[Federal Register: October 28, 2008 (Volume 73, Number 209)]
[Rules and Regulations]
[Page 64067-64097]
[DOCID:fr28oc08-13]

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Part III

Environmental Protection Agency

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40 CFR Part 63

NESHAP: National Emission Standards for Hazardous Air Pollutants:
Standards for Hazardous Waste Combustors: Reconsideration; Final Rule

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2004-0022; FRL-8733-1]
RIN 2050-AG35

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

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule; reconsideration.

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SUMMARY: On October 12, 2005, EPA promulgated national emission
standards for hazardous air pollutants (NESHAP) for new and existing
sources at hazardous waste combustion facilities (the final rule).
Subsequently, the Administrator received four petitions for
reconsideration of the final rule. On March 23, 2006 and September 6,
2006, EPA granted reconsideration with respect to eight issues raised
by the petitions. After evaluating public comments submitted in
response to these reconsideration notices, we are taking final action
regarding the eight issues raised in the petitions for reconsideration.
EPA also re-opened the rule to consider comments relating to a post-
promulgation decision of the United States Court of Appeals for the
District of Columbia Circuit, and is responding in this proceeding to
the comments received on that notice, published on September 27, 2007.
As a result of this reconsideration process, we are revising the new
source standard for particulate matter for cement kilns and for
incinerators that burn hazardous waste. We are also making amendments
to the particulate matter detection system provisions and revisions to
the health-based compliance alternative for total chlorine of the final
rule. Finally, we are also issuing several corrections and
clarifications to the final rule.

DATES: The final rule is effective on October 28, 2008.

ADDRESSES: EPA has established a docket for this action under Docket ID
No. EPA-HQ-OAR-2004-0022. All documents in the docket are listed on the
http://www.regulations.gov Web site. 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, is not placed on the Internet
and will be publicly available only in hard copy form. Publicly
available docket materials are available either electronically through
http://www.regulations.gov or in hard copy at the HQ EPA Docket Center,
Docket ID No. EPA-HQ-OAR-2004-0022, EPA West Building, Room 3334, 1301
Constitution Ave., NW., Washington, DC 20004. This Docket Facility is
open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding
legal holidays. The HQ EPA Docket Center telephone number is (202) 566-
1742. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m.,
Monday through Friday, excluding legal holidays. The telephone number
for the Public Reading Room is<PHONE_NUMBER>. A reasonable fee may be
charged for copying docket materials.

FOR FURTHER INFORMATION CONTACT: For more information on this final
rule, contact Frank Behan at<PHONE_NUMBER>, or<EMAIL_ADDRESS>
Office of Solid Waste (MC: 5302P), U.S. Environmental Protection
Agency, 1200 Pennsylvania Ave., NW., Washington, DC 20460.

SUPPLEMENTARY INFORMATION:
    Outline. The SUPPLEMENTARY INFORMATION in this preamble is
organized as follows:

I. General Information
    A. Does this action apply to me?
    B. Where can I get a copy of this document?
    C. Judicial Review
II. Background
    A. What Is the Source of Authority for the Reconsideration
Action?
    B. What Is the Background on the NESHAP for Hazardous Waste
Combustors?
III. Final Action on Issues for Which EPA Granted Reconsideration
    A. Subcategorization of Liquid Fuel Boilers by Heating Value
    B. Correcting Total Chlorine (TCl) Data to 20 ppmv
    C. Use of PS-11 and Procedure 2 as Guidance for Extrapolating
the Alarm Set-Point of a Particulate Matter Detection System (PMDS)
    D. Tie-Breaking Procedure for New Source Standards
    E. New Source Particulate Matter Standard for New Cement Kilns
    F. Beyond-the-Floor Analyses To Consider Multiple HAP That Are
Similarly Controlled
    G. Dioxin/Furan Standard for Incinerators With Dry Air Pollution
Control Devices
    H. Provisions of the Health-Based Compliance Alternative
IV. Response to Comments to the September 27, 2007 Notice
    A. Standards for Particulate Matter
    B. Standards for Semivolatile Metals and Low Volatile Metals
    C. Standards for Total Chlorine
    D. Standards for Dioxins/Furans
    E. Standards for Non-Dioxin/Furan Organic HAP
    F. Standards for Mercury
    G. Normalization
V. What Other Rule Provisions Are Being Amended or Clarified?
    A. What corrections are we making?
    B. Clarification of the PM Standard for Cement Kilns
VI. Summary of Environmental, Energy, and Economic Impacts
    A. What facilities are affected by the final amendments?
    B. What are the air quality impacts?
    C. What are the water quality, solid waste, energy, cost and
economic impacts?
VII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations
    K. Congressional Review

I. General Information

A. Does this action apply to me?

    The regulated categories and entities affected by this final action
include:

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                                    NAICS code    Potentially affected
             Category                   a               entities
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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.
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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. To determine whether your facility is affected by this action,
you should examine the applicability criteria in 40 CFR 63.1200, ``Who
is subject to these regulations?''. If you have any questions regarding
the applicability of this action to a particular entity, consult either
the air permit authority for the entity or your EPA regional
representative as listed in Sec.  63.13 of the General Provisions to
part 63 (40 CFR part 63, subpart A).

B. Where can I get a copy of this document?

    In addition to being available in the docket, an electronic copy of
this final action will also be available on the Worldwide Web (WWW)
through the Technology Transfer Network (TTN). Following signature, a
copy of the final action will be posted on the TTN's policy and
guidance page for newly proposed or promulgated rules at the following
address: http://www.epa.gov/ttn/oarpg/. The TTN provides information
and technology exchange in various areas of air pollution control. This
action is also available at the following address: http://www.epa.gov/
hwcmact.

C. Judicial Review

    Under section 307(b)(1) of the Clean Air Act (CAA), judicial review
of this final rule is available only by filing a petition for review in
the U.S. Court of Appeals for the District of Columbia Circuit by
December 29, 2008. Under section 307(d)(7)(B) of the CAA, only an
objection to these final rules that was raised with reasonable
specificity during the period for public comment can be raised during
judicial review. This section also provides a mechanism for EPA to
convene a proceeding for reconsideration, ``[i]f the person raising an
objection can demonstrate to EPA that it was impracticable to raise
such objection within [the period for public comment] or if the grounds
for such objection arose after the period for public comment (but
within the time specified for judicial review) and if such objection is
of central relevance to the outcome of this rule.'' Any person seeking
to make such a demonstration to us should submit a Petition for
Reconsideration to the Office of the Administrator, Environmental
Protection Agency, Room 3000, Ariel Rios Building, 1200 Pennsylvania
Ave., NW., Washington, DC 20004, with a copy to the person listed in
the preceding FOR FURTHER INFORMATION CONTACT section, and the
Associate General Counsel for the Air and Radiation Law Office, Office
of General Counsel (Mail Code 2344A), Environmental Protection Agency,
1200 Pennsylvania Ave., NW., Washington, DC 20004. Moreover, under
section 307(b)(2) of the CAA, the requirements established by these
final rules may not be challenged separately in any civil or criminal
proceedings brought by EPA to enforce these requirements.

II. Background

A. What Is the Source of Authority for the Reconsideration Action?

    EPA is reconsidering several aspects of its final rule for
hazardous waste combustors under sections 112(d) and 307(d)(7)(B) of
the Clean Air Act (CAA) as amended (42 U.S.C. 7412(d) and
7607(d)(7)(B)). This action is also subject to section 307(d) of the
CAA (42 U.S.C. 7607(d)).

B. What Is the Background on the NESHAP for Hazardous Waste Combustors?

    Section 112 of the CAA requires that we establish NESHAP for the
control of hazardous air pollutants (HAP) from both new and existing
major sources. Major sources of HAP are those stationary sources or
groups of stationary sources that are located within a contiguous area
under common control that emit or have the potential to emit
considering controls, in the aggregate, 10 tons per year (tpy) or more
of any one HAP or 25 tpy or more of any combination of HAP. For major
sources, the CAA requires the NESHAP to reflect the maximum degree of
reduction in emissions of HAP that is achievable.\1\ This level of
control is commonly referred to as MACT (for Maximum Achievable Control
Technology). See CAA section 112(d)(2).
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    \1\ Section 112(d)(4) gives the Administrator the authority to
establish health-based emission standards in lieu of the MACT
standards for HAP for which a health threshold has been established.
In the final rule promulgated on October 12, 2005, EPA established
health-based compliance alternatives for total chlorine as an
alternative to the MACT technology-based emission standards, which
alternative standards are applicable to all hazardous waste
combustors, with the exception of hydrochloric acid production
furnaces. 70 FR at 59478-486.
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    The minimum control level for major sources is defined under
section 112(d)(3) of the CAA, and is referred to, informally, as ``the
MACT floor.'' The MACT floor ensures that the standards are set at a
level that assures that all major sources perform at the level of
control at least as stringent as that already achieved by the best-
performing sources in each source category or subcategory.
Specifically, for new major sources, the MACT floor cannot be less
stringent than the emission control that is achieved in practice by the
best-controlled similar source. The MACT standards for existing major
sources can be less stringent than standards for new sources, but they
cannot be less stringent than the average emission limitation achieved
by the best-performing 12 percent of existing sources in the category
or subcategory for which the Administrator has emissions information
(where there are 30 or more sources in a category or subcategory;
floors for existing sources in categories or subcategories with fewer
than 30 sources are to be based on the average emission limitation
achieved by the best performing five sources).
    EPA also must consider more stringent ``beyond-the-floor'' control
options. When considering beyond-the-floor options, EPA must consider
not only the maximum degree of reduction in emissions of HAP, but must
take into account costs, energy, and non-air quality health
environmental impacts. See CAA section 112(d)(2).
    We proposed NESHAP for hazardous waste combustors on April 20, 2004
(69 FR 21198), and we published the final rule on October 12, 2005 (70
FR 59402). The hazardous waste combustor NESHAP is codified in subpart
EEE of 40 CFR part 63. Following promulgation of the hazardous waste
combustor final rule, the Administrator received four petitions for
reconsideration, pursuant to section 307(d)(7)(B) of the CAA, from Ash
Grove Cement Company, the Cement Kiln Recycling Coalition (CKRC), the
Coalition for Responsible Waste Incineration (CRWI), and the Sierra
Club.\2\ Under this section of the

CAA, the Administrator must initiate reconsideration proceedings with
respect to provisions that are of central relevance to the rule at
issue if the petitioner shows that it was impracticable to raise an
objection to a rule within the public comment period or that the
grounds for the objection arose after the public comment period but
within the period for filing petitions for judicial review.
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    \2\ These petitions are included in the docket for this rule.
See items EPA-HQ-OAR-2004-0022-0516 thru 0519. EPA also received
petitions from Ash Grove Cement Company and the CKRC, Continental
Cement Company, and Giant Cement Holding, Inc. requesting that we
stay the effective date of the particulate matter standard for new
cement kilns. See items EPA-HQ-OAR-2004-0022-0521 and 0523.
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    Of the twenty or so issues raised in the four petitions for
reconsideration, we decided to grant immediate reconsideration of one
of the issues included in the petitions of Ash Grove Cement Company and
CKRC. On March 23, 2006, EPA published a proposed rule granting
reconsideration of the particulate matter standard for new cement
kilns. 71 FR 14665. Also on March 23, 2006, EPA granted a three-month
administrative stay while the particulate matter standard was under
reconsideration. 71 FR 14655. The administrative stay was issued
pursuant to section 307(d)(7)(B) of the CAA and was in effect from
March 23, 2006 to June 23, 2006. Approximately a dozen public comment
letters were submitted in response to the March 2006 proposed rule,
including a request to extend the comment period by two weeks that EPA
granted in a subsequent notice on April 13, 2006. 71 FR 19155. On
October 25, 2006, EPA issued a final rule amending the effective date
of the particulate matter standard for new cement kilns. 71 FR 62388.
That amendment suspended the obligation of new cement kilns to comply
with the particulate matter standard set forth in Sec.
63.1220(b)(7)(i) until we take final action on the March 2006 proposal
to revise the standard. Today's rule announces our final action
regarding Ash Grove Cement Company and CKRC's petitions for
reconsideration of the particulate matter standard for new cement kilns
that was first proposed on March 23, 2006.
    On August 22, 2006, EPA issued letters to the Ash Grove Cement
Company, the CKRC, and the Sierra Club explaining our rationale to deny
reconsideration on several issues.\3\ On September 6, 2006, we
announced our reconsideration of and requested public comment on seven
issues raised in the petitions of the Ash Grove Cement Company, the
CKRC, and the Sierra Club. 71 FR 52624. In addition to requesting
comment on the reconsideration issues, we also sought comment on
several other proposed amendments to various compliance and monitoring
provisions in the hazardous waste combustor NESHAP. Eleven commenters
submitted responses to this reconsideration notice. In addition to
addressing the PM standard for new cement kilns, today's rule announces
our final decision regarding the seven petition for reconsideration
issues and the other compliance and monitoring amendments included in
the September 2006 proposed rule.
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    \3\ A copy of each letter is included in the docket to this
rulemaking. See docket items EPA-HQ-OAR-2004-0022-0558 through 0560.
A summary of the issues for which we denied reconsideration can also
be found in the September 6, 2006 proposed rule. 71 FR at 52627.
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    On September 27, 2007, EPA issued a Federal Register notice
discussing each of the standards in the rule in light of the DC
Circuit's decision in Sierra Club v. EPA, 479 F. 3d 875 (2007) (``Brick
MACT''). The specific focus of this analysis was whether the MACT
floors for each standard were consistent with the requirements of
section 112(d)(2) and (d)(3) of the Act. EPA also sought comment on
amending the record to make clear that it was no longer relying on
certain rationales which appeared inconsistent with the Brick MACT
opinion. EPA solicited and received comment on this analysis and is
responding to those comments in this notice.

III. Final Action on Issues for Which EPA Granted Reconsideration

    EPA granted reconsideration of eight issues raised in the petitions
of the Ash Grove Cement Company, the Cement Kiln Recycling Coalition,
the Coalition for Responsible Waste Incineration, and the Sierra Club.
Accordingly, we requested comment on the eight issues in two notices
published on March 23, 2006 (71 FR 14665) and September 6, 2006 (71 FR
52624). We discuss below our final action regarding the eight issues
raised in the four petitions for reconsideration and include our
response to the major comments received on these issues.

A. Subcategorization of Liquid Fuel Boilers by Heating Value

    In the October 12, 2005 final rule, we divided the liquid fuel
boiler subcategory into two separate boiler subcategories based on the
heating value of the hazardous waste they burn for purposes of
establishing emission standards for metals and total chlorine (TCl):
Those that burn waste with a heating value below 10,000 Btu/lb, and
those that burn hazardous waste with a heating value of 10,000 Btu/lb
or greater. See 70 FR at 59422. Sources would shift from one
subcategory to the other depending on the heating value of the
hazardous waste burned at the time. Id. at 59476.
    Sierra Club petitioned for reconsideration stating that EPA
developed this subcategorization approach after the period for public
comment and, thus, did not provide notice and opportunity for public
comment.\4\ We subsequently granted reconsideration of this provision.
See 71 FR at 52627-28 (September 6, 2006). Although we granted
reconsideration, we did not propose to change the approach.
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    \4\ See letter from James Pew to Stephen Johnson, dated December
12, 2005, Section II, docket item EPA-HQ-OAR-2004-0022-0517.
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    This issue has now become moot because EPA has determined that the
standard for the high heating value subcategory requires revision
because it only applied to HAP in hazardous waste, not to all HAP input
to the boiler (for example, HAP that may be present in fossil fuels or
other non-waste inputs), which is contrary to the DC Circuit's
decisions in Brick MACT, 479 F. 3d at 882-83. (MACT standards must
apply to all HAP regardless of source of input). Moreover, once the
high heating value subcategory is eliminated, there is no basis for a
low heating value subcategory since the whole basis for differentiation
no longer exists. Accordingly, EPA now agrees with the petitioner that
the subcategorization scheme it adopted for liquid fuel boilers is not
appropriate, and EPA intends to amend these standards. See also
preamble sections IV.B and IV.F below (responding to comments on EPA's
September 27, 2007 notice).

B. Correcting Total Chlorine (TCl) Data to 20 ppmv

    In the October 12, 2005 final rule, we corrected all the total
chlorine (TCl) measurements in the data base that were below 20 ppmv to
account for potential systemic negative biases in the Method 0050 data.
See 70 FR at 59427-29.\5\ Sierra Club petitioned for reconsideration
stating that EPA corrected the TCl measurements in response to comments
on the proposed rule--after the period for public comment--and used the
corrected data to revise the TCl emission standards.\6\
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    \5\ See also USEPA, ``Technical Support Document for HWC MACT
Standards, Volume III: Selection of MACT Standards,'' Section 5.5,
September 2005.
    \6\ See letter from James Pew to Stephen Johnson, dated December
12, 2005, Section IV, docket item EPA-HQ-OAR-2004-0022-0517.

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    We granted reconsideration of our approach to account for these
method biases to assess the true performance of the best performing
sources. Reconsideration was appropriate because, as Sierra Club
stated, we decided to correct the TCl data after the period for public
comment on the proposed rule, and correcting the data significantly
impacted the development of the TCl emission standards.
    To account for the bias in the analytic method, we corrected all
TCl emissions data that were below 20 ppmv to 20 ppmv. We accounted for
within-test condition emissions variability for the corrected data by
imputing a standard deviation that is based on a regression analysis of
run-to-run standard deviation versus emission concentration for all
data above 20 ppmv. This approach of using a regression analysis to
impute a standard deviation is similar to the approach we used to
account for total variability (i.e., test-to-test and within-test
variability) of particulate matter emissions for sources that use
fabric filters.
1. Summary of the Final Action
    The comments to the reconsideration notice did not provide a basis
for us to conclude that it was inappropriate to correct all TCl
emissions data that were below 20 ppmv to 20 ppmv to account for
potential systemic negative biases in the Method 0050 data. Therefore,
we reaffirm our approach of correcting the TCl measurements at
promulgation and are making no changes to the October 12, 2005 final
rule.
2. What Are the Responses to Major Comments?
    Comment: Sierra Club (represented by Earthjustice) states that: (1)
Establishing floor emission levels based on measurements below 20 ppmv
that are corrected to 20 ppmv is impermissible because, even assuming
bias in the analytic method, the corrected measurements do not reflect
the performance of the best performing sources; (2) projecting the
variability of emissions for the average of the best performing sources
considering the variability of emissions for sources that are not best
performing sources is inappropriate; (3) the ``statistical imputation''
methodology used to calculate emissions variability is inappropriate
because EPA admits it overestimates variability; and (4) to the extent
EPA relied on achievability as a reason to change the TCl standard, the
Agency acted unlawfully.
    Response: We respond to each issue in turn:
    a. Corrected Measurements Do Not Reflect Performance of the Best
Performing Sources. The best performing sources are those with
measurements below 20 ppmv. We determined, however, and Sierra Club
does not dispute, that those measurements are likely to be affected by
a systemic negative bias in Method 0050 which collected these data so
that the measured level of performance is biased low and therefore
cannot credibly be deemed to reflect these sources' actual level of
performance. 71 FR at 52629-30. Because measurements below 20 ppmv may
not (indeed, likely do not) represent the performance of a source, we
corrected the measurements to 20 ppmv, the only value of which there is
any reasonable certainty. The corrected data thus are our best
projection of the performance (not considering emissions variability)
of those sources with the lowest measured TCl emissions, accounting for
the bias in measurement.
    We note that the Clean Air Act requires EPA ``to make a reasonable
estimate of the performance of the top 12 percent of units.'' CKRC v.
EPA, 255 F.3d 855, 862 (D.C. Cir. 2001), citing Sierra Club v. EPA, 167
F.3d 658, 662 (D.C. Cir. 1999) (interpreting 42 U.S.C. 7429(a)(2),
which requires that ``emissions standards for existing units in a
category * * * shall not be less stringent than the average emissions
limitation achieved by the best performing 12 percent of units in the
category''). The court has made clear that EPA has authority to devise
the means of deriving this estimate, provided the method the Agency
selects ``allow[s] a reasonable inference as to the performance of the
top 12 percent of units.'' Id. Most importantly, though, EPA must show
not only that it believes its methodology provides an accurate picture
of the relevant sources' actual performance, but also why its
methodology yields the required estimate. Id. We have explained the
basis for the negative bias in the analytic method, the existence of
which is not in dispute. The issue then becomes how best to estimate
the performance of the best performing sources given that their
measured performance reflects the bias of the analytic method. We
believe that correcting potentially biased measurements to 20 ppmv is
appropriate because Method 0050 itself states that the method is not
acceptable for demonstrating compliance with HCl emission standards
less than 20 ppm. \7,8\ TCl emission levels greater than 20 ppmv would
be reported by Method 0050 without significant bias (and therefore are
reliable measurements), while measurements reported to be below 20 ppmv
may actually have been as high as 20 ppmv and cannot be reliably
assessed below that number.
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    \7\ See Method 0050, Section 1.2. Also, see equivalent Method
26A, Section 13.1.
    \8\ As further evidence of the Method 0050 bias, the updated,
equivalent method to Method 0050--Method 26A--states that that
method has a possible measurable negative bias below 20 ppm HCl.
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    Sierra Club does not suggest alternative approaches to correct the
potentially biased measurements to project the performance of those
sources, but rather implies that the uncorrected measurements should be
used to establish the floor emission level. This would be arbitrary and
inappropriate because those data almost certainly (no absolute
certainty is possible) do not represent the performance of those
sources due to analytic bias, and moreover, fail to account for
emissions variability of the best performers.
    b. Projecting Emissions Variability Considering Sources Other Than
the Best Performing Sources. We explained that, after correcting
measurements below 20 ppmv to 20 ppmv, the corrected emission levels
for the best performing sources naturally reflected little
variability--corrected data for the best performing sources were
generally the same values, on the order of 20 ppmv. 71 FR 52630/2. This
had the effect of understating the variability associated with these
data--i.e., these sources' performance. These sources' performance over
time thus would not be assessed correctly, so some different type of
estimate must be made. To address this problem, we performed a linear
regression on the data base--including both best performing sources and
other sources--charting standard deviation against emissions, and
extrapolated the regression downward to the emission level for each
best performing source to impute a standard deviation.
    Sierra Club states that it is inappropriate to use emissions
variability for sources that are not best performing sources to project
emissions variability for the best performing sources. We disagree here
because we believe this is the best means of estimating the best
performing sources' variability and hence their actual performance. See
Sierra Club v. EPA, 479 F.3d 875, 882 (D.C. Cir. 2007) (EPA may
consider variability of performers other than best if there is ``a
demonstrated relationship between the two''). First, Sierra Club is not
correct

that EPA is using variability of non-best performers as a proxy for the
variability of the best performers. As just stated, EPA imputed the
regression curve downward after examining all data and it is reasonable
to do so because the relative standard deviation (i.e., variability of
performance normalized for emission concentration) \9\ of the test
condition runs of the better performing sources (i.e., sources with
lower emissions) here was not significantly different from the relative
standard deviation of the test condition runs of the worse performing
sources.\10\ EPA reasonably assumed that this same relationship (i.e.,
the shape of the regression curve) would be the same at lower levels.
The actual level of variability of the best performing sources
resulting from this imputed regression curve shape is less for the best
performing sources than for non-best sources. See generally, memorandum
from Lucky Benedict, EERGC, to Bob Holloway, USEPA, entitled ``Analysis
of Total Chlorine Data above 20 ppmv,'' dated March 21, 2007.
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    \9\ Relative standard deviation is calculated as the standard
deviation times 100 divided by the average, and is expressed as a
percentage.
    \10\ As should be apparent from the following discussion, EPA is
not using information on emission levels of worse performing sources
to estimate the best performers' emission levels (the fact pattern
of the Cement Kiln Recycling Coalition case and Brick MACT cases;
see 255 F.3d at 865 and Brick MACT, 479 F.3d at 881-82).
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    We have (uncorrected) variability results for several sources that
performed close to the best performing sources--four sources emitted
between 21 ppmv and 25 ppmv, and seven sources emitted between 21 ppmv
and 28 ppmv. We considered using the variability of these sources as a
surrogate for the variability for the best performers (i.e., those at
20 ppmv) but were concerned that this may overstate best performers'
variability and hence result in a standard which is too high (i.e.,
insufficiently stringent).\11\ Rather, we used variability results for
all sources, irrespective of emission level, to develop a variability/
emissions regression curve. This curve regressed variability \12\
versus emissions through the low emitting sources that performed close
to the best performers (e.g., including sources with emissions of 21
ppmv and 24 ppmv, only slightly higher than the 20 ppmv for the best
performers). We then extrapolated the curve down to the 20 ppmv
emission level to impute a standard deviation for the best
performers.\13\ As noted above, we determined that there is no
significant difference in relative standard deviation for low emitting
sources (e.g., sources emitting 21 ppmv to 38 ppmv) compared to high
emitting sources (e.g., sources emitting 130 ppmv to 920 ppmv), and
hence that it is reasonable to use all of the available data to derive
a best fit shape of the regression curve.\14\ This similarity confirms
that data on all sources' variability can reasonably be considered--by
means of imputing the shape of the regression curve at the low end--in
estimating the variability of the best performing sources.
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    \11\ For example, the variability (i.e., standard deviation) of
test condition runs generally increases as emission concentrations
increase.
    \12\ We repeat that variability is measured as standard
deviation.
    \13\ USEPA, ``Technical Support Document for HWC MACT Standards,
Volume III: Selection of MACT Standards,'' September 2005, Section
8-1.
    \14\ See memorandum from Lucky Benedict, EERGC, to Bob Holloway,
USEPA, entitled ``Analysis of Total Chlorine Data above 20 ppmv,''
dated March 21, 2007.
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    This approach does not substitute variability from non-best
performers for variability of best performers. Rather, it uses all of
the data to estimate how variability may change as performance improves
to derive a best estimate of the variability of the best
performers.\15\
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    \15\ As it happens, if EPA were erroneously including
information on variability of higher emitting sources in this
analysis, it would result in a more stringent standard because the
shape of the regression slope would be steeper and would cross the
20 ppmv point at a lower point (because less variability would be
imputed at lower emission concentrations). See Figure 1 in the
memorandum cited in the preceding footnote. In fact, because (as
explained in the text above) relative standard deviations of higher
emitting sources do not increase as emissions increase, EPA does not
believe it committed this type of error.
---------------------------------------------------------------------------

    c. Statistical Imputation Is Inappropriate Because It Overstates
Variability. Sierra Club mistakenly believes that we used statistical
imputation to project variability of the corrected data. As just
discussed in section B.2.b., we used a linear regression analysis
specifically because an alternative approach that we used to project
variability of data sets containing nondetects--statistical
imputation--would overstate variability of the corrected data. 71 FR at
52630. We explained that the statistical imputation approach for
correcting data below 20 ppmv without dampening variability would
involve imputing a value between the reported value and 20 ppmv because
the ``true'' value of the biased data would lie in this interval. This
approach would be problematic, however, given that many of the reported
values (based on the biased analytic method) were much lower than 20
ppmv; the statistical imputation approach would tend to overestimate
the run-to-run variability (leading to a standard higher than the one
we are adopting) and hence we rejected its use in this context.
    d. Achievability of a Floor Emission Level. Sierra Club states that
it is unlawful to consider whether a floor emission level is
achievable. But the issue here is assessing sources' performance over
time. If a best performing source on whose performance a MACT floor is
based cannot itself comply with that floor standard, then that source's
performance over time has been improperly assessed. Put another way,
that source's variability (i.e., performance over time) has not been
adequately accounted for. Mossville Environmental Action Now v. EPA,
370 F. 3d 1232, 1241-42 (D.C. Cir. 2004). Since the standard must be
met ``every day and under all operating conditions,'' it is imperative
that the emission data used to represent the performance of the best
performing sources truly represent the performance of those sources
over time by, notably, accounting for emissions variability. Id. at
1242.

C. Use of PS-11 and Procedure 2 as Guidance for Extrapolating the Alarm
Set-Point of a Particulate Matter Detection System (PMDS)

    In its reconsideration petition, CKRC asked that EPA reconsider its
references to Performance Specification 11 (PS-11) and Procedure 2 in
the particulate matter detection system (PMDS) provisions of the
October 12, 2005 final rule. We granted reconsideration because we
developed the procedures for extrapolating the alarm set-point for PMDS
that included references to PS-11 and Procedure 2, in response to
comments on the proposed rule and after the period for public comment.
71 FR at 52630-31.
    CKRC also stated that the reference to PS-11 for particulate matter
Continuous Emissions Monitoring Systems (40 CFR Part 60, Appendix B)
and Procedure 2 (Appendix F, Part 60) for use as guidance to implement
provisions to extrapolate the alarm set-point of a PMDS may effectively
prevent its members from utilizing this option due to significant
technical difficulties and excessive costs.\16\ CKRC further stated
that PS-11 and Procedure 2 contain a number of problems as they would
apply to cement kilns, and that it has

filed a petition for review in the U.S. Court of Appeals for the D.C.
Circuit challenging EPA's final rule adopting PS-11 and Procedure 2,
which case is being held in abeyance.
---------------------------------------------------------------------------

    \16\ See letter from David P. Novello to Stephen L. Johnson
regarding ``Petition for Reconsideration of Certain Provisions of
Hazardous Waste Combustor MACT Replacement Standards Rule,'' dated
December 9, 2005, p. 9, docket item EPA-HQ-OAR-2004-0022-0520.
---------------------------------------------------------------------------

    Finally, CKRC stated that use of a regression analysis approach to
extrapolate the alarm set-point is not justified or necessary to
establish an approximate correlation between the particulate matter
detector system response and particulate matter concentrations. CKRC
suggested that an alternative approach would be based on a linear
relationship passing through zero and the mean of the PM comprehensive
performance test results.
    When we reviewed the procedures in the final rule for establishing
the set-point in light of CKRC's concerns regarding use of a regression
analysis to extrapolate the set-point and use of PS-11 and Procedure 2
as guidance, we identified several shortcomings of the final rule.
Consequently, we proposed to revise the provisions for establishing the
alarm set-point by extrapolation by: (1) Adding procedures to establish
the alarm set-point for operations under the Documentation of
Compliance; (2) revising procedures to extrapolate the alarm set-point
for operations under the Notification of Compliance; and (3) providing
specific rather than generic references to PS-11 and Procedure 2
provisions that must be followed to extrapolate the alarm set-point. 71
FR at 52631-33.
    We also determined that the final rule was silent on what operators
must do when the PMDS (or bag leak detection system (BLDS)) is
malfunctioning (e.g., when it is out of control or inoperable). We
explained in the reconsideration proposal that it is reasonable to
require that operations when the PMDS or BLDS is unavailable be
considered the same as operations that exceed the alarm set-point given
that there would be no information to conclude otherwise. Thus, we
proposed to require sources to correct the malfunction or minimize
emissions, and require that the duration of the malfunction be added to
the time when the PMDS or BLDS exceeds the alarm set-point. If the time
of PMDS or BLDS malfunction and exceedance of the alarm set-point
exceeds 5 percent of the time during any 6-month block time period, the
source would have to submit a notification to the Administrator within
30 days of the end of the 6-month block time period that describes the
causes of the exceedances and PMDS or BLDS malfunctions and the
revisions to the design, operation, or maintenance of the combustor,
air pollution control equipment, or PMDS (or BLDS) it is taking to
minimize exceedances.
1. Summary of the Final Action
    We are today promulgating: (1) Revised procedures to extrapolate
the PMDS alarm set-point which are less prescriptive than those we
proposed in the reconsideration notice; (2) with respect to the
excessive exceedance notification for the PMDS if the set-point is
exceeded for more than five percent of the time during any 6-month
block time period, a requirement, as proposed in the reconsideration
notice, to also include the time the PMDS malfunctions (while the
combustor is operating), as well as the time the PMDS set-point is
exceeded; and (3) revised PMDS general requirements to clarify that, if
the alarm set-point is exceeded or if the PMDS malfunctions, the source
must take the corrective measures it specifies in its operating and
maintenance plan required under Sec.  63.1206(c)(7).
    We discuss below the revised procedures to extrapolate the PMDS
alarm set point. We discuss the other provisions--PMDS and BLDS
malfunctions and clarification of general PMDS requirements--in the
response to major comments below. Please note that the revised
provisions are effective immediately, and today's final rule does not
change the October 14, 2008 compliance date for existing sources
established by the October 12, 2005 final rule. Sources can readily
comply with the revised provisions promulgated today on the compliance
time line established by the October 12, 2005 final rule.
    The revised procedures to extrapolate the PMDS alarm set point
address four aspects: (1) Establishing the set-point for operations
under the Documentation of Compliance; (2) establishing the set-point
for operations under the initial Notification of Compliance; (3) PMDS
quality assurance procedures; and (4) revising the set-point subsequent
to periodic comprehensive performance testing and other testing, such
as for quality assurance. See Sec.  63.1206(c)(9)(ii) through (v). In
addition, please note that the final rule no longer references PS-11 or
Procedure 2. We have concluded that the Relative Response Audit
provisions of Procedure 2, and applying the correlation curve
statistical parameters in PS-11, may not be appropriate in some
situations. Accordingly, the final rule requires sources to recommend
for approval site-specific procedures for PMDS quality assurance and to
determine, as additional data pairs become available, when and how to
evaluate correlation models that may better represent the relationship
between reference method measurements and PMDS responses than a linear
model.
    a. Documentation of Compliance Set-Point. To establish the set-
point for the Documentation of Compliance (DOC), the source must obtain
a minimum of three reference method and PMDS data pairs, as proposed.
71 FR at 52631/3. As proposed, a source: (1) May use existing data
obtained within 60 months of the DOC; (2) must approximate the
correlation of the reference method data to the PMDS data; (3) may
assume a linear correlation; and (4) may use a zero-point. A source
must request approval from the regulatory authority (in the continuous
monitoring system test plan) of their determination whether multiple
correlation curves will be necessary considering the design and
operation of its combustor and PMDS (e.g., cement kilns equipped with
an in-line raw mill and that use a light-scattering detector may need
to establish separate correlation curves with the mill on and mill
off).\17\ We are including this provision in the final rule in light of
comments indicating that multiple correlation curves may be needed to
appropriately correlate reference method and PMDS responses in some
situations.\18\ As proposed, a source must establish the alarm set-
point as the PMDS response that corresponds to a PM concentration that
is 50% of the PM emission standard or 125% of the highest PM
concentration used to develop the correlation, whichever is greater.
The PM emission concentration used to extrapolate the alarm set-point
must not exceed the PM emission standard, however.
---------------------------------------------------------------------------

    \17\ USEPA, ``Current Knowledge of Particulate Matter (PM)
Continuous Emissions Monitoring,'' September 8, 2000, p. 7-3.
    \18\ See letter from David P. Novello to Stephen L. Johnson
regarding ``Petition for Reconsideration of Certain Provisions of
Hazardous Waste Combustor MACT Replacement Standards Rule,'' dated
December 9, 2005, p. 20, docket item EPA-HQ-OAR-2004-0022-0520.
---------------------------------------------------------------------------

    b. Initial Notification of Compliance Set-Point. To establish the
set-point for operations under the initial Notification of Compliance,
a source must request approval from the regulatory authority (in the
continuous monitoring system test plan) of procedures they will use to
establish an approximate correlation curve considering the three pairs
of Method 5 or 5I data, the PMDS response data from the comprehensive
performance test, and any additional data pairs, as warranted (e.g.,
data pairs during as-found operations; data pairs used for the
Documentation of Compliance correlation curve). As

proposed, the final rule: (1) Requires sources to use a least-squares
regression methodology to correlate PM concentrations to PMDS responses
for data pairs; (2) allows sources to assume that a linear regression
model approximates the relationship between PM concentrations and PMDS
responses; and (3) requires sources to establish the alarm set-point as
the PMDS response that corresponds to a PM concentration that is 50% of
the PM emission standard or 125% of the highest PM concentration used
to develop the correlation, whichever is greater. The emission
concentration used to extrapolate the PMDS response must not exceed the
PM emission standard. 71 FR at 52632-33.
    In addition, a source must request approval from the regulatory
authority (in the continuous monitoring system test plan) of their
determination whether multiple correlation curves are needed,
considering the design and operation of the combustor and PMDS for
reasons discussed above. If multiple correlation curves are needed, a
source must request approval of the number of data pairs needed to
establish those correlation curves and explain how the data will be
obtained.
    We are not promulgating the proposed requirement to obtain three
data pairs under as-found operations in addition to the performance
test data pairs because the additional data may not significantly
improve the assumed linear correlation model in all cases.\19\ Having
three as-found data pairs would still result in too few data pairs to
perform statistical analyses to identify the most appropriate
correlation curve.\20\ Additional as-found data pairs may be warranted,
however, in situations such as those where the extrapolated alarm set-
point correlates to a PM concentration close to the PM emission
standard, or where a single correlation curve may be reasonable even
though multiple curves may better represent the correlation. We
conclude that it is more appropriate to make these determinations on a
site-specific basis rather than mandate universal testing that may not
be particularly useful.
---------------------------------------------------------------------------

    \19\ For example, additional as-found data pairs would not
likely improve compliance assurance for sources that extrapolate the
alarm set-point to a response that correlates to only 50% of the PM
emission standard.
    \20\ Even with three as-found data pairs, there would be only
nine data pairs available to establish the correlation curve--three
data pairs from the DOC, three data pairs from the comprehensive
performance test, and the three as-found data pairs. (There would be
10 data pairs if a zero--point were used.) Procedure 2 for PM CEMS
(Appendix F, Part 60) requires a minimum of 12 data pairs for a
relative correlation audit. See Section 10.3(8).
---------------------------------------------------------------------------

    c. PMDS Quality Assurance. For PMDS quality assurance, a source
must request approval from the regulatory authority (in the continuous
monitoring system test plan) of the quality assurance procedures that
will reasonably ensure that PMDS response values below the alarm set-
point do not correspond to PM emission concentrations higher than the
value that correlated to the alarm set-point.\21\
---------------------------------------------------------------------------

    \21\ Please note that the rule also requires quality assurance
procedures for sources that elect to establish the alarm set-point
without extrapolation. In that situation, a source must request
approval from the regulatory authority of the quality assurance
procedures that reasonably ensure that PMDS response values below
the alarm set-point do not correspond to PM emission concentrations
higher than those demonstrated during the comprehensive performance
test.
---------------------------------------------------------------------------

    Today's final rule requires a source to establish site-specific
quality assurance measures rather than comply with the Relative
Response Audit (RRA) provisions of Procedure 2 that apply to PM CEMS,
which was required under the October 12, 2005 final rule and
contemplated in the reconsideration proposal.\22\ For PM CEMS, a RRA is
comprised of three pairs of reference method and PM CEMS responses at
as-found operating conditions. For PMDS, the RRA would involve
obtaining three pairs of reference method and PMDS responses. We now
conclude, however, that all of the quality assurance provisions
established for PM CEMS may not be appropriate for PMDS given that PMDS
responses will only be approximately correlated to PM concentrations
rather than direct measures of such; therefore PMDS correlations will
not be subjected to the statistical criteria applicable to PM CEMS
under section 13.2 of PS-11.
---------------------------------------------------------------------------

    \22\ Section 10.3(6) explains how a RRA is performed for a PM
CEMS, Section 10.4(6) establishes the criteria for passing a RRA for
a PM CEMS, and Section 10.5 establishes procedures for PM CEMS that
fail the RRA.
---------------------------------------------------------------------------

    For example, one criterion under Procedure 2 for passing the RRA,
section 10.4(6)(iii), as we considered adopting it for PMDS, would
require that at least two of the three sets of PMDS and reference
method measurements must fall within a specified area on a graph of the
correlation regression line. The specified area on the graph of the
correlation regression line is defined by two lines parallel to the
correlation regression line, offset at a distance of 25
percent of the numerical emission limit value from the correlation
regression line. In retrospect, and in light of comments on the
reconsideration notice, we have determined that this criterion would be
inappropriate for a PMDS. The correlation regression line for a PMDS
would generally comprise six data pairs when the alarm set-point is
established in the initial Notification of Compliance, while the
correlation regression line for a PM CEMS would comprise 15 data pairs
initially, and if a Reference Correlation Audit, which requires 12 data
pairs, had been performed, a total of 27 data pairs. Consequently, the
PMDS correlation curve would not be as well defined as the PM CEMS
correlation curve--6 data pairs versus 15 to 27 data pairs--and, thus,
the RRA criterion for PM CEMS under section 10.4(6)(iii) would not be
appropriate.
    Please note that a less precise correlation is appropriate for PMDS
because they will be used for compliance assurance (i.e., as an
indicator for reasonable assurance that an emission standard is not
exceeded) rather than compliance monitoring (i.e., as an indicator of
continuous compliance with an emission standard). As such, exceedance
of a PMDS response that appears to correlate to a PM emission level
exceeding the PM standard is not evidence of a violation of the
emission standard. 70 FR at 59490-91.
    In the interim until more definitive guidance is available, we
recommend that sources consider whether some of the RRA provisions of
Procedure 2 may be appropriate for PMDS.
    d. Revising the Initial Notification of Compliance Set-Point. To
revise the set-point subsequent to periodic comprehensive performance
testing and other testing, such as for quality assurance, a source must
propose to the regulatory authority for approval (in the continuous
monitoring system test plan) an approach for how it will periodically
revise the alarm set-point, considering the additional data pairs.
    We are promulgating a site-specific approach to revise the set-
point rather than the prescriptive approach proposed in the
reconsideration notice (i.e., using the statistical parameters
applicable to PM CEMS to identify the most appropriate correlation
model). 71 FR at 52633/2. At proposal, we assumed that a minimum of 13
data pairs would be available for applying the PM CEMS statistical
parameters, and that the parameters could be applied to as few as 13
data pairs. Under today's final rule, there could be as few as six data
pairs \23\ (plus perhaps a zero-point)

available prior to any quality assurance testing that may be approved
or required by the regulatory authority. Consequently, it would be
appropriate to continue to apply the new data pairs obtained from
quality assurance testing and periodic comprehensive performance
testing to the linear correlation model until enough data pairs are
available to warrant applying statistical parameters to determine if
there is a more appropriate correlation model (e.g., logarithmic,
exponential). In addition, the number of data pairs needed for
meaningful statistical analysis will depend on factors including the
range of the data. For example, if much of the data are representative
of the high end of the range of normal operations (or only two modes of
operation--normal within a narrow range and high-end), statistical
analysis may not help identify the most appropriate correlation model.
Thus, we conclude that these determinations should be made on a site-
specific basis.
---------------------------------------------------------------------------

    \23\ A minimum of three data pairs are needed for the
Documentation of Compliance, and an additional three data pairs are
needed for the initial Notification of Compliance (i.e., obtained
during the comprehensive performance test).
---------------------------------------------------------------------------

    We note that sources can consider adding newly obtained data pairs
to the pool of existing data pairs and continue to apply a linear
correlation model to extrapolate the alarm-set-point until it obtains
enough data representative of a range of PM concentrations that would
warrant statistical analysis to identify the most appropriate
correlation model. After a source obtains enough of these data pairs
(e.g., 12 to 15), the statistical parameters that they should consider
to identify the best correlation model include: The confidence interval
half range percentage, the tolerance interval half range percentage,
and the correlation coefficient. PS-11 provides definitions of these
statistical parameters and other information that may be useful when
evaluating correlation models.
2. What Are the Responses to Major Comments?
    Comment: CKRC states that eliminating general references to PS-11
and Procedure 2 while including references to specific provisions of
those procedures does not address their fundamental problem--PS-11 and
Procedure 2 are problematic in a number of ways for cement kilns. CKRC
believes it is unnecessary to include or even refer to specific
procedures to be used when extrapolating the set-point. Instead, the
facility and regulatory authority can and should be encouraged to
develop appropriate procedures on a case-by-case basis. CKRC states
that other extrapolation procedures may become available, and should
not be excluded or precluded.
    Response: This is not the appropriate forum for addressing CKRC's
challenges to PS-11 and Procedure 2. In response to comments received,
however, the final rule no longer references PS-11 or Procedure 2. As
discussed above, we have concluded that the RRA provisions of Procedure
2, and applying the correlation curve statistical parameters in PS-11,
may not be appropriate in some situations. Accordingly, the final rule
requires sources to recommend for approval site-specific procedures for
PMDS quality assurance and to determine, as additional data pairs
become available, when and how to evaluate correlation models that may
better represent the relationship between reference method measurements
and PMDS responses than a linear model.
    Comment: CKRC states that it is inappropriate to sum times when the
alarm set-point is exceeded and times that the PMDS is malfunctioning
(and the source continues to operate). If the sum of these times
exceeds 5 percent of the operating time in a 6-month block time period,
the source would be required to submit an excess exceedance report to
the regulatory authority. This would create unnecessary burdens and
imply incorrectly that PM emissions may be excessive.
    Response: We explained in the reconsideration notice that it is
reasonable to require that operations when the PMDS is unavailable be
considered the same as operations that exceed the alarm set-point given
that there would be no information to conclude otherwise. We maintain
this view, and the commenter did not provide a basis for us to conclude
that this requirement is inappropriate. In filing the excess exceedance
report, however, the source is free to identify the portion of the
exceedance time that was due to the PMDS malfunctioning.
    Comment: CKRC states that it is possible to improperly interpret
Sec.  63.1206(c)(9)(ii)(C) in the October 12, 2005 final rule to
require compliance with the alarm set-point, implying that an
exceedance of the alarm set-point is a violation of the operating
requirements.
    Response: We agree, and have revised the requirement to clarify
that, if the alarm set-point is exceeded, the corrective measures
specified in the operation and maintenance plan must be followed. See
revised Sec.  63.1206(c)(9)(i)(G) through (I) and 63.1206(c)(9)(vii).

D. Tie-Breaking Procedure for New Source Standards

    The petition of the Coalition for Responsible Waste Incineration
(CRWI) sought reconsideration of the tie-breaking procedure used to
identify the single best performing source in cases where the MACT
floor methodology identified multiple sources with the same single best
System Removal Efficiency (SRE)/Feed aggregated scores.\24\ In the rare
instances when a tie occurred, we selected the source with the lowest
emissions (of the tied sources) as the criterion to break the tie. See
70 FR at 59447 and 71 FR at 52634. As noted in CRWI's petition, this
occurred for the mercury and low volatile metals new source standards
for incinerators. Noting that EPA did not discuss the concept of
selecting the source with the lowest emissions as the criterion to
break ties (because this unusual situation did not occur at proposal),
the CRWI argued in its petition that EPA had provided no opportunity to
comment on the tie-breaking procedure. Pursuant to section 307(d)(7)(B)
of the CAA, we granted the CRWI's petition for reconsideration.
---------------------------------------------------------------------------

    \24\ System removal efficiency is a measure of the percentage of
HAP that is removed prior to being emitted relative to the amount
fed to the unit from all inputs (e.g., hazardous waste, raw
materials). For additional discussion of the SRE/Feed methodology,
see 70 FR at 59441-447.
---------------------------------------------------------------------------

    As stated in the September 6, 2006 notice announcing
reconsideration of this issue, the arguments the CRWI presented in its
petition for reconsideration did not initially persuade us that our
tie-breaking procedure--selecting the source (of the tied sources) with
the lowest emissions as the single best performing source--was
erroneous or inappropriate. 71 FR at 52634. However, because we did not
discuss the concept of selecting the source with the lowest emissions
as the criterion to break ties in the proposed rule, we decided to
grant reconsideration on this issue and provide an opportunity for
public comment on the tie-breaking procedure for new sources.
    In the notice of reconsideration, we requested comment on our
decision to select the source (of all tied sources) with the lowest
emissions as the single best performing source for purposes of new
source floor determinations. We also specifically requested comment on
alternative tie-breaking criteria including (1) using the single source
(of the tied sources) with the best SRE; (2) selecting the single
source (of the tied sources) with worst SRE; and (3) using some other
form of averaging (e.g., the

99th percentile upper prediction limit) of the tied sources.
1. Summary of the Final Action
    The comments to the reconsideration notice did not provide a basis
for us to conclude that the tie-breaking procedure used in the final
rule was incorrect, impermissible, or otherwise flawed. Therefore, we
reaffirm the validity of the determination made at promulgation and are
making no changes to the final rule. Because we are retaining the same
tie-breaking procedure as promulgated in the October 12, 2005 rule, the
new source incinerator emission standards promulgated for mercury and
low volatile metals under Sec.  63.1219(b)(2) and (b)(4) remain
unchanged.
2. What Are the Responses to Major Comments?
    In response to the notice of reconsideration, we received four
comment letters on this issue. These comment letters are available in
the official public docket.\25\ A summary of major comments received on
this reconsideration issue and EPA's responses to those comments are
provided below.
---------------------------------------------------------------------------

    \25\ See comments 0565, 0567, 0569, and 0573 in the docket (EPA-
HQ-OAR-2004-0022).
---------------------------------------------------------------------------

    Comment: Three commenters state that EPA misconstrues the language
of section 112(d)(3) of the CAA, especially the phrase ``best
controlled similar source.'' These commenters argue that section
112(d)(3) does not preclude the possibility that more than one source
could be considered ``best.'' Moreover, EPA is not required to select
the single best performing source in instances where EPA's floor
methodology identifies more than one best performing source. Instead of
applying a tie-breaking procedure, these commenters state that EPA
should establish the floor at a level that all can meet (e.g., the
highest emissions achieved among the tied sources).
    Response: We disagree with the commenters' interpretation of
section 112(d)(3). As we explained in the reconsideration notice, we
believe that the tie-breaking procedure adopted in the final rule is a
reasonable interpretation of section 112(d)(3)'s language (it is, at
the least, reasonable to interpret section 112(d)(3) to base the new
source floor on the performance of a single source, since the provision
refers to ``source'' singular, not plural). 71 FR at 52634. The
commenter cites legislative history in support of its interpretation.
H. Rep. No. 101-490 at 328. That legislative history refers to
``similar sources'' after describing standards for new and existing
sources, and the commenter views this language as supporting its view
that the floor standard for new sources can be based on more than one
best performing source. It is not clear that this passage is referring
to new source standards, or whether instead that the plural reference
is only meant to apply to existing sources. It is also not certain that
the legislative history is even applicable, since it interprets a
version of section 112(d)(3) not identical to the final version, and
one which may have allowed consideration of costs at the floor level of
control. See H. Rep. No. 101-490 at 328 (``In addition, EPA has to
consider the above statutory factors, including costs, in determining
stringency and similarity''). In any case, EPA is not aware of any
compelling policy reason to adopt the commenter's interpretation. As
explained in the reconsideration notice, basing the floor standard on
the performance of a single source having the lowest emissions is an
entirely reasonable means of selecting the best performing source among
sources with best feedrate and system removal. 71 FR at 52634.
    Comment: These same commenters state that EPA is inconsistent in
its application of the tie-breaking procedure to other standards. Two
new source standards are cited by commenters as instances where EPA did
not select a single best performing source among MACT pool sources.
Specifically, the commenters refer to the total chlorine standards for
new incinerators and the total chlorine standards for new liquid fuel
boilers (for the category of sources that burn hazardous waste with an
as-fired heating value less than 10,000 Btu/lb).
    Response: Both standards cited by the commenters are cases where
nearly all available total chlorine data reflect the revised data
handling procedure to account for method bias for total chlorine
measurements below 20 ppmv. (See related discussion in section III.B
above on this issue.) In these instances, we corrected all total
chlorine measurements that were below 20 ppmv to 20 ppmv to establish
the total chlorine floors.\26\ For incinerators, all 25 runs of total
chlorine emissions data from the sources that comprise the MACT pool
were corrected to 20 ppmv, and, in the case of liquid fuel boilers (low
heating value subcategory), 17 of 18 runs were corrected to 20 ppmv.
Given that both MACT pools of best performing sources (incinerators and
liquid fuel boilers) comprised sources with the same level of
performance from an emissions perspective (because nearly all of the
best performing sources' emissions were adjusted to the same emissions
level to account for bias in the analytic method), the case is not
analogous to where performance among sources differ. The commenter's
point also is without practical significance since an identical new
source standard would have been promulgated regardless of source
selected (given identical performance by the best performing sources).
---------------------------------------------------------------------------

    \26\ In addition, to address run-to-run variability given that
nearly all runs for these data sets were corrected to 20 ppmv, we
imputed a run standard deviation based on a regression analysis of
run standard deviation versus total chlorine concentration for
sources with total chlorine measurements greater than 20 ppmv. Thus,
emissions at the upper prediction limit at a 99th percentile
confidence level from these sources are identical.
---------------------------------------------------------------------------

    Comment: Three commenters state that the tie-breaking procedure is
not reasonable because it is based on a method that produces arbitrary
results and is impermissible under the statute. The commenters argue
that breaking the tie based on emissions levels (of the tied sources
for the mercury and low volatile metals standards) is inappropriate
because such standards would arbitrarily reflect HAP levels in raw
materials and fossil fuels. In addition, the tie-breaking procedure is
impermissible because it imposes what amounts to beyond-the-floor
standards without consideration of the beyond-the-floor factors (e.g.,
the floors identified by EPA would require one or more of the tied
source having to install upgraded air pollution control equipment to
achieve the floor) including costs, energy, and non-air health and
environmental impacts.
    Response: We disagree with the commenters' statement that the
mercury and low volatile metals standards represent de facto beyond-
the-floor standards. In EPA's view, a purported floor standard which
forces the best performer on whose performance the floor standard is
based to change its practices is a de facto beyond-the-floor new source
standard (or, put another way, has mis-assessed the source's
performance). This is not the case for the mercury and low volatile
metals standards for new incinerators. These standards reflect the
performance of a combination of front end control (limiting the
feedrate of mercury in the hazardous waste) and back end control
(performance of a control technology such as particulate matter
control). Sources have the ability to control emissions of mercury (and
low volatile metals) by either of these control techniques as did the
single best performing source as identified by our tie-breaking
procedure (of the tied

sources). Thus, we have not improperly estimated the performance of the
best performing source since that source is capable of replicating its
own performance.

E. New Source Particulate Matter Standard for New Cement Kilns

    In the October 12, 2005 final rule, we based the particulate matter
standard for new cement kilns on emissions data from the Ash Grove
Cement Company kiln located in Chanute, Kansas (Ash Grove Chanute) and
promulgated a standard of 0.0023 gr/dscf.\27\ The petitions of the Ash
Grove Cement Company and the Cement Kiln Recycling Coalition requested
that EPA reconsider the 0.0023 gr/dscf standard for new cement
kilns.\28\ The petitioners stated that the 0.0023 gr/dscf standard was
not properly noticed because we did not discuss using the emissions
data from Ash Grove Chanute as part of the new source MACT cement kiln
floor analysis in the April 20, 2004 proposed rule.\29\ However, the
particulate matter data from Ash Grove Chanute was considered (in fact,
it was the single best performing source upon which the 0.0023 gr/dscf
standard was based) in the particulate matter MACT floor analysis in
the final rule. 70 FR at 59419.
---------------------------------------------------------------------------

    \27\ See USEPA, ``Technical Support Document for HWC MACT
Standards, Volume III: Selection of MACT Standards,'' September
2005, Appendix F, Table ``APCD-CK-PM.'' The Ash Grove Chanute test
data were from performance testing conducted in December 2001 and
March 2002.
    \28\ The petitions for reconsideration for the Ash Grove Cement
Company and the Cement Kiln Recycling Coalition are included in the
docket (EPA-HQ-OAR-2004-0022). See docket items 0516 and 0520,
respectively.
    \29\ In the 2004 proposed rule, we stated that it was not
appropriate to use the Ash Grove Chanute data for the MACT floor
analysis for existing sources. 69 FR at 21217 n. 35. While the
proposed rule was thus clear that available particulate matter data
from Ash Grove Chanute would not be used in the MACT floor analysis
for existing sources, we did not state whether or not these data
would be evaluated in the new source floor analysis. Thus, no
revision of the standard is necessary.
---------------------------------------------------------------------------

    Pursuant to section 307(d)(7)(B) of the CAA, we granted
reconsideration of the new source particulate matter standard for new
cement kilns. 71 FR 14665. Reconsideration of the standard was
appropriate because we adopted the calculation using particulate matter
emissions data from the Ash Grove Chanute plant after the period for
public comment on the proposed rule. In addition, the petitioners
argued that the particulate matter standard of 0.0023 gr/dscf was
derived using unrepresentative test data from Ash Grove Chanute,
resulting in a standard that the source itself could not achieve. To
support their position, petitioners provided additional particulate
matter performance data from the Ash Grove Chanute plant.
    In the notice of reconsideration, we stated that ``it appears that
the promulgated new source standard for particulate matter for cement
kilns is overly stringent in that it does not fully reflect the
variability of the best performing source over time (the ``emission
control that is achieved in practice,'' using the language of section
112(d)(3)).'' 71 FR at 14668. Incorporating the newly submitted
particulate matter data from the Ash Grove Chanute plant into the MACT
floor analysis, we proposed a revised particulate matter standard for
new cement kilns of 0.0069 gr/dscf. 71 FR at 14669-70. We also proposed
revisions to the particulate matter standards for new incinerators and
liquid fuel boilers (Id.). As discussed in the reconsideration notice,
the MACT floor methodology for particulate matter includes a
``universal variability factor'' to address long-term variability in
particulate matter emissions of sources using fabric filters. 71 FR at
14668 and 70 FR at 59440.\30\ When we included the newly submitted Ash
Grove Chanute data in the universal variability factor analysis, the
long-term variability relationship changed, which led to the proposed
(small) changes to the incinerator and liquid fuel boiler new source
particulate matter standards.
---------------------------------------------------------------------------

    \30\ The universal variability factor relationship is not
developed for each source category, but is based on relevant data
from all hazardous waste combustor source categories. See
``Technical Support Document for HWC MACT Standards, Volume III:
Selection of MACT Standards,'' September 2005, Sections 5.3 and 7.4.
---------------------------------------------------------------------------

1. Summary of the Final Action
    We are today promulgating revised new source standards for
particulate matter for cement kilns and incinerators that burn
hazardous waste. The revised particulate matter standards for new
cement kilns and new incinerators are 0.0069 gr/dscf and 0.0016 gr/
dscf, corrected to 7 percent oxygen, respectively. These amendments
revise 40 CFR 63.1219(b)(7) and 63.1220(b)(7)(i).
    We are not, however, revising the particulate matter standard for
new liquid fuel boilers as proposed. In the March 23, 2006
reconsideration notice, we proposed to revise the particulate matter
standard to 0.0088 gr/dscf (20 mg/dscm) from 0.0087 gr/dscf (20 mg/
dscm) as a result of a minor change in the universal variability factor
relationship. 71 FR at 14670. In a subsequent action, we decided to
express all particulate matter standards in the same format used in the
October 12, 2005 final rule. See 73 FR at 18973 (April 8, 2008). In the
case of liquid fuel boilers, this would be in the units of mg/dscm.
Since the standard promulgated in the October 2005 rule and the
standard calculated in the reconsideration proceedings are identical--
20 mg/dscm--no change in the standard is necessary.
    As proposed, we are amending the compliance date requirements under
40 CFR 63.1206 to require that new cement kilns (i.e., sources that
commenced construction or reconstruction after April 20, 2004, the date
of the rule proposing the full set of MACT standards for cement kilns)
comply with the revised particulate matter standard by the later of
October 28, 2008 or the date the source starts operations. 71 FR at
14671. See amendments to 40 CFR 63.1206(a)(1)(ii)(B). In addition, we
are not amending the compliance date requirements for new incinerators
for reasons discussed in the proposed rule (Id.).
2. What Are the Responses to Major Comments?
    We received fifteen comment letters in response to the notice of
reconsideration. These comment letters are available in the official
public docket. A summary of major comments received on this
reconsideration issue and EPA's responses to those comments are
provided below.
    Comment: One commenter points out that EPA characterized the newly
submitted data by Ash Grove Chanute as ``normal'' in the March 2006
reconsideration notice and states that it is arbitrary and capricious
to include any emissions data characterized as other than ``compliance
test'' (e.g., ``normal'' or ``in-between'' data) in the MACT floor
analysis for particulate matter.\31\ According to the commenter, EPA's
established methodology for particulate matter only considers data
characterized as ``compliance test.'' As an example, the commenter
cites the incinerator analysis included in the October 2005 rule as
evidence that EPA inappropriately departed in the reconsideration
notice from the established MACT floor methodology for particulate
matter. In addition, the commenter states that it is inappropriate to
include in the MACT floor analysis data rated as other than
``compliance test'' due to regulatory oversight and statistical
variability considerations.

Finally, the commenter states that other source categories should also
be afforded the same opportunity to submit ``normal'' emissions data
for inclusion in the floor analyses.
---------------------------------------------------------------------------

    \31\ We classified emissions data of each test condition for
each pollutant in one of four ways: ``compliance test,'' ``normal,''
``in between,'' and ``not applicable.'' 69 FR at 21218-19.
---------------------------------------------------------------------------

    Response: While it is true that we do not consider ``normal''
emissions data for some MACT floors, we disagree with the commenter
that the particulate matter standards are based solely on data rated as
``compliance test.'' The MACT floor standards for particulate matter
are identified using the Air Pollution Control Technology (APCD)
methodology. See 70 FR at 59447; see also Section III.A of September
27, 2007 notice (72 FR at 54878). For reasons discussed in the
technical support document, the APCD approach only considers
``compliance test'' emissions data for sources not equipped with fabric
filters. However, for fabric filter equipped sources, all available
valid emissions data, including those rated as ``normal'' (i.e., day-
to-day, as opposed to compliance test data) are included in floor
analysis for particulate matter.32 33 Given that Ash Grove
Chanute uses a fabric filter to control emissions of particulate
matter, it is appropriate to include in the MACT floor analysis
available emissions data rated as ``normal,'' which we did in the
reconsideration notice. Therefore, we disagree with the commenter that
we deviated from the established APCD approach methodology in the March
2006 reconsideration notice.
---------------------------------------------------------------------------

    \32\ See USEPA, ``Technical Support Document for HWC MACT
Standards, Volume III: Selection of MACT Standards,'' September
2005, Section 7.4, and also Section 5.3. Valid emissions data
includes those characterized as ``compliance test,'' ``normal,'' and
``in between.''
    \33\ We concluded in the October 12, 2005 rule that normal
emissions data from fabric filter-equipped sources should also be
included in the particulate matter floor analysis because
particulate matter emissions are relatively insensitive to baghouse
inlet loading and operating conditions. 70 FR at 59424.
---------------------------------------------------------------------------

    We also note that the commenter is incorrect in stating that the
incinerator MACT floor standards for particulate matter are based only
on ``compliance test'' data. Eleven fabric filter-equipped sources
comprise the MACT pool for incinerators. When evaluating the floor for
particulate matter, available emissions data from all sources but one
(source no. 3000) included either ``normal'' or ``in between'' data in
the analysis.\34\
---------------------------------------------------------------------------

    \34\ USEPA, ``Technical Support Document for HWC MACT Standards,
Volume III: Selection of MACT Standards,'' September 2005, Appendix
F, Table APCD-INC-PM. For example, the single best performing source
was source no. 341, whose valid particulate matter performance data
include both ``compliance test'' data (condition C10) and ``in
between'' data (condition C12). Another best performing incinerator
in the MACT pool was source 3010 that included a total of nine valid
test conditions (one ``compliance test,'' five ``normal,'' and three
``in between''). Individual test condition ratings can be found in
the hazardous waste combustor database. See docket item EPA-HQ-OAR-
2004-0022-0433.
---------------------------------------------------------------------------

    Finally, we disagree that it is inappropriate to include ``normal''
and ``in between'' emissions data from fabric filter-equipped sources
in the APCD approach analysis. As discussed in the October 12, 2005
rule, particulate matter emissions from fabric filter-equipped sources
are more difficult to maximize (compared to other control equipment)
during compliance testing because particulate matter emissions are
relatively insensitive to fabric filter inlet loadings and operating
conditions.\35\ As a result, in addition to ``compliance test'' data,
we also used ``normal'' and ``in between'' rated emissions data from
fabric filter-equipped sources. We did this not only for cement kilns,
but also for other source categories with best performing sources
equipped with fabric filters. Given that the particulate matter floor
analysis was applied equally to all source categories, the commenter's
suggestion of revising the MACT floor standards for other source
categories is without merit.
---------------------------------------------------------------------------

    \35\ USEPA, ``Technical Support Document for HWC MACT Standards,
Volume III: Selection of MACT Standards,'' September 2005, Section
5.3.
---------------------------------------------------------------------------

    Comment: One commenter states that it is arbitrary for EPA to
revise the particulate matter MACT floor standard based on the
selective use of new data from one source (i.e., the data submitted by
Ash Grove Chanute). According to the commenter, EPA must collect data
from all cement kiln sources. The commenter also states that it was
arbitrary and capricious for EPA to accept the newly submitted data
(showing higher emissions of particulate matter) for the Ash Grove
Chanute kiln while refusing to consider or collect other emissions data
from other newly constructed cement kilns that may refute the claim
that new baghouses inevitably deteriorate.
    Response: First, the commenter's belief that the proposed revision
was based entirely on ``new'' data--data for periods after EPA closed
the data information record--is not correct. The most salient data
indicating that the source's performance over time had been
mischaracterized comes from 2003, within the period for which EPA
accepted performance data. The data showed the Ash Grove Chanute test
average over two tests to be 0.0062 gr/dscf (without any statistical
adjustment for variability), higher than its predicted maximum
performance of 0.0023 gr/dscf.\36\ These data would have been presented
to EPA and included in the data base for the promulgated rule had EPA
provided proper notice, and would have necessarily changed the estimate
of the performance of the Ash Grove Chanute kiln.
---------------------------------------------------------------------------

    \36\ Incidentally, these data are yet another instance where
performance tests failed to accurately characterize a source's
performance (despite the commenter's reiterated assertions that such
tests account for all variability because they are conducted under
so-called worst-case conditions). Indeed, in this instance, even the
EPA-predicted level of 0.0023 gr/dscf (which is a value reflecting
statistical adjustment to account for both short-term and long-term
variability) did not adequately account for the source's long-term
variability.
---------------------------------------------------------------------------

    Second, the remaining information was presented to EPA in the
context of reconsideration, and EPA had no choice but to consider it.
Nor was EPA's consideration of the new information arbitrary. EPA did
not selectively seek new information to alter a standard, nor did an
industry group selectively present data to EPA which it could have
presented during the rulemaking. Nor did EPA review only ``cherry-
picked'' data on the performance of the relevant source. Rather, EPA
has reasonably considered all of the information on the performance of
the source characterized as ``best controlled'', which source's
performance formed the sole basis for the new source standard at issue.
    Comment: Two commenters state that the particulate matter standard
of 0.0023 gr/dscf (the standard promulgated in the October 12, 2005
rule) is readily achievable by cement kilns and should not be revised.
These commenters state that it is arbitrary and capricious for EPA to
use the new Ash Grove Chanute data because the higher emission levels
seen with the 2003-2005 data may be the result of other factors besides
normal deterioration of a new baghouse after the initial break-in
period. The commenters suggest other explanations for the higher
emissions including: (1) Ash Grove Chanute had no regulatory incentive
to optimize the kiln's performance in subsequent tests because the
source was subject to an emission standard that is less stringent than
0.0023 gr/dscf; and (2) Ash Grove Chanute does not use a baghouse leak
detection system with its baghouse that would have allowed it to detect
and fix smaller leaks. Therefore, according to the commenters, the
possibility that Ash Grove Chanute allowed the kiln's performance to
deteriorate by failing to install testing equipment and conduct
necessary maintenance is at least as plausible as normal degradation of
a new baghouse after the initial break-in period.

    Response: We disagree with the comment that a particulate matter
standard of 0.0023 gr/dscf represents the performance of the best
performing source, considering performance variability, for new cement
kilns, based on available data and information. The MACT floor standard
is to be based on actual performance data (accounting for variability),
not as the commenter would have it on what could be achieved by using
other control methods not in use at the best performing source (e.g., a
bag leak detection system at Ash Grove Chanute).\37\ The question of
what the best performer would do if it were equipped differently is
legally irrelevant in establishing a floor for new sources since it
does not relate to the best performing source's actual performance. The
Ash Grove Chanute data from 2003-2005 show that the source we
identified as the single best performer in the October 12, 2005 rule--
Ash Grove Chanute--cannot achieve the 0.0023 gr/dscf standard
promulgated in that rule when it operates under the operation and
maintenance practices that were required and otherwise appropriate for
the source.\38\ In other words, the promulgated standard demonstrably
did not account for the source's legitimate operating variability--its
performance over time when operated and maintained properly.
---------------------------------------------------------------------------

    \37\ In fact, and as acknowledged by the commenters, no cement
kilns are currently using a bag leak detection system with their
kiln baghouse.
    \38\ At the time of testing, the fabric filter performance was
maintained by compliance with an opacity standard.
---------------------------------------------------------------------------

    We also disagree that Ash Grove Chanute allowed its kiln's
performance to deteriorate during subsequent testing in 2003-2005
because there was no regulatory incentive to optimize the kiln's
performance. The commenters speculate that because Ash Grove Chanute
operated at particulate matter levels so far below allowable levels in
2001-2002, Ash Grove could have been less concerned with tuning,
optimizing and maintaining the baghouse for the 2003-2005 testing. The
applicable regulations require the kiln to be properly operated and
designed. Thus, Ash Grove Chanute required to maintain good air
pollution control practices for minimizing emissions during the 2003-
2005 testing (e.g., see Sec. Sec.  63.6(e)(1) and 63.1206(c)(7)).
    The emission data themselves do not support the commenters' claim
and support that the source was properly operated. First, the kiln's
performance did not ``deteriorate'' over time. The kiln had lower
emission levels when tested in 2005 (and 2004) than it did during the
2003 tests.\39\ When the kiln was tested on successive days in 2005,
the nine test runs conducted over a consecutive three day period show
that average emissions of particulate matter decrease from the previous
day: Day one emissions averaged 0.0060 gr/dscf, day two averaged 0.0035
gr/dscf, and emissions on day three averaged 0.0017 gr/dscf.\40\ These
test results showing ``improved'' performance combined with Ash Grove
Chanute's statements that there were no changes in the maintenance of
the air pollution control equipment during the three days of testing do
not support the commenter's argument that Ash Grove Chanute's 2003-2005
data reflect an ineffective ongoing maintenance program. Indeed, the
day three results are among the lowest emissions achieved by the source
in our data base.\41\ Thus, neither the claimed lack of a regulatory
incentive to maintain levels achieved in 2001-2002 nor failure to
maintain the air pollution control system would explain why particulate
matter emissions ``improved'' over this three day period, or
``improved'' between 2003 and 2005. The obvious explanation is that
these varying results illustrate the source's normal operating
variability.
---------------------------------------------------------------------------

    \39\ The data were: One test condition conducted in December
2003 averaged 0.0062 gr/dscf; a second test condition conducted in
September 2004 averaged 0.0015 gr/dscf, and three test conditions
conducted in November 2005 averaged 0.0060, 0.0035, and 0.0017 gr/
dscf, respectively. These are actual measurements, and do not
include adjustments for run-to-run variability, or application of
the Universal Variability Factor.
    \40\ We note that the day three particulate matter results are
only slightly higher than levels achieved in 2002: 0.0017 gr/dscf
vs. 0.0013 gr/dscf.
    \41\ See docket item EPA-HQ-OAR-2004-0022-0546.1, page 9.
---------------------------------------------------------------------------

    Comment: One commenter claims that Ash Grove Chanute's 2003-2005
emissions data resulted from tests that were not conducted under the
same operating conditions as the initial tests in late 2001 and early
2002. According to the commenter, varying combustion gas flow rates and
process conditions explain the higher particulate matter emissions in
the 2003-2005 data.
    Response: Hazardous waste combustor sources are subject to site-
specific operating requirements that must be maintained in order to
ensure continued compliance with the hazardous waste combustor MACT
standards, including the particulate matter standard. These operating
requirements are established during a compliance test when sources
generally operate under conditions that are at the extreme high end of
the range of normal operations. Sources do this to provide themselves
operating flexibility for day-to-day operations while complying with
the rule's standards and operating requirements. While operating
conditions may vary among the available Ash Grove Chanute data, the
2003-2005 data were generated while operating within the limits
established during the compliance test. Therefore, we reject the
suggestion that the data are not reflective of Ash Grove Chanute's
performance over time.
    Comment: The same commenter states that EPA based the proposed
standard of 0.0069 gr/dscf on a cement kiln source (Giant Cement
Company, SC) that ceased operations in 2005. The commenter notes that
this is inappropriate and inconsistent with the approach discussed in
the October 12, 2005 final rule whereby EPA concluded that MACT floor
standards should be based only on the performance of sources that
actually are operating (i.e., burning hazardous waste). 70 FR at 59419.
    Response: We agree with the commenter that this source ceased
operations in 2005. While we continue to believe that the approach to
exclude ``no longer operating sources'' from the MACT floor analysis is
appropriate, we believe this situation is different given that the vast
majority of standards are not at issue in these reconsideration
proceedings. We also note that the MACT floor standard for new cement
kilns would increase slightly (the commenter evidently assumed a
decrease) to 0.0071 gr/dscf if we were to make the data base change the
commenter suggests.

F. Beyond-the-Floor Analyses to Consider Multiple HAP That Are
Similarly Controlled

    The petition of the Sierra Club sought reconsideration of several
beyond-the-floor determinations, including beyond-the-floor analyses to
consider multiple HAP that are controlled by a single control
mechanism. One of the concerns was whether EPA had adequately complied
with public notice and comment requirements regarding the beyond-the-
floor evaluations included in the October 12, 2005 final rule. Noting
that EPA had included a new revised beyond-the-floor analysis (in
response to the petitioner's comments to the April 20, 2004 proposed
rule) in the final rule, the Sierra Club argued that EPA had provided
no opportunity to comment on the revised beyond-the-floor analysis.
Pursuant to section 307(d)(7)(B) of the CAA, we granted the Sierra
Club's petition for reconsideration with respect to beyond-the-floor
analyses to consider multiple

HAP that are controlled by a single control mechanism.\42\
---------------------------------------------------------------------------

    \42\ In its petition for reconsideration, the Sierra Club also
requested that EPA reconsider beyond-the-floor standards based on
wet and dry scrubbing. We denied the Sierra Club's petition to
reconsider these rule provisions for reasons discussed in a letter
to Sierra Club. See docket item EPA-HQ-OAR-2004-0022-0558 (August
22, 2006).
---------------------------------------------------------------------------

    In the notice of reconsideration, we requested comment on a revised
beyond-the-floor analysis whereby we evaluated the achievability,
within the meaning of section 112(d)(2) of the CAA, of beyond-the-floor
standards for all HAP for each source category or subcategory. 71 FR at
52635. We called this analysis the ``comprehensive beyond-the-floor
analysis'' (or comprehensive analysis). Id. In general, the
comprehensive analysis was an evaluation of beyond-the-floor control
options that would achieve emission reductions of all HAP, based on
what we consider reasonable assumptions of performance of each control
method, from levels achieved at the MACT floor. Evaluated control
methods included techniques such as activated carbon injection or
carbon beds, improved or new particulate matter control equipment, and
acid gas scrubbing devices.
    Given that some control methods are capable of achieving reductions
of multiple HAP, we apportioned the costs of a specific control method
(e.g., an activated carbon injection system) among the HAP that it
would control. Control method costs are apportioned on a source-by-
source basis to those HAP requiring emission reductions to achieve the
beyond-the-floor standard. We did this because some control methods are
more achievable (within the meaning of section 112(d)(2)) than other
methods. In addition, apportioning costs of control to each HAP allowed
us to determine that beyond-the-floor standards are warranted for a
subset of HAP for a given category or subcategory in cases where
adopting beyond-the-floor standards for all HAP (the comprehensive
analysis) was not justified. For example, based on the results of the
comprehensive analysis at proposal for the existing source solid fuel
boiler category, we tentatively rejected setting beyond-the-floor
standards for all HAP because we judged the suite of standards as
unachievable.\43\ However, based on our proposed methodology to
apportion control costs, we judged the beyond-the-floor standard for
particulate matter as achievable.\44\
---------------------------------------------------------------------------

    \43\ The aggregate total annualized cost of the comprehensive
analysis was $8.8 million and would result in the following emission
reductions: 0.3 g TEQ of dioxin/furans; 468 tpy of particulate
matter; 0.03 tpy of mercury; 0.47 tpy of semivolatile metals; 0.52
tpy of low volatile metals; 794 tpy of total chlorine; and 0.97 tpy
of non-dioxin/furan organic HAP. See July 2006 technical support
document supporting the reconsideration notice (Appendix A, page 10
of 37 and Table 4-4, page 4-6).
    \44\ The beyond-the-floor analysis of particulate matter alone
resulted in total annualized costs of $1.5 million and would result
in a reduction of 468 tpy of particulate. These estimates equate to
a cost-effectiveness of $2,569 per ton of particulate matter, which
we proposed to be justified (Appendix A, page 3 of 37).
---------------------------------------------------------------------------

1. Summary of the Final Action
    After careful consideration of the comments, we are reaffirming
most of the beyond-the-floor determinations made at promulgation of the
October 12, 2005 final rule and initially determined not to change in
the subsequent reconsideration notice. That is, we continue to conclude
that several beyond-the-floor standards are achievable, namely the
beyond-the-floor standards for particulate matter for existing and new
solid fuel boilers. However, because we have determined for independent
reasons not to defend the dioxin/furan standards for liquid fuel
boilers (see section IV.D below), that issue has become moot. These
beyond-the-floor standards were promulgated in the October 12, 2005
final rule. In addition, we are concluding that beyond-the-floor
standards for the remaining standards (of those EPA is defending) are
not warranted.\45\ Therefore, we are making no changes to the final
rule as a result of reconsideration of the beyond-the-floor standards.
---------------------------------------------------------------------------

    \45\ USEPA, ``Technical Support Document for HWC MACT Standards:
Petitions for Reconsideration Support Document,'' February 2008,
Section 4.
---------------------------------------------------------------------------

2. What Are the Responses to Major Comments?
    In response to the notice of reconsideration, we received seven
comment letters on this issue. These comment letters are available in
the official public docket.\46\ A summary of major comments received on
this reconsideration issue and EPA's responses to those comments are
provided below.
---------------------------------------------------------------------------

    \46\ See comments 0563, 0564, 0565, 0567, 0568, 0569, and 0573
in the docket (EPA-HQ-OAR-2004-0022).
---------------------------------------------------------------------------

    Comment: Regarding EPA's rejection of several beyond-the-floor
analyses that included a cost-effectiveness evaluation of the beyond-
the-floor standard, one commenter states that the CAA requires that
EPA's standards must reflect the ``maximum'' degree of reduction that
is achievable considering the ``cost of achieving such emission
reduction'' and any non-air quality health and environmental impacts
and energy requirements. According to the commenter, the only relevant
factors regarding the cost measures are (1) whether it is too costly to
be ``achievable;'' and (2) whether it would yield additional
reductions, so that EPA's standard would not reflect the ``maximum''
achievable degree of reduction without it. The commenter further states
that cost-effectiveness is not relevant to either of these questions
and that cost-effectiveness is not a metric for cost.
    Response: We disagree with the commenter's interpretation. We
addressed a comment similar to this one in a recent final rule for the
Portland Cement Manufacturing NESHAP. 71 FR at 76534 (December 20,
2006). For readers' convenience, our response is repeated below:
    The statute requires that EPA consider ``the cost of achieving such
emission reduction``(section 112 (d)(2)) in determining the maximum
emission reduction achievable. This language does not mandate a
specific method of taking costs into account, as the commenter would
have it, but rather leaves EPA with significant discretion as to how
costs are to be considered. See Husqvarna AB v. EPA, 254 F.3d 195, 200
(D.C. Cir. 2001). In that case, the court interpreted the requirement
in section 213(a)(3) of the CAA (which mirrors the language in section
112(d)(2)) that nonroad engines ``achieve the greatest degree of
emission reduction achievable through the application of [available]
technology * * * giving appropriate consideration to the cost of
applying such technology,'' and held that this language ``does not
mandate a specific method of cost analysis.'' The court therefore
``f[ound] reasonable EPA's choice to consider costs on the per ton of
emissions removed basis.''
    Moreover, where Congress intended that economic achievability be
the means of assessing the reasonableness of costs of technology-based
environmental standards, it says so explicitly. See Clean Water Act
section 301(b)(2)(A) (direct dischargers of toxic pollutants to
navigable waters must meet standards reflecting ``best available
technology economically achievable''). There is no such explicit
directive in section 112(d)(2). EPA accordingly does not accept the
commenter's interpretation.
    Comment: The same commenter argues that the concept of cost-
effectiveness is at odds with the mandate of section 112(d)(2) that

requires beyond-the-floor standards to reflect the ``maximum''
achievable degree of reduction. According to the commenter, cost-
effectiveness is an inherently subjective measure that compares
``cost'' with a benefit (the amount of pollution reduced). By asserting
discretion to set a beyond-the-floor standard at a level yielding not
the ``maximum'' degree of reduction that is ``achievable'' but,
instead, the degree of reduction that EPA believes is cost-effective,
the commenter argues that EPA alters the statutory mandate and defeats
Congress's purpose.
    Response: First, the commenter is simply not correct that section
112(d)(2) precludes EPA from considering cost-effectiveness as a means
of evaluating costs. In addition to the authority cited in the previous
response, see Bluewater Network v. EPA, 372 F.3d 404, 411, (D.C. Cir.
2004) a case interpreting the same statutory language described in the
previous response (section 213(a)(3) of the Act), which is
substantially identical to the language in section 112(d)(2). Rejecting
an argument that EPA must require the greatest technically achievable
reductions immediately, the court stated ``the lesson from Husqvarna *
* * is not that the EPA must adopt the most stringent standards based
on the most advanced control technologies but that the EPA is to arrive
at standards that reduce emissions to the greatest degree possible
after considering the spectrum of available technologies and the costs
and benefits associated with those technologies.'' Considering costs
and benefits associated with control technologies is essentially
synonymous with the cost per increment of HAP removed, viz. cost
effectiveness.\47\
---------------------------------------------------------------------------

    \47\ See also, Bluewater Network v. EPA, 370 F.3d 1, 20 (D.C.
Cir. 2004) (``We agree that EPA may rely on cost and other statutory
factors to set standards at a level less stringent than that
reflected by across-the-fleet implementation of advanced
technologies. This court noted in Husqvarna that `the overriding
goal of [section 213] is air quality and the other listed
considerations, while significant, are subordinate to that goal.'
254 F.3d at 200. Nevertheless, as the court emphasized in reflecting
on very similar language in section 202(l) of the CAA, the provision
`does not resolve how the Administrator should weigh all [the
statutory] factors in the process of finding the greatest emission
reduction achievable.' Sierra Club v. EPA, 355 U.S. App. D.C. 474,
325 F.3d 374, 378 (D.C. Cir. 2003)''.
---------------------------------------------------------------------------

    The comment also mischaracterizes the proposed beyond-the-floor
methodology. The commenter essentially states that EPA's proposed
beyond-the-floor analyses may not reflect the ``maximum'' degree of HAP
reduction that is achievable by a given beyond-the-floor control
technology or method. This is simply not the case. As proposed in the
reconsideration notice, the beyond-the-floor control options are based
on what we consider a reasonable assumption of a given control method's
consistent performance given the levels achieved at the floor.
Therefore, for each HAP, this performance estimate does indeed reflect
the maximum degree of reduction that is achievable. Using total
chlorine as an example, when evaluating beyond-the-floor standards
based on duct injection dry scrubbing for lightweight aggregate kilns
and solid fuel boilers, we assumed an incremental control level of 75%
(from levels achieved at the floor).\48\ We then evaluated the cost
impacts per ton of total chlorine emission reduction, and the adverse
energy and solid waste impacts, but only at the control level of 75%.
That is, we did not evaluate the costs and corresponding emission
reductions of a given control method--in this example duct injection
dry scrubbing--for less stringent beyond-the-floor standards (e.g.,
less efficient control levels of 70%, 60%, 50%, etc. for duct injection
dry scrubbing) and then select the most cost efficient of the various
control levels evaluated. Thus, the beyond-the-floor analyses presented
in the reconsideration proposed rule do correspond to a ``maximum''
degree of HAP reduction.
---------------------------------------------------------------------------

    \48\ See USEPA, ``Draft Technical Support Document for HWC MACT
Standards: Reconsideration of the Beyond-the-Floor Evaluations,''
July 2006, Section 3, page 3-2.
---------------------------------------------------------------------------

    Comment: The same commenter states, contrary to EPA's claim, that
Husqvarna AB v. EPA, 254 F.3d 195, 200 (D.C. Cir. 2001) does not
support EPA's interpretation of section 112(d)(2). According to the
commenter, although EPA apparently based its cost analysis on cost-
effectiveness in Husqvarna, its decision to do so was neither
challenged nor at issue in that case, and Husqvarna does not endorse
it.
    Response: The commenter's reading of Husqvarna is not correct. The
case both holds that language substantially identical to that in
section 112(d)(2) ``does not mandate a specific method of cost
analysis,'' and explicitly upholds the cost-effectiveness method for
assessing costs used in the rule, since it upheld ``the EPA's choice to
consider costs on the per ton of emissions removed basis.'' 254 F.3d at
200. The court also rejected arguments that EPA was required to conduct
incremental cost-effectiveness analyses (justifying each successive
increment of control as cost effective), Id., surely an unnecessary
step if the Agency could not lawfully conduct any type of cost
effectiveness analysis at all as a means of ascertaining if a standard
is achievable considering costs.
    Comment: The same commenter further states that EPA's proposed
method for determining cost-effectiveness for multiple HAP that are
controlled by a single control mechanism is arbitrary and unrelated to
any relevant inquiry under the CAA. The commenter notes several
deficiencies, including: (1) The proposed beyond-the-floor methodology
is arbitrary because EPA did not explain how the cost of a single
control device (e.g., an activated carbon injection system) is
apportioned among the different HAP controlled by it in the
comprehensive analysis; (2) EPA assigned inappropriately the entire
cost of a single control mechanism to each different HAP controlled by
it that yielded false information and a meaningless analysis; and (3)
EPA failed to assess the cost of a control method against all of the
HAP controlled by it.
    Response: We disagree with all the points raised in the comment as
explained below. With respect to the first point made by the commenter,
the technical support document supporting the reconsideration notice
explained how the cost of a single control device was apportioned among
the HAP controlled by it in the comprehensive analysis. The data used
in the beyond-the-floor cost calculations and the cost apportioning
results were also included in the appendices of the technical support
document. Simply stated, the costs of a beyond-the-floor control
technology or technique is apportioned among the HAP that it would
control according to the formula shown in the technical support
document.\49\
---------------------------------------------------------------------------

    \49\ USEPA, ``Draft Technical Support Document for HWC MACT
Standards: Reconsideration of the Beyond-the-Floor Evaluations,''
July 2006, Section 3.1.3. We note that the formula to apportion
beyond-the-floor costs is shown in Section 3.1.3, paragraph (b), on
pages 3-4 and 3-5.
---------------------------------------------------------------------------

    For purposes of responding to the comment that EPA's proposed
beyond-the-floor methodology requires beyond-the-floor controls to be
purchased and installed more than once (thus overestimating total
control costs), the following example illustrates why the methodology
does not do what the commenter suggests. This example shows how the
beyond-the-floor costs are apportioned using the detailed information
presented at proposal in Appendix A of the technical support
document.\50\ Source no. 487 is an

incinerator that would need reductions in emissions of dioxin/furans,
mercury, particulate matter, and semivolatile metals in order to
achieve the suite of beyond-the-floor standards (page 13 of 37 in
Appendix A) in the comprehensive analysis. Emission reductions of
dioxin/furans and mercury would be achieved by a new activated carbon
injection system and improvements to the existing fabric filter, while
reductions in particulate matter and semivolatile metals would be
achieved by the same improvements to the existing fabric filter (Id.).
Thus, costs associated with the activated carbon system are apportioned
between dioxin/furans and mercury, while the costs of the fabric filter
improvements are allocated among all four HAP. We estimated the
combined total annualized costs of one activated carbon injection
system and the fabric filter improvements for source 487 to be
approximately $396,000 (Id.). In the comprehensive beyond-the-floor
analysis, the costs were allocated according to the discussion in
section 3.1.3 of the technical support document. The results of the
proposed analysis show that $178,000 was allocated each to dioxin/furan
and mercury and the remaining $40,000 was allocated equally to
particulate matter and semivolatile metals (page 27 of 37 in Appendix
A). The sum of these allocated costs equals the total cost of the new
activated carbon injection system and fabric filter improvements--
$396,000 ($178,000 + $178,000 + $40,000). Thus, as this example shows,
we disagree with the commenter that the comprehensive beyond-the-floor
analysis inflates control costs by requiring beyond-the-floor costs to
be purchased and installed more than once.\51\
---------------------------------------------------------------------------

    \50\ USEPA, ``Draft Technical Support Document for HWC MACT
Standards: Reconsideration of the Beyond-the-Floor Evaluations,''
July 2006. All page references related to this discussion are from
this document.
    \51\ This example remains valid as an illustration, although EPA
has determined for independent reasons not to defend the standards
for some of the HAP given in the example.
---------------------------------------------------------------------------

    We further disagree with the commenter that our approach to
apportion control costs is inherently arbitrary and unrelated to any
relevant inquiry under the CAA. Apportioning control costs in the
context of the comprehensive analysis allows us to evaluate the costs
in relation to the HAP controlled. This is particularly true in the
hazardous waste combustor NESHAP because numerous emission standards
are established, including standards for dioxin/furans, mercury,
semivolatile and low volatile metals, particulate matter, hydrogen
chloride and chlorine, hydrocarbons and carbon monoxide.\52\ The
allocation approach allows us to evaluate the costs associated with a
specific HAP and compare it to costs that we have accepted (or
rejected) in other EPA air programs. Otherwise, given the extensive use
of standards for individual HAP, such comparisons are difficult.
Moreover, we are willing to assume higher costs for particularly toxic
HAP and apportioning control method costs among the similarly
controlled HAP helps us identify such cases. For example, consider the
following two theoretical beyond-the-floor situations for a control
method that achieves a total combined reduction of 100 tons of total
chlorine and mercury at a cost of $1,000,000. Assume under the first
scenario that the emission reductions would be split at 99.99 tons of
total chlorine and 0.01 tons of mercury. Under the second scenario, 100
tons of total chlorine and mercury would also be reduced, but assume
the emissions split is 90 tons of total chlorine and 10 tons mercury.
While the overall cost and total reduction in emissions are constant
between the two scenarios and may not be warranted as a beyond-the-
floor control option, we may find the reductions for mercury under the
second scenario as justified, given the greater reductions achieved for
mercury, and given that mercury is a persistent bioaccumulative toxic
compound.\53\
---------------------------------------------------------------------------

    \52\ For example, as explained in an earlier footnote, we
rejected as unachievable the costs associated with adopting beyond-
the-floor standards for all HAP for solid fuel boilers. However, our
cost allocation procedure showed us that the particulate matter
standard was achievable even though beyond-the-floor standards for
the remaining HAP were not.
    \53\ See also 64 FR at 52882 and 52897 (September 30, 1999),
where EPA accepted a higher cost-effectiveness for semivolatile
metal reductions for cement and lightweight aggregate kilns to
ensure that these sources are using the best controls for HAP
introduced almost exclusively from the burning of hazardous waste.
---------------------------------------------------------------------------

    Finally, the commenter states that EPA failed to assess the cost of
a control method against all the HAP controlled by it. We disagree. The
table below, summarizing information in the record at the time we
issued the reconsideration notice, presents the comprehensive beyond-
the-floor analysis for each source category.\54\ The summary table
below shows the total annualized control costs and associated emission
reductions for the beyond-the-floor option for all HAP and HAP
surrogates.\55\
---------------------------------------------------------------------------

    \54\ USEPA, ``Draft Technical Support Document for HWC MACT
Standards: Reconsideration of the Beyond-the-Floor Evaluations,''
July 2006, Section 3.1.3, Table 4-4, and Appendix A. The examples in
the text are to illustrate the reasonableness of the general
methodology for making beyond-the-floor determinations. EPA has
determined, for independent reasons, not to defend certain of the
standards included in the above Table.
    \55\ The PM standard is used as a surrogate to control: (1)
Emissions of nonenumerated metals (antimony, cobalt, manganese,
nickel, and selenium) that are attributable to all feedstreams (both
hazardous waste and remaining inputs); and (2) all nonmercury metal
HAP emissions (both enumerated and nonenumerated metal HAP) from the
nonhazardous waste process feeds at cement kilns, lightweight
aggregate kilns, and liquid fuel boilers (e.g., emissions
attributable to coal and raw material at a cement kiln, and
emissions attributable to fuel oil for liquid fuel boilers).

               Table 1--Summary of Comprehensive Beyond-the-Floor (BTF) Analysis in Proposed Rule
----------------------------------------------------------------------------------------------------------------
                                              Total                 Emission reductions of BTF option
                                           annualized   --------------------------------------------------------
            Source category                cost of BTF      Total all HAP and HAP      Reductions by HAP and HAP
                                             option               surrogates                   surrogate
----------------------------------------------------------------------------------------------------------------
Incinerators...........................     $20,200,000  140 t......................  D/F: 0.8 g; PM: 46 t; Hg:
                                                                                0.2 t; SVM: 0.4 t; LVM:
                                                                                0.2 t; TCl: 91 t; organic
                                                                                HAP: 2.4 t.
Cement kilns...........................      27,800,000  499 t......................  D/F: 1.4 g; PM: 322 t; Hg:
                                                                                0.7 t; SVM: 1.3 t; LVM:
                                                                                0.06 t; TCl: 141 t;
                                                                                organic HAP: 33 t.
Lightweight aggregate kilns............       4,200,000  279 t......................  D/F: 1.1 g; PM: 9.1 t; Hg:
                                                                                0.02 t; SVM: 0.02 t; LVM:
                                                                                0.01 t; TCl: 270 t;
                                                                                organic HAP: 0.2 t.
Liquid fuel boilers....................      24,400,000  679 t......................  D/F: 0.4 g; PM: 437 t; Hg:
                                                                                0.06 t; SVM: 0.1 t; LVM:
                                                                                1.1 t; TCl: 241 t;
                                                                                organic HAP: 0.1 t.
Solid fuel boilers.....................       8,800,000  1,264 t....................  D/F: 0.3 g; PM: 468 t; Hg:
                                                                                0.03 t; SVM: 0.5 t; LVM:
                                                                                0.5 t; TCl: 794 t;
                                                                                organic HAP: 1.0 t.

Hydrochloric production furnaces.......         904,000  17 t.......................  D/F: 0.1 g; TCl: 17 t;
                                                                                organic HAP: 0.01 t.
----------------------------------------------------------------------------------------------------------------

    Comment: The same commenter states that EPA proposed a flawed
beyond-the-floor analysis with respect to organic HAP (other than
dioxin/furans) that would be controlled by activated carbon injection.
According to the commenter, carbon monoxide and hydrocarbons are not
valid surrogates for non-dioxin/furan organic HAP, in general, and are
irrational as a basis for evaluating the cost-effectiveness of
activated carbon injection for the organic HAP that it controls because
EPA did not propose a cost-effectiveness of the control measure. As a
result, the proposed beyond-the-floor analysis overstated costs and
understated effectiveness.
    Response: To the extent the commenter is suggesting that carbon
monoxide and hydrocarbons are generally poor surrogates for organic
HAP, we strongly disagree. We have fully explained in earlier rules our
rationale of using these organic HAP surrogates when establishing MACT
floor standards for hazardous waste combustors. 64 FR at 52847-52.
Furthermore, the beyond-the-floor analysis of control methods for
organic HAP that do not control other HAP regulated by this rule (
e.g., use of an afterburner or use of better combustion practices to
reduce organic HAP emissions) are not at issue in this proceeding.
    As stated in the reconsideration notice, we indicated that it was
inappropriate to identify numerical beyond-the-floor standards for
carbon monoxide and hydrocarbons based on activated carbon injection.
71 FR at 52636. We continue to believe this decision is sound for the
reasons discussed in the proposed rule. However, in response to
comments, we have examined the activated carbon injection beyond-the-
floor analysis discussed in the reconsideration notice. In the proposed
rule we estimated total annualized costs and emission reductions of
dioxin/furans, mercury, and organic HAP associated with activated
carbon injection.\56\ Aggregating the costs and emission reductions for
the three HAP, the cost-effectiveness of the activated carbon injection
option can be estimated for each source category. For each source
category, the cost-effectiveness results were considered unreasonable,
within the meaning of section 112(d)(2). For example, the cement kiln
standards were found to be most cost-effective at approximately
$560,000 per ton of organic HAP, mercury, and dioxin/furan removed.
Given that 98% of the 34 tpy of HAP reduced under the activated carbon
injection option are organic HAP, we find that this cost-effectiveness
value exceeds estimates previously rejected by EPA for organic HAP
control for non-hazardous waste cement kilns. 71 FR at 76531.
---------------------------------------------------------------------------

    \56\ USEPA, ``Draft Technical Support Document for HWC MACT
Standards: Reconsideration of the Beyond-the-Floor Evaluations,''
July 2006, page 4-6, Appendix A, pages 2 and 4.
---------------------------------------------------------------------------

    Comment: One commenter states that some of the emission standards
promulgated in the October 12, 2005 final rule already represent
beyond-the-floor standards because EPA has not shown that 12% of
existing sources can achieve the standards without modification. Thus,
the commenter states that the beyond-the-floor analyses are moot until
EPA justifies the existing standards as beyond-the-floor standards.
    Response: We disagree with the commenter. The MACT floor standards
are based on the performance of actual sources within each source
category. That is, we did not base MACT floors on theoretical sources.
Given that the control methods needed to achieve the MACT floor
standards are fully integrable and compatible, we are not obligated to
establish a suite of floor standards that are simultaneously achievable
by at least six percent of the sources because the standards are not
technically interdependent. See Chemical Manufacturers Ass'n, 870 F. 2d
at 239 (best performing sources can be determined on a pollutant-by-
pollutant basis so that different plants can be best performers for
different pollutants).
    Comment: One commenter suggests that EPA better explain how costs
were allocated among multiple HAP in the comprehensive analysis and why
the chosen method is reasonable and appropriate.
    Response: In finalizing the technical support document, we have
expanded the discussion as suggested by the commenter. See ``Technical
Support Document for HWC MACT Standards: Petitions for Reconsideration
Support Document,'' October 2008.

G. Dioxin/Furan Standard for Incinerators With Dry Air Pollution
Control Devices

    The petition of the Sierra Club sought reconsideration of the
dioxin/furan standard for existing incinerators with either a dry air