed significant variability in other tests (id.)) so EPA
adopted the level of the interim standard as the MACT floor for new
sources. TSD Vol. III p. 11-7. EPA believes that these standards are
consistent with the statute and applicable caselaw.
---------------------------------------------------------------------------

    \25\ See data for test conditions 228C4, 403C4, and 404C3 in
Note from Frank Behan, USEPA, to Docket ID No. EPA-HQ-OAR-2004-0022
entitled ``Comparative D/F Data for the Cement Kiln Best
Performers,'' dated August 23, 2007.
---------------------------------------------------------------------------

3. Lightweight Aggregate Kilns
    The calculated floors for existing and new lightweight aggregate
kilns using the Straight Emissions approach were higher (less
stringent) than the interim standard, so EPA adopted the level of the
interim standard as the MACT floor for both existing and new sources.
TSD Vol. III pp. 12-4 and 12-6. EPA continues to believe that this
approach uses the best measure of evaluating the best sources and their
level of performance, and that these standards are consistent with the
statute and applicable caselaw.
4. Liquid Fuel Boilers
    a. Sources with Dry Air Pollution Control Devices. EPA used the
Straight Emissions approach to establish a floor for existing liquid
fuel boilers equipped with a dry air pollution control device, which
yielded an extremely high standard of 3.3 ng TEQ/dscm.\26\ TSD Vol. III
p. 13-7. The floor standard also includes an alternative based on
meeting temperature control of 400[deg] F at the inlet to the dry air
pollution control device. Id. EPA also adopted a beyond-the-floor
standard for these sources which is (necessarily) more stringent than
the level of the floor. Id. at 13-8. This beyond the floor standard
would be ascertained identically whether or not the existing source
floor included the temperature control alternative. EPA believes that
this standard is consistent with section 112 (d) (2) of the statute,
and that the floor is also consistent with the statute, but not of
direct relevance given that the actual standard is beyond-the-floor.
---------------------------------------------------------------------------

    \26\ The basis for subcategorizing in this way is the same as
for incinerators.
---------------------------------------------------------------------------

    For new sources, EPA adopted a floor standard of the lowest
emitters' performance, or meeting temperature control of 400[deg] F or
less at the inlet to the dry air pollution control device. Subject to
comment, EPA does not believe that this standard accounts for all the
factors that could influence dioxin emissions from new sources, see
Brick MACT, 479 F.3d at 881-82, and therefore intends to seek a remand
of the standard and further examine it in a subsequent rulemaking.
    EPA also recognizes that not all of the rationale adopted for these
standards is consistent with Brick MACT, particularly discussions
relating to whether sources other than those in the best performing
half of the MACT pool of best performers could replicate best
performers' level of performance. EPA has made appropriate edits to the
key support documents which are available for comment in red line
strikeout form in the administrative record.
    b. Sources with Wet or Without Air Pollution Control Equipment. EPA
has decided (subject to comment) not to defend most of the dioxin
standards for sources with wet air pollution control equipment or
without air pollution control equipment.\27\ These include the
standards for liquid fuel boilers with wet or no air pollution control
systems and standards for hydrochloric acid production furnaces. EPA
continues to adhere to its analysis that these sources experience
enormous operating variability based on dioxin formation and control
mechanisms which are uncertain and presently not quantifiable. However,
based on the discussion at 70 FR 59202/2, EPA does not believe that it
is certain that the promulgated standard based on quantified good
combustion addresses all of the potential formation and control
mechanisms for dioxins as required. See Brick MACT, 479 F.3d at 882-83;
CKRC, 255 F.3d at 862-63. Moreover, the cited preamble discussion
suggests that additional dioxin formation and control mechanisms can be
quantified directionally, if not with exactitude. This again may not be
consistent with Brick MACT, 479 F.3d at 883 (lack of data resulting in
inability to quantify variability related to non-technology factors
does not by itself justify by itself a less stringent floor standard).
EPA intends to seek a remand (subject to consideration of public
comment) and to investigate these issues further in subsequent
rulemaking.
---------------------------------------------------------------------------

    \27\ For the same reasons, we will not defend the dioxin
standards for solid fuel boilers.
---------------------------------------------------------------------------

E. Non-Dioxin Organic HAP

    Hazardous wastes contain non-dioxin organic HAP which are destroyed
by effective combustion. Treatment of hazardous waste by destruction of
organics is indeed the chief reason that there is a hazardous waste
combustion industry. See 40 CFR 268.42. (RCRA treatment standards for
organic hazardous wastes, reflecting application of Best Demonstrated
Available Technology (see Hazardous Waste Treatment Council v. EPA, 886
F.2d 355, 363-64 (D.C. Cir. 1989)), are invariably based on performance
of combustion technology.) EPA adopted standards quantifying good
combustion conditions for non-dioxin organic HAP emitted by liquid fuel
boilers, solid fuel boilers, and hydrochloric acid production furnaces.
The floor standards for these sources is either meeting a CO standard
of 100 ppmv or an HC standard of 10 ppmv, plus demonstrating a
destruction/removal efficiency (DRE) of 99.99 percent on the hardest-
to-combust hazardous constituents present in the hazardous waste. In
the event a source chooses to comply with the 100 ppmv CO standard, it
must also demonstrate that it is achieving 10 ppmv HC standard in a
single performance test, and establish continuously monitored
parameters reflecting the conditions of that performance test
(including operating temperature, maximum feed rates, minimum
combustion zone residence time, and operating requirements on the
hazardous waste firing system that optimize liquid waste atomization
efficiency). Sections 63.1216(a)(5), 63.1217(a)(5), and 63.1218(a)(5).
    The basis for these standards is that good combustion, as measured
by 100 ppmv CO or 10 ppmv HC, plus meeting 99.99 percent DRE, is the
best measure of the performance over time of best performers. However,
in contrast to dioxin, EPA has more knowledge of formation mechanisms
and means of control over time. Non-dioxin organics (of which there are
over 100 on the list of HAP) can be present in hazardous waste (or
other inputs) or can be formed as products of incomplete combustion.
Organics are destroyed when wastes are combusted, and best performers
are those which destroy organics through the most efficient combustion.
70 FR at 59463; see also Horsehead Resource Development v. Browner, 16
F.3d 1246, 1265 (D.C. Cir. 1994) (``A kiln's utility as a means of
destroying hazardous wastes turns on its ability to fully destroy them.
In practice, destruction of hazardous wastes in the fuel is a function
of the combustion efficiency of the kiln: Under poor conditions of
efficiency, the principal organic hazardous constituents * * * of the
toxic organic compounds contained in the hazardous waste fuel will be
only partially broken down, thereby increasing the production of
[products of incomplete combustion]'').
    Furthermore, 100 ppmv CO or 10 ppmv HC are long-recognized levels
representing good combustion conditions. 70 FR 59463-464 (explaining
further that lower levels are unlikely to be associated with good
combustion and so no longer serve as a

[[Page 54887]]

measure of organic destruction). EPA adopted these levels here as the
best measure of the sources' long-term performance (and reiterates that
finding here). Id. and TSD Vol. III at 13-35, 14-26, and 15-9. In
addition to good combustion being the long-recognized metric for
organic destruction and performance, EPA lacked any data on individual
organic HAP emissions from these devices, so had no choice but to use
some type of surrogate to evaluate sources' performance.
    EPA views these standards as consistent with the statute and
applicable caselaw. Regarding use of the quantified good combustion
surrogate, the D.C. Circuit has held repeatedly that EPA may select a
surrogate for control of HAP in adopting section 112(d) standards. See,
e.g. National Lime Ass'n v. EPA, 233 F.3d 625, 639 (D.C. Cir. 2000);
Sierra Club v. EPA (``Primary Copper MACT''), 353 F.3d 976, 984-85
(D.C. Cir. 2004). EPA has shown here a valid basis for choosing good
combustion as a surrogate: There is a strong correlation between
optimized combustion conditions and minimized organic emissions in that
oxidation of heavier, more complex organic molecules will be maximized
when combustion conditions are optimized, thus minimizing emission of
organics. 70 FR at 59463; see also id. at 59461-62; see also National
Lime, 233 F.3d at 639 (upholding EPA's selection of PM as a surrogate
for HAP metals where EPA demonstrated a correlation between removal of
PM and metal HAP, and further holding both that EPA need not quantify
the precise amount of metal HAP removed, and that the amount of HAP
metal removed may vary); Primary Copper MACT, 353 F.3d at 984. EPA has
further demonstrated the reasonableness of 100 ppmv CO or 10 ppmv HC as
measures of good combustion.
    National Lime further indicates (in dicta) that choice of a
surrogate may not be valid if emissions of the HAP could increase by
some mechanism for which the surrogate fails to account, specifically
noting that if HAP metal feedrates decreased and PM emissions did not
decrease proportionately, PM might not be a valid surrogate. 233 F.3d
at 639. This discussion has no direct factual applicability here since
organic emissions are not input dependent. See also Primary Copper
MACT, 353 F.3d at 985 (rejecting argument that input variability made
PM an arbitrary surrogate for metals). The situation here is similar to
that in Mossville, where the court held that EPA could account for best
performers' performance over time, and could estimate performance over
time by some means other than emission levels. 370 F.3d at 1242. The
difference here is that EPA is using a quantified surrogate to do so,
but EPA believes this is a difference without legal significance given
the reasonableness of the surrogate on the facts presented here.
Indeed, EPA selected here an existing regulatory standard as a measure
of best performers' performance over time (RCRA standards for CO/HC and
DRE), just as in Mossville EPA selected the existing uniform vinyl
chloride regulatory standard as that measure. 370 F.3d at 1240.\28\
---------------------------------------------------------------------------

    \28\ Brick MACT holds that EPA may not select floor standards to
assure that all sources in the category will be able to meet the
standards. 479 F.3d at 880-81. EPA did not do so here. The CO/HC and
DRE standards are EPA's best estimate of best performers'
performance over time. As in Mossville, EPA selected an existing
regulatory limit not because all sources were (by definition)
meeting that regulatory limit, but because no other means of
accurately assessing variability were available. 370 F.3d at 1240.
Moreover, sources will establish parametric monitoring conditions,
which will vary by source, as part of the process of meeting the 10
ppmv HC standard, so the standards in fact are not uniform across
the source category.
---------------------------------------------------------------------------

    One commenter maintained that CO/HC standards should be numerically
lower to reflect lowest CO/HC emissions, and further maintained that CO
and HC are not the sole measures of organic combustion efficiency,
which, as EPA noted, can be influenced by such factors as inadequate
time, temperature and turbulence within individual combustion zones,
and, the argument goes, are therefore improper or inadequate
surrogates. 70 FR at 59463/2; cf. National Lime, 233 F.3d at 639. EPA
addressed these issues in the record. 70 FR at 59462-63. With respect
to the level for CO/HC, extremely low CO floors are unlikely to be met
at all times by best performers due to all the potential minor sources
of variability. So the 100 ppmv standard--which must be met
continuously (and is measured by a continuous emission monitor), is the
best measure of best performers' variability and hence performance over
time. TSD Vol. III at 13-35, 14-26 and 15-9 (best sources' inability to
duplicate a lower level of performance at all times for these reasons);
see also Mossville, 370 F.3d at 1242 (if floor standard must be met
continuously, then the best performers' maximum variability must be
reflected in that standard). Of equal importance, lower levels of
either CO or HC are no longer likely to be associated with increased
organic destruction efficiency. 70 FR at 59462-64 (CO itself is a
conservative indicator of combustion efficiency because it is a
thermally stable, refractory compound which is the final stage of the
combustion process of an organic molecule, and levels lower than 100
ppmv are no longer reliably associated with levels of organic HAP).
Finally, the factors mentioned by the commenter which can influence
organic destruction are in fact encompassed within the CO and HC
standards because, as EPA explained, sources must conduct a performance
test for HC and DRE, and continuously monitored parameters, including
minimum operating temperature, maximum feed rates, minimum combustion
zone residence time, and operating requirements on hazardous waste
firing systems (i.e., all of the factors mentioned by the commenter),
are established based on the conditions established in that performance
test. 70 FR at 59464/1. EPA consequently views all of these standards
as consistent with Brick MACT and the statute.
    Edited versions of the key support documents for this standard,
edited to reflect changes necessary in light of Brick MACT, are
available in red line strike out format for comment in the
administrative record.

F. Mercury

1. Incinerators
    For existing incinerators, both the SRE/Feed methodologies and
straight emissions methodologies (even without calculation of run-to-
run variability) produced floors which were higher than the interim
standard. TSD Vol. III appendices C and E, tables E-INC-HG CT and SF-
INC-HG, respectively. EPA's decision to use the interim standard as the
level of the floor consequently does not raise issues vis-[aacute]-vis
Brick MACT. See also Mossville, 370 F.3d at 1241-42 (selection of
regulatory standard as floor is a legitimate means of assessing best
performers' variability when these performers demonstrably emit at a
level close to that regulatory level).
    For new incinerators, EPA selected the emission level of the lowest
emitting source since the same source was the lowest emitter under both
the SRE methodology and the Straight Emissions methodology, TSD Vol.
III appendices C and E, tables E-INC-HG CT and SF-INC-HG, respectively,
again raising no issues vis-[aacute]-vis Brick MACT.
2. Cement Kilns
    For both new and existing cement kilns, the mercury floor standard
appears inconsistent with the Brick MACT opinion and the statute
because it is based in whole or in substantial part on emissions
attributable exclusively to hazardous waste control. The standard thus
does not result in control of all mercury which could be

[[Page 54888]]

emitted by cement kilns (mercury in raw materials being the notable
example), and so appears to require revision. 479 F.3d at 882-83.
Subject to comment, it is thus EPA's intent to amend this standard and
to seek remand of the standard.
3. Lightweight Aggregate Kilns
    The methodology for developing floor standards for mercury for
lightweight aggregate kilns is essentially a Straight Emissions
approach for mercury contributed by hazardous waste.\29\ The floor
calculated thereby produced existing and new source floors higher than
the interim standard of 120 [mu]g/dscm total mercury emissions (110
[mu]g/dscm for new sources), which EPA therefore adopted as the floor
standard. TSD Vol. III at 12-8 to 9, 12-12 and section 7.2.3.5. EPA
continues to believe that the interim standard remains the best measure
of best sources' performance given the available data. However, the
interim standard contains a compliance option based solely upon mercury
emissions attributable to hazardous waste. Section 63.1206(b)(15).
Subject to comment, this alternative compliance mechanism appears to be
inconsistent with Brick MACT since it would not control all mercury
emitted by the kiln. 479 F.3d at 882-83; see also section III.B.3
above. Subject to consideration of public comment, EPA intends to seek
a remand of this alternative standard and to consider this issue
further in subsequent rulemaking.
---------------------------------------------------------------------------

    \29\ EPA used the Straight Emissions approach here for data-
specific reasons explained at section 7.5.3.2 of Volume III of the
TSD.
---------------------------------------------------------------------------

4. Liquid Fuel Boilers
    a. Higher Heating Value Hazardous Wastes Subcategory. The mercury
floor standard for this subcategory for both existing and new sources
accounts only for mercury emissions from hazardous waste. TSD Vol. III
pp. 13-14 and 13-16. These standards thus appear to require revision,
and EPA accordingly currently expects to seek remand of this standard.
Brick MACT, 479 F.3d at 882-83.
    b. Lower Heating Value Hazardous Wastes Subcategory. The mercury
floor standard for this subcategory for both existing and new sources
is based on the Straight Emissions methodology. TSD Vol. III at 13-16
and 13-18; see also 69 FR 21286-87 (because so many of the data
measurements were non-detects, EPA was unable to calculate removal
efficiencies, and so did not use the SRE Feed methodology). The
standard also applies to all mercury emitted by the source, not just
that attributable to hazardous waste. Section 63.1217(a)(2)(i). EPA
does not believe that this approach creates any issues vis-[aacute]-vis
Brick MACT.
5. Solid Fuel Boilers
    EPA used the SRE Feed methodology to identify best sources and
their level of performance for both new and existing solid fuel
boilers. TSD Vol. III at 14-7, 14-9. The floor standards are identical
to those using the Straight Emissions methodology because the best
performing sources (and single best performing source) are the same
under either methodology. TSD Vol. III at App. C (E-SFB-HG-CT) and E
(SF-SFB-HG). EPA does not believe that these standards pose issues vis-
[aacute]-vis Brick MACT.

G. Normalization

    A number of the standards are ``normalized,'' that is expressed as
a given amount of pollutant per amount of some production related
parameter such as air flow or thermal inputs. See generally 70 FR at
59451. Most technology-based standards are expressed in terms of some
type of normalizing parameter in order to allow meaningful comparison
between performance of different sources. Weyerhaeuser v. Costle, 590
F.2d 1011, 1059 (D.C. Cir. 1978). As EPA pointed out, comparing
unnormalized performance is like asking which baseball pitcher is the
better performer, the one who has given up 6 earned runs or the one who
has given up 20. Unless and until the figure is normalized over 9
innings pitched, the question is meaningless. 70 FR at 59451 n. 101.
    EPA sees nothing in the statute which precludes use of
normalization in determining who best performers are for purposes of
MACT floor determinations. Section 112(d)(3) does not specifically
address the issue (the terms ``best performing'' and ``best
controlled'' being amenable to an interpretation allowing comparisons
of normalized emissions to assess which source is ``better'' or
``best''). The issue of normalization was not presented in Brick MACT,
so that EPA likewise does not view the opinion as precluding the
approach.

H. Potential Implications to the Compliance Date Provisions if
Standards Are Remanded to EPA

    The compliance date of the final rule is October 14, 2008. As
discussed above, we are contemplating requesting the Court to remand
several standards so that we can reexamine them in a future rulemaking,
a process that likely would be concluded well after the compliance date
of the rule. It is not our intent to ask the Court to vacate any
standards, including those standards that may have to be revised in a
future rulemaking. As a result, sources would need to comply with the
standards promulgated in October 2005 according to the compliance date
provisions codified under Sec.  63.1206(a). See NRDC v. EPA, 489 F.3d
1364, 1373-74 (D.C. Cir. 2007).

List of Subjects in 40 CFR Part 63

    Environmental protection, Air pollution control, Hazardous
substances, Reporting and recordkeeping requirements.

    Dated: September 21, 2007.
Stephen L. Johnson,
Administrator.
[FR Doc. E7-19097 Filed 9-26-07; 8:45 am]

BILLING CODE 6560-50-P
