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ENVIRONMENTAL PROTECTION AGENCY

Veterans Affairs Department

CFR Citation: 40 CFR Part 63

RIN ID: RIN 2060-A167 and 2060-A168

OAR ID: [OAR-2002-0054 and OAR-2002-0055, FRL-7459-9]

NOTICE: Part II

DOCUMENT ACTION: Final rule.

SUBJECT CATEGORY: National Emission Standards for Hazardous Air Pollutants for Brick and Structural Clay Products Manufacturing; and National Emission Standards for Hazardous Air Pollutants for Clay Ceramics Manufacturing

EFFECTIVE DATES: The final rule is effective May 16, 2003.

DOCUMENT SUMMARY: This action promulgates national emission standards for hazardous air pollutants (NESHAP) for new and existing sources at brick and structural clay products (BSCP) manufacturing facilities and NESHAP for new and existing sources at clay ceramics manufacturing facilities. This action will implement section 112(d) of the Clean Air Act (CAA) by requiring major sources to meet hazardous air pollutant (HAP) emission standards reflecting the application of the maximum achievable control technology (MACT). The two subparts will protect air quality and promote the public health by reducing emissions of several of the HAP listed in section 112(b)(1) of the CAA. The rules will reduce HAP emissions from existing sources by 2,300 tons per year nationwide, with hydrogen fluoride (HF) and hydrogen chloride (HCl) accounting for 2,290 tons per year (99.6 percent) of the total HAP emissions reductions from existing sources. The associated metals (antimony, arsenic, beryllium, cadmium, chromium, cobalt, mercury, manganese, nickel, lead, and selenium) reductions from existing sources account for approximately 6 tons per year nationwide (0.4 percent). Exposure to these substances has been demonstrated to cause adverse health effects such as irritation of the lung, skin, and mucus membranes, effects on the central nervous system, and kidney damage. The EPA has classified three of the HAP as known human carcinogens, four as probable human carcinogens, and one as a possible human carcinogen. We estimate that the two subparts will reduce nationwide emissions of HAP from these facilities by approximately 2,100 megagrams per year (Mg/yr)(2,300 tons per year (tpy)), a reduction of approximately 35 percent from the current level of emissions.

SUMMARY: Environmental Protection Agency,

SUPPLEMENTAL INFORMATION

Regulated Entities. Entities potentially regulated by this action are those industrial facilities that manufacture BSCP and clay ceramics. Brick and structural clay products manufacturing is classified under Standard Industrial Classification (SIC) codes 3251, Brick and Structural Clay Tile; 3253, Ceramic Wall and Floor Tile; and 3259, Other Structural Clay Products. The North American Industry Classification System (NAICS) codes for BSCP manufacturing are 327121, Brick and Structural Clay Tile; 327122, Ceramic Wall and Floor Tile Manufacturing; and 327123, Other Structural Clay Products. Clay ceramics manufacturing is classified under SIC codes 3253, Ceramic Wall and Floor Tile; and 3261, Vitreous Plumbing Fixtures (Sanitaryware). The NAICS codes for clay ceramics manufacturing are 327122, Ceramic Wall and Floor Tile Manufacturing; and 327111, Vitreous China Plumbing Fixture and China and Earthenware Bathroom Accessories Manufacturing. Regulated categories and entities are shown in Table 1 of this preamble.
Table 1.Regulated Categories and Entities
Examples of potentially Category SIC NAICS regulated entities Industrial..................... 3251 327121 Brick and structural clay tile manufacturing facilities (BSCP NESHAP)
Industrial..................... 3253 327122 Ceramic wall and floor tile manufacturing facilities (Clay Ceramics NESHAP) and extruded tile manufacturing facilities (BSCP NESHAP).
Industrial..................... 3259 327123 Other structural clay products manufacturing facilities (BSCP NESHAP)
Industrial..................... 3261 327111 Vitreous plumbing fixtures
(sanitaryware) manufacturing facilities (Clay Ceramics NESHAP).

This table is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be regulated by this action. To determine whether your facility is regulated by this action, you should examine the applicability criteria in Sec. 63.8385 of today's final BSCP rule and Sec. 63.8535 of today's final clay ceramics rule. If you have any questions regarding the applicability of this action to a particular entity, consult the person listed in the preceding FOR FURTHER INFORMATION CONTACT section.

Electronic Docket (EDocket). The EPA has established official public dockets for this action under Docket ID No. OAR20020054 for the final BSCP rule and Docket ID No. OAR20020055 for the final clay ceramics rule. The official public dockets are the collection of materials that is available for public viewing at the EPA Docket Center (Air Docket), EPA West, Room B102, 1301 Constitution Avenue, NW., Washington, DC 20460. The Docket Center is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The telephone number for the Reading Room is (202) 5661744, and the telephone number for the Air Docket is (202) 5661742. A reasonable fee may be charged for copying docket materials.

Electronic Access. Electronic versions of the public dockets are available through EPA's electronic public docket
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and comment system, EPA Dockets. You may use EPA Dockets at http://www.epa.gov/edocket/ to view public comments, access the indexes of the
contents of the official public dockets, and to access those documents in the public dockets that are available electronically. Once in the system, select ``search'' and key in the appropriate docket identification number. Although not all docket materials may be available electronically, you may still access any of the publicly available docket materials through the docket facility identified in this document.

Worldwide Web (WWW). In addition to being available in the dockets, an electronic copy of today's document also will be available on the WWW. Following the Administrator's signature, a copy of this action will be posted at www.epa.gov/ttn/oarpg on EPA's Technology Transfer Network (TTN) policy and guidance page for newly proposed or promulgated rules. The TTN provides information and technology exchange in various areas of air pollution control. If more information regarding the TTN is needed, call the TTN HELP line at (919) 5415384.

Judicial Review. Under section 307(b)(1) of the CAA, judicial review of the final rule is available only by filing a petition for review in the U.S. Court of Appeals for the District of Columbia Circuit by July 15, 2003. Under section 307(d)(7)(B) of the CAA, only an objection to the final rule that was raised with reasonable specificity during the period for public comment can be raised during judicial review. Moreover, under section 307(b)(2) of the CAA, the requirements established by the final rule may not be challenged separately in any civil or criminal proceedings brought by EPA to enforce the requirements.

Outline. The information presented in this preamble is organized as follows:

I. Background

A. What Is the Source of Authority for Development of NESHAP?

B. What Criteria Are Used in the Development of NESHAP?

C. How Were the Final Rules Developed?

D. What Are the Health Effects of Pollutants Emitted From the Brick and Structural Clay Products Manufacturing and Clay Ceramics Manufacturing Source Categories?
II. Summary of Responses to Major Comments and Changes to the Brick and Structural Clay Products Manufacturing Proposed NESHAP

A. Air Pollution Control Devices

B. Affected Source

C. Existing Source MACT

D. New Source MACT

E. Cost and Economic Impacts

F. Test Data and Emission Limits

G. Monitoring Requirements

H. Startup, Shutdown, and Malfunction

I. RiskBased Approaches
III. Summary of the Final Brick and Structural Clay Products Manufacturing NESHAP

A. What Source Category Is Regulated by the Final Rule?

B. What Are the Affected Sources?

C. When Must I Comply With the Final Rule?

D. What Are the Emission Limits?

E. What Are the Operating Limits?

F. What Are the Performance Test and Initial Compliance Requirements?

G. What Are the Continuous Compliance Requirements?

H. What Are the Notification, Recordkeeping, and Reporting Requirements?
IV. Summary of Environmental, Energy, and Economic Impacts for the Final Brick and Structural Clay Products Manufacturing NESHAP

A. What Are the Air Quality Impacts?

B. What Are the Water and Solid Waste Impacts?

C. What Are the Energy Impacts?

D. Are There any Additional Environmental and Health Impacts?

E. What Are the Cost Impacts?

F. What Are the Economic Impacts?
V. Summary of Responses to Major Comments and Changes to the Clay Ceramics Manufacturing Proposed NESHAP

A. Affected Source

B. Existing Source MACT

C. New Source MACT

D. Cost and Economic Impacts

E. Test Data and Emission Limits

F. Monitoring Requirements

G. Startup, Shutdown, and Malfunction
VI. Summary of the Final Clay Ceramics Manufacturing NESHAP

A. What Source Category Is Regulated by the Final Rule?

B. What Are the Affected Sources?

C. When Must I Comply With the Final Rule?

D. What Are the Emission Limits?

E. What Are the Operating Limits?

F. What Are the Work Practice Standards?

G. What Are the Performance Test and Initial Compliance Requirements for Sources Subject to Emission Limits?

H. What Are the Initial Compliance Requirements for Sources Subject to a Work Practice Standard?

I. What Are the Continuous Compliance Requirements for Sources Subject to Emission Limits?

J. What Are the Continuous Compliance Requirements for Sources Subject to a Work Practice Standard?

K. What Are the Notification, Recordkeeping, and Reporting Requirements for Sources Subject to Emission Limits?

L. What Are the Notification, Recordkeeping, and Reporting Requirements for Sources Subject to a Work Practice Standard? VII. Summary of Environmental, Energy, and Economic Impacts for the Final Clay Ceramics Manufacturing NESHAP

A. What Are the Air Quality Impacts?

B. What Are the Water and Solid Waste Impacts?

C. What Are the Energy Impacts?

D. Are there any Additional Environmental and Health Impacts?

E. What Are the Cost Impacts?

F. What Are the Economic Impacts?

VIII. Statutory and Executive Order Reviews

A. Executive Order 12866, Regulatory Planning and Review

B. Paperwork Reduction Act

C. Regulatory Flexibility Act

D. Unfunded Mandates Reform Act

E. Executive Order 13132, Federalism

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

G. Executive Order 13045, Protection of Children From Environmental Health & Safety Risks

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

I. National Technology Transfer and Advancement Act

J. Congressional Review Act
I. Background
A. What Is the Source of Authority for Development of NESHAP?

Section 112 of the CAA requires us to list categories and subcategories of major and area sources of HAP and to establish NESHAP for the listed source categories and subcategories. Clay products manufacturing was listed as a category of major sources on the initial source category list published in the Federal Register on July 16, 1992 (57 FR 31576). In the July 22, 2002 Federal Register notice (67 FR 47894) that proposed NESHAP for BSCP manufacturing and clay ceramics manufacturing, the clay products manufacturing source category was replaced by the BSCP manufacturing source category and the clay ceramics manufacturing source category. Today's action contains final rules for the two source categories. Major sources of HAP are those stationary sources or groups of stationary sources that are located within a contiguous area and under common control that emit or have the potential to emit considering controls, in the aggregate, 9.07 Mg/yr (10 tpy) or more of any one HAP or 22.68 Mg/yr (25 tpy) or more of any combination of HAP. Area sources are those stationary sources that are not major sources.

B. What Criteria Are Used in the Development of NESHAP?

Section 112 of the CAA requires that we establish NESHAP for the control of HAP from both new and existing major
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sources. The CAA requires the NESHAP to reflect the maximum degree of reduction in emissions of HAP that is achievable. This level of control is commonly referred to as MACT.

The MACT floor is the minimum control level allowed for NESHAP and is defined under section 112(d)(3) of the CAA. In essence, the MACT floor ensures that the standards are set at a level that assures that all major sources achieve the level of control at least as stringent as that already achieved by the bettercontrolled and loweremitting sources in each source category or subcategory. For new sources, the MACT floor cannot be less stringent than the emission control that is achieved in practice by the bestcontrolled similar source. The MACT standards for existing sources can be less stringent than standards for new sources, but they cannot be less stringent than the average emission limitation achieved by the bestperforming 12 percent of existing sources in the category or subcategory for which the Administrator has emissions information (or the bestperforming 5 sources for which the Administrator has or could reasonably obtain emissions information for categories or subcategories with fewer than 30 sources).

In developing MACT, we also consider control options that are more stringent than the floor. We may establish standards more stringent than the floor based on the consideration of cost of achieving the emissions reductions, any health and environmental impacts, and energy requirements.

C. How Were the Final Rules Developed?

We proposed standards for BSCP manufacturing and clay ceramics manufacturing on July 22, 2002 (67 FR 47894). The preamble for the proposed standards described the rationale for the proposed standards. Public comments were solicited at the time of proposal. The public comment period lasted from July 22, 2002 to September 20, 2002. Industry representatives, regulatory agencies, environmental groups, and the general public were given the opportunity to comment on the proposed rules and to provide additional information during the public comment period. We also offered at proposal the opportunity for oral presentation of data, views, or arguments concerning the proposed rules. A public hearing on the proposed BSCP rule was held on August 21, 2002, during which 21 presentations were made. Following the public hearing, we met with representatives of industry and environmental groups on several occasions.

We received a total of 80 public comment letters on the proposed BSCP rule and 9 public comments letters on the proposed clay ceramics rule. Comments were submitted by industry trade associations, BSCP and clay ceramics manufacturing companies, State regulatory agencies and their representatives, and environmental groups. Today's final rules reflect our consideration of all of the comments received. Major public comments on the proposed rules, along with our responses to those comments, are summarized in this preamble.
D. What Are the Health Effects of Pollutants Emitted From the Brick and Structural Clay Products Manufacturing and Clay Ceramics Manufacturing Source Categories?

Today's proposed rules protect air quality and promote the public health by reducing emissions of some of the HAP listed in section 112(b)(1) of the CAA. Emissions data collected during development of the proposed rules show that HF, HCl, and small amounts of metals (antimony, arsenic, beryllium, cadmium, chromium, cobalt, mercury, manganese, nickel, lead, and selenium) are emitted from BSCP and clay ceramics manufacturing facilities. Exposure to these HAP is associated with a variety of adverse health effects. These adverse health effects include chronic health disorders (e.g., irritation of the lung, skin, and mucus membranes, effects on the central nervous system, and damage to the kidneys), and acute health disorders (e.g., lung irritation and congestion, alimentary effects such as nausea and vomiting, and effects on the kidney and central nervous system). We have classified three of the HAP as human carcinogens, four as probable human carcinogens, and one as a possible human carcinogen. We do not know the extent to which the adverse health effects described above occur, or if any adverse effects occur, in the populations surrounding these facilities. However, to the extent the adverse effects do occur, today's proposed rules would reduce emissions and subsequent exposures. The majority of the emissions reductions from this rule are HF (1900 tons per year nationwide) and HCl (390 tons per year nationwide), while the rule will only reduce emissions of the HAP metals listed below by a small amount (approximately 6 tons nationwide per year).

1. Hydrogen Fluoride

Acute (shortterm) inhalation exposure to gaseous HF can cause severe respiratory damage in humans, including severe irritation and pulmonary edema. Chronic (longterm) exposure to fluoride at low levels has a beneficial effect of dental cavity prevention and may also be useful for the treatment of osteoporosis. Exposure to higher levels of fluoride may cause dental fluorosis or mottling, while very high exposures through drinking water or air can result in crippling skeletal fluorosis. One study reported menstrual irregularities in women occupationally exposed to fluoride. We have not classified HF for carcinogenicity.

2. Hydrogen Chloride

Hydrogen chloride, also called hydrochloric acid, is corrosive to the eyes, skin, and mucous membranes. Acute (shortterm) inhalation exposure may cause eye, nose, and respiratory tract irritation and inflammation and pulmonary edema in humans. Chronic (longterm) occupational exposure to HCl has been reported to cause gastritis, bronchitis, and dermatitis in workers. Prolonged exposure to low concentrations may also cause dental discoloration and erosion. No information is available on the reproductive or developmental effects of HCl in humans. In rats exposed to HCl by inhalation, altered estrus cycles have been reported in females and increased fetal mortality and decreased fetal weight have been reported in offspring. We have not classified HCl for carcinogenicity.

3. Antimony

Acute (shortterm) exposure to antimony by inhalation in humans results in effects on the skin and eyes. Respiratory effects, such as inflammation of the lungs, chronic bronchitis, and chronic emphysema, are the primary effects noted from chronic (longterm) exposure to antimony in humans via inhalation. Human studies are inconclusive regarding antimony exposure and cancer, while animal studies have reported lung tumors in rats exposed to antimony trioxide via inhalation. Effects of oral exposure to antimony are not well described, but a single study has reported decreased longevity and changes in serum glucose and cholesterol in rats. We have not classified antimony for carcinogenicity.

4. Arsenic

Acute (shortterm) highlevel inhalation exposure to arsenic dust or fumes has resulted in gastrointestinal effects (nausea, diarrhea, abdominal
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pain), and central and peripheral nervous system disorders. Chronic (longterm) inhalation exposure to inorganic arsenic in humans is associated with irritation of the skin and mucous membranes. Human data suggest a relationship between inhalation exposure of women working at or living near metal smelters and an increased risk of reproductive effects, such as spontaneous abortions. Inorganic arsenic exposure in humans by the inhalation route has been shown to be strongly associated with lung cancer, while ingestion of inorganic arsenic in humans has been linked to a form of skin cancer and also to bladder, liver, and lung cancer. We have classified inorganic arsenic as a Group A, human carcinogen.

5. Beryllium

Acute (shortterm) inhalation exposure to high levels of beryllium has been observed to cause inflammation of the lungs or acute pneumonitis (reddening and swelling of the lungs) in humans; after exposure ends, these symptoms may be reversible. Chronic (longterm) inhalation exposure of humans to beryllium has been reported to cause chronic beryllium disease (berylliosis), in which granulomatous (noncancerous) lesions develop in the lung. Inhalation exposure to beryllium has been demonstrated to cause lung cancer in rats and monkeys. Human studies are limited, but suggest a causal relationship between beryllium exposure and an increased risk of lung cancer. Oral exposure to beryllium was found to cause stomach lesions in dogs, but effects on humans are not welldescribed. We have classified beryllium as a Group B1, probable human carcinogen, when inhaled; data are inadequate to determine whether beryllium is carcinogenic when ingested.

6. Cadmium

The acute (shortterm) effects of cadmium inhalation in humans consist mainly of effects on the lung, such as pulmonary irritation. Chronic (longterm) inhalation or oral exposure to cadmium leads to a buildup of cadmium in the kidneys that can cause kidney disease. Cadmium has been shown to be a developmental toxicant in animals, resulting in fetal malformations and other effects, but no conclusive evidence exists in humans. An association between cadmium inhalation exposure and an increased risk of lung cancer has been reported from human studies, but these studies are inconclusive due to confounding factors. Animal studies have demonstrated an increase in lung cancer from longterm inhalation exposure to cadmium. We have classified cadmium as a Group B1, probable human carcinogen when inhaled; data are inadequate to determine whether cadmium is carcinogenic when ingested. 7. Chromium

Chromium may be emitted in two forms, trivalent chromium (chromium III) or hexavalent chromium (chromium VI). The respiratory tract is the major target organ for chromium VI toxicity, for acute (shortterm) and chronic (longterm) inhalation exposures. Shortness of breath, coughing, and wheezing have been reported from acute exposure to chromium VI, while perforations and ulcerations of the septum, bronchitis, decreased pulmonary function, pneumonia, and other respiratory effects have been noted from chronic exposure. Limited human studies suggest that chromium VI inhalation exposure may be associated with complications during pregnancy and childbirth, while animal studies have not reported reproductive effects from inhalation exposure to chromium VI. Human and animal studies have clearly established that inhaled chromium VI is a carcinogen, resulting in an increased risk of lung cancer. We have classified chromium VI as a Group A, human carcinogen by the inhalation exposure route. Oral exposure of humans to chromium VI has been reported to cause sores in the mouth, gastrointestinal effects, and elevated white blood cell counts. Animal studies of oral chromium VI exposure have reported testicular degeneration and fetal damage in mice and rats. Chromium IV is also a potent contact sensitizer, producing allergic dermatitis in previouslyexposed humans. Data are inadequate to determine if chromium VI is carcinogenic by oral exposure.

Chromium III is much less toxic than chromium VI. The respiratory tract is also the major target organ for chromium III toxicity, similar to chromium VI. Chromium III is an essential element in humans, with a daily oral intake of 50 to 200 micrograms per day ([mu]g/d) recommended for an adult. Data on adverse effects of high oral exposures of chromium III are not available for humans, but a study with mice suggests possible damage to the male reproductive tract. We have not classified chromium III for carcinogenicity.

8. Cobalt

Acute (shortterm) exposure to high levels of cobalt by inhalation in humans and animals results in respiratory effects such as a significant decrease in ventilatory function, congestion, edema, and hemorrhage of the lung. Respiratory effects are also the major effects noted from chronic (longterm) exposure to cobalt by inhalation, with respiratory irritation, wheezing, asthma, pneumonia, and fibrosis noted. Cardiac effects, congestion of the liver, kidneys, and conjunctiva, and immunological effects have also been associated with cobalt inhalation in humans. Cobalt is an essential element in humans, as a constituent of vitamin B12, but excessive oral intake has been reported to damage the heart, and to cause gastrointestinal effects and contact dermatitis. Human and animal studies are inconclusive with respect to potential carcinogenicity of cobalt. We have not classified cobalt for carcinogenicity.

9. Mercury

Mercury exists in three forms: Elemental mercury, inorganic mercury compounds (primarily mercuric chloride), and organic mercury compounds (primarily methylmercury). Each form exhibits different health effects. Brick, structural clay products, and clay ceramics manufacturing may release elemental or inorganic mercury, but not methylmercury. However, elemental and inorganic mercury are deposited on surface water, where they are converted to methylmercury, an important food contaminant.

Acute (shortterm) exposure to high levels of elemental mercury in humans results in central nervous system (CNS) effects such as tremors, mood changes, and slowed sensory and motor nerve function. High inhalation exposures can also cause kidney damage and effects on the gastrointestinal tract and respiratory system. Chronic (longterm) inhalation exposure to elemental mercury in humans also affects the CNS, with effects such as increased excitability, irritability, excessive shyness, and tremors. Data on toxic effects of oral exposure to elemental mercury are sparse. We have not classified elemental mercury for carcinogenicity.

Acute exposure to inorganic mercury by the oral route may result in effects such as nausea, vomiting, and severe abdominal pain. The major effect from chronic exposure, either oral or inhalation, to inorganic mercury is kidney damage. Reproductive and developmental animal studies have reported effects such as alterations in
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testicular tissue, increased embryo resorption rates, and abnormalities of development. Mercuric chloride (an inorganic mercury compound) exposure has been shown to result in forestomach, thyroid, and renal tumors in experimental animals. We have classified mercuric chloride as a Group C, possible human carcinogen.

Both acute and chronic oral exposure to methylmercury have been found to cause developmental damage to the central nervous system in fetuses and children, with effects including mental retardation, deafness, blindness, and cerebral palsy. Lower exposures may cause developmental delays and abnormal reflexes. The most important source of methylmercury exposure for most people is eating fish. Although fish is an important part of a balanced diet federal and state fish advisories recommend limiting intake of certain fish that contain elevated methylmercury levels.

10. Manganese

Health effects in humans have been associated with both deficiencies and excess intakes of manganese. Chronic (longterm) exposure to low levels of manganese in the diet is considered to be nutritionally essential in humans, with a recommended daily allowance of 2 to 5 milligrams per day (mg/d). Chronic inhalation exposure to high levels of manganese by inhalation in humans results primarily in CNS effects. Visual reaction time, hand steadiness, and eyehand coordination were affected in chronicallyexposed workers. Manganism, characterized by feelings of weakness and lethargy, tremors, a mask like face, and psychological disturbances, may result from chronic exposure to higher levels. Impotence and loss of libido have been noted in male workers afflicted with manganism attributed to inhalation exposures. We have classified manganese as Group D, not classifiable as to human carcinogenicity.

11. Nickel

Nickel is an essential element in some animal species, and it has been suggested it may be essential for human nutrition. Nickel dermatitis, consisting of itching of the fingers, hands, and forearms, is the most common effect in humans from chronic (longterm) skin contact with nickel. Respiratory effects have also been reported in humans from inhalation exposure to nickel. No information is available regarding the reproductive or developmental effects of nickel in humans, but animal studies have reported such effects. Human and animal studies have reported an increased risk of lung and nasal cancers from exposure to nickel refinery dusts and nickel subsulfide. Animal inhalation studies of soluble nickel compounds (i.e., nickel carbonyl) have reported lung tumors. Dermal exposure to nickel may produce contact dermatitis. Adverse effects of oral nickel exposure are not welldescribed. We have classified nickel refinery dust and nickel subsulfide as Group A, human carcinogens, and nickel carbonyl as a Group B2, probable human carcinogen, by inhalation exposure. 12. Lead

Lead is a very toxic element, causing a variety of effects at low oral or inhaled dose levels. Brain damage, kidney damage, and gastrointestinal distress may occur from acute (shortterm) exposure to high levels of lead in humans. Chronic (longterm) exposure to lead in humans results in effects on the blood, CNS, blood pressure, and kidneys. Children are particularly sensitive to the chronic effects of lead, with slowed cognitive development, reduced growth, and other effects reported. Reproductive effects, such as decreased sperm count in men and spontaneous abortions in women, have been associated with lead exposure. The developing fetus is at particular risk from maternal lead exposure, with low birth weight and slowed postnatal
neurobehavioral development noted. Human studies are inconclusive regarding lead exposure and cancer, while animal studies have reported an increase in kidney cancer from lead exposure by the oral route. We have classified lead as a Group B2, probable human carcinogen. 13. Selenium

Selenium is a naturally occurring substance that is toxic at high concentrations but is also a nutritionally essential element. Acute (shortterm) exposure to elemental selenium, hydrogen selenide, and selenium dioxide by inhalation results primarily in respiratory effects, such as irritation of the mucous membranes, pulmonary edema, severe bronchitis, and bronchial pneumonia. Studies of humans chronically (longterm) exposed to high levels of selenium in food and water have reported discoloration of the skin, pathological deformation and loss of nails, loss of hair, excessive tooth decay and discoloration, lack of mental alertness, and listlessness. The consumption of high levels of selenium by pigs, sheep, and cattle has been shown to interfere with normal fetal development and to produce birth defects. Results of human and animal studies suggest that supplementation with some forms of selenium may result in a reduced incidence of several tumor types. One selenium compound, selenium sulfide, is carcinogenic in animals exposed orally. We have classified elemental selenium as a Group D, not classifiable as to human carcinogenicity, and selenium sulfide as a Group B2, probable human carcinogen.
II. Summary of Responses to Major Comments and Changes to the Brick and Structural Clay Products Manufacturing Proposed NESHAP

In response to the public comments received on the proposed BSCP rule, we made several changes in developing today's final BSCP rule. The major comments and our responses and rule changes are summarized in the following sections. A more detailed summary can be found in the ResponsetoComments document, which is available from several sources (see SUPPLEMENTARY INFORMATION section).

A. Air Pollution Control Devices

The most significant change to the proposed BSCP rule concerns our conclusions regarding the effective application of air pollution control devices (APCD) to existing kilns. The EPA received numerous comments from industry representatives, kiln manufacturers, and air pollution control device vendors on issues related to the application and performance of APCD. The MACT floor in the proposed rule was based on the use of dry lime injection fabric filters (DIFF), dry lime scrubber/fabric filters (DLS/FF), or wet scrubbers (WS). Another technology commonly used to control emissions from brick kilns, dry limestone adsorbers (DLA), was not considered to be a MACT floor technology at the time of proposal because we had concerns with monitoring options and our data indicated that the DLA could not achieve HAP emissions reductions equivalent to the reductions achieved by DIFF, DLS/FF, or WS technologies. However, as discussed in the paragraphs below, many commenters reported disadvantages of the DIFF, DLS/FF, and WS technologies for BSCP kilns and provided information to address our concerns about DLA technology. Consequently, the final rule allows some sources to use the DLA technology.

Several commenters argued that DIFF, DLS/FF, and WS technologies are not proven or commercially available for BSCP kilns. Commenters pointed out that, with the exception of one facility, fullscale WS have never been used on
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BSCP kilns, although some shortterm pilot tests of WS have been conducted. The commenters pointed out that injection systems (such as DIFF and DLS/FF) and wet control devices need a certain airflow to operate properly, and different products may require different airflows, some of which could be outside of the range within which the APCD operates properly. In addition, commenters pointed out that during kiln slowdowns (which could be caused by a situation such as an economic slowdown), the APCD may not be able to operate at all because of reduced kiln airflow.

Several commenters expressed concerns about waste disposal. Commenters stated that DIFF and DLS/FF systems produce large amounts of solid waste that is difficult and expensive to dispose of. Commenters stated that WS would not be viable options for many BSCP plants because of wastewater treatment issues (e.g., limited or no sewer access, wastewater treatment costs). Commenters added that recycling of WS wastewater back into the brick body is not an option because of problems created by the soluble salts in the water (e.g., scumming and efflorescence) and because the volume of wastewater generated would exceed process water needs even if recycling were possible.

Commenters also raised concerns about retrofitting existing BSCP kilns with DIFF, DLS/FF, and WS technologies. Commenters pointed out that brick color, the primary factor in brick sales, is affected by kiln airflow. Thus, retrofitting with an APCD that changes the kiln airflow would change the recipes for the manufacture of brick in a tunnel kiln. Thus, years of experience in the colors produced by the unique firing characteristics of a kiln would be lost. Implications are serious if a facility cannot match its existing product line.

The commenters also charged that we did not account for other retrofitting problems associated with installing DIFF, DLS/FF, or WS on older kilns, and the costs associated with these problems. Commenters also described how attempts at retrofitting kilns with these APCD have resulted in significant amounts of kiln downtime and permanent reductions in kiln production capacities. As stated by the commenters, none of the retrofits have been entirely successful in terms of reducing emissions while not disrupting the production process, and several have had dramatic negative impacts on the production process. At one facility that retrofitted two kilns with DIFF, the capacities of the two kilns decreased from 13.5 cars per day to 12.2 cars per day because of changes in the kiln airflow that resulted from the retrofit. This resulted in a loss of revenue of about $1 million per year. Another retrofit DIFF (multistage injection system) installation at a different facility was reported to be extremely problematic, and the cost of the APCD, which was originally estimated at $1 million, is now over $2 million and the system is still not operating correctly more than 2 years later. The facility has experienced numerous problems with the basic design of the unit, including improperly designed dampers and reagent feeding systems. A facility representative stated that the problems are largely due to the fact that few systems have been developed for brick kiln operations; therefore, vendors are still learning (often on the industry's nickel) how to design these systems. In the facility's public comments, they stated that they plan to never build another hot baghouse (DIFF or DLS/FF) due to the massive operating problems associated with them. A retrofit DLS/FF system, the only one that has been attempted in the U.S. to date, also was problematic. The facility stated that they have experienced maintenance and material quality problems that have resulted in kiln downtime. The facility added that the problems stem from the fact that the system is a prototype without a substantial operational, troubleshooting and maintenance history, which has left the facility in the position of having to diagnose and solve the problems as the system operates. In addition, the company that installed this system is no longer quoting systems to the BSCP industry.

Numerous commenters recommended that EPA allow use of DLA. The commenters described the operating benefits of DLA, including ease of operation, low operating cost, little down time, and the ability to handle kiln fluctuations with changing throughputs. Most importantly, DLA do not impact kiln operation. The commenters pointed out that DLA do not require a minimum airflow like DIFF, DLS/FF, or WS technologies. One commenter pointed out that once a DLA is designed for maximum airflow, any fluctuations below this maximum only create more contact time between the kiln exhaust gases and the limestone, which would likely increase the effectiveness of the DLA and would not impact the operation of the kiln. The commenters pointed out that DLA have been used extensively in Europe for many years and also are the most prevalent APCD used in the BSCP industry in the United States. Many commenters stated that DLA should be allowed if they can meet the BSCP standards. The commenters indicated that plants should not have to request sitespecific monitoring parameters for DLA because they are the most prevalent technology. In addition, some commenters discussed the high costs and limited additional HAP reduction associated with replacing existing DLA with a DIFF system.

Several commenters felt that EPA disregarded or ``bashed'' DLA and disagreed with EPA's conclusions regarding DLA in the preamble to the proposed rule. Specifically, the commenters disagreed that: DLA generate particulate matter (PM) emissions; longterm test data that demonstrate DLA performance over the life of the sorbent are not available; DLA limestone is not continuously replaced; and the performance of DLA decreases as the sorbent is reused because the ability of the sorbent to adsorb HF and HCl decreases.

We disagree with commenters that the use of DIFF has not been proven in the brick industry. The DIFF and DLS/FF systems are a proven control technology for kilns with a given minimum airflow rate. We do, however, believe that retrofitting existing kilns with DIFF or DLS/FF systems is not feasible in many cases. We recognize that WS may not be practical or lowcost for most facilities, but believe they could be a legitimate option for some facilities (e.g., facilities with sewer access). We acknowledge that retrofitting existing BSCP kilns with certain APCD (particularly those that affect kiln airflow) can alter timehonored recipes for brick color, thereby changing the product. We acknowledge that DLA are used extensively around the world to control emissions from brick kilns. In developing the description of DLA technology for the preamble to the proposed rule, we used the technical data available to us at the time. We had no intention of ``bashing'' DLA but simply reported the data at hand.

After consideration of the comments received regarding DIFF, DLS/ FF, WS, and DLA technologies, we have come to new conclusions regarding the effective application of these devices. We now believe that DLA are the only currently available technology that can be used to retrofit existing kilns without potentially significant impacts on the production process, and we have revised today's final rule accordingly. In addition, we believe that, because of the retrofit concerns that we have identified, it is not technologically and economically feasible for an existing
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small tunnel kiln that would otherwise meet the criteria for reconstruction in 40 CFR 63.2 and whose design capacity is increased such that it is equal to or greater than 9.07 Mg/hr (10 tph) of fired product (for the remainder of this preamble, these sources will be referred to as ``existing small kilns that are rebuilt such that they become large kilns'') to meet the relevant standards (i.e., new source MACT) by retrofitting with a DIFF, DLS/FF, or WS. In addition, we believe that it is not technologically and economically feasible for an existing large DLAcontrolled kiln that would otherwise meet the criteria for reconstruction in 40 CFR 63.2 (for the remainder of this preamble, these sources will be referred to as ``existing large DLA controlled kilns that are rebuilt'') to meet the relevant (i.e., new source MACT) standards by retrofitting with a DIFF, DLS/FF, or WS. Accordingly, we have added regulatory language in 40 CFR 63.8390(i) to provide that an existing small kiln that is rebuilt such that it becomes a large kiln and an existing large DLAcontrolled tunnel kiln that is rebuilt do not meet the definition of reconstruction in 40 CFR 63.2 and are not subject to the same requirements as new and reconstructed large tunnel kilns. However, it is technologically and economically feasible for both types of kilns described in 40 CFR 63.8390(i) to retrofit with a DLA (or to continue operating an existing DLA) and we have revised today's final rule to require that such kilns meet emission limits that correspond to the level of control provided by a DLA. We continue to believe that DIFF, DLS/FF, and WS are appropriate technologies for new large tunnel kilns and for reconstructed large tunnel kilns that were equipped with DIFF, DLS/FF, or WS prior to reconstruction. However, DLA are the only APCD that have been demonstrated on small tunnel kilns (which have smaller airflows than large tunnel kilns), and, therefore, the requirements for new and reconstructed small tunnel kilns are based on the level of control that can be achieved by a DLA. We note that facilities have the flexibility to select any control device or technique that ensures that emissions from their brick kilns are in compliance with the emission limits set forth in the final rule. Each of the APCD described above have advantages and disadvantages to their use, and the selection of the APCD to meet the requirements of the final rule will be dependent on sitespecific parameters.
B. Affected Source

1. ProductionRate Limit

The proposed rule subcategorized tunnel kilns based on a 9.07 Mg/hr (10 tph) design capacity. We requested comment on the appropriate design capacitybased subcategorization level in the preamble to the proposed rule. We received numerous comments regarding
subcategorization of tunnel kilns. While some commenters agreed with the 9.07 Mg/hr (10 tph) distinction among tunnel kiln subcategories, several commenters thought that the 9.07 Mg/hr (10 tph) limit was arbitrarily assigned. The commenters charged that EPA did not use all available data in determining the appropriate size cutoff. Many commenters argued that the design capacity limit should be higher based on available data (i.e., 10.1 Mg/hr (11.1 tph) or 12.1 Mg/hr (13.3 tph)). The commenters disagreed that the cutoff should be rounded down from 10.1 Mg/hr (11.1 tph) to 9.07 Mg/hr (10 tph).

Some commenters noted that a design capacity distinction gives a competitive advantage to facilities operating smaller kilns. One commenter disagreed that there was a technological basis for differentiating among tunnel kilns producing above or below 9.07 Mg/hr (10 tph). The commenter stated that EPA may not subcategorize tunnel kilns to reduce costs.

Through subcategorization, we are able to define subsets of similar emission sources within a source category if differences in emissions characteristics, processes, APCD viability, or opportunities for pollution prevention exist within the source category. Section 112(d)(1) of the CAA states ``the Administrator may distinguish among classes, types, and sizes of sources within a category or subcategory'' in establishing emission standards. Thus, we have discretion in determining appropriate subcategories based on classes, types, and sizes of sources. We used this discretion in developing subcategories for the BSCP source category. We first subcategorized kilns based on type (i.e., periodic kilns versus tunnel kilns). We then further subcategorized tunnel kilns based on kiln size. Our distinctions are based on technological differences in the equipment. For example, periodic kilns are smaller than tunnel kilns and operate in batch cycles, whereas tunnel kilns operate continuously. There are also differences in the effective application of air pollution controls. To our knowledge, HAP emissions from periodic kilns have not successfully been controlled. Similarly, we distinguished between tunnel kilns with design capacities above and below 9.07 Mg/hr (10 tph) at proposal in part because the APCD we believed to be the best performers (DIFF, DLS/ FF, and WS) were not demonstrated on existing tunnel kilns with design capacities below roughly 9.07 Mg/hr (10 tph). For the reasons discussed below, we revisited the appropriate subcategorization level in response to comments on the proposal when developing today's final rule. While we continue to believe that 9.07 Mg/hr (10 tph) is the appropriate subcategorization level, our reasons for choosing that level have changed since proposal in light of new information that we received during the public comment period about DLA controls and the three proposed MACT controls (DIFF, DLS/FF, and WS).

As discussed earlier, numerous commenters pointed out serious concerns regarding retrofitting existing kilns with APCD such as DIFF, DLS/FF, and WS. Therefore, we now consider DLA to be the only currently available technology that can be used to retrofit existing kilns, including existing small kilns that are rebuilt such that they become large kilns and existing large DLAcontrolled kilns that are rebuilt, without potentially significant impacts on the production process.

In response to comments suggesting that we include new data in our analyses, we updated our data base with information on new kilns, new APCD (except those controls that we consider to achieve the lowest achievable emission rate (LAER) as specified in section 112(d)(3)(A) of the CAA), changes in kiln capacities, and changes in facility ownership. We used the information submitted by commenters and made followup calls to States and individual facilities for additional clarification as necessary to update our data base.

We used our updated data base in reevaluating all aspects of the proposed standards. The smallest tunnel kiln with MACT floor controls (i.e., with DLA controls reflecting the existing source MACT floor under today's final rule) in our updated database has a capacity of 8.3 Mg/hr (9.1 tph). Rounding up to the nearest integer, based on current application of APCD to BSCP tunnel kilns, we believe that 9.07 Mg/hr (10 tph) continues to be an appropriate subcategorization level. Commenters have stated that a smaller tunnel kiln (e.g., 4.5 Mg/hr (5 tph) capacity) is dissimilar from a larger tunnel kiln (e.g., 13.6 Mg/ hr (15 tph) capacity), especially with regard to the airflow, which is a key operating parameter for APCD. Airflow is particularly important for
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lime injectiontype systems (DIFF and DLS/FF), because the injected lime is carried through the reaction chamber (or duct) by the kiln exhaust gas. For a given lime injection rate, if a minimum exhaust flow is not maintained, the sorbent can settle in the duct work and cause APCD malfunction. Furthermore, APCD malfunctions can affect the airflow within the kiln, and can destroy product that is in the kiln. We believe that DIFF and DLS/FF systems, if attempted on smaller kilns, would experience more difficulties with respect to airflow than systems on larger kilns because as the design airflow decreases, the acceptable operating range also would be expected to decrease. Any fluctuation in airflow would be expected to have a greater impact on APCD operation as the size of the system decreases. Given the technological concerns and the capacities of currentlycontrolled tunnel kilns, we maintain that a design capacitybased subcategorization level of 9.07 Mg/hr (10 tph) is appropriate for existing tunnel kilns.

We acknowledge the comments suggesting that 10.1 Mg/hr (11.1 tph) should be the size cutoff based on the smallest DIFFcontrolled tunnel kiln. However, because we now consider that the performance of a DLA represents the MACT floor for existing sources (and DIFF, DLS/FF, and WS also can meet the emission limits), we considered the smallest non LAER DLAcontrolled kiln in setting the subcategorization level. We disagree that 12.1 Mg/hr (13.3 tph) would have been the proper level for proposal or for the final rule. We believe that consideration of technological differences and the effective application of APCD to kilns of different sizes is the appropriate method of selecting a subcategorization level. We maintain that 9.07 Mg/hr (10 tph) is appropriate.

We understand that, regardless of the particular subcategorization level selected, there will be facilities that operate kilns with throughputs slightly above the level and some that operate kilns at slightly below the level. Facilities operating kilns slightly above the subcategorization level have the option of accepting a federally enforceable permit limit to limit their throughput to below the level. Facilities operating just below the level must make careful decisions regarding expansion of their kilns. We acknowledge that facilities operating near the subcategorization level must make decisions regarding permit limits and expansions based on facilityspecific considerations (e.g., control costs, impact on revenue). However, as some commenters have pointed out, cost is not an appropriate criteria for us to use in establishing subcategories, because our discretion for establishing subcategories is limited, under the CAA, to distinguishing among classes, types, and sizes of sources.

2. R&D Kiln Definition

One commenter requested that we change the definition of research and development (R&D) kiln so that it is consistent with the definition of R&D in section 112(c)(7) of the CAA and most other NESHAP. Therefore, today's final rule includes a revised definition of research and development kiln that is consistent with section 112(c)(7) of the CAA and other NESHAP.
C. Existing Source MACT
1. Consideration of Synthetic Area Sources in the MACT Floor Determinations for Existing Sources

In the preamble to the proposed BSCP rule, we requested comment on inclusion of synthetic area sources (also called synthetic minor sources) in the MACT floor determinations for existing tunnel kilns. For the remainder of this preamble, we will refer to these sources as synthetic minor sources. Synthetic minor sources are those facilities that emit fewer than 10 tons per year of any HAP and fewer than 25 tons per year of any combination of HAP because they use some emission control device (or devices), the operation of which is required by a Federally Enforceable State Operating Permit (FESOP). In the absence of such controls, these sources would be major.

Inclusion of synthetic minor sources in the MACT floor determination was an issue prior to proposal because whether or not synthetic minor sources were included would affect the level of control represented by the floor determinations for existing large tunnel kilns (i.e., tunnel kilns with design capacities equal to or greater than 9.07 Mg/hr (10 tph)). Had synthetic minor sources been excluded, the MACT floor for existing tunnel kilns would have been ``no emissions reductions.'' With synthetic minor sources included (as we proposed), the MACT floor for existing tunnel kilns was based on a DIFF, DLS/FF or WS.

Industry representatives asserted, prior to proposal, that the BSCP MACT floor determination should not include synthetic minor sources. We rejected the idea of excluding synthetic minor sources from the MACT floor determination for several reasons discussed in the preamble to the proposed rule. (See 67 FR 47894, 4791147912, July 22, 2002.) Nevertheless, because of the industry representatives' arguments, we requested comment from all interested parties on inclusion of synthetic minor sources in MACT floor determinations.

Following proposal, numerous industry representatives commented on the issue of whether to include synthetic minor sources in MACT floor determinations. The industry representatives commented that only major sources are included in the listed BSCP source category, and therefore, only major sources are to be used in the MACT floor determination. The commenters referenced section 112(a)(1) of the CAA, which defines major source as a source that ``emits or has the potential to emit considering controls 10 tons per year * * *.'' (emphasis added), and stated that by definition, synthetic minor sources are not major sources. The commenters noted that EPA did not include true area sources (or minor sources) in the MACT floor determination and stated that synthetic minor sources should be treated similarly for purposes of establishing MACT floors.

An environmental group also commented on the issue of including synthetic minor sources in MACT floor determinations. The commenter supported EPA's decision to include synthetic minor sources in the MACT floor for BSCP. The commenter stated that the CAA requires EPA to include synthetic minor sources in MACT floor determinations. The commenter stated that excluding consideration of the bestcontrolled sources (which became synthetic minor sources as a result of effective controls) would contradict the CAA section 112(d) MACT floor methodology established by Congress. The commenter argued that such exclusion would weaken emission standards required for existing sources, and increase the levels of air toxics released into the environment.

Section 112(d) of the CAA directs us to establish emission standards for each category or subcategory of major sources and minor sources of HAP listed for regulation pursuant to section 112(c) of the CAA. Each such standard must reflect a minimum level of control known as the MACT floor. (See CAA section 112(d).) However, section 112 of the CAA does not specifically address synthetic minor or synthetic area sources, which include those sources that emit fewer than 10 tons per year of any HAP or fewer than 25 tons per year of any combination of HAP because they use some emission control device(s), pollution prevention techniques or other measures (collectively referred to as controls in this preamble) adopted
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under Federal or State regulations. If not for the enforceable controls they have implemented, synthetic minor sources would be major sources under section 112 of the CAA.

We believe that the better interpretation of the CAA's plain language and legislative history requires that synthetic minor sources be included in MACT floor determinations. First, the plain language of the statute makes clear that our MACT floor determinations are to reflect the best sources in a category. For new sources in a category or subcategory, the MACT floor shall not be less stringent than the emission control that is achieved in practice by the bestcontrolled similar source, as determined by EPA. (See CAA section 112(d)(3), emphasis added.) For existing sources in a category or subcategory with 30 or more sources, the MACT floor may be less stringent than the floor for new sources in the same category or subcategory but shall not be less stringent than the average emission limitation achieved by the best performing 12 percent of the existing sources (for which the Administrator has emissions information). (See CAA section 112(d)(3)(A), emphasis added.\1\) Thus, section 112(d)(3) of the CAA requires that MACT floors reflect what the bestcontrolled new sources and the bestperforming existing sources achieve in practice. These phrases contain no exemptions and are not limited by references to sources with or without controls. Therefore, they suggest that all of the bestcontrolled or bestperforming sources should be considered in MACT floor determinations, regardless of whether or not such sources rely upon controls.
\1\ If a category or subcategory has fewer than 30 sources, the floor shall be ``the average emission limitation achieved by the best performing 5 sources (for which the Administrator has or could reasonably obtain emissions information) in the category or subcategory.'' (See CAA section 112(d)(3)(B), emphasis added.)

Furthermore, section 112(d)(3) of the CAA expressly excludes certain sources that meet LAER requirements from MACT floor determinations for existing sources. (See CAA section 112(d)(3)(A).) The fact that Congress expressly excluded such LAER sources but did not also exclude synthetic minor sources suggests that no exclusion was intended for synthetic minor sources. Indeed, nothing in the statute suggests that EPA should exclude a control technology from its consideration of the MACT floor because the technology is so effective that it reduces source emissions such that the source is no longer a major source of HAP. (See 67 FR 36,460 and 36,464, May 23, 2002, stating this rationale for including synthetic minor sources in the floor determination for the proposed NESHAP for municipal solid waste landfills.)

Some commenters argue that because the BSCP source category only includes major sources and synthetic minor sources are nonmajor by definition, synthetic minor sources (like true area sources) fall outside the regulated source category and should not be considered in MACT floor determinations. EPA agrees that the BSCP source category includes only major sources. (See 67 FR 47,894 and 47,898, July 22, 2002.) However, EPA disagrees that the CAA contemplates that synthetic minor sources must be treated like true area sources and excluded from MACT floor determinations. Section 112(a) of the CAA defines a major source as:

any stationary source or group of stationary sources located within a contiguous area and under common control that emits or has the potential to emit considering controls, in the aggregate, 10 tons per year or more of any hazardous air pollutant or 25 tons per year or more of any combination of hazardous air pollutants * * *. (See CAA section 112(a)(1).) An area source is defined as any stationary source of hazardous air pollutants that is not a major source. (See CAA section 112(a)(1).) In the major source definition, the reference to a source's potential to emit considering controls allows the interpretation that a source's potential to emit before and after controls is relevant, such that synthetic minor sources may be considered within the meaning of this definition and included in MACT floor determinations for categories of major sources.\2\ Some commenters appear to suggest that the reference to a source's potential to emit considering controls can only mean a source's potential to emit after controls have been implemented. While it is possible to read the phrase in this manner in isolation, this interpretation would have the effect of excluding the bestperforming sources in a category from MACT floor determinations and therefore would be contrary to the statutory mandate that EPA set MACT floors based on the levels the best controlled new sources and the bestperforming existing sources achieve in practice. We believe the statutory reference to potential to emit considering controls should be read in a manner consistent with the other requirements of section 112(d) of the CAA to allow for the consideration of synthetic minor sources in MACT floor determinations for categories of major sources.
\2\ We believe this approach is not inconsistent with our policy that existing sources that limit their potential to emit to below the major source threshold prior to the first compliance deadline under a MACT standard will not be subject to the standard, as one commenter suggests. (See Memorandum from John S. Seitz, Director, Office of Air Quality Planning and Standards, EPA, to EPA Regions, ``Potential to Emit for MACT StandardsGuidance on Timing Issues,'' May 16, 1995.) Including synthetic minor sources in MACT floor determinations ensures that MACT floors reflect the bestperforming sources, as the CAA requires. At the same time, our policy recognizes that sources that already achieve or perform better than the MACT floors need not be subject to the MACT standards.

In addition, the legislative history suggests that synthetic minor sources should be included in MACT floor determinations. In a floor statement, Senator Durenberger stated that in implementing section 112(d)(3) of the CAA, ``the [Senate] managers intend the Administrator to take whatever steps are necessary to assure that [the Administrator] has collected data on all of the betterperforming sources within each category. [The Administrator] must have a datagathering program sufficient to assure that [EPA] does not miss any sources that have superior levels of emission control.'' (See Environment and Natural Resources Policy Division, Congressional Research Service, 103d Cong., S.Prt. 10338 (prepared for the U.S. Senate Committee on Environment and Public Works), A Legislative History of the Clean Air Act Amendments of 1990 at 870, Nov. 1993, emphasis added.) This statement underscores that Congress intended for MACT floor determinations to reflect consideration of all of the sources in each category with the best emission controls. We believe it would be inconsistent with Congress's intent and the plain language of the CAA to exclude synthetic minor sourcesthose sources with superior controls which became synthetic minor sources by implementing such controlsfrom MACT floor determinations.

We believe that the inclusion of synthetic minor sources in MACT floor determinations is justified because of the reasons explained above. Even if the MACT floor determination had been ``no emissions reductions'' we believe that a departure from the MACT floor to a beyondthefloor standard, based on DLA technology, is viable because the benefits associated with the emissions reductions will exceed the cost of installing and operating the technology.

2. MACT Floors for Existing Sources

Some commenters questioned how the MACT floor for existing sources was
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set. Some commenters thought that control devices installed for sulfur oxides (SOx) control (rather than for HAP control) should not be considered in the MACT floor. Other commenters felt that costs should be a consideration.

One commenter charged that EPA has simply set MACT floors based on control technology type and that EPA did not identify the relevant best performers and set floors reflecting their average emission level. The commenter noted that factors other than control device type affect emissions and that EPA must consider all nonnegligible factors in setting MACT floors and considering beyondthefloor measures. The commenter stated that if EPA believes it is unworkable to consider all factors, then perhaps EPA should base standards on actual emissions data which reflects all the factors influencing a source's performance. The commenter also noted that EPA picked the worst performance of any source that used the chosen technology to set the floor for PM.

A detailed discussion of how we determined the MACT floor for existing large tunnel kilns (i.e., tunnel kilns with design capacities equal to or greater than 9.07 Mg/hr (10 tph)) is provided below. Although the discussion in the example below focuses on existing large tunnel kilns that exhaust directly to the atmosphere or to an APCD, the same MACT floor methodology was used for existing large tunnel kilns that exhaust to sawdust dryers prior to exhausting to the atmosphere, existing small tunnel kilns that exhaust directly to the atmosphere or to an APCD, exis

FOR FURTHER INFORMATION CONTACT For further information concerning applicability and rule determinations, contact the appropriate State or local agency representative. If no State or local representative is available, contact the EPA Regional Office staff listed in 40 CFR 63.13. For information concerning the analyses performed in developing the final rules, contact Ms. Mary Johnson, Combustion Group, Emission Standards Division (MCC43901), U.S. EPA, Research Triangle Park, North Carolina 27711, telephone number (919) 5415025, email address:
johnson.mary@epa.gov.