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6560-50-P

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 9 and 63

[EPA-HQ-OAR-2010-0239; FRL-9140-7]

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.

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. EPA proposed these 

actions on April 28, 2010 (75 FR 22470). 

DATES: This final rule is effective on [INSERT DATE OF

PUBLICATION IN THE FEDERAL REGISTER].

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 www.regulations.gov website. Although listed 

in the index, some information is not publicly available, e.g., 

Confidential Business Information (CBI) or other information 
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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 (202) 566-

1744, and the telephone number for the Air and Radiation Docket

and Information Center is (202) 566-1742.

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 

(919) 541-7912; fax number (919) 541-3207, e-mail address: 

french.chuck@epa.gov. 

SUPPLEMENTARY INFORMATION:

The information presented in this preamble is organized as 

follows:

I. General Information

A. Does this action apply to me?
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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

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:
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Category NAICS 

code1

Examples of 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: 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 
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(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: 

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 [INSERT DATE 60 DAYS AFTER

PUBLICATION IN FEDERAL REGISTER]. 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
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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 
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established under CAA section 112(d)(2), which requires 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 beyondthe-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 
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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 §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 

proposal1; (2) additional analyses in response to public comments 

on the proposed rule2

 

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.

; 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 

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”).

Comment [ger1]: Interagency 

reviewer said: “Somewhere in this 

front section, EPA should provide a 

footnote and clear link to where 

the new test data can be found in 

the docket.”

EPA Response: Okay, we added 

footnote. 

Comment [ger2]: Interagency 

reviewer said: 

“Please note where this analysis 

can be found”

EPA Response: Okay, we added a 

footnote.
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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).

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 

Comment [ger3]: Interagency 

reviewer said: “Since this rule 

needs to stand on its own, it may 

be helpful to present the 

requirements/statutory language for 

creating the MACT floor and beyond 

the floor standards. All that 

introduction seems to be missing 

from this preamble.”

EPA response: Okay. We added a 

section above to explain this. 

Comment [ger4]: Interagency 

reviewer said: “Can a citation for 

this be provided. In the TSD, it 

seems that EPA decided they were 

invalid for use? Was it EPA or 

NDEP?”

EPA response: Yes, we have 

provided a citation. NDEP 

initially reviewed the tests since 

they were performed for compliance 

with their program and found them 

invalid and we agreed with the NDEP 

determination and decided not to 

use the data in our data set. 
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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 shutdown 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 for achieving the MACT floor 
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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 

Comment [ger5]: 

Interagency reviewer said: 

Shouldn’t there be some discussion 

of how it was conducted?

EPA response: We added some text 

to briefly explain how the analysis 

was done. We also added a sentence 

below saying more information on 

these analyses is available in 

section V. There is also a 

sentence above that says “new 

information and analyses are 

discussed in more detail in Section 

V of this preamble and in the MACT 

Floor document which is available 

in the docket for this rulemaking”.
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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. 
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Table 1—MACT Floor Results for Ore Pretreatment Processes

Facility Average performance 

(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 existing 

sources)

158

99% UPL for new sources1 (i.e., the 

MACT Floor for new sources)

84

 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 

Comment [ger6]: Interagency 

reviewer said: “Please use 

facility name consistent with the 

TSD”

EPA: We have included the facility 

names and a cross walk to the 

“letters” in the TSD. However, we 

believe it is unnecessary and 

inappropriate to include facility 

names in the preamble. So, we are 

keeping it as letters in the 

preamble. The reader can refer to 

the TSD if they want to know the 

actual facilities...

Comment [ger7]: Interagency 

reviewer said: “Briefing slides we 

were provided said 127. Please 

confirm which value is correct.”

EPA response: 127 is the MACT 

standard when going beyond the 

floor, and is the final MACT 

standard for this affected source. 

158 is the MACT Floor, without 

going beyond the floor, not the

final MACT standard. 

Comment [ger8]: Interagency 

reviewer said: “Please clarify 

that new and existing refer to new 

sources and existing sources. 

Please also provide citation and 

link to TSD where calculations are 

provided.”

EPA: O.K. We have added “sources” 

after the word existing and new, 

and adding additional 

clarification. We also refer 

reader to the MACT floor document 

for more info.

Comment [ger9]: Interagency 

reviewer said: “So the 99% UPL is 

the same as the average? How is 

this possible.”

EPA response: No. It was just a 

coincidence that it came out that 

way. The “UPL” for new sources is 

based on the best performing 

source’s average emissions (in 

lb/million tons of ore) value 

(facility A) plus an amount to 

account for variability (i.e., the 

students t-factor multiplied by the 

square root of the total variance, 

which is equal to 2.42 * sqrt

(2.63e-10) = 39). The 39 is added 

to 45 = 84. With regard to the 

“average”, it was calculated by 

adding 45 + 56 + 71 + 165 and 

dividing by 4 = 84.
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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 removed from the data set emissions data 

based on previously uncontrolled sources that installed controls 

in 2009; for those sources, only the controlled emissions data 

were used. 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. 

Comment [ger10]: Interagency 

reviewer said: “Shouldn’t there be 

some discussion of how many 

facilities there were. Table 3 has 

9. RIA has 10”

EPA: Yes, we added text that 

describes how many facilities are 

in each final affected source. 

There are 10 facilities that have 

carbon processes with retorts. 

(Jerritt Canyon got left out of the 

preamble table). There are two 

facilities for which we have data 

for in the carbon processes without 

retorts. 
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For carbon processes, regardless of whether the facility 

operates a mercury retort, the MACT floor is based on control of 

mercury emissions using mercury condensers and carbon adsorbers. 

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 

Comment [cf11]: Interagency reviewer 

said: “Please provide footnote 

citation/link”

EPA response: Okay. We added a 

citation.
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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

Facility Average performance

(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 existing sources)

2.2

99% UPL for new sources (i.e., MACT 

Floor for new sources)

0.8

Table 3—MACT Floor Results for Carbon Processes without Mercury 

Retorts

Facility Average performance 

(lb/ton of concentrate)

M 0.058

F 0.098

Average of top 2 facilities 0.078

Comment [ger12]: Interagency 

reviewer said: “See previous 

comments regarding clarifying what 

this means.”

EPA response: okay, we have 

clarified this.

Comment [ger13]: Interagency 

reviewer: “Weren’t these the only 

two? This should be clarified/

discussed.”

EPA: we believe there are ~7-8 

facilities in the country that 

could fall in this source category, 

but we only have complete data for 

2 facilities. However, we believe 

these are the 2 best controlled of 

those 7-8 facilities. We have 

clarified the text to reflect this. 
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99% UPL for existing sources (i.e., 

MACT Floor for existing sources)

0.17

99% UPL new sources (i.e., MACT 

Floor for new sources)

0.14

 

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, the 

MACT floors for both existing and new sources are based on 

control of 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 costeffective option. There are approximately 3 facilities in the 

U.S. that use these types of processes. We have emissions tests 
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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

Facility Average performance 

(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 existing 

sources)

0.2

99% UPL for new sources (i.e., 

MACT Floor for new sources)

0.1

C. Compliance Dates

In the final rule, we provide in §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; and the consideration of installing new controls 

on the roaster preheaters, which also have not yet been 

Comment [ger14]: Interagency 

reviewer said: “Only two?”

EPA response: we believe there are 

3 or 4 facilities that fall into 

this source category, but these two 

are the only ones for which have 

data for. Edit to say “Average of 

2 facilities” 
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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 §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.
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In §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 §63.11646(a)(3) that compliance testing must be 
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performed with all affected emissions units in operation, if 

this is possible. This same requirement applies to the 

establishment of operating limits for all process units. 

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 §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 §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 
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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 §63.11645(e)(2) of the proposed 

rule, we have removed from the final rule the compliance 

requirement for that option that was in §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 
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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 

§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, 
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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 
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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 §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 
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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 §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 §63.11647(a)(1)(ii) of the final rule, we require these 
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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, §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 
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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 §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 §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 
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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 §63.11651 

to clarify that this term, as used in the final rule, includes 
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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 §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 cutoff) were not 

included in the section 112(c)(6) inventory that was the basis 

for the listing of gold mine ore production and processing

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
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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 
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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 112 (d)(2) or (d)(4). EPA reasonably 
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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. 
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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 production and processing. See 75 Fed. Reg. 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 Fed. Reg. 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 
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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. 
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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. Moreover, they did not identify any major 

flaws in EPA's estimation approach. 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, and the methodology EPA used to derive that 

estimate is detailed in docket item EPA-HQ-OAR-2010-0239-0175. 

No commenter has provided any other estimate or reasonable means 

of estimating the 1990 emissions. 

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 MACTlevel 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 
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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: We believe it is appropriate to promulgate MACT 

standards for mercury emissions for this industry. Based on our 

1990 baseline inventory for 112(c)(6) and other emission 

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 
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concerns about potential emissions from new gold mine

facilities. In summary, we believe it is necessary and 

appropriate to promulgate 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)
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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 D.C. Circuit in National Lime Ass’n v. 

EPA, 233 F.3d 625, 633-634 (D.C. Cir. 2000)). The part of the 
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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 
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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) 
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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 
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sources. Nor does National Lime address the issue, since the 

case dealt exclusively with major sources. 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. 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 
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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 
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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 
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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 states the 

following: “data indicate that the gold mining processing and 

production category consists of only area sources (i.e. 

facilities that emit less than 10 tons per year of any single 

HAP and less than 25 tons per year of any combination of HAP).” 

75 Fed. Reg. at 22479. The commenter did not support the area 

source determination for gold mines processing and production 

facilities. The commenter also claimed that the proposal 

indicates that actual emissions of hydrogen cyanide (HCN) at a 

few facilities are near the major source threshold. The 

commenter continued by saying that “by basing its evaluation of

whether gold mines are major sources on their actual emissions 

instead of their potential emissions, EPA violates both the 

Clean Air Act and its own regulations.” 

The commenter also stated that EPA’s failure to apply the 

same variability analysis in calculating gold mines’ potential 

to emit that was used in setting floors was internally 
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inconsistent, unexplained, and arbitrary and capricious. The 

commenter 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 and resulted in higher 

calculated HCN emissions than may actually be present. For 

instance, EPA did not apply what the commenters believe to be a 

key correction factor to account for the fact that much of the 

mass transfer of HCN for large surface areas is expected to be 

gas phase limited. Application of this correction factor would 

have reduced the estimates for HCN emissions from the mines 

tested by approximately 40-50%. The commenters also stated that 

Comment [ger15]: Interagency 

reviewer commented: “Is it clear 

that there were commenters that did 

not support an area source 

determination. We did not see this 

in the section”

EPA response: they are in the 

first part of this comment they 

didn’t think that gold mines were 

area sources because of the 

potential to emit. We added a 

sentence above to clarify this.
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fence line testing at selected gold mine operations demonstrated 

that there was no concern with fenceline levels of HCN 

emissions, and 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 
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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 Fed. Reg. 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 largestemitting 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), 

for the five largest gold mine facilities in our inventory, EPA 

conservatively estimated the source’s potential to emit HCN 

assuming that these sources would be operating every day of the 

year, 24 hours a day, at 100 percent of its current capacity. 

These conservative assumptions resulted in a potential to emit 

value of 5 tons per year of HCN 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 also eliminating the surface area 

correction factor, and those calculations resulted in a 

potential to emit value of 9 tons of HCN per year for the 

largest source. 

The commenters correctly point out that in determining 

whether a source is a “major source” under CAA section 112, we 
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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.
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In sum, EPA has developed very conservative estimates of 

the sources’ potential to emit HCN. At one end of the 

conservative range EPA estimates potential emissions of 5 tons 

of HCN per year, 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, 

which is also below the major source thresholds. 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 
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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, and to further examine the management practices at 

issue.

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 
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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.
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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. 
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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 
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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 
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State permit programs. According to the commenters, all nontitle 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 
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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, multinational, 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). 

Comment [ger16]: Interagency 

reviewer said: “It is not clear 

why EPA believes this. Can a more 

specific response to each of the 

concerns raised be presented.”

EPA response: we continue in the 

text below to explain our reasons

-Not a large amount of facilities 

affected

-Not financially burdensome

-Not burdensome to states

Comment [ger17]: Interagency 

comment: “Suggest instead citing 

specific data and what it shows to 

support EPAs belief”

EPA response: We changed the text 

some, and are adding a reference to 

the economic and small business 

analysis in the docket. This shows

that there are not any small 

businesses and how much revenue 

this industry makes and supports 

the position that it will not be 

financial burden.
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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.
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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 
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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 
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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 
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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 
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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 recreationtype prospectors; and gold mining operations that process less 
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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 production and 
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processing 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. We are also not making the exemption of 

facilities that process less than 1,000 tons per year of ore. 

As mentioned above, we already include in the final rule an 

exemption for very small scale operations. Further, we are 

concerned that the proposed 1,000 tons per year of ore cut-off 

may include sources beyond the very small scale operations. 

Therefore we believe this exemption is not necessary or 

appropriate.

C. MACT Floors
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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 
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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.3

 

3

 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. 

 A review of the run-by-run 
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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.

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, 
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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 
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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 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 
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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 based on representative and 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 
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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 
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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 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 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 

(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 
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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 from 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 
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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 
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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 
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proposed new source MACT standard for carbon processes and noncarbon 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. 
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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 these well-controlled facilities 

and used the information to conduct MACT floor analysis, as 
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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 it 

has been demonstrated as achievable in practice by facilities 

that installed mercury emission controls. 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 
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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° to 700°C, releasing 

gaseous elemental mercury, whereas autoclaves commonly reach 

temperatures of 175° to 230°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 
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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 
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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, it is not 

appropriate to 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 
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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 
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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-thefloor control for ore preheaters/dryers, as well as the beyondthe-floor control for autoclaves, in determining the MACT 

standard in this final rule for existing sources of ore pretreatment 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 
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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 
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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 megawatthours 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 
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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 
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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 
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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 D.C. 

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 
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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 reexamination of the emission controls and 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 mercury emissions from carbon processes at this facility are

about a factor of 10 less than the next “best” performer 

(Facility N) and a factor of 23 less than the average of the top 

5 performing facilities in the proposed rule. This level of 

emissions is due primarily to the very low levels of mercury in 

the ore rather than the control efficiency of its control 

devices. Facility M has good controls for mercury emissions
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from its carbon processes, but they are not as effective as the 

controls at Facility N. Facility N has state-of-the-art 

controls that achieve a more effective reduction of mercury 

emissions than Facility M. The difference is further manifested 

by the differences in the processing train for the carbon group 

in that mercury retorts are not needed or used at Facility M to 

recover mercury because the mercury levels are so low. 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 two 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 and those without mercury retorts, 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 
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and improve emission control as part of the NMCP. The new data 

indicate that 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. In light of the small 

emission reduction and the high cost effectiveness of this 

beyond-the-floor option, we 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. 
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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 newlyinstalled 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 new sources (based on the best 

performing facility, Facility N). In the beyond-the-floor 

analysis, we evaluated the impacts of adding a second carbon 

adsorber in series with the controls applied to achieve the MACT 

floor level of control. We estimate the capital cost would be 

$3 million with a total annualized cost of $1.3 million per 

year, an emission reduction of 9 lb/yr of mercury, and a cost 

effectiveness of $150,000/lb of mercury. Because of the small 

emission reduction and high cost effectiveness associated with 

this additional control, we decided not to go beyond the floor. 

Therefore, for existing sources of carbon processes with mercury 
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retorts, the MACT floor limit is the MACT standard for this 

affected source. We also considered possible beyond-the-floor 

options for new carbon processes with mercury retorts, but 

concluded these options were not cost-effective or feasible.

5. Compliance Alternative for New Carbon Process Sources

Comment: One commenter noted that the compliance 

“alternative” of 97 percent would be unlawful unless EPA 

specified that carbon sources had to meet the more stringent of 

either the floor standard or a 97 percent reduction standard. 

The commenter stated that because floors must reflect the 

emission level achieved by the best performing sources, allowing 

sources to meet a 97 percent reduction standard that was less 

stringent than the emission level actually achieved by the 

relevant best sources would contravene section 112(d)(3) and 

well-established D.C. Circuit court precedent.

One commenter supported EPA’s use of the percent control 

alternative to the new source MACT for the carbon group. The 

commenter believes that the percent control alternative for new 

source carbon group MACT should also be available as an 

alternative to the existing source MACT for the carbon group. 

Another commenter stated that another facility, which has 

an average mercury reduction efficiency level of 99.995 percent, 
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represents the “best controlled” similar source for the carbon 

process group and should be the basis for the alternative limits 

for new carbon processes.

Several commenters requested clarification of the way in 

which compliance with the alternative for percent reduction 

would be demonstrated for new sources when there are multiple 

control devices on an emission unit. 

Response: We eliminated in the final rule the compliance 

alternative of 97 percent reduction for new carbon processes. 

After reviewing the comments received on this 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 in stringency to the proposed new source limit of 

0.14 pounds of mercury per ton of concentrate. Largely due to 

the reasons stated above, we have eliminated the 97 percent 

control efficiency option for new carbon processes in the final 
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rule. In addition we are not allowing this percent reduction to 

be used for existing carbon sources as one commenter suggested. 

We also note that the facility that one commenter identified as 

having an average mercury reduction efficiency level of 99.995 

percent is now being used as the “best controlled” similar 

source for the final MACT standard for new carbon processes with 

mercury retorts.

D. Compliance Determinations

1. Timing for Compliance Determinations

Comment: Several commenters requested that the compliance 

deadline for existing sources be 3 years after the effective 

date of the rule, rather than the 2 years proposed. The 

commenters noted that several facilities will have to install 

control devices to achieve the MACT floor limits that have been 

proposed. The commenters explained that the controls must be 

custom designed for the unique characteristics of each process 

and associated process streams at each facility and stated that 

it can be time consuming and difficult to design, procure, 

construct, and implement emission controls to ensure effective 

operation for the particular source. 

Response: After reviewing the information provided in 

public comments on the challenges of retrofitting new controls, 
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and the fact that these controls have not yet been demonstrated 

on autoclaves and ore preheaters, we believe 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, we conclude that 2 years may not 

provide adequate time for existing sources to comply with the 

final emission standards.

Comment: Several commenters recommended that the rule 

specify that source testing results be used to determine 

compliance for the calendar year in which the test was conducted 

rather than to determine compliance for the prior 12 months. 

The commenters suggested that the source test results be applied 

to the hours of operation at the end of the calendar year to 

determine the source’s compliance with the MACT standard on an 

annual basis, as required in the NMCP. The commenters suggested 

that, if more than one source test is conducted in a year, the 

facility should average the mercury emission test results to 

determine compliance for the calendar year in which the tests 

were conducted. 

Another commenter commented that the annual compliance 
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testing should not be constrained to the same calendar quarter 

each year. The commenter stated that this can lead to testing 

during periods of operation that may not represent normal

production capacities. The commenter believes that mercury 

emissions testing should be scheduled for the most appropriate 

time interval throughout the calendar year. 

Response: The permitting authority needs to be able to 

determine compliance with the NESHAP as soon as possible after 

the tests are completed and test results are available. 

Consequently, the final rule requires that initial compliance be 

determined based on production data and operating hours for all 

full calendar months between the date the rule is published in 

the Federal Register and the date of the compliance test, and 

subsequently, annual compliance must be based on production data 

and operating hours for the 12 full calendar months preceding 

the compliance test. This allows the permitting authority to 

determine if the affected source is in compliance in a timely 

manner. (This is consistent with the way compliance 

determinations are made in another MACT rule that uses a similar 

format - National Emission Standards for Hazardous Air 

Pollutants for Primary Lead Smelting, 40 CFR part 63, subpart 

TTT.) If compliance was based on a calendar year, as suggested 
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by the commenter, then we would not know if a source is in 

compliance until after December each year. For example, if a 

source conducted its compliance test in March, we would have to 

wait about 9 more months before we could determine if that 

source was actually in compliance. After those 9 months, if the 

source was not in compliance, it would mean that the source 

could have been out of compliance for the previous 9 months. 

Moreover, we do not believe that compliance with the NESHAP 

based on the production data from the 12 months prior to the 

compliance test would cause problems with reporting under the 

State program. It is our understanding that the emissions 

limits in the Nevada State Phase 2 permits are (or will be) 

based on concentration in the stacks (e.g., micrograms per cubic 

meter (μg/m3

)). The limits in this final rule are based either 

on pounds of mercury per million tons of ore or pounds of 

mercury per tons of concentrate. Therefore, the companies can 

continue to report the annual emissions as required under the 

TRI program and the State program without conflict with this 

rule. 

If multiple compliance tests are conducted during the year, 

then a compliance determination must be made for each separate 

compliance test based on the production data and hours of 
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operation for the 12 full calendar months preceding each test 

(i.e., the results of multiple compliance tests conducted 

throughout the year are not averaged to provide a single 

compliance determination for the year).

We understand that the rule, as proposed, may have required 

all existing sources to conduct their subsequent annual 

compliance tests in the same calendar quarter, and this may pose 

a scheduling problem because of the large number of facilities 

located in the same State (e.g., Nevada). Our concern was that 

subsequent annual compliance tests, if not separated in time, 

could be conducted for two different years with little time 

between the two tests (e.g., only a few days apart for the 

extreme case where the first test is conducted in late December 

and the second one in early January of the following year). We 

are providing scheduling flexibility by requiring that annual 

compliance tests be at least 3 months apart and no more than 15 

months apart, and we are providing a similar separation for the 

period between the initial compliance test and the first annual 

compliance test. We do not believe that tracking multiple 

compliance dates is a particular problem for the permitting 

authority because that is the case for many other source 

categories subject to annual compliance testing.
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2. Test Methods

Comment: Several commenters supported EPA’s proposal of 

alternate Methods 30A and 30B for demonstrating compliance. One 

commenter supported EPA’s requirement to use Method 29 as an 

emission test method, but recommended two revisions: requiring 

a determination of the absence of cyclonic flow before sampling, 

and a minimum sampling time of 90 minutes for each test run. 

The commenter also stated that they do not support the use of 

the Ontario Hydro Method (ASTM D6784-02), Method 30A, or Method 

30B as mercury test methods. The commenter believes that the 

methods of demonstrating compliance with the emissions standards 

should be consistent with the methods utilized to establish the 

emission standards, which were based mainly on Method 29 data. 

The commenter said that the typical gas streams associated with 

the gold mining industry have high particulate loadings, high 

mercury concentrations, sulfur dioxide (SO2), and contain 

particulate-bound mercury. The commenter also stated that the 

alternative methods were not developed specifically for the gold 

mining industry and their typical gas streams and concluded that 

the results from the various alternative methods will yield 

varying results, will not be comparable, and will provide 

inconsistent reporting of overall mercury emissions.
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Response: Method 29 references Method 1, which requires 

cyclonic flow checks under certain circumstances. Consequently, 

in the final rule, we have removed the specific requirements for 

cyclonic flow checks prior to every stack test that were in 

§63.11646(a)(1)(vi) of the proposed rule. Owners or operators 

should follow the requirements in the applicable EPA reference 

method and any additional requirements specified by the 

permitting authority. 

When specifying the minimum requirements for compliance 

tests, it is more important to specify a minimum sampling volume 

than a minimum sampling time because the detection of a 

regulated pollutant is a function of the volume of the sample 

rather than the length of time taken to collect the sample. 

Thus, the final rule does not specify a minimum sampling time. 

We are also changing the required minimum sampling volume to be 

30 dscf rather than the 60 dscf as proposed in §63.11646(a)(2)

because we believe that 30 dscf generally will be adequate for 

detecting mercury emissions for this industry. Affected 

facilities should be aware, however, that the minimum sample 

volume may sometimes result in a failure to detect any mercury 

(a non-detect) emitted from a process unit subject to the 

emission standard (for the group of process units within the 
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affected source) because of a mercury concentration at the 

outlet lower than expected. If the emission testing results for 

any of the emission points yield a non-detect value, then the 

minimum detection limit (MDL) must be used in calculating the 

emissions for that emission point and, in turn, for calculating 

the sum of the mass emissions for all emission points subject to 

the emission standard for determining compliance. If the 

resulting mercury emissions (in pounds of mercury per ton of 

concentrate, or pounds of mercury per million tons of ore) for 

the affected source are greater than the MACT emission standard, 

the owner or operator may use procedures that produce lower MDL 

results and repeat the mercury emissions testing one additional 

time for any emission point for which the measured result was 

below the MDL. If this additional testing is performed, the 

results from that testing must be used to determine compliance 

(i.e., there are no additional opportunities allowed to lower 

the MDL).

After reviewing the information provided by the commenter 

about Method 29, we agree with the commenter that Method 29 is 

the most appropriate method for compliance determinations for 

this source category because of the unique characteristics of 

these sources. Therefore, we are promulgating Method 29 as the 
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main method for compliance in this rule. Alternative methods, 

such as 30B and the Ontario Hydro method (OHM; ASTM D6784-02),

could be used to demonstrate compliance for this source category 

if approved by the permitting authority. These alternative 

methods (such as 30B and OHM) may prove to be more appropriate 

under certain circumstances. However, we have omitted Method 

30A as an option in the final rule, as it is not yet in general 

use. 

E. Monitoring

1. Compliance Assurance

Comment: One commenter noted that EPA’s proposed mercury 

standards are expressed in a format of pounds of mercury per 

million tons of ore processed and observed that the proposed 

rule requires stack testing only once a year. The commenter 

claims that EPA’s proposed monitoring requirements would not 

demonstrate whether sources are in compliance with their 

emission standards, which renders the rule unenforceable. 

According to the commenter, the once-a-year stack test would 

provide no indication as to what a mine’s emissions were the 

rest of the year. The commenter said that a source that failed 

its stack test would have only one violation of emission 

standards, even if that test showed that the source likely 
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violated its emission standard throughout the year. The 

commenter believes that EPA’s proposed monitoring requirements 

would not assure compliance with the proposed emission 

standards. The commenter also noted that EPA proposed to 

require sources to monitor their mercury emissions either with 

CEMs, sampling, or various types of parametric monitoring; 

however, these methods do not provide direct information about 

the pounds of mercury emitted. Consequently, none of these 

monitoring methods could be used to demonstrate whether a source 

is in or out of compliance with the proposed emission standards. 

According to another commenter, all three affected source 

categories should be required to use CEMS at all times and at 

all emission points. The commenter stated that the ore 

pretreatment group especially needs CEMS because of variable 

levels of mercury in the ore and different operational measures 

within the control of the facility.

Other commenters supported a requirement for continuous 

monitoring and said that the CEMS should be incorporated into 

the compliance regime as well. The commenters believe that, if 

the monitoring results indicate that the mine is consistently 

out of compliance for a period of one week without correction, 

the process unit should be subject to compliance-based penalties 
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and/or shut down until corrections are made and the process unit 

is back in compliance. According to the commenters, quarterly 

stack testing should still be required to demonstrate that the 

CEMS is working.

Response: We recognize the importance of requiring 

adequate monitoring to assure compliance with the emission 

standards. Because of the higher mercury emitting potential of 

the roaster, we proposed the option of mercury monitoring using 

CEMS or weekly monitoring with PS 12B with associated parametric 

monitoring as well. We are including in the final rule the 

option to perform continuous PS 12B monitoring, and, as with the 

CEMS, associated parametric monitoring would not be required. 

We are changing the frequency of the proposed weekly 

concentration monitoring approach for roasters to twice per 

month (at least 11 days apart) and would allow a facility to 

conduct a Method 30B test (as an alternative to a PS 12B test), 

supplemented with continuous parametric monitoring. We changed 

the frequency because we believe that sampling twice per month, 

coupled with continuous parametric monitoring, is sufficient for 

determining that the roaster control devices are operating 

properly. We added the alternative of using Method 30B because 

this method directly measures mercury concentration and is a 
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valid means of determining whether the concentration is below 

the operating limit established during the initial performance 

test. The twice per month Method 30B measurements will provide 

a concentration value that can be compared to that operating 

limit to determine if an exceedance of the operating limit has 

occurred. Also, if the twice monthly sampling shows repeated 

deviations over time, EPA could decide at a later date that CEMs 

or continuous monitoring with PS 12B are appropriate and 

necessary for roasters. 

We disagree with the commenter that the proposed monitoring 

requirements render the rule unenforceable. Although the 

mercury concentrations monitoring for roasters along with the 

parametric monitoring of all control devices on all units do not 

directly measure pounds of mercury per ton of input, we believe 

that these actions, along with the annual emissions compliance 

tests, is still an acceptable approach to assure compliance with 

the emission standards all year long. Parametric monitoring of 

control devices assures that the control devices are operating 

properly (and reducing emissions) on an ongoing basis. Any 

exceedance of the parameter limits or operating limits triggers 

corrective action. If corrective action does not return the 

mercury concentration within the established limits, the plant 
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must conduct a full compliance test and determine if the source 

is meeting the mass-based (lb/million tons of ore) emission 

standard.

We do not believe that we should include CEMS as a 

monitoring option for the non-roaster sources. These sources 

have less potential mercury emissions, and requiring CEMS on all 

these other units would be quite costly and burdensome. 

Moreover, most of these other units are, or will be, controlled 

with carbon adsorbers, and the carbon adsorber monitoring

required by the final rule is an effective means of ensuring the 

controls are working effectively on a continuing basis. We 

consider that either frequent testing of carbon beds to monitor 

for breakthrough using Method 30B, or frequent adsorbent 

sampling for mercury content, is an effective way to ensure 

these mercury control systems are operating properly on a 

continuing basis. The final rule also requires parametric 

monitoring of wet scrubbers that are considered the final 

mercury control (i.e., not followed by a carbon adsorber or 

calomel mercury scrubber). We believe that annual tests coupled 

with appropriate parametric monitoring of the wet scrubbers are 

sufficient to ensure emissions are properly controlled on a 

continuing basis. 
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With regard to the comment that quarterly stack testing 

should be required for facilities using a CEMS, we believe that 

following the Quality Assurance (QA) procedures detailed in 40 

CFR 60, Appendix F, are sufficient to ensure the CEMS continues 

to operate as designed, and in this case, additional stack 

sampling is not necessary.

2. Operating Limits

Comment: One commenter stated that the operating limits 

for roasters and for carbon adsorbers are inappropriate and set 

up a second set of MACT standards. The commenter claimed that 

the operating limits do not take into account the effects of: 

hours of operation of a process unit on mercury emissions; 

reduction in performance of a process unit offset by an 

improvement in performance of another process unit; variability 

in the exhaust gas flow rates with no appreciable effect on the 

corresponding mercury emission rate; and variability in the 

inlet mercury concentrations to a carbon adsorber. These 

factors all result in variability in the outlet mercury 

concentration. The commenter also noted that the proposed 

operating limit for carbon adsorbers could result in premature 

carbon change out, resulting in the generation of more waste. 

The commenter recommended that EPA defer to the Nevada state 
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monitoring requirements and only provide for monitoring of 

throughput and annual mercury emission testing to demonstrate 

compliance with the MACT emission standard. The commenter 

believes that any operating limit parameters must be established 

based on manufacturer specifications and recommendations in 

coordination with the permitting authority and not based on 

values measured during source compliance testing.

Response: We proposed the mercury operating limits as a 

monitoring tool to ensure that the processes within individual 

affected sources and their associated control devices are 

functioning properly on a continuing basis and not as a second 

set of MACT standards. We developed emission standards for four

affected sources, and the emission standard for an affected 

source applies to the sum of emissions from all process units 

within the affected source. One unit could have an upward 

fluctuation in mercury concentration, but the group of process 

units could still meet the MACT limit. We see the value of the 

operating limit approach as sufficient to detect significant 

increases in emissions and as a valuable tool to ensure the 

control devices are operating effectively and provide quick 

notification of a potential problem with controls or emissions. 

The monitoring parameters are used as compliance indicators, and 
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the relevant mercury operating limits are the main “triggers” of 

a possible emissions increase and are set to alert facility 

operators when emissions are greater than the corresponding

mercury operating limit. We believe it is important to have 

such monitoring in the rule to ensure the control devices are 

working properly.

Regarding specific comments about monitoring the carbon 

adsorber, the State of Nevada has had good results with 

conducting sampling of the carbon adsorber to maintain its 

performance. The final rule offers an additional option of 

measuring the mercury concentration exiting the carbon adsorber 

that also achieves the same objective of avoiding breakthrough 

of the bed. We do not expect sudden dramatic failures of this 

technology. Instead, we expect to obtain close control of 

performance by ensuring that the carbon is changed in a way that 

prevents breakthrough. This monitoring methodology should also 

prevent premature replacement of the bed.

We disagree with the comments that only monitoring for 

throughput and annual emissions testing are sufficient to 

demonstrate compliance with the MACT standards. Such an 

approach does not yield sufficient data to assure compliance 

with the emission standards either directly or indirectly by 
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assuring that the control devices are operating properly. The 

parametric monitoring and operating limits specified in this 

final rule provide assurance that control devices are properly

operated and maintained between emissions tests, and exceedances 

of the operating limit require corrective action. With regard 

to the comment that any operating limit parameters should be 

based solely on manufacturer specifications and/or in 

consultation with the permitting authority, we have provided 

various options in this rule for establishing control device 

parameter limits. Control device operating parameter values 

sometimes are site-specific and are associated with a level of 

emissions from the source. Therefore, it is generally 

preferable for certain control device parameter limits to be 

associated with an emissions test that demonstrates compliance 

with the emissions standards. However, we agree that certain 

parameters for mercury scrubbers applied to roasters, such as 

the ranges associated with ensuring the proper chemistry of the 

scrubber, are best provided by the system’s manufacturer. 

Guarantees of performance are usually conditioned by requiring 

that the system be operated as designed and specified by the 

manufacturer, and there is no assurance that a potentially 

narrow range that would be established during a short 
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performance test reflects the full applicable range of proper 

operation. We also realize that it may be preferable that the 

permit authority establish the parameter limits for some of the 

control devices in this industry because of some of the unique 

characteristics of the processes and control devices used in 

this industry and the experience of the permit authority with 

addressing these sources. Therefore, this final rule allows 

three options for establishing parameter limits: (1) based on 

the initial compliance test; (2) according to the manufacturer’s 

specifications; or (3) based on limits established by the 

permitting authority

Comment: Some commenters stated that their established 

parametric monitoring programs are sufficient to confirm that 

mercury emission controls are functioning properly for roasters. 

The commenters also stated that the NMCP permits have required 

parametric limits and that additional CEMS for mercury would 

neither improve the operation of these current controls, nor 

reduce mercury emissions. The commenters concluded that the 

operating parameters monitored on a regular basis are key 

parameters for measuring the efficiency and operation of the 

mercury controls and that operating each of these units within 

the optimum ranges ensures that mercury emissions are being 
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effectively controlled. 

Response: As discussed above, we do not believe parametric 

monitoring alone is sufficient for roasters because of the very 

high mercury emission potential, unless the facility has 

adequately demonstrated that the mercury emissions from the 

roasters are consistently very low (e.g., less than 10 pounds 

per million tons). We have concluded that the combined approach 

of annual stack compliance testing along with the mercury 

concentration monitoring and parametric monitoring requirements 

and options outlined in this rule are necessary to detect excess

emissions and to ensure controls are working effectively on a 

continuous basis. We note that for facilities that choose to 

monitor the mercury concentration from the roaster with CEMS or 

continuous PS 12B sampling, they do not have to do parametric 

monitoring. For facilities that can demonstrate their mercury 

emissions are less than 10 lbs per million tons of ore, they 

only have to do parametric monitoring, no mercury concentration 

monitoring.

3. Mercury Concentration Monitoring for Roasters

Comment: One commenter stated that the proposed provisions

for monitoring mercury concentrations in roaster emissions are 

not based on roaster process and pollution control device 

Comment [ger18]: Interagency 

Review: “This sort of implies that 

you do finalize an approach which 

has parametric monitoring alone. Is 

this correct or are we confused?”

EPA response: 

Yes. One approach allowed

parametric monitoring alone. If a 

facility has very low mercury 

emissions (emits less than 10 

pounds per million tons) they only 

need to perform parametric 

monitoring of their roaster and 

annual emissions tests. We revised 

the text to clarify.
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operational parameters and would not yield reliable information 

that can be used for detecting and correcting problems. The 

commenter also stated that the formula for establishing the 

mercury operation limit for roasters is not appropriate because 

it uses an emission limit that is based on emission test data 

from several process units in addition to the roaster. The 

commenter recommended using the methods proposed for parametric 

monitoring of roaster emission control devices for all roasters. 

The commenter also has concerns about utilizing PS 12A (mercury 

CEMS) and PS 12B for emissions monitoring purposes because there 

are terms and conditions listed in the proposed rule that are 

not fully defined. The commenter also recommended deleting the 

emissions monitoring requirements for mercury concentration for 

carbon adsorbers for the same reasons described above for 

roasters.

Response: We disagree with the comment that monitoring the 

mercury concentration in roaster emissions would not yield 

reliable information that can be used for detecting and 

correcting problems. An elevated mercury concentration in the

roaster stack gas indicates that there could be a problem with 

either the process or the control device, which could result in

excess mercury emissions from that unit. Monitoring the mercury 
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concentration in roaster emissions provides a direct measure of

the regulated pollutant (mercury). The commenter is correct 

that the formula for establishing the mercury operating limit 

for roasters is based on emission tests performed on several 

processes units in addition to the roaster. However, for the 

facilities with roasters that will be subject to the 

requirements to monitor mercury concentration, the roaster is 

the biggest source of potential mercury emissions within the 

affected source. Therefore, we conclude that changes in the 

mercury concentration in the roaster exhaust gases provide a

reasonable indication of overall emissions from the affected 

source. In addition, the operating limit is not used directly 

to determine compliance with the MACT emission standard. As 

mentioned above, it is designed to detect elevated mercury 

concentrations in the roaster stack gas, which could indicate a 

problem with either the process or the control device. We 

continue to believe that it is necessary and appropriate to 

monitor mercury concentration for the largest source of 

potential mercury emissions in the source category (i.e., the 

roaster) to detect excursions in emissions that must be 

addressed when the operating limit is exceeded. By developing 

the mercury operating limit from the emission standard and 
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compliance test results, an exceedance of the mercury operating 

limit will indicate a potential increase in emissions and that 

corrective actions are needed. 

As described above, we believe that either continuous 

mercury sampling or mercury sampling twice per month (coupled 

with continuous parametric monitoring of the control device)

should be required for the roaster emissions. If a CEMS is 

used, the daily average mercury concentration is calculated by 

averaging the hourly emissions concentrations during that day. 

The final rule includes continuous sampling with PS 12B as an 

option for monitoring roasters. If PS 12B is used for 

continuous integrated sampling (i.e., without parametric 

monitoring), the daily average concentration is determined by 

assigning the mercury concentration measured by the sorbent trap 

monitoring system (total mass of mercury collected during the 

sampling period divided by the sample volume) as the daily 

average value to each of the days covered by the integrated 

sample.

 A third option is based on short-term sampling twice per 

month (at least 11 days apart) for mercury concentration using 

either PS 12B or Method 30B, and if this option is chosen, 

continuous parametric monitoring of the mercury scrubber must 
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also be performed. For this short-term sampling option (twice 

per month sampling) each measured mercury concentration must be 

compared to the operating limit to determine if an exceedance 

has occurred. For the contents of the monitoring plan, see 40 

FR 63.8(d)(3) and 40 CFR 60, Appendix F.

We also disagree that parametric monitoring alone is 

sufficient for carbon adsorbers. For carbon adsorbers, 

measuring the mercury concentration exiting the carbon bed is 

also a direct measure of the pollutant of interest. (The other 

option as established for years in NDEP operating permits 

involves sampling the carbon for mercury content.) An elevated 

mercury concentration indicates that there could be a problem 

with either the process or the control device, which could 

result in excess mercury emissions from that unit. We have 

established exit concentration monitoring requirements in many 

rules for emissions of organic compounds exiting carbon 

adsorbers. That monitoring has proven to be effective to 

prevent or detect breakthrough, and the same principles apply 

here for mercury. 

Comment: Commenters stated that CEMS for gold mining 

operations are not capable of accurately measuring mercury 

emissions and that there are three major challenges with the 
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feasibility of mercury CEMS for the gold mining industry: 

mercury CEMS calibration, sample transport, and system 

operability and reliability. The commenters are concerned with 

the unavailability of a means to calibrate the CEMS for roasters 

because existing calibrator designs are simply not capable of 

generating mercury concentrations high enough to provide 

meaningful upscale calibration points that correspond to gold 

mining source characteristics. The commenters noted the 

unavailability of National Institute of Standards and Technology 

(NIST) traceable calibration gases and stated that the current 

calibration standards traceable to NIST do not apply to the full 

range of mercury concentrations that can be present in the 

exhaust gases of roasters. The commenters concluded that the 

lack of a NIST-traceable standard is a fatal flaw that precludes 

using mercury CEMS to monitor roaster emissions. Regarding 

sample transport, the commenters said that current designs of 

mercury CEMS for coal-fired electric generating units require 

high temperature umbilical lines to transport the sample from 

the stack to the analyzer and that CEMS on coal-fired electric 

generating units have seen umbilical failures occur, 

representing another challenge to having CEMS function 

consistently for the continuous monitoring of mercury from 
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industrial sources. The commenters were also concerned with the 

CEMS operability and reliability because mercury CEMS must 

contain some type of converter to reduce oxidized mercury to 

elemental mercury and premature catalytic failures periodically 

occur in these units resulting in several days of missing data. 

The commenters continued by stating that users reported mercury 

CEMS to be unavailable as much as 30 to 40 percent of the 

electric generating unit operating time. The commenters believe 

the amount of downtime to be expected from these systems on 

roasters would likely be even higher. The commenter concluded 

that the breakdown events, combined with the other types of 

failures, result in data availability that is substantially 

inferior to parametric monitoring and cannot justify the 

significant cost and resource investment necessary to install, 

operate, and maintain these devices.

The commenters are concerned that continuous data reports 

of mercury emissions that are not accurate, reliable, or 

credible could be offered as “credible evidence” to assert a 

violation. The commenter concluded by stating that this concern 

was particularly troubling in Nevada, where there are separate 

mercury limits established pursuant to State law.

Response: Regarding the feasibility of using CEMS to 
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monitor mercury emissions from roasters, CEMS have been 

demonstrated for process units similar to roasters (e.g., coalfired power plants), and we believe there is no technical reason 

why they will not work for the roasters. (See NESCAUM, 2010. 

Technologies for Control and Measurement of Mercury Emissions 

from Coal-Fired Power Plants in the United States: A 2010 Status 

Report Northeast States for Coordinated Air Use Management 

(NESCAUM) July 2010).

Many of the issues with mercury CEMS have been resolved as 

facilities have gained experience with their use. However, we 

realize that mercury concentrations in the exhaust gases from 

roasters can be higher than the range of concentrations for 

coal-fired power plants, and that the calibration standards 

traceable to NIST, that have been available in the past, have 

not applied to the full range of mercury concentrations that can 

be present in the exhaust gases from roasters. Nevertheless, as 

we discussed in the proposal preamble, CEMS manufacturers supply 

calibration standards for the ranges of concentrations seen at 

roasters.

In addition, the NIST has recently completed certification 

of a ‘NIST Prime’ elemental mercury gas generator at 

concentrations of 41, 68, 85, 105, 140, 185, 230, 287, and 353

Comment [ger19]: Interagency 

reviewer: “Can a specific citation 

be provided linking to the 

successful use of CEMS monitoring 

for Hg in the US?”

EPA: Yes. We added a citation 

(NESCAUM, 2010). 

Comment [ger20]: Interagnecy 

reviewer: “Are these sufficiently 

similar to roasters in the range of 

hg emissions? It seems the NIST

calibration standards are only 

applicable within a small range. 

Are roasters and coal fired power 

plants in the same range?”

EPA: mercury concentrations in the 

exhaust gases from roasters can be 

higher than the range of 

concentrations for coal-fired power 

plants. The current calibration 

standards traceable to NIST do not 

apply to the full range of mercury 

concentrations that can be present 

in the exhaust gases from roasters. 

However, calibration standards are 

available from the manufacturers of 

mercury CEMS which can be used to 

calibrate these CEMS for monitoring 

of roasters. We added text to 

clarify this.
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μg/m3. Mercury gas generator vendors may now submit elemental 

mercury gas generators for certification to serve as ‘Vendor 

Primes’ in a wide range of concentrations. Therefore NIST 

traceable mercury gas standards can now be made available in 

concentrations that cover the full range of the concentrations 

typically measured from roasters.

After consideration of public comments, we continue to 

believe CEMS are a valuable tool and a reasonable option for

monitoring mercury concentrations and comparing those 

concentrations to the operating limit that is established by 

CEMS measurements made during the compliance test. However, 

we also point out that the final rule does not require the use 

of CEMS; instead, the final rule includes CEMS as one of the 

three monitoring options. The other two options that we are 

promulgating for monitoring mercury from roasters are: (1)

continuous monitoring using PS 12B; and (2) twice per month 

sampling using PS 12B or Method 30B coupled with parametric 

monitoring. All three of these monitoring options are intended

to ensure that emissions from the roasters are not exceeding

operating limits, or if they do exceed the operating limits, 

that corrective actions are taken in a timely manner to bring 

the emissions down to within the operating limits. If these 
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corrective actions are not successful then the facility must 

perform a complete compliance test using the methods in section 

63.11646 to determine whether the affected source is in 

compliance with the MACT standard. The CEMs can also be used to 

help identify problems with control systems and ensure that 

corrective actions are taken immediately to fix such problems. 

The exceedance of the operating limit is not intended to 

determine if the source in violation of the MACT standard. 

Rather, it would be the subsequent compliance test pursuant to 

section 63.11646 that would be used to determine if the source 

is in compliance with the MACT standard.

We understand the commenter’s concerns regarding the 

transport of samples and converter failures. However, we have 

revised the final rule to give facilities 3 years to comply with 

the rule which will allow extra time to successfully set-up and 

operate controls and monitoring equipment to be able to comply 

with the MACT standards. We believe this will provide 

sufficient time, for facilities that choose the CEMs monitoring 

option, to identify and resolve issues with the transport of 

samples and converters.

Comment: One commenter stated that the regulated industry 

has no experience with direct measurements of mercury 
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concentrations at the roaster exhaust gas stream. As a result, 

the commenter believes that there will be problems in collecting 

data, establishing appropriate timeframes for sampling under PS 

12B, maintaining instrument reliability for CEMS, and in 

establishing confidence in the accuracy of the results reported 

by these methods. The commenter claimed that the calculated 

operating limit based on source testing and simultaneous direct 

measurements may not be reflective of the future daily 

operations of all the stack emissions. The commenter noted that 

flow rate measurements are critical in verifying compliance with 

actual emission limits because sometimes lower flow rates of the 

stack exhaust gas flow can artificially elevate the mercury 

concentration in the gas stream with no real effect on 

emissions. The commenter concluded that any exceedance in 

mercury concentration should be verified first with a compliance 

test before halting the roaster production.

Response: We have learned from the comments received that

there may be a learning curve for facilities to implement the 

concentration monitoring procedures. As described in section 

V.D. of this preamble, we have established in the final rule a 

compliance date that is 3 years after the effective date of the 

final rule for existing sources, partly to allow sources time to 
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ensure they can successfully comply with the monitoring

requirements, but mainly to allow time to install new mercury 

emission controls that we believe will be necessary to meet the 

emission standards in the final rule.

We agree that mercury concentration measurements are not

direct measurements of the emissions rate from the affected 

source and that flow rate, production, and other factors need to 

be considered. These are some of the reasons that the operating 

limit is not being used as a direct measure of compliance with 

the MACT standards. However, concentration measurements above 

the operating limit should indicate that either controls are not 

working effectively or other problems are occurring. In either 

case, exceedances of the operating limit require investigation 

and may require corrective actions. The requirement to shut 

down the roaster has been removed from this final rule. However 

an exceedance of the mercury concentration does trigger 

corrective action, and if not corrected requires a compliance 

test.

Comment: One commenter requested that EPA reduce the 

weekly Method 12B monitoring frequency to quarterly or at most 

monthly. The commenter also requested that EPA include a 

provision that allows for a source to demonstrate a correlation 

Comment [ger21]: Interagency 

Reviewer said: 

“Is there something in the comments 

that leads EPA to believe 3 yrs 

will be sufficient? If so, it would 

be helpful to cite. It is unclear 

based on the comments that more 

time will resolve the concerns 

raised.”

EPA response: 3 years is the max 

that the General Provisions will 

allow. We had proposed 2 years. 

Industry asked for the 3 years. We 

believe 3 years is appropriate to 

give sufficient time to add 

controls, etc...

§ 63.6 Compliance with standards and 

maintenance requirements.

(c) Compliance dates for existing sources. (1) 

After the effective date of a relevant standard 

established under this part pursuant to section 

112(d) or 112(h) of the Act, the owner or 

operator of an existing source shall comply with 

such standard by the compliance date 

established by the Administrator in the 

applicable subpart(s) of this part. Except as 

otherwise provided for in section 112 of the Act, 

in no case will the compliance date established 

for an existing source in an applicable subpart 

of this part exceed 3 years after the effective 

date of such standard.
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or consistency of performance such that the Method 12B sampling 

frequency can be further reduced based on the permitting 

authority’s acceptance of the demonstration. The commenter 

suggested that if multiple Method 12B samples are collected in a 

single day or over multiple days in the calendar week, then the 

samples should be averaged, and this average concentration 

should be compared to the operating limit. The commenter said 

that, for stacks with high mercury concentration, the sample 

collection time may be only an hour or two, and in this case, it 

may be important to collect more than one sample in a single day 

or over multiple days to obtain a representative mercury 

concentration measurement.

Response: After taking into consideration the commenter’s 

rationale, under this monitoring option, the final rule requires

the sampling of mercury concentration at least twice per month 

(with 2 samples taken at least 11 days apart) instead of weekly 

sampling as proposed. If multiple samples are taken during the 

twice per month period, each result must be compared to the 

operating limit separately (i.e., not averaged). Otherwise, a 

high result from a sample taken near the end of the sampling

period might not trigger corrective actions to correct a problem 

that developed at that time if the results are averaged with 

Comment [ger22]: Interagency 

reviewer commented: “Is this 

change responsive to all the 

commenters concerns mentioned 

above? What is EPAs response 

regarding collection time?”

EPA: this is mainly a response to 

comment that requested that EPA 

reduce the weekly Method 12B 

monitoring frequency to quarterly 

or at most monthly” We are 

compromising to twice per month. 

With regard to collection time, we 

believe this issue has been 

adequately addressed. Moreover, we 

decided that they cannot average 

multiple tests, each test much be 

compared to operating limit.
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previous samples during periods of good performance. We do not 

agree with the suggestion to allow the monitoring frequency to 

be reduced if the monitoring results demonstrate consistency 

over the long term. We believe that monitoring the mercury 

concentration at least twice per month is necessary for roasters 

to ensure that potential problems with control systems are 

identified quickly and corrective actions are taken in a timely 

manner.

4. Parametric Monitoring of Control Device for Roasters

Comment: Some commenters recommended that EPA remove the 

provisions requiring monitoring of the mercury scrubber liquor 

flow rate and scrubber pressure drop because each facility that 

has a roaster has a unique sequence of air pollution control 

devices, and monitoring parameters that may be appropriate for 

one roaster may not be applicable to another. One of the 

commenters said that the scrubber liquor flow rate is not 

currently monitored, nor is it considered a critical parameter 

in the daily operation of the scrubber mercury removal tower 

associated with roasters at their facility. The commenter 

further explained that the scrubber is not a spray tower, but 

instead the liquor is recirculated in the tower, so the pump is 

monitored to insure it is operational. The commenter stated 
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that the pressure drop across the mercury removal tower at its 

roasters is monitored, but is not considered a critical 

parameter and that the mercuric ion and chloride ion 

concentrations that they monitor are the critical parameters 

that define the effectiveness of the mercury scrubber. 

Another commenter added that, for the calomel-based mercury 

scrubbers, the key parameter is the reagent concentration in the 

solution exiting the scrubber and that maintaining the exit 

reagent concentration ensures there is sufficient reagent to 

react with the mercury vapor. The commenter noted that low exit 

concentrations indicate that either the liquor flow rate is too 

low, or the fresh reagent addition rate is too low. Thus, 

liquor flow rate does not need to be monitored in addition to 

reagent exit concentration. The commenter stated that if EPA 

continues to require them, the ranges should be based on the 

manufacturer’s specification or an alternative value approved by 

the permitting authority, as opposed to the three test runs from 

the initial compliance test. One commenter recommended that the 

corresponding range or limit for parametric deviations be 

applied to a daily average value rather than continuous 

instantaneous values or single samples. 

Another commenter also stated that the requirement to 
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establish the minimum water flow rate and pressure drop of the 

wet scrubber on readings taken during the performance test 

should not apply to scrubbers on roasters. The commenter noted 

that these parameters were intended to monitor for physical 

processes, and the scrubbers on roasters often include chemical 

reactions, which are not monitored. 

Response: We agree that pressure drop is not relevant to 

mercury scrubbers because, unlike venturi scrubbers applied to 

control PM emissions, it is not related to its mercury emission 

control performance. We have removed pressure drop monitoring 

from the final rule for mercury scrubbers. However, we continue 

to believe that it is important to monitor the scrubber flow 

rate to ensure the scrubber solution is being delivered to the 

system and that the flow is adequate, which is related to the 

system’s performance. We understand that some facilities 

monitor mercury scrubber solution line pressure (solution header 

pressure) as an indicator of flow rate, and we agree this is 

adequate to ensure proper flow. Consequently, the final rule 

requires hourly monitoring of scrubber flow rate (or line 

pressure) for mercury scrubbers on roasters. As with the inlet 

temperature operating range, the minimum flow rate or line 

pressure must be established by one of the following three ways: 
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(1) during the initial compliance test, (2) from the 

manufacturer’s specifications, or (3) based on the 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. The final rule requires hourly monitoring and 

that corrective action is triggered if the flow rate or line 

pressure falls below the established parameter limit.

Regarding the acceptability of scrubber flow rate and inlet 

gas temperature parameter values that were approved by 

permitting authorities prior to this final rule, such values 

must be established as specified in the final rule and are not 

presumed in advance to be acceptable. Note that the monitoring 

requirements for wet scrubbers in §63.11647 of the final rule 

would not apply to the mercury scrubbers on roasters, or any wet

scrubber prior to the mercury scrubber on the roasters.

Comment [ger23]: Interagency 

Reviewer: “It is unclear which 

parameter values are being referred 

to.”

EPA: we have clarified the 

parameter values for roasters i.e. 

scrubber flow rate and inlet gas 

temperature.
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Comment: One commenter believes that establishing a 

maximum operating temperature for inlet gas concentrations by 

artificially increasing this temperature during compliance 

testing may destroy the control equipment, conflict with 

recommended operating temperatures, and artificially increase 

the reported mercury emissions. The commenter concluded that 

these parameters are not deemed critical in the effective 

operation of a mercury calomel scrubber. Another commenter 

added that their Compliance Assurance Monitoring (CAM) plan 

provides for an inlet gas temperature range of 32° to 134°F to 

prevent water freezing problems or extremely hot gas 

temperatures that could damage the mercury scrubber. The 

commenter stated that mercury scrubbers remove mercury from the 

gas stream through a chemical reaction and not a condensation 

mechanism and that lower temperatures will not remove (via 

condensation) additional mercury. The commenter explained that,

although mercury scrubber inlet gas temperature is not a 

relevant control performance parameter, their facility maintains 

the inlet gas temperature below 134°F and monitors the 

temperature daily to prevent damage to the controls system from 

excessively low or high gas temperatures.

Response: After additional review of operating permits and 

Comment [ger24]: Interagency 

Reviewer: “Many separate and 

distinct comments are presented 

above over 2.5 pages and thus it 

was a bit hard to tell if EPA was 

responsive to all the concerns 

listed. It may improve readability 

if perhaps provides a response 

after each substantive comment, 

instead of one response for the 

entire section.”

EPA: As suggested, we split the 

previous large Section #4 into two 

separate sections, which include 

this section and the section 

immediately above this section. We 

believe this makes it clearer and 

is sufficient now.
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consideration of public comments, we have found that the inlet 

temperature of the mercury scrubber is monitored and maintained 

within a range to provide operational flexibility with the lower 

end bounded to prevent freezing and the upper end bounded to 

prevent damage to equipment, which in turn could lead to excess 

emissions. In addition, we have learned that this temperature 

is dependent on the cooling tower water temperature used in the 

process, and this water temperature can vary quite widely from 

winter to summer. Facilities may not be able to address the 

issues described above if they can only use initial compliance 

testing to establish the inlet temperature operating range, as 

we proposed. Consequently, the final rule provides the 

following three ways for a facility with a roaster to establish 

an operating range for inlet temperature: (1) based on the 

maximum inlet temperature during the initial compliance test;

(2) from the manufacturer’s specifications; or (3) based on the 

limits established by the permitting authority. If the facility 

chooses the option to establish the limits during initial 

compliance, the final rule requires 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. The facility 
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must monitor the temperature hourly, and any exceedance of the 

upper limit for temperature would trigger corrective action. 

5. Exceeding the Operating Limits for Roasters

Comment: One commenter was concerned about the 

consequences of exceeding a parametric monitoring limit. The 

commenter remarked that shutting down the roaster for exceeding 

a monitoring parameter without evidence of an ongoing emission 

limit exceedance is arbitrary and capricious, unnecessarily 

punitive, and threatens the economic viability of the regulated 

sources. The commenter pointed out that the ranges of 

parameters measured during source testing are not necessarily 

the only ranges within which the unit can operate effectively. 

The parameters proposed by EPA are not the best parameters for 

monitoring roaster emissions and do not directly correlate to 

mercury emissions or proper control system operation. The 

commenter also objected to the period of only 45 minutes to 

investigate and take corrective action. 

One commenter recommended that the corrective action 

response time be extended minimally to 48 hours after daily 

average values are processed, plus an additional 24 hours to 

verify the daily average parametric value was within limits. For 

facilities that conduct PS 12B sampling and a daily average 

Comment [ger25]: Interagency 

comment: “We did not see where EPA 

responded to this comment.”

EPA: we have clarified this in the 

text. The main points are: 

-we are allowing them the option to 

set operation ranges from 

manufacturer’s specifications or 

range approved by permitting 

authority.

-we are still requiring them to 

monitor scrubber flow rate and 

inlet gas temperature, but removing 

pressure drop. 

-We revised the time period for 

corrective action to at least 48 

hours. 
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parametric deviation persists for 96 hours, the commenter 

recommended requiring sampling of the roaster’s exhaust using PS 

12B within the next 24 hours, then evaluating the mercury 

concentration results. If the mercury concentration is below 

the operating limit, then, within 10 days of receiving the 

analytical results, the facility should be required to either 

petition the permitting authority for a change in the parametric 

limits, or provide the permitting authority with a compliance 

plan that details corrective actions taken to date and the plan 

and schedule for bringing the parameter back within range. The 

commenter said that, if the mercury concentration is above the 

operating limit, the facility will be required to schedule an 

independent source testing firm to perform a compliance test 

within 45 days using one of the approved methods described in 

the rule. The commenter noted that the Nevada State agency 

requires 30 days to review the testing protocol, and source 

testing companies typically require 30 days or more advanced 

notice. 

For roasters where direct concentration measurements are 

not required and a daily average parametric deviation persists 

for 96 hours, the commenter recommended that within 48 hours, 

the facility should: (1) provide the permitting authority with 
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a compliance plan that details corrective actions taken to date 

and the plan and schedule for bringing the parameter back within

the limits; or (2) schedule an independent source testing firm 

to perform a compliance test within 45 days using one of the 

approved methods described in the rule. The commenter concluded 

that, if the test results show that the source has exceeded the 

threshold of 10 lb/million tons of ore, the facility would be 

required to implement direct mercury concentration measurements.

One commenter requested that EPA provide an exception from 

the shutdown requirement when it can be demonstrated that, 

notwithstanding an exceedance of the parametric operating range, 

the roaster mercury emissions are less than the operating limit 

for mercury concentration. The commenter stated that the 

mercury concentration measurement is a more direct indication of 

the ultimate mercury emissions that the parametric monitors are 

designed to address. 

Response: We have investigated in greater detail the 

issues associated with monitoring roasters, and we have 

consulted with NDEP and the owners and operators of roasters to 

learn more about appropriate roaster monitoring. We understand 

that sometimes the ranges of parameters measured during source 

testing are not necessarily the only ranges within which the 
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unit can operate effectively, that is why in the final rule we 

are offering two other options for establishing the ranges: (1) 

based on manufacturer’s specifications; and (2) ranges approved 

by the permitting authority. We believe that monitoring the 

scrubber flow rate, inlet gas temperature, and scrubber liquid 

chemistry, as required in the final rule, are appropriate 

parameters to monitor. We have also revised the requirements of 

this final rule to provide assurance that timely corrective 

actions are taken when a monitoring parameter is exceeded, and 

we have included requirements for testing for mercury 

concentrations to determine if the corrective actions were 

successful or if a deviation has occurred. The final rule 

includes parametric monitoring of the mercury scrubbers applied 

to roasters to control mercury. If a parameter is outside of 

the established range or limit, corrective actions are 

triggered. If corrective actions do not result in the parameter 

reading being corrected and verified within 48 hours, a mercury 

concentration measurement (using CEMs, Method 30B, 29, OHM, or 

PS 12B) 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). If the 
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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 operating limit is exceeded, the exceedance must 

be reported as a deviation and the facility must conduct a full 

compliance test within 40 days to determine if the source is in 

compliance with the MACT limit. See §63.11647(d) of final rule.

Comment: For facilities that monitor roasters with a CEMS, 

one commenter proposed that corrective action be required within 

48 hours of receiving and processing the results from the CEMS 

data, plus an additional 24 hours should be allowed to collect 

verification data to see if the daily average concentration was 

restored below the operating limit. The commenter recommended 

that, if the exceedance persists, the facility should be 

required to schedule an independent source testing firm to 

perform a compliance test within 45 days.

For facilities that choose PS 12B monitoring, the commenter 

recommended that a deviation be considered an exceedance of the 

operating limit if the average of three consecutive sampling 
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results (three weeks) were above the established limit. The 

commenter proposed that the facility should then have one week 

to take corrective actions, an additional week to take the 

verification sample using PS 12B, with receipt of results the 

following week (three weeks total). The commenter stated that 

if the exceedance persists, the facility should be required to 

schedule an independent source testing firm to perform a 

compliance test within 45 days using one of the approved methods 

described in the proposed rule.

Response: After considering these comments on the mercury 

concentration operating limit and the above discussion on 

parametric monitoring of roasters, we have made several 

clarifications in the final rule. If a mercury concentration 

operating limit is exceeded from either daily average 

measurements from a CEMS, continuous sampling using PS 12B, or 

from sampling twice per month (at least 11 days apart) using PS

12B or Method 30B, the exceedance must be reported to the permit 

authority as a deviation and corrective actions must be 

implemented within 48 hours upon receipt of the sampling results 

that show the deviation. Moreover, within 96 hours of the 

exceedance, the owner or operator must measure the concentration 

again (with the CEMS, PS 12B, Method 30B, Method 29, or OHM) and 

Comment [ger26]: Interagency 

Reviewer: “It is unclear to this 

reader why 96 hrs was chosen.”

EPA: We provide 48 hours from the

time of exceedance to get parameter 

back in range. If they can’t get 

it back in range within the next 48 

hours they have to conduct a PS12B 

or Method 30B test within 48 hrs to 

demonstrate that the operating 

limit has not been exceeded. So 

total of 96 hours from exceedance. 

We believe this is the appropriate 

time to allow for these actions. 

The test results need to be 

finalized as fast as reasonably 

possible to ensure the emissions 

are being controlled. We estimate 

that 96 hours total (48 + 48) is 

sufficient time to accomplish this. 
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demonstrate to the permit authority that the operating limit for 

mercury concentration has been met, or inform the permit 

authority that the limit continues to be exceeded. If the 

operating limit is still exceeded after these 96 hours, the 

owner or operator must conduct a full compliance test for the 

ore pretreatment affected source within 40 days to determine if 

the affected source is in compliance with the MACT emission 

standard. If the source is determined to be in compliance, the 

compliance test may also be used to establish a new operating 

limit for mercury concentration. See §63.11647(a)(1)(ii), 

(a)(2)(ii), and (a)(3)(ii) of the final rule.

Comment: One commenter requested that EPA provide an 

exception to the shutdown requirement for facilities that have 

well-controlled roasters and elect to monitor under the proposed 

Option 3. The commenter believes a facility should have time (45 

days) to demonstrate that the roaster’s mercury emissions remain 

less than 10 lbs of mercury per million tons of ore. The 

commenter stated that this would be achieved by scheduling an 

independent source testing firm to perform a compliance test 

using methods described in the rule, and calculations that 

demonstrate compliance with the limit of 10 lbs per million tons 

of ore. 

Comment [ger27]: Interagency 

reviewer: “We did not see where 

this comment was responded to.”

EPA: we removed the shut down 

requirement and revised the time

period for demonstrating compliance 

with operating limits. We have 

clarified this in the text.
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Response: As we have discussed above, the final rule relies in 

part on parametric monitoring of mercury scrubbers used on

roasters to assure compliance with the applicable emission 

standards, and when the measured parametric values are out of 

the established operating range, corrective actions must be 

taken. This is no different for facilities that qualify for the 

exemption described in §63.11647(a)(5) of the final rule (i.e., 

facilities exempt from mercury concentration monitoring by 

having demonstrated that their roaster emissions are less than 

10 lb/million tons of ore). For these facilities, the final 

rule similarly requires that corrective actions be taken to 

restore the scrubber operating parameters to the established 

operating range. If the parameters are not restored to the 

established range within 48 hours of triggering the corrective 

actions, the owner or operator must perform mercury 

concentration sampling of the roaster emissions using PS 12B,

Method 30B, Method 29, CEMS or OHM and determine the mercury 

concentration within 48 hours following the initial 48 hours (or 

a total of 96 hours from the time the parameter range was 

exceeded). The measured concentration must be compared to a 

mercury concentration operating limit that is based on Equation 

2 in the final rule, where the value for “Ctrap” in Equation 2 is 
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based on the mercury concentration for the roaster measured 

during the most recent compliance test. 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 the operating limit is 

exceeded, the facility must take corrective actions and report 

it to the permit authority as a deviation. The owner or 

operator must also conduct a compliance test within 40 days to 

determine if the roaster operations are in compliance with the 

emission standard. See §63.11647(d) of the final rule. We also 

note that the requirement to shut down the roaster has been 

removed from this final rule.

6. Carbon Adsorber Temperature Monitoring

Comment: Several commenters stated their concern with the 

proposed requirement of monitoring gas stream temperature at the 

inlet to the carbon adsorber and maintaining the inlet 

temperature below the maximum temperature established during the 

compliance test. They noted that the primary purpose for 

monitoring the inlet gas stream temperature of carbon adsorbers 
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is to prevent spontaneous combustion of the sulfidized carbon in 

the adsorber, not to detect excursions in mercury emissions. 

The commenters also stated that some carbon adsorption systems 

heat the gas stream prior to the carbon adsorber to prevent 

moisture buildup and/or subsequent condensation in the carbon. 

The commenters explained that the NMCP already requires that the 

exit gas temperature of condensers prior to the carbon adsorbers 

be established to minimize mercury emissions from the condenser. 

The commenters believe that an increase in inlet gas temperature 

to a carbon adsorption unit is not indicative of an increase in 

inlet gas stream mercury emissions because the high operating 

temperatures of the processes volatilize approximately 100 

percent of mercury. The commenters stated that establishing a 

maximum operating temperature for inlet gas concentrations by 

artificially increasing this temperature during compliance 

testing may destroy mercury control equipment; conflict with 

NMCP requirements and/or manufacturer’s recommended operating 

temperatures; artificially increase the reported mercury 

emissions; or artificially decrease the allowable operating 

limit for mercury concentration.

The commenters continued by stating that, if EPA persisted 

in requiring the monitoring of the gas stream inlet temperature, 
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the maximum inlet temperature limit should be established by 

either the manufacturer’s recommendation and/or concurrence with 

the permitting authority. The commenters proposed monitoring 

the inlet temperature once per shift as an option to 

continuously monitoring the inlet temperature and comparing the 

daily averages rather than the hourly averages to the operating 

limit. The commenters noted that many facilities do not have 

digital acquisition systems capable of recording continuous 

data, and monitoring once per shift is sufficient to maintain 

control performance. The commenters suggested that, if 

corrective action is needed, the facility should be allowed to 

sample the carbon loading to demonstrate that the effectiveness 

of the carbon adsorber has not been adversely impacted. 

Response: The purpose of monitoring the inlet temperature 

to carbon adsorbers is not to provide an indication of higher 

mercury concentrations in the inlet stream as suggested by the 

commenters. The purpose is related to the fact that temperature 

is a fundamental parameter that affects the efficiency and 

capacity of carbon adsorbers. Generally, higher temperatures

result in lower capacity and earlier breakthrough and, in fact, 

high temperatures are used to desorb adsorbed pollutants to 

regenerate carbon. In the extreme of temperature, the carbon 
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adsorber might actually be desorbing rather than acting as a 

control device. This is particularly important for those carbon 

adsorbers applied to high temperature thermal processes, such as 

carbon kilns and melt furnaces, where it is possible for the 

exhaust temperature to rise above the normal operating 

temperature or above the temperature at which the carbon 

adsorber was designed to operate. For high temperature 

processes (such as furnaces), and not those such as 

electrowinning where the temperature may be near ambient 

conditions, we continue to require monitoring the inlet 

temperature. Owners or operators must establish an operating

limit for temperature based on one of the following: (1) the 

maximum temperature during the initial compliance test; (2) from 

the manufacturer’s specifications; or (3) based on limits 

established by the permitting authority. If this established 

operating limit is exceeded corrective action must be taken and 

the exceedance reported as a deviation to the permit authority. 

Further, the final rule requires facilities to monitor inlet 

temperature once per shift rather than continuously, as was 

proposed. Because inlet temperatures should not vary greatly 

over the course of an 8 to 12-hour period, we believe monitoring 

once per shift is adequate. We also conclude that if a 
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temperature exceedance has occurred, the carbon bed should be 

sampled or the outlet concentration determined, depending on the 

monitoring option chosen, within 48 hours to ensure no permanent 

damage to the carbon adsorber occurred as a result of the 

deviation. We believe the temperature exceedance should be 

reported as a deviation even if the subsequent monitoring shows 

that the carbon bed is operating properly because the subsequent 

monitoring would not necessarily detect if mercury had been 

desorbed and excess emissions occurred.

7. Monitoring of Wet Scrubbers 

Comment: One commenter proposed that only the scrubber 

water flow rate monitoring be required for wet scrubbers on the 

quenching circuits associated with the roaster. The commenter 

wanted to confirm that wet scrubber monitoring does not apply to 

wet scrubbers or condensers on roasters. Another commenter 

asked that EPA confirm that the term “wet scrubbers” does not 

include condensers, which are used throughout the mining 

processes for gas cooling to condense water or (in the case of 

retorts) mercury. Another commenter asked EPA to confirm that 

wet scrubber monitoring does not apply to wet scrubbers 

associated with ore preheaters.

One commenter noted that continuous readings on wet 
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scrubbers are unreliable and proposed monitoring the water flow 

rate and pressure drop once per shift. The commenter noted that 

if any water flow rate or pressure drop reading exceeds the 

operating limit, the facility should follow the procedures for 

operating limit exceedances. The commenter stated that many 

facilities do not have data acquisition systems capable of 

recording continuous data and that wet scrubbers are primarily 

used to control particulates. The commenter concluded by 

stating that wet scrubbers are not key mercury controls and 

monitoring once per shift is sufficient to maintain control 

performance on a continuing basis. 

One commenter wanted to confirm that the limits established 

during testing would not be more stringent than the requirements 

set forth in the Standards of Performance for New Stationary 

Sources for Metallic Mineral Processing Plants, which allows for 

plus or minus 30 percent. Another commenter recommended that 

the operating limit for wet scrubber monitoring be based on 

either the lowest average value during any test run or no lower 

than 10 percent below the average value measured during the 

test.

Response: We are clarifying in the final rule that 

§63.11647(h) applies only to wet scrubbers not followed by a 
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mercury control system (i.e., carbon adsorber, calomel mercury 

scrubber, etc.). It is necessary to monitor the primary mercury 

emission control device, which is the last stage of the exhaust 

gas cleaning treatment train, to ensure it is operating properly 

and controlling mercury emissions, and the rule does not require 

that wet scrubbers in the gas treatment train (typically used 

for control of PM and/or SO2) prior to the primary mercury 

emission control device be monitored under this rule for mercury 

emissions. However, if there is no carbon adsorber or mercury 

scrubber, and the wet scrubber in question is the only control 

device for mercury emissions, the final rule requires that it be 

monitored once per shift per operating day (e.g., minimum of two 

times per day) for pressure drop and flow rate with operating 

limits that are either established during the initial compliance 

test, from the manufacturer’s specifications, or based on 

approval from the permitting authority (except for pressure drop 

for autoclaves as discussed above). This applies to wet 

scrubbers on ore preheaters and quenching if there is no carbon 

adsorber or mercury scrubber in the exhaust gas treatment train.

As discussed above, the scrubber monitoring for roasters applies 

to the mercury scrubber (located at or near the end of the 

exhaust gas treatment train) and does not apply to the wet
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scrubbers that are used to remove PM and SO2 prior to the mercury 

scrubber. 

We are clarifying in the final rule that condensers, such 

as those found at roasters and mercury retorts, are not wet 

scrubbers. We agree that monitoring and recording the pressure 

drop once per shift is adequate for monitoring these wet 

scrubbers to ensure they are operating properly. We disagree 

that a buffer of +/- 30 percent based on a certain New Source 

Performance Standard (NSPS) subpart is appropriate for this 

NESHAP for mercury. The comment suggesting an option of a +/-10 

percent buffer around the average value during the performance 

test has merit as an option to only using the lowest value 

during any individual run as the operating limit. If the system 

is so stable that it shows very minimal variability during the 

performance test, we agree that it is appropriate to add +/-10 

percent to account for potential future variability. 

Consequently, we are incorporating this option in the final 

rule, as suggested by the commenter. However, we are using +/-

10 percent rather than +/- 30 percent. We are also clarifying 

for the final rule for wet scrubbers on an autoclave, that 

facilities must establish the pressure drop range according to 

manufacturer’s specifications. 
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8. Monitoring of Multiple Units Ducted to One Stack

Comment: Commenters requested clarification that, for 

facilities that have two roasters ducted together through a 

shared mercury control system, the mercury concentration 

monitoring would be conducted on the combined exhaust stream. 

The commenters also requested clarification that the mercury 

concentration operating limit for two roasters that share a 

control system would be established during the simultaneous 

operation of the roasters in order to account for the combined 

mercury emissions from both roasters. 

Commenters also requested clarification that, for 

facilities with multiple process units ducted together through a 

shared carbon adsorber, the mercury concentration monitoring

would be conducted on the combined exhaust stream. The 

commenters also requested clarification that the mercury 

concentration operating limit for a carbon adsorber for multiple 

units that share the carbon adsorber would be established during 

the simultaneous operations of all process units in order to 

account for the combined mercury emissions. 

Response: We agree with the commenters in general and have 

made the following clarifications in the final rule. If two 

roasters share a common control device and stack, the mercury 
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concentration operating limit, as well as stack testing for 

compliance will be based on both roasters operating if possible. 

However, monitoring for mercury concentration must be performed 

at the frequency specified in the final rule whether only one or 

both roasters are operating. We also have clarified that, for 

multiple process units vented to a common carbon adsorber, the 

mercury concentration operating limit and the stack testing for 

compliance must be based on all units operating if possible. 

However, the ongoing mercury concentration monitoring must be 

performed at the frequency specified in the final rule for 

whatever units are operating at the time.

9. Monitoring Mercury Concentration in Roaster Ore

Comment: One commenter objected to the proposed 

requirement to conduct additional compliance testing if the 

mercury concentration in the ore fed to the roaster is higher 

than any concentration measured in the previous 12 months. The 

commenter stated that there would not be an increase in the 

mercury emissions from their roasters because of the extensive 

series of mercury controls, some of which operate more 

efficiently at higher mercury loadings with unchanged stack 

emissions. In addition, the commenter noted that the rule does

not provide details on how to measure the mercury ore 
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concentration or what threshold of significance would be used to 

show an increase in ore mercury content occurred. The commenter 

concluded that the requirement would only provide extra cost and 

burden without any environmental benefit.

Response: We agree with the commenter and have removed 

this requirement (§63.11647(a)(4)(iii) of proposed rule) from 

the final rule. We have no data showing 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, roasters condense and recover 

elemental mercury prior to the mercury scrubber, and any 

increase in mercury loading would likely result in an increase 

in the recovery of liquid elemental mercury. We have identified 

and require the monitoring of parameters associated with the 

scrubber chemistry, and maintaining these parameters within the

established range for which the mercury scrubber was designed. 

This monitoring approach helps ensure that the mercury scrubbers 

are controlling mercury emission independent of variations in 

ore mercury content.

VI. Summary of Environmental, Economic and Health Benefits 
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For proposal, we estimated baseline mercury emissions to be 

3,119 lb/yr based on the available emissions data and average 

process data for the period 2007 to 2009. To estimate the 

impacts of the final rule, we have revised our baseline mercury 

emissions estimate to account for the recent installation of new 

mercury emission controls at two facilities and additional test 

data received since proposal. As a result of these changes, we 

now estimate baseline mercury emissions to be 2,636 lb/yr. We 

estimate the final MACT standard will reduce mercury emissions 

from gold mine ore processing and production by 1,461 lb/yr from 

the baseline emissions levels of 2,636 lb/yr down to a level of 

1,176 lb/yr once this NESHAP is fully implemented. The annual 

emissions expected after the MACT standards are implemented 

(1,176 lb/yr) represent an estimated 77 percent reduction from 

2007 emissions (5,000 lb/yr), a 95 percent reduction from the 

emissions level in 2001 (about 23,000 lb/yr), and more than 97 

percent reduction from uncontrolled emissions levels (more than 

37,000 lb/yr). The capital cost of emission controls is 

estimated as $36 million with a total annualized cost of $8 

million per year. The capital costs for monitoring, reporting, 

and recordkeeping are estimated as $0.5 to $1.0 million with a 

total annualized cost of $0.7 to $1.5 million per year, 
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depending on the monitoring option that is chosen. The overall 

cost effectiveness is estimated to be about $6,300 per pound of 

mercury reduced. The cost of compliance is estimated to be less 

than 0.8 percent of sales for all affected firms. We therefore 

believe that the economic impact on an affected company would be 

insignificant. Electricity consumption is expected to increase 

by about 12,600 megawatt-hours per year due to increased fan 

capacity for carbon adsorbers and the installation of 

refrigeration units or condensers on a few process units. Nonhazardous solid waste (spent carbon containing mercury that must 

be regenerated or disposed of) would increase by about 7 tons 

per year.

VII. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

This action is a “significant regulatory action” under the 

terms of Executive Order 12866 (58 FR 51735, October 4, 1993)

because it may raise novel legal or policy issues. Accordingly, 

EPA submitted this action to the Office of Management and Budget 

(OMB) for review under Executive Order 12866, and any changes 

made in response to OMB recommendations have been documented in 

the docket for this action. 

B. Paperwork Reduction Act
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The information collection requirements in this final rule 

have been submitted for approval to OMB under the Paperwork 

Reduction Act, 44 U.S.C. 3501 et seq. The Information 

Collection Request (ICR) document prepared by EPA has been 

assigned EPA ICR No. 2383.01.

The recordkeeping and reporting requirements in this final 

rule are based, in large part, on the information collection 

requirements in EPA’s NESHAP General Provisions (40 CFR part 63, 

subpart A). The recordkeeping and reporting requirements in the 

General Provisions are specifically authorized by section 114 of 

the CAA (42 U.S.C. 7414). All information other than emissions 

data submitted to EPA pursuant to the information collection 

requirements for which a claim of confidentiality is made is 

safeguarded according to CAA section 114(c) and EPA’s 

implementing regulations at 40 CFR part 2, subpart B.

This final NESHAP will require applicable one-time 

notifications according to the NESHAP General Provisions. In 

addition, owners or operators must submit annual notifications 

of compliance status and report any deviations in each 

semiannual reporting period. Records of all performance tests,

measurements of feed input rates, monitoring data, and 

corrective actions will be required.
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The average annual burden for this information collection 

averaged over the first 3 years of this ICR is estimated to 

total 483 labor hours per year at a cost of approximately 

$26,847 per year for the 21 facilities that will be subject to 

this final rule, or approximately 23 hours per year per 

facility. Capital costs are estimated as $1.0 million, 

operation and maintenance costs are estimated as $52,000 per 

year, and total annualized cost (including capital recovery) is 

estimated as $360,210 per year for this final rule’s information 

collection requirements. No costs or burden hours are estimated 

for new sources because none is projected for the next 3 years. 

Burden is defined at 5 CFR 1320.3(b).

An agency may not conduct or sponsor, and a person is not 

required to respond to, a collection of information unless the 

collection displays a currently valid OMB control number. The 

OMB control numbers for EPA’s regulations in 40 CFR part 63 are 

listed in 40 CFR part 9. In addition, EPA is amending the table 

in 40 CFR part 9 of currently approved OMB control numbers for 

various regulations to list the regulatory citations for the 

information requirements contained in this final rule.

C. Regulatory Flexibility Act

The Regulatory Flexibility Act generally requires an agency 
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to prepare a regulatory flexibility analysis of any rule subject 

to notice and comment rulemaking requirements under the 

Administrative Procedure Act or any other statute unless the 

agency certifies that this rule would not have a significant 

economic impact on a substantial number of small entities. 

Small entities include small businesses, small not-for-profit 

enterprises, and small governmental jurisdictions. 

For the purposes of assessing the impacts of this final 

NESHAP on small entities, a small entity is defined as: (1) a 

small business whose parent company meets the Small Business 

Administration size standards for small businesses found at 13 

CFR 121.201 (less than 500 employees for gold mine ore 

processing and production facilities – NAICS 212221); (2) a 

small governmental jurisdiction that is a government of a city, 

county, town, school district, or special district with a 

population of less than 50,000; and (3) a small organization 

that is any not-for-profit enterprise that is independently 

owned and operated and is not dominant in its field.

After considering the economic impacts of this final rule 

on small entities, I certify that this action will not have a 

significant economic impact on a substantial number of small 

entities. This final rule is estimated to impact about 21 gold 
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mine ore processing and production facilities, none of which are 

owned by small entities. Thus, there are no impacts to small 

entities from this final rule. Although this final rule will 

contain requirements for new sources, EPA expects few, if any,

new sources to be constructed in the next several years. 

Therefore, EPA did not estimate the impacts for new affected 

sources for this final rule. 

Although this final rule will not have a significant 

economic impact on a substantial number of small entities, EPA 

nonetheless has tried to reduce the impact of this final rule on 

small and large entities. These standards establish emission 

limits that reflect practices and controls that are used

throughout the industry and in many cases are already required 

by State operating permits. These standards also require only 

the essential monitoring, recordkeeping, and reporting needed to 

verify compliance. These final standards were developed based 

on information obtained from industry representatives in our 

surveys, consultation with business representatives and their 

trade association and other stakeholders. 

D. Unfunded Mandates Reform Act

This final rule does not contain a federal mandate that may 

result in expenditures of $100 million or more for state, local, 
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and tribal governments, in the aggregate, or to the private 

sector in any one year. This final rule is not expected to 

impact state, local, or tribal governments. The total 

nationwide annualized cost of this final rule for affected 

industrial sources is $9.1 million/yr. Thus, this final rule is 

not subject to the requirements of sections 202 and 205 of the 

Unfunded Mandates Reform Act (UMRA).

This final rule is also not subject to the requirements of 

section 203 of UMRA because it contains no regulatory 

requirements that might significantly or uniquely affect small 

governments. This final rule will not apply to such governments 

and will not impose any obligations upon them.

E. Executive Order 13132: 

This action does not have federalism implications. It will 

not have substantial direct effects on the States, on the 

relationship between the national government and the States, or 

on the distribution of power and responsibilities among the 

various levels of government, as specified in Executive Order 

13132. This final rule does not impose any requirements on 

state and local governments. Thus, Executive Order 13132 does 

not apply to this action. 

Federalism

In the spirit of Executive Order 13132, and consistent with 
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EPA policy to promote communications between EPA and State and 

local governments, EPA specifically solicited comment on this 

proposed action from State and local officials.

F. Executive Order 13175: Consultation and Coordination with 

Indian Tribal Governments

This action does not have tribal implications, as specified 

in Executive Order 13175 (65 FR 67249, November 9, 2000). This 

final rule imposes no requirements on tribal governments; thus, 

Executive Order 13175 does not apply to this action. Although 

EPA requested comment from tribal officials in developing this 

action, no comments on the proposal were received from tribal 

governments. However, the reductions in mercury emissions to 

the environment, which will be achieved by this final rule, will 

certainly benefit tribal populations within the vicinity of 

affected gold mine ore processing and production facilities. 

G. Executive Order 13045: Protection of Children from 

Environmental Health and Safety Risks

EPA interprets Executive Order 13045 (62 F.R. 19885, April 

22, 1997) as applying only to those regulatory actions that are 

based on health or safety risks, such that the analysis required 

under section 5-501 of the Executive Order has the potential to 

influence the regulation. This action is not subject to 
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Executive Order 13045 because it is based solely on technology 

performance. However, we note that the final rule will result 

in significant reductions in emissions of mercury, and thus will 

provide benefits to children's health.

H. Executive Order 13211: Actions Concerning Regulations That 

Significantly Affect Energy Supply, Distribution, or Use

This action is not a “significant energy action” as defined 

in Executive Order 13211 (66 FR 28355, May 22, 2001) because it 

is not likely to have a significant adverse effect on the 

supply, distribution, or use of energy. We have concluded that 

this final rule will not likely have any significant adverse 

energy effects because energy consumption would increase by only 

12,600 megawatt-hours per year.

I. National Technology Transfer and Advancement Act

Section 12(d) of the National Technology Transfer and 

Advancement Act of 1995 (“NTTAA”), Public Law No. 104-113 (15 

U.S.C. 272 note), directs EPA to use voluntary consensus 

standards (VCS) in its regulatory activities unless to do so 

would be inconsistent with applicable law or otherwise 

impractical. VCS are technical standards (e.g., materials 

specifications, test methods, sampling procedures, business 

practices) that are developed or adopted by voluntary consensus 
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standards bodies. NTTAA directs EPA to provide Congress, 

through OMB, explanations when the Agency decides not to use 

available and applicable VCS. 

This final rulemaking involves technical standards. EPA 

decided to use ASME PTC 19.10-1981, “Flue and Exhaust Gas 

Analyses,” for its manual methods of measuring the oxygen or 

carbon dioxide content of the exhaust gas. These parts of ASME 

PTC 19.10-1981 are acceptable alternatives to EPA Method 3B. 

This standard is available from the American Society of 

Mechanical Engineers (ASME), Three Park Avenue, New York, NY 

10016–5990.

Another VCS, ASTM D6784-02, “Standard Test Method for 

Elemental, Oxidized, Particle-Bound and Total Mercury in Flue 

Gas Generated from Coal-Fired Stationary Sources (Ontario Hydro 

Method)” is an acceptable alternative to EPA Method 29 for this 

NESHAP if approved by the permit authority. This performance 

test method is available from ASTM International. See 

http://www.astm.org/.

EPA has also decided to use EPA Methods 1, 1A, 2, 2A, 2C, 

2D, 2F, 2G, 3, 3A, 3B, 4, 12A, 12B, 29, 30B, Method 7471A, 

“Mercury in Solid or Semisolid Waste (Manual Cold-Vapor 

Technique),” and ASTM D6784–02, “Standard Test Method for
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Elemental, Oxidized, Particle-Bound and Total Mercury in Flue 

Gas Generated from Coal-Fired Stationary Sources,” (incorporated 

by reference – see 63.14). Although the Agency has identified 

14 VCS as being potentially applicable to these methods cited in 

this rule, we have decided not to use these standards in this 

final rulemaking. The use of these VCS would have been 

impractical because they do not meet the objectives of the 

standards cited in this rule. The search and review results are 

in the docket for this final rule.

Under section 63.7(f) and section 63.8(f) of Subpart A of 

the General Provisions, a source may apply to EPA for permission 

to use alternative test methods or alternative monitoring 

requirements in place of any required testing methods, 

performance specifications, or procedures in the final rule.

J. Executive Order 12898: Federal Actions to Address 

Environmental Justice in Minority Populations and Low-Income 

Populations

Executive Order 12898 (59 FR 7629, February 16, 1994) 

establishes federal executive policy on environmental justice. 

Its main provision directs federal agencies, to the greatest 

extent practicable and permitted by law, to make environmental 

justice part of their mission by identifying and addressing, as 
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appropriate, disproportionately high and adverse human health or 

environmental effects of their programs, policies, and 

activities on minority populations and low-income populations in 

the United States.

EPA has determined that this final rule will not have 

disproportionately high and adverse human health or 

environmental effects on minority or low-income populations 

because it will increase the level of environmental protection 

for all affected populations without having any 

disproportionately high and adverse human health or 

environmental effects on any population, including any minority 

or low-income population. 

Additionally, the Agency has reviewed this rule to 

determine if there were any existing disproportionately high and 

adverse human health or environmental effects on minority or 

low-income populations that could be mitigated by this 

rulemaking. An analysis of demographic data showed that the 

areas in closest proximity to gold mines are very rural, with

low total populations. The population total for block groups 

which centers are within 3 miles of a gold mine facility is 

1,580. At the three mile radius, minority populations and 

children’s populations are underrepresented when compared to 
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national averages, while populations living below poverty are 

overrepresented. The aggregate average percentages for these 

groups are 26.3 percent, 30.5 percent, and 26 percent for 

minority populations, populations living below poverty, and 

children’s populations, respectively. These averages are 

compared to national averages across block groups for these 

populations are 31.8 percent, 12.5 percent, and 25.7 percent. . 

There were only two block groups with centers within 3 miles of 

any gold mine, and the total population living below poverty was 

found to be 492. 

In determining the aggregate demographic makeup of the 

communities near affected sources, EPA used census data at the 

block group level to identify demographics of the populations 

considered to be living near affected sources, such that they 

have notable exposures to current emissions from these sources. 

In this approach, EPA reviewed the distributions of different 

socio-demographic groups in the locations of the expected 

emission reductions from this rule. The review identified those 

census block groups within a circular distance of a 1, 3, and 5 

miles of affected sources and determined the demographic and 

socio-economic composition (e.g. race, income, education, etc.) 

of these census block groups. The radius of 3 miles (or 
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approximately 5 kilometers) has been used in other demographic 

analyses focused on areas around potential sources.4,5,6,7 Gold 

mine facilities were assumed to have an average area of 7 square 

miles and buffered distances were calculated beyond the 7 square 

mile area to count populations not within the mine boundaries. 

EPA’s demographic analysis has shown that these areas have an 

overrepresentation of populations below poverty, and an 

underrepresentation of minority and children’s populations.8

This action establishes national emission standards for new 

and existing gold mines. The EPA estimates that there are 

approximately 23 such locations covered by this rule. The rule 

will reduce emissions of mercury (Hg), and as a result have 

positive health and welfare benefits to sustenance fishing

communities, many of which are often considered to have 

environmental justice concerns. 

 

EPA defines “Environmental Justice” to include meaningful 

involvement of all people regardless of race, color, national 

 

4 U.S. GAO (Government Accountability Office). Demographics of People Living 

Near Waste Facilities. Washington DC: Government Printing Office; 1995. 5 Mohai P, Saha R. “Reassessing Racial and Socio-economic Disparities in 

Environmental Justice Research”. Demography. 2006;43(2): 383–399. 6 Mennis J. “Using Geographic Information Systems to Create and Analyze 

Statistical Surfaces of Populations and Risk for Environmental Justice 

Analysis”. Social Science Quarterly, 2002;83(1):281-297. 7 Bullard RD, Mohai P, Wright B, Saha R, et al. Toxic Waste and Race at Twenty 

1987-2007. United Church of Christ. March, 2007. 8 The results of the demographic analysis are presented in “Review of 

Environmental Justice Impacts for Gold Mines”, December 2010, a copy of which 

is available in the docket. 
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origin, or income with respect to the development, 

implementation, and enforcement of environmental laws, 

regulations, and polices. To promote meaningful involvement, 

EPA has developed a communication and outreach strategy to 

ensure that interested communities have access to this rule and 

are aware of its content. EPA will publicize the rulemaking via 

EJ newsletters, Tribal newsletters, EJ listservs, and the 

internet, including the Office of Policy, Economics, and 

Innovation’s (OPEI) Rulemaking Gateway web site 

(http://yosemite.epa.gov/opei/RuleGate.nsf/). EPA will also 

conduct targeted outreach to EJ communities as appropriate. 

Outreach activities may include providing general rulemaking 

fact sheets (e.g., why is this important for my community) for 

EJ community groups and conducting conference calls with 

interested communities. In addition, state and federal 

permitting requirements will provide state and local governments 

and members of affected communities the opportunity to provide 

comments on the permit conditions associated with permitting the 

sources affected by this rulemaking. 

Overall, this final rule is expected to reduce mercury 

emissions from gold mine ore processing and production 

facilities and thus decrease the amount of such emissions to 
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Page 168 of 217

which all affected populations are exposed.

K. Congressional Review Act

The Congressional Review Act, 5 U.S.C. 801 et seq., as 

added by the Small Business Regulatory Enforcement Fairness Act 

of 1996, generally provides that before a rule may take effect, 

the agency promulgating the rule must submit a rule report, 

which includes a copy of the rule, to each House of the Congress 

and to the Comptroller General of the United States. EPA will 

submit a report containing this final rule and other required 

information to the U.S. Senate, the U.S. House of 

Representatives, and the Comptroller General of the United 

States prior to publication of this final rule in the Federal

Register. A major rule cannot take effect until 60 days after 

it is published in the Federal Register. This action is not a 

“major rule” as defined by 5 U.S.C. 804(2). This final rule 

will be effective on [INSERT DATE OF PUBLICATION IN THE FEDERAL 

REGISTER].
National Emission Standards for Hazardous Air Pollutants: Gold 

Mine Ore Processing and Production Area Source Category; and 

Addition to Source Category List for Standards

Page 169 of 217

List of Subjects in 40 CFR Parts 9 and 63

Environmental protection, Air pollution control, Hazardous 

substances, Incorporations by reference, Reporting and 

recordkeeping requirements.

___________

Dated: 

____________________________

Lisa P. Jackson,

Administrator.
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For the reasons stated in the preamble, title 40, chapter I, of 

the Code of Federal Regulations is amended as follows:

PART 9—[AMENDED]

1. The authority citation for part 9 continues to read as 

follows:

Authority: 7 U.S.C. 135, et seq., 136–136y; 15 U.S.C. 

2001, 2003, 2005, 2006, 2601–2671; 21 U.S.C. 331j, 346a, 348; 31 

U.S.C. 9701; 33 U.S.C. 1251, et seq., 1311, 1313d, 1314, 1318, 

1321, 1326, 1330, 1342, 1344, 1345(d) and (e), 1361; E.O. 11735, 

38 FR 21243, 3 CFR, 1971–1975 Comp. p. 973; 42 U.S.C. 241, 242b, 

243, 246, 300f, 300g, 300g–1, 300g–2, 300g–3, 300g–4, 300g–5, 

300g–6, 300j–1, 300j–2, 300j–3, 300j–4, 300j–9, 1857, et seq., 

6901–6992k, 7401–7671q, 7542, 9601–9657, 11023, 11048.

Subpart A—[Amended]

* * * * *

2. The table in §9.1 is amended by adding an entry in 

numerical order for “63.11647–63.11648” under the heading 

“National Emission Standards for Hazardous Air Pollutants for 

Source Categories” to read as follows:

§9.1 OMB Approvals under the Paperwork Reduction Act.

* * * * *

40 CFR citation OMB control No.

* * * * *
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National Emission Standards for Hazardous Air Pollutants for 

Source Categories3

* * * * *

63.11647–63.11648 2060–NEW

* * * * *

* * * * *

3 The ICRs referenced in this section of the table encompass the 

applicable general provisions contained in 40 CFR part 63, 

subpart A, which are not independent information collection 

requirements.

* * * * *

PART 63—[AMENDED]

3. The authority citation for part 63 continues to read as 

follows:

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

Subpart A—[Amended]

4. Section 63.14 is amended by revising paragraphs (b)(35)

and (i)(1) and by adding paragraph (k)(1)(v) to read as follows:

§63.14 Incorporation by reference.

* * * * *

(b) * * *

(35) ASTM D6784–02, Standard Test Method for Elemental, 

Oxidized, Particle-Bound and Total Mercury in Flue Gas Generated 

from Coal-Fired Stationary Sources (Ontario Hydro Method), IBR 

approved for §63.11646(a)(1)(v) and table 5 to subpart DDDDD of 

this part.
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* * * * *

(i) * * *

(1) ANSI/ASME PTC 19.10–1981, “Flue and Exhaust Gas 

Analyses [Part 10, Instruments and Apparatus],” IBR approved for 

§§63.309(k)(1)(iii), 63.865(b), 63.3166(a)(3), 

63.3360(e)(1)(iii), 63.3545(a)(3), 63.3555(a)(3), 63.4166(a)(3), 

63.4362(a)(3), 63.4766(a)(3), 63.4965(a)(3), 63.5160(d)(1)(iii), 

63.9307(c)(2), 63.9323(a)(3), 63.11148(e)(3)(iii), 

63.11155(e)(3), 63.11162(f)(3)(iii) and (f)(4), 

63.11163(g)(1)(iii) and (g)(2), 63.11410(j)(1)(iii), 

63.11551(a)(2)(i)(C), 63.11646(a)(1)(iii), table 5 to subpart 

DDDDD of this part, and table 1 to subpart ZZZZZ of this part.

* * * * *

(k) * * *

(1) * * *

(v) Method 7471A, “Mercury in Solid or Semisolid Waste 

(Manual Cold-Vapor Technique),” IBR approved for 

§63.11647(f)(2).

* * * * *

5. Part 63 is amended by adding subpart EEEEEEE to read as 

follows:

Subpart EEEEEEE—National Emission Standards for Hazardous Air 

Pollutants: Gold Mine Ore Processing and Production Area Source 
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Category

Applicability and Compliance Dates

Sec.

63.11640 Am I subject to this subpart?

63.11641 What are my compliance dates?

Standards and Compliance Requirements

63.11645 What are my mercury emission standards?

63.11646 What are my compliance requirements?

63.11647 What are my monitoring requirements?

63.11648 What are my notification, reporting, and recordkeeping 

requirements?

Other Requirements and Information

63.11650 What General Provisions apply to this subpart?

63.11651 What definitions apply to this subpart?

63.11652 Who implements and enforces this subpart?

63.11653 [Reserved]

Tables to Subpart EEEEEEE of Part 63

Table 1 to Subpart EEEEEEE of Part 63—Applicability of General

Provisions to Subpart EEEEEEE

Subpart EEEEEEE—National Emission Standards for Hazardous Air 

Pollutants: Gold Mine Ore Processing and Production Area Source 

Category

Applicability and Compliance Dates

§63.11640 Am I subject to this subpart?

(a) You are subject to this subpart if you own or operate 

a gold mine ore processing and production facility as defined in 

§63.11651, that is an area source.

(b) This subpart applies to each new or existing affected 
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source. The affected sources are each collection of “ore 

pretreatment processes” at a gold mine ore processing and 

production facility, each collection of “carbon processes with 

mercury retorts” at a gold mine ore processing and production 

facility, each collection of “carbon processes without mercury 

retorts” at a gold mine ore processing and production facility, 

and each collection of “non-carbon concentrate processes" at a 

gold mine ore processing and production facility, as defined in 

§63.11651.

(1) An affected source is existing if you commenced 

construction or reconstruction of the affected source on or 

before April 28, 2010.

(2) An affected source is new if you commenced 

construction or reconstruction of the affected source after 

April 28, 2010.

(c) This subpart does not apply to research and 

development facilities, as defined in section 112(c)(7) of the 

Clean Air Act (CAA).

(d) If you own or operate a source subject to this 

subpart, you must have or you must obtain a permit under 40 CFR 

part 70 or 40 CFR part 71.

§63.11641 What are my compliance dates?

(a) If you own or operate an existing affected source, you 
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must comply with the applicable provisions of this subpart no 

later than [INSERT DATE 3 YEARS AFTER PUBLICATION OF THIS FINAL 

RULE IN THE FEDERAL REGISTER].

(b) If you own or operate a new affected source, and the 

initial startup of your affected source is on or before [INSERT 

DATE OF PUBLICATION OF THIS FINAL RULE IN THE FEDERAL REGISTER], 

you must comply with the provisions of this subpart no later 

than [INSERT DATE OF PUBLICATION OF THIS FINAL RULE IN THE 

FEDERAL REGISTER].

(c) If you own or operate a new affected source, and the 

initial startup of your affected source is after [INSERT DATE OF 

PUBLICATION OF THIS FINAL RULE IN THE FEDERAL REGISTER], you 

must comply with the provisions of this subpart upon startup of 

your affected source.

Standards and Compliance Requirements

§63.11645 What are my mercury emission standards?

(a) For existing ore pretreatment processes, you must emit 

no more than 127 pounds of mercury per million tons of ore

processed.

(b) For existing carbon processes with mercury retorts, 

you must emit no more than 2.2 pounds of mercury per ton of 

concentrate processed.

(c) For existing carbon processes without mercury retorts, 
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you must emit no more than 0.17 pounds of mercury per ton of 

concentrate processed.

(d) For existing non-carbon concentrate processes, you 

must emit no more than 0.2 pounds of mercury per ton of 

concentrate processed.

(e) For new ore pretreatment processes, you must emit no 

more than 84 pounds of mercury per million tons of ore

processed.

(f) For new carbon processes with mercury retorts, you 

must emit no more than 0.8 pounds of mercury per ton of 

concentrate processed.

(g) For new carbon processes without mercury retorts, you 

must emit no more than 0.14 pounds of mercury per ton of 

concentrate processed. 

(h) For new non-carbon concentrate processes, you must 

emit no more than 0.1 pounds of mercury per ton of concentrate

processed.

(i) The standards set forth in this section apply at all 

times. 

§63.11646 What are my compliance requirements?

(a) Except as provided in paragraph (b) of this section, 

you must conduct a mercury compliance emission test within 180

days of the compliance date for all process units at new and 
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existing affected sources according to the requirements in 

paragraphs (a)(1) through (13) of this section. This compliance 

testing must be repeated annually thereafter, with no two 

consecutive annual compliance tests occurring less than 3 months 

apart or more than 15 months apart.

(1) You must determine the concentration of mercury and 

the volumetric flow rate of the stack gas according to the 

following test methods and procedures:

(i) Method 1 or 1A (40 CFR part 60, appendix A-1) to 

select sampling port locations and the number of traverse points 

in each stack or duct. Sampling sites must be located at the 

outlet of the control device (or at the outlet of the emissions 

source if no control device is present) and prior to any 

releases to the atmosphere. 

(ii) Method 2, 2A, 2C, 2D, 2F (40 CFR part 60, appendix A1), or Method 2G (40 CFR part 60, appendix A-2) to determine the 

volumetric flow rate of the stack gas.

(iii) Method 3, 3A, or 3B (40 CFR part 60, appendix A-2) 

to determine the dry molecular weight of the stack gas. You may 

use ANSI/ASME PTC 19.10-1981, “Flue and Exhaust Gas Analyses” 

(incorporated by reference-see §63.14) as an alternative to EPA 

Method 3B.

(iv) Method 4 (40 CFR part 60, appendix A-3) to determine 
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the moisture content of the stack gas.

(v) Method 29 (40 CFR part 60, appendix A-8) to determine 

the concentration of mercury, except as provided in paragraphs 

(a)(1)(vi) and (vii) of this section.

(vi) Upon approval by the permitting authority, ASTM 

D6784–02; “Standard Test Method for Elemental, Oxidized, 

Particle-Bound and Total Mercury in Flue Gas Generated from 

Coal-Fired Stationary Sources (Ontario Hydro Method)” 

(incorporated by reference – see §63.14) may be used as an 

alternative to Method 29 to determine the concentration of 

mercury.

(vii) Upon approval by the permitting authority, Method 

30B (40 CFR part 60, appendix A-8) may be used as an alternative 

to Method 29 to determine the concentration of mercury for those 

process units with relatively low particulate-bound mercury as 

specified in Section 1.2 of Method 30B. 

(2) A minimum of three test runs must be conducted for 

each performance test of each process unit. Each test run 

conducted with Method 29 must collect a minimum sample volume of 

0.85 dry standard cubic meters (30 dry standard cubic feet). If 

conducted with Method 30B or Ontario Hydro Method, determine 

sample time and volume according to the testing criteria set 

forth in the relevant method. If the emission testing results 
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for any of the emission points yields a non-detect value, then 

the minimum detection limit (MDL) must be used to calculate the 

mass emissions rate (lb/hr) used to calculate the emissions 

factor (lb/ton) for that emission point and, in turn, for 

calculating the sum of the emissions (in units of pounds of 

mercury per ton of concentrate, or pounds of mercury per million 

tons of ore) for all emission points subject to the emission 

standard for determining compliance. If the resulting mercury 

emissions is greater than the MACT emission standard, the owner 

or operator may use procedures that produce lower MDL results 

and repeat the mercury emissions testing one additional time for 

any emission point for which the measured result was below the 

MDL. If this additional testing is performed, the results from 

that testing must be used to determine compliance (i.e., there

are no additional opportunities allowed to lower the MDL). 

(3) Performance tests shall be conducted under such 

conditions as the Administrator specifies to the owner or 

operator based on representative performance of the affected 

source for the period being tested. Upon request, the owner or 

operator shall make available to the Administrator such records 

as may be necessary to determine the conditions of performance 

tests. Performance tests must be conducted under operating 

conditions (including process or production throughputs) that 
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are based on representative performance. Record and report to 

the permit authority the process throughput for each test run. 

For sources with multiple emission units (e.g., two roasters, or 

a furnace, electrowinning circuit and a retort) ducted to a 

common control device and stack, compliance testing must be 

performed with all affected emissions units in operation if 

possible. If it is not possible to test all sources ducted to a 

common control device simultaneously, the sources can be tested 

separately. In such cases, any source that is not tested 

initially must be tested as soon as is practicable.

(4) Calculate the mercury emission rate (lb/hr), based on 

the average of 3 test run values, for each process unit using 

Equation (1) of this section:

E = Cs * Qs * K (Eq. 1)

Where:

E = mercury emissions in lb/hr;

Cs = concentration of mercury in the stack gas, in grains 

per dry standard cubic foot (gr/dscf);

Qs = volumetric flow rate of the stack gas, in dry 

standard cubic feet per hour; and

K = conversion factor for grains (gr) to pounds (lb), 

1.43 x 10-4

.

(5) Monitor and record the number of one-hour periods each 

process unit operates during each month.

(6) For the initial compliance determination for both new 

and existing sources, determine the total mercury emissions for 

all the full calendar months between the compliance date and the 
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date of the initial compliance test by multiplying the emission 

rate in lb/hr for each process unit by the number of one-hour 

periods each process unit operated during those full calendar 

months prior to the initial compliance test. This initial 

period must include at least 1 full month of operations. After 

the initial compliance test, for subsequent compliance tests, 

determine the mercury mass emissions for the 12 full calendar 

months prior to the compliance test in accordance with the 

procedures in paragraph (a)(7) of this section. Existing 

sources may use a previous emission test for their initial 

compliance determination in lieu of conducting a new test if the 

test was conducted within one year of the compliance date using 

the methods specified in paragraphs (a)(1) through (4) of this 

section, and the tests were representative of current operating 

processes and conditions. If a previous test is used for their 

initial compliance determination, 3 to 12 full months of data on 

hours of operation and production (i.e., million tons of ore, or 

tons of concentrate), including the month the test was 

conducted, must be used to calculate the emissions rate (in 

units of pounds of mercury per million tons of ore for the ore 

pretreatment affected sources, or in units of pounds of mercury 

per tons of concentrate for the other affected sources).

(7) For compliance determinations following the initial 
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compliance test for new and existing sources, determine the 

total mercury mass emissions for each process unit for the 12

full calendar months preceding the performance test by 

multiplying the emission rate in lb/hr for each process unit by 

the number of one-hour periods each process unit operated during 

the 12 full calendar months preceding the completion of the 

performance tests. 

(8) You must install, calibrate, maintain and operate an 

appropriate weight measurement device, mass flow meter, or 

densitometer and volumetric flow meter to measure ore throughput 

for each roasting operation and autoclave and calculate hourly,

daily and monthly totals in tons of ore according to paragraphs 

(a)(8)(i) and (ii) of this section.

(i) Measure the weight or the density and volumetric flow 

rate of the oxidized ore slurry as it exits the roaster 

oxidation circuit(s) and before the carbon-in-leach tanks. 

Alternatively, the weight of the ore can be measured “as fed” if 

approved by the permit authority as an acceptable equivalent 

method to measure amount of ore processed.

(ii) Measure the weight or the density and volumetric flow 

rate of the ore slurry as it is fed to the autoclave(s).

Alternatively, the weight or the density and volumetric flow 

rate of the oxidized ore slurry can be measured as it exits the 
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autoclave and before the carbon-in-leach tanks if approved by 

the permit authority as an acceptable equivalent method to 

measure amount of ore processed.

(9) Measure the weight of concentrate (produced by 

electrowinning, Merrill Crowe process, gravity feed, or other 

methods) using weigh scales for each batch prior to processing 

in mercury retorts or melt furnaces. For facilities with 

mercury retorts, the concentrate must be weighed in the same 

state and condition as it is when fed to the mercury retort. 

For facilities without mercury retorts, the concentrate must be 

weighed prior to being fed to the melt furnace before drying in 

any ovens. For facilities that ship concentrate offsite, 

measure the weight of concentrate as shipped offsite. You must 

keep accurate records of the weights of each batch of 

concentrate processed and calculate, and record the total weight 

of concentrate processed each month.

(10) You must maintain the systems for measuring density, 

volumetric flow rate, and weight within ±5 percent accuracy. 

You must describe the specific equipment used to make 

measurements at your facility and how that equipment is 

periodically calibrated. You must also explain, document, and 

maintain written procedures for determining the accuracy of the 

measurements and make these written procedures available to your 
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permitting authority upon request. You must determine, record, 

and maintain a record of the accuracy of the measuring systems 

before the beginning of your initial compliance test and during 

each subsequent quarter of affected source operation.

(11) Record the weight in tons of ore for ore pretreatment 

processes and concentrate for carbon processes with mercury 

retorts, carbon processes without mercury retorts, and for noncarbon concentrate processes on a daily and monthly basis.

(12) Calculate the emissions from each new and existing 

affected source for the sum of all full months between the 

compliance date and the date of the initial compliance test in 

pounds of mercury per ton of process input using the procedures 

in paragraphs (a)(12)(i) through (iv) of this section to 

determine initial compliance with the emission standards in 

§63.11645. This must include at least 1 full month of data. 

After this initial compliance test period, determine annual 

compliance using the procedures in paragraph (a)(13) of this 

section for existing sources.

(i) For ore pretreatment processes, divide the sum of 

mercury mass emissions (in pounds) from all roasting operations 

and autoclaves during the number of full months between the 

compliance date and the initial compliance test by the sum of 

the total amount of gold mine ore processed (in million tons) in 
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these process units during those same full months following the 

compliance date. If a previous test is used to determine 

initial compliance, pursuant to section 63.11646(a)(6), then the 

same 3 to 12 full months of production data (i.e., million tons 

of ore) and hours of operation referred to in section 

63.11646(a)(6), must be used to determine the emissions in 

pounds of mercury per million tons of ore.

(ii) For carbon processes with mercury retorts, divide the 

sum of mercury mass emissions (in pounds) from all carbon kilns, 

preg tanks, electrowinning, mercury retorts, and melt furnaces 

during the initial number of full months between the compliance 

date and the initial compliance tests by the total amount of 

concentrate (in tons) processed in these process units during 

those same full months following the compliance date. If a 

previous test is used to determine initial compliance, pursuant 

to section 63.11646(a)(6), then the same 3 to 12 full months of 

production data (i.e., tons of concentrate) and hours of 

operation referred to in section 63.11646(a)(6), must be used to 

determine the emissions in pounds of mercury per tons of 

concentrate.

(iii) For carbon processes without mercury retorts, divide 

the sum of mercury mass emissions (in pounds) from all carbon 

kilns, preg tanks, electrowinning, and melt furnaces during the 
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initial number of full months between the compliance date and 

the initial compliance tests by the total amount of concentrate 

(in tons) processed in these process units during those same 

full months following the compliance date. If a previous test 

is used to determine initial compliance, pursuant to section 

63.11646(a)(6), then the same 3 to 12 full months of production 

data (i.e., tons of concentrate) and hours of operation referred 

to in section 63.11646(a)(6), must be used to determine the 

emissions in pounds of mercury per tons of concentrate.

(iv) For non-carbon concentrate processes, divide the sum 

of mercury mass emissions (in pounds) from mercury retorts and 

melt furnaces during the initial number of full months between 

the compliance date and the initial compliance tests by the 

total amount of concentrate (in tons) processed in these process 

units during those same full months following the compliance 

date. If a previous test is used to determine initial 

compliance, pursuant to section 63.11646(a)(6), then the same 3 

to 12 full months of production data (i.e., tons of concentrate) 

and hours of operation referred to in section 63.11646(a)(6), 

must be used to determine the emissions in pounds of mercury per 

tons of concentrate.

(13) After the initial compliance test, calculate the 

emissions from each new and existing affected source for each 
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12-month period preceding each subsequent compliance test in 

pounds of mercury per ton of process input using the procedures 

in paragraphs (a)(13)(i) through (iv) of this section to 

determine compliance with the emission standards in §63.11645. 

(i) For ore pretreatment processes, divide the sum of 

mercury mass emissions (in pounds) from all roasting operations 

and autoclaves in the 12-month period preceding a compliance 

test by the sum of the total amount of gold mine ore processed

(in million tons) in that 12-month period.

(ii) For carbon processes with mercury retorts, divide the 

sum of mercury mass emissions (in pounds) from all carbon kilns, 

preg tanks, electrowinning, mercury retorts, and melt furnaces 

in the 12-month period preceding a compliance test by the total 

amount of concentrate (in tons) processed in these process units 

in that 12-month period.

(iii) For carbon processes without mercury retorts, divide 

the sum of mercury mass emissions (in pounds) from all carbon 

kilns, preg tanks, electrowinning, and melt furnaces in the 12-

month period preceding a compliance test by the total amount of 

concentrate (in tons) processed in these process units in that 

12-month period.

(iv) For non-carbon concentrate processes, divide the sum 

of mercury mass emissions (in pounds) from mercury retorts and 
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melt furnaces in the 12-month period preceding a compliance test 

by the total amount of concentrate (in tons) processed in these 

process units in that 12-month period.

(b) At all times, you must operate and maintain any 

affected source, including associated air pollution control 

equipment and monitoring equipment, in a manner consistent with 

safety and good air pollution control practices for minimizing 

emissions. Determination of whether such operation and 

maintenance procedures are being used will be based on 

information available to the Administrator which may include, 

but is not limited to, monitoring results, review of operation 

and maintenance procedures, review of operation and maintenance 

records, and inspection of the source.

§63.11647 What are my monitoring requirements?

(a) Except as provided in paragraph (a)(5) of this 

section, you must monitor each roaster for mercury emissions 

using one of the procedures in paragraphs (a)(1), (2), or (3) of 

this section and establish operating limits for mercury 

concentration as described in paragraph (a)(4) of this section.

(1) Perform sampling and analysis of the roaster’s exhaust 

for mercury concentration using EPA Performance Specification 

12B or EPA Method 30B at least twice per month. A minimum of 

two measurements must be taken per month that are at least 11 
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days apart from other consecutive tests. The mercury

concentration must be maintained below the operating limit 

established in paragraph (a)(4) of this section. The results of 

the sampling must be obtained within 72 hours of the time the 

sample is taken.

(i) To determine the appropriate sampling duration, you 

must review the available data from previous stack tests to 

determine the upper 99th percentile of the range of mercury 

concentrations in the exit stack gas. Based on this upper end 

of expected concentrations, select an appropriate sampling 

duration that is likely to provide a valid sample and not result 

in breakthrough of the sampling tubes. If breakthrough of the 

sampling tubes occurs, you must re-sample within 7 days using a 

shorter sampling duration.

(ii) If any mercury concentration measurement from the 

twice per month sampling with PS 12B or Method 30B is higher 

than the operating limit, the exceedance must be reported to the 

permit authority as a deviation and corrective actions must be 

implemented within 48 hours upon receipt of the sampling 

results. Moreover, within 96 hours of the exceedance, the owner 

or operator must measure the concentration again (with PS 12B, 

Method 30B, Method 29, or OHM) and demonstrate to the permit 

authority that the mercury concentration is no higher than the 
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operating limit, or inform the permit authority that the limit 

continues to be exceeded. If the operating limit is still 

exceeded after these 96 hours, the owner or operator must 

conduct a full compliance test for the ore-pretreatment affected 

source within 40 days to determine if the affected source is in 

compliance with the MACT emission standard. If the source is 

determined to be in compliance, the compliance test may also be 

used to establish a new operating limit for mercury 

concentration (in accordance with paragraph (e) of this 

section).

(2) Install, operate, calibrate, and maintain a continuous 

emissions monitoring system (CEMS) to continuously measure the 

mercury concentration in the final exhaust stream from each 

roaster according to the requirements of Performance 

Specification 12A (40 CFR part 60, appendix B) except that 

calibration standards traceable to the National Institute of 

Standards and Technology are not required. You must perform a 

data accuracy assessment of the CEMS according to section 5 of 

Appendix F in part 60 and follow the monitoring requirements in 

§63.8, except that 63.8(c)(1)(i) and (iii) no longer apply. 

Moreover, 63.8(d)(3) applies except the last sentence, which 

refers to an SSM plan. SSM plans are no longer required. 

(i) You must continuously monitor the daily average 
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mercury concentration from the roaster and maintain the daily 

average concentration below the operating limit established in 

paragraph (a)(4) of this section. 

(ii) If the daily average mercury concentration from the 

CEMs is higher than the operating limit, the exceedance must be 

reported to the permit authority as a deviation and corrective 

actions must be implemented within 48 hours upon receipt of the 

sampling results. Moreover, within 96 hours of the exceedance, 

the owner or operator must measure the concentration again (with 

the CEMs) and demonstrate to the permit authority that the 

mercury concentration is no higher than the operating limit, or 

inform the permit authority that the limit continues to be 

exceeded. If the operating limit is still exceeded after these 

96 hours, the owner or operator must conduct a full compliance 

test for the ore-pretreatment affected source within 40 days to 

determine if the affected source is in compliance with the MACT 

emission standard. If the source is determined to be in 

compliance, the compliance test results may also be used to 

establish a new operating limit for mercury concentration (in 

accordance with paragraph (e) of this section).

(iii) You must submit a monitoring plan that includes 

quality assurance and quality control (QA/QC) procedures 

sufficient to demonstrate the accuracy of the CEMS to your 
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permitting authority for approval 180 days prior to your initial 

compliance test. At a minimum, the QA/QC procedures must 

include daily calibrations and an annual accuracy test for the 

CEMS.

(3) Continuously measure the mercury concentration in the 

final exhaust stream from each roaster using EPA Performance 

Specification 12B.

(i) You must continuously measure the mercury 

concentration in the roaster exhaust and maintain the average 

daily mercury concentration below the operating limit 

established in paragraph (a)(4) of this section. To determine 

the appropriate sampling duration, you must review the available 

data from previous stack tests to determine the upper 99th 

percentile of the range of mercury concentrations in the exit 

stack gas. Based on this upper end of expected concentrations, 

select an appropriate sampling duration that is likely to 

provide a valid sample and not result in breakthrough of the 

sampling tubes. If breakthrough of the sampling tubes occurs, 

you must re-sample within 7 days using a shorter sampling 

duration.

(ii) If the daily average mercury concentration is higher 

than the operating limit, the exceedance must be reported to the 

permit authority as a deviation and corrective actions must be 
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implemented within 48 hours upon receipt of the sampling 

results. Moreover, within 96 hours of the exceedance, the owner 

or operator must measure the concentration again with PS 12B, 

Method 30B, Method 29, or OHM and demonstrate to the permit 

authority that the mercury concentration is no higher than the 

operating limit, or inform the permit authority that the limit 

continues to be exceeded. If the operating limit is still 

exceeded after these 96 hours, the owner or operator must 

conduct a full compliance test for the ore-pretreatment affected 

source within 40 days to determine if the affected source is in 

compliance with the MACT emission standard. If the source is 

determined to be in compliance, the compliance test results may 

also be used to establish a new operating limit for mercury 

concentration (in accordance with paragraph (e) of this 

section). 

(4) Use Equation (2) of this section to establish an upper 

operating limit for mercury concentration as determined by using 

the procedures in paragraphs (a)(1), (2), or (3) of this section

concurrently while you are conducting your annual compliance 

performance stack test according to the procedures in 

§63.11646(a).

OLR = Ctest * (EL/CT) (Eq 2)

where
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OLR = mercury concentration operating limit for the 

roaster (in micrograms per cubic meter);

Ctest = average mercury concentration measured by the 

monitoring procedures (PS 12A or PS 12B or 30B) 

during the annual performance stack test (in 

micrograms per cubic meter);

EL = emission standard for ore pretreatment processes (in 

lb/ million tons of ore);

CT = compliance test results for ore pretreatment 

processes (in lb/ million tons of ore).

(5) For roasters that utilize calomel-based mercury 

control systems for emissions controls, you are not required to 

perform the monitoring for mercury emissions in paragraphs

(a)(1), (2), or (3) of this section if you demonstrate to the 

satisfaction of your permitting authority that mercury emissions 

from the roaster are less than 10 pounds of mercury per million 

tons of ore throughput. If you make this demonstration, you 

must conduct the parametric monitoring as described below in 

paragraphs (b) and (c) of this section. 

(i) The initial demonstration must include three or more 

consecutive independent stack tests for mercury at least one 

month apart on the roaster exhaust stacks. Subsequent 

demonstrations may be based upon the single stack test required 

in paragraph (a) of section §63.11646. The results of each of 

the tests must be less than 10 pounds of mercury per million 

tons of ore. The testing must be performed according to the 

procedures in §63.11646(a)(1) through (4) to determine mercury 

emissions in pounds per hour. 
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(ii) Divide the mercury emission rate in pounds per hour

by the ore throughput rate during the test expressed in millions 

of tons per hour to determine the emissions in pounds per 

million tons of ore. 

(b) For facilities with roasters and a calomel-based 

mercury control system that choose to monitor for mercury 

emissions using the procedures in paragraph (a)(1) of this 

section or that qualify for and choose to follow the 

requirements in paragraph (a)(5) of this section, you must 

establish operating parameter limits for scrubber liquor flow

(or line pressure) and scrubber inlet gas temperature and 

monitor these parameters. You may establish your operating 

parameter limits from the initial compliance test, according to 

the manufacturer’s specifications, or based on limits 

established by the permitting authority. If you choose to 

establish your operating parameter limits from the initial 

compliance test, monitor the scrubber liquor flow (or line 

pressure) and scrubber inlet gas temperature during each run of 

your initial compliance test. The minimum operating limit for 

scrubber liquor flow rate (or line pressure) is either the 

lowest value during any run of the initial compliance test or 10 

percent less than the average value measured during the 

compliance test, and your maximum scrubber inlet temperature 
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limit is the highest temperature measured during any run of the 

initial compliance test or 10 percent higher than the average 

value measured during the compliance test. You must monitor the 

scrubber liquor flow rate (or line pressure) and scrubber inlet 

gas temperature hourly and maintain the scrubber liquor flow (or 

line pressure) at or above the established operating parameter

and maintain the inlet gas temperature below the established 

operating parameter limit. 

(c) For facilities with roasters and a calomel-based 

mercury control system that choose to monitor for mercury 

emissions using the procedures in paragraph (a)(1) of this 

section or that qualify for and follow the requirements in 

paragraph (a)(5) of this section, you must establish operating 

parameter ranges for mercuric ion and chloride ion 

concentrations or for oxidation reduction potential and pH using 

the procedures in paragraph (c)(1) or (2) of this section

respectively. 

(1) Establish the mercuric ion concentration and chloride 

ion concentration ranges for each calomel-based mercury control 

system. The mercuric ion concentration and chloride ion 

concentration ranges for each calomel-based mercury control 

system must be based on the manufacturer’s specifications, or

based on approval by your permitting authority. Measure the 
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mercuric ion concentration and chloride ion concentrations at 

least once during each run of your initial compliance test. The 

measurements must be within the established concentration range 

for mercuric ion concentration and chloride ion concentration. 

Subsequently, you must sample at least once daily and maintain 

the mercuric ion concentration and chloride ion concentrations 

within their established range.

(2) Establish the oxidation reduction potential and pH 

range for each calomel-based mercury control system. The 

oxidation reduction potential and pH range for each calomelbased mercury control system must be based on the manufacturer’s 

specifications, or based on approval by your permitting 

authority. Install monitoring equipment to continuously monitor 

the oxidation reduction potential and pH of the calomel-based 

mercury control system scrubber liquor. Measure the oxidation 

reduction potential and pH of the scrubber liquor during each 

run of your initial compliance test. The measurements must be 

within the established range for oxidation reduction potential 

and pH. Subsequently, you must monitor the oxidation reduction 

potential and pH of the scrubber liquor continuously and 

maintain it within the established operating range.

(d) If you have an exceedance of a control device 

operating parameter range provided in paragraphs (b) or (c) of 
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this section, you must take corrective action and bring the 

parameters back into the established parametric ranges. If the 

corrective actions taken following an exceedance do not result 

in the operating parameter value being returned within the 

established range within 48 hours, a mercury concentration 

measurement (with PS 12B, CEMS, Method 30B, Method 29, or OHM) 

must be made to determine if the operating limit for mercury 

concentration is being exceeded. The measurement must be 

performed and the mercury concentration determined within 48

hours (after the initial 48 hours, or a total of 96 hours from 

the time the parameter range was exceeded). If the measured 

mercury concentration meets the operating limit for mercury 

concentration established under §63.11647(a)(4), the corrective 

actions are deemed successful, and the owner or operator can 

request the permit authority to establish a new limit or range 

for the parameter. If the measured mercury concentration 

exceeds the operating limit for mercury concentration after 

these 96 hours, the exceedance must be reported as a deviation

within 24 hours to the permitting authority. The owner or 

operator must conduct a compliance test pursuant to §63.11646(a) 

within 40 days to determine if the roaster operations are in 

compliance with the MACT emission standard. If the source is 

determined to be in compliance with the MACT emission standard, 
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the compliance test may also be used to establish a new 

operating limit for mercury concentration (see paragraph (e) of 

this section).

(e) You may submit a request to your permitting authority 

for approval to change the operating limits established under 

paragraph (a)(4) of this section for the monitoring required in 

paragraph (a)(1),(2), or (3) of this section. In the request, 

you must demonstrate that the proposed change to the operating 

limit detects changes in levels of mercury emission control. An 

approved change to the operating limit under this paragraph only 

applies until a new operating limit is established during the 

next annual compliance test.

(f) You must monitor each process unit at each new and 

existing affected source that uses a carbon adsorber to control 

mercury emissions using the procedures in paragraphs (f)(1) or

(2) of this section. A carbon adsorber may include a fixed 

carbon bed, carbon filter packs or modules, carbon columns, and 

other variations.

(1) Continuously sample and analyze the exhaust stream 

from the carbon adsorber for mercury using Method 30B (40 CFR 

part 60, appendix A-8) for a duration of at least the minimum 

sampling time specified in Method 30B and up to one week that 

includes the period of the annual performance test.
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(i) Establish an upper operating limit for the process as 

determined using the mercury concentration measurements from the 

sorbent trap as calculated from Equation (3) of this section.

OLC = Ctrap * (EL/CT) (Eq 3)

where

OLC = mercury concentration operating limit for the carbon 

adsorber control device on the process as measured 

using the sorbent trap, (micrograms per cubic 

meter);

Ctrap = average mercury concentration measured using the 

sorbent trap during the week that includes the 

performance test, (micrograms per cubic meter);

EL = emission standard for the affected sources (lb/ton 

of concentrate);

CT = compliance test results for the affected sources 

(lb/ton of concentrate).

(ii) Sample and analyze the exhaust stream from the carbon 

adsorber for mercury at least monthly using Method 30B (40 CFR 

part 60, appendix A-8). When the mercury concentration reaches 

75 percent of the operating limit, begin weekly sampling and 

analysis. When the mercury concentration reaches 90 percent of 

the operating limit, replace the carbon in the carbon adsorber 

within 30 days. If mercury concentration exceeds the operating 

limit, change the carbon in the carbon adsorber within 30 days

and report the deviation to your permitting authority.

(2) Conduct an initial sampling of the carbon in the 

carbon bed for mercury 90 days after the replacement of the 

carbon. A representative sample must be collected from the 
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inlet of the bed and the exit of the bed and analyzed using EPA 

Method 7471A (incorporated by reference - see §63.14). The 

depth to which the sampler is inserted must be recorded. The 

design capacity is established by calculating the average carbon 

loading from the inlet and outlet measurements. Sampling and 

analysis of the carbon bed for mercury must be performed 

quarterly thereafter. When the carbon loading reaches 50 

percent of the design capacity of the carbon, monthly sampling 

must be performed until 90 percent of the carbon loading 

capacity is reached. The carbon must be removed and replaced 

with fresh carbon no later than 30 days after reaching 90 

percent of capacity. For carbon designs where there may be 

multiple carbon columns or beds, a representative sample may be 

collected from the first and last column or bed instead of the 

inlet or outlet. If the carbon loading exceeds the design 

capacity of the carbon, change the carbon within 30 days and 

report the deviation to your permitting authority. 

(g) You must monitor gas stream temperature at the inlet 

to the carbon adsorber for each process unit (i.e., carbon kiln, 

melt furnace, etc.) equipped with a carbon adsorber. Establish 

a maximum value for the inlet temperature either during the 

annual performance test (required in §63.11646(a)), according to 

the manufacturer’s specifications, or as approved by your 
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permitting authority. If you choose to establish the 

temperature operating limit during the performance test, 

establish the temperature operating limit based on either the 

highest reading during the test or at 10°F higher than the 

average temperature measured during the performance test. 

Monitor the inlet temperature once per shift. If an inlet 

temperature exceeds the temperature operating limit, you must 

follow the requirements for outlet concentration measurement in 

paragraph (f)(1) of this section. If the concentration is below 

90 percent of the operating limit, you may set a new temperature 

operating limit 10°F above the previous operating limit. If the 

concentration is above 90 percent of the operating limit, you 

must take corrective action within 48 hours to reduce the 

temperature back below the temperature operating limit and again 

measure the outlet concentration within 96 hours of the 

exceedance of the temperature limit according to paragraph 

(f)(1) of this section. If the concentration is still above 90

percent of the operating limit, then you must change the carbon 

in the bed within 30 days and report the event to your 

permitting authority, and reestablish an appropriate maximum 

temperature limit based on approval of your permit authority. 

(h) For each wet scrubber at each new and existing 

affected source not followed by a mercury control system, you 
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must monitor the water flow rate (or line pressure) and pressure 

drop. Establish a minimum value as the operating limit for 

water flow rate (or line pressure) and pressure drop either 

during the performance test required in §63.11646(a), according 

to the manufacturer’s specifications, or as approved by your 

permitting authority. If you choose to establish the operating 

limit based on the results of the performance test, the new 

operating limit must be established based on either the lowest 

average value during any test run or no lower than 10 percent of 

the average value measured during the test. For wet scrubbers 

on an autoclave, establish the pressure drop range according to 

manufacturer’s specifications. You must monitor the water flow 

rate and pressure drop once per shift and take corrective action 

within 24 hours if any daily average is less than the operating 

limit. If the parameters are not in range within 72 hours, the 

owner or operator must report the deviation to the permitting 

authority and perform a compliance test within 40 days to 

determine if the source is in compliance with the MACT limit. 

(i) You may conduct additional compliance tests according 

to the procedures in §63.11646 and re-establish the operating 

limits required in paragraphs (a) through (c) and (f) through 

(h) of this section at any time. You must submit a request to 

your permitting authority for approval to re-establish the 
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operating limits. In the request, you must demonstrate that the 

proposed change to the operating limit detects changes in levels 

of mercury emission control. An approved change to the 

operating limit under this paragraph only applies until a new 

operating limit is established during the next annual compliance 

test.

§63.11648 What are my notification, reporting, and 

recordkeeping requirements?

(a) You must submit the Initial Notification required by 

§63.9(b)(2) no later than 120 calendar days after the date of 

publication of the final rule in the Federal Register or within 

120 days after the source becomes subject to the standard. The 

Initial Notification must include the information specified in 

§63.9(b)(2)(i) through (b)(2)(iv). 

(b) You must submit an initial Notification of Compliance 

Status as required by §63.9(h).

(c) If a deviation occurs during a semiannual reporting 

period, you must submit a deviation report to your permitting 

authority according to the requirements in paragraphs (c)(1) and 

(2) of this section.

(1) The first reporting period covers the period beginning 

on the compliance date specified in §63.11641 and ending on June 

30 or December 31, whichever date comes first after your 
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compliance date. Each subsequent reporting period covers the 

semiannual period from January 1 through June 30 or from July 1 

through December 31. Your deviation report must be postmarked 

or delivered no later than July 31 or January 31, whichever date 

comes first after the end of the semiannual reporting period. 

(2) A deviation report must include the information in 

paragraphs (c)(2)(i) through (iv) of this section.

(i) Company name and address.

(ii) Statement by a responsible official, with the 

official’s name, title, and signature, certifying the truth, 

accuracy and completeness of the content of the report.

(iii) Date of the report and beginning and ending dates of 

the reporting period.

(iv) Identification of the affected source, the pollutant 

being monitored, applicable requirement, description of 

deviation, and corrective action taken.

(d) If you had a malfunction during the reporting period, 

the compliance report required in § 63.11648(b) must include the 

number, duration, and a brief description for each type of 

malfunction which occurred during the reporting period and which 

caused or may have caused any applicable emission limitation to 

be exceeded. The report must also include a description of 

actions taken by an owner or operator during a malfunction of an 
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affected source to minimize emissions in accordance with 

§63.11646(b), including actions taken to correct a malfunction. 

(e) You must keep the records specified in paragraphs 

(e)(1) through (3) of this section. The form and maintenance of 

records must be consistent with the requirements in section 

63.10(b)(1) of the General Provisions.

(1) As required in §63.10(b)(2)(xiv), you must keep a copy 

of each notification that you submitted to comply with this 

subpart and all documentation supporting any Initial 

Notification, Notification of Compliance Status, and semiannual 

compliance certifications that you submitted.

(2) You must keep the records of all performance tests, 

measurements, monitoring data, and corrective actions required 

by §§63.11646 and 63.11647, and the information identified in 

paragraphs (c)(2)(i) through (vi) of this section for each

corrective action required by §63.11647.

(i) The date, place, and time of the monitoring event 

requiring corrective action;

(ii) Technique or method used for monitoring;

(iv) Operating conditions during the activity;

(v) Results, including the date, time, and duration of the 

period from the time the monitoring indicated a problem to the 

time that monitoring indicated proper operation; and
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(vi) Maintenance or corrective action taken (if 

applicable).

(3) You must keep records of operating hours for each 

process as required by §63.11646(a)(5) and records of the 

monthly quantity of ore and concentrate processed or produced as 

required by §63.11646(a)(10).

(f) Your records must be in a form suitable and readily 

available for expeditious review, according to §63.10(b)(1). As 

specified in §63.10(b)(1), you must keep each record for 5 years 

following the date of each recorded action. You must keep each 

record onsite for at least 2 years after the date of each 

recorded action according to §63.10(b)(1). You may keep the 

records offsite for the remaining 3 years.

(g) After December 31, 2011, within 60 days after the date 

of completing each performance evaluation conducted to 

demonstrate compliance with this subpart, the owner or operator 

of the affected facility must submit the test data to EPA by 

entering the data electronically into EPA’s WebFIRE data base 

through EPA’s Central Data Exchange. The owner or operator of 

an affected facility shall enter the test data into EPA’s data 

base using the Electronic Reporting Tool or other compatible 

electronic spreadsheet. Only performance evaluation data 

collected using methods compatible with ERT are subject to this 
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requirement to be submitted electronically into EPA’s WebFIRE 

database.

Other Requirements and Information

§63.11650 What General Provisions apply to this subpart?

Table 1 to this subpart shows which parts of the General 

Provisions in §§63.1 through 63.16 apply to you.

§63.11651 What definitions apply to this subpart?

Terms used in this subpart are defined in the Clean Air 

Act, in §63.2, and in this section as follows:

Autoclave means a pressure oxidation vessel that is used to 

treat gold ores (primarily sulfide refractory ore) and involves 

pumping a slurry of milled ore into the vessel which is highly 

pressurized with oxygen and heated to temperatures of 

approximately 350° to 430°F.

Calomel-based mercury control system means a mercury 

emissions control system that uses scrubbers to remove mercury 

from the gas stream of a roaster or combination of roasters by 

complexing the mercury from the gas stream with mercuric 

chloride to form mercurous chloride (calomel). These scrubbers 

are also referred to as “mercury scrubbers.”

Carbon adsorber means a control device consisting of a 

single fixed carbon bed, multiple carbon beds or columns, carbon 

filter packs or modules, and other variations that uses 
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activated carbon to remove pollutants from a gas stream.

Carbon kiln means a kiln or furnace where carbon is 

regenerated by heating, usually in the presence of steam, after 

the gold has been stripped from the carbon.

Carbon processes with mercury retorts means the affected 

source that includes carbon kilns, preg tanks, electrowinning

cells, mercury retorts, and melt furnaces at gold mine ore 

processing and production facilities that use activated carbon, 

or resins that can be used as a substitute for activated carbon,

to recover (adsorb) gold from the pregnant cyanide solution.

Carbon processes without mercury retorts means the affected 

source that includes carbon kilns, preg tanks, electrowinning 

cells, and melt furnaces, but has no retorts, at gold mine ore 

processing and production facilities that use activated carbon, 

or resins that can be used as a substitute for activated carbon,

to recover (adsorb) gold from the pregnant cyanide solution.

Concentrate means the sludge-like material that is loaded 

with gold along with various other metals (such as silver, 

copper, and mercury) and various other substances, that is 

produced by electrowinning, the Merrill-Crowe process, flotation 

and gravity separation processes. Concentrate is measured as 

the input to mercury retorts, or for facilities without mercury 

retorts, as the input to melt furnaces before any drying takes 
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place. For facilities without mercury retorts or melt furnaces, 

concentrate is measured as the quantity shipped. 

Deviation means any instance where an affected source 

subject to this subpart, or an owner or operator of such a 

source:

(1) Fails to meet any requirement or obligation 

established by this subpart, including but not limited to any 

emissions limitation or work practice standard;

(2) Fails to meet any term or condition that is adopted to 

implement an applicable requirement in this subpart and that is 

included in the operating permit for any affected source 

required to obtain such a permit; or

(3) Exceeds any operating limit established under this 

subpart.

Electrowinning means a process that uses induced voltage on 

anode and cathode plates to remove metals from the continuous 

flow of solution, where the gold in solution is plated onto the 

cathode. Steel wool is typically used as the plating surface. 

Electrowinning Cells means a tank in which the 

electrowinning takes place.

Gold mine ore processing and production facility means any 

industrial facility engaged in the processing of gold mine ore 

that uses any of the following processes: roasting operations, 
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autoclaves, carbon kilns, preg tanks, electrowinning, mercury 

retorts, or melt furnaces. Laboratories (see CAA section 

112(c)(7)), individual prospectors, and very small pilot scale 

mining operations that processes or produces less than 100

pounds of concentrate per year are not a gold mine ore 

processing and production facility. A facility that produces 

primarily metals other than gold, such as copper, lead, zinc, or 

nickel (where these metals other than gold comprise 95 percent 

or more of the total metal production) that may also recover 

some gold as a byproduct is not a gold mine ore processing and 

production facility. Those facilities whereby 95 percent or 

more of total mass of metals produced are metals other than 

gold, whether final metal production is onsite or offsite, are 

not part of the gold mine ore processing and production source 

category. 

Melt furnace means a furnace (typically a crucible furnace) 

that is used for smelting the gold-bearing material recovered 

from mercury retorting, or the gold-bearing material from 

electrowinning, the Merrill-Crowe process, or other processes 

for facilities without mercury retorts. 

Mercury retort means a vessel that is operated under a 

partial vacuum at approximately 1100° to 1300oF to remove 

mercury and moisture from the gold bearing sludge material that 
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is recovered from electrowinning, the Merrill-Crowe process, or 

other processes. Mercury retorts are usually equipped with 

condensers that recover liquid mercury during the processing.

Merrill-Crowe process means a precipitation technique using 

zinc oxide for removing gold from a cyanide solution. Zinc dust 

is added to the solution, and gold is precipitated to produce a 

concentrate.

Non-carbon concentrate processes means the affected source 

that includes mercury retorts and melt furnaces at gold mine ore 

processing and production facilities that use the Merrill-Crowe 

process or other processes and do not use carbon (or resins that 

substitute for carbon) to recover (adsorb) gold from the 

pregnant cyanide solution.

Ore dry grinding means a process in which the gold ore is 

ground and heated (dried) prior to additional preheating or 

prior to entering the roaster.

Ore preheating means a process in which ground gold ore is 

preheated prior to entering the roaster.

Ore pretreatment processes means the affected source that 

includes roasting operations and autoclaves that are used to 

pre-treat gold mine ore at gold mine ore processing and 

production facilities prior to the cyanide leaching process.

Pregnant solution tank (or preg tank) means a storage tank 
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for pregnant solution, which is the cyanide solution that 

contains gold-cyanide complexes that is generated from leaching 

gold ore with cyanide solution.

Pregnant cyanide solution means the cyanide solution that 

contains gold-cyanide complexes that are generated from leaching 

gold ore with a dilute cyanide solution.

Quenching means a process in which the hot calcined ore is 

cooled and quenched with water after it leaves the roaster. 

Roasting operation means a process that uses an industrial 

furnace in which milled ore is combusted across a fluidized bed 

to oxidize and remove organic carbon and sulfide mineral grains 

in refractory gold ore. The emissions points of the roasting 

operation subject to this subpart include ore dry grinding, ore 

preheating, the roaster stack, and quenching. 

§63.11652 Who implements and enforces this subpart?

(a) This subpart can be implemented and enforced by the 

U.S. EPA or a delegated authority, such as your state, local, or 

tribal agency. If the U.S. EPA Administrator has delegated 

authority to your state, local, or tribal agency, then that 

agency has the authority to implement and enforce this subpart. 

You should contact your U.S. EPA Regional Office to find out if 

this subpart is delegated to your state, local, or tribal 

agency.
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(b) In delegating implementation and enforcement authority 

of this subpart to a state, local, or tribal agency under 40 CFR 

part 63, subpart E, the authorities contained in paragraph (c) 

of this section are retained by the Administrator of the U.S. 

EPA and are not transferred to the state, local, or tribal 

agency.

(c) The authorities that will not be delegated to state, 

local, or tribal agencies are listed in paragraphs (c)(1) 

through (4) of this section.

(1) Approval of alternatives to the applicability 

requirements in §63.11640, the compliance date requirements in 

§63.11641, and the applicable standards in §63.11645.

(2) Approval of an alternative nonopacity emissions 

standard under §63.6(g). 

(3) Approval of a major change to a test method under 

§63.7(e)(2)(ii) and (f). A “major change to test method” is 

defined in §63.90(a).

(4) Approval of a major change to monitoring under 

§63.8(f). A “major change to monitoring” is defined in 

§63.90(a).

(5) Approval of a waiver of recordkeeping or reporting 

requirements under §63.10(f), or another major change to 

recordkeeping/reporting. A “major change to 
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recordkeeping/reporting” is defined in §63.90(a).

§63.11653 [Reserved]

Tables to Subpart EEEEEEE of Part 63

Table 1 to Subpart EEEEEEE of Part 63—Applicability of General 

Provisions to Subpart EEEEEE

As stated in §63.11650, you must comply with the applicable 

General Provisions requirements according to the following 

table:

Citation Subject

Applies 

to 

subpart 

EEEEEEE Explanation

§63.1(a)(1), (a)(2), 

(a)(3), (a)(4), 

(a)(6), (a)(10)–

(a)(12), (b)(1), 

(b)(3), (c)(1), 

(c)(2), (c)(5), (e)

Applicability Yes

§63.1(a)(5), (a)(7)–

(a)(9), (b)(2), 

(c)(3), (c)(4), (d)

Reserved No

§63.2 Definitions Yes

§63.3 Units and AbbreviationsYes

§63.4 Prohibited Activities 

and Circumvention

Yes

§63.5 Preconstruction Review 

and Notification 

Requirements

Yes

§63.6(a), (b)(1)–

(b)(5), (b)(7), 

(c)(1), (c)(2), 

(c)(5), 

(e)(1)(iii),(f)(2), 

(f)(3), (g), (i), (j)

Compliance with 

Standards and 

Maintenance 

Requirements

Yes

§63.6(e)(1)(i) and 

(ii), (e)(3), 

Startup, Shutdown and 

Malfunction 

No Subpart 

EEEEEEE
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and(f)(1) Requirements (SSM) standards 

apply at all 

times.

§63.6(h)(1), (h)(2), 

(h)(4),(h)(5)(i), 

(ii), (iii) and (v), 

(h)(6)–(h)(9)

Compliance with Opacity 

and Visible Emission 

Limits

No Subpart 

EEEEEEE does 

not contain 

opacity or 

visible 

emission

limits.

§63.6(b)(6), (c)(3), 

(c)(4), (d), (e)(2), 

(e)(3)(ii), (h)(3), 

(h)(5)(iv)

Reserved No

§63.7, except (e)(1) Applicability and 

Performance Test Dates

Yes

§ 63.7(e)(1) Performance Testing 

Requirements Related to 

SSM

No

§63.8(a)(1), (b)(1), 

(f)(1)-(5), (g)

Monitoring RequirementsYes

§63.8(a)(2), (a)(4), 

(b)(2)-(3), (c), (d), 

(e), (f)(6), (g)

Continuous Monitoring 

Systems 

Yes Except cross 

references 

to SSM 

requirements 

in 

§63.6(e)(1) 

and (3) do 

not apply

§63.8(a)(3) [Reserved] No

§63.9(a), (b)(1), 

(b)(2)(i)-(v),

(b)(4), (b)(5), (c), 

(d), (e), (g),

(h)(1)–(h)(3), 

(h)(5), (h)(6), (i), 

(j)

Notification 

Requirements

Yes

§63.9(f) No

§63.9(b)(3), (h)(4) Reserved No
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§63.10(a), (b)(1), 

(b)(2)(vi)–(xiv), 

(b)(3), (c), (d)(1)-

(4), (e), (f)

Recordkeeping and 

Reporting Requirements

Yes

§ 63.10(b)(2)(i)-(v), 

(d)(5)

Recordkeeping/Reporting 

Associated with SSM

No

§63.10(c)(2)–(c)(4), 

(c)(9)

Reserved No

§63.11 Control Device 

Requirements

No

§63.12 State Authority and 

Delegations

Yes

§§63.13–63.16 Addresses, 

Incorporations by 

Reference, Availability 

of Information, 

Performance Track 

Provisions

Yes