Benzene NESHAP provides flexibility regarding what factors the EPA
might consider in making determinations and how these factors might be
weighed for each source category. Thus, the level of the MIR is only
one factor to be weighed in determining acceptability of risks.
    The EPA wishes to point out that certain health information has not
been considered to date in making residual risk determinations. In
assessing risks to populations in the vicinity of the facilities in
each category, we present risk estimates associated with HAP emissions
from the source category alone (source category risk estimates) and the
risks due to HAP emissions from the entire facility at which the
covered source category is located (facility wide risk estimates). We
have not attempted to characterize the risks associated with all HAP
emissions impacting the populations living near the sources in these
categories. That is, at this time, we do not attempt to quantify those
HAP risks that may be associated with emissions from other facilities
that are not included in the source categories in question, including
mobile source emissions, natural source emissions, persistent
environmental pollution, and atmospheric transformation in the vicinity
of the sources in these categories.
    The agency understands the potential importance of considering an
individual's total exposure to HAP in addition to considering exposure
to HAP emissions from the source category and facility. This is
particularly important when assessing non-cancer risks, where
pollutant-specific exposure health reference levels (e.g., RfC) are
based on the assumption that thresholds exist for adverse health
effects. For example, the agency recognizes that, although exposures
attributable to emissions from a source category or facility alone may
not indicate the potential for increased risk of adverse non-cancer
health effects in a population, the exposures resulting from emissions
from the facility in combination with emissions from all of the other
sources (e.g., other facilities) to which an individual is exposed may
be sufficient to result in increased risk of adverse non-cancer health
effects. In May 2010, the EPA SAB advised us ``* * * that RTR
assessments will be most useful to decision makers and communities if
results are presented in the broader context of aggregate and
cumulative risks, including background concentrations and contributions
from other sources in the area.'' \34\
---------------------------------------------------------------------------

    \34\ The EPA's response to this and all other key
recommendations of the SAR's advisory on RTR risk assessment
methodologies (which is available at: http://yosemite.epa.gov/sab/
sabproduct.nsf/4AB3966E263D943A8525771F00668381/$File/EPA-SB-10-007-
unsigned.pdf) are outlined in a memo to this rulemaking docket from
David Guinnup entitled, EPA's Actions in Response to the Key
Recommendations of the SAB Review of RTR Risk Assessment
Methodologies.
---------------------------------------------------------------------------

    Although we are interested in placing source category and facility
wide HAP risks in the context of total HAP risks from all sources
combined in the vicinity of each source, we are concerned about the
uncertainties of doing so. At this point, we believe that such
estimates of total HAP risks will have significantly greater associated
uncertainties than for the source category or facility wide estimates,
and hence would compound the uncertainty in any such comparison. This
is because we have not conducted a detailed technical review of HAP
emissions data for source categories and facilities that have not
previously undergone an RTR review or are not currently undergoing such
review.

C. How did we perform the technology review?

    For our technology review, we identified and evaluated the
developments in practices, processes and control technologies that have

occurred since the 1999 MACT rules were promulgated. In cases where we
identified such developments, we analyzed the technical feasibility of
and the estimated impacts (costs, emissions reductions, risk
reductions, etc.) of applying these developments. We then decided,
based on impacts and feasibility, whether it was necessary to propose
amendments to the regulation to require any of the identified
developments.
    Based on our analyses of the data, information collected under the
voluntary industry survey, our general understanding of both of the
industries and other available information on potential controls for
these industries, we identified potential developments in practices,
processes, and control technologies.
    For the purpose of this exercise, we considered any of the
following to be a ``development'':
     Any add-on control technology or other equipment that was
not identified and considered during development of the 1999 MACT
rules.
     Any improvements in add-on control technology or other
equipment (that were identified and considered during development of
the 1999 MACT rules) that could result in significant additional
emissions reduction.
     Any work practice or operational procedure that was not
identified or considered during development of the 1999 MACT rules.
     Any process change or pollution prevention alternative
that could be broadly applied to the industry and that was not
identified or considered during development of the 1999 MACT rules.
     Any development in equipment or technology that could
result in increased HAP emissions.
    In addition to reviewing the practices, processes, and technologies
that were not considered at the time we developed the 1999 MACT rules,
we reviewed a variety of data sources for the mineral wool and wool
fiberglass industries. Among the data sources we reviewed were the
NESHAP for various industries that were promulgated after the 1999 MACT
rules. We reviewed the regulatory requirements and/or technical
analyses associated with these regulatory actions to identify any
practices, processes and control technologies considered in these
efforts that could possibly be applied to emissions sources in the
Mineral Wool Production and Wool Fiberglass source categories, as well
as the costs, non-air impacts, and energy implications associated with
the use of these technologies. We reviewed scientific and technical
literature regarding refractory products including high chrome
refractories and consulted experts in the refractory manufacturing
field.
    Control technologies, classified as RACT, BACT, or LAER apply to
stationary sources depending on whether the sources are existing or
new, and on the size, age and location of the facility. We consulted
the EPA's RBLC to identify potential technology advances. BACT and LAER
(and sometimes RACT) are determined on a case-by-case basis, usually by
State or local permitting agencies. The EPA established the RBLC to
provide a central database of air pollution technology information
(including technologies required in source-specific permits) to promote
the sharing of information among permitting agencies and to aid in
identifying future possible control technology options that might apply
broadly to numerous sources within a category or apply only on a
source-by-source basis. The RBLC contains over 5,000 air pollution
control permit determinations that can help identify appropriate
technologies to mitigate many air pollutant emissions streams. We
searched this database to determine whether it contained any practices,
processes, or control technologies for the types of processes covered
by the Mineral Wool Production and Wool Fiberglass Manufacturing MACT
rules.
    Additionally, we requested information from facilities regarding
developments in practices, processes, or control technology. Finally,
we reviewed other information sources, such as State and local
permitting agency databases and industry-supported databases.

D. What other issues are we addressing in this proposal?

    In addition to the analyses described above, we also reviewed other
aspects of the MACT standards for possible revision. Based on this
review we have identified several aspects of the MACT standards that we
believe need revision. This includes proposing revisions to the
startup, shutdown, and malfunction provisions of the MACT rule in order
to ensure that they are consistent with a recent court decision in
Sierra Club v. EPA, 551 F. 3d 1019 (DC Cir. 2008).
    We are proposing HAP-specific emission limits for COS, phenol, and
methanol in place of surrogacy in the MACT standards. The proposed rule
also would regulate the collection process as a source of HAP emissions
of phenol, methanol and formaldehyde that were not included in the 1999
Mineral Wool MACT standard.
    In addition, we are proposing other various minor changes with
regards to editorial errors and other revisions to promote the use of
plain language. The analyses and proposed decisions for these actions
are presented in Section VI of this preamble.

E. What analyses were performed for the Mineral Wool Production source
category under the Regulatory Flexibility Act?

    Section 609(b) of the RFA requires a Panel to be convened prior to
publication of the IRFA that an agency may be required to prepare under
the RFA. The RFA directs the Panel to report on the comments of small
entity representatives and make findings on the following elements:
     A description and estimate of the number of small entities
to which the proposed rule will apply;
     A description of projected reporting, recordkeeping and
other compliance requirements of the proposed rule, including an
estimate of the classes of small entities that will be subject to the
requirements and the type of professional skills necessary for
preparation of the report or record;
     An identification, to the extent practicable, of all
relevant federal rules which may duplicate, overlap, or conflict with
the proposed rule; and
     Descriptions of any significant alternatives to the
proposed rule which accomplish the stated objectives of applicable
statutes and which minimize any significant economic impact of the
proposed rule on small entities. This analysis must discuss any
significant alternatives such as:
     The establishment of differing compliance or reporting
requirements or timetables that take into account the resources
available to small entities;
     The clarification, consolidation, or simplification of
compliance and reporting requirements under the rule for such small
entities;
     The use of performance rather than design standards; and
     An exemption from coverage of the rule, or any part
thereof, for such small entities.
    Once completed, the Panel Report presents the results of the
analyses identified in the above list, and is provided to the agency
issuing the proposed rule and is included in the rulemaking record. The
agency is to consider the Panel's findings when completing the draft of
the proposed rule. In light of the Panel Report, and where appropriate,
the agency is also to consider whether changes are needed to the IRFA
for the proposed rule or the

decision on whether an IRFA is required.
    The Panel's findings and discussion are based on the information
available at the time the final Panel Report is published. The EPA will
continue to conduct analyses relevant to the proposed rule, and
additional information may be developed or obtained during the
remainder of the rule development process.
    Any options identified by the Panel for reducing the rule's
regulatory impact on small entities may require further analysis and/or
data collection to ensure that the options are practicable,
enforceable, environmentally sound and consistent with the CAA and its
amendments. The Mineral Wool SBAR Panel convened on June 2, 2011, to
address regulatory flexibility alternatives and opportunities for the
mineral wool industry.

VI. Summary of Proposed Decisions and Actions

    Pursuant to CAA sections 112(d)(2), 112(d)(6) and 112(f), we are
proposing to revise the 1999 MACT rules relative to mineral wool
production and wool fiberglass manufacturing to include the standards
and requirements summarized in this section. More details of the
rationale for these proposed standards and requirements are provided in
Sections VII and VIII of this preamble. In addition, as part of these
rationale discussions, we solicit public comment and data relevant to
several issues. The comments we receive during the public comment
period will help inform the rule development process as we work toward
promulgating a final action.

A. What are the proposed decisions and actions related to the Mineral
Wool Production NESHAP?

    The following sections discuss the proposed decisions and actions
regarding unregulated pollutants and emissions sources (i.e., the MACT
floors), recordkeeping and notification, compliance and other proposed
decisions and actions related to subcategorization of emissions sources
and the findings of the SBAR Panel.
1. Addressing Unregulated Pollutants and Emissions Sources From Mineral
Wool Production
    In the course of evaluating the 1999 MACT rule, we identified
certain HAP for which we failed to establish emission standards in the
original MACT (i.e., COS, HF, HCl, phenol, and methanol) and certain
unregulated processes (i.e., collection). Some of these HAP (COS,
phenol, and methanol) were not regulated under the 1999 MACT rule
because they were represented by surrogates (i.e., CO and
formaldehyde). The EPA did not regulate HF and HCl in the 1999 rule
although these HAP are emitted from cupolas. The 1999 MACT rule also
did not regulate any HAP emitted from collection processes that occur
on a bonded line even though these processes emit the HAP phenol,
formaldehyde, and methanol. According to National Lime v. EPA, 233 F.3d
625, 634 (DC Cir. 2000), the EPA has a ``clear statutory obligation to
set emissions standards for each listed HAP.'' As a part of the
information collected in 2010 to support this proposal, we specifically
evaluated COS, HF, and HCl from cupolas and formaldehyde, phenol and
methanol from collection and curing operations.
    For the Mineral Wool Production source category, we are proposing
MACT limits for: (1) COS, HF and HCl for existing, new and
reconstructed cupolas; and (2) formaldehyde, phenol and methanol for
existing, new and reconstructed combined collection and curing
operations. The collection process emits HAP when a phenol-formaldehyde
based binder is sprayed during collection. Such collection processes
immediately precede curing ovens. Both processes emit HAP when they
occur on bonded production lines, but of the two processes, only the
curing oven was regulated under the 1999 MACT standard. This proposed
rule regulates collection and curing as a combined process on bonded
production lines under three subcategories (one subcategory for each
combined process design). The proposed emissions limits were calculated
using the 99 percent UPL method.
    We considered beyond-the-floor options for COS, HF, and HCl
standards for all cupolas, and for formaldehyde, phenol and methanol
for all combined collection and curing operation designs, as required
by section 112(d)(2) of the Act. However, we decided not to propose any
limits based on the beyond-the-floor analyses for COS, HF, HCl,
formaldehyde, phenol, and methanol for these sources because of the
costs, potential disadvantages of additional controls (including the
cost of RTO and unintended SO2 emissions), non-air
environmental impacts, and adverse energy implications associated with
use of these additional controls. The beyond-the-floor analyses are
presented in the technical documentation for this action (see MACT
Floor Analysis for the Mineral Wool Production Manufacturing Source
Category and the MACT Floor Analysis for the Wool Fiberglass
Manufacturing Source Category), and are available in the docket for
this action.
    In summary, we are proposing the following emissions limits for
existing, new, and reconstructed cupolas in the Mineral Wool Production
Source Category as presented in Table 2. We are not proposing changes
to the PM emissions limits in the 1999 MACT rule for Mineral Wool
Production, and for this reason they are not included in the proposed
limits in Table 2 below.

Table 2--Mineral Wool Production Proposed Emissions Limits for Existing,
   New, and Reconstructed Cupolas, Pound of Pollutant per Ton of Melt
------------------------------------------------------------------------
                                             Emission limit (lb/ton of
                                                       melt)
                                         -------------------------------
                Pollutant                                     New and
                                             Existing      reconstructed
                                              cupolas         cupolas
------------------------------------------------------------------------
COS.....................................          3.3             0.017
HF......................................          0.014           0.014
HCl.....................................          0.0096          0.0096
------------------------------------------------------------------------

2. Subcategorization
    Under CAA section 112(d)(1), the EPA has the discretion to ``* * *
distinguish among classes, types, and sizes of sources within a
category or subcategory in establishing * * *'' standards. When
separate subcategories are established, a MACT floor is determined
separately for each subcategory. To determine whether

the mineral wool production facilities warrant subcategorization for
the MACT floor analysis, the EPA reviewed unit and process designs,
operating information, and air emissions data compiled in the industry
survey data set and other information collected by the agency for
development of the NESHAP for this source category. Based on this
review, the EPA concluded that there are significant design and
operational differences in the collection operations at each of the
three facilities that operate a bonded line in this source category.
    For the unregulated process that emits HAP (i.e., collection and
curing for facilities that operate a bonded line), we are proposing to
subcategorize combined collection operations and curing ovens designs
into three subcategories based on what the industry is currently using:
Vertical, horizontal and drum. When separate subcategories are
established, a MACT standard is determined separately for each
subcategory. To determine whether the mineral wool production
facilities warrant subcategorization for the MACT floor analysis, the
EPA reviewed unit and process designs, operating information and air
emissions data compiled in the industry survey data set and other
information collected by the agency for development of the NESHAP for
this source category. Based on this review, the EPA concluded that
there are significant design and operational differences in the
collection operations at each of the three facilities that operate a
bonded line in this source category. The combined collection and curing
designs consist of three design types: Vertical, horizontal and drum.
For each existing, new, and reconstructed combined collection and
curing operation, we are proposing the following emissions limits as
presented in Table 3.

Table 3--Mineral Wool Production Proposed Emissions Limits for Existing,
 New, and Reconstructed Combined Collection and Curing Operations, Pound
                      of Pollutant per Ton of Melt
------------------------------------------------------------------------
                                                          Emission limit
              Design                      Pollutant         (lb/ton of
                                                               melt)
------------------------------------------------------------------------
Vertical..........................  Formaldehyde........         0.46
                                    Phenol..............         0.52
                                    Methanol............         0.63
Horizontal........................  Formaldehyde........         0.054
                                    Phenol..............         0.15
                                    Methanol............         0.022
Drum..............................  Formaldehyde........         0.067
                                    Phenol..............         0.0023
                                    Methanol............         0.00077
------------------------------------------------------------------------

3. Reporting and Recordkeeping Notifications
    We are proposing to revise certain reporting and recordkeeping
requirements of 40 CFR part 63, subpart DDD. Specifically, we are
proposing that facilities maintain records and prepare and submit
performance test reports on the frequency described below in Compliance
Dates and Approaches to comply with the proposed emissions limits for
COS, HF, HCl, formaldehyde, phenol, methanol and the existing PM limit.
Although the PM limits in the existing MACT do not change as a result
of this proposed rule we are proposing the same reporting,
recordkeeping requirements for PM as for the other pollutants addressed
under this proposed rule. We are also proposing language that would
require the use of electronic reporting for all test methods that are
supported by the ERT. Methods supported by ERT may be found at http://www.epa.gov/ttn/chief/ert/index.html.
4. Compliance Dates and Approaches
    We are proposing that facilities that commenced construction or
reconstruction on or before November 25, 2011 must demonstrate
compliance with the requirements of this subpart no later than 3 years
after the effective date of this rule. Affected sources that commenced
construction or reconstruction after the effective date of this rule
must demonstrate compliance with the requirements of this subpart no
later than the effective date of the rule or upon start-up, whichever
is later.
    We are proposing that compliance testing for PM, COS, formaldehyde,
phenol and methanol be conducted using the same test methods as
required by the 1999 MACT rule (i.e., Method 5 for PM and Method 318
for the organic HAP). We are proposing that sources can use either Test
Method 26A or Test Method 320 to determine compliance for HF and HCl.
    We are proposing both an initial performance test and repeat
testing every 5 years or more often if the raw materials charged to the
cupola change by more than 10 percent of that used for the initial
performance test. Finally, we propose that continuous monitoring of
appropriate operating parameters for control devices (e.g., RTO),
cupolas, curing ovens and/or collection operations will be required as
parametric monitoring. This is to ensure continuous compliance with the
PM, COS, HF, HCl, formaldehyde, phenol and methanol emissions limits.
5. Other Decisions and Actions
    In addition to the proposed decisions and actions discussed above,
we are also proposing changes to the use of surrogates in the existing
rule and to subcategorize the combined collection operations and curing
oven designs from those facilities operating bonded lines. We also
discuss here the findings of the SBAR panel.
a. Surrogacy
    As described in Sections III.B and VII.B of this preamble, the
court, in the Brick MACT decision (Sierra Club v. EPA, 479 F.3d 875 (DC
Cir. March 13, 2007))\3\, found that the EPA has a ``clear statutory
obligation to set emission standards for each listed HAP,'' which does
not allow it to ``avoid setting standards for HAP not controlled with
technology.'' Because we did not conduct analyses that would support
the use of CO as a surrogate for COS, or formaldehyde for methanol and
phenol, we cannot demonstrate that we established emission limits for
COS, methanol and phenol in the 1999 MACT standard. Therefore, the
agency is proposing to add emission limits for both phenol and
methanol. Similarly, the agency is proposing to discontinue the use of
CO as a surrogate for COS, and to set emission limits for COS. The
proposed emissions limits for formaldehyde, phenol, methanol and COS
are presented in Tables 2 and 3, above. We are soliciting comment on
our decisions to discontinue use of

formaldehyde and CO as surrogates; any person wishing to establish or
reestablish surrogacy relationships of one pollutant for others should
provide emissions testing to support their conclusions.
b. Small Business Advocacy Review Panel
    For purposes of assessing the impacts of the proposed rule on small
entities, the RFA defines small entities as including ``small
businesses,'' ``small governments,'' and ``small organizations'' (5
U.S.C. 601). The regulatory revisions being considered by the EPA for
this rulemaking are expected to affect a variety of small businesses,
but would not affect any small governments or small organizations. The
RFA references the definition of ``small business'' found in the Small
Business Act, which authorizes the SBA to further define ``small
business'' by regulation. The SBA definitions of small business by size
standards using the NAICS can be found at 13 CFR 121.201. For the
Mineral Wool Production source category (NAICS code 327993), the SBA
size standard for a small business is 500 employees. Based on this size
designation, there are currently 5 small businesses operating with a
total number of 540 employees.
    Under section 609(b) of the RFA, the Panel is to report its
findings related to these four items:
     A description of and, where feasible, an estimate of the
number of small entities to which the proposed rule will apply;
     A description of the projected reporting, recordkeeping
and other compliance requirements of the proposed rule, including an
estimate of the classes of small entities which will be subject to the
requirement and the type of professional skills necessary for
preparation of the report or record;
     Identification, to the extent practicable, of all relevant
federal rules which may duplicate, overlap or conflict with the
proposed rule; and
     A description of any significant alternatives to the
planned proposed rule which would minimize any significant economic
impact of the proposed rule on small entities consistent with the
stated objectives of the authorizing statute.
    The Panel's most significant findings and discussion with respect
to each of these items are summarized below. To read the full
discussion of the Panel findings and recommendations, see Section 9 of
the Panel Report.
1. Number and Types of Entities Affected
    Six companies exist in this industry; five of the six companies are
small businesses. All small businesses in the mineral wool production
industry operate under NAICS code 327993.
2. Recordkeeping, Reporting and Other Compliance Requirements
    The proposed rule under consideration potentially impacts small
businesses by requiring new emission limits on processes that were not
regulated under the MACT standard promulgated in 1999, by requiring
emission limits for pollutants that were not regulated under the MACT,
or both processes and pollutants not regulated under the MACT. All
companies are subject to Title V operating permits requirements, and as
such will be required to add the newly regulated processes to their
operating permits along with compliance demonstrations that the
processes meet each pollutant emission limit in the rule. Compliance
testing will be required to be conducted using EPA methods for each
pollutant. Reporting and recordkeeping requirements are not expected to
change from the MACT, with the exception of additional pollutants and
processes included in such reports.
3. Related Federal Rules
    NAAQS: the most prevalent technology for reducing COS emissions
will increase emissions of SO2. Under the current NAAQS,
none of the small entities are in nonattainment areas, so installation
of emissions control equipment should not subject them to additional
permitting requirements under the SO2 NAAQS. However, the
EPA cannot make such assurances about future NAAQS or future
nonattainment zones, so there is a risk that future compliance with
this rule could trigger additional emissions control requirements
through the Title V/prevention of significant deterioration permit
program.
    GHG: Most emissions control strategies identified by the EPA during
the Panel would increase the energy intensity of mineral wool
production. Although the Panel does not have specific information about
the GHG emissions of individual facilities in this industry, these
facilities could be subject to GHG permitting as that program is phased
in under the Tailoring Rule.
4. Regulatory Flexibility Alternatives
    The Panel agrees that the EPA does not have discretion in a number
of areas that SER commented upon. Specifically, the EPA does not have
the discretion to set the MACT floor emission limits at levels
suggested by the SER. The Panel recognizes that EPA has the authority
to review the MACT standard for completeness, risk, and technology
improvements, and that the agency is currently under court order to
conduct the risk and technology review for the mineral wool source
category and propose amendments to the standard by October 31, 2011,
and promulgate the amendments by October 31, 2012. However, whenever
opportunities for regulatory flexibility arise, and when that
regulatory flexibility can work to lessen impacts to small businesses,
the Panel recommends that the EPA propose amendments to the mineral
wool MACT that offer such regulatory flexibility to the maximum extent
possible. Specifically, these opportunities arise in the following
situations:
     Selection of the averaging method in calculating the MACT
floor for COS from cupolas and phenol, formaldehyde and methanol
emissions from collection and curing processes; and
     Subcategorization of regulated processes, when
appropriate.
    The Panel recommends that the EPA not require BTF emission limits
for the mineral wool industry. Such limits are likely to have
additional cost impacts to industry. In addition, the EPA did not
identify BTF measures for consideration and has found that the results
of the risk assessment show acceptable risks from this source category.
    The Panel recommends subcategorization of collection along the
lines described in Section 3 of the Panel Report, specifically,
subcategorization for vertical collection and curing, horizontal
collection and curing, and drum collection and curing. Based on
available information, the Panel believes that emission standards based
on the average emission limits across both collection and curing
processes at each of the three subcategories would minimize the burden
on small entities while fully complying with the EPA's obligations
under section 112. The Panel also recommends setting MACT limits for
new sources equal to MACT limits for existing sources.
    The Panel recommends that the EPA allow the maximum amount of time
within its discretion (3 years) and work with state permitting
authorities to provide for the additional year permitted by the
statute.
    The Panel recommends that the EPA provide a detailed discussion in
the preamble to the proposed rule that outlines the manner in which
small entities may demonstrate compliance

with the rule, when finalized, during start-up and shutdown. The Panel
also recommends that the EPA propose allowing an affirmative defense
against compliance actions for malfunction events, consistent with
other section 112 rules recently promulgated. For more information on
the SBAR Panel review process and findings, see Section IV.E of this
preamble and the Final Report of the Small Business Advocacy Review
Panel on the EPA's Planned Proposed Rule Risk and Technology Review
(RTR) Amendments to the National Emission Standard for Hazardous Air
Pollutants (NESHAP) for Mineral Wool Production October 2011 in the
docket.
c. Technical Corrections to the Rule
    We are also proposing revisions to certain terms in the existing
NESHAP. Specifically, we are proposing to replace the term
``incinerator'' with ``regenerative thermal oxidizer'' to avoid
confusion with rules promulgated under CAA section 129 and any new
requirement that may be imposed on something called an ``incinerator''.
We are also proposing to specify performance testing frequency for
RTOs.

B. What are the proposed decisions and actions related to the Wool
Fiberglass Manufacturing NESHAP?

    The following sections discuss the decisions proposed by this
action with regard to the following topics: unregulated pollutants and
emissions sources; the risk review; the technology review; our plans
regarding area sources; recordkeeping, reporting and notification
requirements; compliance requirements; and other proposed decisions and
actions (i.e., changes in surrogacy and terminology cleanup).
1. Addressing Unregulated Pollutants and Emissions Sources
    In the course of evaluating the 1999 MACT rule, we identified
certain HAP for which we failed to establish emission standards in the
original MACT (i.e., HF, HCl, phenol and methanol). As stated earlier,
the EPA has ``clear statutory obligation to set emissions standards for
each listed HAP''. National Lime v. EPA, 233 F. 3d 625, 634 (DC Cir.
2000). The EPA specifically evaluated HF and HCl, from glass-melting
furnaces and formaldehyde, phenol and methanol from RS manufacturing
lines and FA manufacturing lines.
a. Surrogacy
    As described in Sections III. B and VII.B of this preamble, the
Court, in the Brick MACT decision, also found that the EPA erred when
we did not establish emission limits for each HAP emitted from
industrial processes regulated by the MACT standard. We are proposing
to replace CO as a surrogate for COS with COS emissions limits. We are
also proposing to discontinue use of formaldehyde as a surrogate for
phenol and methanol. We are, therefore, proposing to add emission
limits for COS, phenol and methanol. The proposed emissions limits can
be found in Tables 4-6, below.

  Table 4--Proposed Emissions Limits for Rotary Spin (RS) Manufacturing
                                  Lines
                    [Pound of pollutant/ton of melt]
------------------------------------------------------------------------
                                                              New and
                Pollutant                   Existing RS    reconstructed
                                               lines         RS lines
------------------------------------------------------------------------
Formaldehyde............................            0.17         0.020
Phenol..................................            0.19         0.0011
Methanol................................            0.48         0.00067
------------------------------------------------------------------------

      Table 5--Proposed Emissions Limits for Flame Attenuation (FA)
                           Manufacturing Lines
                    [Pound of pollutant/ton of melt]
------------------------------------------------------------------------
                                                              New and
                Pollutant                   Existing FA    reconstructed
                                               lines         FA lines
------------------------------------------------------------------------
Formaldehyde............................            5.6             3.3
Phenol..................................            1.4             0.46
Methanol................................            0.50            0.50
------------------------------------------------------------------------

      Table 6--Proposed Emissions Limits for Glass-Melting Furnaces
                    [Pound of pollutant/ton of melt]
------------------------------------------------------------------------
                                                              New and
                Pollutant                    Existing      reconstructed
                                             furnaces        furnaces
------------------------------------------------------------------------
HF......................................          0.002          0.00078
HCl.....................................          0.0015         0.00078
------------------------------------------------------------------------

b. Emission Limits for Unregulated HAPs
    For the Wool Fiberglass Manufacturing source category, we are
proposing MACT limits for HF and HCl for glass-melting furnaces;
formaldehyde, phenol and methanol from existing, new, and reconstructed
RS manufacturing lines; and formaldehyde, phenol and methanol from
existing, new, and reconstructed FA manufacturing lines. The proposed
emissions limits can be found in Tables 4-6 above.
    Section 112(d)(3)(B) of the CAA requires that the MACT standards
for existing sources be at least as stringent as the average emissions
limitation achieved by the best performing 12 percent of sources (for
which the Administrator has or could reasonably

obtain emissions information) in a category with more than 30 sources.
The Wool Fiberglass Manufacturing source category consists of 29
facilities with approximately 80 glass-melting furnaces. Since there
are more than 30 furnaces, we based the MACT floor limit on the average
emissions limitation achieved by the best performing 12 percent of
furnaces.
    The EPA must exercise its judgment, based on an evaluation of the
relevant factors and available data, to determine the level of
emissions control that has been achieved by the best performing sources
under variable conditions. It is recognized in the case law that the
EPA may consider variability in estimating the degree of emissions
reduction achieved by best-performing sources and in setting MACT
floors. See Mossville Envt'l Action Now v. EPA, 370 F.3d 1232, 1241-42
(DC Cir 2004) (holding that the EPA may consider emissions variability
in estimating performance achieved by best-performing sources and may
set the floor at a level that a best-performing source can expect to
meet ``every day and under all operating conditions''). More details on
how we calculate MACT floors and how we account for variability are
described in the MACT Floor Analysis for the Wool Fiberglass
Manufacturing Source Category which is available in the docket for this
proposed action.
    We considered beyond-the-floor options for the HF and HCl standards
for all of the glass-melting furnaces and the formaldehyde, phenol and
methanol standards for all RS manufacturing lines and FA manufacturing
lines, as required by section 112(d)(2) of the Act. We decided not to
propose any limits based on the beyond-the-floor analyses for any of
these pollutants because of the costs, non-air environmental impacts,
and adverse energy implications associated with use of these additional
controls. The beyond-the-floor analysis is presented in the technical
documentation for this action (MACT Floor Analysis for the Mineral Wool
Production Source Category and the MACT Floor Analysis for the Wool
Fiberglass Manufacturing Source Category).
2. Proposed Decisions Based on the Risk Review
    Based on the results of our risk assessment and risk review (which
are described in more detail in Section VIII of this preamble), we are
proposing emission limits for chromium compounds under the authority of
section 112(f)(2) of the CAA of 0.006 pounds of total chromium per
thousand tons of glass pulled. As explained in Section VIII of this
preamble, we are proposing these limits as an outcome of our ample
margin of safety analysis.
3. Proposed Decisions Based on the Technology Review for the Wool
Fiberglass Industry
    As explained in Sections VI.B and VIII.E of this preamble, we are
proposing emissions limits for PM, under section 112(d)(6) (see Table
12 of Section VIII in this preamble). Furthermore, as explained in
Section VIII.F of this preamble, we are proposing emissions limits for
chromium compounds under section 112(d)(6) of the CAA as part of our
technology review (see those sections for details) of 0.006 pounds of
total chromium per thousand tons of glass pulled, which is the same
limit we are proposing under Section 112(f)(2) of the CAA.
    In our technology review for this industry, we discovered and
evaluated two new technology developments that affect emissions from
wool fiberglass manufacturing furnaces: furnace control technologies
and high chrome refractories. These are discussed below.
    Wool fiberglass furnaces are now equipped with air pollution
control devices that achieve emissions of about 0.014 pounds PM per ton
of glass produced. This is about 50 times lower than required under the
MACT rule (0.5 lb PM per ton glass produced). In light of the record
and additional data we received on PM emissions, we are proposing
revised PM limits under the technology review of the wool fiberglass
source category (as described in Section VIII of this preamble).
    Glass-melting furnaces are constructed using refractories, which
direct the heat of the furnace back into the melt. We are aware of a
new technology that is used to significantly extend the life of the
wool fiberglass furnace: refractories that are made of almost 100
percent chromium compounds and that are used to construct entire
furnaces or very large parts of furnaces. Based on emission testing of
one furnace, it appears that the levels of chromium compounds that can
be emitted when glass-melting furnaces are constructed from high chrome
refractories can be significant. This facility operates two furnaces.
The total chromium compound emissions at this facility are estimated as
913 lb/yr assuming that both furnaces emit at a similar rate. This
includes 840 pounds of hexavalent chromium. Industry information
indicates that the furnaces emitting the highest levels of chromium
compounds are constructed in whole or in part from these types of
refractories. (Notes of April 14, 2011; Region 7 Certainteed
Notes).12 13
    It is our understandng that because of the corrosive properties of
the molten glass, fresh refractory is continuously exposed to the
molten glass along the metal/glass contact line in the glass-melting
furnace process. This increases the surface area of the refractory that
is exposed to the molten glass. As a result, when the glass furnace is
constructed using high chrome refractories, the emission levels of
chromium compounds continuously increase over the life of the furnace
(Please refer to notes of April 14, 2011, telephone discussion between
Susan Fairchild and Certainteed). One industry spokesperson estimated
that 20,000 lb/yr of refractory are worn away from the inside walls of
one wool fiberglass furnace and ducted to the control device before
venting to the atmosphere.\35\
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    \35\ Meeting between U.S. EPA, would fiberglass industry
representatives and NAIMA (trade association). August 31, 2011. At
USEPA offices in Research Triangle Park, NC.
---------------------------------------------------------------------------

    On August 31, 2011, industry representatives met with the agency to
provide data, in an attempt to improve our understanding of the levels
of chromium content in refractory products used at wool fiberglass
furnaces and their impacts on chromium compound emissions. In the
meeting industry representatives stated the following:
     The use of chromium in refractories is important to wool
fiberglass operations because it extends the useful life of the
furnace;
     Chromium content of furnaces vary from 0 to 95 percent;
there is no distinction between the types of refractories used at the
highest chrome emitting furnace and the refractories used to construct
other glass furnaces that emit low levels of hexavalent chromium.
     The type of furnace used at the high chromium emitting
facility may may be responsible for increased hexavalent chromium
emissions.
    However, the information from the meeting appears to contradict
other information on the reason for certain furnaces to have elevated
chromium emissions. As previously discussed, emission test results from
the 2010 testing and previous statements made to the EPA from owners/
operators (Notes of April 14, 2011, Certainteed; Region 7 Certainteed
notes) seem to inply that the high chromium emissions are due to the
chromium content of the refractory. Because of this contradictory
information we are requesting

additional emissions testing of wool fiberglass furnaces (discussed
below). We are also soliciting comment on whether and how to
subcategorize industry according to furnace type, or type of
refractory. Commenters should also provide emissions test data to
support their assertions regarding the correct manner in which to
subcategorize the industry.
    As shown in Table 12 of Section VIII of this preamble, we are
proposing chromium compound emissions limits of 0.00006 lb/ton of glass
produced. These limits would apply to wool fiberglass furnaces at major
sources. However, there are no differences in furnaces at major sources
and those at area sources. We are concerned about the levels of
hexavalent chromium that can be emitted by area sources where furnaces
may be constructed or reconstructed using high chrome refractories. We
are announcing today our plans to regulate wool fiberglass area sources
in a future action. We have issued a section 114 information collection
request to the wool fiberglass industry to collect comprehensive
information specific to the chrome content of the refractories used to
construct their glass-melting furnaces and obtain complete chromium
emissions test data. This information will enable us determine the
scope of the source category (in terms of the universe of wool
fiberglass producers that are area sources and that emit hexavalent
chromium) to be regulated in the future action.
    We are requesting information specific to wool fiberglass furnaces,
including information on the chromium content of the refractories used
in furnace construction, process rates and emissions testing.
Nevertheless, we are soliciting comment from the public on our approach
to limit emissions of chromium compounds as well as other alternatives
to reducing emissions of chromium compounds, especially hexavalent
chromium.
4. Reporting, Recordkeeping and Notification Requirements
    We are proposing to revise certain recordkeeping requirements of 40
CFR part 63, subpart NNN. Specifically, we are proposing that
facilities maintain records and prepare and submit performance test
reports to comply with the proposed emissions limits for PM, chromium
compounds, HF, HCl, formaldehyde, phenol and methanol. Because
refractory products can contain chromium compounds that can then be
emitted to the ambient air during wool fiberglass manufacturing, we are
proposing that owners/operators of glass manufacturing furnaces
maintain records of the refractory brick composition from which the
furnaces are constructed, including any rebricking or additional layers
of refractory that are added to the outside furnace walls. In addition,
owners and operators are required to keep records of the occurrence and
duration of each malfunction or operation of the air pollution control
equipment and monitoring equipment. We are also proposing requirements
for the use of electronic reporting for all test methods that are
supported by the ERT. Methods supported by ERT may be found at http://www.epa.gov/ttn/chief/ert/index.html.
5. Compliance Dates and Approaches
    With regard to formaldehyde, HCl, HF, phenol and methanol, we are
proposing that facilities that commenced construction or reconstruction
on or before November 25, 2011 must demonstrate compliance with the
requirements of this subpart no later than 3 years after the effective
date of this rule. Affected sources that commenced construction or
reconstruction after the proposal date of this rule must demonstrate
compliance with the requirements of this subpart no later than the
effective date of the rule or upon start-up, whichever is later. We are
proposing an initial performance test within 90 days of promulgation of
the final rule.
    With regard to total chromium compounds, we are proposing that the
requirements under CAA section 112(f)(2), if finalized, must be
implemented no later than 90 days after the effective date of this
rule, but the EPA may extend that timeframe for circumstances under
which we believe the additional time is necessary for installation of
air pollution control equipment or other measures to reduce HAP
emissions. We are, therefore, allowing affected sources up to one year
from the effective date of this rule to demonstrate compliance with the
chromium emission limits. Consistent with CAA section 112(f)(4)(B), we
are proposing that a one-year compliance period is necessary so that
affected facilities have adequate time to install additional controls
and demonstrate compliance, including the time necessary to purchase,
install and test control equipment. Because these limits reflect the
reductions from glass making furnaces required under both sections
112(d)(6) and 112(f)(2), we believe a one-year compliance timeframe is
needed for the same reasons provided above. In addition, we are
proposing that the PM emissions limit that would reflect reductions
required for the glass making furnaces pursuant to CAA section
112(d)(6) must be met no later than one year after the effective date
of this rule. We believe this time is needed to either enable
installation of replacement bags, or if a facility decides to add a new
baghouse in series with an existing baghouse, seek bids, select a
vendor, install and test the new equipment; prepare and submit the
reports in this proposed rule, if finalized.
    Therefore, we are proposing that wool fiberglass facilities would
be required to show compliance with both PM and the chromium limits
within 1 year of promulgation of this standard. We are soliciting
comments on this aspect of this proposed action.
    Additionally, we propose that compliance with the proposed chromium
compounds emissions limits be demonstrated by annual performance tests
for all glass-melting furnaces subject to this rule as described in
Section VI.B.2 of this preamble. We are proposing additional annual
performance testing no later than 12 calendar months following the
initial or previous performance or compliance test to demonstrate
compliance with the chromium compounds emissions limit for furnaces.
    We are proposing both an initial performance test and repeat
testing every 5 years on the RS and FA lines and each time the binder
formulation changes by more than 10 percent as compared to the binder
formulation used in the initial performance test. We are seeking
comment on whether the binder formulation variability of 10 percent as
used here is appropriate.
    We are proposing that compliance testing for PM, formaldehyde,
phenol and methanol be conducted using the same test methods as
required by the 1999 MACT rule (i.e., Method 5 for PM and Method 318
for formaldehyde, phenol and methanol). We are proposing Test Method
26A be used to determine compliance for HF and HCl and Test Method 0061
be used to ensure compliance with the chromium compounds emission
limit.
    We propose that continuous monitoring of temperatures of control
devices (e.g., fabric filters, wet and dry ESP, scrubbers) for glass-
melting furnaces, RS manufacturing lines, and FA manufacturing lines
will be required as parametric monitoring to ensure continuous
compliance with the PM, chromium compounds, HF, HCl, formaldehyde,
phenol and methanol emissions limits.
    Because the recent test data for glass-melting furnaces show a
significant

portion of the chromium compounds are hexavalent chromium, we are
requiring Test Method 0061 be used to ensure compliance with the
chromium compounds emission limit and as the most cost effective method
to determine both total chromium and hexavalent chromium from wool
fiberglass furnace stacks. Sources must report both total chromium and
hexavalent chromium using this method or all chromium emissions are
assumed to be hexavalent chromium.
6. Other Decisions and Actions
    In addition to the proposed decisions and actions discussed above,
we are also proposing surrogacy changes and some general cleanup in
terminology to the existing rule.
    a. Surrogacy
    As described in Sections III.B and VIII.B in this preamble, the
Court found that the EPA has a ``clear statutory obligation to set
emission standards for each listed HAP.'' Because we did not conduct
analyses that would support the use of formaldehyde as a surrogate for
methanol and phenol, we cannot currently demonstrate that we
established emission limits for the HAP methanol and phenol in the 1999
MACT standard. Therefore, we are proposing the emissions limits for
phenol and methanol, which are presented in Tables 4-6, above.
    b. Technical corrections to the rule.
    We are also proposing revisions to certain terms in the existing
NESHAP. Specifically, we are proposing to replace the term
``incinerator'' with ``RTO'' and specify performance test frequency.

C. What are the proposed decisions and actions related to startup,
shutdown and malfunction?

    The United States Court of Appeals for the District of Columbia
Circuit vacated portions of two provisions in the EPA's CAA section 112
regulations governing the emissions of HAP during periods of SSM.
Sierra Club v. EPA, 551 F.3d 1019 (DC Cir. 2008), cert. denied, 130 S.
Ct. 1735 (U.S. 2010). Specifically, the Court vacated the SSM exemption
contained in 40 CFR 63.6(f)(1) and 40 CFR 63.6(h)(1), that are part of
a regulation, commonly referred to as the ``General Provisions Rule,''
that the EPA promulgated under CAA section 112. When incorporated into
CAA section 112(d) regulations for specific source categories, these
two provisions exempt sources from the requirement to comply with the
otherwise applicable CAA section 112(d) emissions standard during
periods of SSM.
    We are proposing the elimination of the SSM exemption in this rule.
Consistent with Sierra Club v. EPA, the EPA is proposing standards in
this rule that apply at all times. We are also proposing several
revisions to Table 1 to subparts DDD and NNN of part 63 (the General
Provisions Applicability table). For example, we are proposing to
eliminate the incorporation of the General Provisions' requirement that
the source develop an SSM plan. We also are proposing to eliminate or
revise certain recordkeeping and reporting that related to the SSM
exemption. The EPA has attempted to ensure that we have not included in
the proposed regulatory language any provisions that are inappropriate,
unnecessary, or redundant in the absence of the SSM exemption. We are
specifically seeking comment on whether there are any such provisions
that we have inadvertently incorporated or overlooked.
    In proposing the standards in this rule, the EPA has taken into
account startup and shutdown periods and, for the reasons explained
below, is proposing emissions limits for those periods. Information on
periods of startup and shutdown received from the industry survey
indicate that emissions during these periods are less than emissions
during production. Control devices such as baghouses for PM and metal
HAP particulate control and RTO for COS control are started up before
the process units, and are operational during the shutdown phase of a
process. Therefore, no increase in emissions is expected during these
periods. Because the processes are ducted to the control device before
startup and after shutdown, and because emissions during startup and
shutdown are not more than emissions during production, startup and
shutdown emissions limits should be equivalent to the emissions limits
for production. Production based emissions limits are expressed in this
rule on a pound of pollutant per ton melt basis. However, during
startup and shutdown, there is no melt being produced. Therefore,
separate standards for periods of startup and shutdown were developed
by translating the production-based emissions limits from a pound per
ton basis to a pound of pollutant per hour basis and are being proposed
in this rule. Periods of startup, normal operations and shutdown are
all predictable and routine aspects of a source's operations. However,
by contrast, malfunction is defined as a ``sudden, infrequent, and not
reasonably preventable failure of air pollution control and monitoring
equipment, process equipment or a process to operate in a normal or
usual manner * * *'' (40 CFR 63.2). The EPA has determined that CAA
section 112 does not require that emissions that occur during periods
of malfunction be factored into development of CAA section 112
standards. Under CAA section 112, emissions standards for new sources
must be no less stringent than the level ``achieved'' by the best
controlled similar source and for existing sources generally must be no
less stringent than the average emissions limitation ``achieved'' by
the best performing 12 percent of sources in the category. There is
nothing in CAA section 112 that directs the agency to consider
malfunctions in determining the level ``achieved'' by the best
performing or best controlled sources when setting emissions standards.
Moreover, while the EPA accounts for variability in setting emissions
standards consistent with the CAA section 112 case law, nothing in that
case law requires the agency to consider malfunctions as part of that
analysis. Section 112 of the CAA uses the concept of ``best
controlled'' and ``best performing'' unit in defining the level of
stringency that CAA section 112 performance standards must meet.
Applying the concept of ``best controlled'' or ``best performing'' to a
unit that is malfunctioning presents significant difficulties, as
malfunctions are sudden and unexpected events.
    Further, accounting for malfunctions would be difficult, if not
impossible, given the myriad different types of malfunctions that can
occur across all sources in the category and given the difficulties
associated with predicting or accounting for the frequency, degree and
duration of various malfunctions that might occur. As such, the
performance of units that are malfunctioning is not ``reasonably''
foreseeable. See, e.g., Sierra Club v. EPA, 167 F. 3d 658, 662 (DC Cir.
1999) (the EPA typically has wide latitude in determining the extent of
data-gathering necessary to solve a problem. The court generally defers
to the agency's decision to proceed on the basis of imperfect
scientific information, rather than to ``invest the resources to
conduct the perfect study.''). See also, Weyerhaeuser v. Costle, 590
F.2d 1011, 1058 (DC Cir. 1978) (``In the nature of things, no general
limit, individual permit or even any upset provision can anticipate all
upset situations. After a certain point, the transgression of
regulatory limits caused by `uncontrollable acts of third parties,'
such as strikes, sabotage, operator intoxication or insanity, and a
variety of other eventualities, must be a matter for the administrative
exercise of case-by-case enforcement discretion, not

for specification in advance by regulation''). In addition, the goal of
a best controlled or best performing source is to operate in such a way
as to avoid malfunctions of the source and accounting for malfunctions
could lead to standards that are significantly less stringent than
levels that are achieved by a well-performing non-malfunctioning
source. The EPA's approach to malfunctions is consistent with CAA
section 112 and is a reasonable interpretation of the statute.
    In the event that a source fails to comply with the applicable CAA
section 112(d) standards as a result of a malfunction event, the EPA
would determine an appropriate response based on, among other things,
the good faith efforts of the source to minimize emissions during
malfunction periods, including preventative and corrective actions, as
well as root cause analyses to ascertain and rectify excess emissions.
The EPA would also consider whether the source's failure to comply with
the CAA section 112(d) standard was, in fact, ``sudden, infrequent, not
reasonably preventable'' and was not instead ``caused in part by poor
maintenance or careless operation'' 40 CFR 63.2 (definition of
malfunction).
    Finally, the EPA recognizes that even equipment that is properly
designed and maintained can sometimes fail and that such failure can
sometimes cause an exceedance of the relevant emissions standard (see,
e.g., State Implementation Plans: Policy Regarding Excessive Emissions
During Malfunctions, Startup, and Shutdown (Sept. 20, 1999); Policy on
Excess Emissions During Startup, Shutdown, Maintenance and Malfunctions
(Feb. 15, 1983)). The EPA is, therefore, proposing to add to the final
rule an affirmative defense to civil penalties for exceedances of
emissions limits that are caused by malfunctions. See 40 CFR 63.542
(defining ``affirmative defense'' to mean, in the context of an
enforcement proceeding, a response or defense put forward by a
defendant, regarding which the defendant has the burden of proof, and
the merits of which are independently and objectively evaluated in a
judicial or administrative proceeding). We also are proposing other
regulatory provisions to specify the elements that are necessary to
establish this affirmative defense; the source must prove by a
preponderance of the evidence that it has met all of the elements set
forth in 40 CFR 63.552 (40 CFR 22.24). The criteria ensure that the
affirmative defense is available only where the event that causes an
exceedance of the emissions limit meets the narrow definition of
malfunction in 40 CFR 63.2 (sudden, infrequent, not reasonable
preventable and not caused by poor maintenance and or careless
operation). For example, to successfully assert the affirmative
defense, the source must prove by a preponderance of the evidence that
excess emissions ``[w]ere caused by a sudden, infrequent, and
unavoidable failure of air pollution control and monitoring equipment,
process equipment, or a process to operate in a normal or usual manner
* * *.'' The criteria also are designed to ensure that steps are taken
to correct the malfunction, to minimize emissions in accordance with 40
CFR 63.543(j) and to prevent future malfunctions. For example, the
source must prove by a preponderance of the evidence that ``[r]epairs
were made as expeditiously as possible when the applicable emissions
limitations were being exceeded * * *'' and that ``[a]ll possible steps
were taken to minimize the impact of the excess emissions on ambient
air quality, the environment and human health * * *.'' In any judicial
or administrative proceeding, the Administrator may challenge the
assertion of the affirmative defense and, if the respondent has not met
its burden of proving all of the requirements in the affirmative
defense, appropriate penalties may be assessed in accordance with CAA
section 113 (see also 40 CFR 22.27).
    The EPA included an affirmative defense in the proposed rule in an
attempt to balance a tension, inherent in many types of air regulation,
to ensure adequate compliance while simultaneously recognizing that
despite the most diligent of efforts, emission limits may be exceeded
under circumstances beyond the control of the source. The EPA must
establish emission standards that ``limit the quantity, rate, or
concentration of emissions of air pollutants on a continuous basis.''
42 U.S.C. 7602(k)(defining ``emission limitation and emission
standard''). See generally Sierra Club v. EPA, 551 F.3d 1019, 1021 (DC
Cir. 2008). Thus, the EPA is required to ensure that section 112
emissions limitations are continuous. The affirmative defense for
malfunction events meets this requirement by ensuring that even where
there is a malfunction, the emission limitation is still enforceable
through injunctive relief. While ``continuous'' limitations on the one
hand are required, there is also case law indicating that in many
situations it is appropriate for the EPA to account for the practical
realities of technology. For example, in Essex Chemical v. Ruckelshaus,
486 F.2d 427, 433 (DC Cir. 1973), the DC Circuit acknowledged that in
setting standards under CAA section 111 ``variant provisions'' such as
provisions allowing for upsets during startup, shutdown and equipment
malfunction ``appear necessary to preserve the reasonableness of the
standards as a whole and that the record does not support the `never to
be exceeded' standard currently in force.'' See also, Portland Cement
Association v. Ruckelshaus, 486 F.2d 375 (DC Cir. 1973). Though
intervening case law such as Sierra Club v. EPA and the CAA 1977
amendments undermine the relevance of these cases today, they support
the EPA's view that a system that incorporates some level of
flexibility is reasonable. The affirmative defense simply provides for
a defense to civil penalties for excess emissions that are proven to be
beyond the control of the source. By incorporating an affirmative
defense, the EPA has formalized its approach to upset events. In a
Clean Water Act setting, the Ninth Circuit required this type of
formalized approach when regulating ``upsets beyond the control of the
permit holder.'' Marathon Oil Co. v. EPA, 564 F.2d 1253, 1272-73 (9th
Cir. 1977). But see, Weyerhaeuser Co. v. Costle, 590 F.2d 1011, 1057-58
(DC Cir. 1978) (holding that an informal approach is adequate). The
affirmative defense provisions give the EPA the flexibility to both
ensure that its emission limitations are ``continuous'' as required by
42 U.S.C. 7602(k), and account for unplanned upsets and thus support
the reasonableness of the standard as a whole.

D. What are the proposed decisions and actions related to electronic
reporting?

    Records must be maintained in a form suitable and readily available
for expeditious review, according to 63.10(b)(1). Electronic
recordkeeping and reporting is available for many records, and is the
form considered most suitable for expeditious review if available.
Electronic recordkeeping and reporting is encouraged in this proposal
and some records and reports are required to be kept in electronic
format. Records required to be maintained electronically include the
output of continuous monitors and the output of the BLDS. Additionally,
standard operating procedures for the BLDS and fugitive emissions
control are required to be submitted to the Administrator for approval
in electronic format.

VII. Rationale for the Proposed Actions for the Mineral Wool Production
Source Category

    As discussed in Section VI.A of this preamble, we evaluated
emissions limits

for PM, COS, HF, HCl, formaldehyde, phenol and methanol at mineral wool
production facilities. This section of the preamble provides the
results of the RTR, our rationale for the proposed actions and
decisions concerning changes to the 1999 MACT rule for the Mineral Wool
Production source category.

A. What data were used for the NESHAP analyses?

    To perform the technology review and residual risk analysis for the
Mineral Wool NESHAP, we created a comprehensive dataset based on
existing and new test data provided by the 7 mineral wool facilities.
As described in Section IV.C of this preamble, the voluntary industry
survey requested available information regarding process equipment,
control devices, point and fugitive emissions, practices used to
control fugitive emissions, and other aspects of facility operations.
In addition to the industry survey, each owner/operator was asked to
submit reports for any recent emissions tests conducted at their
facility and to conduct additional emissions tests in 2010 for certain
HAP from specific processes. Pollutants tested for the mineral wool
source category in 2010 included most HAP metals, CO, PM and certain
organic HAP (formaldehyde, phenol, methanol and carbonyl sulfide).

B. What are the proposed decisions regarding surrogacy relationships?

    In the 1999 MACT rule, PM serves as the surrogate for metal HAP36
at existing and new cupolas, CO serves as the surrogate for COS at new
cupolas and formaldehyde serves as the surrogate for phenol and
methanol from curing ovens. The 1999 MACT standard does not have
emissions limits for COS, HCl or HF from existing cupolas; limits for
phenol or methanol from curing; or emissions limits for any pollutants
from collection operations. We are proposing HAP-specific emission
limits for these pollutants under CAA section 112(d)(3)in this action.
The agency is retaining use of PM as a surrogate for HAP metals. As
discussed in Sections III.B and VII.B. of this preamble, the Court
found that the EPA must set emission limits for each listed HAP (Sierra
Club v. EPA, 479 F. 3d 875 (DC Cir. March 13, 2007)),\3\ and agreed
with the EPA that nothing in the CAA suggests that it is prohibited
from resetting the MACT floors in order to correct our own errors. They
also agreed that the approach our petitioners labeled ``MACT-on-MACT''
would be more accurately described as ``MACT-on-Unsupportable-
Standards-Erroneously-Labeled-as-MACT'' \37\. With regard to the
evaluation of potential MACT limits for HAP metals from this source
category, consistent with the explanation presented in the proposal of
the 1999 MACT rule (NESHAP for Mineral Wool Production, Proposed Rule,
June 1, 1997, 64 FR 29490) for this source category describing the
appropriateness of PM as a surrogate for HAP metals, we continue to
consider PM as an appropriate surrogate for HAP metals in the proposed
amendments to the NESHAP in this action.
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    \36\ The HAP metals emitted from mineral wool cupolas include
antimony, arsenic, beryllium, cadmium, chromium, cobalt, mercury,
manganese, nickel, lead and selenium.
    \37\ Sierra Club v. EPA, 167 F. 3d 658 (DC Cir. March 2, 1999).
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    The agency is proposing emissions limits for phenol and methanol
because the concentration of formaldehyde in a specific binder
formulation is independent of phenol and/or methanol. The mineral wool
industry commented during the small business advocacy review that the
binder ingredients and formulation can vary from one mineral wool
company to the next, and that the test data from one company is not
necessarily relevant for or representative of another company.
    In summary, under 112(d)(3) we are proposing emission limits for
COS, HF and HCl from cupolas; and for formaldehyde, methanol and phenol
from bonded lines.

C. What are the proposed decisions regarding certain unregulated
emissions sources?

    In the course of evaluating the Mineral Wool Production source
category, we identified certain HAP for which we failed to establish
emission standards in the original MACT. See National Lime v. EPA, 233
F. 3d 625, 634 (DC Cir. 2000) (the EPA has ``clear statutory obligation
to set emissions standards for each listed HAP''). Specifically, we
evaluated emissions standards for COS, HF and HCl for cupolas and
formaldehyde, phenol and methanol for curing ovens and collection
operations at mineral wool production facilities, that are not
specifically regulated in the existing 1999 MACT standard. We are
proposing emissions limits for these pollutants and processes pursuant
to 112(d)(2) and 112(d)(3) as discussed in Section V.A of this
preamble.

D. What are the proposed decisions regarding subcategorization?

    The EPA collected information from the mineral wool companies that
operate bonded lines to better understand the different equipment
designs and whether all collection processes are the same, or whether
design and manufacturing process differences warranted consideration of
subcategories for the collection process. This process led to the
identification of three distinct process design subcategories:
Vertical, horizontal and drum. Because collection processes only emit
HAP if they occur on a bonded line, we are proposing to bundle
collection operations and curing ovens together for each of three
subcategories and propose new emissions limits for formaldehyde,
phenol, and methanol at combined collection/curing on bonded lines. The
following discussion involves the rationale for subcategorization of
collection operations into three subcategories:
1. The Vertical Collection Design
    During the production of wool fiberglass on a bonded production
line using a vertical collection design, the molten rock/slag mixture
is poured from the cupola spout onto a group of stainless steel drums
spinning in opposite directions. The spinning drums form fine fibers of
the mineral mixture. High air volume directs the fibers off the
fiberization spinners toward a fast-moving porous vertical conveyor
belt. A strong vacuum is drawn on the opposite side of the belt causing
the fibers to lie against the vertical belt as it moves upward. At the
top of the conveyance, the belt travels around a curve, the vacuum is
released, and the fibers are moved onto a second belt that conveys the
layer of binder-sprayed mineral wool fibers into the curing oven.
Because the conveyor belt is vertical, the air volume drawn through the
belt and fiber layer must be very high and the resulting fiber layer
that is collected on the belt is thin. In this design, `shot' (BB-sized
black granules that are high in iron as a result of using slag from the
iron and steel industry) falls out of the fiber layer. The vertical
design is used to produce a specific type of mineral wool that is low
in `shot' and may be used in the hydroponic gardening market as well as
in a specialized market of insulation products in which shot is
undesirable.
    Currently, only one facility operates this type of collection
design. Formaldehyde, phenol and methanol MACT floors for existing, new
and reconstructed sources in this

subcategory were based on emissions test runs for combined curing and
collection operations from this facility.
2. The Horizontal Collection Design
    Horizontal collection is similar to vertical collection, but
because the conveyor belt is horizontal it works with gravitational
forces. The layer of mineral wool collected on a horizontal belt is
thinner than that collected on a vertical belt, and the `shot' is not
selectively removed. The air volume that is drawn through the fiber
layer is much lower than in the vertical design, and therefore the air
stream is conducive to thermal oxidation at the hottest part of the
cupola exhaust stack or the existing thermal oxidizer on the curing
oven.
    Currently, only one facility operates this type of collection
design. Formaldehyde, phenol and methanol MACT floors for existing, new
and reconstructed sources in this subcategory were based on emissions
test runs for combined curing and collection operations from this
facility.
3. The Drum Collection Design
    In the drum collection design, fibers are drawn using a very high
volume air flow into the center of a rotating drum. The sides of the
rotating drum have small holes that allow the air flow to exit, but
which trap the fibers. The angle of the drum and the use of a vacuum
and centrifugal force pull the fibers against the inside wall of the
drum and out the end. The entire drum is enclosed and the air flow may
be vented to the hottest part of the cupola exhaust stack or to the
existing thermal oxidizer on the curing oven.
    Currently, only one facility operates this type of collection.
Formaldehyde, phenol, and methanol MACT floors for existing, new, and
reconstructed sources in this subcategory were based on emissions test
runs for combined curing and collection operations from this facility.

E. What are the results from the risk assessments performed and the
proposed decisions for the Mineral Wool Production source category?

    As described in Section V.A of this preamble, we conducted an
inhalation risk assessment for all HAP emitted from the Mineral Wool
Production source category. We also conducted multipathway screenings
for cadmium, mercury, and lead. Details of the risk assessments and
additional analyses can be found in the draft residual risk
documentation referenced in Section V.A of this preamble, which is
available in the docket for this action. The agency considered the
available health information--the MIR; the numbers of persons in
various risk ranges; cancer incidence; the maximum non-cancer HI; the
maximum acute non-cancer hazard; the extent of non-cancer risks; the
potential for adverse environmental effects; and the distribution of
risks in the exposed population (54 FR 38044, September 14, 1989)--in
developing the proposed CAA section 112(f)(2) standards for the Mineral
Wool Production source category.
1. Inhalation Risk Assessment Results for the Mineral Wool Production
Source Category
    Table 7 of this preamble provides an overall summary of the results
of the inhalation risk assessment.

                                           Table 7--Mineral Wool Production Inhalation Risk Assessment Results
--------------------------------------------------------------------------------------------------------------------------------------------------------
   Maximum individual cancer risk  (in 1 million) \1\                                       Maximum chronic non-cancer TOSHI
---------------------------------------------------------    Estimated        Estimated                    \2\
                                             Based on      population at    annual cancer  ----------------------------------   Maximum screening acute
                                            allowable      increased risk     incidence         Based on         Based on          non-cancer HQ \3\
    Based on actual emissions level         emissions     of cancer >=  1-    (cases per         actual         allowable
                                              level         in-1 million        year)       emissions level  emissions level
--------------------------------------------------------------------------------------------------------------------------------------------------------
4......................................              10            1,650           0.0004             0.04              0.1   8 (REL) 0.4 (AEGL-1, ERGP-
                                                                                1).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Estimated maximum individual excess lifetime cancer risk due to HAP emissions from the source category.
\2\ Maximum TOSHI. The highest TOSHI for the Mineral Wool Production source category is for the respiratory system.
\3\ The maximum HQ acute value of 8 is driven by emissions of formaldehyde. It is also based on a refined emissions multiplier of 3 which was used to
  estimate the peak hourly emission rates from the average rates. See section V.A. of this preamble for explanation of acute dose-response values.

    The results of the chronic inhalation cancer risk assessment
indicate that, based on estimates of current actual emissions, the MIR
could be up to 4-in-1 million, with formaldehyde primarily driving
these risks. The total estimated cancer incidence from this source
category based on actual emission levels is 0.0004 excess cancer cases
per year or one case in every 2,500 years, with emissions of
formaldehyde and arsenic compounds contributing 64 percent and 33
percent, respectively, to this cancer incidence.\38\ In addition, we
note that no persons are estimated to have cancer risks greater than
10-in-1 million, and approximately 1,650 people are estimated to have
risks greater than 1-in-1 million as a result of emissions from 1
facility. When considering the risks associated with MACT-allowable
emissions, the MIR could be up to 10-in-1 million. The maximum modeled
chronic non-cancer TOSHI value for the Mineral Wool Production source
category could be up to 0.04 with emissions of formaldehyde dominating
those impacts, indicating no significant potential for chronic non-
cancer impacts.
---------------------------------------------------------------------------

    \38\ We note that the MIR for this source category would not
change if the CIIT URE for formaldehyde had been used in the
assessment, although the total cancer incidence would decrease by 52
percent. The MIR for the source category would remain at 40 due to
Cr (VI). There is an ongoing IRIS reassessment for formaldehyde, and
future RTR risk assessments will use the cancer potency for
formaldehyde that results from that reassessment. As a result, the
current results may not match those of future assessments.
---------------------------------------------------------------------------

    Our screening analysis for worst-case acute impacts indicates the
potential for only one pollutant, formaldehyde, to exceed an HQ value
of 1 at only one facility in this source category, with a potential
maximum HQ up to 8. A refined emissions multiplier of 3 was used to
estimate the peak hourly emission rates from the average rates. Refer
to Appendix 7 of the draft residual risk document in the docket for a
detailed description of how the refined emissions multiplier was
developed for the Mineral Wool Production source category. The worst-
case acute impact estimate occurs at a facility that is located in a
rural area with a small population. Since the acute modeling

scenario is worst-case because of its confluence of peak emission rates
and worst-case dispersion conditions, and since the HQ estimates for
formaldehyde based on the AEGL-1 and ERPG-1 values for this facility
are well below 1, we are proposing to find that acute noncancer health
impacts of concern are unlikely.
    With respect to the potential for adverse environmental effects
from non PB-HAP, we note that that there is a lack of information about
specific adverse environmental effects occurring at given
concentrations of the HAP emitted by this source category. However,
given that all chronic non-cancer HQ values considering actual
emissions are less than 1 using human health reference values, we
believe that it is unlikely that adverse environmental effects would
occur at the actual HAP concentrations estimated in our human health
risk assessment.
2. Multipathway Risk Assessments and Results
    There were no exceedances of screening emissions rates for the PB
HAP emitted by the facilities in the Mineral Wool Production source
category, thus we have no concerns about potential multi-pathway risks
from this source category.
3. Facility Wide Risk Assessment Results
    For all facilities in this source category, there are no other
significant HAP emissions sources present beyond those included in the
source category. All significant HAP sources have been included in the
source category risk analysis. Therefore, we conclude that the facility
wide risks are essentially the same as the source category risks.

F. What are our proposed decisions for the Mineral Wool Production
source category based on risk acceptability and ample margin of safety?

1. Risk Acceptability
    As noted in Section V.A of this preamble, we weigh all health risk
factors in our risk acceptability determination, including the MIR; the
numbers of persons in various risk ranges; cancer incidence; the
maximum noncancer HI; the maximum acute noncancer hazard; the extent of
noncancer risks; the potential for adverse environmental effects; and
distribution of risks in the exposed population; and risk estimation
uncertainty (54 FR 38044, September 14, 1989) in developing the
proposed CAA section 112(f)(2) standards for this source category.
    Based on the inhalation risk assessment, we estimate that the
cancer risks to the individual most exposed could be up to 4-in-1
million due to actual emissions and up to 10-in-1 million due to MACT-
allowable emissions, mainly due to formaldehyde stack emissions. We
estimate that the incidence of cancer based on actual emissions is
0.0004 excess cancer cases per year or one case every 2,500 years, and
that about 1,650 people face a cancer risk greater than 1-in-1 million
due to HAP emissions from this source category. Our assessments also
indicated a low potential for HAP emissions from these sources to pose
any significant adverse environmental effects or human health multi-
pathway risks or chronic noncancer human health risks due to
inhalation. While our acute risk screening ruled out the possibility of
acute impacts of concern for all pollutants except for formaldehyde at
one facility, we ultimately concluded that the potential for acute
impacts of concern at this facility is low. The risk assessment for
this source category was largely based on facility-specific stack test
data and emissions estimates, indicating a high degree of confidence in
the results. Considering all of the above information, we are proposing
that the current risks due to actual HAP emissions from this source
category are acceptable.
    While the estimated chronic risks associated with MACT-allowable
emissions from this source category are slightly higher than risk
estimates based on actual emission levels, they are still well below
100 in one million and there are no other significant risks. Therefore,
we propose the risks due to allowable emissions are also acceptable.
2. Ample Margin of Safety
    As explained earlier in Section V of this preamble, the agency
again considers all of the health risks and other health information
considered in the first step. Beyond that information, we evaluate the
cost and feasibility of available control technologies and other
measures (including the controls, measures and costs reviewed under the
technology review) that could be applied in this source category to
further reduce the risks due to emissions of HAP identified in our risk
assessment.
    Based on our research and analyses as discussed in Section V.C of
this preamble, we have not identified any feasible control options
beyond what we are requiring in our proposed standards for emissions
sources described above, and are therefore not proposing additional
controls, under section 112(f)(2). Therefore, we are proposing that the
MACT standards for the mineral wool production source category, as
revised per above, provide an ample margin of safety to protect public
health and prevent adverse environmental effects.
    Nevertheless, we are soliciting comments and information regarding
additional control measures and work practices that may be available
and their feasibility in further reducing stack emissions of COS, HF,
HCl, formaldehyde, phenol, and methanol, or additional monitoring that
may be warranted to ensure adequate control of these emissions.

G. What are the results from the technology review and proposed
decisions?

    Based on our technology review, we believe that the reductions in
HAP emissions since promulgation of the 1999 Mineral Wool Production
MACT rule are directly related to improvements in two areas: (1)
Improvements in fabric filter control technology (e.g., improved bag
materials, replacement of older baghouses) and (2) addition of
regenerative thermal oxidizers (RTOs) and oxygen injection to control
emissions from cupolas. Additional reductions have been achieved due to
the use of low-sulfur raw materials at one facility. The RTOs and lower
sulfur raw materials are discussed above (in Section VII.C of this
preamble) since these controls and measures are relevant to development
of the MACT standards for COS and other organic HAPs under Section
112(d)(2) of the CAA, and in the beyond the floor analyses (described
in Section VII.C of this preamble) that we also do as part of the MACT
standard evaluations under Section 112(d)(2) and 112(d)(3).
    In this section, as part of our technology review, we describe
developments in development in fabric filter technologies and the
relationship to PM emissions.
    Slight improvements in fabric filter control technology are
reflected in the emissions test data collected under the industry
survey. The emissions limit for PM under the 1999 MACT rule is a
production-based limit of 0.1 pounds of PM per ton of melt for new and
existing cupolas. Based on our analysis of survey responses and test
data collected under the industry survey, this industry primarily uses
fabric filters to control emissions of metal HAP, and sources affected
by the current PM limit are achieving PM concentrations at control
device outlets that are only slightly

below the current limit (see Technology Review for the Mineral Wool
Production Manufacturing Source Category). Given fluctuations in
control device performance and mineral wool production fluctuations, we
do not believe that developments in practices, processes, and control
technologies warrant revisions to the PM limit in the 1999 MACT rule to
reflect HAP metal emissions levels achieved in practice.
    Moreover, the RBLC did not identify any practices, processes, or
control technologies applicable to the emission sources in this source
category that were not identified and evaluated during the original
MACT development.
    In summary, we have not identified any additional relevant cost-
effective developments in technologies, practices or processes since
promulgation of the MACT rule to further reduce HAP emissions.
Therefore, we are not proposing any changes to the MACT standards in
this action as a result of our technology review under Section
112(d)(6) for Mineral Wool Production.
    Additional details regarding these analyses can be found in the
following technical document for this action which is available in the
docket: Technology Review for the Mineral Wool Production Manufacturing
Source Category.

VIII. Rationale for the Proposed Actions for the Wool Fiberglass
Manufacturing Source Category

    As discussed in Section VI.B of this preamble, we evaluated
emissions limits for PM, chromium compounds, HF, HCl, formaldehyde,
phenol, and methanol at wool fiberglass manufacturing facilities. This
section of the preamble provides the results of the RTR, our rationale
for the proposed actions for the Wool Fiberglass Manufacturing source
category, and our proposed decisions concerning changes to the 1999
MACT rule.

A. What data were used for the NESHAP analyses?

    To perform the technology review and residual risk analysis for the
Wool Fiberglass Manufacturing NESHAP, we created a comprehensive
dataset based on existing and new test data provided by 26 of the 29
wool fiberglass facilities. As described in Section IV.C of this
preamble, the voluntary industry survey requested available information
regarding process equipment, control devices, point and fugitive
emissions, practices used to control fugitive emissions, and other
aspects of facility operations. In addition to the ICR survey, each
facility was asked to submit reports for any recent emissions tests
conducted and to conduct additional emissions tests in 2010 for certain
HAP from specific processes. Pollutants tested for the wool fiberglass
source category in 2010 included most HAP metals, PM, and certain
organic HAP (HF, HCl, formaldehyde, phenol, and methanol).
    As discussed in Section IV.C above, in the emissions testing for
the survey, industry requested to conduct emission testing on furnaces
they believed were representative of the other furnaces in operation.
The EPA and industry agreed that the bases for representativeness would
include a variety of factors such as processing the same materials,
producing the same products and being the same type of furnace. Furnace
construction and refractory composition were not factors that were
presented by industry as having an effect on HAP emissions, and those
factors were not used as a basis of representativeness for the
resulting data set. During analysis of the test data, the EPA
discovered high emissions of chromium compounds, including hexavalent
chromium, and that these emissions were mostly from certain furnaces
constructed of high chrome refractories.
    The Wool Fiberglass Manufacturing source category consists of 29
facilities with 80 furnaces, 54 RS manufacturing lines and less than 30
FA manufacturing lines. Since there are more than 30 furnaces and RS
lines, we based the MACT floor limits on the average emissions
limitation achieved by the best performing 12 percent of sources.
Therefore, the MACT floor for HF and HCl from glass-melting furnaces
was based on the 10 best performing furnaces; the 7 best performing RS
lines; and the 5 best performing FA lines.
    The stack test data were used to calculate the MACT floors using
the 99 percent UPL for glass-melting furnaces, RS manufacturing lines,
and FA manufacturing lines from wool fiberglass manufacturing plants.
The UPL analysis is explained in more detail in MACT Floor Analysis for
the Wool Fiberglass Manufacturing Source Category, which is available
in the docket for this proposed action. The results from the MACT floor
analysis are presented in Section VI.B of this preamble.

B. What are the proposed decisions regarding surrogacy relationships?

    A surrogate approach is used to allow for easier and less expensive
measurement and monitoring requirements. In the 1999 MACT rule for this
source category, PM serves as the surrogate for metal HAPs \39\ at
existing and new glass-melting furnaces and formaldehyde serves as the
surrogate for phenol and methanol from forming and curing at RS
manufacturing lines and forming and curing at FA manufacturing lines.
As described in Sections III.B and VIII.B in this preamble, the court
found that the EPA erred when we did not set emission limits for each
HAP emitted by industry processes in the MACT standards.\40\ Therefore,
the agency is proposing HAP-specific emissions limits for phenol and
methanol.
---------------------------------------------------------------------------

    \39\ The HAP metals emitted from wool fiberglass glass-melting
furnaces include antimony, arsenic, beryllium, cadmium, chromium,
cobalt, mercury, manganese, nickel, lead, and selenium.
    \40\ Sierra Club v. EPA, 479 F. 3d 875 (DC Cir. March 13, 2007).
---------------------------------------------------------------------------

C. What are the proposed decisions regarding certain unregulated
emissions sources?

    As discussed earlier in Section VI.B of this preamble, we
identified certain HAP for which we failed to establish emission
standards in the original 1999 MACT. In the 1999 MACT rule, we used
formaldehyde as a surrogate for phenol and methanol, and we did not
establish HAP-specific emission limits for phenol, methanol, HF and
HCl. For this action we evaluated emissions standards for HF, HCl,
phenol, and methanol at wool fiberglass manufacturing facilities,
described below, that are not specifically regulated in the existing
1999 MACT standard. The EPA is therefore proposing to set emissions
limits for these HAP emissions, under CAA section 112(d)(3) in this
action.

D. What are the results from the risk assessments and analyses and the
proposed decisions for the Wool Fiberglass Manufacturing source
category?

    An inhalation risk assessment was completed for all HAP emitted for
the Wool Fiberglass Manufacturing source category. Details of the risk
assessments and additional analyses can be found in the residual risk
documentation referenced in Section V.A of this preamble. The agency
considered the available health information--the MIR; the numbers of
persons in various risk ranges; cancer incidence; the maximum non-
cancer HI; the maximum acute non-cancer hazard; the extent of non-
cancer risks; the potential for adverse environmental effects; and
distribution of risks in the exposed population (54 FR 38044, September
14, 1989)--in developing the proposed CAA section 112(f)(2) standards
for the Wool

Fiberglass Manufacturing source category.
1. Inhalation Risk Assessment Results for the Wool Fiberglass
Manufacturing Source Category
    Table 8 of this preamble provides an overall summary of the results
of the inhalation risk assessment.

                                        Table 8--Wool Fiberglass Manufacturing Inhalation Risk Assessment Results
--------------------------------------------------------------------------------------------------------------------------------------------------------
    Maximum individual cancer risk (in 1 million) \1\                                       Maximum chronic non-cancer TOSHI
---------------------------------------------------------    Estimated        Estimated                    \2\
                                             Based on      population at    annual cancer  ----------------------------------   Maximum screening acute
                                            allowable      increased risk     incidence         Based on         Based on          non-cancer HQ \3\
    Based on actual emissions level         emissions     of cancer >=  1-    (cases per         actual         allowable
                                              level         in-1 million        year)       emissions level  emissions level
--------------------------------------------------------------------------------------------------------------------------------------------------------
40.....................................              60          849,000             0.05              0.2              0.5   30 (REL) 2 (AEGL-1, ERPG-
                                                                                1).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ Estimated maximum individual excess lifetime cancer risk due to HAP emissions from the source category. Hexavalent chromium is the primary driver
  for cancer risk.
\2\ Maximum TOSHI. The highest TOSHI for the Wool Fiberglass Manufacturing source category is for the respiratory system.
\3\ The maximum HQ acute value of 30 is driven by emissions of formaldehyde. See section V.A. of this preamble for explanation of acute dose-response
  values.

    The results of the chronic inhalation cancer risk assessment
indicate that, based on estimates of current actual emissions, the
maximum individual lifetime cancer risk (MIR) could be up to 40-in-1
million. The major contributor to this cancer risk is hexavalent
chromium that is emitted from the furnace refractory brick. The
greatest amount of hexavalent chromium emitted from a single source is
from a facility that currently uses a type of refractory brick that is
made almost entirely of chromium compounds. In addition, we note that
approximately 12,000 people are estimated to have cancer risks greater
than 10-in-1 million as a result of formaldehyde and hexavalent
chromium emissions at 2 facilities, and approximately 849,000 people
are estimated to have risks greater than 1-in-1 million as a result of
formaldehyde and hexavalent chromium emissions from 15 facilities. The
maximum estimated chronic non-cancer TOSHI value for the Wool
Fiberglass Manufacturing source category is 0.2 with emissions of
formaldehyde dominating those impacts, indicating no significant
potential for chronic non-cancer impacts.
    Based on the acute REL to assess possible acute non-cancer effects
due to emissions of formaldehyde, our analysis indicates that the
maximum acute HQ value could exceed a value of 1 at a total of 7
facilities due to formaldehyde emissions,\41\ with one facility in this
source category indicating the potential to create a maximum worst-case
HQ value up to 30. This maximum worst-case acute impact corresponds to
a maximum HQ of 2 based on the AEGL-1 and ERPG-1 levels for
formaldehyde. Altogether, these results indicate that we cannot rule
out the potential for formaldehyde emissions from this source category
to cause acute impacts of mild concern, such as eye and nose
irritation. Repeated exposures to these levels (i.e., at or above the
AEGL-1 and ERPG-1) could cause further health concerns.
---------------------------------------------------------------------------

    \41\ Individual facility acute HQ values for all facilities can
be found in Appendix 6 of the risk assessment document that is
included in the docket for this proposed rulemaking.
---------------------------------------------------------------------------

    With respect to the potential for adverse environmental effects
from non PB-HAP, we note that that there is a lack of information about
specific adverse environmental effects occurring at given
concentrations for the HAP emitted by this source category. However,
given that all chronic non-cancer HQ values considering actual
emissions are less than 1 using human health reference values, we
believe that it is unlikely that adverse environmental effects would
occur at the actual HAP concentrations estimated in our human health
risk assessment.
2. Auxiliary Risk Characterization
    As indicated in Section VIII.D.1 above, the MIR for the Wool
Fiberglass Manufacturing source category could be up to 40-in-1-million
based on actual emissions. The major contributor to this cancer risk is
hexavalent chromium. The greatest amount of risk is from one facility
that uses a type of refractory brick that is described by the company
as ``high chrome.''12 13 ((Notes of April 14, 2011,
Certainteed); (Region 7 Certainteed Notes).
    Because the use of high chrome refractories extends the life of the
furnace from a maximum of 10 years to at least 15 years, and the cost
of furnace construction is increased by about 15 percent when it is
reconstructed using high chrome refractories \12\ (Notes of April 14,
2011, Certainteed) we believe that there is a financial incentive for
other facilities to switch to this high chromium refractory at the time
they rebuild their furnaces. For this reason, we performed an auxiliary
risk characterization analysis to assess the potential maximum
individual lifetime cancer risks in the event that the other 28 Wool
Fiberglass facilities switch to the high chromium brick. For the
auxiliary risk characterization analysis it was assumed that the
hexavalent chromium emissions for each facility would be the same as
that for the facility with annual emissions of 420 lbs of hexavalent
chromium per furnace. Table 9 of this preamble provides a summary of
the results of this auxiliary inhalation risk assessment.

               Table 9--Wool Fiberglass Manufacturing Auxiliary Inhalation Risk Assessment Results
----------------------------------------------------------------------------------------------------------------
Potential maximum individual cancer risk (in                                       Estimated
               1 million) \1\                    Estimated        Estimated      population at      Estimated
---------------------------------------------  population at    population at    increased risk   annual cancer
                                               increased risk   increased risk    of cancer >=      incidence
       Based on actual emissions level        of cancer >=  1- of cancer >= 10-     100-in-1        (cases per
                                                in-1 million     in-1 million       million           year)
----------------------------------------------------------------------------------------------------------------
900.........................................       7,300,000          460,000            8,100             0.46
----------------------------------------------------------------------------------------------------------------
\1\ Estimated maximum individual excess lifetime cancer risk due to HAP emissions from the source category.

    The results of the auxiliary analysis indicate that, under this
scenario, the estimated emissions from 14 facilities could lead to
maximum individual lifetime cancer risks greater than 100-in-1-million,
with the highest emitting facility posing a potential maximum
individual risk of 900-in-1-million. Under this scenario, 8,100 people
would be exposed to risks greater than 100-in-1-million, 460,000 people
would be exposed to risks of greater than 10-in-1-million, and over 7
million people would be exposed to cancer risks of greater than 1-in-1-
million.
    In summary, the auxiliary risk analysis indicates that if other
facilities switch to high chromium refractory, emissions of hexavalent
chromium could potentially pose unacceptable risks to public health due
to inhalation exposures resulting from stack emissions of hexavalent
chromium.
3. Multipathway Risk Assessments and Results
    None of the facilities in the Wool Fiberglass Manufacturing source
category reported emissions of PB HAP that were greater than the
screening emission rates. Therefore, multi-pathway exposures and
environmental risks were deemed negligible.
4. Facility Wide Risk Assessment Results
    For this source category, there are no other significant HAP
emissions sources present beyond those included in the source category.
All significant HAP sources have been included in the source category
risk analysis. Therefore, we conclude that the facility wide risk is
essentially the same as the source category risk and that no separate
facility wide analysis is necessary.

E. What are our proposed decisions for the Wool Fiberglass
Manufacturing source category based on risk acceptability and ample
margin of safety?

1. Risk Acceptability
    As noted in Section VIII.D of this preamble, we weigh all health
risk factors in our risk acceptability determination, including the
MIR; the numbers of persons in various risk ranges; cancer incidence;
the maximum noncancer HI; the maximum acute noncancer hazard; the
extent of noncancer risks; the potential for adverse environmental
effects; and distribution of risks in the exposed population; and risk
estimation uncertainty (54 FR 38044, September 14, 1989) in developing
the proposed CAA section 112(f)(2) standards for this source category.
    Based on the inhalation risk assessment, we estimate that the
cancer risks to the individual most exposed could be up to as 40-in-1
million due to actual emissions and up to as 60-in-1 million due to
MACT-allowable emissions, mainly due to formaldehyde and chromium stack
emissions. We estimate that the incidence of cancer based on actual
emissions is 0.05 excess cancer cases per year or one case every 20
years, and that about 850,000 people face a cancer risk greater than 1-
in-1 million due to the HAP emissions from this source category.
    Our assessments also indicate a low potential for HAP emissions
from these sources to pose any significant adverse environmental
effects, human health multi-pathway effects, or chronic noncancer human
health risks. Our acute risk screening ruled out the possibility of
acute impacts of concern for all pollutants but one, formaldehyde, at
seven facilities, with a maximum worst-case HQ estimated to be 30 based
on the REL and 2 based on the AEGL-1 (or ERPG-1, which is equivalent).
While this means we cannot rule out the potential for acute concerns
due to formaldehyde emissions from these facilities, we note that the
use of formaldehyde is being phased out in this industry, and will be
eliminated from all but 2 facilities in the source category. Since the
cancer risks due to actual and allowable emissions (based on the
current composition of refractory bricks used by this source category)
are well within the acceptable range (i.e., less than 100-in-1 million)
and since we have no additional significant concerns regarding other
potential human health or environmental impacts, we are proposing that
the current risk levels due to actual and MACT-allowable emissions are
acceptable.
2. Ample Margin of Safety Analysis and Proposed Decisions
    As described above, we are proposing that the risks associated with
the actual and MACT-allowable stack emissions from this source category
are acceptable based on the current composition of refractory bricks
used by this source category. However, as discussed in Section
VIII.D(2) of this preamble, if other wool fiberglass facilities
reconstructed their furnaces with high chromium refractory bricks, the
maximum individual cancer risks would be higher and likely result in a
finding of unacceptable risks.
    According to our 2-step process for assessing risks, after we
evaluate whether risks are ``acceptable'' we evaluate whether cost
effective measures are available to reduce risks further, to provide an
``ample margin of safety.'' As stated in Section VIII.F of this
preamble, both NaOH scrubbers and a furnace rebuild are considered cost
effective when hexavalent chromium levels are high. NaOH scrubbers
achieve at least 95 percent reduction in hexavalent chromium emissions
at other industries. Transferring this technology to the wool
fiberglass industry is reasonable and would reduce hexavalent chromium
to levels that would achieve an ample margin of safety. Therefore, we
are proposing emission limits of 0.06 lb of total chromium compounds
per thousand tons (or 60 lb of total chromium compounds per million
tons) of glass pulled in this action (as presented in Table 10) under
Section 112(f)(2) of the CAA in this action. We believe this limit
would achieve an ample margin of safety to protect public health and
prevent adverse environmental effects.

 Table 10--Proposed Emissions Limits for Glass-Melting Furnaces Based on
                               Risk Review
------------------------------------------------------------------------
                                                           Pounds of
                                                         pollutant per
                      Pollutant                        thousand tons of
                                                             melt:
------------------------------------------------------------------------
Chromium compounds..................................               0.06
------------------------------------------------------------------------

    These emission limits apply to furnaces at major sources in the
wool fiberglass manufacturing source category. However, there are no
differences in furnaces at major sources and area sources. We are
concerned about the levels of hexavalent chromium that can be emitted
by area sources where furnaces may be constructed using high chrome
refractories. Therefore we plan to collect additional information from
industry to inform regulation of area sources in a future action.
    The emission limits we are proposing for chromium compounds under
112(f)(2) are identical to the chromium compounds limits we are
proposing under 112(d)(6), as described in Section VIII.F of this
preamble.
    Our assessments also indicate a low potential for HAP emissions
from these sources to pose any significant adverse environmental
effects, human health multi-pathway effects, or chronic noncancer human
health risks. Our acute risk screening ruled out the possibility of
acute impacts of concern for all pollutants but one, formaldehyde, at
seven facilities, with a maximum worst-case HQ estimated to be 30 based
on the REL and 2 based on the AEGL-1 or ERPG-1, which is equivalent
(formaldehyde). While this means we cannot rule out the potential for
acute concerns due to formaldehyde emissions from these facilities, we
note that the worst-case acute HQs are based on conservative
assumptions (e.g., worst-case meteorology coinciding with peak short-
term one-hour emissions from each emission point, with a person located
at the point of maximum concentration during that hour). Moreover, the
use of formaldehyde is being phased out in this industry, and will be
eliminated from all but 2 facilities in the source category. Since the
cancer risks due to actual emissions are well within the acceptable
range (i.e., less than 100 in 1 million) and since we have no
additional significant concerns regarding other potential human health
or environmental impacts, and since we have not identified any
additional cost-effective controls to further reduce formaldehyde
emissions, we are proposing that the MACT rule along with all the
proposed amendments described above (including the emissions limits for
chromium and formaldehyde) will provide an ample margin of safety to
protect public health and prevent adverse environmental effects.
    We are soliciting comments and information regarding additional
control measures, work practices that may be available, and their
feasibility in further reducing emissions of formaldehyde, chromium
compounds, HCl, and HF, or additional monitoring that may be warranted
to ensure adequate control of stack emissions. We specifically request
information on other criteria on which a chromium compounds emission
limit should be based that would reduce risks from hexavalent chromium.
3. Analysis of the Resulting Risk After the Proposed Requirements Are
in Place
    We conducted an assessment to estimate the risks based on a post-
control scenario reflecting all the proposed requirements for the
emissions described above (including the proposed emissions limit for
chromium compounds). Details are provided in the Draft Residual Risk
Assessment for the Mineral Wool Production and Wool Fiberglass
Manufacturing Source Categories, EPA's Office of Air Quality Planning
and Standards Office of Air and Radiation, September 2011, which is
available in the docket to this rule.
    Table 11 of this preamble provides an overall summary of the
results of the post-control inhalation risk assessment. As compared to
Table 8, the MIR decreased from 40 in 1 million to 20 in 1 million,
primarily as a result of one facility replacing the high chrome
refractory bricks at the facilities that currently exceed the proposed
chromium standard. These estimates are based on the dataset compiled
using the industry's emissions test data from their 2010 industry
survey responses, which show three furnaces would have to reduce
chromium emissions to meet the limit in the proposed rule.

                      Table 11--Post Control Inhalation Risk Estimates for Wool Fiberglass
                                          [Result of chromium control]
----------------------------------------------------------------------------------------------------------------
                                                                                Maximum chronic
                                                 Estimated        Estimated        non-cancer        Maximum
    Maximum individual cancer risk (in 1       population at    annual cancer    TOSHI based on  screening acute
million) based on actual emissions level \1\   increased risk     incidence          actual       non- cancer HQ
                                              of cancer >=  1     (cases per    emissions level        \3\
                                                in 1 million        year)             \2\
----------------------------------------------------------------------------------------------------------------
20..........................................         282,000             0.02              0.2               30
----------------------------------------------------------------------------------------------------------------

    In addition, we estimated that the formaldehyde emissions would be
at or below the MACT standard for all facilities once this rule is
fully implemented and we are not proposing that additional control
options be implemented.
    In a letter dated June 8, 2011, the industry trade association
(NAIMA) stated that ``NAIMA can provide documentation that all major
sources have already converted or have announced plans to convert to
non-phenol formaldehyde binders. Essentially non-formaldehyde binders
are or will be used industry-wide.'' A copy of this letter has been
placed in the docket for this action (see NAIMA's Response for the
Fiberglass Industry to EPA's Formaldehyde and Collection Questions).
Based on this information and the information provided by the industry
in their 2010 survey, we estimate that 27 of the 29 wool fiberglass
manufacturing facilities will have HAP emissions below the 10 and 25
tpy thresholds and will not be subject to the major source MACT
requirements. We further estimate that there may be two facilities
manufacturing pipe insulation or heavy density insulation products that
will be major sources of HAP emissions on the compliance date of these
proposed amendments to subpart NNN. If NAIMA is correct in that
formaldehyde will be phased out by the compliance date of these
proposed amendments, we anticipate that the estimated inhalation risks
due to formaldehyde would further decrease.

    In summary, we are proposing that the MACT standard, with the
changes we are proposing in this action, will provide an ample margin
of safety and prevent adverse environmental effects.

F. What are the results from the technology review and proposed
decisions?

    Based on our technology review, we determined that there have been
advances in emissions control measures since the Wool Fiberglass
Manufacturing NESHAP was originally promulgated in 1999. Since
promulgation, we estimate that industry-wide metal HAP emissions from
process sources have been reduced by approximately 76 percent. Due to
industry's efforts to replace phenol-formaldehyde binders, more than 95
percent of formaldehyde, phenol, and methanol emissions have been
reduced (or will be by 2012). As a result actual PM (metal HAP),
formaldehyde, phenol, and methanol emissions from process sources at
all wool fiberglass manufacturing facilities are significantly lower
than are allowed under the 1999 MACT rule.
    We believe that the reductions in metal HAP emissions since
promulgation of the 1999 MACT rule are mainly directly related to
improvements in two areas: (1) Improvements in fabric filter control
technology (e.g., improved bag materials, replacement of older
baghouses) and (2) the use of electrostatic precipitators (ESPs). Our
review also indicates that high chrome refractories are a new
technology used in wool fiberglass furnaces that the available data
indicate result in an increase in emissions of chromium compounds. The
results of our analyses and our proposed decisions for these areas
under CAA section 112(d)(6) are presented in the following sections.
Based on these data, we believe that developments in practices,
processes, and control technologies warrant revisions to the 1999
NESHAP. Additional details regarding these analyses can be found in
Technology Review for the Wool Fiberglass Manufacturing Source
Category.
    The improvements in fabric filter control technology are reflected
in the emissions test data collected under the industry survey. Two
types of PM control are used in the wool fiberglass manufacturing
industry: fabric filters (baghouses) and electrostatic precipitators.
Electrostatic precipitators (ESP) may be configured as either wet ESPs
or dry ESPs. The emissions limit for PM under the 1999 MACT rule is a
production-based limit of 0.5 pounds of PM per ton of glass pulled
applicable to all glass melting furnaces. Based on our analysis of
survey responses and test data collected under the industry survey,
this industry primarily uses fabric filters to control emissions of
metal HAP, and the vast majority of sources affected by the current PM
limit are achieving PM emissions at control device outlets that are far
below the current limit. Id.
    Most, if not all, sources reported PM emissions (coming out of the
stacks after the control devices) that are less than 10 percent of the
current limit, with several sources achieving PM emissions that are two
to three orders of magnitude lower than the current limit. Based on
these data, we believe that developments in practices, processes, and
control technologies warrant revisions to the 1999 MACT rule, under
section 112(d)(6). Our analysis of emissions data provided in the
survey conducted by industry indicates that stacks equipped with a
well-performing fabric filter or ESP can achieve exhaust PM
concentrations of less than 0.014 lb/ton of glass pulled. We estimate
that all of the wool fiberglass facilities would be able to comply with
this revised limit without additional controls. We estimate that this
would result in small reductions of metal HAP emissions since there
will only be a couple of facilities subject to the PM limits and the
available data on some of the furnaces at those facilities indicates
they are currently meeting the proposed PM emission limit. We do not
anticipate additional energy use associated with this revised limit.
Furthermore, we do not anticipate any adverse non-air environmental
impacts associated with the implementation of this revised limit.
Therefore, we are proposing that reducing the PM limit in the NESHAP
from 0.50 lb of PM per ton of glass pulled to 0.014 lb of PM per ton of
glass pulled (see Table 12) is both feasible and cost effective.
Therefore, we are proposing a revised PM limit in the NESHAP of 0.014
lb of PM per ton of glass pulled in this action. We have based these
statements on information we received from the industry in their survey
responses; nevertheless, we are seeking comment on our estimation that
all wool fiberglass manufacturers can meet the PM emission limits
without additional controls.
    We conducted a review of the available test data for chromium
compounds including hexavalent chromium emissions from glass furnaces.
We found that for most furnaces, measured emissions were near or below
detection limits of the methods used for testing (EPA Method 29
followed by EPA Method 0061). In contrast, the chromium emissions for a
few furnaces were several orders of magnitude higher than the rest of
the industry. The facility emitting the highest level of hexavalent
chromium, at 840 lb/yr, advised us that the reason chromium tested very
high was due to the refractory products, high chrome refractories, from
which the furnaces are constructed (Notes of April 14, 2011,
Certainteed) \12\. Based on the emissions testing and information on
high chrome refractories, we believe changes to the 1999 MACT rule are
warranted under CAA section 112(d)(6).
    The data indicate that well performing wool fiberglass furnaces
emit small amounts of chromium compounds, that is, they emit less than
0.06 pounds of chromium compounds (Cr) per thousand tons of glass
pulled. However, three facilities currently operate furnaces that emit
chromium in excess of this rate. Chromium emissions from these high
emitters range from 9 to 840 lb/yr. Furnaces operating below this rate
generally emit less than 1 pound per year; many of these tested below
the detection level of the test method. The data indicate that there is
a `break' between the furnaces emitting less than the proposed limit
and those emitting greater amounts of chromium. Data further indicate
there are no wool fiberglass manufacturers with low glass production
rates but high levels of chrome emissions. We are therefore proposing
to set a chromium compounds emission limit of 0.06 lb of chromium per
thousand tons of glass pulled as shown in Table 12.
    Under section 112(d)(6), we are proposing this emission limit for
chromium compounds taking into account the developments in practices,
processes and technology by the wool fiberglass industry since
promulgation of the 1999 MACT standard. The emission limits we are
proposing for chromium compounds under 112(d)(6) are identical to the
chromium compounds limits we are proposing under 112(f)(2), as
described in Section VIII.E of this preamble.
    We estimate that the 2 remaining major source wool fiberglass
facilities would be able to comply with this chromium compounds
emission limit. We estimate that if the high chromium emitting
facilities remain major sources, these new emission limits would result
in annual reductions of 1,155 pounds of chromium compounds,
specifically hexavalent chromium and there will be no reductions at the
remaining facilities because data indicate they are currently meeting
the proposed chromium emission limit.

    Wet scrubbers are not generally in use in this industry. However,
we evaluated their use to achieve reductions in hexavalent chromium for
furnaces emitting chrome above the levels being proposed. Sodium
hydroxide (NaOH) scrubbers are in use for furnace operations at other
industries for chromium compounds reduction. We have evaluated the use
of NaOH scrubbers for the wool fiberglass manufacturing industry and
find that the control technology can be adapted for use in the wool
fiberglass industry from the chromium electroplating industry and from
certain high temperature metallurgical industries.\42\
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    \42\ NaOH Scrubber Information. Telephone discussion and emails
between vendors, companies, and EPA. Steffan Johnson, Measurement
Policy Group, USEPA/OAQPS/SPPD.
---------------------------------------------------------------------------

    We do anticipate an additional energy use associated with this
revised limit if sources choose to install NaOH scrubbers to remove
hexavalent chromium from the furnace gases. We anticipate the affected
sources may incur disposal costs of hexavalent chromium contaminated
materials associated with the implementation of this emission limit. We
anticipate that two sources which currently emit chromium at levels
slightly higher than the proposed limit will be able to meet it by