[Federal Register: December 28, 2005 (Volume 70, Number 248)]
[Rules and Regulations]
[Page 76917-76935]
[DOCID:fr28de05-20]

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Part II

Environmental Protection Agency

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40 CFR Part 63

National Emission Standards for Hazardous Air Pollutants for
Industrial, Commercial, and Institutional Boilers and Process Heaters:
Reconsideration; Final Rule

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[OAR-2002-0058; FRL-8011-5]
RIN 2060-AM97

National Emission Standards for Hazardous Air Pollutants for
Industrial, Commercial, and Institutional Boilers and Process Heaters:
Reconsideration

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule, amendments; notice of final action on
reconsideration.

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SUMMARY: EPA is promulgating amendments to the national emission
standards for hazardous air pollutants (NESHAP) for industrial,
commercial, and institutional boilers and process heaters which EPA
promulgated on September 13, 2004. After promulgation of the final rule
for boilers and process heaters, the Administrator received petitions
for reconsideration of certain provisions in the final rule. On July
27, 2005, EPA published a notice of reconsideration and requested
public comment on certain aspects of the health-based compliance
alternatives, as outlined in 40 CFR 63.7507 and appendix A to the final
rule (40 CFR part 63, subpart DDDDD). After evaluating public comment
on the notice of reconsideration, we are retaining the health-based
compliance alternatives in the final rule in substantially the same
form. However, we are making a limited number of amendments to 40 CFR
63.7507 and appendix A to the final rule to improve and clarify the
process for demonstrating eligibility to comply with the health-based
compliance alternatives contained in the final rule.

DATES: The final rule amendments are effective on February 27, 2006.

ADDRESSES: EPA has established a docket for this action under Docket ID
No. EPA-OAR-2002-0058. All documents in the docket are listed in on the
http://www.regulations.gov Web site. Although listed in the index, some

information is not publicly available, i.e., CBI or other information
whose disclosure is restricted by statute. Certain other information,
such as copyrighted materials, is not placed on the Internet and will
be publicly available only in hard copy form. Publicly available docket
materials are available either electronically through
http://www.regulations.gov or in hard copy form at the Air and Radiation

Docket, Docket ID No. EPA-OAR-2002-0058, EPA/DC, EPA West, Room B102,
1301 Constitution Ave., NW., Washington, DC. The Public Reading Room is
open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding
legal holidays. The telephone number for the Public Reading Room is
(202) 566-1744, and the telephone number for the Air and Radiation
Docket is<PHONE_NUMBER>.

FOR FURTHER INFORMATION CONTACT: For information concerning
applicability and rule determinations, contact your State or local
representative or appropriate EPA Regional Office representative. For
information concerning rule development, contact Jim Eddinger,
Combustion Group, Emission Standards Division (C439-01), U.S. EPA,
Research Triangle Park, North Carolina 27711, telephone number (919)
541-5426, fax number<PHONE_NUMBER>, e-mail address:
<EMAIL_ADDRESS>

SUPPLEMENTARY INFORMATION: Regulated Entities. Categories and entities
potentially regulated by this action include:

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             Category                 SIC code       NAICS code                          Examples of potentially regulated entities
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Any industry using a boiler or                 24             321  Manufacturers of lumber and wood products.
 process heater in the final rule.             26             322  Pulp and paper mills.
                                               28             325  Chemical manufacturers.
                                               29             324  Petroleum refiners and manufacturers of coal products.
                                               30   316, 326, 339  Manufacturers of rubber and miscellaneous plastic products.
                                               33             331  Steel works, blast furnaces.
                                               34             332  Electroplating, plating, polishing, anodizing, and coloring.
                                               37             336  Manufacturers of motor vehicle parts and accessories.
                                               49             221  Electric, gas, and sanitary services.
                                               80             622  Health services.
                                               82             611  Educational Services.
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    Worldwide Web (WWW). In addition to being available in the docket,
an electronic copy of the final rule is also available on the WWW
through the Technology Transfer Network (TTN). Following signature, a
copy of the final rule will be posted on the TTN policy and guidance
page for newly proposed or promulgated rules at the following address:
http://www.epa.gov/ttn/oarpg. The TTN provides information and

technology exchange in various areas of air pollution control.
    Judicial Review. Under section 307(b)(1) of the CAA, judicial
review of the final rule amendments to the NESHAP is available by
filing a petition for review in the U.S. Court of Appeals for the
District of Columbia Circuit by February 27, 2006. Only those
objections that were raised with reasonable specificity during the
period for public comment may be raised during judicial review. Under
section 307(b)(2) of the CAA, the requirements that are the subject of
the final rule amendments may not be challenged later in civil or
criminal proceedings brought by EPA to enforce these requirements.
    Background Information Document. EPA proposed and provided notice
of the reconsideration of the NESHAP for industrial, commercial, and
institutional boilers and process heaters on June 27, 2005 (70 FR
36907), and received 35 comment letters on the proposal. A memorandum
``National Emission Standards for Hazardous Air Pollutants for
Industrial, Commercial, and Institutional Boilers and Process Heaters,
Summary of Public Comments and Responses to Reconsideration of the
Final Rule,'' containing EPA's responses to each public comment is
available in Docket No. OAR-2002-0058.
    Organization of this document: The information presented in this
preamble is organized as follows:

I. What is the statutory authority for the final rule?
II. Background
III. What revisions were made as a result of the reconsideration?
    A. Adoption of a Weighted Average Stack Height Metric for
Appendix A to the Final Rule
    B. Correction Regarding Sources That May Demonstrate Eligibility
for Health-Based Compliance Alternatives
    C. Review of Eligibility Demonstrations by Permitting Agencies
    D. Clarification of Eligibility Criteria
    E. Timeline for New or Reconstructed Sources To Submit
Preliminary Submission of Eligibility

    F. Requirement for Title V Permit Conditions
    G. Health-Based Alternative for Manganese Emissions and Total
Selected Metals Standard
IV. What are the responses to significant comments?
    A. Methodology and Criteria for Demonstrating Eligibility for
the Health-based Compliance Alternatives
    B. Tiered Risk Assessment Methodology
    C. Look-up Tables
    D. Site-Specific Risk Assessment
    E. Background Concentrations and Emissions From Other Sources
    F. Health-Based Compliance Alternative for Metals
    G. Deadline for Submission of Health-Based Applicability
Determinations
    H. Proposed Corrections to the Health-Based Compliance
Alternatives
    I. Review of Eligibility Demonstrations and Relationship With
Title V
    J. Miscellaneous
V. Impacts of the Final Rule
VI. Statutory and Executive Order (EO) Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From
Environmental Health and Safety Risks
    H. Executive Order 13211: Actions That Significantly Affect
Energy Supply, Distribution or Use
    I. National Technology Transfer and Advancement Act
    J. Congressional Review Act

I. What is the statutory authority for the final rule?

    Section 112 of the Clean Air Act (CAA) requires EPA to list
categories and subcategories of major sources and area sources of
hazardous air pollutants (HAP) and to establish NESHAP for the listed
source categories and subcategories. Industrial, commercial and
institutional boilers (ICI), and process heaters were listed on July
16, 1992 (57 FR 31576). Major sources of HAP are those that have the
potential to emit greater than 10 tons per year (tpy) of any one HAP or
25 tpy of any combination of HAP.

II. Background

    On September 13, 2004 (69 FR 55218), we promulgated the NESHAP for
ICI boilers and process heaters pursuant to section 112 of the CAA.
Under section 112(d) of the CAA, the NESHAP must reflect the maximum
degree of reduction in emissions of HAP that is achievable, taking into
consideration the cost of achieving the emissions reductions, any non-
air quality health and environmental impacts, and energy requirements.
This level of control is commonly referred to as maximum achievable
control technology (MACT). However, section 112(d)(4) of the CAA also
states that ``[w]ith respect to pollutants for which a health threshold
has been established, the Administrator may consider such threshold
level, with an ample margin of safety, when establishing emissions
standards under this subsection.''
    We proposed standards for ICI boilers and process heaters on
January 13, 2003 (68 FR 16660). The preamble for the proposed rule
described the rationale for the proposed rule and solicited public
comments. We requested comment on incorporating various risk-based
approaches (based on section 112(d)(4) and other provisions of the CAA)
into the final rule to reduce the cost of regulatory controls on those
facilities that pose little risk to public health and the environment.
(See 68 FR 1688-1693.) Industry trade associations, owners/operators of
boilers and process heaters, State regulatory agencies, local
government agencies, and environmental groups submitted comments on the
proposed risk-based approaches. We received a total of 218 public
comment letters on the proposed rule during the comment period. We
summarized major public comments on the proposed risk-based approaches,
along with our responses to those comments, in the preamble to the
final rule (69 FR 55239) and in the comment response memorandum,
``Response to Public Comments on Proposed Industrial, Commercial, and
Institutional Boilers and Process Heaters NESHAP (Revised)'' which was
placed in the docket for the final rule.
    In the final rule, we adopted health-based compliance alternatives
for the hydrogen chloride (HCl) emission limit and the total selected
metals (TSM) emission limit, based on our authority under section
112(d)(4) of the CAA. Affected sources that successfully demonstrate
that they are eligible for the HCl health-based compliance alternative
are not required to demonstrate compliance with specific HCl emissions
limits in table 1 to the final rule, but are still subject to operating
and monitoring requirements in the final rule (subpart DDDDD of 40 CFR
part 63). Affected sources that demonstrate eligibility for the health-
based compliance alternative for TSM are still subject to a technology-
based (MACT) TSM emission limit and operating and monitoring
requirements in the final rule (subpart DDDDD of 40 CFR part 63) except
that they may demonstrate compliance with this TSM emission limit based
on the sum of emissions for seven metals, instead of the eight selected
metals, by excluding manganese emissions.
    The methodology and criteria for affected sources to use in
demonstrating eligibility for the health-based compliance alternatives
were promulgated in appendix A to subpart DDDDD of 40 CFR part 63. (See
69 FR 55282.) Appendix A specifies the process units and pollutants
that must be included in the eligibility demonstration, the emissions
testing methods, the criteria for determining if an affected source is
eligible, the risk assessment methodology (look-up table analysis or
site-specific risk analysis), the contents of the eligibility
demonstration, the schedule for submission of the self-certified
eligibility demonstrations, and the methods for ensuring that an
affected source remains eligible. For an affected source to be eligible
for the health-based compliance alternatives, the owner/operator of the
source must conduct a risk assessment, as described in appendix A to
the final rule, and submit the risk assessment, also called the
eligibility demonstration, to the permitting authority along with a
signed certification that the assessment is an accurate depiction of
the affected facility. To ensure the source remains eligible, federally
enforceable limits reflecting the parameters used in the eligibility
demonstration must be incorporated into its title V permit.
    Following promulgation of the final rule, the Administrator
received petitions for reconsideration pursuant to section 307(d)(7)(B)
of the CAA from the Natural Resources Defense Council (NRDC),
Environmental Integrity Project (EIP), and General Electric (GE).\1\
Under this provision, the Administrator is to initiate reconsideration
proceedings if the petitioner can show that it was impracticable to
raise an objection to a rule within the public comment period

or that the grounds for the objection arose after the public comment
period.
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    \1\ In addition to the petitions for reconsideration, two
petitions for judicial review of the final rule were filed with the
U.S. Court of Appeals for the District of Columbia by NRDC, Sierra
Club, and EIP (No. 04-1385, D.C. Cir.) and American Municipal
Power--Ohio and Ohio cities of Dover, Hamilton, Orrville,
Painesville, Shelby, and St. Marys (No. 04-1386, D.C. Cir.). The two
cases have been consolidated. Eleven additional parties have filed
petitions to intervene: American Home Furnishings Alliance, Council
of Industrial Boiler Owners, American Forest and Paper Association,
American Chemistry Council, National Petrochemical and Refiners
Association, American Petroleum Institute, National Oilseed
Processors Association, Coke Oven Environmental Task Force, Utility
Air Regulatory Group, and Alliance of Automobile Manufacturers are
intervening with regard to the health-based compliance alternatives.
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    NRDC and EIP initially requested that EPA reconsider seven issues
reflected in the final rule that they believe could not have been
practicably addressed during the public comment period. EIP also filed
a supplement to this petition which raised additional issues for
reconsideration. Together, NRDC and EIP requested reconsideration of
the following issues: (1) The adoption of ``no control'' MACT floors
for certain subcategories and pollutants; (2) establishing risk-based
alternatives on a plant-by-plant basis; (3) the existence of health
thresholds for HCl and manganese; (4) consideration of background
pollution and co-located emission sources; (5) establishing a health-
based compliance alternative for a pollutant (HCl) that serves as a
surrogate for other inorganic pollutants; (6) promulgating a health-
based compliance alternative that allows low risk sources of manganese
emissions to comply with the MACT limitations for metals without
counting manganese; (7) the procedures for demonstrating compliance
with the health-based alternatives; (8) consideration of emissions
during periods of startup, shutdown, malfunction and, (9) the cost
effectiveness of the health-based alternatives. The NRDC and EIP
petition also requested that EPA stay the effectiveness of the health-
based compliance alternatives pending reconsideration. By letters dated
January 28, 2005, we informed NRDC and EIP that we intended to grant
their joint petition for reconsideration.
    On June 27, 2005, we decided to reconsider (70 FR 36907) several of
the issues raised in the NRDC and EIP petition pertaining to certain
provisions of the health-based compliance alternatives in appendix A to
the final rule. We denied the petitioners' request to stay because in
this case, a stay was not necessary to protect the public health or
provide a more adequate timeline for compliance planning. We are
continuing to review the issue raised by GE with respect to the
emissions averaging provision of the final rule and published proposed
action on that petition on October 31, 2005 (70 FR 62264).\2\
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    \2\ GE requested reconsideration of the emissions averaging
provisions of the final rule to address how this provision might
apply in the context of emissions units that vent to a single stack.
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    In the June 27, 2005, notice of reconsideration, we specifically
solicited comment in the following eight areas: (1) The methodology and
criteria for demonstrating eligibility for the health-based compliance
alternatives; (2) the use of a tiered analysis in appendix A to the
final rule and the application of the principles set forth in the 1994
National Academy of Sciences report, ``Science and Judgment in Risk
Assessment'' (in response to the concerns expressed by the petitioners,
we entered this document into the public docket for review); (3) the
methodology used to develop the look-up tables including average stack
heights, the use of conservative assumptions to account for other
variables such as meteorology, and the derivation of different look-up
table values based on the distance from the property line; (4) the
approach for conducting a site-specific risk assessment and the
criteria set forth in section 7 of appendix A to the final rule; (5)
the approach for selecting a hazard index (HI) and hazard quotient (HQ)
applicability cutoff value of 1.0, exclusive of background or co-
located emissions, and the deferral of further consideration of
background and co-located sources until we assess facility-wide
emissions of HAP in future residual risk actions; (6) the
appropriateness of adopting a health-based compliance alternative for
manganese and using the same TSM emission limit in table 1 to subpart
DDDDD of 40 CFR part 63 as a limitation for seven metals, while
excluding manganese from the calculation; (7) whether we should or
should not extend the deadline for submission of eligibility
demonstrations in light of this reconsidered action; and (8) proposed
corrections regarding the scope sources that are able to demonstrate
eligibility for the health-based compliance alternatives. The responses
to the significant comments received on these eight areas are discussed
later in this preamble. A comprehensive response to public comments is
also available in a document entitled ``National Emission Standards for
Hazardous Air Pollutants for Industrial, Commercial, and Institutional
Boilers and Process Heaters, Summary of Public Comments and Responses
to Reconsideration of the Final Rule,'' which can be found in the
docket for this action (Docket No. OAR-2002-0058).

III. What revisions were made as a result of the reconsideration?

    We are making a limited number of amendments to 40 CFR 63.7507 and
appendix A to the final rule to improve and clarify the process for
demonstrating eligibility to comply with the health-based alternatives
contained in the final rule. Overall, however, we are retaining the
health-based compliance alternatives in substantially the same form.

A. Adoption of a Weighted Average Stack Height Metric for Appendix A to
the Final Rule

    Sections 4 and 6 of appendix A to the final rule have been modified
to incorporate procedures for calculating a weighted average stack
height metric for use in a look-up table analysis. Equation 3 was added
to section 6 to calculate a weighted average stack height for
determining the maximum allowable HCl-equivalent emission rate in table
2 to the final rule. Equation 4 was also added to section 6 to
calculate a weighted average stack height for determining the maximum
allowable manganese emission rate in table 3 to the final rule.
    The amendments made to incorporate the weighted average stack
height metric also required conforming modifications to the format of
equations 1 and 2 of appendix A to the final rule. Equation 1 in
section 4 of appendix A was amended to clarify the calculation of the
maximum hourly emissions.

B. Correction Regarding Sources That May Demonstrate Eligibility for
Health-Based Compliance Alternatives

    We revised the text of 40 CFR 63.7507(a) and the title of appendix
A to the final rule to clarify that all subpart DDDDD, 40 CFR part 63,
sources subject to HCl and TSM emission limits may demonstrate
eligibility for the health-based compliance alternatives, not just
large solid fuel-fired units.

C. Review of Eligibility Demonstrations by Permitting Agencies

    Sections 10 and 11 of appendix A to the final rule have been
amended to explicitly state that eligibility demonstrations may be
reviewed by permitting agencies (i.e., EPA or any State, local, or
tribal agency that has been delegated title V permitting authority) to
verify that they meet the requirements of appendix A and are
technically sound. To accommodate this addition and to clarify appendix
A, we also moved some of the provisions in sections 9 and 10 of
appendix A to different sections.
    We also amended section 6 of appendix A to the final rule to
clarify that a look-up table analysis may not be used for the
eligibility demonstration if the permitting authority determines it is
not appropriate based on site specific factors. A site specific
analysis under section 7 of appendix A would be required in these
circumstances.

D. Clarification of Eligibility Criteria

    With respect to site-specific compliance demonstration, we revised
sections 5(c)(2) and (d)(2) of appendix A to the final rule to clarify
the locations where hazards must be assessed. The phrase ``where people
live'' has been changed to indicate that hazards must be assessed where
people live or congregate (e.g., including locations such as schools or
daycare centers). We also reworded other parts of these two paragraphs
to better express our original intent.

E. Timeline for New or Reconstructed Sources To Submit Preliminary
Submission of Eligibility

    We amended section 9(c)(1) of appendix A to the final rule to
specify when new or reconstructed sources that start up after the
effective date of subpart DDDDD, 40 CFR part 63, must submit a
preliminary eligibility demonstration. New or reconstructed sources
must submit this preliminary eligibility demonstration at the same time
that the source submits an application for approval of construction or
reconstruction.

F. Requirement for Title V Permit Conditions

    In conjunction with other revisions to section 10 of appendix A to
the final rule discussed above, we moved the existing requirement that
sources submit certain parameters for incorporation into a title V
permit into section 8 to appendix A to the final rule and clarified
that the proposed permit conditions must be submitted at the same time
as the rest of the eligibility demonstration. Section 8, which
addresses the contents of the eligibility demonstration, is a more
natural and logical place to include this requirement. We also expanded
the list of parameters that should be considered for inclusion as
enforceable permit limits.

G. Health-Based Alternative for Manganese Emissions and Total Selected
Metals Standard

    We are retaining the health-based compliance alternative to the TSM
standard for sources that can demonstrate eligibility based on
emissions of manganese. However, we are modifying the language in 40
CFR 63.7507(b) and related parts of appendix A to the final rule
slightly to clarify that eligible sources are subject to two
alternative requirements--one is the health-based compliance
alternative for manganese emissions in appendix A and the other is an
alternative MACT emissions limitations for seven selected metals set
forth in 40 CFR 63.7507(b).
    With respect to manganese emissions, an eligible source must
satisfy the requirements of appendix A to the final rule, which include
the requirement to submit, for incorporation as conditions in the title
V permit, the parameters that make the affected source eligible for the
health-based alternative. Compliance with these and other appendix A
requirements for manganese represents compliance with the health-based
alternative for these manganese emissions.
    However, the remaining seven metals that are covered by the
technology-based TSM standard must continue to meet a technology-based
standard based on MACT. Thus, we are retaining the existing requirement
that eligible sources comply with the TSM limit in table 1 to the final
rule based on the sum of seven metals rather than eight. Using the same
methodology we used to develop the TSM MACT limitation for eight
metals, we derived an alternative MACT limitation for seven metals for
the final rule promulgated on September 13, 2004. This alternative
applies only to those sources that demonstrate eligibility for the
health-based alternative for manganese emissions. Because our MACT
methodology yielded the same MACT standard for both seven and eight
metals, we expressed the alternative MACT standard for seven metals as
a requirement to comply with the standard in table 1 based on the sum
of seven metals instead of repeating the numerical standard in 40 CFR
63.7507(b).
    We explain our basis for these revisions further below in response
to individual comments.

IV. What are the responses to significant comments?

    We received 35 public comment letters on the proposed rule and
notice of reconsideration. Complete summaries of all the comments and
EPA responses are found in the Response-to-Comments document (see
SUPPLEMENTARY INFORMATION section). The most significant comments are
summarized below.

A. Methodology and Criteria for Demonstrating Eligibility for the
Health-Based Compliance Alternatives

    Comment: Two commenters suggested that EPA provide for flexibility
and engineering judgment by allowing an applicability cutoff HI or HQ
of greater than 1.0 in individual situations. One commenter stated that
a value of 1.0 is the most stringent margin of safety required and the
Agency could use a HI greater than 1.0 in certain cases. The commenter
added that no additional margin of safety is required because the
Reference Concentration (RfC) calculation contains many layers of
protection, including safety factors to account for uncertainty.
    One commenter suggested the use of an applicability cutoff HI or HQ
value of at most 0.5 in order to account for cumulative and persistent
risk.
    Response: We disagree that an HI or HQ value other than 1.0 should
be used as an applicability cutoff value for the health-based
compliance alternatives. HI and HQ values are based on peer reviewed
reference values such as EPA's reference concentrations (RfC). An RfC
is an estimate (with uncertainty spanning perhaps an order of
magnitude) of a continuous inhalation exposure or a daily exposure to
the human population (including sensitive subgroups) that is likely to
be without an appreciable risk of deleterious non-cancer effects during
a lifetime. An HI or HQ less than or equal to 1.0 means that the
concentration of the pollutant (in air) is less than or equal to the
reference value, and, therefore, is presumed to be without appreciable
risk of adverse health effects.
    As mentioned by commenters, RfC values contain uncertainty factors
in order to account for scientific uncertainties that are identified in
the literature. We acknowledge that EPA can consider the uncertainty
inherent in these reference values when making risk-based
determinations. For the health-based compliance alternatives in this
rule, using an HI and HQ of 1.0 as a health-protective default is
appropriate and, along with the risk assessment methods specified in
appendix A to the final rule, protects public health with an ample
margin of safety as required by CAA section 112(d)(4).
    Comment: One commenter did not support the use of a HI less than or
equal to 1.0 as the applicability cutoff value for determining
eligibility with the HCl health-based compliance alternative. The
commenter asserted that the HI should be changed to less than 10 but
greater than 1.0 due to the additive effect of several health
protective factors used for deriving the HCl HI value. Specifically,
the commenter highlighted that it is overly conservative to apply the
chlorine RfC to evaluate the exposure to chlorine. The commenter added
that chlorine reacts in the atmosphere to form HCl, and the commenter
requested EPA to evaluate the exposure to chlorine using

the equivalent amount of HCl formed in the atmospheric reactions.
    Response: As we argue above, we disagree that an HI or HQ value
other than 1.0 should be used as an applicability cutoff value for the
health-based compliance alternatives. An HI of 1.0 corresponds to a
level of pollutant exposure that is unlikely to result in adverse
health effects over a lifetime. We acknowledge that EPA can consider
the uncertainty inherent in reference values when making risk-based
determinations. However, for the health-based compliance alternatives,
using an HI and HQ of 1.0 as a health-protective default is appropriate
and helps protect public health with an ample margin of safety.
    Additionally, as stated above, we believe that it is appropriate to
apply our risk assessment methodology to the health-based alternative
compliance options in the final rule. This methodology includes
calculating hazard to the individual most exposed to pollutant
emissions from the source, which helps ensure that public health is
protected with an ample margin of safety.
    We also disagree with the commenter's suggestion to account for
atmospheric reactions of chlorine to form HCl. Impacts from chlorine
can occur shortly after release if a population lives near an emission
point. Chlorine has a lower reference value than HCl. Thus, we make the
health-protective assumption that people are exposed to chlorine
emitted from the source prior to any conversion into the less potent
HCl. This approach, along with the other requirements of appendix A to
the final rule, helps ensure that public health is protected with an
ample margin of safety.

B. Tiered Risk Assessment Methodology

    Comment: Multiple commenters supported the flexibility and
efficiency of a tiered risk assessment methodology, and these
commenters stated that the methodology set forth in appendix A to the
final rule provided an appropriate balance of conservatism and accuracy
to protect the public health with an ample margin of safety. One
commenter added that the tiered approach provides a simple,
conservative first tier analysis that companies can achieve without
hiring an outside consultant to demonstrate compliance with the health-
based compliance alternative. This commenter also feels it is necessary
to allow facilities to conduct site-specific analyses in tandem with
the look-up analysis so that facilities can still demonstrate
compliance with the health-based alternatives in the event that the
source fails the look-up analysis. Other commenters added that a tiered
approach is less arbitrary than a control-based standard, which
requires equivalent controls across the board, without considering the
risk of an affected source.
    Response: We agree with the flexible, efficient, and health-
protective nature of a two-tiered risk approach. We concluded that a
tiered risk approach is consistent with both the commenters' support
for an approach that minimizes the impact on low-risk facilities and
EPA's statutory mandate under CAA section 112.

C. Look-up Tables

    Comment: Several commenters disagreed with use of the look-up
tables because they believe there is an insufficient level of
conservatism inherent in the look-up tables during worse-case
scenarios. These commenters emphasized that if the look-up tables
remained as a result of the reconsideration, the look-up tables should
not be used when unique site-specific factors such as building
downwash, rain caps, or complex terrain occur, because these factors
are not accounted for in the look-up tables. One commenter requested
that EPA clarify that sources must comply with the MACT standard in the
event that a permitting agency rejects the use of look-up table
analysis for demonstrating eligibility with the health-based compliance
alternative.
    Response: We continue to believe that the look-up tables can
provide an efficient and cost-effective method for sources to comply
with the health-based alternative compliance options while also
protecting the public health with an ample margin of safety. However,
we agree that the protective measures inherent in the look-up tables do
not necessarily justify their use in all cases. We developed the look
up tables by running the SCREEN3 atmospheric dispersion model with
worst-case meteorology defaults, an assumption of flat terrain, an
assumption that building downwash effects are not present, and an
assumption that the plume does not encounter a raincap or other
obstruction. As several commenters identified, we recognize that site-
specific factors not accounted for in the SCREEN3 dispersion modeling,
such as building downwash, the presence of rain caps, and complex
terrain, could make the use of the tables inappropriate for some
sources. Therefore, we agree with limiting the use of the look-up
tables to those situations where the tables can conservatively
represent actual site conditions. In order to prevent the misuse of
look-up tables, we are adding language in section 6 of appendix A to
the final rule to clarify that, although the lookup tables are presumed
to be applicable in each case, permit agencies have the authority to
determine on a site-specific basis, that look-up tables may not be used
if unique site-specific factors, for which the look-up tables do not
account, make their use inappropriate. In such situations, a source
would have to demonstrate eligibility using a site-specific risk
assessment that does account for these unique factors. If a source is
unable to make this demonstration (e.g. if a permitting authority
ultimately finds the eligibility demonstration deficient on technical
grounds), the source must then comply with the technology-based
standards in the NESHAP.
    Comment: Three commenters suggested alternatives to the average
stack height metric. One commenter proposed an alternate method of four
stack height ranges which is currently used in the State's hazardous
air pollutant rule. Two commenters requested EPA to consider weighted
stack heights and cited the use of a weighted stack height metric in
the proposed amendments to the plywood NESHAP. The commenters suggested
the weighted stack height more accurately portrays the potential risk
than the average stack height metric.
    Four commenters expressed concern with the appropriateness and
accuracy of using the average stack height metric in the look-up
tables. Three of these commenters suggested limiting the use of the
look-up tables to facilities with similar stack heights to those
assumed in the model.
    One commenter disagreed with the use of the average stack height,
contending that this approach understates risk and that EPA lacked a
justification and documentation on how the EPA chose this metric.
According to this commenter, risk is understated when a calculation
averages the shortest, most-highly polluting stack located closest to
neighboring populations with another emission point that is taller,
cleaner, and farther away. The commenter also contended that there is
no documentation of the analysis or data at any step of the final
rulemaking, including this action, which supports the development of
the average stack height metric that would enable a member of the
public to evaluate EPA's methodology.
    Response: We agree that the average stack height is not the best
metric for characterizing risk, and that a more precise approach is the
weighted stack

height metric proposed in the Plywood NESHAP amendments. We are
changing the stack height metric in the boilers and process heaters
rule by adding two equations to appendix A to the final rule, similar
to the approach used for equations 3 and 4 listed in appendix B of 40
CFR part 63, subpart DDDD. Equations 1 and 2 of appendix A of 40 CFR
part 63, subpart DDDDD, will also be modified to harmonize the existing
calculations of appendix A with the new weighted stack height metric.
The complete rationale for selecting the weighted stack height metric
can be found in the amendments to the plywood NESHAP (70 FR 44021).
    There are situations where the average stack height is health
protective, (e.g. when most emissions are from the tallest stacks) and
situations where the average stack height metric is not health
protective, (e.g., when most emissions are from the shortest stacks).
The toxicity- and emissions-weighted stack height, which we are
incorporating into appendix A to the final rule, is more health
protective when most emissions are from the shortest stacks. Further,
using this more precise method does not undercut our reliance on
health-protective assumptions in the look-up table analysis when most
of the emissions come from taller stacks.
    Comment: Several commenters suggested that the use of the minimum
distance to property boundary metric is overly conservative. Two
commenters requested EPA to allow a weighted average for the distance
to property boundary when there are multiple emission units. These two
commenters argued that this metric would portray more accurate
estimates of the potential risk from facilities.
    One commenter requested that the modeling protocol for HAP should
be consistent with the modeling protocols for criteria pollutants under
the PSD protocols found at 40 CFR part 51, appendix W. The commenter
expressed concern that the current use of minimum property distance may
not be the point of maximum impact.
    Response: We disagree with changing the minimum distance to
property boundary. We recognize that the minimum distance to property
boundary may overestimate the ambient concentration and exposure;
however, we emphasize the health-protective nature of the look-up
tables and do not believe that it is appropriate to change this metric
towards one that would be uniformly less health-protective.
    It is incorrect to assert that, when performing a look-up table
analysis, the minimum distance to the property boundary may not be the
point of maximum impact. For the look-up tables, we developed the
allowable emission rate for each property boundary distance from the
maximum modeled HAP concentrations beyond that property boundary. As a
result, a look-up table analysis necessarily considers the point of
maximum pollutant impact outside the source's property boundary. This
is consistent with appendix W of 40 CFR part 51.

D. Site-Specific Risk Assessment

    Comment: Several commenters disagreed with the level of guidance
EPA provided for conducting a site-specific assessment. Three of these
commenters added that there is a lack of basic methods or required
parameters, such as the years of exposure to an individual which might
lead to basing a risk assessment on a 1-year exposure instead of the
traditional lifetime exposure. One commenter stated that while EPA has
provided some guidance on performing site-specific assessments, EPA has
a responsibility to develop constraints on the sources' discretion. The
commenter contended that the lack of constraint included in the final
rule does not provide specific, knowable, replicable, and enforceable
legal standards necessary to govern and enforce the final rule. The
commenter added that the loose guidance provided for in selecting a
site-specific assessments can be interpreted as unlimited discretion
for the affected source, and thus prevent any future efforts for
administrative challenge.
    Response: We believe that providing sources with the discretion to
use any ``scientifically-accepted, peer-reviewed risk assessment
methodology'' is appropriate. However, contrary to the assertions of
some commenters, this discretion is not unlimited. In section 7(c) of
appendix A to the final rule, EPA has established specific minimum
criteria for site-specific compliance demonstrations. In order to
demonstrate eligibility for the health-based compliance alternative,
the site-specific risk assessment conducted by the facility must meet
the following criteria: (1) Estimate long-term inhalation exposures
through the estimation of annual or multi-year average ambient
concentrations; (2) estimate the inhalation exposure for the individual
most exposed to the facility's emissions; (3) use site-specific,
quality-assured data wherever possible; (4) use health-protective
default assumptions wherever site-specific data are not available; and
(5) contain adequate documentation of the data and methods used.
    Furthermore, EPA cited the Air Toxics Risk Assessment (ATRA)
Reference Library to provide guidance to the sources and States on
developing technically sound site-specific risk assessments. The ATRA
Reference Library provides examples of how a risk assessment can be
conducted. These examples include instruction in basic risk assessment
methodology, in determining what parameters to include in a risk
assessment, and in the constraints that should be placed on those
parameters. The documents within the ATRA Reference Library have been
peer-reviewed and were developed according to the principles, tools and
methods outlined in the 1999 EPA Residual Risk Report to Congress.
However, the guidance in the ATRA Reference Library may not be
appropriate for all sources. For that reason sources may consider
alternative analytical tools as long as these alternatives are
scientifically defensible, peer-reviewed and transparent.
    Finally, the discretion of each source is not unlimited because
permitting agencies have the authority to review each site-specific
eligibility demonstration to determine if it meets the requirements in
section 7(c) of appendix A to the final rule and if the methodology, as
applied in the demonstration of eligibility, is technically sound and
appropriate. After reviewing a source's compliance demonstration, the
permitting authority makes the final determination of whether site-
specific assessments are completely and correctly submitted. These
authorities may reject site-specific assessments if they do not meet
the requirements of section 7 of appendix A or if they contain
technical flaws with respect to the risk assessment methodology. Thus,
it may be advisable for sources to seek prior approval when using a
methodology that deviates from the approach in the ATRA Reference
Library. However, we do not feel that it is necessary to require this
prior approval.

E. Background Concentrations and Emissions From Other Sources

    Comment: Multiple commenters disagreed with EPA's decision not to
include background or co-located emissions when determining whether or
not a facility qualifies for the health-based compliance alternative
standards in the final rule. Several commenters stated that when
evaluating whether or not a facility is eligible to comply with the
health-based compliance alternatives, the background or co-located
emissions should be included in the risk determination.

    Several of the commenters that opposed consideration of emissions
from background or co-located sources argued that the statutory
language in CAA section 112(d) does not provide EPA with the legal
authority to consider emissions from other source categories. Many of
these commenters also provided counter-examples of sections of the CAA
where the Congressional intent was focused on including background or
co-located emissions. Several commenters added that background or co-
located emissions do not fall into a source category or subcategory of
major sources listed for regulation. Two commenters stated that there
is no precedent for the consideration of background or co-located
emissions during the promulgation of the benzene NESHAP or during the
litigation of the vinyl chloride NESHAP.
    Three commenters cited a 1990 Senate Report, and concluded that the
consideration of background or co-located emission sources would be the
kind of lengthy study Congress intended to avoid. Two commenters cited
risk documents from the Presidential/Congressional Commission on Risk
Assessment and Risk Management, and a paper written by the Residual
Risk Coalition to support their position on excluding background and
co-located emission sources when evaluating whether or not a facility
qualifies for the health-based alternative standard in appendix A to
the final rule.
    One commenter argued that the public health is most protected when
regulations are specific to a source category and provided examples of
how the different provisions of the CAA account for different sources
of HAP. The commenter added that the consideration of background
emissions would over-regulate the affected source category and
effectively require certain sources to compensate for other sources of
HAP.
    Two of the commenters that supported considering emissions from
background and co-located sources contended that the major source
status is based on facility-wide emissions and limiting the risk
analysis to certain sources within the facility presents an unrealistic
view of the facility's impact. One commenter added that EPA must meet
its duty of providing for an ``ample margin of safety'' by evaluating
the risk of background emissions now as opposed to during the residual
risk evaluation. One commenter stated that risk assessment should be
done in the context of all HAP sources at the facility and at nearby
facilities. One of these commenters disagreed with the health-based
compliance alternative for metals because it does not adjust for
facility-wide emissions
    Three commenters cited the 1996 National Air Toxics Assessment
(NATA) for support of the concern of high exposures to air toxics
throughout the country and stated a reduction in such exposures will
require a general reduction across all sources. These commenters
expressed concern that excluding background or co-located emissions
ignore cumulative risk and do not protect the public health.
    One commenter contended that the tiered risk approach used at this
State level correctly considers background emissions, in contrast to
the exclusion of these background emissions in the final NESHAP. The
commenter added that by excluding these background sources, the final
MACT rule identifies low-risk subcategories based on an unrealistic
view of the facility impact. The commenter also concluded that the
refined site-specific risk screening provides no real measure of health
impact without including background or co-located emission sources.
    Response: Based on the arguments made by several commenters and our
review of the CAA, we believe it is permissible under CAA section
112(d) to limit our analysis to establishing emissions limitations for
only those sources in the individual source categories subject to this
action. Therefore, in developing emissions limitations under section
112(d), we believe emissions from sources outside of this source
category need not be considered to determine eligibility for the health
based compliance alternatives for ICI boilers and process heaters.
Although we may combine several source categories into one NESHAP
rulemaking as we did in this action, we do not construe the CAA to
require that we regulate the emissions from all other source categories
through an individual section 112(d) rule for particular source
categories.
    The focus of section 112(d) of the CAA is on establishing emission
standards for individual source categories. Section 112(d)(1) indicates
that the administrator is to ``promulgate regulations establishing
emission standards for each category or subcategory of major sources
and area source of hazardous air pollutants listed for regulation
pursuant to subsection (c) of this section in accordance with the
schedule provided in subsections (c) and (e) of this section.'' The
health-based compliance alternatives are included among the emissions
standards we have established for ICI boilers and process heaters under
section 112(d). Section 112(d)(4) states that ``the Administrator may
consider such threshold level, with an ample margin of safety, when
establishing emission standards under this subsection.'' The subsection
described in this provision of the statute is CAA subsection 112(d).
Since the ``ample margin of safety'' provision is also contained within
section 112(d), we do not interpret this part of the CAA to require
that we consider emissions from other source categories in establishing
a health-based alternative under section 112(d)(4) for one category of
sources. Based on the overall focus of section 112(d) on sources in
specific categories, we believe the ``ample margin of safety'' criteria
should be applied to the emissions of threshold pollutants from the
individual source category subject to each NESHAP rulemaking.
    We agree with several commenters that the legislative history
supports this view that Congress intended for EPA to focus only on the
emissions from sources within a particular category when establishing
health-based standards for a particular source category under CAA
section 112(d)(4). The Senate Report stated that the following:

    The Administrator is authorized by section 112(d)(4) to use the
no observable effects or NOEL (again with an ample margin of safety)
as the emissions limitation in lieu of more stringent ``best
technology'' requirements. Following this scenario, only those
sources in the category which present a risk to public health (those
emitting in amounts greater than the safety threshold) would be
required to install controls, even though the general policy is
``maximum achievable technology'' everywhere.

    This statement suggests an intent for EPA to address only whether
``sources in the category'' present a risk to public health when EPA is
determining whether individual sources in the category should have to
comply with a technology-based emissions limitation or may avoid
installation of controls by demonstrating that the emissions from a
source do not present risks greater than an established health
threshold.
    Thus, we believe it is permissible to conclude that the facility-
wide impact is not the focus of the analysis in the development of a
CAA section 112(d) rule. Under our interpretation, the appropriate
analysis under the CAA is whether the emissions of sources in the
applicable category (without consideration of emissions from sources in
other categories) are below the health threshold. Under the eligibility
demonstration methodology set forth in appendix A of subpart DDDDD of
40 CFR part 63, a source must demonstrate

eligibility based on the emissions from all units in the ICI boilers
and process heaters source category. Because all emissions units in the
category are covered, any background emissions or emissions from other
sources at a particular location would have to be emissions from
sources in other categories or emissions that occur naturally.
    We do not read CAA section 112(d) to require us to use emissions
from sources outside the category to establish health-based
alternatives for sources in the ICI boilers category. Likewise, we do
not believe eligibility for health-based alternative should be
determined by using a sum of emissions from all source categories or by
lowering the health threshold for emissions from one source category to
account for emissions from other source categories. We believe we
should concentrate on only the emissions from each source category to
establish health-based emissions limitations for that category and in
determining whether sources in that category are eligible to comply
with a health-based emissions limitation or must meet a technology-
based emissions limitation.
    Although a particular facility may be identified as a major source
of HAP for purposes of CAA section 112 on the basis of emissions from
affected sources in multiple source categories, this does not require
that we establish eligibility for a health-based emissions limitation
in a particular source category based on emissions from co-located
sources outside the category. Emissions units in other source
categories located at the same major source site remain subject to the
technology-based emissions limitations contained in other NESHAP
rulemaking promulgated under section 112(d). The sources covered by
these NESHAP rules are not eligible to comply with the health-based
alternatives in the ICI boilers and process heaters NESHAP because an
ICI boiler or process heater at the same site is eligible for the
health-based alternative in the NESHAP for ICI boilers and process
heaters.
    Under either scenario, each source is subject to regulatory
requirements (whether health or technology-based) that address the
health risks posed by emissions from that facility. The health-based
compliance alternatives in the 40 CFR part 63, subpart DDDDD, are only
available for HCl and manganese, and only if emissions of these HAP
meet the health-based criteria defined in appendix A to the final rule.
Affected sources that can comply with the health-based alternatives in
appendix A are still subject to other emissions standards under the
NESHAP.
    With respect to the concerns about cumulative risk, emission
standards under CAA section 112(d) are only one aspect of a broader
national air toxics control program. Under the residual risk program,
we may consider, as appropriate, risks from other source categories and
risks from the total emissions from a particular location. This
approach was reiterated in the recently finalized Coke Oven Residual
Risk rule where we said we will only consider emissions from the
regulated source category when determining ``acceptable risk'' during
the first step of the residual risk analysis. However, during the
second step, where we determine the ample margin of safety considering
costs and technical feasibility (70 FR 19997), we may consider co-
located sources and background levels where appropriate.
    Comment: Three commenters agreed with the Agency suggestion to
revisit the consideration of background emission during future residual
risk evaluations. However, one commenter disagreed with the suggestion
to revisit facility-wide residual risk determinations in future
residual risk rules and stated that EPA does not have the authority to
mandate facility-wide residual risk determinations. The commenter
provided an attachment of the Coke Oven Residual Risk rule to support
their position. Several commenters stated an intention to address this
issue in subsequent residual risk rulemakings if EPA proposes to
revisit facility-wide emissions at this stage.
    Four commenters expressed concern on considering co-located
emissions only during the residual risk analysis. One commenter stated
that deferring the risk screening acts is contrary to the intent of the
CAA. Three commenters were not satisfied with the residual risk
evaluations performed to date. Two commenters specifically cited that
background concentrations for benzene or any other HAP were not
incorporated into the Coke Oven Residual Risk report. One commenter
added that EPA must meet its duty of providing for an ``ample margin of
safety'' by evaluating the risk of background emissions now as opposed
to during the residual risk evaluation. The commenter added that in
deferring the consideration of these background emission sources until
the residual risk evaluation, the agency is acting arbitrary,
capricious, and otherwise not in accordance with law.
    Response: To the extent necessary, we believe the appropriate stage
for considering total facility risk from air toxics emissions is at the
residual risk rulemaking stage under section 112(f) of the CAA. As
noted above, we do not construe the requirement in CAA section
112(d)(4) to ``consider such threshold, with an ample margin of safety,
when establishing emission standards'' under CAA subsection (d) to
require assessment of the cumulative risk at a given location due to
the emissions from all source categories at this stage of NESHAP rule
development. However, as stated in our recent residual risk rule for
coke ovens, we do not agree that CAA section 112(f) entirely precludes
EPA from considering emissions other than those from the relevant
source category during a residual risk rulemaking analysis for an
individual source category. (70 FR 19992, 19998; April 15, 2005)
Section 112(f) of the CAA directs EPA to consider whether promulgation
of additional standards ``is required to provide an ample margin of
safety to protect public health.''
    Although the phrase ``ample margin of safety'' is used in both CAA
sections 112(d)(4) and 112(f), the context surrounding the phrase is
different in each section. The context of CAA subsection 112(d) focuses
on each individual source category for which we are promulgating a
NESHAP rulemaking under CAA subsection (d). Although we agree that the
first stage of our section 112(f) analysis should focus on the risks
from each individual source category, we believe we may consider
cumulative risks to some extent in implementing the ``ample margin of
safety'' requirement in the context of CAA subsection (f) and in
evaluating ``other relevant factors'' under this subsection. (70 FR at
19998). As a result, we believe the appropriate stage for any
consideration of cumulative facility risks is this second part of the
residual risk analysis rather than in the development and
implementation of a health-based alternative under section 112(d)(4) of
the CAA.
    We do not construe section 112(d)(4) of the CAA to accelerate the
residual risk analysis under CAA section 112(f) when we invoke section
112(d)(4) to establish a health-based standard during the first stage
or rulemaking under section 112(d). In this action, we are implementing
section 112(d) and are not writing a regulation based on section
112(f). Section 112(d)(4) does not call for a residual risk analysis
for all sources in the category. Rather, this provision allows EPA to
consider the existence of health thresholds (with an adequate margin of
safety) for particular pollutants at the first stage of the NESHAP
promulgation process.

    Comment: Two commenters felt it was unclear how the health-based
compliance alternatives will affect CAA section 112(f) residual risk
evaluations for HCl and manganese, and asked if these two threshold
pollutants will be exempted from residual risk assessments.
    Response: HCl and manganese will not be exempted in future CAA
112(f) analyses. Rather, exposure to these two pollutants will be
assessed along with exposure to other HAP emitted from the source
category.

F. Health-Based Compliance Alternative for Metals

    Comment: Multiple commenters agreed with EPA's method for
evaluating manganese and the basis of excluding manganese from the TSM
emission limit for units that comply with the manganese health-based
compliance alternative. These commenters also stated that the health-
based compliance alternative adequately protects the public health. One
commenter cited EPA re-analysis of the MACT floor based on seven
instead of eight metals, and concluded that because manganese was only
about 5 percent of the TSM, the MACT floor remained the same.
    Several commenters disagreed with the appropriateness and
lawfulness of the manganese health-based compliance alternative. Three
commenters stated that EPA has not provided a justifiable explanation
for the exclusion of manganese from the calculation of TSM. The
commenters contended that although EPA found the MACT floor to be the
same whether or not manganese was included in the floor analysis, this
reasoning does not justify removing manganese from the TSM limit. One
commenter stated the mechanism through which the manganese compliance
alternative operates unlawfully allows plants with low manganese
emissions to avoid controlling the emissions of other non-mercury
metals. Further, the commenter suggested that the top-performing
sources used to calculate the MACT floor may have low manganese
emissions because existing controls at the source may reduce manganese
emissions, such that the TSM emission limit would not be affected by
the incorporation of manganese concentrations. The commenter emphasized
that dirtier sources would also be allowed to exclude manganese from
their TSM limit calculations and as a result be allowed to emit higher
levels of manganese and the other seven metals included in the TSM
standard.
    Response: We believe the alternative TSM emissions limit for
sources that qualify for the health-based alternative is technically-
sound and supported by the record. The alternative emissions limitation
set forth in 40 CFR 63.7507(b) subpart DDDDD, is a MACT (technology-
based) standard for seven metals (excluding manganese). This
alternative MACT emissions limit is applicable only to those sources
who qualify for the health-based compliance alternative for TSM based
on their emissions of manganese. The manganese emissions from these
sources are subject to the health-based alternative standard, which is
enforceable through the operating conditions in the title V permit of
sources that successfully demonstrate eligibility for the health-based
alternative. However, the remaining seven metals that are included in
the TSM calculation must still be subject to a MACT (technology-based)
emissions limit. As a result, we derived an alternative MACT emissions
limit for these seven selected metals using the same MACT methodology
that we used for other emissions limits in subpart DDDDD. Only sources
that qualify for the health-based alternative for TSM are eligible to
apply this alternative TSM MACT limit in 40 CFR 63.7507(b) because the
manganese emissions are otherwise controlled to health-based levels
through the operating conditions in the title V permit established
pursuant to appendix A to the final rule.
    The methodology for the MACT floor analysis conducted for
establishing this alternative, technology-based TSM limit is described
in the memorandum ``MACT Floor Analysis for the Industrial, Commercial,
and Institutional Boilers and Process Heaters National Emission
Standards for Hazardous Air Pollutants'' in the docket. When we
investigated the possibility of establishing an alternative TSM
emission limit for these seven metals, we performed the same MACT floor
analysis that we conducted for the TSM emission limit for eight metals.
That is, we reexamined the emission test data for solid fuel units that
included emissions results for all of the eight total selected metals
(arsenic, beryllium, cadmium, chromium, lead, manganese, nickel, and
selenium) with manganese removed from the summation. The technology-
based TSM limit for these seven metals (excluding manganese) resulted
in a MACT floor emission level for existing large solid fuel units of
0.001 pound per million British thermal units (lb/mmBtu). This is the
same level as the eight-metal (including manganese) TSM MACT emission
level proposed and promulgated for existing large solid fuel units. Our
MACT floor analysis for new solid fuel units achieved the same result.
Thus, rather than repeating the emissions limit already contained in
table 1 to the final rule in 40 CFR 63.7507(b), we expressed the
alternative, technology-based TSM limit for these seven metals for
eligible sources as a requirement to meet the same emissions limitation
without counting manganese.
    The seven-metal and eight-metal technology-based TSM limit were the
same because the manganese emissions from the unit serving as the basis
for the limit only accounted for less than 5 percent of the total
selected metals. When we conducted our MACT floor analysis for the
seven metals standard, we determined that the unit we used as the basis
for the setting the TSM limit for eight metals was the same as the unit
selected under the analysis for seven metals.
    We understand, but do not agree with commenters concerns that
allowing sources to exclude manganese from their TSM limit calculation
will result in higher emissions of the other seven metals. Based on the
available data, we do not expect sources other than biomass-fired
sources to qualify for the health-based alternative for manganese and
TSM. The record does not indicate that sources using biomass fuels emit
significant quantities of metals other than manganese. Thus, while in
theory the exclusion of manganese from the TSM limitation could allow
an eligible source to increase emissions of the other seven metals, the
record does not indicate that eligible sources are capable of doing so.
    The TSM limit in the final rule was included at proposal because
the Agency was sensitive to the fact that some sources burn fuels (e.g,
biomass) that contain very little metals but have sufficient
particulate matter (PM) emissions to require control under the PM
provision of the final rule. In these cases, we did not think that PM
would be an appropriate surrogate for metallic HAP. Under the rules in
subpart DDDDD of 40 CFR part 63, a source may choose to comply with the
alternative TSM emission limit instead of the PM limit. The eight
metals included in the TSM summation represent the most common and the
largest emitted metallic HAP from boilers and process heaters. Based on
the impacts analysis done for the final rule, the TSM emission limit
would minimize the impacts on small entities (e.g., furniture industry,
sugar cane industry) since

some of the potential small entities burn biomass.
    Biomass (e.g., wood, bagasse, peanut hulls, etc.) generally does
not contain measurable amounts of metals except for manganese. For
example, fuel analyses of bagasse from sugar cane mills in Louisiana
did not detect any of the metals except for manganese. Fuel analyses of
bagasse from sugar cane mills in Florida only detected manganese, lead,
and selenium, with lead and selenium totaling 0.00032 lb/mmBtu, and
this is assuming that all the metals in the fuel is emitted which would
not be the case due to some remaining in the bottom ash. Wood also
contains little metals except for manganese. Fuel analyses of wood
combusted as fuel at three furniture facilities detected only
manganese. Fuel analysis at another furniture facility did detect
cadmium, chromium, and nickel beside manganese, but the total of those
three metals (0.00005 lb/mmBtu) was only 1.3 percent the level of
manganese or 5 percent of the TSM limit. Other biomass materials, such
as peanut hulls, used as fuel also have similar metals composition.
Fuel analysis conducted by EPA on peanut hulls only detected the
presence of manganese.
    The metal makeup of biomass differs greatly from coal. Coal
contains detectable levels of all eight metals. Fuel analyses from six
coal-fired facilities indicate that even if a coal-fired facility could
demonstrate eligibility with the TSM health-based compliance
alternative and may exclude manganese emissions, it would still require
high efficient PM control to achieve the TSM limit. Thus, when we
promulgated the TSM health-based compliance alternative, we believed,
and still believe that only biomass units will seek to demonstrate that
they do not need to employ PM controls by showing they qualify to
exclude manganese from the TSM compliance demonstration, since
manganese is the principal metal in biomass while manganese only makes
up a small fraction of the metals contained in coal.
    Comment: One commenter stated that EPA cannot adopt risk-based
exemptions for pollutants for which no health threshold has been
established. The commenter contended, based on documents in EPA's
Integrated Risk Information System (IRIS), that no health threshold has
been established for manganese. On the contrary, two commenters
specified that manganese has long been recognized as a threshold
pollutant. Another commenter stated that unlike other metals in the
MACT list, manganese is not a carcinogen, rather it is a Class D
pollutant.
    Response: We agree that health-based compliance alternatives
adopted under section 112(d)(4) of the CAA can apply only to pollutants
for which a threshold for health effects has been established. For the
pollutants for which we have elected to establish health-based
compliance alternatives (manganese and HCl), the scientific data
support a threshold approach to evaluating the potential for adverse
health effects.
    For air toxics risk assessments, we identify pertinent toxicity or
dose-response values using a default hierarchy of sources to assist us
in identifying the most scientifically appropriate benchmarks. EPA's
IRIS is the preferred source in this hierarchy. The values in the IRIS
database reflect EPA consensus values and their development typically
incorporates extensive peer review. When adequate toxicity information
is not available in IRIS, we consult other sources in a default
hierarchy that recognizes the desirability of peer review and
consistency with EPA risk assessment guidelines to ensure that we have
consistent and scientifically sound assessments. For substances lacking
current IRIS assessments, U.S. Agency for Toxic Substances and Disease
Registry (ATSDR) chronic minimal risk levels received next preference,
followed by California Environmental Protection Agency (CalEPA) chronic
reference exposure levels and unit risk estimates. Furthermore, when
there is an IRIS assessment but that assessment substantially lags the
current scientific knowledge, we are committed to consider alternative
credible and readily available assessments.
    Based on our analysis of manganese using this approach, we believe
the data currently available show that a health threshold has been
established for manganese and that we are therefore authorized under
CAA section 112(d)(4) to establish a health-based alternative for this
pollutant. Under our default hierarchy approach, we first consulted
IRIS. IRIS may be found on Internet at http://www.epa.gov/iris, but we have

added the relevant pages in IRIS to the docket for this rulemaking
action. As listed in table 4 of the preamble to the rule (68 FR 1690;
Jan. 13, 2003), IRIS contains a reference concentration for manganese.
However, IRIS does not contain a unit risk estimate, which addresses
cancer risk. EPA's assessment in IRIS indicates that there is
inadequate evidence of carcinogenicity for manganese. In addition, a
cancer assessment for manganese is not available from any of the other
sources in our default hierarchy or from another scientifically-
credible source. Based on this information, which we believe is the
best available at the present time, our judgment is that it is only
appropriate for EPA to evaluate manganese with regard to non-cancer
effects. In the absence of specific scientific evidence to the
contrary, it has been our policy to classify non-carcinogenic effects
as threshold effects. RfC development is the default approach for
threshold (or nonlinear) effects. Thus, in the absence of adequate
evidence that manganese is a carcinogen and based on the presence of a
reference concentration in IRIS for non-cancer effects of manganese,
our best scientific judgment at this time is that manganese is a
threshold pollutant. We also used this approach to reach a similar
conclusion with respect to HCl. (See Comment-Response Document, pg. 233
(February 2004.)
    Regarding the lowest observable adverse effect level issue, the
methodology employed by EPA recognizes that while a no observable
adverse effect level is preferable to a LOAEL for use as the point of
departure to which uncertainty factors are applied to derive an RfC, a
LOAEL may also be used. (U.S. Environmental Protection Agency. 1994.
Methods for Derivation of Inhalation Reference Concentrations and
Application of Inhalation Dosimetry. Office of Research and
Development. EPA/600/8-90/066F.) IRIS incorporates factors to account
for uncertainties in the scientific database. The use of a LOAEL to
derive the RfC for manganese is one of these uncertainties and is
appropriately addressed through the application of uncertainty factors
as part of the IRIS process.
    We disagree with the commenter that we did not consider acute
effects. We performed a risk assessment evaluating the potential acute
effects of boiler emissions, including manganese (see docket item
OAR-2002-0058-0608). We used acute inhalation reference
values, taken from the table on EPA's air toxics Web site (http://www.epa.gov/ttn/atw/toxsource/table2.pdf
), for all pollutants in this assessment.

Although the commenter is correct that this table does not contain an
acute exposure guidelines level (AEGL) value for manganese compounds,
the table does contain an immediately dangerous to life and health
(IDLH)/10 value of 50 mg/m3. This is the acute dose-response value that
we used, as reflected in table 3 (converted to 50000 ug/m3)
of the screening assessment memorandum (OAR-2002-0058-0608). Thus, the
commenter's assertion that the table on the Web site contains no acute
dose-response value or that EPA does not know what that value might be
is

incorrect. As described in the screening assessment memorandum, for HAP
with more than one acute dose-response value, the most health-
protective value was chosen. EPA has not prioritized these values.
Since we only had one value for manganese, we used that value in our
acute assessment. The results indicate that HAP emissions, including
manganese, from the industrial boilers source category are unlikely to
pose acute risks to human health.

G. Deadline for Submission of Health-Based Applicability Determinations

    Comment: Numerous commenters did not deem it as necessary for the
Agency to extend the deadline for the submission of eligibility or
final compliance dates provided that certain timelines and components
of the health-based compliance alternatives were maintained as a result
of this reconsideration.
    Several commenters requested that the Agency consider including an
extension of at least 1 year to both the submission of eligibility and
final compliance dates in the final rule. These commenters added that
the uncertainties resulting from the reconsideration and ongoing
litigation made the original deadlines impractical.
    One commenter disagreed with extending the submission of
eligibility demonstration or compliance dates of affected sources under
any circumstances. The commenter contended that an extension will only
further delay the installation of the pollution controls that are
required by the CAA. The commenter added that it is unlawful to extend
compliance dates of affected sources.
    Response: We do not believe it is appropriate at this time to
adjust the deadline for submitting eligibility demonstrations. Most
commenters representing the regulated industry believed that they would
not need an extension if EPA met certain conditions.
    EPA has met the conditions outlined by these commenters. We have
completed the reconsideration in a timely manner and have not made
significant changes to the rule. As stated in the notice of
reconsideration as proposed (70 FR 36913), we did not anticipate that
significant revisions would be made as a result of the reconsideration,
and we advised affected sources to ``proceed to prepare their
eligibility demonstrations under the existing process promulgated in
the final rule.'' Although we are making some clarifying amendments, we
are not changing the final rule substantially. Thus, this action will
not have the impact on the eligibility-demonstration process that
concerned several other commenters. Therefore, we do not believe an
extension is necessary in order for sources to complete their
eligibility demonstrations by September 2006.
    In addition, we do not have cause to extend the compliance date for
existing sources. Section 112(i)(3)(A) of the CAA specifies that NESHAP
for existing sources can have compliance dates of no more than 3 years.
For the ICI boiler and process heater NESHAP, EPA provided the maximum
3 years for covered sources to comply with the new standards.
    It is not unusual for promulgation of CAA standards to be followed
by litigation or petitions for reconsideration. Section 307(b)(1) of
the CAA specifically provides that the filing of a petition for
reconsideration of a rule does not postpone the effectiveness of a
rule. To date, EPA has not, during the pendency of a reconsideration
request, extended the compliance deadlines for promulgated MACT
standards to provide compliance periods in excess of the statutory 3-
year maximum. In contrast, where the Agency has amended a MACT standard
in a significant way, we have found it appropriate to set a new
compliance date for the rule that takes into account new requirements
not contained in the original rule.
    In this action, we are making relatively minor clarifying
amendments to the eligibility demonstration methodology for the health-
based alternatives and have not reconsidered or changed any aspect of
the technology-based MACT standards. EPA indicated in the
reconsideration notice, as proposed, that we were unlikely to change
the compliance deadline and that the petitions for reconsideration had
not provided new information suggesting a need for significant
revisions to the applicability demonstration methodology for the
health-based alternatives. (70 FR 36910, 36913) Thus, affected sources
were on notice that significant revisions to health-based alternatives
were not anticipated, Furthermore, we indicated that we intended to
complete this reconsideration action expeditiously to shorten any
uncertainty that may have been created by our partial granting of these
petitions for reconsideration. (7 FR 36910) The time required to
complete the reconsideration process has not been extraordinarily
lengthy.
    We disagree with the request to provide a blanket compliance date
extension for all sources in the category under section 112(i)(3)(B) of
the CAA. The granting of an extension under this provision is up to the
individual permitting authorities, and is restricted to specific
situations where a source can demonstrate that such time is necessary
for the installation of controls. We have not been provided with
sufficient evidence to show that all sources in the category would be
able to (or even have a need to) make such a showing.

H. Proposed Corrections to the Health-Based Compliance Alternatives

    Comment: Three commenters disagreed with the proposed correction to
extend the risk-based exemptions beyond the large solid-fuel
subcategory. These commenters believed the expansion of the health-
based compliance alternative to other subcategories to be a significant
rule change that would require a separate formal rulemaking process
with public notice and a comment period. These commenters expressed
concern that this correction will allow more sources, specifically
smaller sources with shorter stacks that tend to be located closer to
populous regions, to become eligible for the risk-based exemptions. One
commenter added that the analysis of TSM contained in the docket was
specific to large solid fuel units and not all units for which the
proposed correction seeks to offer applicability. One commenter cited
sections within the final preamble language that indicated the
alternatives applied to large solid fuel-fired sources.
    Two commenters contended that there is no technical reason why the
type of unit or fuel burned should restrict a facility from the right
to demonstrate eligibility.
    Response: We do not agree that a separate rulemaking proceeding is
necessary to adopt the proposed correction to clarify that sources in
all subcategories may demonstrate eligibility for the health-based
compliance alternatives. Although this correction was coupled with
EPA's response to a petition for reconsideration, EPA provided notice
and opportunity to comment on the proposed revisions to the text of the
final rule in accordance with the rulemaking requirements of section
307(d) of the CAA. Commenters have not cited legal authority in the CAA
or elsewhere that requires EPA to address an allegedly ``significant''
change to a rule in a separate or independent rulemaking action.
    We acknowledge that our original intent with respect to the scope
of the health-based compliance alternatives is unclear and
contradictory. EPA included language in 40 CFR 63.7507(a) that limits
the applicability of the

health-based compliance alternative for HCl to sources in the large
solid fuel-fired subcategory. We also made several statements in the
preamble, highlighted by the commenters, which indicate an intent to
limit one or both health-based alternatives to large solid fuel
sources. These statements were made because the existing solid fuel-
fired units at major sources are the main category of sources
potentially affected by the health-based compliance alternatives.
Furthermore, the number of new small solid fuel-fired units at major
sources projected in the future (see Docket OAR-2002-0058) is
relatively small. However, we also took certain actions in the final
rule which show an intent to allow sources in all subcategories to
demonstrate eligibility for the health-based compliance alternatives.
For example, we did not include language in 40 CFR 63.7507(b) that
limits the health-based alternative for TSM to sources in the large
solid fuel subcategory. Likewise, we did not include any language in
section 2 of appendix A to the final rule limiting the health-based
alternative for HCl to just sources in the large solid-fuel
subcategory. In that provision, we said that ``each new, reconstructed,
or existing source may demonstrate that they are eligible for the
health-based compliance alternatives.'' Thus, the bottom line is that
various portions of the final rule and preamble are inconsistent on the
intended scope of eligibility for the health-based compliance
alternatives.
    As a result of these inconsistencies, we proposed a correction that
would make these elements of the final rule consistent. Although we
indicated in the proposal that this correction was intended to reflect
our original intent, we agree that this terminology was imprecise.
Given the conflicting statements and regulatory text in the final rule
cited above, we concede that the Agency's original intent was not clear
one way or the other. To remedy this confusion, we are resolving the
inconsistency by eliminating regulatory language that could be read to
limit one or both of the health-based alternatives to only sources in
the large solid fuel category. Thus, we are taking the action we
proposed, which is to remove the words ``for large solid fuel boilers
located at a single facility'' from 40 CFR 63.7507(a) and the words
``Specified for the Large Solid Fuel Subcategory'' from the title of
appendix A to the final rule.
    Because large solid fuel-fired units are not the only units that
have applicable manganese and HCl MACT limits, we believe it is
technically correct, and appropriate, to allow all affected sources
with manganese and HCl limits the opportunity to demonstrate
eligibility for the health-based compliance alternatives. Where EPA has
determined that no adverse health effects are expected below a certain
threshold level of exposure, there is no reasoned basis for precluding
smaller industrial boilers and process heaters from using the health-
based compliance alternative so long as their emissions do not result
in human exposure above the designated threshold value. To the extent
we are expanding the availability of the health-based compliance
alternative to all sources, this will not subject the public to adverse
health effects.
    We do not believe health risks are increased by allowing smaller
sources to qualify for the health-based compliance alternatives, even
if the commenters are correct that these sources tend to have shorter
stacks and are closer to populous areas. The amendments we are making
in the final rule do not automatically make all small sources eligible
for the health-based compliance alternatives. Such sources must still
demonstrate eligibility under the procedures and criteria in appendix A
to the final rule, which consider stack heights and distance to
populated areas in determining eligibility. If these characteristics
indicate that a particular source has emissions that pose risks above
the threshold levels, the source will not be eligible for the health-
based compliance alternative. In addition, emissions rates are also
part of the analysis under appendix A. Because small sources have lower
emissions rates, all other things being equal, small sources present
less risk than large sources.
    We do not believe this correction to the rule requires an extensive
re-analysis of the cost or emissions reduction impacts of the health-
based compliance alternatives. We have sufficient information to
conclude that this correction will not result in a meaningful change to
the cost or emissions impacts of the final rule.
    In the final rule, the cost and economic analyses developed as part
of the final MACT rule were based on the estimated costs for all
affected sources to install, maintain, and operate controls and to
comply with MACT requirements. Costs were not based on the health-based
compliance alternatives since the cost of compliance with controls is
significantly higher than the cost to comply with the health-based
compliance alternatives. The costs associated with voluntarily
conducting risk analyses were not analyzed and, therefore, not re-
analyzed to account for this correction to the applicability of the
health-based alternatives to all affected units.
    Our supplemental analysis of the impact on control costs and
emissions reductions resulting from adoption of the health-based
alternatives cited by commenter showed that the estimated costs of the
final rule would be lower if the health-based provisions were adopted.
This ``rough assessment'' of the number of sources that would qualify
for the health-based alternatives focused on large sources because
these sources were the sources most likely to seek to demonstrate
eligibility to comply with the health-based alternatives.
    Based on the available information on sources in the category, we
do not expect this correction to enable a significant number of
additional sources to qualify for the health-based alternatives. Thus,
this correction to the final rule will not result in a dramatic
difference in our rough control cost and emissions reduction estimates.
Since we evaluated the costs of the final rule without the health-based
compliance alternatives, we have no reason to believe this amendment
will increase compliance costs above these high-end estimates. The
analysis we conducted in this reconsideration proceeding is sufficient
to enable us to conclude that compliance costs will not be
significantly different if a few additional sources are able to
demonstrate eligibility as a result of this correction. For similar
reasons, we do not have a basis to believe this change dramatically
alters the emissions reductions that will be achieved under the final
rule.
    We adopted the health-based alternatives in part to reduce the
compliance costs of the NESHAP while continuing to maintain the health
protection called for in the Clean Air Act. The potential for this
correction to reduce compliance costs further does not undermine this
reason for adopting health-based compliance alternatives. We did not
rely on these cost and emission reduction estimates as a basis for
establishing technology-based MACT emissions limitations or the
eligibility criteria for the health-based compliance alternatives. We
conducted the cost and emission reduction estimates in order to present
a summary of the environmental and economic impacts of final rule. The
estimates included in our supplemental analysis of the impact on
control costs and emissions reductions were presented in order to
provide a comparative summary of impacts of the final rule based on a
rough estimate of facilities that might opt to comply with the health-
based compliance alternatives. Additionally, these cost estimates are
necessary in order

complete several Statutory and Executive Order Reviews including: the
Paperwork Reduction Act, the Regulatory Flexibility Act, and the
Unfunded Mandates Reform Act of 1995.

I. Review of Eligibility Demonstrations and Relationship With Title V

    Comment: Several commenters pointed out that the health-based
compliance alternative is dependent on the approval from a permitting
authority via issuance of a title V permit that includes enforceable
alternative limits. These commenters stated that the proposed process
for reviewing and incorporating the health-based compliance
alternatives into the permits is unworkable because many parameters
that affect air dispersion modeling and risks are not required to be
incorporated into the title V permit.
    One commenter requested EPA to clarify in sections 9 and 10 of
appendix A to the final rule that a facility's compliance with the
health-based compliance alternatives is dependent on the approval from
a permitting authority via issuance of a title V permit that includes
the alternative limits. The commenter added, if the eligibility
determination is not approved, the facility must comply with the final
NESHAP rule requirements.
    One commenter opposed a requirement to obtain EPA or State agency
approval of the site-specific risk assessments as currently stated in
the hazardous waste combustion rule (HWC) rule. The commenter believed
that requiring approval would likely create delays in the eligibility
process and result in very short compliance timelines if a reviewing
authority rejected a site-specific assessment or did not complete the
review in a timely manner. The commenter added there is no technical
justification for requiring approval in the final HWC MACT rule and
recommended not doing so in the final boiler and process heater rule.
    Response: We agree that the preferred approach is to not require
affirmative approval by the permitting authority of each risk
assessment before a source is eligible to comply with the health-based
alternative. Thus, under the procedures in appendix A of subpart DDDDD
of 40 CFR part 63, as amended in this action, a source becomes eligible
to comply with the health-based alternatives at the time it submits an
eligibility demonstration meeting the requirements of section 8 of
appendix A to the final rule.
    However, for a source to remain eligible to comply with the health-
based alternatives the eligibility demonstration must be complete and
the application for a permit modification must ultimately be approved
by the permitting authority. Thus, as part of this process, permitting
agencies do have the authority to review eligibility demonstrations to
verify that they meet the requirements of appendix A to the final rule
and are technically sound. For example, a permitting authority may
notify a source that its eligibility demonstration is deficient if the
demonstration is incomplete or if a look-up table analysis is performed
in a situation when site-specific conditions exist that make the use of
the look-up tables inappropriate. Based upon the technical findings of
the review, permitting agencies have the authority to inform a source
that it is no longer eligible for the health-based alternative if the
eligibility demonstration is deficient. EPA will also review some
demonstrations as part of an audit program.
    This review authority derives from the title V permit program
through which the health-based compliance alternatives are implemented,
and it was inherent in the final rule when promulgated on September 14,
2004. Subpart DDDDD of 40 CFR part 63 contains applicable requirements
that are incorporated in title V permits. The title V permit program
provides a process for identifying and consolidating all of the
applicable requirements for each source. Through this process, the
permit authority reviews each application to verify the applicable
requirements for each source. Thus, when a source submits a
demonstration of eligibility for the health-based alternatives in
subpart DDDDD, the title V permitting authority has the ability to
review this submission to determine whether the applicable requirements
for that source are the health-based or the technology-based
requirements in subpart DDDDD.
    However, to clarify this issue, we are adding explicit language in
sections 10 and 11 of appendix A to the final rule to make clear that
permitting agencies may review each facility's eligibility
demonstration. If the permitting authority identifies deficiencies with
the eligibility determination or the permit modification is eventually
disapproved based on problems with the eligibility demonstration, then
the facility is no longer eligible for the health-based alternative and
must comply with the MACT emission standards by the compliance dates
specified in 40 CFR 63.7495.
    For new sources, we are establishing a slightly different procedure
because new sources will be relying upon the health-based alternative
at start-up. In these cases, the source will have a grace period of 30
to 90 days to correct any deficiencies before ceasing to be eligible
for the health-base alternative. This grace period is not needed for
existing sources because their eligibility demonstrations must be
submitted 12 months prior to the compliance date. We believe this
provides sufficient time for permitting authorities to notify sources
of any deficiencies and for a source to correct any deficiencies.
    Comment: Several commenters requested that EPA specify additional
process and non-process related parameters under section 11 of appendix
A to the final rule to clarify the enforceable requirements for the
facility. One commenter specifically requested that ``emission rate''
be added to the list of parameters. Three commenters requested that
non-process parameters that can affect air dispersion modeling be
included, such as stack height, exit gas temperature, distance to the
plant property line, and changes in RfC or land-use.
    Response: We recognize that a large number of parameters can affect
continuous compliance with the health-based compliance alternatives.
These parameters include, but are not limited to, HAP emission rates,
fuel type, type of control device, stack parameters, reference values,
and location of local residences. Some of these parameters are
appropriate for incorporation into title V permits (e.g., HAP emission
rates or a surrogate for emission rate such as production volume) while
others are not (e.g., reference values). However, changes in any of
these parameters can trigger the need for a re-assessment. Therefore,
we are adding language to appendix A to the final rule expanding the
list of parameters that should be considered for inclusion as
enforceable permit limits. In section 11 of appendix A, we are also
expanding the list of parameters that, if changes occur, could also
necessitate a re-assessment.
    Comment: Three commenters requested that EPA clarify the deadline
for compliance for sources whose health-based eligibility determination
is found to be deficient. These commenters also suggested an allowance
period of 12 months after the facility receives notice of a deficiency
in their health-based eligibility determination.
    Two commenters stated that the health-based compliance alternative
will delay compliance with MACT for sources that attempt to
unsuccessfully demonstrate eligibility with the health-based compliance
alternatives.

    Response: We disagree that there will be a delay in compliance
caused by the health-based compliance alternatives. Sources that submit
eligibility demonstrations in an attempt to comply with the health-
based compliance alternative but do so unsuccessfully must still be in
compliance within 3 years after the rule was promulgated. We do not
believe it is appropriate to automatically extend the compliance date
in these situations. As noted above, for existing sources, there is a
1-year window in which permitting authorities and sources can work out
any deficiencies in an eligibility demonstration. The health-based
compliance alternative is an optional compliance approach. Some risk is
involved in electing to comply with the MACT standard via the health-
based compliance alternatives. This assumed risk could include a
shorter amount of time to install the controls that are required to
meet technology standards in the event that a source does not submit a
health-based eligibility demonstration that meets the requirements of
Appendix A to the final rule. We do not necessarily endorse the use of
CAA section 112(i)(3)(B) to grant compliance date extensions in these
circumstances. However, we will leave the decision of whether to grant
such a compliance date extension on a site-specific basis to permitting
authorities.

J. Miscellaneous

    Comment: Two commenters addressed the vagueness of the criteria for
determining the location at which the affected source must demonstrate
that the HI for HCl and chlorine (Cl2) and the HQ for
manganese is less than or equal to 1.0. One commenter requested to
incorporate potential land use changes where people could reasonably be
expected to live in the future into the demonstrations of eligibility.
The commenter stated that the rule language ``where people live'' does
not account for the individual most exposed in the future for a
location that was not residentially zoned at the time of the risk
assessment. One commenter suggested replacing ``where people live''
with the ``point of maximum impact beyond the facility's property
boundary.''
    Response: We agree that there is a need clarify the wording of the
phrase ``where people live'' in section 5 of Appendix A. To address
some of the commenters concerns, we are changing the phrase to ``where
people live or congregate (e.g. including schools or daycares).'' We
believe that this a an appropriate approach given that, as described in
EPA's Air Toxics Risk Assessment Reference Library, sources can deviate
from the default assumption that an exposed individual remains at the
location of highest exposure for 24 hours per day, 365 days per year.
    We do not believe any additional changes are needed in section 5 of
Appendix A to account for future land use changes. The final rule
requires that a source complying with a health-based compliance
alternative must resubmit their demonstration of eligibility if process
or non-process parameters change in a way that could increase public
health risk. Thus, if people have moved into an area, or if schools or
daycare centers are constructed, the demonstration of eligibility must
be resubmitted with a new risk assessment that incorporates updated
parameters to account for the public health risk of these new
populations. This resubmission of the eligibility demonstration is part
of the existing requirements of Appendix A to the final rule for
maintaining continuous compliance. If a source is no longer in
compliance with the health-based alternative due to changes in land
use, that source must comply with the technology standards in the MACT.

V. Impacts of the Final Rule

    The revisions incorporated as a result of the final rule amendments
do not change any of the impacts presented in section V of the preamble
to the final rule which was published at 69 FR 55218 (September 13,
2004).

VI. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

    Under Executive Order 12866 (58 FR 51735, October 4, 1993), EPA
must determine whether the regulatory action is ``significant'' and,
therefore, subject to review by OMB and the requirements of the
Executive Order. The Executive Order defines ``significant regulatory
action'' as one that is likely to result in a rule that may:
    (1) Have an annual effect on the economy of $100 million or more or
adversely affect in a material way the economy, a sector of the
economy, productivity, competition, jobs, the environment, public
health or safety, or State, local, or Tribal governments or
communities;
    (2) Create a serious inconsistency or otherwise interfere with an
action taken or planned by another agency;
    (3) Materially alter the budgetary impact of entitlements, grants,
user fees, or loan programs, or the rights and obligations of
recipients thereof; or
    (4) raise novel legal or policy issues arising out of legal
mandates, the President's priorities, or the principles set forth in
the Executive Order.
    Pursuant to the terms of Executive Order 12866, it has been
determined that today's action is a ``significant regulatory action''
because it raises novel legal or policy issues. As such, the action was
submitted to OMB for review under Executive Order 12866. Revisions made
in response to OMB suggestions or recommendations are documented in the
public record (see ADDRESSES section of this preamble).

B. Paperwork Reduction Act

    Today's final rule amendments impose no new information collection
requirements on the industry. Because there is no additional burden on
the industry as a result of the final rule amendments, the information
collection request has not been revised. The Office of Management and
Budget (OMB) has previously approved the information collection
requirements contained in the existing regulations under the provisions
of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq., and has
assigned OMB control number 2060-0551 (EPA No. 2028.02). A copy of the
OMB approved Information Collection Request (ICR) may be obtained from
Susan Auby, Collection Strategies Division, U.S. Environmental
Protection Agency (2822T), 1200 Pennsylvania Ave., NW., Washington, DC
20460 or by calling<PHONE_NUMBER>.
    Burden means the total time, effort, or financial resources
expended by persons to generate, maintain, retain, or disclose or
provide information to or for a Federal agency. This includes the time
needed to review instructions; develop, acquire, install, and utilize
technology and systems for the purposes of collecting, validating, and
verifying information, processing and maintaining information, and
disclosing and providing information; adjust the existing ways to
comply with any previously applicable instructions and requirements;
train personnel to be able to respond to a collection of information;
search data sources; complete and review the collection of information;
and transmit or otherwise disclose the information.
    An Agency may not conduct or sponsor, and a person is not required
to respond to a collection of information unless it displays a
currently valid OMB control number. The OMB control numbers for EPA's
regulations are listed in 40 CFR part 9 and 40 CFR chapter 15.

C. Regulatory Flexibility Act

    EPA has determined that it is not necessary to prepare a regulatory
flexibility analysis in connection with today's final rule amendments.
    For purposes of assessing the impacts of today's final rule
amendments on small entities, a small entity is defined as: (1) A small
business having no more than 500 to 750 employees, depending on the
business' NAICS code; (2) a small governmental jurisdiction that is a
government of a city, county, town, school district or special district
with a population of less than 50,000; and (3) a small organization
that is any not-for profit enterprise which is independently owned and
operated and that is not dominant in its field.
    We conclude that the final rule amendments will not have a
significant economic impact on a substantial number of small entities.
This rule will not impose additional regulatory requirements on small
entities. After evaluating public comment on the notice of
reconsideration, we are retaining the health-based compliance
alternatives in the final rule in substantially the same form. However,
we are making a limited number of amendments to 40 CFR 63.7507 and
appendix A to the final rule to improve and clarify the process for
demonstrating eligibility to comply with the health-based compliance
alternatives contained in the rule.

D. Unfunded Mandates Reform Act

    Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public
Law 104-4, establishes requirements for Federal agencies to assess the
effects of their regulatory actions on State, local, and tribal
governments and the private sector. Under section 202 of the UMRA, EPA
generally must prepare a written statement, including a cost-benefit
analysis, for proposed and final rules with ``Federal mandates'' that
may result in expenditures by State, local, and tribal governments, in
the aggregate, or by the private sector, of $100 million or more in any
1 year. Before promulgating an EPA rule for which a written statement
is needed, section 205 of the UMRA generally requires EPA to identify
and consider a reasonable number of regulatory alternatives and adopt
the least costly, most cost effective, or least-burdensome alternative
that achieves the objectives of the rule. The provisions of section 205
do not apply when they are inconsistent with applicable law. Moreover,
section 205 allows EPA to adopt an alternative other than the least
costly, most cost-effective, or least burdensome alternative if the
Administrator publishes with the final rule an explanation why that
alternative was not adopted. Before EPA establishes any regulatory
requirements that may significantly or uniquely affect small
governments, including tribal governments, it must have developed,
under section 203 of the UMRA, a small government agency plan. The plan
must provide for notifying potentially affected small governments,
enabling officials of affected small governments to have meaningful and
timely input in the development of EPA's regulatory proposals with
significant Federal intergovernmental mandates, and informing,
educating, and advising small governments on compliance with the
regulatory requirements.
    EPA has determined that today's final rule amendments do not
contain a Federal mandate that may result in expenditures of $100
million or more for State, local, and tribal governments, in the
aggregate, or the private sector in any 1 year. Although the final rule
have annualized costs estimated to range from $690 to $860 million
(depending on the number of facilities eventually demonstrating
eligibility for the health-based compliance alternatives), today's
final rule amendments do not add new requirements that would increase
this cost. Thus, today's final rule amendments are not subject to the
requirements of sections 202 and 205 of the UMRA. In addition, EPA has
determined that the final rule amendments do not significantly or
uniquely affect small governments because there are no new requirements
that apply to such governments or impose obligations upon them.
Therefore, today's final rule amendments are not subject to section 203
of the UMRA.

E. Executive Order 13132: Federalism

    Executive Order 13132 (64 FR 43255, August 10, 1999) requires EPA
to develop an accountable process to ensure ``meaningful and timely
input by State and local officials in the development of regulatory
policies that have federalism implications.'' ``Policies that have
federalism implications'' are defined in the Executive Order to include
regulations that have ``substantial direct effects on the States, on
the relationship between the national government and the States, or on
the distribution of power and responsibilities among the various levels
of government.''
    The final rule amendments do not have federalism implications. It
will not have substantial direct effects on the States, on the
relationship between the national government and the States, or on the
distribution of power and responsibilities among the various levels of
government, as specified in Executive Order 13132. None of the affected
facilities are owned or operated by State governments, and the
requirements discussed in today's action will not supersede State
regulations that are more stringent. Thus, Executive Order 13132 does
not apply to today's final rule amendments.

F. Executive Order 13175: Consultation and Coordination With Indian
Tribal Governments

    Executive Order 13175 (65 FR 67249, November 9, 2000) requires EPA
to develop an accountable process to ensure ``meaningful and timely
input by tribal officials in the development of regulatory policies
that have tribal implications.'' ``Policies that have tribal
implications'' are defined in the Executive Order to include
regulations that have ``substantial direct effects on one or more
Indian tribes, on the relationship between the Federal government and
Indian tribes, or on the distribution of power and responsibilities
between the Federal government and Indian tribes.'' The final rule
amendments do not have tribal implications, as specified in Executive
Order 13175.
    The final rule amendments do not significantly or uniquely affect
the communities of Indian tribal governments. We do not know of any ICI
boilers or process heaters owned or operated by Indian tribal
governments. However, if there are any, the effect of these rules on
communities of tribal governments would not be unique or
disproportionate to the effect on other communities. EPA specifically
solicited additional comment on the final rule from tribal officials,
but received none. Thus, Executive Order 13175 does not apply to
today's final rule amendment.

G. Executive Order 13045: Protection of Children From Environmental
Health and Safety Risks

    Executive Order 13045 (62 FR 19885, April 23, 1997) applies to any
rule that: (1) Is determined to be ``economically significant'' as
defined under Executive Order 12866, and (2) concerns an environmental
health or safety risk that we have reason to believe may have a
disproportionate effect on children.
    If the regulatory action meets both criteria, we must evaluate the
environmental health or safety effects of the planned rule on children,
and explain why the planned regulation is preferable to other
potentially effective

and reasonably feasible alternatives we considered.
    We interpret Executive Order 13045 as applying only to those
regulatory actions that are based on health or safety risks, such that
the analysis required under section 5-501 of the Executive Order has
the potential to influence the regulation. Today's final rule
amendments are not subject to the Executive Order because eligibility
demonstrations submitted in support of the health-based alternative
compliance options will be based on noncancer human health reference
values (e.g., reference concentrations) that are designed to be
protective of sensitive subpopulations, including children.

H. Executive Order 13211: Actions That Significantly Affect Energy
Supply, Distribution, or Use

    Today's final rule amendments are not a ``significant energy
actions'' as defined in Executive Order 13211 (66 FR 28355, May 22,
2001) because it is not likely to have a significant adverse effect on
the supply, distribution, or use of energy. Further, we have concluded
that today's final rule amendments are not likely to have any adverse
energy effects.

I. National Technology Transfer and Advancement Act

    Section 12(d) of the National Technology Transfer and Advancement
Act (NTTAA) of 1995 (Pub. L. 104-113; 15 U.S.C. 272 note) directs EPA
to use voluntary consensus standards in their regulatory and
procurement activities unless to do so would be inconsistent with
applicable law or otherwise impracticable. Voluntary consensus
standards are technical standards (e.g., material specifications, test
methods, sampling procedures, business practices) developed or adopted
by one or more voluntary consensus bodies. The NTTAA requires EPA to
provide Congress, through the OMB, with explanations when EPA decides
not to use available and applicable voluntary consensus standards.
    During the development of the final rule, EPA searched for
voluntary consensus standards that might be applicable. The search
identified three voluntary consensus standards that were considered
practical alternatives to the specified EPA test methods. An assessment
of these and other voluntary consensus standards is presented in the
preamble to the final rule (69 FR 55251, September 13, 2004). Today's
final rule amendments do not involve the use of any additional
technical standards beyond those cited in the final rule. Therefore,
EPA did not consider the use of any additional voluntary consensus
standards.

J. Congressional Review Act

    The Congressional Review Act, 5 U.S.C. 801 et seq., as added by the
Small Business Regulatory Enforcement Fairness Act of 1996, generally
provides that before a rule may take effect, the agency promulgating
the rule must submit a rule report, which includes a copy of the rule,
to each House of the Congress and to the Comptroller General of the
United States. EPA will submit a report containing this action and
other required information to the U.S. Senate, the U.S. House of
Representatives, and the Comptroller General of the United States prior
to publication of the rule in the Federal Register. A Major rule cannot
take effect until 60 days after it is published in the Federal
Register. This action is not a ``major rule'' as defined by 5 U.S.C.
804(2). This rule will be effective February 27, 2006.

List of Subjects in 40 CFR Part 63

    Environmental protection, Administrative practice and procedure,
Air pollution control, Hazardous substances, Intergovernmental
relations, Reporting and recordkeeping requirements.

    Dated: December 15, 2005.
Stephen L. Johnson,
Administrator.

0
For the reasons stated in the preamble, title 40, chapter 1 of the code
of Federal Regulations is amended as follows:

PART 63--[AMENDED]

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1. The authority citation for part 63 continues to read as follows:

    Authority: 42 U.S.C. 7401, et seq.

Subpart DDDDD--[Amended]

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2. Section 63.7507 is revised to read as follows:

Sec.  63.7507  What are the health-based compliance alternatives for
the hydrogen chloride (HCl) and total selected metals (TSM) standards?

    (a) As an alternative to the requirement to demonstrate compliance
with the HCl emission limit in table 1 to this subpart, you may
demonstrate eligibility for the health-based compliance alternative for
HCl emissions under the procedures prescribed in appendix A to this
subpart.
    (b) As an alternative to the requirement to demonstrate compliance
with the TSM emission limit in table 1 to this subpart based on the sum
of emissions for the eight selected metals, you may demonstrate
eligibility for the health-based alternative for manganese emissions
under the procedures prescribed in appendix A to this subpart and
comply with the TSM emission standards in table 1 based on the sum of
emissions for seven selected metals (by excluding manganese emissions
from the summation of TSM emissions).
* * * * *

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3. Appendix A to subpart DDDDD is amended as follows:
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a. By revising the heading.
0
b. In Section 4 by revising paragraph (g).
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c. In Section 5 by revising paragraphs (c)(2) and (d)(2).
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d. In Section 6 by revising the introductory text and paragraphs (a)
and (b).
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e. In Section 8 by revising paragraphs (b)(1) and adding paragraph (d).
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f. In Section 9 by revising paragraphs (b), (c)(1) and (c)(2).
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g. Revising Section 10.
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h. Revising Section 11.

Appendix A to Subpart DDDDD--Methodology and Criteria for Demonstrating
Eligibility for the Health-Based Compliance Alternatives

* * * * *

4. How do I determine HAP emissions from my affected source?

* * * * *
    (g) You must determine the maximum hourly emission rate for each
appropriate emission point according to Equation 1 of this appendix.
An appropriate emission point is any emission point emitting HCl,
Cl2, or Manganese from a subpart DDDDD emission unit.
[GRAPHIC] [TIFF OMITTED] TR28DE05.000

Where:

Ei,s = maximum hourly emission rate for HAP i at each
emission point s associated with a subpart DDDDD emission unit j,
lbs/hr

i = applicable HAP, where i = (HCl, Cl2, or Manganese) s
= individual emission point
j = each subpart DDDDD emission unit associated with an emission
point, s
t = total number of subpart DDDDD emission units associated with an
emission point s
Ri,j = emission rate (the 3-run average as determined
according to table 1 of this appendix or the pollutant concentration
in the fuel samples analyzed according to Sec.  63.7521) for HAP i
at subpart DDDDD emission unit j associated with emission point s,
lb per million Btu.
Ij = Maximum rated heat input capacity of each subpart
DDDDD unit j emitting HAP i associated with emission point s,
million Btu per hour.

5. What are the criteria for determining if my facility is eligible for
the health-based compliance alternatives?

* * * * *
    (c) * * *
    (2) Your site-specific compliance demonstration indicates that
none of your HI values for HCl and CL2 are greater than
1.0 at locations where people live or congregate (e.g., schools,
daycare centers, etc.);
    (d) * * *
    (2) Your site-specific compliance demonstration indicates that
none of your HQ values for manganese are greater than 1.0 at
locations where people live or congregate (e.g., schools, daycare
centers, etc.).

6. How do I conduct a look-up table analysis?

    You may use look-up tables to demonstrate that your facility is
eligible for either the compliance alternative for HCl emissions
limit or the compliance alternative for the TSM emissions limit,
unless your permitting authority determines that the look-up table
analysis in this section is not applicable to your facility on
technical grounds due to site-specific variations that are not
accounted for in the look-up table analysis (e.g. presence of
complex terrain, rain caps, or building downwash effects).
    (a) HCl compliance alternative. (1) Using the emission rates for
HCl and Cl2 determined according to section 4 of this
appendix, calculate, using equation 2 of this appendix, the
toxicity-weighted emission rate (expressed in HCl-equivalents) for
each emission point that emits HCl or Cl2 from any
subpart DDDDD sources. Then, calculate the weighted average stack
height using equation 3 of this appendix.
[GRAPHIC] [TIFF OMITTED] TR28DE05.001

Where:

TWs = the toxicity-weighted emission rate (in HCl-
equivalent) for each emission point s, lb/hr.
s = individual emission points
EHCl,s = the maximum hourly emission rate for HCl at
emission point s, lb/hr
ECl2,s = the maximum hourly emission rate for
Cl2 at emission point s, lb/hr
RVCl2 = the reference value for Cl2
RVHCl = the reference value for HCl
(reference values for HCl and Cl2 can be found at http://www.epa.gov/ttn/atw/toxsource/summary.html
).

[GRAPHIC] [TIFF OMITTED] TR28DE05.002

Where:

HHCl = weighted average stack height for determining the
maximum allowable HCl-equivalent emission rate (in Table 2 to this
appendix), m.
s = individual emission points
n = total number of emission points
TWs = toxicity-weighted HCl-equivalent emission rate from
each emission point (from equation 2), lb/hr.
Hs = height of each individual stack, m
TWT = total toxicity-weighted HCl-equivalent emission
rate from the source (summed for all emission points), lb/hr.

    (2) Calculate the total toxicity-weighted emission rate for your
affected source by summing the toxicity-weighted emission rate for
each appropriate subpart DDDDD emission point.
    (3) Using the weighted average stack height and the minimum
distance between any appropriate subpart DDDDD emission point at the
source and the property boundary, identify the appropriate maximum
allowable toxicity weighted emission rate for your affected source,
expressed in HCl-equivalents, from table 2 of this appendix.
Appropriate emission points are those that emit HCl or
Cl2, or both, from subpart DDDDD units. If one or both of
these values does not match the exact values in the look-up tables,
then use the next lowest table value. (Note: If your weighted
average stack height is less than 5 meters (m), you must use the 5
meter row.) Your affected source is eligible to comply with the
health-based alternative for HCl emissions if the value calculated
in paragraph (a)(2) of this section, determined using the methods
specified in this appendix, does not exceed the appropriate value in
table 2 of this appendix.
    (b) TSM Compliance Alternative. Using the emission rates for
manganese determined according to section 4 of this appendix,
calculate the total manganese emission rate for your affected source
by summing the maximum hourly manganese emission rates for all your
subpart DDDDD units. Identify the appropriate allowable emission
rate in table 3 of this appendix for your affected source using the
weighted average stack height value and the minimum distance between
any appropriate subpart DDDDD emission point at the facility and the
property boundary. Appropriate emission points are those that emit
manganese from subpart DDDDD units. If one or both of these values
does not match the exact values in the look-up tables, then use the
next lowest table value. (Note: If your weighted average stack
height is less than 5 meters, you must use the 5 meter row.) Your
affected source is eligible to comply with the health-based
alternative for manganese emissions and may exclude manganese when
demonstrating compliance with the TSM emission limit if the total
manganese emission rate, determined using the methods specified in
this appendix, does not exceed the appropriate value specified in
table 3 of this appendix.
[GRAPHIC] [TIFF OMITTED] TR28DE05.003

Where:
HMn = weighted average stack height for determining the
maximum allowable emission rate for manganese (in table 3 to this
appendix), m.
s = individual emission points
n = total number of emission points
EMn,s= maximum hourly manganese emissions from emission
point s, lbs/hr.
Hs = height of each individual stack s
EMn,T = total maximum hourly manganese emissions from
affected source (sum emission rates from all emission points), lb/hr
* * * * *

8. What Must My Health-Based Eligibility Demonstration Contain?

* * * * *
    (b) * * *
    (1) Calculations used to determine the weighted average stack
height of the subpart DDDDD emission points that emit manganese,
HCl, or Cl2.
* * * * *
    (d) To be eligible for either health-based compliance
alternative, the parameters that defined your affected source as
eligible for the health-based compliance alternatives must be
submitted to your permitting authority for incorporation into your
title V permit, as federally enforceable limits, at the same time
you submit your health-based eligibility demonstration. These
parameters include, but are not limited to, fuel type, fuel mix
(annual average), emission rate, type of control devices, process
parameters (e.g., maximum heat input), and non-process parameters
(e.g., stack height).

9. When Do I Have to Complete and Submit My Health-Based Eligibility
Demonstration?

* * * * *
    (b) If you have a new or reconstructed affected source that
starts up before the effective date of subpart DDDDD, or an affected
source that is an area source that increases its emissions or its
potential to emit such that it becomes a major source of HAP before
the effective date of subpart DDDDD, then you may submit an
eligibility demonstration at any time after September 13, 2004 but
you must comply with the emissions limits in table 1 to this subpart
and all other requirements of subpart DDDDD until your eligibility
demonstration is submitted to your permitting authority in
accordance with the requirements of section 10 of this appendix.
    (c) * * *
    (1) You must complete and submit a preliminary eligibility
demonstration based on the information (e.g., equipment types,
estimated emission rates, process and non-process parameters,
reference values, etc.) that will be used to apply for your title V