[Federal Register Volume 76, Number 33 (Thursday, February 17, 2011)]
[Rules and Regulations]
[Pages 9450-9489]
[FR Doc No: 2011-2608]

Vol. 76

Thursday,

No. 33

February 17, 2011

Part III

Environmental Protection Agency

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40 CFR Parts 9 and 63

National Emission Standards for Hazardous Air Pollutants: Gold Mine Ore
Processing and Production Area Source Category; and Addition to Source
Category List for Standards; Final Rule

Federal Register / Vol. 76 , No. 33 / Thursday, February 17, 2011 /
Rules and Regulations

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 9 and 63

[EPA-HQ-OAR-2010-0239; FRL-9242-3]
RIN 2060-AP48

National Emission Standards for Hazardous Air Pollutants: Gold
Mine Ore Processing and Production Area Source Category; and Addition
to Source Category List for Standards

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: EPA is adding the gold mine ore processing and production area
source category to the list of source categories to be regulated under
Section 112(c)(6) of the Clean Air Act due to its mercury emissions.
EPA is also promulgating national emission standards for hazardous air
pollutants to regulate mercury emissions from this source category.

DATES: This final rule is effective on February 17, 2011. The
incorporation by reference of certain publications listed in the final
rule is approved by the Director of the Federal Register as of February
17, 2011.

ADDRESSES: EPA has established a docket for this action under Docket ID
No. EPA-HQ-OAR-2010-0239. All documents in the docket are listed on the
http://www.regulations.gov Web site. Although listed in the index, some
information is not publicly available, e.g., Confidential Business
Information (CBI) or other information whose disclosure is restricted
by statute. Certain other material, such as copyrighted material, is
not placed on the Internet and will be publicly available only in hard
copy form. Publicly available docket materials are available either
electronically through www.regulations.gov or in hard copy at the EPA
Headquarters Library, Room Number 3334, EPA West Building, 1301
Constitution Ave., NW., Washington, DC. The EPA/DC Public Reading Room
hours of operation are 8:30 a.m. to 4:30 p.m. Eastern Standard Time
(EST), Monday through Friday. The telephone number for the Public
Reading Room is<PHONE_NUMBER>, and the telephone number for the Air
and Radiation Docket and Information Center is<PHONE_NUMBER>.

FOR FURTHER INFORMATION CONTACT: Mr. Chuck French, Sector Policies and
Program Division, Office of Air Quality Planning and Standards (D243-
02), Environmental Protection Agency, Research Triangle Park, North
Carolina 27711, telephone number<PHONE_NUMBER>; fax number (919) 541-
3207, e-mail address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION: The information presented in this preamble
is organized as follows:

I. General Information
    A. Does this action apply to me?
    B. Where can I get a copy of this document?
    C. Judicial Review
II. Addition to Section 112(c)(6) Source Category List
III. What is the statutory authority and regulatory approach for the
proposed standards?
IV. Summary of Significant Changes Since Proposal
    A. Applicability
    B. Final Emission Standards
    C. Compliance Dates
    D. Compliance Requirements
    E. Monitoring Requirements
    F. Definitions
V. Summary of Responses to Major Comments
    A. Statutory Requirements
    B. Applicability
    C. MACT Floors
    D. Compliance Determinations
    E. Monitoring Requirements
    F. Definitions
VI. Summary of Environmental, Economic and Health Benefits
VII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From
Environmental Health and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act
    J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations
    K. Congressional Review Act

I. General Information

A. Does this action apply to me?

    The regulated categories and entities potentially affected by this
final rule include:

------------------------------------------------------------------------
                                                         Examples of
             Category               NAICS code \1\   regulated entities
------------------------------------------------------------------------
Industry:
    Gold Ore Mining..............           212221  Establishments
                                                     primarily engaged
                                                     in developing the
                                                     mine site, mining,
                                                     and/or
                                                     beneficiating
                                                     (i.e., preparing)
                                                     ores valued chiefly
                                                     for their gold
                                                     content.
                                                     Establishments
                                                     primarily engaged
                                                     in transformation
                                                     of the gold into
                                                     bullion or dore bar
                                                     in combination with
                                                     mining activities
                                                     are included in
                                                     this industry.
------------------------------------------------------------------------
\1\ North American Industry Classification System.

    This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be affected by this
action. To determine whether your facility would be regulated by this
action, you should examine the applicability criteria in 40 CFR
63.11640 of subpart EEEEEEE (National Emission Standards for Hazardous
Air Pollutants (NESHAP): Gold Mine Ore Processing and Production Area
Source Category). If you have any questions regarding the applicability
of this action to a particular entity, consult either the air permit
authority for the entity or your EPA Regional representative, as listed
in 40 CFR 63.13 of subpart A (General Provisions).

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

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

C. Judicial Review

    Under Section 307(b)(1) of the Clean Air Act (CAA), judicial review
of this final rule is available only by filing a petition for review in
the U.S. Court of

Appeals for the District of Columbia Circuit by April 18, 2011. Under
section 307(d)(7)(B) of the CAA, only an objection to this final rule
that was raised with reasonable specificity during the period for
public comment can be raised during judicial review. Moreover, under
section 307(b)(2) of the CAA, the requirements established by this
final rule may not be challenged separately in any civil or criminal
proceedings brought by EPA to enforce these requirements.
    Section 307(d)(7)(B) also provides a mechanism for us to convene a
proceeding for reconsideration, ``[i]f the person raising an objection
can demonstrate to EPA that it was impracticable to raise such
objection within [the period for public comment] or if the grounds for
such objection arose after the period for public comment (but within
the time specified for judicial review) and if such objection is of
central relevance to the outcome of the rule.'' Any person seeking to
make such a demonstration to us should submit a Petition for
Reconsideration to the Office of the Administrator, U.S. EPA, Room
3000, Ariel Rios Building, 1200 Pennsylvania Ave., NW., Washington, DC
20460, with a copy to the person listed in the preceding FOR FURTHER
INFORMATION CONTACT section.

II. Addition to Section 112(c)(6) Source Category List

    For reasons stated in the preamble to the proposed rule (75 FR
22470, April 28, 2010), we are adding the gold mine ore processing and
production area source category to the list of source categories under
section 112(c)(6) on the basis of its mercury emissions. The preamble
for the proposed rule provides a description of this industry including
the processes used and the typical control technologies applied.

III. What is the statutory authority and regulatory approach for the
proposed standards?

    As explained in the preamble to the proposed rule, CAA section
112(c)(6) requires that EPA set standards under section 112(d)(2) or
(d)(4). The mercury standards for the gold mine ore processing and
production area source category are being established under CAA section
112(d)(2), which requires maximum available control technology (MACT)
level of control. Under CAA section 112(d), the MACT standards for
existing sources must be at least as stringent as the average emissions
limitation achieved by the best performing 12 percent of existing
sources (for which the administrator has emissions information) for
source categories and subcategories with 30 or more sources, or the
best performing 5 sources for categories and subcategories with fewer
than 30 sources (CAA section 112(d)(3)(A) and (B)). This level of
minimum stringency is called the MACT floor. For new sources, MACT
standards must be at least as stringent as the emission control that is
achieved in practice by the best controlled similar source (CAA section
112(d)(3)). EPA also must consider more stringent ``beyond-the-floor''
control options. When considering beyond-the-floor options, EPA must
consider not only the maximum degree of reduction in emissions of HAP,
but must take into account costs, energy, and nonair quality health and
environmental impacts when doing so.

IV. Summary of Significant Changes Since Proposal

    This section summarizes the significant changes to the rule since
proposal. Additional information on the basis for these changes and
other changes can be found in the Summary of Responses to Major
Comments in section V of this preamble and in the Summary of Comments
and Responses document which is available in the docket for this
action.

A. Applicability

    We have clarified in Sec.  63.11651 of the final rule that the term
``gold mine ore processing and production facility'' does not include
individual prospectors and very small pilot scale mining operations.
These types of operations are very small and were not included in the
section 112(c)(6) inventory that was the basis for the listing of the
gold mine ore processing and production source category.

B. Final Emission Standards

    We have made changes to all of the proposed emission standards as
the result of the following developments: (1) Inclusion of additional
emissions test data received since proposal; \1\ (2) additional
analyses in response to public comments on the proposed rule; \2\ and
(3) further review of the data used to develop the standards for the
proposed rule. The changes are summarized below and described in more
detail in section V of this preamble. We estimate the final MACT
standards will reduce mercury emissions from gold mine ore processing
and production down to a level of about 1,180 pounds per year, which
will be an estimated 77 percent reduction from the 2007 emissions level
(5,000 lb/yr), a 95 percent reduction from year 2001 emissions level
(about 23,000 lb/yr), and more than 97 percent reduction from
uncontrolled emissions levels (more than 37,000 lb/yr).
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    \1\ The new test data used in final MACT standard calculations
can be found in the docket as docket items: EPA-HQ-OAR-2010-0239-
0359 and EPA-HQ-OAR-2010-0239-0360.
    \2\ Analyses for the final MACT standards can be found in the
docket in the document titled: ``Development of the MACT Floors and
MACT for the Final NESHAP for Gold Mine Ore Processing and
Production'' (also known as the ``MACT Development Document'').
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Ore Pretreatment Processes
    In the proposed rule, the proposed mercury emission standards for
both existing and new ore pretreatment processes were 149 pounds per
million tons of ore processed (lb/million tons of ore). In the final
rule, the emission standard for existing sources is 127 lb/million tons
of ore; and for new sources the emission standard is 84 lb/million tons
of ore. The final emission standards are based on several changes to
the data set used in the MACT analysis. Since we issued the proposed
rule, we collected emissions data from more recent tests that were not
available at proposal. Further, we learned that two emissions tests
that we used to develop the MACT floor in our proposed rule had been
invalidated by the Nevada Division of Environmental Protection (NDEP),
and we removed those test results from the database. Information on the
specific tests invalidated and the rationale are available in the
docket (docket item number EPA-HQ-OAR-2010-0239-0061). We also
discovered that the test data for a unit within the ore pretreatment
affected source at a facility should have been included as part of a
different unit at the same facility. We have also dropped the data for
one facility from the analysis because their autoclave was shut down in
2007 and dismantled, and the only test data we had for them was one
test of the autoclave when it was operating in 2006. Moreover, we
conducted additional beyond-the-floor analyses for the ore pretreatment
affected source. The new information and analyses described above are
discussed in more detail in section V.C of this preamble and in the
MACT Development Document which is available in the docket for this
rulemaking.
    The resulting data set included emissions data for four facilities
that ranged from 45 to 165 lb/million tons of ore. Based on these data,
and using the same upper prediction limit (UPL) approach used for
proposal to account for variability, we determined the MACT floor to be
158 lb/million tons of ore for existing sources of ore pretreatment
processes and 84 lb/

million tons of ore for new sources. As explained in the proposed rule
(75 FR at 22482), the technologies that we estimate are needed to
achieve the MACT floor level of performance for existing ore
pretreatment processes include calomel-based mercury scrubbers on
roasters and venturi scrubbers on autoclaves and ancillary roaster
operations. The preamble to the proposed rule provides a description of
the UPL and the approach and calculations used to derive the UPL. The
UPL is also discussed further in section V.
    In our beyond-the-floor analysis, we evaluated the potential to add
condensers and carbon adsorbers to control autoclaves, and the
potential to add carbon adsorbers to control the ore pre-heaters. Based
on this beyond-the-floor analysis, we concluded that it is feasible and
cost-effective to establish the MACT standard for existing sources at a
level lower than the MACT floor. Based on the analysis, we determined
the MACT standard for existing sources to be 127 lb/million tons of
ore. For new sources, we determined that it was not feasible and cost-
effective to establish a standard lower than the new source MACT Floor
(of 84 lb/million tons); therefore the MACT standard for new sources
was determined to be 84 lb/million tons.
    The technologies needed to achieve the new source MACT floor will
depend on the types of ore processed, amount of mercury in the ore, and
specific process units used. Nevertheless, we conclude that, at a
minimum, the controls that would be needed would include calomel-based
mercury scrubbers on roasters and venturi scrubbers on autoclaves and
ancillary roaster operations. Additional controls that will likely be
needed to achieve emissions at or below the new source MACT floor level
include condensers and carbon adsorbers on autoclaves, and carbon
adsorbers on ore preheaters.
    Table 1 summarizes the MACT floor analysis for existing and new ore
pretreatment processes. The beyond-the-floor analyses are explained
further in section V of this preamble and in more detail in the MACT
Development document.

       Table 1--MACT Floor Results for Ore Pretreatment Processes
------------------------------------------------------------------------
                                                               Average
                                                             performance
                         Facility                            (lb/million
                                                            tons of ore)
------------------------------------------------------------------------
A.........................................................            45
C.........................................................            56
E.........................................................            71
D.........................................................           165
Average of the 4 facilities...............................            84
99% UPL for existing sources (i.e., the MACT Floor for               158
 existing sources)........................................
99% UPL for new sources \1\ (i.e., the MACT Floor for new             84
 sources).................................................
------------------------------------------------------------------------
\1\ The MACT Floor for new sources is based on the average performance
  of Facility A (i.e., 45) plus an amount to account for variability
  (i.e., 45 + 39 = 84).

Carbon Processes
    Under the proposed rule, all carbon processes were subject to the
same proposed mercury emissions limits of 2.6 pounds per ton of
concentrate (lb/ton of concentrate) for existing sources and, for new
sources, either 0.14 lb/ton of concentrate or 97 percent reduction in
uncontrolled mercury emissions. These limits would have applied to
facilities that operate mercury retorts and facilities that do not
operate mercury retorts. In the final rule, we distinguish between
carbon processes with mercury retorts and carbon processes without
mercury retorts because we believe there are unique differences in
these two types of processes. Therefore, the final rule specifies
separate emission standards for these two types of processes. Moreover,
the final emission standards for carbon processes reflect inclusion of
new test data that were not available at proposal. We also revised our
data set based on new information that we received since proposal which
impacted which sources were among the best performing sources. Based on
the data that we have, there are 10 facilities that have carbon
processes with mercury retorts, and we have mercury emissions data for
all 10 of these facilities. There are approximately 7 facilities that
have carbon processes without mercury retorts, and we have
comprehensive and reliable mercury emissions data for 2 of these
facilities. These 2 facilities are the best controlled facilities
within that group based on the information we have. (See section V for
further details.) For carbon processes with mercury retorts, the
emission standard in the final rule is 2.2 lb/ton of concentrate for
existing sources and 0.8 lb/ton of concentrate for new sources. For
carbon processes without mercury retorts, the emission standard in the
final rule is 0.17 lb/ton of concentrate for existing sources and 0.14
lb/ton of concentrate for new sources.
    For carbon processes, regardless of whether the facility operates a
mercury retort, we estimate that to meet the MACT floor facilities
would generally need to have mercury condensers and carbon adsorbers to
control mercury emissions. We also considered beyond-the-floor options
for both existing and new sources for these process groups, which were
based on the addition of a second carbon adsorber; however, we rejected
those options because they are not cost effective. Additional
information on the analyses performed can be found in the MACT
Development document in the docket for this rulemaking.
    We also eliminated in the final rule the compliance alternative of
97 percent reduction for new carbon processes. After reviewing the
comments received on this proposed alternative standard and giving
further consideration to the practicality of how it would be measured,
we concluded that this option would be difficult to implement,
particularly when multiple processes that are operated at different
times vent to a single control device and stack. In addition, we have
limited data supporting this compliance alternative. In proposing this
alternative for comment, we had hoped to, but did not, receive
additional data indicating that the 97 percent reduction option would
be equivalent to the proposed new source limit of 0.14 pounds of
mercury per ton of concentrate. For the reasons stated above, we
eliminated the 97 percent control efficiency option for new carbon
processes in the final rule.
    Table 2 summarizes the results of the MACT floor analysis for
carbon processes with mercury retorts, and Table 3 summarizes the
analysis for carbon processes without mercury retorts.

  Table 2--MACT Floor Results for Carbon Processes With Mercury Retorts
------------------------------------------------------------------------
                                                              Average
                                                            performance
                         Facility                            (lb/ton of
                                                            concentrate)
------------------------------------------------------------------------
N........................................................           0.53
J........................................................           0.74
I........................................................           1.06
A........................................................           1.47
H........................................................           1.67
D........................................................           2.20
C........................................................           3.71
G........................................................           8.17
E........................................................          14.49
B........................................................          20.60

Average of top 5.........................................           1.1
99% UPL for existing sources (i.e., MACT Floor for                  2.2
 existing sources).......................................
99% UPL for new sources (i.e., MACT Floor for new                   0.8
 sources)................................................
------------------------------------------------------------------------

Table 3--MACT Floor Results for Carbon Processes Without Mercury Retorts
------------------------------------------------------------------------
                                                              Average
                                                            performance
                         Facility                            (lb/ton of
                                                            concentrate)
------------------------------------------------------------------------
M........................................................          0.058
F........................................................          0.098
Average of top 2 facilities..............................          0.078
99% UPL for existing sources (i.e., MACT Floor for                 0.17
 existing sources).......................................
99% UPL for new sources (i.e., MACT Floor for new                  0.14
 sources)................................................
------------------------------------------------------------------------

Non-Carbon Concentrate Processes
    Under the proposed rule, the mercury emission standards for non-
carbon concentrate processes were 0.25 lb/ton of concentrate for
existing sources and 0.2 lb/ton of concentrate for new sources. In the
final rule, the emission standards for these sources are 0.2 lb/ton of
concentrate for existing sources and 0.1 lb/ton of concentrate for new
sources. These standards are based on using new emissions data that
were not available when we developed the proposal, along with the data
that were used for the proposal. For non-carbon concentrate processes,
we estimate that to meet the MACT floors, for both existing and new
sources, facilities would generally need to control mercury emissions
using mercury condensers and carbon adsorbers. As explained in the
proposed rule, we considered beyond-the-floor controls for these
processes (which were based on adding a second carbon adsorber to the
MACT floor level controls) but concluded those controls would not be a
cost-effective option. There are approximately 3 facilities in the U.S.
that use these types of processes. We have emissions tests data for 2
of these facilities.
    Table 4 summarizes the results of the MACT floor analysis for non-
carbon concentrate processes.

    Table 4--MACT Floor Results for Non-Carbon Concentrate Processes
------------------------------------------------------------------------
                                                              Average
                                                            performance
                         Facility                            (lb/ton of
                                                            concentrate)
------------------------------------------------------------------------
K........................................................          0.047
L........................................................          0.078
Average of 2 facilities..................................          0.062
99% UPL for existing sources (i.e., MACT Floor for                 0.2
 existing sources).......................................
99% UPL for new sources (i.e., MACT Floor for new                  0.1
 sources)................................................
------------------------------------------------------------------------

C. Compliance Dates

    In the final rule, we provide in Sec.  63.11641 that the compliance
date for existing sources is 3 years after promulgation of the final
rule as opposed to 2 years as proposed. We reviewed the information
provided in public comments on the challenges of installing new
controls, especially for autoclaves, which, although the controls have
not yet been demonstrated, have been proposed by facilities with
autoclaves in their Nevada Mercury Control Program (NMCP) permit
applications. We also considered the installation of new controls on
the roaster preheaters, which also have not yet been demonstrated, but
have been proposed by these facilities in their NMCP permit
applications. We concluded that allowing 3 years for existing sources
to comply is appropriate, given the complexity of the sources, the
combinations of control devices that are needed in many cases, and the
amount of time necessary for designing, installing, testing, and
commissioning additional emission controls for mercury.

D. Compliance Requirements

    Section 63.11646(a)(1) of the final rule does not include Method
30A, as was proposed, as an appropriate method for determining mercury
concentration because it is not yet in general use. This paragraph
further clarifies that the use of ASTM D6784-02 and Method 30B are
allowed for compliance tests only if approved by the permit authority
as opposed to automatically being allowed as in the proposal. The final
rule also does not include the requirement to follow the acetone rinse
procedures and the absence of cyclonic flow determination requirement,
which were in subparagraphs (v) and (vi) respectively of our proposed
Sec.  63.11646(a)(1). Method 29 already includes requirements for the
acetone rinse, so there is no need to specify those procedures in the
rule; and Method 1, which is required by the rule, addresses the issue
of cyclonic flow.
    In Sec.  63.11646(a)(2), we changed the minimum sample volume when
Method 29 is used to determine compliance from the proposed 60 dry
standard cubic feet (dscf) to 30 dscf. We believe this volume is
adequate for detecting mercury in the samples and determining mercury
emissions for this industry. We have also expanded this section to
address non-detect values. If the emission testing results for any of
the emission points yield a non-detect value, the final rule requires
that the minimum detection limit (MDL) be used to calculate the mass of
emissions (in pounds of mercury) for that emission point that would
subsequently be used in the calculations to determine if the source is
in compliance with the MACT standard. If the resulting calculations
indicate that mercury emissions are greater than the MACT emission
standard, the owner or operator may repeat the mercury emissions
testing one additional time for any emission point for which the
measured result was below the MDL using procedures that produce lower
MDL results. If this additional testing is performed, the results from
that testing must be used to determine compliance.
    For sources with multiple emission units (e.g., two roasters)
ducted to a common control device and stack, we have clarified in Sec.
63.11646(a)(3) that compliance testing must either be performed with
all affected emissions units in operation, if this is possible, or
units must be tested separately. We also clarified that the
establishment of operating limits for units that share a common stack
can be based on emissions when all process units are operating
together, or based on testing units separately. However, this
requirement does not affect the frequency and schedule for monitoring,
which are specified in the rule. If facilities have batch type
processes that cannot be operated simultaneously, then the facility can
test some or all of the units individually.
    In Sec.  63.11646(a)(6) and (7), we clarify that the production
data used in compliance determinations are based on full calendar
months. For the initial compliance test, data for all the full calendar
months between publication of the final rule and the initial compliance
test must be used. This initial compliance determination must include
at least one full month of production

data (e.g., hours of operation, and million tons of ore processed or
tons of concentrate processed) including the month the test was
conducted. For subsequent annual compliance tests, data for the 12 full
calendar months prior to the annual compliance test must be used to
demonstrate compliance. In addition, we clarify in paragraphs Sec.
63.11646(a)(5), (6) and (7) that compliance determinations are based on
the number of 1-hour periods each process unit operates. By using the
1-hour period terminology, the final rule language is consistent with
the terminology used in the General Provisions to part 63.
    Because the final rule does not include the 97 percent reduction
option that was in Sec.  63.11645(e)(2) of the proposed rule, we have
removed from the final rule the compliance requirement for that option
that was in Sec.  63.11646(b) of the proposed rule, which addressed
testing the inlets and outlets for sources choosing that proposed
option.

E. Monitoring Requirements

    Section 63.11647(a) of the final rule includes an additional option
for monitoring mercury emissions from roasters. The proposed rule
specified two options for monitoring mercury emissions: Paragraph
(a)(1) specified weekly sampling using PS 12B; and paragraph (a)(2)
specified continuous monitoring using a mercury continuous emissions
monitoring system (CEMS). In the final rule, we added paragraph (a)(3)
to provide a third option of continuous sampling using PS 12B. In
addition, paragraph (a)(1) in the final rule was changed to require
sampling at least twice per month using either PS 12B or Method 30B
rather than weekly. We believe that Method 30B is an acceptable
alternative method for monitoring purposes and allows owners and
operators more flexibility in how they monitor roaster emissions. We
also believe that sampling twice per month coupled with extensive
parametric monitoring of control devices (as explained below) is
sufficient for the monitoring option in paragraph (a)(1).
    Section 63.11647(a)(4)(iii) of the proposed rule would have
required additional compliance testing if the mercury concentration in
the ore fed to the roaster was higher than any concentration measured
in the previous 12 months. We have removed this requirement from the
final rule because it is not clear that the mercury content of the ore
has a significant effect on the performance of mercury scrubbers
applied to roasters, which are designed to handle and operate
efficiently for a range of mercury inlet concentrations. In addition,
condensers are used to recover liquid elemental mercury prior to the
mercury scrubber, and any increase in mercury loading would likely
result in an increase in the recovery of elemental mercury.
    The final rule incorporates several changes to Sec.  63.11647(b),
which addresses monitoring of calomel-based mercury scrubbers (i.e.,
mercury scrubbers) that are used to control emissions from roasters.
The proposed rule required monitoring of the scrubber liquid flow,
liquid chemistry, scrubber pressure drop, and scrubber inlet gas
temperature hourly. The final rule does not include the requirement to
monitor pressure drop across calomel-based scrubbers because we
conclude that pressure drop is not related to mercury emission control
performance by this type of control device. In addition, the final rule
allows hourly monitoring of the line pressure in the scrubber liquid
supply line as an alternative to hourly monitoring of scrubber liquid
flow rate. Line pressure monitoring is already in practice at some
facilities and provides the same type of information as does liquid
flow rate. As was proposed, the final rule allows the operating limit
for scrubber liquid flow rate (or line pressure) and inlet gas
temperature to be based on the minimum flow rate (or line pressure) or
maximum inlet gas temperature established during the initial
performance test. It also includes two additional options for setting
these operating limits: (1) Based on the manufacturer's specifications
if certain types of systems are designed to operate within a specified
range of flow rates or temperatures; and (2) based on limits
established by the permitting authority. If the facility chooses the
option to establish the limits during initial compliance, the final
rule requires the scrubber flow rate operating limit to be based on
either the lowest value for any run of the initial compliance test or
10 percent less than the average value measured during the compliance
test and the inlet gas temperature operating limit to be based on
either the highest value for any run of the initial compliance test or
10 percent higher than the average value measured during the compliance
test. This requirement takes into account the fact that, although
initially the system may exhibit little variability from test run to
test run, the short-term variability in performance may increase with
time. Additional discussion of these changes can be found in section
V.E of this preamble and in the Summary of Public Comments and
Responses document in the docket for this rulemaking.
    In response to comments, we have revised the requirements for
corrective action following control device monitoring parameter
exceedances specified in Sec.  63.11647(d). Under the final rule, if
the corrective actions taken following an exceedance do not result in
the parameter value (e.g., liquid flow rate, line pressure, or inlet
gas temperature) being returned to within the parameter range or limit
within 48 hours, a mercury concentration measurement must be made to
determine if the operating limit for mercury concentration is being
exceeded. The measurement must be performed and the concentration
determined within 48 hours after the initial 48 hours, or a total of 96
hours from the time the parameter was exceeded. If the measured mercury
concentration meets the operating limit for mercury concentration, the
corrective actions are deemed successful. In addition, the owner or
operator may request approval from the permitting authority to change
the parameter range or limit based on measurements of the parameter at
the time the mercury concentration measurement was made. If, on the
other hand, the measured mercury concentration indicates the operating
limit for mercury concentration is exceeded, the exceedance must be
reported as a deviation within 24 hours to the permitting authority,
and the facility must perform a compliance test (pursuant to Sec.
63.11647(d)) within 40 days to determine whether the source is in
compliance with the MACT standard. We believe 40 days is appropriate
because it may take 3 to 4 weeks to schedule and have the testing
contractor on site, and, following completion of the test, another week
or so to receive the final test results, and allows sufficient time to
notify the permitting authority. We also removed the requirement that
roasters must be shut down if a parameter is out of range.
    In Sec.  63.11647(a)(1)(ii) of the final rule, we require these
same corrective actions described above (i.e., measuring mercury
concentration within 48 hours, reporting a deviation if the data show
the operating limit was exceeded within 24 hours, and conducting a
compliance test within 40 days) for exceedances of mercury
concentration operating limits indicated by the results of the twice
monthly monitoring using PS 12B or Method 30B, CEMS, or continuous
monitoring using PS 12B. In such cases, the owner or operator must use
the results of the compliance test to determine if the ore pretreatment

process affected source is in compliance with the emission standard. If
the source is determined to be in compliance, the owner or operator may
use this compliance test to establish a new operating limit for mercury
concentration for the roaster. We also removed the requirement that
roasters must be shut down if the mercury concentration is out of
range.
    In the final rule, Sec.  63.11647(f)(1) requires monthly sampling
of the exhaust stream of carbon adsorbers using Method 30B. The
duration of sampling must be at least the minimum sampling time
specified in Method 30B and up to one week. The proposed rule required
a full week of such sampling, but, as pointed out by one of the
commenters, breakthrough of the sampling trap from exhaust streams with
high mercury concentrations could occur before a week had elapsed.
    Section 63.11647(f)(2) of the final rule clarifies that sampling of
the carbon bed must be collected from the inlet and outlet of the bed.
This paragraph also specifies that, for carbon adsorbers with multiple
carbon columns or beds, the sampling should be performed in the first
and last column or bed rather than at the inlet or outlet.
    We have deleted Sec.  63.11647(f)(3) in the proposed rule, which
allowed the carbon bed change-out rate to be determined based on
historical data and the estimated life of the carbon. We have concluded
that this method would not be adequate to ensure that breakthrough does
not occur earlier than expected.
    We have clarified Sec.  63.11647(h) with respect to the monitoring
of scrubbers (other than the calomel-based mercury scrubbers described
above). Under the final rule, owners or operators are required to
monitor and record water flow rate (or line pressure) and scrubber
pressure drop once per shift; they also must record any occurrences
when the water flow rate (line pressure) or pressure drop are outside
the operating range, take corrective actions to return the water flow
rate (line pressure) or pressure drop back in range, and record the
corrective actions taken. At proposal, the water flow rate and pressure
drop were to be monitored continuously. However, measuring the water
flow rate (line pressure) and pressure drop once per shift will provide
two to three measurements per day, and we believe that is sufficient to
assure proper operations of the wet scrubber, and thus assure
compliance with the emission standards. We have also added the option
of monitoring the line pressure in the scrubber liquid supply line as
an alternative to monitoring scrubber liquid flow rate because line
pressure monitoring is already in practice at some facilities and
provides the same type of information as does liquid flow rate. As was
proposed, the final rule allows the operating limit for water flow rate
and pressure drop to be based on the minimum value during the initial
performance test. It also includes two additional options for setting
the operating limit: (1) Based on the manufacturer's specifications;
and (2) based on limits established by the permitting authority. We
have also clarified that, for scrubbers on autoclaves, the pressure
drop parameter range should be established from manufacturer's
specifications only.

F. Definitions

    We have added a definition of carbon adsorber to Sec.  63.11651 to
clarify that this term, as used in the final rule, includes control
devices consisting of a single fixed carbon bed, multiple carbon beds
or columns, carbon filter packs or modules, and other variations of
carbon adsorber design.
    The definition of ``gold mine ore processing and production
facility'' in Sec.  63.11651 of the rule has been clarified to state
that small operations, such as prospectors and very small pilot scale
mining operations, that process or produce less than 100 pounds of
concentrate per year are excluded from the source category. These
prospectors and very small pilot-scale operations (that process at or
below this level) were not included in the section 112(c)(6) inventory
that was the basis for the listing of gold mine ore processing and
production source category. These types of very small operations were
not intended to be subject to the final rule, and we do not expect any
significant emissions from them. We also clarified that the source
category does not include facilities at which 95 percent or more of the
metals produced are metals other than gold. For example, if other non-
ferrous metals (such as copper, lead, nickel, or zinc) comprise 95
percent or more of the product, the facility is not part of the gold
ore processing and production source category.

V. Summary of Responses to Major Comments

A. Statutory Requirements

1. Listing of the Gold Mine Ore Processing and Production Source
Category Under Section 112(c)(6)
    Comment: One commenter stated that adding the gold mine ore
processing and production category to the list of categories required
by Clean Air Act (CAA) section 112(c)(6) was correct and required
because gold mines accounted for a significant portion of the aggregate
emissions of mercury in the baseline year (1990) and because they still
do so today. Other commenters stated that EPA does not have the
authority to list gold mining processing and production as a source
category under section 112(c)(6) and noted that section 112(c)(6)
requires EPA to list, by 1995, categories of sources that make up 90
percent of the 1990 emissions for a subset of hazardous air pollutants
(HAP), including mercury. The commenters said that EPA concluded its
statutory listing obligation for mercury in 1998 with the publication
of a list of source categories constituting 90 percent of aggregate
mercury emissions, and that gold mining was not included on that list
in 1998. In addition, the commenters said that the CAA requires EPA to
list all categories under section 112(c)(6) by 1995 and complete
issuance of standards for all listed sources by 2000, a task that would
be impossible if EPA had the authority to add source categories ad
infinitum.
    Response: We appreciate the commenter's support in listing the gold
mine processing and production area source category pursuant to section
112(c)(6). We disagree, however, with the commenters that assert that
EPA is precluded from listing additional categories pursuant to section
112(c)(6). The commenters appear to be arguing that EPA is limited to a
single listing opportunity under section 112(c)(6) and, having not
listed gold mine ore processing and production in the initial 1998
listing effort, EPA is now foreclosed from doing so. There is nothing
in the language of section 112(c)(6), however, that precludes EPA from
listing additional source categories to the extent EPA determines that
those categories are needed to meet the 90 percent requirement in
section 112(c)(6). Indeed, the commenter's reading is contrary to the
fundamental purpose of section 112(c)(6).
    The core requirement of section 112(c)(6) is that EPA ``shall * * *
list categories and subcategories of sources assuring that sources
accounting for not less than 90 per centum of the aggregate emissions
of each such pollutant'' are subject to standards under either
11217FE0(d)(2) or (d)(4). EPA reasonably interprets section 112(c)(6)
as allowing it to revise the list to add categories, where, as here, it
determines that it needs the additional categories to meet the 90
percent requirement in section 112(c)(6). Indeed, EPA has previously
revised the section 112(c)(6)

list to add a source category, where EPA determined that category was
needed to meet its 90 percent requirement for mercury. See 72 FR 74087
(Dec. 28, 2007) (adding area source electric arc furnaces to the
section 112(c)(6) list).
    As explained in the proposed rule, we have a 1990 baseline
emissions inventory, and it is against this baseline that we assess
compliance with the 90 percent requirement for each of the pollutants
specified in section 112(c)(6). EPA explained in the initial 1998
listing notice that it was using 1990 as the baseline year for
assessing compliance with the 90 percent requirement. As EPA has
developed emission standards for the sources included on the initial
section 112(c)(6) list, it has acquired additional information on those
sources and their emissions in 1990, which has resulted in some
revisions to the 1990 baseline emissions inventory estimates. These
revisions resulted in the need to regulate an additional source
category. See 72 FR 74087 (setting standards for area source electric
arc furnaces).
    In addition to obtaining additional information concerning the
source categories on the initial list, EPA has obtained additional
information concerning the 1990 emissions of other sources. As
explained in the preamble to the proposed rule, at the time of the
initial section 112(c)(6) listing, there was very little available
information on mercury emissions from gold mine ore processing and
production. See 75 FR 22471. Because EPA lacked emissions information
on mercury emissions from this source category at the time of the
listing decision, EPA was unable to estimate the 1990 baseline mercury
emissions from the gold mine ore processing and production source
category and include this category in the first listing effort. Based
on information that became available after the initial listing, EPA now
finds that regulation of the area source gold mine ore processing and
production category is needed to meet the 90 percent requirement for
mercury. 75 FR 22471. Under the commenters' view, EPA cannot add any
additional categories to the section 112(c)(6) list following the
initial listing. If true, EPA could not meet its section 112(c)(6)
obligation--a result Congress could not have intended. EPA reasonably
interprets section 112(c)(6) in a manner that allows the Agency to
achieve that provision's core requirement. EPA repeats that it sees
nothing in the language or purpose of section 112(c)(6) that precludes
it from listing additional source categories as needed.
    Finally, Congress left to EPA's discretion which categories and
subcategories of sources to include on the section 112(c)(6) list. We
have determined that we need the gold mine ore processing and
production source category to meet the 90 percent requirement in
section 112(c)(6) for mercury and are therefore now setting standards
for that category.
    We also reject the comment that the task of completing standards by
2000 would be impossible if EPA had the authority to add source
categories. Nevertheless, EPA is under a court ordered deadline to
complete section 112(c)(6) standards by January 16, 2011. (Sierra Club
v. EPA, Consolidated Case No. 01-1537, D.D.C).
    Comment: Some commenters claimed that EPA did not provide an
adequate basis for its 1990 emissions estimate for gold mining
processing and production. Specifically, they questioned EPA's
estimated emissions of 4.4 tons from this source category in the 1990
baseline year.
    Response: Although the commenters question EPA's estimated
emissions of 4.4 tons from this source category in the 1990 baseline
year, they did not provide an alternative method for calculating such
emissions or alternative data or assumptions that should be used. They
also did not explain what they think the 1990 baseline emissions should
have been. EPA continues to maintain that its baseline emissions
estimate is reasonable. The methodology EPA used to derive that
estimate is described in docket item EPA-HQ-OAR-2010-0239-0175.
    Comment: Several commenters stated that Phase 2 permits under the
Nevada Mercury Control Program (NMCP), which are scheduled for issuance
by the end of 2010, will result in MACT-level controls on all thermal
units at Nevada gold mines. According to the commenters, these permits
are the culmination of a 7-year collaborative effort between NDEP and
the gold mining industry to substantially reduce mercury emissions from
gold mine processes. The commenters said that the proposal does not
address how the NESHAP will result in reductions in mercury at gold
mines in areas of the country other than Nevada, where the mercury
content of the ore in gold mines is non-existent or only a fraction of
the amount found in Nevada, and Nevada accounted for 99 percent of
mercury emissions associated with gold mining operations in the United
States. According to the commenters, this shows that if Nevada has an
equivalent mercury control program for the gold mining industry, then
there is nothing to be gained from imposing a Federal program, and if
EPA acknowledges that the mines in Nevada are already well controlled,
then the listing of gold mining and the promulgation of an additional
layer of regulation at substantial cost to industry, but with little
environmental benefit, is both legally indefensible and practically
unsupportable.
    Response: As explained above, we are regulating the gold mine ore
processing and production source category to meet the 90 percent
requirement in section 112(c)(6) for mercury and are therefore setting
standards for that category. Based on our 1990 baseline inventory for
section 112(c)(6) and other emissions information for subsequent years,
we estimate that this industry was among the top ten highest emitting
categories of mercury emissions in the U.S. in 1990 and has remained in
the top 10 since that time. Moreover, even though most emissions are
from facilities located in Nevada, several commenters expressed serious
concerns about the potential for mercury emissions from new gold mines
in other States (e.g., Alaska). We share these concerns about potential
emissions from new gold mine facilities. Finally, Congress left to
EPA's discretion which categories and subcategories of sources to
include on the section 112(c)(6) list. We are regulating the gold mine
ore processing and production source category to meet the 90 percent
requirement in section 112(c)(6) for mercury and are therefore now
promulgating a Federal NESHAP for existing and new gold mine ore
processing and production facilities.
2. Emission Standards for HAP Other Than Mercury
    Comment: One commenter stated that CAA section 112(c)(6) provides
that EPA must ``list categories and subcategories of sources assuring
that sources accounting for not less than 90 percent of each
[enumerated] pollutant are subject to standards under subsection (d)(2)
or (d)(4) of this section.'' The commenter also stated that the D.C.
Circuit has held repeatedly that when EPA sets standards for a category
or subcategory of sources under section 112(d)(2), EPA has a statutory
duty to set emission standards for each HAP that the sources in that
category or subcategory emit (e.g., National Lime Ass'n v. EPA, 233
F.3d 625, 633-634 (D.C. Cir. 2000)). The commenter concluded that when
EPA sets standards for gold mines under section 112(d)(2), as section
112(c)(6) requires it to do, EPA must set section 112(d)(2) emission
standards for all the HAP that gold mines emit.
    The commenter said that EPA appears to believe that because gold
mines are

needed only to reach the section 112(c)(6) requirement of 90 percent
for mercury and not for the other pollutants enumerated in section
112(c)(6), EPA's only obligation under section 112(c)(6) is to set
section 112(d)(2) standards for mercury. The commenter said that
section 112(c)(6) expressly requires EPA to issue section 112(d)(2)
standards for the ``sources'' in the categories listed under section
112(c)(6), not some subset of the pollutants that those sources emit,
and that section 112(d)(2) standards must include emission standards
for each HAP that a source category emits. The commenter continued by
stating that nothing in the CAA exempts EPA from this requirement. The
commenter concluded that, had Congress wished to give EPA discretion to
set standards for only some of the pollutants emitted by a category
listed under section 112(c)(6), it would have done so expressly.
    Response: EPA disagrees with the comment that, even though EPA
lists a category under section 112(c)(6) due to the emissions of one or
more HAP specified in that section, EPA must issue emission standards
for all HAP (including HAP not listed in section 112(c)(6)) that
sources in that category emit. The commenter cited in support the
opinion by the United States Court of Appeals for the DC Circuit in
National Lime Ass'n v. EPA, 233 F.3d 625, 633-634 (D.C. Cir. 2000)).
The part of the National Lime opinion referenced in the comment dealt
with EPA's failure to set emission standards for certain HAPs emitted
by major sources of cement manufacturing because the Agency found no
sources using control technologies for those HAP. In rejecting EPA's
argument, the court stated that EPA has ``a statutory obligation to set
emission standards for each listed HAP.'' Id. at 634. The Court noted
the list of HAP in section 112(b) and stated that section 112(d)(1)
requires that EPA ``promulgate regulations establishing emission
standards for each category or subcategory of major sources * * * of
hazardous air pollutants listed for regulation. * * *'' Id. (Emphasis
added). For the reasons stated below, we do not believe that today's
final rule is controlled by or otherwise conflicts with the National
Lime decision.
    National Lime did not involve section 112(c)(6). That provision is
ambiguous as to whether standards for listed source categories must
address all HAP or only the section 112(c)(6) HAP for which the source
category was listed. Section 112(c)(6) requires that ``sources
accounting for not less than 90 per centum of the aggregate emissions
of each such [specific] pollutant are subject to standards under
subsection (d)(2) or (d)(4).'' This language can reasonably be read to
mean standards for the section 112(c)(6) HAP or standards for all HAP
emitted by the source. Under either reading, the source would be
subject to a section 112(d)(2) or (d)(4) standard.
    The commenter insists that once a section 112(d)(2) standard comes
into play, all HAP must be controlled (per National Lime). But this
result is not compelled by the pertinent provision, section 112(c)(6).
That provision is obviously intended to ensure controls for specific
persistent, bioaccumulative HAP, and this purpose is served by a
reading which compels regulation under section 112(d)(2) only of the
HAP for which a source category is listed under section 112(c)(6),
rather than for all HAP.
    The facts here support the reasonableness of EPA's approach. Gold
mine ore processing is an area source category listed under section
112(c)(6) for regulation under section 112(d)(2) solely due to its
mercury emissions. There is special statutory sensitivity to regulation
of area source categories in section 112. For example, an area source
category may be listed for regulation under section 112 if EPA makes an
adverse effects finding pursuant to Section 112(c)(3) or if EPA
determines that the area source category is needed to meet its section
112(c)(3) obligations to regulate urban HAP or its section 112(c)(6)
obligations to regulate certain persistent bioaccumulative HAP.
Therefore, unless an area source category emits a section 112(c)(3)
urban HAP or a section 112(c)(6) HAP and EPA determines that such
category is needed to meet the 90 percent requirement set forth in
section 112(c)(3) and (c)(6), findings related to adverse human health
or environmental effects are required before EPA can regulate that area
source category--findings EPA is unable to make for non-mercury HAP
emitted from the gold mine ore processing and production source
category at this time. Moreover, to the extent EPA lists an area source
category pursuant to section 112(c)(3) (whether that finding is based
on adverse effects to human health or the environment or a finding that
the source is needed to meet the 90 percent requirement in section
112(c)(3), the statute gives EPA discretion to set generally available
control technology (``GACT'') standards for such sources. 42 U.S.C.
7412(d)(5).
    EPA does not interpret section 112(c)(6) to create a means of
automatically compelling regulation of all HAP emitted by area sources
unrelated to the core object of section 112(c)(6), which is control of
the specific persistent, bioaccumulative HAP, and thereby bypassing
these otherwise applicable preconditions to setting section 112(d)
standards for area sources. Nor does National Lime address the issue,
since the case dealt exclusively with major sources.\3\ 233 F. 3d at
633. Consequently, EPA disagrees with the comment that it is compelled
to promulgate section 112(d)(2) MACT standards for all HAP emitted by
gold mine ore processors.
---------------------------------------------------------------------------

    \3\ EPA acknowledges that major sources regulated under section
112 must be subject to MACT standards for all HAP emitted from the
source category consistent with National Lime.
---------------------------------------------------------------------------

3. Emission Standards for Fugitive Emissions
    Comment: One commenter stated that gold mines have significant
fugitive emissions of mercury, but that EPA did not propose standards
for these emissions or mention them in its proposal. The commenter said
that EPA has a statutory obligation to set standards for gold mine
mercury emissions under section 112(d)(2) and (3), and must set
emission standards for all the mercury emissions from the listed
category. Another commenter described a recent preliminary study at two
facilities in Nevada that found fugitive mercury air emissions from
various non-point sources at those two mining operations such as from
leach pads and tailings ponds.
    One commenter stated that means to control fugitive emissions are
available, such as enclosing their leaching operations. By enclosing
the leaching process, the commenter believes that mines could eliminate
this source of fugitive emissions. The commenter also stated that mines
should not send tailings into open tailing ponds, but into closed
treatment facilities that would remove mercury and other HAP from the
tailings and prevent their release to the air. The commenter
recommended that EPA evaluate the use of sulfur-based complexing agents
for removing mercury during cyanidization of gold. According to the
commenter, research indicates that these products appear useful for
substantially reducing mercury in process solution during heap
leaching.
    Response: Due to the lack of information, we have not included
fugitive mercury emissions at gold mine facilities in our 1990 baseline
emission estimate (or in our more recent emissions estimates) for the
gold mine ore processing and production area source category.
Accordingly, these fugitive emissions are not part of the

source category we are listing and regulating in this final rule. Other
than the recent preliminary research at two facilities, we have no data
on fugitive mercury emissions at gold mine facilities. The recent
preliminary research suggests that some fugitive emissions may be
occurring at these facilities from large non-point sources such as
tailings ponds, leach fields and waste rock piles. However, it is our
understanding that this preliminary research has not yet been published
or peer-reviewed. Thus, at this juncture, we do not have sufficient
information on fugitive emissions.
    Furthermore, we have very little information on how these fugitive
mercury emissions might be controlled. A few commenters suggested that
certain compounds were available that may be useful for limiting these
emissions. However, as far as we know, there has been no demonstration
that these compounds would work effectively to limit the emissions, and
we do not know the costs or potential adverse impacts of applying these
chemicals. Therefore, we question the feasibility and practicality of
applying these chemicals to limit fugitive mercury emissions from these
non-point sources. We also question the feasibility and practicality of
enclosing the leaching operations or the tailings ponds, as suggested
by some commenters.
    As explained in the proposed rule, the gold mine ore processing and
production area source category covers the thermal processes that occur
after ore crushing, including roasting operations (i.e., ore dry
grinding, ore preheating, roasting, and quenching), autoclaves, carbon
kilns, electrowinning, preg tanks, mercury retorts, and furnaces. The
data and calculations used to derive the estimated 4.4 tons of mercury
emissions for this source category for the 1990 baseline inventory for
section 112(c)(6) reflect emissions from the thermal processes
described above, and the final MACT standards address all of these
processes.
4. Major Source Determination
    Comment: One commenter noted that the proposal stated that the gold
mining processing and production source category consists of only area
sources; however, the proposal indicated that actual emissions of
hydrogen cyanide (HCN) at a few facilities were near the major source
threshold. The commenter concluded that EPA violates both the CAA and
its own regulations by basing its evaluation of whether gold mines are
major sources on their actual emissions instead of their potential
emissions.
    The commenter further noted that the proposal requested comment on
a certification process that would allow gold mines to avoid major
source status whereby companies could certify that they are area
sources by implementing certain ``management practices'' and then
certifying to EPA that they had done so. The commenter stated that such
a certification process would be unlawful in calculating a sources
``potential to emit'' because the management practices are not
``control equipment,'' ``restrictions on hours of operation or on the
type or amount of material combusted, stored, or processed,'' and would
not be ``federally enforceable.''
    Other commenters supported EPA's conclusion and determination that
the gold mines are area sources of HAP. According to the commenters,
EPA's methodology in making this determination was extremely
conservative because EPA did not apply what the commenters believe to
be a key correction factor. Application of this correction factor would
have reduced the HCN emissions estimates from by approximately 40-50%.
The commenters also stated that fence line testing at selected gold
mine operations demonstrated that these levels of HCN were below all
applicable public health standards.
    The commenters believe that, because the gold mines are area
sources of HCN, they should not be subject to section 112 work practice
standards or newly developed certification requirements. The commenters
noted that it is not technically practical to set systematic work
practice standards to reduce HCN emissions for every gold mining
operation to follow because each mine is unique in its mineralogy and
cyanide leaching processes, and different process solution pH values
are necessary to enhance gold recovery.
    The commenters explained that for economic, health, and safety
reasons, they already implement work practice standards designed to
minimize HCN. The commenter concluded that the combination of these
work practice standards and the annual TRI reporting more than
adequately ensure that gold mining operations will remain area sources
of HCN.
    Response: Contrary to the assertions of one of the commenter's, EPA
did not state in the preamble to the proposed rule that the sources at
issue had actual emissions ranging from 5 to 9 tons. By contrast, EPA
stated that ``a few facilities are close to the major source threshold
due to hydrogen cyanide (HCN).'' 75 FR 22479. EPA failed to clarify in
the preamble to the proposed rule that the range of 5 to 9 tons
represented potential to emit calculations for the largest-emitting
sources. Specifically, as explained in the document ``Estimated
Emissions of HCN from Gold Mine Facilities in the U.S.'' (which is
available in the docket for this rulemaking), EPA estimated the
potential to emit for the five largest sources assuming that these
sources would be operating every day of the year, 24 hours a day, at
100 percent of its current capacity. These assumptions and calculations
resulted in a potential to emit estimate of 5 tons of HCN per year for
the largest source. EPA then completed a second set of calculations,
using the same assumptions (i.e., operating every day of the year, 24
hours a day, at full capacity), but without applying the surface area
correction factor, and those calculations resulted in a conservative
potential to emit estimate of 9 tons of HCN per year for the largest
source. The emission estimates for the remaining large facilities were
all below 9 tons.
    The commenters correctly point out that in determining whether a
source is a ``major source'' under CAA section 112, we must consider
the source's potential to emit, as well as its actual emissions. See
CAA section 112(a)(1) and 40 CFR 63.2. As noted above, we specifically
examined the sources' potential to emit and concluded that all sources'
potential to emit were below the major source thresholds.
    Some commenters allege that EPA significantly overestimated HCN
emissions from the larger sources by not accounting for certain
correction factors. They assert that if one were to account for the
appropriate correction factors in developing the potential to emit
values, HCN emissions would ``range from 3.7-4.5 tpy for the larger
mines compared to the 5-9 tpy estimate'' (See document titled ``PTE
Emission Estimates for HCN'' by the Nevada Mining Association, which is
available in the docket for this action). Other commenters make a
blanket, unsupported assertion that the Agency has underestimated HCN
emissions from the source category because they believe that without
the management practices currently employed by sources in the category,
HCN emissions would exceed the major source thresholds at the larger
sources. These latter commenters, however, made only conclusory
statements and did not demonstrate that HCN emissions from the larger
sources would exceed the major source thresholds if the management
practices were not employed.

    In sum, EPA has developed conservative estimates of the sources'
potential to emit HCN. At one end of the range EPA estimates potential
emissions of 5 tons per year of HCN for the largest source, which is
well below the major source threshold of 10 tons per year of a single
HAP. At the other end of the range EPA estimates potential emissions of
9 tons per year for that same largest source, which is a conservative
estimate and is still below the major source threshold. The emission
estimates for the remaining large facilities were all below 9 tons. We
understand that the sources at issue implement various management
practices as part of their operations to minimize the use and emissions
of cyanide to protect workers, to comply with Mine Safety and Health
Administration (MSHA) standards, to comply with their agreements to the
International Cyanide Code, and for economic reasons (to reduce
operational and supply costs). We currently do not have sufficient
information to explicitly quantify emissions reductions achieved
through these management practices, but nothing in the record suggests
that the facilities would be major sources if they failed to employ the
management practices. Accordingly, we are taking final action today to
list the gold mine ore processing and production area source category
and regulate its mercury emissions pursuant to CAA section 112(c)(6).
    Although not required, we intend to send letters to various Gold
Mining Processing and Production companies pursuant to Section 114 of
the Clean Air Act to confirm our conclusion that the sources' potential
to emit remain below major source thresholds.
5. Title V Permit Exemption
    Comment: In the proposal preamble, EPA solicited comment on whether
a title V exemption ``is appropriate under section 502(a) for any
particular sources in this category.'' One commenter offered the
following reasons for not exempting gold mines from title V permitting
requirements:
     EPA did not properly determine whether some or all sources
in the category are major sources by determining each source's
potential to emit.
     The CAA allows EPA to exempt area sources from title V
permitting only if it establishes that compliance with the title V
permitting requirements would be ``impracticable, infeasible or
unnecessarily burdensome.'' However, EPA does not claim that such
requirements are ``impracticable,'' ``infeasible,'' or ``unnecessarily
burdensome'' for gold mines.
     It is feasible and within the gold mining companies'
financial means to comply with title V permitting requirements.
    The commenter believes that the text and legislative history of the
CAA make plain that Congress intended ordinary citizens to be able to
get emissions and compliance information about air toxics sources and
to be able to use that information in enforcement actions and in public
policy decisions on a State and local level. According to the
commenter, Congress did not think that enforcement by States or other
government entities was enough; if it had, Congress would not have
enacted the citizen suit provisions. The commenter said that, if a
source does not have a title V permit, it is difficult or impossible
for a member of the public to obtain relevant information about its
emissions and compliance status or to bring enforcement actions. The
commenter stated that to the extent the informational and enforcement
benefits provided by title V permits can be considered a burden, these
benefits far outweigh that burden.
    The commenter also noted that title V provides important monitoring
benefits and that title V permits are necessary to provide adequate
monitoring. The commenter concluded by stating that the legislative
history of the CAA shows that Congress did not intend EPA to exempt
source categories from compliance with title V unless doing so would
not adversely affect public health, welfare, or the environment;
however, exempting gold mines from title V would adversely affect
public health, welfare and the environment by depriving the public of
important informational and enforcement benefits.
    One State agency commented that additional title V permitting would
subject both the source and the State agency to additional resource
burdens. The commenter points out that major sources of criteria
pollutant emissions are currently subject to title V permit
requirements in Nevada and that sources not subject to major source
permitting requirements are subject to Nevada's minor source permitting
program. In addition, the NMCP requires all mining sources to obtain
mercury-specific operating permits to construct. The commenter believes
that these permit programs would provide a strong basis for
implementing and enforcing any Federal MACT requirements for the gold
mining industry, and there would be nothing gained by subjecting these
sources to title V permitting.
    Several commenters stated that EPA should exercise its discretion
and exempt the gold mine ore processing and production industry from
the title V requirements as impracticable, infeasible, and
unnecessarily burdensome. The commenters said that, in light of EPA's
findings in other similar rulemakings for area sources, the four
factors set forth in the Exemption Rule support a finding that title V
permitting is ``unnecessarily burdensome'' for the gold mine ore
processing and production area source category.
    In discussing the first factor of the Exemption Rule, whether title
V would result in significant improvements to the compliance
requirements, the commenters said that the proposed NESHAP for the gold
mine ore processing and production area source category includes
extensive monitoring, recordkeeping, and reporting requirements that
are more comprehensive than title V requirements. The commenters
believe that Nevada regulations and permits provide an additional layer
of compliance assurance on the Federal NESHAP that obviates the need
for title V permitting. The commenters claimed that the additional
layering of title V does not ``significantly improve'' upon the
proposed and existing compliance requirements.
    Regarding the second factor in the Exemption Rule, whether title V
permitting would impose significant burdens on the area source category
and whether the burdens would be aggravated by any difficulty the
sources may have in obtaining assistance from permitting agencies, the
commenters said that there are extensive administrative burdens and
costs associated with the title V permitting process, including
mandatory activities that have been previously identified by EPA. The
commenters claimed that many of the area source gold mines are owned
and operated by small entities that are already required to comply with
comprehensive State permitting requirements for mercury emissions and
that requiring title V permits for them would result in resources being
redirected away from more useful and necessary efforts.
    The commenters explained that the third factor in the Exemption
Rule examines whether the costs of title V permitting for the area
source category would be justified, taking into consideration any
potential gains in compliance likely to occur for such sources. The
commenters claim that there do not appear to be any gains in compliance
to justify the additional costs that would be imposed on these area
sources from title V permitting

based on the lack of significant improvements in compliance
requirements and the substantial additional costs and burdens
associated with title V compliance.
    The commenters noted that the fourth factor in the Exemption Rule
analysis is whether there are implementation and enforcement programs
in place that are sufficient to assure compliance with the NESHAP for
the area source category, without relying on title V permits. The
commenters claimed that the proposed rule includes all necessary
monitoring to effectively implement its requirements, and the area
sources for the gold mine ore processing and production are already
permitted under State permit programs. According to the commenters, all
non-title V sources in Nevada are required to hold ``Class II''
operating permits that must contain, among other things, all applicable
emission limitations and standards. The commenters said that other
States where gold mine ore processing and production area source are
located either would be covered by a comparable delegated State air
program or by EPA.
    The commenters stated that EPA regularly provides title V
exemptions for area sources similar to gold mine ore processing and
production area sources and cited examples from the past year. The
commenters claim that the existing and proposed compliance and
monitoring requirements for the gold mines are generally more stringent
than those found in the other NESHAPs for which EPA has granted a title
V permit exemption.
    The commenters stated that exempting the gold mine ore processing
and production area source category from title V permitting will not
adversely affect public health, welfare, or the environment because
title V permits do not generally impose substantive air quality control
requirements. According to the commenters, requiring title V permits
also carries the potential of adversely affecting public health,
welfare, or the environment by shifting State agency resources away
from ensuring compliance with a program that is reducing mercury
emissions from gold mines.
    The commenters stated that EPA should exempt the gold mine ore
processing and production area source category from title V permitting
requirements, and at a minimum, should exempt area source gold mines
that are subject to Nevada's comprehensive mercury control program.
    Response: After reviewing the comments, we continue to believe that
it is appropriate that all gold mine ore processing and production
facilities be required to obtain title V permits. Most of the other
area source categories for which we have provided title V permit
exemptions have hundreds or thousands of facilities that are mostly
owned by small businesses. In contrast, there are an estimated 21
facilities that are subject to this final rule, and, based on our
research and analyses, none of the facilities are owned by small
businesses; most of these facilities are owned by large, and in some
cases, multi-national, corporations. Therefore, we conclude that the
argument of financial burden, which has supported title V exemption for
other source categories, does not apply to the gold mining industry
(see Economic and Small Business Analysis, which is available in the
docket).
    Currently, it is our understanding that 7 of the 21 facilities that
will be subject to the final rule already have title V permits (5 in
Nevada and 2 in other states). Further, there are approximately 5
facilities in all other States (i.e., except Nevada) that do not
currently have title V permits that will be subject to this final rule,
so title V permitting will apply to no more than a few facilities in
any one of these other States. Therefore, we do not believe the
requirement for title V permitting will be overly burdensome to the
permitting authorities in those States. Although there are more
facilities in Nevada that will be subject to the final rule, as the
commenters point out, Nevada already has an effective permitting system
in place. Five of the 14 gold mine facilities in Nevada already have
title V permits. Because of Nevada's existing permitting system and
experience with title V permitting, we do not think that it is an undue
burden on the State of Nevada to require title V permits from the other
gold mine facilities located within the State. We also think it is
important for the public in States where these facilities are located
to have access to emissions and monitoring data and the opportunity for
public involvement in the permitting of these facilities that is
provided by title V permitting.
6. Reconstruction
    Comment: Several commenters believe it is appropriate to group
under each of the umbrella ``affected sources'' all the equipment
associated with each particular process in order to ensure a reasonable
application of the reconstruction provisions found in the General
Provisions. The commenters asked that EPA reaffirm that the 50 percent
fixed capital cost trigger for determining reconstruction would be
measured against all equipment components needed for the defined
processes, and that reconstruction at one affected source as defined in
the standard will not affect or result in reconstruction at another
affected source.
    The commenters also noted that the definition of ``reconstruction''
authorizes EPA to establish special provisions in a particular standard
for the application of the reconstruction criteria to the affected
source. The commenters said that the ``carbon processes'' affected
source illustrates that the affected source can consist of several
pieces of interconnected equipment that together constitute the process
line, and it can be anticipated that production needs will give rise to
the need to add more pieces of equipment to an existing carbon process
line or even to install a whole new carbon process line. The commenters
provided three examples: Adding a new component to an existing carbon
processes group; construction of a new carbon group due to expansion at
a facility that has an existing carbon group; and installation of new
pollution control equipment. The commenter said that consideration of
whether or where new MACT requirements should apply in these examples
warrants the development of special reconstruction provisions in this
standard, or EPA should clarify that the three examples would not be
considered reconstruction under the proposed rule.
    The commenters asked that EPA either clarify that the three
examples would not be considered reconstruction, or alternatively, add
the following provisions to the proposed rule: (1) An addition of a new
piece of equipment to address production requirements is not considered
a reconstruction, (2) the expansion of a facility by the construction
of a completely new process line will not be considered a
reconstruction of an existing process line, and (3) the installation of
air pollution control equipment to comply with this standard is not
considered a reconstruction.
    Response: The determination of what constitutes a reconstruction is
directly tied to the definition of the affected source and the
definition of reconstruction in the part 63 General Provisions:

    Reconstruction, unless otherwise defined in a relevant standard,
means the replacement of components of an affected or a previously
nonaffected source to such an extent that:
    (1) The fixed capital cost of the new components exceeds 50
percent of the fixed capital cost that would be required to

construct a comparable new [affected] source; and
    (2) It is technologically and economically feasible for the
reconstructed source to meet the relevant standard(s) established by
the Administrator (or a State) pursuant to section 112 of the Act.
Upon reconstruction, an affected source, or a stationary source that
becomes an affected source, is subject to relevant standards for new
sources, including compliance dates, irrespective of any change in
emissions of hazardous air pollutants from that source.

    For each of the four affected sources in the final rule, we have
defined the affected source as the collection of processes associated
within each affected source. Consequently, if one process within the
affected source is upgraded or replaced with a new process, the 50
percent fixed capital cost criterion would be based on the fixed
capital cost of replacing all processes in the affected source, not
just the capital cost of the process being upgraded or replaced. For
example, if a new carbon kiln is added to an existing group of carbon
processes with mercury retorts, the capital cost of the new carbon kiln
would be divided by the fixed capital cost of constructing a comparable
new affected source containing all of the processes within the existing
affected source of carbon processes with mercury retorts to calculate
the percent for comparison to the 50 percent criterion.
    With regard to the scenario where a new carbon process with a
mercury retort is installed, the affected source is defined as the
collection of all applicable processes within the affected source, and
because of this, a facility could not have two carbon processes with
mercury retorts affected sources, such as the commenter suggested,
where one group is new and the other is existing. For example, if a new
group of carbon processes with mercury retorts is installed at a
facility in addition to an existing group of carbon processes with
mercury retorts, the two groups (all carbon processes with mercury
retorts at the facility) collectively would be a single affected
source. In this case, the fixed capital cost criterion would be based
on the fixed capital cost of replacing the existing affected source
with a comparable new affected source, and if the new processes exceed
50 percent of that cost, all of the carbon processes with mercury
retorts would be subject to the new source limit for carbon processes.
There would not be separate and different emission standards for the
two sets of carbon sources with mercury retorts (the older group and
newer group) because the collection of all of these processes is the
affected source.
    We do not see a necessity to provide criteria for this final rule
that are different from the requirements in the General Provisions for
determining what constitutes a reconstruction. We also think it is
appropriate to exclude the cost of emission control equipment from the
cost calculation for reconstruction determinations.

B. Applicability

    Comment: Several commenters stated the rule should exempt
individuals (prospectors), laboratories, small mining operations, and
non-leaching operations. The commenters urged EPA to include in the
final rule all of the following exemptions to avoid the problem of
unintended regulation of sources that were not meant to be included in
the source category: Gold mining operations that produce less than 100
pounds of concentrate per year, which would exempt analytical labs that
perform small bench scale processing tests on gold ores; gold mining
operations that do not leach or dissolve gold, which would exempt
placer and other non-leaching operators, including both small
commercial efforts as well as individual recreation-type prospectors;
and gold mining operations that process less than 1,000 tons per year
of gold ore, which would exempt certain small scale pilot plants and
related testing operations. The commenters said that the exemptions
suggested above will not reduce in any way the effectiveness of the
proposed rule in controlling mercury emissions from the targeted larger
mines, nor will they lead to increased mercury emissions, but they will
exclude regulation of a large number of small operators who do not emit
any significant mercury.
    Response: Section 63.11640(c) of the proposed rule provides that
the emissions standards for this area source category do not apply to
research and development facilities, as that term is defined under CAA
section 112(c)(7). We did not receive any adverse comments concerning
this provision, and are finalizing the provision in this rule.
    Further, as mentioned above in section IV, we are clarifying in
this final rule that this area source category does not include
individual prospectors and very small pilot scale mining operations.
Prospectors and other very small pilot-scale operations (e.g.,
operations that produce or process less than 100 pounds of concentrate
per year) are very small and were not included in the section 112(c)(6)
inventory that was the basis for the listing of gold mine ore
processing and production source category. We believe that emissions
from the very small scale operations described above to be very
minimal.
    By contrast, the commenter's suggested 1,000 tons/yr ore threshold
may include operations beyond the very small scale pilot operations
discussed above. We believe that the 100 pounds of concentrate per year
more appropriately reflect these very small scale operations.
    We are not making the suggested change of excluding operations that
do not leach or dissolve gold because certain gold mine facilities in
the source category use flotation or gravity flotation processes and
perform thermal processing of concentrate in melt furnaces, which can
have significant emissions of mercury. However, as mentioned above we
are clarifying that this final rule does not apply to these very small
scale operations.

C. MACT Floors

1. Consideration of Variability in Determining Floors
    Comment: One commenter acknowledged that EPA may consider
variability in calculating the best sources' performance, but stated
that EPA's method of considering variability seeks to assure that none
of the sources among those identified as best performers would ever
exceed the floor level. The commenter claims that such an approach
ignores the reality that sources' emission levels are largely within
their control, and although a great deal of variability may be
statistically conceivable if EPA chooses a high enough prediction limit
(in this case the 99th percentile) that does not mean that a well-
operated source actually would experience such variability. The
commenter said that one of the main points of having emission standards
is to ensure that sources not only deploy the appropriate control
measures, but also use those control measures consistently to minimize
emissions.
    The commenter said that using an upper prediction limit to set
standards reflecting the statistical worst performance these sources
could have in a purely statistical sense does not yield an accurate
picture of the best sources actual performance, and it is especially
arbitrary in the absence of any explanation of why EPA thinks that the
relevant best sources' performance would ever be so bad, other than the
fact that it is statistically possible.
    Response: As described previously, the MACT floor limits are
calculated based on the performance of the lowest

emitting sources in each of the MACT floor pools. We ranked all of the
sources for which we had data based on their emissions and identified
the lowest emitting sources.
    As the commenter concedes, EPA can consider variability in
assessing sources' performance when setting MACT standards. See Brick
MACT, 479 F.3d at 881-82; and Mossville Envt'l Action Now v. EPA, 370
F.3d 1232, 1241-42 (D.C. Cir 2004) (reaffirming that EPA can assess
variability in determining the level of emissions control achieved by
the best performing sources).
    Variability in facilities' performance has various causes. One
source of variability for these facilities is the differing mercury
concentrations in the input materials. Another source of variability is
due to normal variations in performance of the control devices for
which both run-to-run and test-to-test variability must be
accounted.\4\ A review of the run-by-run emissions data in the record
shows that emission rates from one run to the next for well-operated
sources can vary by as much as a factor of 8. We need to account for
sources' variability (both due to control device performance and
variability in inputs) in assessing sources' performance when
developing technology-based standards. Accordingly, EPA accounts for
variance in test data, between units, and among facilities when
developing the MACT standard.
---------------------------------------------------------------------------

    \4\ Run-to-run variability is essentially within-test
variability, and encompasses variability in individual runs
comprising the compliance test, and includes uncertainties in
correlation of monitoring parameters and emissions, and imprecision
of stack test methods and laboratory analysis. 72 FR at 54877 (Sept.
27, 2007). Test-to-test variability results from variability in
pollution device control efficiencies over time. Test-to-test
variability can be termed long-term variability. 72 FR at 54878.
---------------------------------------------------------------------------

    In determining the MACT floor limits, we first determine the
average emissions of the top performers based on available data. We
then assess variability of the best performers by using a statistical
formula designed to estimate a MACT floor level that is equivalent to
the average of the best performing sources based on future compliance
tests. Specifically, the MACT floor limit is an upper prediction limit
(UPL) calculated with the Student's t-test. The Student's t-test has
also been used in other EPA rulemakings (e.g., NESHAP for Cement
Manufacturing, NSPS for Hospital/Medical/Infectious Waste Incinerators,
and NESHAP for Industrial, Commercial, and Institutional Boilers and
Process Heaters) in accounting for variability. A prediction interval
for a future observation is an interval that will, with a specified
degree of confidence, contain the next (or some other pre-specified)
randomly selected observation from a population. In other words, the
prediction interval estimates what the upper bound of future values
will be, based upon present or past background samples taken. The UPL
consequently represents the value which we can expect the mean of
future observations (i.e., emission test runs) to fall below within a
specified level of confidence, based upon the results of an independent
sample from the same population. In other words, if we were to randomly
select a future test condition from any of these sources (e.g., average
of 3 runs) we can be 99 percent confident that the reported level will
fall at or below the 99 percent UPL value. We note that the methodology
accounts for both short-term and long-term variability and encompasses
run-to-run and test-to-test variability.
    For this rule, we used the 99 percent UPL analysis on the emissions
data for the top performing sources to account for the variance. In the
context of determining the MACT floor, the 99 percent UPL represents
the value below which the mean of future compliance tests (based on,
for example, a 3-run average) would fall 99 percent of the time. A 99
percent level of confidence means that a facility, whose emissions are
consistent with the best performing sources, has one chance in 100 of
exceeding the emission standard.
    We believe that using the 99 percent UPL is appropriate for this
rule. As noted above, this approach is consistent with several other
previous rulemakings. It also makes sense from a practical standpoint.
If we selected a lower number (e.g., 95 percent UPL) this would mean
that a best performing source that is performing at the MACT level of
control would potentially exceed the limit 5 percent of the time--which
we do not believe is a reasonable approach for this rule. See
Mossville, 379 F.3d at 1241-42); see also 70 FR at 59438 (Oct. 12,
2005) (explaining use of 99th percentile). With regard to the
commenter's statement that no sources among the best performers would
ever exceed the MACT standard, we believe this is incorrect. The
commenter provided no basis for this statement, and we do not believe
the commenter based this statement on an analysis of the variability in
the data.
    We do not believe that the UPL analysis reflects the statistical
worst performance the top five performing sources could have. The UPL
calculation is dependent on the data that we have, and reflects the
actual variability in the test data for the best performing sources. It
does not reflect worst-case performance. We continue to believe that
the UPL does yield an accurate picture of the best sources' performance
as best as possible with taking into account variance between the
facilities, units at the facilities, and between test runs for the
different units (including variability in input materials).
    Furthermore, although the average of several data sets may show a
top performing source meeting the emission standard by a significant
margin, the variability in emissions inherent in any one compliance
test could easily indicate much higher emissions, and, in some cases,
an exceedance of the emission standard. We continue to believe that the
UPL analysis evaluated at 99 percent confidence is appropriate for this
source category.
    Moreover, we believe the data we used to calculate the MACT
standards are representative of the normal performance of the best
performing sources for several reasons. First, the test results that we
are using in our MACT database are tests conducted under Nevada's
mercury emission control program, and are conducted to determine
whether a facility is in compliance with State requirements. Facilities
typically try to perform as well as they can during such tests. State
(and often EPA) permitting authority staff are notified before a
performance test is conducted to provide an opportunity to attend and
observe the test, and they often attend to ensure the source is
operating properly and that the testing is performed according to the
strict requirements in the codified test methods.
    Test reports are carefully reviewed by the permitting authority,
and any failure to follow the test method or abnormal operation of a
source is flagged. These data are usually invalidated, and invalidated
tests are not used in our MACT standard calculations. For example,
several tests from these facilities were invalidated by the NDEP
because the specified testing procedures were not followed or the
emission control device was not operating properly, and we have not
used those results in our analysis for those reasons. We have collected
additional data from test reports not available at the time of
proposal, and one of those tests was invalidated because NDEP
representatives discovered that the emission control device was not
operating properly during the test. Therefore, we also did not use
those test data.
    The commenter believes that floors must be set at the average
emission level

achieved by the best performers when they are operating properly. We
agree that the performance data characterizing the emission level
achieved by the top performers must be data obtained when they are
operating properly, and we believe that is the case for our current
database for this source category.
    As described above, the MACT floor is based on the average
performance of the top performers plus an amount to account for
variability. We have appropriately developed a MACT standard based on
emissions from the top 5 best performing sources that accounts for
variability because, over an extended period of time, the emissions
from each of these best performing facilities (even the best
controlled) will vary above and below the facility average. For
example, we expect that about half of the duration of the year the
emissions from a best performing facility would be somewhat below their
average and that about half of the duration of the year their emissions
would be somewhat higher than their average. If we set the MACT limit
exactly equal to the average emissions level achieved by the best
performers (without accounting for variability), and we had a source
that was performing at exactly the MACT level over the course of the
year, the measured emissions level on roughly half the days of the year
would suggest that the source is emitting at levels above the MACT
limit, and on about half of the other days of the year the measured
emissions level would suggest that the source is emitting at levels
less than the MACT limit. We reasonably and appropriately accounted for
variability in the data consistent with established statistical theory
and practice and judicial precedent. Finally, ignoring variability of
the best performing sources and using only the average performance
would virtually guarantee that some of even the best performers would
exceed the floor limit at least some of the time.
    Thus, we developed a MACT standard based on the average of the best
performing sources that accounts for variability. We accomplished this
by calculating the MACT standard from this average performance and
accounting for variability by using the 99 percent UPL. The specific
calculations are presented in the MACT floor document in the docket for
this rulemaking. Furthermore, we agree with the comment that one of the
points of having emission standards is to ensure that sources not only
deploy the appropriate control measures, but also use those control
measures consistently to minimize emissions. We believe that the MACT
standards established in this rule along with the requirements to
monitor and maintain control device parameters within certain ranges
will ensure control measures are applied consistently to minimize
emissions.
    Comment: Another commenter stated that consideration should be
given to defining the inherent range of measurement error and requiring
more test runs in order to reduce variability due to process variation.
The commenter said that this would also better clarify when variability
was due to operational controls, which could be addressed, rather than
due to factors that cannot be controlled, such as mercury content in
the ore. The commenter asked for clarification on how inconsistent runs
should be treated, what defines an acceptable set of runs, and at what
point more runs would be required to provide reliable data.
    The commenter also stated that the degree of variability allowed in
the development of the new source limit for ore pretreatment appears to
be out of line with the new source limits for carbon processes and non-
carbon processes. The commenter believes that ore pretreatment
variability for new sources is higher than existing sources because low
thermal units were included in the same category, high emissions were
allowed in the data set, and variable emissions were allowed in data
set. The commenter recommended that, if EPA continues to use Goldstrike
as the best performing source for new source MACT, then they should re-
evaluate and reduce the variability to be equal to or less than the
variability for existing sources.
    Response: We agree with the commenter that the testing process
would be more accurate if the number of test runs was increased.
However, we balance several factors in determining the minimum number
of runs required, and because the compliance testing is supplemented by
various types of continuous or periodic parametric monitoring, we have
concluded that three test runs are appropriate for this final rule.
Although we have not proposed a formal procedure to assess the
consistency of test runs, the permitting authority performs routine
reviews of compliance test data to identify potential outliers and
results that suggest further investigation is needed. For example, a
routine review tracks trends in performance, and in particular, flags
any trends in deteriorating performance over time. An unusually high
run among the three runs also attracts attention and would be examined
to determine if it might have been caused by a problem with the
process, control device, sampling, or analysis. If the permitting
authority identifies inconsistent runs, they have the authority to
invalidate any or all runs. A source would be required to perform more
runs to provide reliable data if two to three runs were invalidated.
    We agree with the commenter that the degree of variability used in
the development of the proposed new source MACT standard for the ore
pretreatment group appeared to be inconsistent with the degree of
variability used in the development of the proposed new source MACT
standard for carbon processes and non-carbon concentrate processes. We
agree with the commenter that the ore pretreatment degree of
variability at proposal for new sources was higher than the degree of
variability for existing sources. We do not believe that the
variability was higher because low thermal units (i.e., autoclaves)
were included in the same category, but because two tests of the ore
preheater/dry grinding processes at Goldstrike were allowed in the data
set. These tests had, as the commenter identified, inconsistently high
emissions (as compared to other tests at other times for the same
units) and inconsistent variability between the runs. We have
determined that the tests the commenter is referring to are not
representative of normal operation, and those tests have been removed
from our database because the NDEP invalidated the tests due to
possible sample contamination. (See the MACT Floor Document in the
docket for the final rulemaking for more details). We continue to use
Goldstrike as the best performing source for the ore pretreatment new
source MACT, and the variability for new source MACT is now less than
that of the variability for existing source MACT, and is less than the
variability calculated at the time of proposal.
2. General Comments on MACT
    Comment: Some commenters stated that the MACT floor already
represents installation and operation of MACT controls, and the use of
emissions data from facilities that are already controlling their
mercury emissions creates an artificially low MACT floor. The
commenters said that the low MACT floor penalizes facilities that
voluntarily invested in pollution control technology and creates a
substantial disincentive for industry and States to move ahead of EPA
in reducing emissions of HAP.
    Response: We acknowledged at proposal that many gold mine
facilities are already well controlled for many

reasons, including participation in the NMCP. We also acknowledge that
the top performing facilities that are the basis for the MACT floor
calculation are the top performers because they have installed
controls. CAA section 112(d)(3)(B) requires that, for a category with
fewer than 30 sources, the MACT floor not be less stringent than ``the
average emission limitation achieved by the best performing 5 sources
(for which the Administrator has or could reasonably obtain emission
information).'' (Emphasis added). EPA has information on the well-
controlled facilities and used the information to conduct MACT floor
analysis, as required by the CAA. Although the MACT floor may be
considered more stringent in comparison to floors that would have been
established if no facilities had mercury emission controls, we do not
consider the floor to be ``artificially low'' because consistent with
the statute, it reflects the level achieved in practice by the best
performing sources. See 112(d)(3). We do not believe that the MACT
floor penalizes facilities that invested in pollution control
technology because those facilities will be able to meet the MACT
standards. We do not consider that this final rule creates a
disincentive for industry and States to move ahead of EPA in reducing
HAP emissions because as facilities reduce mercury emissions by adding
controls required by State programs, they will be able to meet the
NESHAP. Most of the facilities that will not meet the current final
standards have already proposed to add controls to their units in their
Phase 2 applications for the NMCP.
3. MACT for the Ore Pretreatment Group
    Comment: Several commenters supported EPA's general approach to
establish three groups of affected sources in the proposal. On the
other hand, several commenters suggested that EPA develop separate
emission standards for roasters and autoclaves for existing and new
sources. One commenter stated that roaster and autoclave processes are
different from each other based on the mercury species released,
controls utilized, and their rates of mercury emissions. The commenter
said that roasters commonly reach temperatures of 400[deg] to
700[deg]C, releasing gaseous elemental mercury, whereas autoclaves
commonly reach temperatures of 175[deg] to 230[deg]C producing reactive
gaseous mercury and sulfate and forming mercury sulfate. According to
the commenter, autoclaves are expected to be able to improve efficiency
over time. The commenter noted that roasters produce one to two orders
of magnitude higher emissions than do autoclaves. The commenter
believes that facilities that only use autoclaves should not be allowed
the leeway to emit at the rate that facilities employing roasters are
allowed. The commenter recommends that the ore pretreatment group be
divided into high temperature pretreatment processes (roasters) and low
temperature pretreatment processes (autoclaves and ancillary roaster
processes, such as dry grinding, pre-heating, and quenching).
    Response: We discussed in section V.A. of the preamble to the
proposed rule our rationale for establishing the different affected
sources, including the ore pretreatment processes affected source. We
believe it is appropriate to maintain the ore pretreatment group
affected source, as we had proposed. We do not agree with the comment
that roasters necessarily have higher emissions that are one to two
orders of magnitude higher than emission from autoclaves. The available
data show a wide range in emissions from autoclaves (from 0.4 to 115
lb/million tons of ore). This range overlaps the range for roasters and
their ancillary equipment, which have combined emissions between 42 to
71 lb/million tons of ore. Regardless of the mercury species released,
controls utilized, operating temperatures, or control efficiency over
time, autoclaves and roasters process the same input material (i.e.,
ore) and are intended for the same purpose (i.e., to oxidize the ore).
Therefore, we believe that it is appropriate to maintain the ore
pretreatment affected source as we had proposed, keeping roasting
operations and autoclaves together.
    Comment: One commenter stated that EPA failed to consider beyond-
the-floor standards for roasters and that if additional reductions are
achievable at roasters, then EPA must set additional beyond-the-floor
standards for roasters.
    A commenter also stated that although EPA's standard for new ore
pretreatment facilities is as high as its standard for existing
facilities, EPA does not propose or discuss setting beyond-the-floor
standards for new sources. The commenter claims that EPA has a
statutory obligation to ensure that its new source standards reflect
the maximum achievable reduction in emissions.
    Response: Following proposal, we continued to investigate the
performance of facilities with ore pretreatment processes and
opportunities for additional control. We collected data from more
recent tests that were not available at proposal, and these new data
show that emission control performance at these facilities has
continued to improve. We identified two previous tests in the proposal
database that were suspect, and we confirmed with NDEP that these tests
should be invalidated and not used in the analysis because of possible
sample contamination. We have also dropped the data for one facility
from the analysis because their autoclave was shutdown in 2007 and
dismantled, and we only had one test of the autoclave when it was
operating in 2006. For these reasons, we did not include data for that
facility in the analysis, which is now based on the only four
facilities currently operating.
    Based on the addition and change described above with respect to
our available data, we revised the MACT floor analysis for the ore
pretreatment processes. The revised MACT floor for existing sources
decreased from 175 lb/million tons at proposal to 158 lb/million tons,
and the new source MACT floor dropped from 163 lb/million tons to 84
lb/million tons.
    The MACT floor limit for existing ore pretreatment processes is
based on the use of calomel-based mercury scrubbers on roasters and wet
scrubbers on autoclaves and ancillary roaster operations. We conducted
a beyond-the-floor analysis during the development of the proposed
rule. The roasters were already equipped with very good mercury
controls (condensers and calomel-based mercury scrubbers), and we did
not identify any beyond-the-floor options for the roasters. However, we
identified as a beyond-the-floor control for autoclaves the
installation of both a refrigeration unit (or condenser) and a carbon
adsorber. We continue to believe that the roasters stacks are well
controlled, but since our proposal, we have identified a beyond-the-
floor control option (carbon adsorption) for the ore pre-heaters/dryers
(ancillary roaster operation) that could achieve additional emissions
reductions of approximately 70 percent (or more) for those units. Two
of the three facilities with roasters have already proposed in their
NMCP Phase 2 permit applications to apply controls to their preheaters/
ore dryers, and these two companies have submitted cost estimates for
applying a carbon adsorption system. Using the cost estimates submitted
by the affected facilities, we estimate the capital costs for control
of roaster preheaters/dryers for the three facilities with roasters as
$3 million with a total annualized cost of $1.6 million per year. We
also estimate a reduction of 118 lb/yr of mercury emissions would be
achieved at an overall cost effectiveness of about $13,800 per pound of
mercury. We

believe that these costs and cost effectiveness are reasonable. As
required under CAA section 112(d)(2), we have also considered non-air
quality health and environmental impacts and energy requirements of
this additional control. We conclude that this is an acceptable beyond-
the-floor control technology for existing roaster preheaters/ore
dryers. Therefore, we included the beyond-the-floor control for ore
preheaters/dryers, as well as the beyond-the-floor control for
autoclaves, in determining the MACT standard in this final rule for
existing sources of ore pre-treatment processes. After applying the
appropriate variability analyses to the data, we determined that the
MACT standard for existing sources is 127 lb/million tons of ore.
    As mentioned above, we have revised the new source MACT floor. We
also did a beyond-the-floor analysis for new sources in the ore pre-
treatment processes group. However, we did not establish the MACT
standard for new sources based on this beyond-the-floor analysis
because we did not identify a feasible and cost-effective option to
achieve reductions greater than the new source MACT floor. Therefore,
for new sources of ore pretreatment processes, the MACT ``floor'' is
the MACT standard for the affected source. The final new source MACT
standard is 84 lb/million tons of ore, which is considerably more
stringent compared to the proposed standard of 149 lb/million tons of
ore and reflects the maximum achievable reduction in emissions.
    Comment: One commenter stated that the proposed estimated capital
costs of $890,000 and total annualized cost of $720,000 for beyond-the-
floor autoclave controls are not representative of actual costs of
installing a refrigeration unit (or condenser) and a carbon adsorber on
autoclaves. The commenter estimates that capital costs for autoclave
controls will range from $18 million to at least $30 million, and
annual operating costs could range from $2 million to $60 million,
depending on which controls, if any, are determined to be technically
feasible. The commenter believes that based on these cost estimates,
beyond-the-floor MACT controls would be cost prohibitive and are not
justified for the ore pretreatment affected source group.
    Another commenter estimated that for the installation of carbon
adsorbers on their autoclaves to control mercury emissions, the capital
costs would range from $30 million to $35 million, annual operating
costs would be $2 million per year, and the annual energy requirements
would be 11,400 megawatt-hours per year with an annual energy cost of
$900,000.
    Response: After reviewing the new cost estimates provided by the
commenters, we agree that capital and total annualized cost estimates
of the beyond-the-floor controls on autoclaves in the proposal were
underestimated. We evaluated the detailed cost estimate based on an
engineering study for a carbon adsorption system provided by one of the
commenters (see details in the comment above on capital, operating, and
energy costs), and our review of these details indicates it to be a
reasonable cost estimate and more representative. Therefore, we have
used this estimate as the basis for our estimate of the costs of the
beyond-the-floor mercury emission controls for autoclaves. Our revised
estimates are that the capital cost for installing carbon adsorbers on
autoclaves would be $29.3 million, with a total annualized cost of $4.9
million per year, which would result in an estimated reduction of 431
lb/yr of mercury emissions per year and an overall cost effectiveness
of about $11,000 per pound of mercury. Based on these new costs and
estimated reductions we conclude that the beyond the floor controls are
affordable and justified for the ore pretreatment affected source.
    Comment: Several commenters noted that, at the proposed new source
MACT limit of 149 pounds/million tons of ore, the proposed new source
Donlin Creek Mine, located in Alaska, would be allowed to emit 3,200
lb/yr of mercury based on a projected production rate of 22 million
tons/yr of ore.
    Response: With respect to this proposed new gold mine in Alaska,
the commenters' estimate of 3,200 lb/yr of mercury emissions is
inaccurate and a significant overestimate for a number of reasons. The
two primary reasons are that, based on available information, if the
facility is built, only an estimated 15 percent of the ore mined will
be processed in autoclaves (not 100 percent as assumed by the
commenters), and that the commenters' estimate is based on assuming
that the average emissions level for the facility throughout the year
would be at the maximum allowed at the proposed new source limit (149
lb/million tons of ore), which has been significantly reduced since
proposal.
    With the new source MACT standard in the final rule that is about
two times more stringent (i.e., lower) than the proposed MACT standard,
along with corrections described above, we estimate that far less than
3,200 lb/yr would be emitted from this new source if it is ever built.
Assuming continuous operation for 365 days per year, an estimated 21.5
million tons/yr of ore mined, about 3.2 million tons/yr processed in
autoclaves (15 percent), and assuming the source would emit at the
average emission level used to calculate the revised new source MACT
(45 lb/million tons of ore), we calculate that mercury emissions would
be about 144 lb/yr, which is about 5 percent of the estimate provided
by the commenters. Considering that the facility has yet to go through
the permitting process and that, if it is built, it will likely include
emissions controls that would reduce the emissions below 45 lb/million
tons of ore, we believe that, if the facility is built, emissions would
quite likely be lower than 144 lb/yr.
4. MACT for Carbon Processes
    Comment: Several commenters objected to including Facility M in the
MACT floor determination for new and existing sources in the carbon
processes affected source because it is not representative of, or
similar to, other sources, because it has unusually low mercury
concentrations in its ore, and no need for a retort to remove and
recover mercury. They noted that, because the mercury content of the
gold ore is fixed, the only way for other facilities to reduce
emissions of mercury is to apply mercury emission controls, but, for
many facilities, emission controls will not be enough to meet the
proposed MACT standard. The commenters stated they were aware that the
DC Circuit Court had constrained EPA's discretion to set floors that
fail to consider material inputs, but they said gold mines were
different from the remanded source categories (brick kilns and cement
kilns) because gold mining operations process very large quantities of
ore, and the ore is the only material input that results in mercury
emissions. The commenters stated that, in adopting section 112,
Congress expressly cautioned EPA against setting standards that would
require mining operations to change the ore used as essential
feedstock. The commenters said that, by ignoring the mercury content in
the ore being mined and processed at the facilities in the MACT floor
determination, EPA is requiring facilities to consider the substitution
of, or changes in, the ore that is processed because there is no other
way to achieve the standard. The commenters recommended that EPA
address, as a threshold matter, the differences in processing and
emissions across facilities that result from the variable concentration
of mercury in ore. The commenters recommended that Facility M not be
considered the ``best controlled similar source'' for purposes of
setting the new source MACT floor because the

facility is not similar to other sources. The commenters stated that,
if EPA does not exclude from the source category facilities that do not
use retorts to process concentrate, then they should subcategorize
them.
    Response: After consideration of comments and a re-examination of
the design of the facilities at issue, the emission controls, and other
factors affecting emissions from the carbon processes at Facility M, we
agree that this facility is quite different and unique compared to most
other gold mine ore processing and production facilities, including
other facilities in Nevada, in its carbon process. The difference is
manifested in the processing train in that mercury retorts are not
needed or used at Facility M to recover mercury. As the commenter
notes, the CAA allows EPA to ``distinguish among classes, types and
sizes of sources within a category'' in developing MACT emission
standards, and gold mine facilities without mercury retorts are
different in both class and type from those with mercury retorts.
Accordingly, in the final rule, we identify and set separate MACT
standards for these two different types of carbon processes: those that
use mercury retorts; and those, such as the carbon process at Facility
M, that do not use mercury retorts.
    As part of our re-analysis of the MACT floor and the MACT for
sources that are in the carbon processes with mercury retorts group and
sources that are in the carbon processes without mercury retorts group,
we considered new data that were not available at the time of proposal.
Over the past one to two years since our data collection effort for the
proposal, facilities in Nevada have continued to add controls and
improve emission control as part of the NMCP. The new data indicate
there were two facilities with carbon processes without mercury retorts
operating in 2009. Using the data from these two facilities, we
determined that the MACT floor limits for carbon processes without
mercury retorts are 0.17 lb/ton of concentrate for existing sources and
0.14 lb/ton of concentrate for new sources (based on the best
performing facility, Facility M).
    In our beyond-the-floor analysis, we considered the addition of a
carbon adsorber on an uncontrolled emission unit within an existing
affected source. We estimate the capital cost as $210,000 with a total
annualized cost of $72,000 per year, an emission reduction of 1.63 lb/
yr of mercury, and a cost effectiveness of $44,000/lb of mercury. We do
not believe that the small emission reduction that this control option
would achieve is justified in light of its cost. We therefore decided
not to go beyond-the-floor. We also considered possible beyond-the-
floor options for new carbon processes without mercury retorts, but
concluded these options were not cost-effective or feasible. Therefore,
for new and existing sources of carbon processes without mercury
retorts, the MACT floor limit is the MACT standard for this affected
source.
    As part of our re-analysis for the carbon group processes with
mercury retorts, we collected and evaluated additional data. As
discussed above, several of the facilities have improved emission
control over the levels observed in the database we used at proposal.
Two facilities with newly-installed controls replaced two higher-
emitting facilities that were in the top 5 at proposal, and all three
of the other facilities that remained in the top 5 had lower levels of
emissions after considering the new data. The results are that the MACT
floor limits for carbon processes with mercury retorts are 2.2 lb/ton
of concentrate for existing sources and 0.8 lb/ton of concentrate for