Form for Compliance with E.O. 12866 Docket Requirements 

Title of Regulation: National Emission Standards for Hazardous Air Pollutants for Gold Mine Ore 

Processing and Production 

Contact person: Chuck French, EPA/OAQPS/SPPD/MMG 

Phone number: (919) 541-7912 

Was this regulation reviewed by OMB under Executive Order 12866 - Regulatory Planning and 

Review? 

9Yes No. 

If you checked “no”, you are done with this form. Simply place it in the docket for your 

regulation. If you checked “yes”, please fill out the remainder of the form before placing it in the 

docket. Also docket any relevant documents referenced in the form. 

For regulations that are checked “Yes” above: 

This regulation was reviewed by OMB under Executive Order 12866 - Regulatory Planning and 

Review. 

Attached is the draft regulation and any other documents sent to OMB for review, such as 

analyses and assessments. E.O. 12866 requires agencies to make these publicly available. 

E.O. 12866 also requires agencies to identify the substantive changes between the draft regulation 

sent to OMB for review and the regulation subsequently announced [Please check the appropriate 

box below:] 

 

 9 EPA made substantive changes to this regulation 

(includes changes initiated by EPA or OMB). 

Attached is a document which: (1) identifies all the substantive changes made, and (2) 

notes those changes OMB suggested or recommended. 

 

 No substantive changes were made to this regulation

 Therefore, no further attachments are required. 

If you have questions about this regulation, please call the EPA contact person listed above. 
1

6560-50-P 

ENVIRONMENTAL PROTECTION AGENCY 

40 CFR Part 63

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

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: Proposed rule. 

SUMMARY: EPA is proposing to adding the gold mine ore 

processing and production area source category to the list of 

source categories subject to regulation under the hazardous air 

pollutant section of the Clean Air Act (CAA) due to their 

mercury emissions. Subsequent to its listing EPA is also 

proposing national mercury emission standards for this category 

based on the emissions level of the best performing facilities 

which are well controlled for mercury. EPA is soliciting 

comments on all aspects of this proposed rule. 

DATES: Comments must be received on or before [INSERT DATE 30

DAYS AFTER PUBLICATION IN THE FEDERAL REGISTER] unless a public 

hearing is requested by [INSERT DATE 10 DAYS AFTER PUBLICATION 

IN THE FEDERAL REGISTER]. If a hearing is requested on this 

proposed rule, written comments must be received by [INSERT DATE 

45 DAYS AFTER PUBLICATION IN THE FEDERAL REGISTER]. Under the 

Paperwork Reduction Act, comments on the information collection 
2

provisions must be received by the Office of Management and 

Budget (OMB) on or before [INSERT DATE 30 DAYS AFTER PUBLICATION 

IN THE FEDERAL REGISTER]. 

ADDRESSES: Submit your comments, identified by Docket ID No. 

EPA-HQ-OAR-2010-0239, by one of the following methods: 

• Follow the on-line instructions for submitting comments at 

the following web address: www.regulations.gov. 

• E-mail: Comments may be sent by electronic mail (e-mail) 

to a-and-r-Docket@epa.gov, Attention Docket ID No. EPA-HQOAR-2010-0239. 

• Fax: Fax your comments to: (202) 566-9744, Attention 

Docket ID No. EPA-HQ-OAR-2010-0239. 

• Mail: Send your comments to: Air and Radiation Docket and 

Information Center, Environmental Protection Agency, 

Mailcode: 2822T, 1200 Pennsylvania Ave., NW, Washington, 

DC 20460, Attention: Docket ID No. EPA-HQ-OAR-2010-0239. 

Please include a total of two copies. In addition, please 

mail a copy of your comments on the information collection 

provisions to the Office of Information and Regulatory 

Affairs, Office of Management and Budget (OMB), Attn: Desk 

Officer for EPA, 725 17th St., NW, Washington, DC 20503. 

• Hand Delivery or Courier: Deliver your comments to EPA 

Docket Center, Room 3334, 1301 Constitution Ave., NW, 

Washington, DC 20460. Such deliveries are only accepted 
3

during the Docket Center’s normal hours of operation, and 

special arrangements should be made for deliveries of boxed 

information. 

Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR2010-0239. EPA’s policy is that all comments received will be 

included in the public docket without change and may be made 

available online at www.regulations.gov, including any personal 

information provided, unless the comment includes information 

claimed to be confidential business information (CBI) or other 

information whose disclosure is restricted by statute. Do not 

submit information that you consider to be CBI or otherwise 

protected through www.regulations.gov or e-mail. The 

www.regulations.gov website is an “anonymous access” system, 

which means that EPA will not know your identity or contact 

information unless you provide it in the body of your comment. 

If you send an e-mail comment directly to EPA without going 

through www.regulations.gov, your e-mail address will be 

automatically captured and included as part of the comment that 

is placed in the public docket and will be made available on the 

Internet. If you submit an electronic comment, EPA recommends 

that you include your name and other contact information in the 

body of your comment and with any disk or CD-ROM you submit. If 

EPA cannot read your comment due to technical difficulties and 

cannot contact you for clarification, EPA may not be able to 
4

consider your comment. Electronic files should avoid the use of 

special characters, any form of encryption, and be free of any 

defects or viruses. 

Docket: All documents in the docket are listed in the 

www.regulations.gov index. Although listed in the index, some 

information is not publicly available (e.g., CBI or other 

information whose disclosure is restricted by statute). Certain 

other material, such as copyrighted material, will be publicly 

available only in hard copy form. Publicly available docket 

materials are available either electronically in 

www.regulations.gov or in hard copy at the EPA Docket Center, 

Public Reading Room, EPA West, Room 3334, 1301 Constitution 

Ave., NW, Washington, DC. The Public Reading Room is open from 

8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal 

holidays. The telephone number for the Public Reading Room is 

(202) 566-1744, and the telephone number for the Air Docket is 

(202) 566-1742. 

FOR FURTHER INFORMATION CONTACT: For questions about these 

proposed standards for gold mine ore processing and production, 

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. 
5

SUPPLEMENTARY INFORMATION: 

 The information presented in this preamble is organized as 

follows: 

I. General Information 

A. Does this action apply to me? 

B. What should I consider as I prepare my comments to EPA? 

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

D. When would a public hearing occur? 

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

III. Background Information 

A. What is the statutory authority and regulatory approach for 

the proposed standards? 

B. What source category is affected by the proposed NESHAP? 

C. What are the production operations, emission sources, and 

available controls? 

IV. Summary of the Proposed Standards 

A. Do these proposed standards apply to my facility? 

B. When must I comply with the proposed standards? 

C. What are the proposed standards? 

D. What are the testing and monitoring requirements? 

E. What are the notification, recordkeeping, and reporting 

requirements? 

F. What are the title V permit requirements? 

G. Emissions of non-mercury HAPs.

H. Request for comments.

V. Rationale for the Proposed Standards 

A. How did we select the affected source? 

B. How did we determine MACT? 

C. How did we select the testing, monitoring, and electronic 

reporting requirements? 

VI. Impacts of the Proposed Standards 

A. What are the emissions, cost, economic, and non-air 

environmental impacts? 

B. What are the health benefits of reducing mercury emissions? 

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 
6

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 Advancement Act 

J. Executive Order 12898: Federal Actions to Address 

Environmental Justice in Minority Populations and Low-Income 

Populations 

I. General Information 

A. Does this action apply to me? 

 The regulated categories and entities potentially affected 

by the proposed standards include: 

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 
7

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. What should I consider as I prepare my comments to EPA? 

 Do not submit CBI to EPA through www.regulations.gov or email. Send or deliver information identified as CBI only to the 

following address: Roberto Morales, OAQPS Document Control 

Officer (C404-02), Office of Air Quality Planning and Standards, 

Environmental Protection Agency, Research Triangle Park, NC 

27711, Attention: Docket ID No. EPA-HQ-OAR-2010-0239. Clearly 

mark the part or all of the information that you claim to be 

CBI. For CBI contained in a disk or CD-ROM that you mail to 

EPA, mark the outside of the disk or CD-ROM as CBI and then 

identify electronically within the disk or CD-ROM the specific 

information that is claimed as CBI. In addition to one complete 

version of the comment that includes information claimed as CBI, 

a copy of the comment that does not contain the information 

claimed as CBI must be submitted for inclusion in the public 

docket. Information so marked will not be disclosed except in 

accordance with procedures set forth in 40 CFR part 2. 

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

 In addition to being available in the docket, an electronic 

copy of this proposed action will also be available on the 

Worldwide Web (WWW) through the Technology Transfer Network 
8

(TTN). Following signature, a copy of the proposed 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. 

D. When would a public hearing occur? 

 If anyone contacts EPA requesting to speak at a public 

hearing concerning this proposed rule by [INSERT DATE 10 DAYS 

AFTER PUBLICATION IN THE FEDERAL REGISTER], a public hearing 

will be held on [INSERT DATE 15 DAYS AFTER PUBLICATION IN THE 

FEDERAL REGISTER]. If you are interested in attending the 

public hearing, contact Ms. Pamela Garrett, Metals and Minerals 

Group (D243-02), Sector Policies and Programs Division, U.S. 

EPA, Research Triangle Park, NC 27711, telephone (919) 541-7966 

email address: garrett.pamela@epa.gov to verify that a hearing 

will be held. If a public hearing is held, it will be held at 

EPA’s campus located at 109 T.W. Alexander Drive in Research 

Triangle Park, NC, or an alternate site. If a hearing is 

requested by [INSERT DATE 10 DAYS AFTER PUBLICATION IN THE 

FEDERAL REGISTER], any persons interested in presenting oral 

testimony at that hearing should contact Ms. Pamela Garrett at 

least 2 days in advance of the date of the public hearing. 

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

 Section 112(c)(6) of the CAA requires that EPA list 
9

categories and subcategories of sources assuring that sources 

accounting for not less than 90 percent of the aggregate 

emissions of each of the seven specified Hazardous Air 

Pollutants (HAP) are subject to standards under section 

112(d)(2) or (d)(4). The seven HAP specified in section 

112(c)(6) are as follows: alkylated lead compounds, polycyclic 

organic matter, hexachlorobenzene, mercury, polychlorinated 

biphenyls, 2,3,7,9-tetrachlorodibenzofurans, and 2,3,7,8-

tetrachloridibenzo-p-dioxin. 

 In 1998, EPA published a list of section 112(c)(6) 

categories (63 FR 17838, April 10, 1998). At that time, there 

was very little available information on mercury emissions from 

gold mine ore production and processing. Since the 1998 notice, 

a substantial amount of data and information have become 

available on mercury emissions from this source category. For 

example, in 2000, the first estimates of mercury emissions from 

this source category were published in the Toxics Release 

Inventory (TRI), largely because of the lower TRI reporting 

threshold for mercury that went into effect about that time. 

Following this, from 2001 to 2005, additional data and 

information were collected through the Voluntary Mercury 

Reduction Program (VMRP), which was a collaborative agreement 

between the State of Nevada Division of Environmental Protection 

(NDEP), EPA’s Region 9 Office, and four gold mining companies. 
10

Then, in 2005-2006 the EPA’s Office of Air Quality Planning and 

Standards (OAQPS) and the NDEP sent questionnaires to a number 

of companies seeking additional information and data on mercury 

emissions. Moreover, starting in 2007 the NDEP has been 

requiring all facilities in Nevada to conduct annual mercury 

emissions tests. Based on these data collected over the past 

several years, along with information about the industry 

processing and production levels and activities in the early 

1990s, EPA has estimated that the gold mine ore processing and 

production emitted about 4.4 tons of mercury during the baseline 

year (i.e., in 1990). These estimated mercury emissions in the 

1990 inventory for gold mine ore processing and production are 

based on emissions from the following thermal processes at gold 

mine ore processing and production facilities: roasters, 

autoclaves, carbon kilns, pregnant storage solution tanks (“preg 

tanks”), electrowinning, melt furnaces, and retorts. We have 

updated our 1990 baseline emission inventory for section 

112(c)(6) to reflect this contribution of mercury from gold mine 

ore processing and production and determined that this area 

source category contributed to the 90 percent of the aggregate 

emissions of mercury in 1990. Consequently, we are adding gold 

mine ore processing and production area source category to the 

list of source categories under section 112(c)(6) on the basis 

of mercury emissions. 
11

III. Background Information 

A. What is the statutory authority and regulatory approach for 

the proposed standards? 

 As mentioned above, CAA section 112(c)(6) requires that EPA 

set standards under section 112(d)(2) or (d)(4). The mercury 

standards for the gold mine ore processing and production area 

source category are being established under CAA section 

112(d)(2), which require MACT level of control. Under CAA 

section 112(d), the MACT standards for existing sources must be 

at least as stringent as the average emissions limitation 

achieved by the best performing 12 percent of existing sources 

(for which the administrator has emissions information) for 

source categories and subcategories with 30 or more sources, or 

the best performing 5 sources for categories and subcategories 

with fewer than 30 sources (CAA section 112(d)(3)(A) and (B)). 

This level of minimum stringency is called the MACT floor. For 

new sources, MACT standards must be at least as stringent as the 

emission control that is achieved in practice by the best 

controlled similar source (CAA section 112(d)(3)). EPA also 

must consider more stringent ”beyond-the-floor” control options. 

When considering beyond-the-floor options, EPA must consider not 

only the maximum degree of reduction in emissions of HAP, but 

must take into account costs, energy, and nonair quality health 

and environmental impacts when doing so. 
12

B. What source category is affected by the proposed NESHAP?

 The gold mine ore processing and production area source 

category consists of facilities engaged in processing gold ore 

to recover gold using one or more of the following process 

units: roasters, autoclaves, carbon kilns, melt furnaces, 

mercury retorts, electrowinning, and/or pregnant solution tanks. 

There were approximately 21 gold mine ore processing and 

production facilities operating these processes in the United 

States in 2008. The majority and the largest of these 

facilities are located in Nevada. The other facilities 

currently operating are in Alaska, California, Colorado, 

Montana, and Washington. In 2007, the U.S. gold mine industry 

produced about 240 metric tons of gold, and the value of gold 

mine production was about $5.1 billion. 

C. What are the production operations, mercury emission 

sources, and available controls?

 All gold mine operations in the U.S. begin by mining ores, 

generally using large earth moving equipment. The ore is then 

subject to crushing operations. After crushing, some ore may be 

pre-treated by roasting or autoclaving. Subsequent to these 

operations the ore undergoes some type of leaching process using 

a dilute cyanide solution. The cyanide binds with the gold (and 

various impurities including mercury) to produce a “pregnant” 

solution. The pregnant solutions are further processed using 
13

various thermal processes (e.g., electrowinning, retorts and 

furnaces) to recover gold. The gold mine ore processing and 

production area source category covers the thermal processes 

that occur after the crushing, including roasting operations 

(i.e., ore dry grinding, ore preheating, roasting, and 

quenching), autoclaves, carbon kilns, electrowinning, preg 

tanks, retorts and furnaces. Further details of the gold 

production processes are described in section C.2 below. 

1. Historical Background on Mercury Emissions 

 Mercury, which is naturally present in the ores in various 

concentrations, enters the gold recovery processes with the gold 

mine ore. Most of this mercury is recovered as a by-product in 

the form of liquid elemental mercury, or as a mercury 

precipitate, placed in closed containers, and stored or sold to 

commercial metal companies. In addition, a notable amount of 

mercury is currently captured by mercury emission control 

devices (e.g., in carbon media) and is not recovered for sale. 

Nevertheless, some portion of the mercury in the ore is 

liberated to the air during the thermal processes resulting in 

mercury emissions to the atmosphere. Without emissions controls 

the potential for mercury emissions from these facilities would 

be quite high. 

 In May 2000, EPA published the first estimates of mercury 

emissions for gold mine ore processing and production facilities 
14

as part of the EPA’s TRI for year 1998. Total mercury air 

emissions reported to the TRI in the 1998-2001 timeframe for 

this source category were about 14,000 pounds per year. 

However, EPA estimated (in the 1999 National Emissions 

Inventory) that total mercury emissions from this category were 

higher (about 23,000 pounds in 1999), and the mining industry 

reported emissions to be 21,000 pounds in 2001. Even at that 

time, some facilities had controls on processes to limit mercury 

emissions. Early efforts to reduce or limit mercury emissions 

were due in part to concerns about worker exposure to mercury. 

For example, for years facilities that were processing ores with 

higher levels of mercury have been using retorts to condense and 

capture the mercury in liquid elemental form. Moreover, two of 

the largest facilities have been using mercury specific 

emissions controls on their roasters since the mid-1990s. Also, 

a number of facilities had carbon adsorption beds to control 

mercury emissions on various thermal process units prior to 

2001. We estimate that without these early controls the 

potential emissions would have been much higher than 23,000 

pounds (at least 37,000 pounds). 

 Since 2001, mercury emissions from gold mine ore processing 

and production have been further reduced. The reductions 

achieved since 2001 were obtained through programs implemented 

by the NDEP, EPA, and industry. The first program for reducing 
15

mercury emissions from these facilities was the Voluntary 

Mercury Reduction Program (VMRP). The VMRP was a voluntary 

partnership between the NDEP, EPA Region 9, and four large gold 

mining companies. The main goal of the VMRP, which was 

officially adopted in June 2002, was to achieve significant, 

permanent and rapid reductions in mercury air emissions from 

precious metal processing operations. The VMRP focused on 5 

large facilities in Nevada that accounted for most of the 

reported emissions in 2001. Some mercury emission reductions 

were quickly achieved by adding emission controls to some of the 

thermal units that emit mercury at these facilities. 

 To achieve further reductions in mercury emissions, the 

NDEP converted the VMRP into a regulatory program, called the 

Nevada Mercury Control Program (NMCP). As described on the NDEP 

website, the NMCP is a State regulatory program that supersedes 

and replaces the VMRP and requires best available mercury 

emissions control technology on all thermal units located at all 

precious metal mines in Nevada. The NMCP was adopted March 8, 

2006 and made effective May 4, 2006. The NMCP is a case-by-case 

permit program in 2 phases. The NMCP also had an early 

reduction program, which provided incentives for facilities to 

add controls within the first 2 years of the program (by mid2008). A few facilities in Nevada took advantage of the early 

reduction program and added mercury specific controls (sulfur 
16

impregnated carbon filters) in 2007 on various thermal units. 

 In Phase 1 of the NMCP, which has recently been completed, 

permits were issued that require comprehensive work practice 

standards for the proper operation of existing mercury controls 

and the operations of the thermal units to minimize mercury 

emissions until specific controls are identified later under 

Phase 2 of the program. Phase 1 also required annual stack 

testing, site inspections and emissions reporting to collect 

data to assist in mercury emissions controls determinations in 

Phase 2. Emissions data collected in Phase 1 of the NMCP were 

used in the development of this proposed rule. Phase 2 has 

begun issuing permits and all permits are scheduled for issuance 

by the end of calendar year 2010. Implementation of controls 

will begin shortly after permit issuance. The Phase 2 permit 

process is a technology review and engineering analysis to 

determine the best available control technology and mercury 

emission limits. Controls and mercury emissions limits will be 

determined on a case-by-case analysis and will be unique to the 

individual unit (not universal for the unit type). The NMCP is 

a control-based program that will require thermal units in 

Nevada to have a best available mercury control technology 

installed. The NDEP and EPA have coordinated on the review and 

analyses of data on emissions, controls, and monitoring 

approaches for mercury emissions from this category, and 
17

collaborated to assure that the State program could co-exist and 

provide an additional level of control for facilities in Nevada 

while working in concert with the proposed National standards. 

 As described further below, several facilities already have 

effective mercury emissions controls in place on various thermal 

units. We expect that a number of other facilities will need to 

add mercury controls to comply with emissions limits set forth 

in this NESHAP, resulting in further emissions reductions from 

this category. 

2. Description of Gold Mine Ore Processing and Production 

 The gold mine ore processing and production source category 

consists of the following processes: roasting operations, 

autoclaves, carbon regeneration kilns, electrowinning cells, 

pregnant solution tanks, mercury retorts, and melt furnaces. 

Each facility may not have every one of these processes because 

there are different production paths that can be taken to 

recover gold from mine ore. Mercury can be emitted from each of 

these thermal processes. Some of these processes are already 

well controlled for mercury emissions; however, there are some 

process units at several plants that are only partly controlled 

or uncontrolled for mercury. 

 The first step in gold mining is extracting the goldcontaining ores from surface or undergrounds mines, generally by 

using large-scale earthmoving equipment. Samples of ore are 
18

examined to determine grade and metallurgical characteristics. 

Broken rock is marked by type for efficient processing. Based 

on its metallurgical makeup, the ore is delivered to the proper 

processing location. Low grade ore is roughly broken into small 

chunks, and high grade ore is delivered to a grinding mill, 

where the ore is pulverized to a powder (milled ore). 

 Depending on its metallurgical and other characteristics, 

the ore may be pretreated in a roaster or autoclave prior to 

leaching, or it may be sent directly to a leaching circuit 

without pretreatment. The two main types of ore are oxide ore 

and refractory ore. If the process of cyanide leaching can 

extract most of the gold contained in an ore with no 

pretreatment, the ore is referred to as oxide ore, and if not, 

the ore is described as refractory ore. Oxide ore is sent 

directly to the leaching circuit where cyanide is used to 

liberate the gold. However, refractory ores contain organic 

carbon and/or sulfide mineral grains which inhibit the efficient 

recovery of gold during cyanide leaching. Roasters and 

autoclaves are used to oxidize the ore and remove these 

components. Refractory ore containing carbon and sulfur is 

roasted to over 1000oF, burning off the sulfide and carbon. The 

product of this process, which is now basically an oxide ore, is 

routed to a leaching circuit. Sulfide refractory ore without 

carbon is oxidized in an autoclave to liberate the gold from 
19

sulfide minerals, then it is sent to a leaching circuit. At all 

facilities, the ores are eventually sent to some type of cyanide 

leaching process. 

 Lower grade oxide ores generally undergo a heap leaching 

process, whereby the ore is spread over large areas and dilute 

cyanide solution is slowly dripped through and collected on 

liners and channels. During the leaching process, cyanide binds 

with gold and other elements (including mercury) producing a 

“pregnant” cyanide solution. At most facilities that use this 

process, the next step involves pumping the pregnant cyanidegold solution to tanks with activated carbon where the gold is 

adsorbed (collected) out of solution onto the activated carbon, 

and the remaining cyanide solution is largely recycled. This 

carbon adsorption step that follows the cyanide leaching is 

generally referred to as the “carbon-in-pulp” process. 

 Higher grade ores are generally milled. If the ore is a 

higher grade “oxide ore”, it is milled and then generally sent 

directly to carbon-in-leach processes where activated carbon is 

added along with the milled ore and cyanide solution in tanks 

where the cyanide-gold complexes adsorb onto activated carbon. 

In these units the leaching and carbon adsorption occur 

together. If the higher grade ore is a refractory ore, it is 

roasted or autoclaved first, then it is sent to carbon-in-leach 

processes. 
20

 However, a few facilities do not use carbon. Instead, 

these facilities use a different, zinc precipitate process, 

which is described later in this preamble. 

 At all the facilities that use a carbon adsorption process, 

the gold loaded carbon (which also contains mercury and other 

constituents) is moved into a vessel where the gold is 

chemically stripped from the carbon typically by using a 

concentrated caustic cyanide solution, producing a concentrated 

cyanide-gold solution. Gold (along with other metals and 

minerals) is drawn from this concentrated solution 

electrolytically (in electrowinning cells). The concentrate 

from the electrowinning cells is usually sent to a filter press 

to remove excess moisture and then to a retort followed by a 

melt furnace. However, some facilities do not have retorts. 

These facilities dry the concentrate and then feed it directly 

to the melt furnace. Either way, the gold is melted in 

furnaces into dore (pronounced “doh-rey”) bars containing up to 

90 percent gold. Dore bars are subsequently sent to an external 

refinery to be refined to bars of 99.9 percent or more pure 

gold. The processing steps are discussed in more detail below. 

For processing steps that emit mercury, the discussion below 

also describes the points of mercury emissions and available 

controls for such emissions. 

3. Pretreatment of Refractory Ore. 
21

 As mentioned above, refractory ores have to be pretreated 

by furnace oxidation (ore roasting) and/or pressure oxidation 

(autoclaving) before they can be ready for cyanide leaching. 

 Roasting Operations. The roasting operations that are 

sources of mercury emissions include ore dry grinding where the 

ore is ground and dried, preheating prior to roasting, roasting, 

and quenching. The roaster is by far the process unit with the 

greatest potential for mercury emissions because of the large 

quantity of ore processed and the high roasting temperatures, 

which readily volatilize available mercury from the ore. The 

mercury concentrations in the roasted ores are high enough that 

elemental mercury can be recovered from the roaster exhaust gas 

by condensation. The emission potential of the ancillary 

roasting operations (dry grinding, pre-heating and quenching) 

are much less than those from the roaster because they are 

operated at much lower temperatures. Dry grinding of the ore 

prior to roasting is primarily a source of particulate matter 

(PM) emissions; consequently, baghouses are used for PM emission 

control. Ore preheaters used to raise the ore temperature to 

facilitate roasting are typically equipped with baghouses or wet 

scrubbers, which control particulate and some oxidized mercury. 

Emissions from quenching (when the roasted ore is cooled) are 

controlled by wet scrubbers, which remove particulate and some 

oxidized mercury. 
22

 Ore roasting is a combustion process where the milled ore 

is oxidized in a fluidized bed roaster. During the combustion 

process, ore components that interfere with the cyanide leaching 

of gold are oxidized and therefore removed. As the ore exits 

the combustion chamber, it typically enters a quench process, 

where the temperature is reduced by contact with cooling water 

and the generation of steam. The steam from the quench process 

is used as a heat source in other processes at the mill, or may 

be sent directly to a cooling tower. 

 There are three gold mine ore processing and production 

facilities that have a total of six roasters. The mercury 

emissions generated during roasting are mainly in gaseous 

elemental or oxidized forms of mercury. A very small portion of 

the mercury emitted is in particulate or particulate-bound form. 

Each of these roasters has complex gas treatment systems to 

control not only these forms of mercury, but also to control PM, 

sulfur dioxide (SO2), nitrogen oxides (NOx), and carbon monoxide 

(CO). The PM control devices remove particulate mercury and 

some oxidized mercury. A significant amount of the elemental 

mercury is removed and recovered by condensation (either in a 

condenser or gas cooling device), and the three facilities with 

roasters use mercuric chloride scrubbers. These scrubbers use a 

mercuric chloride scrubber liquor to complex with mercury in the 

exhaust gas to precipitate a mercurous chloride byproduct 
23

(calomel). These scrubbers are also referred to as “calomel 

scrubbers.” The calomel precipitate is subsequently removed and 

is either sent to electrowinning to recover the mercury, 

disposed of offsite as a waste material, or a portion may be 

chlorinated to create fresh mercuric chloride for the calomel 

scrubber liquor. An example of the emissions controls and gas 

treatment train for a roaster includes a hot gas electrostatic 

precipitator (ESP), wash tower, gas coolers, fluorine tower, wet 

ESP, calomel scrubber, acid plant (for removal of SO2 and 

conversion to sulfuric acid product), peroxide scrubber (to 

control NOx), and regenerative thermal oxidizer (for CO). 

 Autoclaves. Autoclaves are pressure oxidation vessels that 

are used to pretreat ores to increase gold recovery by cyanide 

leaching. The milled ore is mixed with water to form a slurry, 

and is then acidified with sulfuric acid. The acidified slurry 

is then pumped into the autoclave vessel, where oxygen is used 

to increase the vessel pressure to over 300 pounds per square 

inch, and the slurry is heated to 350oF to 430oF. The slurry is 

agitated in the reaction vessel and is then discharged to a 

pressure relief chamber. There the liquid content is flashed to 

steam, recovered, and returned to the pressurized segment of the 

vessel. 

 Most mercury is present in the gold ore as mercury sulfide, 

and during autoclaving, the mercury sulfide combines with oxygen 
24

to form mercury sulfate, which dissociates to some degree in the 

slurry. Consequently, the mercury present in gaseous emissions 

from the autoclave is mainly in the oxidized form. 

 Three facilities have a total of eight autoclaves. All of 

the autoclaves are equipped with wet venturi scrubbers, which 

remove most of the particulate mercury and a significant portion 

of the oxidized mercury present in the emissions. Venturi 

scrubbers have a specially designed “throat” that increases the 

gas speed through the throat and shears spray droplets to 

smaller sizes, which enhances mixing of the droplets and 

particles and increases coagulation and collection. 

4. Leaching 

 As mentioned above, leaching generally takes place either 

directly after crushing or milling, or after roasting or 

autoclaving. In heap leaching, a dilute alkaline cyanide 

solution is distributed onto crushed ore. The solution 

percolates through the ore, and the gold reacts with free 

cyanide to form soluble gold-cyanide complexes. The complexes 

migrate with the solution to an impermeable liner and flow to a 

collection pond. 

 The solution containing the precious metals is called the 

“pregnant” cyanide solution. During this process, mercury, also 

present in the ore, may be leached into the gold-cyanide 

solution. 
25

 Refractory ores, which have been roasted or autoclaved, are 

generally leached in reaction vessels, referred to as vat 

leaching. Activated carbon adsorbent is usually added to the 

leach vessels to improve gold recovery. All five facilities in 

the U.S. that employ roasters and/or autoclaves add activated 

carbon to these leach vessels, where the leaching and carbon 

adsorption occur simultaneously in the tank. This is called the 

“carbon-in-leach” process. 

5. Carbon Adsorption Process 

 As mentioned above, after leaching, the most common path 

for recovering gold from the cyanide solution is carbon 

adsorption, where the gold complexes in the pregnant solution 

are concentrated through adsorption onto activated carbon. If 

mercury is present in the gold-cyanide solution, it is also 

adsorbed onto the carbon. The gold-bearing solution may be 

extracted from the leaching process and subsequently introduced 

into a carbon adsorption column for concentration of the gold 

content (i.e., the carbon-in-pulp process), or carbon may be 

added into the leach process concurrent with leaching from the 

ore (i.e., the carbon–in-leach process). All of these carbon 

adsorption processes produce a “loaded” carbon, which contains 

gold and mercury (and some other metals such as copper) as 

adsorbed cyanide complexes. 

6. Carbon Desorption Processes 
26

 The loaded carbon is then separated from the rest of the 

solution or slurry by physical separation processes (such as 

with a screen). The remaining cyanide solution is now 

considered “barren” and can either be recycled back to the 

barren pond for use in the heap leaching process, sent directly 

to the tailings impoundment (if the cyanide concentrations are 

low), or sent to a cyanide destruction process and then to a 

tailings impoundment once the cyanide levels are sufficiently 

low. 

 The loaded carbon, which contains gold-cyanide complexes, 

mercury, and other metals, is stripped in a carbon strip tank to 

recover gold (and other metals) typically using a heated caustic 

cyanide solution. Adsorbed gold, as well as adsorbed silver, 

mercury, and other metals are stripped from the carbon through 

desorption under pressurized or atmospheric conditions, 

resulting in a more concentrated gold-containing solution. 

7. Description of thermal units used after carbon desorption. 

 Carbon kilns. After gold has been removed from the 

activated carbon through the stripping process, the carbon is 

usually regenerated and then recycled back to the adsorption 

process. Regeneration is performed to regain the adsorption 

capacity of the carbon. Rotary kilns known as carbon kilns are 

used to regenerate the spent carbon. Because the carbon can be 

oxidized in the kiln if air is present in the heating chamber, 
27

steam is introduced to the kiln to prevent the infiltration of 

air. As the carbon moves through the carbon kiln, it is heated, 

and mercury and other remaining components are desorbed into the 

gas stream in the kiln. Regenerated carbon exits the kiln and 

is captured and quenched, and the gas stream is vented from the 

process, along with combustion gas from heating the kiln 

chamber. The off-gas, containing steam and mercury, is 

discharged to a pollution control device, such as a carbon 

adsorber. The potential for mercury emissions from carbon kilns 

is directly dependent on the mercury content of the stripped 

carbon and whether there is a carbon adsorber or other device to 

control mercury emissions. 

 There are approximately 16 facilities with 18 carbon kilns. 

Most of these carbon kilns have installed carbon adsorption 

units to control mercury emissions, and some other facilities in 

Nevada have proposed in their state permit applications under 

the NMCP to install carbon adsorbers on their carbon kilns. One 

facility uses a hypochlorite scrubber on its carbon kiln which 

oxidizes the elemental mercury to a more soluble form and 

removes it as mercuric chloride. 

 Pregnant storage solution tanks (“preg tanks”). The 

concentrated gold-containing solution that was stripped from the 

carbon is transferred to a preg tank, which serves as a storage 

and feed tank to the electrowinning process (discussed below). 
28

The concentrated solution also contains mercury, and mercury 

vapor can be emitted from the preg tank vent. Two facilities 

have installed carbon adsorbers on their preg tanks. In 

addition, five facilities in Nevada have proposed in their state 

permit applications under the NMCP to install carbon adsorbers 

on their preg tanks. 

 Electrowinning cells. Recovery of gold, along with coprecipitated metals such as silver and mercury, from 

concentrated carbon strip solutions is performed in one of two 

ways: electrowinning (the most common process) or precipitation 

with zinc powder (discussed below). Separation of gold through 

electrowinning is achieved by using an electric potential to 

plate the gold (and other metals present) in solution onto a 

cathode; steel wool is typically used as the plating surface 

because of the large surface area it provides for gold 

deposition. The plated cathode, or sponge, is then either 

removed from the electrowinning cell, so that the gold-bearing 

sludge-like material can be removed from the plated cathode, or 

the plated cathode can be left in the electrowinning (EW) cell, 

but the current is turned off and the remaining solution is 

drained out, then the material is removed from the plated 

cathode. Either way, once the current has stopped, the goldbearing sludge-like material (known as “EW concentrate”) is 

separated from the cathode by physical means (such as shaking). 
29

The gold-bearing EW concentrate is then ready for further 

processing. During electrowinning, elemental mercury can 

vaporize and escape from the cell with the other gases produced 

in the process; carbon adsorption filters are effective in 

controlling these mercury emissions. 

 There are approximately 17 electrowinning units located at 

14 plants. Five facilities have installed carbon adsorbers to 

control mercury emissions from electrowinning. In addition, 

four facilities in Nevada have proposed in their State permit 

applications under the NMCP to install carbon adsorbers on their 

electrowinning units. 

 Retorts. The EW concentrate may contain up to sixty weight 

percent gold, depending on the mercury content of the cyanide 

solution, the presence of other metals and minerals in the 

material, and the configuration of the gold recovery process. 

EW concentrate with significant mercury content is treated in a 

retort to remove mercury moisture and other impurities. In this 

process, the EW concentrate is placed in a pot or tray that is 

loaded into a heated oven under vacuum pressure, usually for 12 

to 24 hours at 600°C to 700°C to remove up to 99 percent of the 

mercury. The EW concentrate is heated, mercury is vaporized and 

then pulled through a condenser where it condenses forming 

liquid mercury. The liquid mercury is recovered and sent 

through a tube into a collection vessel. The remaining gold and 
30

silver at the end of the retorting process typically contains 

less than 1 percent mercury (e.g., 1,000 to 8,000 mg/kg). The 

condenser allows some mercury to discharge in the off gas, and a 

loss of 0.4 to 0.7 percent of the mercury from the condenser has 

been reported. All facilities that have retorts operate the 

retort with a condenser and a carbon adsorption filter. A 

properly designed and maintained carbon adsorption filter 

located downstream of the condenser is expected to capture about 

95 percent of the mercury in the cooled gas. 

 There are approximately 12 facilities that operate retorts, 

and all have carbon adsorbers to control mercury emissions from 

the condensers. 

 Melt furnaces. Smelting is the last step in gold mine ore 

processing and production before the gold is sent to an off-site 

commercial gold refinery. Even after retorting, the retorted 

gold mixture still contains some impurities, including small 

concentrations of base and ferrous metals, and some residual 

mercury. During this last step, the retorted gold mixture (or 

EW concentrate for facilities that do not have retorts) is 

melted in a refinery melt furnace, along with a flux material 

that preferentially absorbs impurities, to produce a purified 

commercial mixture of gold known as dore. The furnace is heated 

to approximately 1500°C. Most of the remaining mercury is 

volatilized in the melt furnace as elemental mercury or oxidized 
31

mercury. The dore melt is poured into bars, and any flux slag 

that hardens on the bars is removed with a mechanical chipper. 

The bars are then shipped to a commercial gold refinery, where 

they are further processed to produce gold bullion (99.9 percent 

pure gold). 

 There are approximately 24 melt furnaces at 17 gold mine 

ore processing and production facilities. All of the melt 

furnaces are equipped with either fabric filters, ESPs, wet 

scrubbers, or a combination thereof to control emissions of PM. 

The wet scrubbers also remove most of the oxidized mercury, but 

do not remove elemental mercury. Six facilities have installed 

carbon adsorbers to control both oxidized and elemental mercury 

emissions from their melt furnaces. In addition, three 

facilities in Nevada have proposed in their state permit 

applications under NMCP to install carbon adsorbers on their 

melt furnaces. 

8. Non-carbon concentrate process 

 After leaching, four facilities recover the gold from the 

cyanide solution without using carbon by a process commonly 

known as the Merrill-Crowe (MC) method. The cyanide solution 

containing gold is separated from the ore by methods such as 

filtration and counter current decantation and clarified in 

special filters, usually coated with diatomaceous earth to 

produce a clarified solution. Zinc dust is then added to the 
32

clarified solution. Because zinc has a higher affinity for 

cyanide ions than does gold or other metals, zinc is dissolved 

and gold, silver, and mercury precipitate as a solid. The fine 

particulate metals are recovered by filtration processes. This 

process is performed in deoxygenated, enclosed reaction cells. 

 The precipitate (also known as MC concentrate) is processed 

in retorts and melt furnaces, which are described above. The 

retorts and melt furnaces are the sources of mercury emissions 

at facilities that use non-carbon concentrate processes, and 

these processes are equipped with carbon adsorbers or venturi 

scrubbers to control mercury emissions. These facilities do not 

have carbon kilns since they do not use carbon. 

IV. Summary of the Proposed Standards 

A. Do these proposed standards apply to my facility?

 These proposed mercury standards would apply to gold mine 

ore processing and production facilities that are area sources 

that use any of the following thermal processes: roasting 

operations, autoclaves, carbon kilns, preg tanks, 

electrowinning, retorts, and melt furnaces. Separate mercury 

6standards are proposed for each of the following three affected 

sources: (1) ore pretreatment processes (roasting operations 

and autoclaves), (2) carbon processes (carbon kilns, preg tanks, 

electrowinning, retorts, and melt furnaces at facilities that 

use carbon to recover the gold from the cyanide solution), and 
33

(3) non-carbon concentrate processes (retorts and melt furnaces 

at facilities that do not use carbon to recover gold). 

 We are proposing standards for both new and existing 

affected sources. An affected source is an existing source if 

construction or reconstruction commenced on or before [INSERT 

DATE OF PUBLICATION OF THIS PROPOSED RULE IN THE FEDERAL 

REGISTER]. An affected source is a new source if construction 

or reconstruction commenced after [INSERT DATE OF PUBLICATION OF 

THIS PROPOSED RULE IN THE FEDERAL REGISTER]. 

B. When must I comply with the proposed standards?

 We are proposing that the owner or operator of an existing 

affected source comply with the final rule no later than 2 years 

after publication of that rule in the Federal Register. The 

owner or operator of a new affected source is required to comply 

by the date of publication of the final rule in the Federal 

Register or upon startup of the affected source, whichever 

occurs later. 

C. What are the proposed standards?

We are soliciting comments on all aspects of this proposed 

rule including, but not limited to, the data and calculations 

used to establish the emissions limits, the proposed testing and 

monitoring for emissions, and the parametric monitoring of 

control devices. 

The proposed standards are summarized in Table 1 of this 
34

preamble and discussed in more detail below. These proposed 

standards establish mercury MACT emission limits for three 

affected sources. The proposed MACT standard for new and 

existing ore pretreatment processes is 149 pounds of mercury per 

million tons of ore processed (149 lb/million tons). The 

proposed MACT standard for existing carbon processes is 2.6 

pounds of mercury per ton of concentrate processed (2.6 lb/ton 

of concentrate), and for new carbon processes is 0.14 pounds of 

mercury per ton of concentrate (0.14 lb/ton of concentrate). 

Concentrate is the gold-bearing sludge material that is 

processed in retorts. For facilities without retorts, 

concentrate is the quantity processed in melt furnaces before 

any drying. For new carbon processes, we are proposing a 

compliance alternative of 97 percent control efficiency. This 

alternative provides at least equivalent HAP reductions as the 

MACT floor. 

Table 1. Summary of Proposed Mercury Emission Limits

Affected source Mercury emission limit

Existing source New source

Ore pretreatment 

processes

149 lb/ton of ore 149 lb/ton of ore

Carbon processes 2.6 lb/ton of 

concentrate

0.14 lb/ton of 

concentrate or 97 

percent reduction in 

uncontrolled emissions

Non-carbon 

concentrate processes

0.25 lb/ton of 

concentrate

0.20 lb/ton of 

concentrate

 The proposed MACT standard for existing non-carbon 
35

concentrate processes is 0.25 pounds of mercury per ton of 

concentrate processed (0.25 lb/ton of concentrate processed), 

and for new non-carbon concentrate processes is 0.20 lb/ton of 

concentrate processed. 

D. What are the testing and monitoring requirements?

1. Testing for Compliance with Emission Limits 

 Any stack that is a discharge point for any thermal process 

at a gold mine ore processing and production facility would be 

tested for mercury emissions based on the average of a minimum 

of three runs per stack at least once annually (i.e., once every 

four successive calendar quarters) using EPA Method 29 in 

Appendix A-8 to part 60, the Ontario Hydro Method (ASTM D6784 – 

02, “Standard Test Method for Elemental, Oxidized, ParticleBound and Total Mercury in Flue Gas Generated from Coal-Fired 

Stationary Sources”), EPA Method 30A, or EPA Method 30B, both in 

Appendix A-8 to part 60. 

 We are proposing that the initial compliance test for new 

sources be conducted within 180 days of the compliance date. 

The emissions for each process stack (in lb/hr) would be 

multiplied by the number of hours the process operated in the 6-

month period following the compliance date to determine the 

total mercury emissions for the initial 6-month period. The 

process inputs used in the denominator of the emission limit, 

including ore and concentrate, would be measured and summed for 
36

each month to provide the total input (in tons) for the initial 

6-month period following the compliance date. The emissions (in 

lbs) for the 6-month period would be divided by the input for 

the 6-month period to determine compliance with the emission 

limit. After the initial 6-month period, all the stacks for the 

thermal process units would be tested for mercury emissions 

annually. 

 We are proposing that existing sources also conduct their 

initial compliance test within 180 days of their compliance 

date. The emissions for each process stack (in lb/hr) would be 

multiplied by the number of hours the process operated in the 6-

month period following the initial compliance date to determine 

the emissions for the 6-month period. The emissions for each 

process stack would be recorded in total pounds of mercury for 

the 6-month period. The total mercury emissions for the 

affected source for the 6 months would be determined by summing 

the emissions for each process stack included in the affected 

source. The total emissions for the 6-month period for the 

affected source would be divided by the process input 

(concentrate or ore) for the 6-month period to determine 

compliance with the emission limit. 

 After the initial 6-month period, all of the stacks for the 

thermal process units at new and existing sources would be 

tested for mercury emissions annually. The total mercury 
37

emissions and process inputs for each 12 month period would be 

calculated as described below to determine compliance with the 

emissions limit. 

 The process inputs used in the denominator of the emission 

limit, including ore and concentrate, would be measured and 

summed to provide the total input (in tons) for each month. For 

facilities with ore pretreatment processes, the daily quantity 

of ore (in tons) would be determined either by calibrated weigh 

scales or by measuring volumetric flow rate and density and 

multiplying the two measurements. The daily totals would be 

summed for each calendar month to provide a monthly total for 

ore input. For facilities with carbon and/or non-carbon 

processes affected sources, each batch of concentrate would be 

weighed by scales, and the total of all batches would be summed 

for each calendar month to produce monthly weights of 

concentrate. 

 Emissions in lb/million tons of ore for each affected 

source of ore pretreatment processes would be determined by 

summing the emissions for all units in the pre-treatment 

processes affected source for the appropriate time period (e.g., 

a 6-month period initially for new and existing sources and the 

12-month periods thereafter) and dividing this sum of the 

emissions by the sum of the total ore processed (expressed in 

millions tons) in all processes at the affected source for the 
38

appropriate time period (i.e., 6 months or 12 months). 

Emissions in lb/ton of concentrate for each affected source of 

carbon processes would be determined by dividing the sum of the 

emissions from all carbon processes at the affected source for 

the appropriate time period by the sum of the tons of 

concentrate processed at the affected source for each time 

period. Emissions in lb/ton of concentrate for each non-carbon 

concentrate process affected source would be determined by 

dividing the sum of the emissions from all non-carbon 

concentrate processes at the affected source for each 

appropriate time period by the sum of the concentrate (expressed 

in tons) processed in all processes at the affected source for 

each time period. 

 Mercury testing at both the inlet and outlet of all mercury 

emissions control devices is proposed for new affected sources 

with carbon processes that choose to demonstrate a 97 percent 

reduction in emissions. The inlet and outlet of every process 

unit’s control device would be sampled, and the mercury 

emissions before and after control (in lb/hr) would be 

multiplied by each process unit’s operating hours for the 

appropriate time period to determine the mercury emissions for 

the time period. The initial tests would be done within 180 

days of the compliance date. For the first 6 months of 

operation, the inlet emissions for all process units would be 
39

calculated and summed and compared to the sum of the calculated 

outlet emissions for the 6-month period. After the initial 6 

months, annual tests would be conducted and the calculations 

would be based on each 12 month period to determine the percent 

reduction in mercury emissions. 

We have also considered other procedures for calculating 

the mercury emission rate in pounds per ton of input to 

determine compliance for the ore pretreatment group and possibly 

for the carbon and non-carbon affected sources as well. For 

example, one approach for the ore pre-treatment processes would 

be to divide the measured emission rate (in pounds per hour) 

from the compliance test for each autoclave and roasting 

operation by the ore throughput (in tons per hour) for each 

autoclave and roasting operation as measured during the 

performance tests. The result would be emissions in pounds per 

ton of ore for each autoclave and roasting operation. Then the 

fraction of the total ore processed in the previous 12 months 

would be calculated for each roasting operation and autoclave, 

and the emissions from all autoclaves and roasting operations in 

the group would be calculated as the weighted average pounds per 

ton of ore to determine compliance (i.e., the sum of fraction of 

total ore throughput times the pounds per ton for each roasting 

operation and autoclave). With this approach, it would not be 

necessary to monitor, record, and use the annual operating hours 
40

for each unit to calculate emissions. A similar approach could 

possibly also be used for the carbon and non-carbon groups. We 

are requesting comment and supporting information on the 

advantages and disadvantages of this possible alternative 

procedure and the proposed procedure for determining compliance 

from the ore pretreatment group and the other process groups. 

2. Monitoring Requirements 

Roasters. We are proposing two options for monitoring 

roaster emissions: (1) integrated sorbent trap mercury 

monitoring coupled with parametric monitoring of scrubbers and 

(2) monitoring using a continuous emission monitoring system 

(CEMS) for mercury. Both proposed monitoring options would 

require establishment of operating limits to detect and correct 

problems as soon as possible. An exceedance of an operating 

limit would trigger immediate corrective action and would 

require that the problem be corrected within 48 hours or that 

the feed of ore to the roaster be stopped. 

The first option for monitoring emissions from roasters 

would be to use the EPA Performance Specification (PS) 12B for 

integrated sorbent trap mercury monitoring on a periodic basis 

coupled with parametric monitoring of mercury scrubbers. We 

propose that under this option the facility will sample and 

analyze weekly for mercury concentration according to PS 12B. 

To determine appropriate sampling duration, we propose that the 
41

owner or operator 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, the facility would 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, the 

facility would re-sample using a shorter sampling duration. 

We are proposing that the owner or operator of an affected 

source would establish an operating limit for mercury 

concentration for PS 12B monitoring during the initial 

compliance test and maintain the mercury emissions below the 

established operating limit. The specific method and equation 

to be used to establish the operating limit are described in the 

proposed rule. If the operating limit is exceeded, the facility 

would report the exceedance as a deviation and take corrective 

actions within 48 hours to return the emissions control system 

back to proper operation. 

In addition, we are proposing as part of this first 

monitoring option (i.e., sorbent trap monitoring) that 

facilities with roasters and calomel-based mercury control 

systems (also referred to as “mercury scrubbers”) also establish 

operating limits for various control parameters described below 

during their annual mercury compliance stack test. We are 
42

proposing that each mercury scrubber be equipped with devices to 

monitor the scrubber liquor flow rate, scrubber pressure drop, 

and inlet gas temperature. Minimum operating limits for the 

scrubber liquor flow rate and pressure drop would be established 

based on the lowest average value measured during any of the 

three runs of a compliant performance test. A maximum inlet 

temperature would be established based on the highest 

temperature measured during any of the three runs of the 

compliance test. In addition to the parameters described above, 

we are proposing that the facility must also monitor the 

mercuric ion concentration and the chloride ion concentration 

four times per day or continuously monitor the oxidation 

reduction potential and pH. These monitored parameters would be 

maintained within the range specified by the scrubber’s 

manufacturer or within an alternative range approved by the 

permitting authority. If any of the parameters are outside the 

specified range or limit, corrective action would be taken to 

bring the parameters back to the operating range or limit or 

else the facility would commence shutdown of the roaster. 

As mentioned above, we are including an alternative option 

for monitoring emissions from roasters, which is to install and 

operate a continuous emission monitoring system (CEMS) for 

mercury. Under this alternative option, facilities would not be 

required to do the parametric monitoring of the mercury 
43

scrubbers described above under the first option. A facility 

choosing the CEMS option would operate the mercury CEMS 

according to EPA Performance Specification (PS) 12A (except that 

calibration standards traceable to the National Institute of 

Standards and Technology (NIST) are not required). This 

exception is necessary because the mercury concentrations in the 

exhaust gases from roasters can be higher than the range of 

concentrations that are covered with the existing calibration 

standards traceable to NIST. 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. 

In addition to following PS 12A, the facility would perform 

a data accuracy assessment of the CEMS according to section 5 of 

Appendix F in part 60. We are proposing that the owner or 

operator would establish an operating limit for mercury 

concentration for the CEMS during a compliance test for the 

roaster stack and monitor the daily average mercury 

concentration in the roaster stack exhaust gas with the CEMS. 

The specific method and equation to be used to establish the 

operating limit are described in the proposed rule. If any 

daily average concentration as measured with the CEMS exceeds 
44

the operating limit, the facility would report the exceedance as 

a deviation and take corrective actions within 48 hours to 

return the emission control system back to proper operation. 

Regardless of whether deviations occur, the owner or operator of 

any facility with a roaster would submit a monitoring plan that 

includes quality assurance and quality control (QA/QC) 

procedures sufficient to demonstrate the accuracy of the CEMS. 

At a minimum, the QA/QC procedures would include daily 

calibrations and an annual accuracy test for the CEMS. 

For facilities that control roaster mercury emissions with 

mercury scrubbers, we are proposing not to require sorbent traps 

or mercury CEMs monitoring if a facility demonstrates that the 

mercury emissions from its roasters are consistently low and 

well controlled. Specifically, if a facility can demonstrate 

that mercury emissions from the roaster are less than 10 pounds 

of mercury per million tons of ore, then the facility would be 

allowed to discontinue the use of the sorbent trap or CEMS as 

described above. To demonstrate this, the facility would 

conduct three or more consecutive independent performance tests 

for mercury at least one month apart on the roaster exhaust 

stacks and show that emissions are less than 10 pounds per 

million tons of ore during normal operations for all tests. 

However, such a facility would be required to perform the 

parametric monitoring for mercury scrubbers and maintain 
45

parameters within the operating ranges established in accordance 

with the proposed rule. Also, the facility would continue to 

perform annual compliance tests of the roaster stack. Moreover, 

if there is an increase in the mercury concentration in the ore 

processed by the roaster that is higher than any concentration 

measured during the previous 12 months, then the facility would 

need to perform a compliance test within 30 days of the first 

day that the new ore is processed to determine whether the

mercury emissions are still below 10 lbs per million tons of 

ore. If any subsequent performance compliance test indicates 

that the roaster is emitting more than 10 pounds of mercury per 

million tons of ore input, then the facility would be required 

to monitor the roaster emissions using the sorbent trap method 

or CEMS. 

Carbon Adsorbers. For process units (such as furnaces, 

kilns, retorts, electrowinning, and autoclaves) that control 

mercury emissions with a carbon adsorber, we are proposing three 

emissions monitoring options. One proposed option involves 

monitoring the mercury concentration at the exit of the carbon 

bed. A second option is based on sampling the carbon bed for 

mercury. The third option is based on changing out the carbon 

bed after a fixed period of time determined based on historical 

operating experience. 

For the first option (i.e., the exit concentration 
46

monitoring option), the mercury concentration would be measured 

periodically using a sorbent trap according to EPA Method 30B. 

An operating limit would be established through sorbent trap 

measurements obtained during the initial compliance test. The 

mercury concentration would be measured during each annual 

performance compliance test of each of the stacks for the carbon 

processes using Method 30B. An operating limit would be 

calculated from the average mercury concentration measured 

during the compliance test multiplied by a factor. The factor 

is the MACT emission limit for carbon processes divided by the 

sum of results of the compliance test for all units within the 

carbon processes affected source. Thereafter, if the 

established operating limit is exceeded, the exceedance would be 

reported as a deviation and corrective action would be triggered 

(e.g., replace the carbon in the bed). The specific equations 

to calculate the operating limit are described in the proposed 

rule. Initially, the facility would measure mercury 

concentration in the exit gas monthly using Method 30B. Once 

mercury concentrations reach 50 percent of the operating limit, 

the facility would then need to perform weekly sampling and 

analysis using Method 30B. When the concentration reaches 90 

percent of the operating limit, to prevent an exceedance, the 

owner or operator would be expected to replace the carbon in the 

control device within 30 days (or before the operating limit is 
47

actually exceeded). 

The second proposed monitoring option, which is based on 

sampling the carbon bed for mercury, would require conducting an 

initial sampling of the carbon in the carbon bed 90 days after 

the replacement of the carbon to determine mercury loading. A 

representative sample would be collected from the carbon bed and 

analyzed using EPA Method 7471A, and the depth to which the 

sampler is inserted would be recorded. Based upon sample 

results, a carbon loading would be calculated for the system, 

and sampling would be performed quarterly thereafter. When the 

carbon loading reaches 50 percent of the design capacity of the 

carbon, monthly sampling would be performed until 90 percent of 

the carbon loading capacity is reached. The carbon would be 

removed and replaced with fresh carbon no later than 30 days 

after reaching 90 percent of capacity to ensure that the maximum 

mercury loading as recommended by the manufacturer is not 

exceeded. 

The third proposed option would start with one of the two 

previous options. After collecting at least two years of data 

under one of the options described above, a facility would 

establish a change out time for the carbon based on the two 

years of monitoring and could implement this periodic change out 

instead of sampling and analysis after approval by the 

permitting authority. However, if there is any significant 
48

change in the process, input materials, or mercury control 

system (e.g., an increase in operating rates or processing 

different ores with higher mercury levels) then sampling and 

analysis (according to the procedures in option 1 or option 2 

described above) would be required within 30 days to reestablish the carbon change out time. 

We are also proposing that the inlet stream to carbon 

adsorbers applied to autoclaves, carbon kilns, melt furnaces, 

and retorts be monitored for temperature and that the inlet 

temperature be maintained below the maximum temperature 

established during the compliance tests. If the maximum 

temperature is exceeded, the owner or operator would analyze the 

outlet concentration using Method 30B within 30 days as 

described above. If the concentration is below 90 percent of 

the operating limit, the owner or operator could set a new 

temperature operating limit 10°F above the previous operating 

limit. On the other hand, if the concentration is more than 90 

percent of the operating limit, the facility would take 

corrective action to reduce the temperature back down to below 

the maximum temperature recorded during compliance tests and 

then retest emissions using Method 30B. If the concentration is 

more than 90 percent of the operating limit based on this 

subsequent test, then the facility must replace the carbon. 

Wet scrubbers. For each wet scrubber, we are proposing 
49

that pressure drop and water flow rate be maintained at a 

minimum level based on measurements during the initial or 

subsequent compliance test(s). 

E. What are the notification, recordkeeping, and reporting 

requirements?

The owner or operator of an existing or new affected source 

would be required to comply with certain notification, 

recordkeeping, and reporting requirements of the NESHAP General 

Provisions (40 CFR part 63, subpart A), which are identified in 

Table 1 of this proposed rule. Each owner or operator of an 

affected source would submit an Initial Notification according 

to the requirements in 40 CFR § 63.9(a) through (d) and a 

Notification of Compliance Status according to the requirements 

in 40 CFR § 63.9(h). 

 Each owner or operator of an existing or new affected 

source would be required to keep records to document compliance 

with the mercury emission limits. Owners or operators of new 

and existing affected sources would maintain records of all 

monitoring data. Other records include monthly totals of ore 

quantity for ore pretreatment affected sources, monthly 

quantities of concentrate for all other affected sources, and 

monthly hours of operation for each process unit at each 

affected source. 
50

 If a deviation from this rule’s requirements occurs, an 

affected source would be required to submit a compliance report 

for that reporting period. The proposed rule specifies the 

information requirements for such compliance reports. 

 We are also proposing to require electronic reporting of 

performance evaluation data collected using methods compatible 

with EPA’s Electronic Reporting Tool (ERT). After December 31, 

2011, within 60 days after the date of completing each 

performance evaluation conducted to demonstrate compliance, the 

owner or operator would 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 would enter the test data into EPA’s data base 

using the ERT or other compatible electronic spreadsheet. Only 

performance evaluation data collected using methods compatible 

with ERT would be subject to this requirement to be submitted 

electronically into EPA’s WebFIRE database. 

F. What are the title V permit requirements?

 Under section 502(a) of the CAA, all major sources and 

certain other sources, including sources subject to section 112 

standards, are required to operate in compliance with a title V 

permit. Today’s proposal requires that gold mine ore processing 

and production area sources comply with the title V permitting 

requirements. However, section 502(a) of the CAA provides that 
51

the Administrator may exempt an area source category (in whole 

or in part) from title V if she/he determines that compliance 

with title V requirements is “impracticable, infeasible, or 

unnecessarily burdensome” on such category. We are therefore 

soliciting comment on whether such an exemption is appropriate 

under section 502(a) for any particular sources in this 

category. Commenters should provide supporting data and 

rationale to explain the bases for their comments.1

G. Emissions of Non-Mercury HAPs: 

 EPA recently gathered data and evaluated emissions of other 

HAP, including cyanide and non-mercury metals. The data 

indicate that the gold mining processing and production category 

consists of only area sources (i.e., facilities that emit less 

than ten tons per year of any one HAP and less than 25 tons per 

year of any combination of HAP). However, a few facilities are 

close to the major source threshold due to hydrogen cyanide 

(HCN). For example, the largest facility emits an estimated 5 

to 9 tons of HCN per year. Emissions of all other HAPs, 

including mercury, are individually significantly lower than the 

10 ton per year threshold for a single HAP and the 25 ton per 

 

1

 For the factors that EPA considers in evaluating whether to 

exercise the Agency’s discretion to exempt area sources from 

title V, please see National Emission Standards for Hazardous 

Air Pollutants for Area Sources: Clay Ceramic Manufacturing, 

Glass Manufacturing, and Secondary Nonferrous Metal Processing; 

Proposed rule, 72 Fed. Reg. 53838, 53849-53853 (September 20, 

2007). 
52

year threshold for a combination of HAP. However, depending on 

how facilities manage their cyanide processes, EPA believes that 

cyanide emissions could potentially change a facility’s status 

from area source to major source. Although EPA would develop 

MACT standards if it ever identified any major sources of gold 

mine ore processing and production, the MACT standards in 

today’s proposal apply only to area sources because those are 

the only gold mine ore processing and production sources EPA has 

identified. 

 In light of the above, we are considering including in 

today’s NESHAP a provision under whichallowing sources mayto

certify and demonstrate that they are area sources of gold mine 

ore processing and production. We would include in this area 

source NESHAP management practices for cyanide processes that we 

believe would effectively limit cyanide emissions and thus 

assure that sources maintain their area source status. To the 

extent sources were concerned about their HCN emissions, they 

could implement the management practices for cyanide processes 

specified in this rule and certify to the Agency that they had 

done so. Some management practices we are considering include: 

maintaining pH of cyanide leach solutions greater than nine; 

burying leach lines whenever practical and feasible; monitoring 

cyanide concentrations at the perimeter and in a downwind 

direction of main emission sources; not allowing puddles to form 
53

that are greater than 1 square meter on leach pads; and in 

locations that have the highest potential for concentrated 

emissions (e.g., mixing tanks, CIL tanks, loading stations) 

maintain HCN air concentrations below a prescribed level (e.g., 

5 ppm). 

 We request comment on whether we should include the proposal 

described above or some modification of it. We also request 

comment on effective management practices to limit cyanide 

emissions, including the practices described above as well as 

other approaches to manage cyanide emissions.

H. Request for comments.

As mentioned previously, we are soliciting comments on all 

aspects of this proposed rule, including, but not limited to, 

the data and calculations used to establish the emissions limits

for mercury, the proposed requirements and options for emissions 

testing and monitoring, the parametric monitoring options for 

control devices, title V permit requirements, and emissions of

non-mercury HAPs. 

V. Rationale for the Proposed Standards

A. How did we select the affected source?

 We are proposing individual MACT standards for each of the 

following three affected sources in the gold mine ore processing 

and production source category: ore pretreatment processes, 

carbon processes, and non-carbon concentrate processes. These 
54

three affected sources reflect the three primary different types 

of processes used in this source category to produce gold. 

Moreover, many gold mine ore processing and production 

facilities combine the emissions from multiple process units 

within a single affected source and route them to a single 

mercury emission control system and stack. Because we cannot 

determine the mercury emissions from individual process units 

that share a stack, it is difficult to establish emission 

standards for each process unit within an affected source. 

Setting MACT standards for each of the three affected sources 

accommodates the various stack and control configurations for 

the process units within an affected source. Emissions from all 

process units in the affected source would be summed to 

determine compliance with the proposed MACT standard for that 

affected source. 

 As described above, the three affected sources differ in 

process operations, the sources of mercury entering the 

processes, and the nature of the emissions. Ore pretreatment 

processes include roasting operations (roasters, ore dryers, ore 

pre-heaters, and quenchers) and autoclaves that are used to 

pretreat refractory ore, which contains organic carbon and/or 

sulfide mineral grains that prevent the initial use of cyanide 

leaching to extract the gold effectively from the ore. Mercury 

enters these processes with the ore. The potential for mercury 
55

emissions from this affected source is directly related to the 

amount of ore processed in the autoclaves and roasters; the 

proposed standard for this affected source is therefore 

expressed in pounds of mercury emissions per million tons of ore 

processed (lb/million tons of ore). 

 Carbon processes include carbon kilns, electrowinning 

cells, melt furnaces, retorts, and preg tanks at facilities that 

use carbon to recover gold from pregnant cyanide solution. In 

developing a proposed format for the emission limit for carbon 

processes, we examined the use of stripped carbon, concentrate, 

and gold production in the denominator of a pound per ton 

format. In other NESHAPs, we have typically used the amount of 

feed throughput or the amount of product produced in the 

denominator of the emission limit. For example, in the proposed 

revisions to the Portland cement NESHAP (74 FR 21136, May 6, 

2009), we analyzed the data and developed the MACT floor in 

terms of pounds per million tons of feed to the kiln and 

subsequently converted the emission limit to a format of pounds 

per million tons of clinker (i.e., the product from the kiln). 

Although stripped carbon can be considered the “primary feed”, 

we discovered there were potential issues with its measurements 

(e.g., default values were used for density), we were unsure 

that the data from different facilities were comparable, and it 

was not a quantity that has been required to be reported under 
56

existing State regulatory programs. We rejected the use of gold 

produced because some facilities do not produce gold (they send 

the intermediate product to offsite refineries), and the 

quantity of gold varies depending on the percent of gold in the 

product. The primary intermediate product that is common to all 

of the facilities with these carbon processes is the goldbearing concentrate, which is the input to retorts or melt 

furnaces. Further, concentrate is closely related to the final 

product because it contains about 60 percent gold, and because 

of its value, it is carefully and accurately weighed and records 

of the quantities are kept. Concentrate is also required to be 

reported under the NDEP program, so we had comparable and 

reliable data from the different gold mine ore processing and 

production facilities. Consequently, we decided that the most 

appropriate format of the emission limit for the carbon 

processes is lb/ton of concentrate. 

 For the reasons discussed above, we are proposing the 

concentrate format. However, we also considered using the 

amount of carbon stripped for the denominator of the emission 

limit format for carbon processes instead of concentrate, and we 

believe there may be merit in using carbon as the denominator. 

Therefore, we are soliciting comments on the merits of both 

formats. In particular, we seek comments on whether loaded 

carbon or concentrate would be the better format for compliance 
57

determinations (e.g., accuracy and reliability of the 

measurements, availability of records) or for other reasons or 

factors, such as the processes present at a given plant, 

operating layout, or offsite shipments for processing. We are 

also requesting comment on whether the quantity of concentrate 

should be determined on an “as fed” or dry basis, and if a dry 

basis, what methods could be used to determine dry weight 

accurately and reproducibly. 

 Non-carbon concentrate processes include retorts and melt 

furnaces at facilities that neither use carbon to recover gold 

nor pre-treat ore before leaching. The facilities that conduct 

non-carbon processes do not have roasters, autoclaves, or carbon 

kilns; they use only retorts and melt furnaces to recover the 

gold. As described above, during the non-carbon processes, zinc 

dust is added to the cyanide solution after leaching to 

precipitate gold and other metals (including mercury). The 

precipitate (or “non-carbon concentrate”) is then processed in 

retorts and metal furnaces, liberating mercury from the 

concentrate. The potential mercury emissions are therefore 

directly related to the amount of concentrate processed; 

consequently for this reason and the merits of using concentrate 

as discussed above, the proposed standard for this affected 

source is expressed in lb/ton of concentrate. 

B. How did we determine MACT?
58

1. Selection of MACT Floors for Existing Sources for the Three 

Affected Sources 

 CAA section 112(d)(3)(B) requires that the MACT standards 

for existing sources be at least as stringent as the average 

emission limitation achieved by the best performing five sources 

(for which the Administrator has or could reasonably obtain 

emissions information) in a category with fewer than 30 sources. 

The gold mine ore processing and production source category 

consists of fewer than 30 sources. As mentioned above, we are 

proposing MACT standards for each of the following three 

affected sources: ore pretreatment processes, carbon processes, 

and non-carbon concentrate processes. We have mercury emissions 

data on ore pretreatment processes for all five facilities in 

the United States with ore pretreatment processes. We have 

mercury emissions data on carbon processes for 11 facilities and 

mercury emissions data on non-carbon concentrate processes for 

two facilities. Pursuant to section 112(d)(3), the MACT floor 

limits for existing ore pretreatment processes and carbon 

processes are based on the average emission limitation achieved 

by the best performing five facilities for each of these two 

affected sources, and the MACT floor limit for existing noncarbon concentrate processes are based on the average emission 

limitation achieved by the two facilities with such processes. 

 To calculate the MACT floor limit for each of the affected 
59

sources, we established and ranked sources’ emissions from 

lowest to highest. The data on which we based the limits are 

expressed in terms of pounds of mercury emitted per ton of 

input, where the gold mine ore is the input for the ore 

pretreatment processes and concentrate is the input for the 

carbon processes and the non-carbon concentrate processes. 

We used the emissions data for those best performing 

affected sources to determine the emission limits to be 

proposed, with an accounting for variability. EPA must exercise 

its judgment, based on an evaluation of the relevant factors and 

available data, to determine the level of emissions control that 

has been achieved by the best performing sources under variable 

conditions. The Court has recognized that EPA may consider 

variability in estimating the degree of emission reduction 

achieved by best-performing sources and in setting MACT floors. 

See Mossville Envt’l Action Now v. EPA, 370 F.3d 1232, 1241–42 

(D.C. Cir 2004) (holding EPA may consider emission variability 

in estimating performance achieved by best-performing sources 

and may set the floor at level that best-performing source can 

expect to meet “every day and under all operating conditions”). 

 To calculate the achieved emission limit, including 

variability, we used the equation:2

 

2 More details on the calculation of the MACT floor limits are 

given in the technical memo in the docket. 
60

UPL = xp + t * (vT)0.5

where 

UPL = upper prediction limit (99 percent), 

xp = average of the best performing MACT pool sources, 

t = Student’s t-factor evaluated at 99 percent confidence, and 

vT = total variance determined as the sum of the within-source 

variance and the between-source variance. 

 The between-source variance is the variance of the average 

of the best performing source averages. The within-source 

variance is the variance of the MACT source average considering 

“m” number of future individual test runs used to make up the 

average to determine compliance. We are proposing that a 

compliance test would be based on the average of three runs; 

consequently, the value of “m” used in the statistical analysis 

is 3. This value of “m” is used to reduce the variability to 

account for the lower variability when averaging of individual 

runs is used to determine compliance in the future. For 

example, if the average of three test runs is used to determine 

compliance (m=3), the variability based on 3-run averages is 

lower than the variability of the single run measurements in the 

data base, which results in a lower UPL for the 3-run average. 

 Our MACT floor limit calculations are based primarily on 

mercury emissions data from annual testing that was required by 

NDEP for 2007 and 2008. However, we used data from 2006 for an 

autoclave at a Nevada facility that was not tested in 2007 and 

did not operate in 2008. We also used data from 2009 to replace 
61

2008 test data at one Nevada facility that was invalidated due 

to not following the procedures in the State’s testing protocol. 

In addition, we used 2010 test data for a Nevada facility that 

installed new mercury emission controls on its roasters and 

resumed operation in late 2009. The tests that generated the 

data described above generally consisted of three runs per test 

per process at each facility. There were cases where 2007 

results represent emissions before a control device was 

installed, and 2008 test results were after a mercury emission 

control device had been installed. In those cases, we used only 

the 2008 (controlled) test results to determine the top 

performing facilities. Emissions from the tests (in lb/hr) were 

multiplied by the number of hours the process operated in the 

calendar year and then divided by the process input rate for the 

year (in tons) to calculate the facility’s performance for an 

affected source (expressed as lbs of mercury emissions per ton 

of input material). 

 Source performance and the resulting MACT floor limits are 

summarized in Tables 2, 3, and 4, for ore pretreatment, carbon, 

and non-carbon concentrate processes, respectively. 

Table 2. MACT Floor Results for Ore Pretreatment 

Facility 

Average performance 

(lb/million tons ore) 

A 62 

B 64 
62

C 69 

E 90 

D 211 

Average of top 5 99 

99% UPL existing (MACT Floor) 175 

99% UPL new (MACT Floor) 163 

Table 3. MACT Floor Results for Carbon Processes 

Facility 

Average performance 

(lb/ton concentrate) 

M 0.06 

N 0.60 

A 1.5 

H 1.8 

D 2.9 

F 3.1 

C 3.7 

I 6.9 

G 9.7 

B 21 

J 39 

 

Average of top 5 1.4 

99% UPL existing (MACT Floor) 2.6 

99% UPL new (MACT Floor) 0.14 

Table 4. MACT Floor Results for Non-Carbon Concentrate 

Processes 

Facility 

Average performance (lb/ton 

concentrate) 

K 0.07 

L 0.11 

 

Average of top 2 0.09 

99% UPL existing 0.25 

99% UPL new 0.20 
63

The average emission rates for ore pretreatment and carbon 

processes from the top five facilities performing these 

processes are 99 lbs/million tons ore and 1.4 lb/ton of 

concentrate, respectively. The average emission rate for noncarbon concentrate processes from the top two facilities 

performing these processes is 0.09 lb/ton of concentrate. As 

previously discussed above, we account for variability in 

setting floors, not only because variability is an element of 

performance, but also because it is reasonable to assess best 

performance over time. Here, for example, we know that the 2 to 

5 lowest emitting affected sources’ emission estimates are 

averages and we expect that the actual emissions will vary over 

time. If we do not account for this variability, we would 

expect that even the sources that perform better than the floor 

on average would potentially exceed the floor emission levels 

part of the time. 

For the lowest emitting sources (2 to 5 sources, depending 

on the affected source), we calculated an average emission rate 

using the data from multiple test runs for multiple processes. 

The results are shown in Tables 2, 3, and 4 and represent the 

average performance of each source from the sum of the average 

emissions from all process units within the affected source. We 

then calculated the average performance of the lowest emitting 
64

sources and the variances of the emission rates for each process 

unit, which is a direct measure of the variability of the data 

set. This variability includes the run-to-run and year-to-year 

variability in the total mercury input to each process unit and 

variability of the sampling and analysis methods over the 

testing period, and it includes the variability resulting from 

site-to-site differences for the lowest emitters. We calculated 

the MACT floor based on the UPL (upper 99th percent) as 

described earlier from the average performance of the lowest 

emitting sources, Students t-factor, and the total variability, 

which was adjusted to account for the lower variability when 

using 3-run averages to determine compliance. Our calculations 

yield the following MACT floor limits for existing sources: 175 

lbs/million tons of ore for ore pretreatment processes, 2.6 

lb/ton of concentrate for carbon processes, and 0.25 lbs/ton of 

concentrate for non-carbon concentrate processes. 

 The technologies for achieving the MACT floor for existing 

ore pretreatment processes include mercury scrubbers on roasters 

and venturi scrubbers on autoclaves and ancillary roaster 

operations. The roasters and autoclaves at Facilities A, B, C, 

and E shown in Table 2 above are already equipped with these 

controls. Our MACT floor analysis indicates that these 

facilities are achieving the MACT floor average of 99 lb/million 

tons of ore. The analysis also indicates that an emission 
65

reduction will be needed for Facility D to achieve the MACT 

floor. Currently Facility D also has venturi scrubbers on its 

autoclaves; however, the emission control performance of these 

scrubbers will need to be improved to achieve the MACT floor. 

 To achieve the MACT floor for existing carbon processes, we 

expect that facilities would need to install carbon adsorbers on 

all process units that do not already have them (i.e., carbon 

adsorbers for carbon kilns, electrowinning, preg tanks, retorts, 

and melt furnaces). Our MACT floor analysis indicates that only 

Facilities M and N in Table 3 are achieving the MACT floor level 

of control; consequently, the other nine facilities in Table 3 

are expected to have to install carbon adsorbers on all process 

units that do not already have them. The two top performing 

facilities (M and N) are fully equipped with carbon adsorbers 

(i.e., all of their process units are controlled by carbon 

adsorbers). Facility M also processes ore which has 

significantly lower mercury concentrations compared to the ore 

processed at most other facilities. We believe the combination 

of processing ore with low mercury content and the use of stateof-the-art mercury emission controls result in emissions at 

Facility M that are considerably lower than the other 

facilities. 

 For the non-carbon concentrate processes, the MACT floor 

technology is the use of carbon adsorbers on retorts and melt 
66

furnaces. We expect that Facility L would probably need to 

install a carbon adsorber on their melt furnace to achieve the 

MACT floor. 

2. Selection of New Source Floors for the Three Affected Sources 

 CAA section 112(d)(3) requires that the MACT floor limit 

for new sources not be less stringent than the emission control 

that is achieved in practice by the best controlled similar 

source. Table 2 above shows that Facility A has the lowest 

emission rate for ore pretreatment processes and is therefore 

considered the “best controlled similar source” for such 

processes. As previously mentioned, this facility is equipped 

with calomel scrubbers on roasters and venturi scrubbers on 

autoclaves. The emission rate for ore-pretreatment processes at 

Facility A is 62 lbs/million tons ore, not accounting for 

variability. Applying the UPL formula discussed earlier to 

account for variability based on the emission test runs for all 

affected process units at the best performing ore pretreatment 

affected source (Facility A), we calculated the 99th percentile 

of performance, which results in a new source MACT level of 163 

lb/million tons of ore for ore pre-treatment processes. 

 Table 3 shows that Facility M has the lowest emission rate 

for carbon processes and is therefore considered the “best 

controlled similar source” for such processes. As previously 

mentioned, all carbon process units at Facility M are well 
67

controlled with carbon absorbers. The emission rate for carbon 

processes at Facility M is 0.06 lb/ton of concentrate. After 

applying the UPL formula as described above to account for 

variability, the new source floor for carbon processes based on 

the 99th percentile of performance is 0.14 lb/ton of concentrate. 

 For carbon processes at new sources, we are proposing a 

compliance alternative to provide flexibility in determining 

compliance because of the wide variety of process combinations 

and variations in input material that may be present at future 

new carbon process sources. A well-established and conventional 

metric for expressing the degree of emission control is the 

percent control of the target pollutant. As mentioned above, 

Facility M is considered the “best controlled similar source” 

for carbon processes. Test data were available for 2007 for 

Facility M when the processes were uncontrolled, for 2008 when 

the controls were newly installed, and from 2009 after over one 

year of operation. The test results showed a 99.6 percent 

mercury emission reduction in 2008 and 93.5 percent reduction in 

2009. Based on these results and considering variability over 

time, we are proposing a compliance alternative of 97 percent 

reduction in mercury emissions for new carbon processes. This 

compliance alternative was calculated based on the average 

reduction achieved by the best performing source in 2008 and 

2009. 
68

 Table 4 shows that Facility K has the lowest emission rate 

for non-carbon concentrate processes and is therefore considered 

the “best controlled similar source” for such processes. The 

emission rate for non-carbon concentrate processes at Facility K 

is 0.07 lb/ton of concentrate (not accounting for variability). 

Again applying the UPL formula as described above to account for 

variability, the new source floor for non-carbon concentrate 

processes based on the 99th percentile of performance is 0.20 

lb/ton of concentrate. 

3. Beyond the Floor Determination 

 To evaluate opportunities for emission reductions beyond 

those provided by the MACT floor, we typically identify control 

techniques that have the ability to achieve an emissions limit 

more stringent than the MACT floor. As mentioned above, the 

facilities with ore pretreatment processes would have installed 

mercury scrubbers and venturi scrubbers on their roasters and 

autoclaves, respectively, to achieve the MACT floor for ore 

pretreatment processes. To achieve further reductions in 

mercury beyond what can be achieved using mercury scrubbers and 

venturi scrubbers, we identified as a beyond-the-floor option 

the installation of both a refrigeration unit (or condenser) and 

a carbon adsorber on autoclaves. This additional control system 

would follow the existing venturi scrubbers to further reduce 

mercury emission from autoclaves. Because the exhaust is 
69

saturated with water, a refrigeration unit or condenser would be 

needed to remove water that would otherwise adversely affect the 

adsorptive capacity of the carbon adsorber. With this 

additional control system, all facilities with ore pretreatment 

processes could achieve an average performance of 90 lb/million 

tons of ore or less. This is lower than the average emission 

rate of 99 lbs/million tons ore for ore pretreatment processes 

from the top five facilities performing these processes. 

 In determining whether to control emissions “beyond-thefloor,” we must consider the costs, non-air quality health and 

environmental impacts, and energy requirements of such more 

stringent control. See CAA Section 112(d)(2). We estimate that 

the capital cost for the additional controls on the autoclaves 

would be $890,000 with a total annualized cost of $720,000/yr. 

Mercury emissions would be reduced by 543 lbs, resulting in an 

estimated cost effectiveness of $1,300/lb. Energy consumption 

would increase by about 730 megawatt-hours per year, primarily 

due to the refrigeration unit. Solid waste generation and 

disposal (spent carbon loaded with mercury) would increase by 

about 3 tons per year. (See Section VI.A for additional 

discussion of our consideration of emissions, cost, and non-air 

impacts in developing MACT standards for this source category.) 

After considering the costs and the above-mentioned impacts 

associated with the use of a refrigeration unit (or condenser) 
70

and a carbon adsorber on autoclaves, we believe that the 

emission reduction that can be achieved with this additional 

control system is justified under section 112(d) of the CAA. 

Applying the UPL formula discussed earlier to account for 

variability, the 99th percent UPL would be 149 lb/million tons of 

ore. We therefore propose that the beyond-the-floor performance 

level of 149 lb/million tons of ore is MACT for new and existing 

ore pretreatment processes. 

 For the carbon processes, we estimate that 9 of the 11 

facilities for which we have data will need to improve control 

to meet the floor limits because these 9 plants have an average 

emission control performance that is above the MACT floor 

average performance. There are a few facilities in the middle 

of the rankings that will probably only need marginal 

improvements, but several facilities (especially those at the 

bottom of the ranking that average several times the floor 

average) will need significant improvements in mercury emission 

control. We estimate that the MACT floor limit for the carbon 

processes will reduce emissions by about 1,100 lbs per year, a 

reduction of 89 percent from current levels. Our estimates of 

impacts for the MACT floor indicate that most of the carbon 

processes currently have or will have carbon adsorbers installed 

to effectively control mercury emissions at the MACT floor 

level. Considering the very low mercury concentrations when the 
71

carbon processes are performing at the MACT level of control, it 

is difficult to identify a technology that can obtain efficient 

additional percent reductions from low concentration streams. 

For a beyond-the-floor analysis, we assumed that theoretically a 

second carbon adsorption system could be installed in series 

with the first one and would get an additional 90 percent 

reduction from the very low mercury concentrations that result 

from the MACT floor level of control. We acknowledge that there 

is uncertainty as to the additional percent reduction the second 

control system might achieve. Nevertheless, we estimate that 

the emission reduction would only be 12 lbs per year. The 

capital cost was estimated as $3.2 million with a total 

annualized cost of about $1.2 million/yr and a cost 

effectiveness of $100,000/lb. Considering the significant cost 

and the small additional reduction in emissions associated with 

a second carbon adsorption system and the uncertainty that even 

that small reduction might be achieved, we believe that the 

additional emission reduction from this beyond-the-floor control 

option is not warranted under section 112(d). 

 For the non-carbon concentrate processes, we expect that 

Facility L would probably need to add a carbon adsorber to its 

melt furnace to achieve the MACT floor level of control. For 

beyond the floor, we again assumed that the existing carbon 

adsorbers would be supplemented by adding a second control 
72

system of carbon adsorbers in series for all of the melt 

furnaces. We estimated the capital cost for the second set of 

control systems as $0.7 million and a total annualized cost of 

$306,000/year. Emissions would be reduced by 7 lb/year, which 

results in a cost effectiveness of $44,000/lb. Considering the 

very small emission reduction from a second carbon adsorber 

system, and its high capital and operating costs, we believe 

that the emission reduction associated with this additional 

control system is not warranted under section 112(d) of the CAA. 

C. How did we select the testing, monitoring and electronic 

reporting requirements?

We are proposing testing and monitoring requirements to 

assure compliance with the emission standards set forth in this 

proposed rule. These compliance assurance provisions are based, 

in part, on requirements that have been applied to this source 

category in State operating permits, EPA requirements applied to 

other industries that emit mercury, and an understanding of how 

control devices and processes perform and can be effectively 

monitored. 

We are proposing initial compliance stack tests for mercury 

(using Method 29) within the first 180 days of the compliance 

date and annual compliance tests thereafter for all thermal 

process units to determine compliance with the proposed emission 

limits. The testing frequency and procedures would be 
73

essentially the same as the NDEP requirements for the facilities 

that are located in Nevada partly because the stack test data 

that we used to develop the proposed emission limits were based 

on the test methods applied in Nevada. To provide additional 

flexibility, we propose to allow the use of the Ontario Hydro 

Method, Method 30A, or Method 30B as alternatives to EPA Method 

29. 

We also propose the following monitoring requirements to 

assure compliance with the proposed MACT standards. 

Roasters. In addition to the annual stack test, we are 

proposing two options for monitoring roaster emissions: (1) 

integrated sorbent trap mercury monitoring coupled with 

parametric monitoring of scrubbers and (2) monitoring using a 

continuous emission monitoring system (CEMS) for mercury. Both 

proposed monitoring options would require establishment of 

operating limits to detect and correct problems as soon as 

possible. An exceedance of an operating limit for the sorbent 

trap or CEMS monitoring would trigger immediate corrective 

action and would require that the problem be corrected within 48 

hours or that the feed of ore to the roaster be stopped. 

As part of this first monitoring option (i.e., sorbent trap 

monitoring), we are also proposing that facilities with roasters 

and mercury scrubbers establish operating limits for various 

parameters during their compliance test (i.e., the annual stack 
74

test for mercury emissions). The proposed parametric monitoring 

provides additional compliance assurance by ensuring that the 

process and control devices are operating properly. The 

proposed parameters for monitoring mercury scrubbers are similar 

to those currently required to be monitored in the title V 

operating permits issued by NDEP for roasters. We are proposing 

that each mercury scrubber be equipped with devices to monitor 

the scrubber liquor flow rate, scrubber pressure drop, and inlet 

gas temperature. Minimum operating limits for the scrubber 

liquor flow rate and pressure drop would be established based on 

the lowest average value measured during any of the three runs 

of a compliant performance test. A maximum inlet temperature 

would be established based on the highest temperature measured 

during any of the three runs of the compliance test. In 

addition to the parameters described above, we are proposing 

that the facility would also monitor the mercuric ion 

concentration and the chloride ion concentration four times per 

day or continuously monitor the oxidation reduction potential 

and pH. These monitored parameters would be maintained within 

the range specified by the scrubber’s manufacturer or within an 

alternative range approved by the permitting authority. If any 

of the parameters are outside the specified range or limit, 

corrective action would be taken to bring the parameters back 

within the operating range or the facility would commence 
75

shutdown of the roaster. 

As mentioned above, we are including a mercury CEMS as an 

alternative for monitoring of mercury emissions from roasters. 

This monitoring option would not require parametric monitoring 

of the mercury scrubbers. Mercury CEMS have been applied at 

other industrial sources that emit mercury, such as coal-fired 

power plants and cement production plants, and these devices 

yield valuable information regarding continuous emissions 

performance. We realize that mercury CEMs have not yet been 

demonstrated on roasters at gold production facilities and that 

there are currently no calibration standards traceable to NIST 

within the range of mercury concentrations from roasters. 

However, calibration standards are available from the 

manufacturers of mercury CEMS. Based on the Agency’s 

understanding and experience relative to continuous mercury 

monitoring at other industrial facilities, such as coal-fired 

power plants and cement plants, as well as research experience, 

EPA believes that the CEMS can be adequately calibrated with 

manufacturers’ standards and be used as a valuable tool to 

monitor roasting operations to detect deviations in performance. 

We therefore believe that it is appropriate to propose the use 

of mercury CEMS as a monitoring option for roasters. However, 

we believe that it is appropriate to also propose an alternative 

monitoring approach based on frequent (weekly) monitoring using 
76

a sorbent trap method. 

We request comments on the viability of using mercury CEMs,

specifically for monitoring mercury emissions from roasters at 

gold ore processing and production facilities. We request 

comments on calibration methods, costs, reliability and other 

aspects of the CEMs. We also request similar comments on the 

sorbent trap method.

For facilities that control roaster mercury emissions with 

mercury scrubbers, we are proposing that if a facility 

demonstrates, in accordance with the demonstration requirements 

in the proposed rule, that mercury emissions from the roaster 

are less than 10 pounds of mercury per million tons of input 

ore, they can cease monitoring via either the sorbent trap or 

the mercury CEMS. Such a facility would be required to conduct 

the parametric monitoring for mercury scrubbers as described 

above (under option one) and maintain parameters within the 

operating ranges established in accordance with the proposed 

rule. Also, the facility would continue to perform annual 

compliance tests of the roaster stack to demonstrate emissions 

continue to be less than 10 pounds of mercury per million tons 

of input ore. We believe that for roasters that are effectively 

controlled with mercury scrubbers (i.e., emitting less than 10 

pounds per million ton of ore during normal operations), 

parametric monitoring of the scrubbers would be sufficient. 
77

This monitoring option provides additional incentive for 

facilities to reduce emissions from roasters. However, if any 

subsequent compliance tests indicate that the roaster is 

emitting more than 10 pounds of mercury per million tons of ore 

input, then the facility would be required to monitor the 

roaster emissions using a sorbent trap method or CEMS. 

We are specifically requesting comments on the advantages 

and disadvantages of the two options for monitoring emissions 

from roasters along with any supporting data and documentation 

to support one or both of the options. We are also requesting 

comment on the proposed daily averaging time when using the 

mercury CEMS option and the frequency of sampling when using the 

sorbent trap option. In addition, we are requesting comments on 

the proposed monitoring approach for low-emitting roasters with 

mercury scrubbers, as described in the paragraph above, and 

possible alternatives to this approach. Moreover, we are 

requesting comments on the parametric monitoring methods. 

Carbon Adsorbers. For process units (such as furnaces, 

kilns, retorts, electrowinning, and autoclaves) that control 

mercury emissions with a carbon adsorber, we are proposing three 

options. One option involves monitoring the mercury 

concentration at the exit of the carbon bed. A second option, 

adopted from requirements in some NDEP permits, is based on 

sampling the carbon bed for mercury. The third option is based 
78

on changing out the carbon bed after a fixed period of time 

determined based on historical operating experience. 

We believe that all three options could provide reasonable 

assurance that the carbon adsorber is operating properly on a 

continuing basis and that the carbon is replaced before 

breakthrough occurs. Our current preference among the three 

proposed monitoring options for carbon beds described above is 

the option of sampling the exit gas from the carbon bed using 

EPA Method 30B along with continuous temperature monitoring 

because this option provides a direct measurement of the amount 

of mercury exiting the control device. We are specifically 

requesting comments on the advantages and disadvantages of the 

three options along with any supporting data and documentation. 

Based on public comments, we intend to promulgate one or more of 

these options or a modified version as necessary. 

We are also proposing that the inlet stream to carbon 

adsorbers applied to autoclaves, carbon kilns, melt furnaces, 

and retorts be monitored for temperature and that the inlet 

temperature be maintained below the maximum temperature 

established during the compliance tests. We believe the 

temperature monitoring is needed to detect any excursions in 

mercury emissions caused by excessively high temperatures. We 

are also considering a reduction in frequency of the sampling 

and analysis based on historical data on the life of a new 
79

carbon bed (e.g., quarterly sampling when the carbon bed is 

fresh and monthly sampling after a specified period of time) and 

for processes that are very small sources of mercury emissions. 

We are requesting comments and supporting data on these options 

and others that may be appropriate for monitoring carbon beds. 

Wet scrubbers. For each wet scrubber, we are proposing 

that pressure drop and water flow rate be maintained at a 

minimum level based on measurements during the initial or 

subsequent compliance test(s). These parameters are the typical 

monitoring parameters required by other MACT standards and by 

State operating permits for wet scrubbers at gold mine ore 

processing and production facilities. Monitoring these 

parameters ensures that wet scrubbers are operating properly. 

Electronic reporting. The EPA must have performance test 

data to conduct effective reviews of CAA Section 112 and 129 

standards, as well as for many other purposes including 

compliance determinations, emissions factor development, and 

annual emissions rate determinations. In conducting these 

required reviews, we have found it ineffective and time 

consuming not only for us but also for other regulatory agencies 

and source owners and operators to locate, collect, and submit 

emissions test data because of varied locations for data storage 

and varied data storage methods. One improvement that has 

occurred in recent years is the availability of stack test 
80

reports in electronic format as a replacement for cumbersome 

paper copies. 

In this action, we are taking a step to improve data 

accessibility. Owners and operators of affected facilities 

would be required to submit to an EPA electronic database an 

electronic copy of reports of certain performance tests required 

under this rule. Data entry would be through an electronic 

emissions test report structure called the Electronic Reporting 

Tool (ERT) that will be used by the staff as part of the 

emissions testing project. The ERT was developed with input 

from stack testing companies who generally collect and compile 

performance test data electronically and offices within State 

and local agencies which perform field test assessments. The 

ERT is currently available, and access to direct data submittal 

to EPA’s electronic emissions database (WebFIRE) will become 

available by December 31, 2011. 

The requirement to submit source test data electronically 

to EPA would not require any additional performance testing and 

would apply to those performance tests conducted using test 

methods that are supported by ERT. The ERT contains a specific 

electronic data entry form for most of the commonly used EPA 

reference methods. The website listed below contains a listing 

of the pollutants and test methods supported by ERT. In 

addition, when a facility submits performance test data to 
81

WebFIRE, there would be no additional requirements for emissions 

test data compilation. Moreover, we believe industry would 

benefit from development of improved emissions factors, fewer 

follow-up information requests, and better regulation 

development as discussed below. The information to be reported 

is already required for the existing test methods and is 

necessary to evaluate the conformance to the test method. 

One major advantage of submitting source test data through 

the ERT is that it provides a standardized method to compile and 

store much of the documentation required to be reported by this 

rule while clearly stating what testing information we require. 

Another important benefit of submitting these data to EPA at the 

time the source test is conducted is that it will substantially 

reduce the effort involved in data collection activities in the 

future. Specifically, because EPA would already have adequate 

source category data to conduct residual risk assessments or 

technology reviews, there would likely be fewer or less 

substantial data collection requests (e.g., CAA Section 114 

letters). This results in a reduced burden on both affected 

facilities (in terms of reduced manpower to respond to data 

collection requests) and EPA (in terms of preparing and 

distributing data collection requests). 

State/local/Tribal agencies may also benefit in that their 

review may be more streamlined and accurate as the States will 
82

not have to re-enter the data to assess the calculations and 

verify the data entry. Finally, another benefit of submitting 

these data to WebFIRE electronically is that these data will 

improve greatly the overall quality of the existing and new 

emissions factors by supplementing the pool of emissions test 

data upon which the emissions factor is based and by ensuring 

that data are more representative of current industry 

operational procedures. A common complaint we hear from 

industry and regulators is that emissions factors are outdated 

or not representative of a particular source category. 

Receiving and incorporating data for most performance tests will 

ensure that emissions factors, when updated, represent 

accurately the most current operational practices. In summary, 

receiving test data already collected for other purposes and 

using them in the emissions factors development program will 

save industry, State/local/Tribal agencies, and EPA time and 

money and work to improve the quality of emissions inventories 

and related regulatory decisions. 

As mentioned earlier, the electronic data base that will be 

used is EPA’s WebFIRE, which is a Web site accessible through 

EPA’s Technology Transfer Network (TTN). The WebFIRE Web site 

was constructed to store emissions test data for use in 

developing emissions factors. A description of the WebFIRE data 

base can be found at 
83

http://cfpub.epa.gov/oarweb/index.cfm?action=fire.main. 

The ERT will be able to transmit the electronic report 

through EPA’s Central Data Exchange (CDX) network for storage in 

the WebFIRE data base. Although ERT is not the only electronic 

interface that can be used to submit source test data to the CDX 

for entry into WebFIRE, it makes submittal of data very 

straightforward and easy. A description of the ERT can be found 

at http://www.epa.gov/ttn/chief/ert/ert_tool.html. 

VI. Impacts of the Proposed Standards 

A. What are the emissions, cost, economic, and non-air 

environmental impacts? 

 We estimate the proposed MACT standard will reduce mercury 

emissions from gold mine ore processing and production by 1,650 

lb/year from current emissions levels down to a level of 1,390 

lb/year post-MACT. The annual emissions expected after MACT (of 

1,390 lbs) represent a 73 percent reduction from 2007 emissions 

(5,000 pounds), more than 90 percent reduction from the 

emissions level in 2001 (about 23,000 pounds), and more than 96 

percent reduction from uncontrolled emissions levels (more than 

37,000 pounds). The capital cost of emission controls is 

estimated as $5 million with a total annualized cost of $2.3 

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

and recordkeeping are estimated as $1.0 to $1.3 million with a 

total annualized cost of $0.8 to $1.5 million per year, 
84

depending on the monitoring option that is chosen. The cost of 

compliance is estimated to be less than 0.3 percent of sales. 

We therefore believe that the economic impact on an affected 

company would be insignificant. Electricity consumption is 

expected to increase by about 2,100 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. Non-hazardous solid waste (spent carbon 

containing mercury that must be regenerated or disposed of) 

would increase by about 7 tons per year. 

B. What are the health benefits of reducing mercury emissions? 

B. What are the health benefits of reducing mercury emissions? 

Mercury is emitted to the air from various man-made and 

natural sources. These emissions transport through the 

atmosphere and eventually deposit to land or water bodies. This 

deposition can occur locally, regionally, or globally, depending 

on the form of mercury emitted and other factors such as the 

weather. The form of mercury emitted varies depending on 

source type and other factors. Available data indicate that the 

The majority of air eemissions from gold mine ore processing and 

production facilities are in the form of gaseous elemental 

mercury. This form of mercury , which can be transported very 

long distances, even globally, to regions far from the 

emissions source (becoming part of the global “pool”) before 
85

deposition occurs. However, this source category also emits 

some The remaining emissions are in the form of gaseous 

inorganic ionic mercury forms (such as mercuric chloride) , and 

smaller amounts of particulate bound mercuryor bound to emitted 

particles. These forms have a shorter atmospheric lifetime and 

can will deposit to land or water bodies closer to the emissions 

source. Furthermore, Eelemental mercury in the atmosphere can 

undergo transformation into ionic mercury, providing a 

significant pathway for deposition of emitted elemental mercury.

 Once deposited, the mercury form can change (primarily by 

microbial metabolism) to methyl mercury, which has the capacity 

to collect in organisms (bioaccumulate) and to concentrate up 

food chains (biomagnify), especially in the aquatic food chain 

(fish and marine mammals).

 

Potential exposure routes to mercury emissions include 

both inhalation and ingestion (e.g., through the consumption of 

fish containing mercury compounds). . The toxicity to humans 

and other organisms depends on the chemical form, the amount, 

the pathway of exposure, and the vulnerability of the person 

exposed. Chronic inhalation exposure to relatively low levels 

of mercury vapor is associated with various neurotoxic effects, 

including increases in memory disturbance and slight subjective 

and objective evidence of autonomic dysfunction. For example, 
86

studies of occupationally exposed humans have shown adverse 

effects on the central nervous system at long-term air levels of 

25-30 micrograms per cubic meter. Likewise, chronic ingestion 

exposures to mercury in fish can cause, among other things, 

developmental neurotoxic effects. Moreover, acute mercury 

inhalation exposure, to sufficiently elevated levels, is 

associated with nervous system damage, kidney damage, and 

gastrointestinal and respiratory effects. 

As mentioned previously, the gold mine ore processing 

and production source category emitted about 2.5 tons of mercury 

to the air in 2007 in the U.S. Based on the EPA’s National 

Emission Inventory, about 103 tons of mercury were emitted from 

all anthropogenic sources in the U.S. in 2005. Moreover, the 

United Nations has estimated that about 2100 tons were emitted 

worldwide by anthropogenic sources in 2005.3 We believe that 

total mercury emissions in the U.S. and globally in 2007 were 

about the same magnitude as in 2005. Therefore, we estimate 

that in 2007 the gold mine ore processing and production source 

category emitted about 2.5 percent of the total anthropogenic 

 

3

 United Nations Environment Programme/Arctic Monitoring and 

Assessment Program (UNEP/AMAP). Study on mercury-emitting 

sources, including emissions trends and cost and effectiveness 

of alternative control measures: “UNEP Paragraph 29 study.” 

2008. Available at: 

http://www.chem.unep.ch/mercury/Paragraph29/Zero%20Draft%20Repor

t%20March%208.doc
87

mercury emissions in the U.S. and about 0.12 percent of the 

global emissions.

As described above, mercury that has been emitted to the 

air eventually settles into water or onto land where it can be 

washed into water. Once deposited, certain microorganisms can 

change it into methylmercury, a highly toxic form that builds up 

in fish, shellfish and animals that eat fish. Fish and 

shellfish are the main sources of methylmercury exposure to 

humans. Methylmercury builds up more in some types of fish and 

shellfish than others. The levels of methylmercury in fish and 

shellfish depend on what they eat, how long they live and how 

high they are in the food chain. Mercury concentrations in fish 

vary widely. Most fish, including Llocal freshwater fish 

typically contain some methylmercury, which can be due, at least 

partly, to local emissions sources. However, the majority of 

fish species consumed in the U.S. are ocean species and the 

methylmercury concentrations in these species are primarily 

influenced by the global mercury pool. Potential exposure 

routes to mercury emissions include both inhalation and 

subsequent ingestion through the consumption of fish containing 

methylmercury. However, the primary route of exposure to 

mercury of potential concern due to emissions from industrial 

sources is generally indirectly through the consumption of fish 

containing methylmercury after the mercury has deposited to land 
88

and water bodies, changed form, and subsequently accumulated in 

fish through the process described above. 

Nevertheless, research shows that most people’s fish 

consumption does not cause a health concern. However, certain 

sub-populations aremay be at higher risk because of their 

routinely high consumption of fish and shellfish (e.g., tribal 

and other subsistence fishers and their families who rely 

heavily on fish for the majority of their diet). It has been 

demonstrated that high levels of methylmercury in the 

bloodstream of unborn babies and young children may harm the 

developing nervous system, making the child less able to think 

and learn. Moreover, mercury exposure at high levels can harm 

the brain, heart, kidneys, lungs, and immune system of people of 

all ages.4

 Overall, Tthis regulation will reduce mercury emissions by 

about 1,650 pounds per year from current levels and, therefore, 

contribute to reductions in mercury exposures and health 

effects. 

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, 

 

4

 For more information see http://www.epa.gov/mercury/about.htm. 
89

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

 The information collection requirements in this proposed 

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 

proposed 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 proposed NESHAP would require applicable one-time 

notifications according to the NESHAP General Provisions. In 

addition, owners or operators must submit annual notifications 
90

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 would be required. 

 The average annual burden for this information collection 

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

total 4,225 labor hours per year at a cost of approximately 

$213,726 per year for the 21 facilities that would be subject to 

this proposed rule, or approximately 201 hours per year per 

facility. Capital costs are estimated as $1.3 million, 

operation and maintenance costs are estimated as $65,000 per 

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

estimated as $256,000 per year for this proposed 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. 

 To comment on the Agency’s need for this information, the 

accuracy of the provided burden estimates, and any suggested 

methods for minimizing respondent burden, EPA has established a 
91

public docket for this rule, which includes this ICR, under 

Docket ID number EPA-HQ-OAR-2010-0239. 

 Submit any comments related to the ICR to EPA and OMB. See 

ADDRESSES section at the beginning of this notice for where to 

submit comments to EPA. Send comments to OMB at the Office of 

Information and Regulatory Affairs, Office of Management and 

Budget, 725 17th Street, NW, Washington, DC 20503, Attention: 

Desk Office for EPA. Since OMB is required to make a decision 

concerning the ICR between 30 and 60 days after [Insert date of 

publication in the Federal Register.], a comment to OMB is best 

assured of having its full effect if OMB receives it by [Insert 

date 30 days after publication in the Federal Register.]. The 

final rule will respond to any OMB or public comments on the 

information collection requirements contained in this proposal. 

C. Regulatory Flexibility Act

 The Regulatory Flexibility Act generally requires an agency 

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 proposed 
92

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 proposed 

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

a significant economic impact on a substantial number of small 

entities. This proposed rule is estimated to impact about 21 

gold mine ore processing and production facilities, none of 

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

to small entities from this proposed rule. Although this 

proposed 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 proposed rule. 

 Although this proposed 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 proposed rule 
93

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 proposed standards were developed 

based on information obtained from industry representatives in 

our surveys, consultation with business representatives and 

their trade association and other stakeholders. We continue to 

be interested in the potential impacts of this proposed rule on 

small entities and welcome comments on issues related to such 

impacts. 

D. Unfunded Mandates Reform Act

 This proposed rule does not contain a federal mandate that 

may result in expenditures of $100 million or more for state, 

local, and tribal governments, in the aggregate, or to the 

private sector in any one year. This proposed rule is not 

expected to impact state, local, or tribal governments. The 

nationwide annualized cost of this proposed rule for affected 

industrial sources is $3.8 million/yr. Thus, this proposed rule 

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

the Unfunded Mandates Reform Act (UMRA). 

 This proposed rule is also not subject to the requirements 

of section 203 of UMRA because it contains no regulatory 
94

requirements that might significantly or uniquely affect small 

governments. This proposed rule will not apply to such 

governments and will not impose any obligations upon them. 

E. Executive Order 13132: Federalism

 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 proposed rule does not impose any requirements on 

state and local governments. Thus, Executive Order 13132 does 

not apply to this action. 

In the spirit of Executive Order 13132, and consistent with 

EPA policy to promote communications between EPA and State and 

local governments, EPA specifically solicits 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 

proposed rule imposes no requirements on tribal governments; 

thus, Executive Order 13175 does not apply to this action. EPA 

specifically solicits additional comment on this proposed action 

from tribal officials. 
95

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 

Executive Order 13045 because it is based solely on technology 

performance. 

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 proposed rule will not likely have any significant adverse 

energy effects because energy consumption would increase by only 

2,100 megawatt-hours per year. 

I. National Technology Transfer 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 
96

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

specifications, test methods, sampling procedures, business 

practices) that are developed or adopted by voluntary consensus 

standards bodies. NTTAA directs EPA to provide Congress, 

through OMB, explanations when the Agency decides not to use 

available and applicable VCS. 

 This proposed rulemaking involves technical standards. EPA 

proposes 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. 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, 29, 30A, 30B, Method 7471A, “Mercury 

in Solid or Semisolid Waste (Manual Cold-Vapor Technique),” and 

ASTM D6784–02, “Standard Test Method for Elemental, Oxidized, 
97

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 proposed 

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 proposed rule. 

 EPA welcomes comments on this aspect of this proposed 

rulemaking and, specifically, invites the public to identify 

potentially-applicable voluntary consensus standards and to 

explain why such standards should be used in this regulation. 

 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 proposed 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 
98

extent practicable and permitted by law, to make environmental 

justice part of their mission by identifying and addressing, as 

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 proposed 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. This proposed rule is expected to 

reduce mercury emissions from gold mine ore processing and 

production facilities and thus decrease the amount of such 

emissions to which all affected populations are exposed.
National Emission Standards for Hazardous Air Pollutants: Gold 

Mine Ore Processing and Production Area Source Category 

Page 99 of 136 

List of Subjects in 40 CFR Part 63

 Environmental protection, Air pollution control, Hazardous 

substances, Incorporations by reference, Reporting and 

recordkeeping requirements. 

___________ 

Dated: 

____________________________ 

Lisa P. Jackson, 

Administrator. 
100

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

the Code of Federal Regulations is proposed to be 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 Section 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. 

* * * * * 
101

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. 

* * * * * 
102

 (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 

Category 

Applicability and Compliance Dates 
103

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 

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” at a 
104

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 [INSERT DATE OF PUBLICATION OF THIS PROPOSED RULE IN THE 

FEDERAL REGISTER]. 

 (2) An affected source is new if you commenced 

construction or reconstruction of the affected source after 

[INSERT DATE OF PUBLICATION OF THIS PROPOSED RULE IN THE FEDERAL 

REGISTER]. 

 (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 

must comply with the applicable provisions of this subpart no 

later than 2 years after the date of publication of the final 

rule in the Federal Register. 

 (b) If you start up a new affected source on or before the 

date of publication of the final rule in the Federal Register, 
105

you must comply with the provisions of this subpart no later 

than the date of publication of the final rule in the Federal 

Register. 

 (c) If you start up a new affected source after the date 

of publication of the 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 149 pounds of mercury per million tons of ore 

processed. 

 (b) For existing carbon processes, you must emit no more 

than 2.6 pounds of mercury per ton of concentrate processed. 

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

must emit no more than 0.25 pounds of mercury per ton of 

concentrate processed. 

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

more than 149 pounds of mercury per million tons of ore 

processed. 

 (e) For new carbon processes, you must either: 

 (1) Emit no more than 0.14 pounds of mercury per ton of 

concentrate processed, or 

 (2) Achieve a 97 percent reduction in mercury emissions as 
106

measured before and after the mercury emission control devices. 

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

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

processed. 

(g) 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 

existing affected sources according to the requirements in 

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

testing must be repeated annually thereafter (i.e., once every 

four successive calendar quarters). 

(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 A-
107

1), 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 

the moisture content of the stack gas. 

(v) Method 29 (40 CFR part 60, appendix A-8), ASTM D6784–

02, “Standard Test Method for Elemental, Oxidized, ParticleBound and Total Mercury in Flue Gas Generated from Coal-Fired 

Stationary Sources (Ontario Hydro Method)” (incorporated by 

reference – see §63.14), Method 30A (40 CFR part 60, appendix A8), or Method 30B (40 CFR part 60, appendix A-8) to determine 

the concentration of mercury. If you use Method 29, the acetone 

rinse procedures in Section 8.2.6 of the method must be followed 

and are not optional (i.e., quantitative removal of particulate 

matter and any condensate from the sampling apparatus (probe 

nozzle, fitting, holder) and front half of the filter holder 

must be performed using acetone). 

(vi) The absence of cyclonic flow must be determined prior 

to or during the test. For retorts and other narrow stacks 

where sampling is done at a single point with a standard pitot 
108

tube, a "null" check must be performed prior to sampling. 

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

each performance test of each process unit. Each test run must 

be conducted for at least two hours and collect a minimum sample 

volume of 1.7 dry standard cubic meters (60 dry standard cubic 

feet). 

(3) Tests must be conducted under operating conditions 

(including process or production throughputs) that are based on 

representative performance. Record and report the process 

throughput for each test run. 

(4) Calculate the mercury emission rate 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 

milligrams per dry standard cubic meter (mg/dscm); 

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

standard cubic feet per hour; and 

K = conversion factor from mg/dscm to pounds per dry 

standard cubic foot, 6.23 x 10-8. 

(5) Monitor and record the number of hours 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 

the 6-month period following the compliance date by multiplying 
109

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

of hours each process unit operated during the 6-month period. 

After the initial 6 months following the compliance date, 

determine the annual mercury mass emissions 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. 

(7) For compliance determinations following the initial 

compliance test for new and existing sources, determine the 

total mercury mass emissions for each process unit for the 12-

month period preceding the performance test by multiplying the 

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

hours each process unit operated during the 12-month period 

preceding the completion of the performance tests. 

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

appropriate weight measurement device or densitometers and 

volumetric flow meters to measure ore throughput for each 

roasting operation and autoclave and calculate hourly, daily and 

monthly totals in tons of as fed ore. 

(i) Measure the weight or the density and volumetric flow 
110

rate of the oxidized ore slurry as it exits the roaster 

oxidation circuit and before the carbon-in-leach tanks. 

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

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

(9) Measure the weight of concentrate processed (by 

electrowinning, Merrill Crowe process, gravity feed, or other 

methods) using weigh scales for each batch prior to retorting. 

The concentrate must be weighed in the same state and condition 

as it is when fed to the retort. For facilities without 

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 

permitting authority upon request. You must determine, record, 

and maintain a record of the accuracy of the measuring systems 
111

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 and for noncarbon concentrate processes on a daily and monthly basis. 

(12) Calculate the emissions from each new and existing 

affected source for the 6-month period following the compliance 

date in pounds of mercury per ton of process input using the 

procedures in paragraphs (a)(12)(i) through (iii) of this 

section to determine initial compliance with the emission 

standards in §63.11645. After the initial 6-month 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 from all roasting operations and 

autoclaves during the initial 6-month period following the 

compliance date by the sum of the total amount of gold mine ore 

processed in these process units during the 6-month period 

following the compliance date. 

(ii) For carbon processes, divide the sum of mercury mass 

emissions from all carbon kilns, preg tanks, electrowinning, 

retorts, and melt furnaces during the initial 6-month period 

following the compliance date by the total amount of concentrate 

processed in these process units during the initial 6-month 
112

period following the compliance date. 

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

of mercury mass emissions from retorts and melt furnaces during 

the initial 6-month period following the compliance date by the 

total amount of concentrate processed in these process units 

during the 6-month period following the compliance date. 

(13) After the initial compliance test, calculate the 

emissions from each new and existing affected source for each 

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 (iii) 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 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 that 

12-month period. 

(ii) For carbon processes, divide the sum of mercury mass 

emissions from all carbon kilns, preg tanks, electrowinning, 

retorts, and melt furnaces in the 12-month period preceding a 

compliance test by the total amount of concentrate processed in 

these process units in that 12-month period. 

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

of mercury mass emissions from retorts and melt furnaces in the 
113

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

of concentrate processed in these process units in that 12-month 

period. 

(b) If you have a new carbon processes affected source and 

elect to comply with the percent reduction standard in 

§63.11645(e)(2), you must perform annual tests of the inlet and 

outlet to each control device used in the new affected source 

and calculate emissions at the inlet and outlet using the 

methods and procedures in paragraphs (a)(1) through (7) of this 

section. The sampling and analysis of inlet emissions for 

retorts must be performed following the mercury condenser and 

before the carbon adsorber. Calculate the percent reduction in 

mercury emissions based on the difference in emission rates at 

the inlet and outlet to each control device. Perform compliance 

determination for the initial 6-month period following the 

compliance date using the procedures in paragraph (a)(6) of this 

section. Perform compliance determinations annually following 

the initial 6-month period using the procedures in paragraph 

(a)(7) of this section. 

(c) 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. 
114

§63.11647 What are my monitoring requirements?

(a) Except as provided in paragraph (a)(4) of this section, 

you must monitor each roaster for mercury emissions using one of 

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

establish operating limits for mercury concentration as 

described in paragraph (a)(3) of this section. 

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

for mercury concentration using EPA Performance Specification 

12B each week and maintain the daily average concentration below 

the operating limit established in paragraph (a)(3) of this 

section. 

(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 30 days using a 

shorter sampling duration. 

(ii) If you measure a daily average concentration above 

the operating limit, you must take corrective action and correct 

the problem within 48 hours of the exceedance or stop the feed 

of ore to the roaster, and report the exceedance as a deviation. 
115

(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. 

(i) You must continuously monitor the daily average 

mercury concentration from the roaster and maintain the daily 

average concentration below the operating limit established in 

paragraph (a)(3) of this section. If you measure a daily 

average concentration above the operating limit, you must take 

corrective action and correct the problem within 48 hours of the 

exceedance or stop the feed of ore to the roaster, and report 

the exceedance as a deviation. 

(ii) 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 

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 
116

CEMS. 

(3) 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) or (2) of this section 

concurrently while you are also doing your annual compliance 

performance stack test according to the procedures in 

§63.11646(a). 

OLR = Ctest * (149/CT) (Eq 2) 

where 

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) during the 

annual performance stack test (in micrograms per 

cubic meter); 

149 = emission limit for ore pretreatment processes (in 

lb/ million tons of ore); 

CT = compliance test results for ore pretreatment 

processes (in lb/ million tons of ore). 

(4) 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) or (2) 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. 
117

(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. 

(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. 

(iii) You must continue to perform annual compliance tests 

of the roaster stack as required in §63.11646(a). In addition, 

if the mercury concentration in the ore processed in the roaster 

increases to a level higher than any mercury concentration 

measured in the previous 12 months, you must perform a 

compliance test within 30 days of the first day that the ore 

with higher mercury levels is processed to determine whether the 

mercury emissions are still below 10 lbs per million tons of 

ore. If any subsequent compliance tests indicates that the 

roaster is emitting more than 10 pounds of mercury per million 

tons of ore input, then you must implement the monitoring 
118

required in paragraphs (a)(1) or (2) of this section within 30 

days. 

(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)(4) of this section, you must 

establish operating parameters for scrubber liquor flow, 

scrubber pressure drop and scrubber inlet gas temperature and 

monitor these parameters. Monitor the scrubber liquor flow, 

scrubber pressure drop and scrubber inlet gas temperature during 

each run of your initial compliance test. The minimum operating 

rate for scrubber liquor flow and pressure drop are the lowest 

values during any run of the initial compliance test, and your 

maximum scrubber inlet temperature limit is the highest measured 

during any run of the initial compliance test. Subsequently, 

you must monitor the scrubber liquor flow, scrubber pressure 

drop and scrubber inlet gas temperature hourly and maintain the 

scrubber liquor flow and scrubber pressure drop at or above the 

operating parameters established during the initial compliance 

test and maintain the inlet gas temperature below the operating 

parameters established during the initial compliance test. 

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

mercury control system that choose to monitor for mercury 
119

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

section or that qualify for and follow the requirements in 

paragraph (a)(4) of this section, you must establish operating 

parameters for mercuric ion and chloride ion concentrations or 

for oxidation reduction potential and pH using the procedures in 

either paragraph (c)(1) or (2) of this section. 

(1) Establish the mercuric ion concentration and chloride 

ion concentration range for each calomel-based mercury control 

system. The mercuric ion concentration and chloride ion 

concentration for each calomel-based mercury control system must 

be based on the manufacturer’s specifications. Alternatively, 

the mercuric ion concentration and chloride ion concentration 

range for each calomel-based mercury control system may be 

approved by your permitting authority. Measure the 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 four times 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 calomel-
120

based mercury control system must be based on the manufacturer’s 

specifications. Alternatively, the oxidation reduction 

potential and pH range for each calomel-based mercury control 

system may be approved 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 an operating limit or 

range in paragraphs (b) or (c) of this section, you must take 

corrective action and bring the system operations back into the 

specified operational range or limit within 45 minutes or 

commence shutdown of the roaster. 

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

for approval to change the operating limits established under 

paragraph (a)(3) of this section for the monitoring required in 

paragraph (a)(1) or (2) 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 
121

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), 

(2), or (3) of this section. 

(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 one week that includes the period of 

the annual performance test. 

(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 

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 limit 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 
122

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

50 percent of the operating limit, begin weekly sampling and 

analysis. When the mercury concentration reaches 80 percent of 

the operating limit, replace the carbon in the carbon adsorber 

within 30 days. 

(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 top 

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. Calculate an 

average carbon loading from the two 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. 

(3) Calculate the change out rate for the carbon in the 

carbon adsorber based on the carbon lifetime as determined from 

at least 2 years of data for the process unit from following the 

procedures in paragraphs (f)(1) or (2) of this section. You 

must submit supporting data and request approval from your 
123

permitting authority to periodically change out the carbon 

instead of monitoring. After approval from your permitting 

authority, change out the carbon in the carbon adsorber no less 

frequently than the established lifetime. If you change the 

process or inputs in such a manner that mercury emissions might 

increase (e.g., increase throughput), you must re-establish the 

change out period based on two years of historical data as 

described in this paragraph. 

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

to the carbon adsorber for each autoclave, carbon kiln, melt 

furnace, and retort equipped with a carbon adsorber during the 

annual performance test required in §63.11646(a) and establish a 

maximum value for the inlet temperature. 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. Continuously monitor the 

inlet temperature thereafter. If an hourly average 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 to reduce the temperature back below 
124

the temperature operating limit and again measure the outlet 

concentration 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. 

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

affected source, you must monitor the water flow rate and 

pressure drop during the performance test required in 

§63.11646(a) and establish a minimum value as the operating 

limit based on either the lowest average value during any test 

run or as no lower than 10 percent of the average value measured 

during the test. You must continuously monitor the water flow 

rate and pressure drop and take corrective action within 24 

hours if any daily average is less than the operating 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. 

§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 
125

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 

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. 
126

(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 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 affected source to minimize 

emissions in accordance with §63.11646(c), including actions 

taken to correct a malfunction. 

 (e) You must keep the records specified in paragraphs 

(e)(1) through (3) of this section. 

 (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, 

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. 
127

 (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 (e.g., 

VE) to the time that monitoring indicated proper operation; and 

(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 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 
128

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 

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 
129

chloride to form mercurous chloride (calomel). Sometimes these 

scrubbers are also referred to as “mercury scrubbers.” 

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 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 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 retorts, or for facilities without retorts, as the 

input to melt furnaces before any drying takes place. For 

facilities without 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 
130

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 

facility engaged in the processing of gold mine ore that uses 

any of the following processes: roasting operations, 

autoclaves, carbon kilns, preg tanks, electrowinning, retorts, 

or melt furnaces. A facility that produces primarily copper 

(where copper is 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. 

Melt furnace means a furnace (typically a crucible furnace) 

that is used for smelting the gold-bearing material recovered 

from retorting, or the gold-bearing material from 
131

electrowinning, the Merrill-Crowe process or other processes for 

facilities without retorts. 

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 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 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 

for pregnant solution, which is the cyanide solution that 

contains gold-cyanide complexes that is generated from leaching 

gold ore with cyanide solution. 
132

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. 

Retort means a vessel that is operated under a partial 

vacuum at approximately 1,100 to 1,300oF to remove mercury and 

moisture from the gold bearing sludge material that is recovered 

from electrowinning, the Merrill-Crowe process or other 

processes. Retorts are usually equipped with condensers that 

recover liquid mercury during the processing. 

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 
133

this subpart is delegated to your state, local, or tribal 

agency. 

 (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 
134

recordkeeping/reporting. A “major change to 

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 Abbreviations Yes 

§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 Startup, Shutdown and No Subpart 
135

(ii), (e)(3), 

and(f)(1) 

Malfunction 

Requirements (SSM) 

EEEEEEE 

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 Requirements Yes 

§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 
136

§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