National Emissions Standards for Hazardous Air Pollutants: Secondary Aluminum Production

Federal RegisterFeb 14, 2012

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2010-0544; FRL-9628-8]

RIN 2060-AQ40

National Emissions Standards for Hazardous Air Pollutants: Secondary Aluminum Production

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

The EPA is proposing amendments to the national emissions standards for hazardous air pollutants for Secondary Aluminum Production to address the results of the residual risk and technology review that the EPA is required to conduct by the Clean Air Act. In addition, the EPA is proposing amendments to correct and clarify rule requirements and provisions. These proposed amendments would require emission sources to comply with the emission limits at all times including periods of startup and shutdown; add a definition of affirmative defense; add a requirement to report performance testing through the Electronic Reporting Tool (ERT); add rule provisions allowing owners and operators to change furnace classifications; add rule requirements regarding testing of uncontrolled furnaces; add compliance provisions for hydrogen fluoride (HF) for uncontrolled group 1 furnaces; add operating requirements such as monitoring of lime injection rates; and make technical corrections and clarifications to the applicability, definitions, operating, monitoring, and performance testing requirements.

DATES:

Comments must be received on or before March 30, 2012. Under the Paperwork Reduction Act, comments on the information collection provisions are best assured of having full effect if the Office of Management and Budget (OMB) receives a copy of your comments on or before March 15, 2012.

Public Hearing.

If anyone contacts the EPA requesting to speak at a public hearing by February 24, 2012, a public hearing will be held on February 29, 2012.

ADDRESSES:

Submit your comments, identified by Docket ID Number EPA-HQ-OAR-2010-0544, by one of the following methods:

•

http://www.regulations.gov:

Follow the on-line instructions for submitting comments.

•

Email: a-and-r-docket@epa.gov,

Attention Docket ID Number EPA-HQ-OAR-2010-0544.

•

Fax:

(202) 566-9744, Attention Docket ID Number EPA-HQ-OAR-2010-0544.

•

Mail:

U.S. Postal Service, send comments to: EPA Docket Center, EPA West (Air Docket), Attention Docket ID Number EPA-HQ-OAR-2010-0544, U.S. Environmental Protection Agency, Mailcode: 2822T, 1200 Pennsylvania Ave. NW., Washington, DC 20460. 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 Street NW., Washington, DC 20503.

•

Hand Delivery:

U.S. Environmental Protection Agency, EPA West (Air Docket), Room 3334, 1301 Constitution Ave. NW., Washington, DC 20004, Attention Docket ID Number EPA-HQ-OAR-2010-0544. Such deliveries are only accepted during the Docket's normal hours of operation, and special arrangements should be made for deliveries of boxed information.

Instructions.

Direct your comments to Docket ID Number EPA-HQ-OAR-2010-0544. The EPA's policy is that all comments received will be included in the public docket without change and may be made available on-line at

http://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

http://www.regulations.gov

or email. The

http://www.regulations.gov

Web site is an “anonymous access” system, which means the EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an email comment directly to the EPA without going through

http://www.regulations.gov,

your email address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the Internet. If you submit an electronic comment, the 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 the EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, the EPA may not be able to consider your comment. Electronic files should avoid the use of special characters, any form of encryption, and be free of any defects or viruses. For additional information about the EPA's public docket, visit the EPA Docket Center homepage at

http://www.epa.gov/epahome/dockets.htm.

Docket.

The EPA has established a docket for this rulemaking under Docket ID Number EPA-HQ-OAR-2010-0544. The proposed rulemaking also used material from Docket ID Number EPA-HQ-OAR-2010-0469 in the development of this rule. All documents in the docket are listed in the

http://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, is not placed on the Internet and will be publicly available only in hard copy. Publicly available docket materials are available either electronically in

http://www.regulations.gov

or in hard copy at the EPA Docket Center, 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 EPA Docket Center is (202) 566-1742.

Public Hearing.

If a public hearing is held, it will begin at 10 a.m. on February 29, 2012 and will be held at the EPA's campus in Research Triangle Park, North Carolina, or at an alternate facility nearby. Persons interested in presenting oral testimony or inquiring as to whether a public hearing is to be held should contact Ms. Virginia Hunt, Office of Air Quality Planning and Standards, Sector Policies and Programs Division, (D243-02), U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711; telephone number: (919) 541-0832.

FOR FURTHER INFORMATION CONTACT:

For questions about this proposed action, contact Ms. Rochelle Boyd, Sector Policies and Programs Division (D243-02), Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, telephone (919) 541-1390; fax number: (919) 541-3207; and email address:

boyd.rochelle@epa.gov.

For specific information regarding the risk modeling methodology, contact Dr. Michael Stewart, Office of Air Quality Planning and Standards, Health and Environmental Impacts Division, Air Toxics Assessment Group (C504-06), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711;

telephone number: (919) 541-7524; fax number: (919) 541-0840; and email address:

stewart.michael@epa.gov.

For information about the applicability of the national emission standards for hazardous air pollutants (NESHAP) to a particular entity, contact the appropriate person listed in Table 1 of this preamble.

Table 1—List of EPA Contacts for the NESHAP Addressed in This Proposed Action

NESHAP for:

OECA Contact

OAQPS Contact

Secondary Aluminum Production

Scott Throwe, (202) 564-7013

throwe.scott@epa.gov

Rochelle Boyd, (919) 541-1390,

boyd.rochelle@epa.gov

EPA Office of Enforcement and Compliance Assurance.

EPA Office of Air Quality Planning and Standards.

SUPPLEMENTARY INFORMATION:

Preamble Acronyms and Abbreviations

Several acronyms and terms used to describe industrial processes, data inventories, and risk modeling are included in this preamble. While this may not be an exhaustive list, for ease of reading of this preamble and for reference purposes, the following terms and acronyms are defined here:

ACGIH American Conference of Government Industrial Hygienists

ADAF age-dependent adjustment factors

AEGL acute exposure guideline levels

AERMOD air dispersion model used by the HEM-3 model

APCD air pollution control devices

AMOS ample margin of safety

ANPRM advance notice of proposed rulemaking

ATSDR Agency for Toxic Substances and Disease Registry

BACT best available control technology

CAA Clean Air Act

CBI confidential business information

CFR Code of Federal Regulations

D/F dioxins and furans

EJ environmental justice

EPA Environmental Protection Agency

ERPG Emergency Response Planning Guidelines

ERT Electronic Reporting Tool

HAP hazardous air pollutants

HCl hydrogen chloride

HEM-3 Human Exposure Model, Version 3

HF hydrogen fluoride

HHRAP human health risk assessment protocols

HI hazard index

HQ hazard quotient

ICR information collection request

IRIS Integrated Risk Information System

km kilometer

LAER lowest achievable emissions rate

lb/yr pounds per year

MACT maximum achievable control technology

MACT Code code within the NEI used to identify processes included in a source category

MDL method detection level

mg/acm milligrams per actual cubic meter

mg/dscm milligrams per dry standard cubic meter

mg/m

milligrams per cubic meter

MIR maximum individual risk

MRL minimum risk level

NAC/AEGL Committee National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances

NAICS North American Industry Classification System

NAS National Academy of Sciences

NATA National Air Toxics Assessment

NEI National Emissions Inventory

NESHAP National Emissions Standards for Hazardous Air Pollutants

NOAEL no observed adverse effects level

NRC National Research Council

NTTAA National Technology Transfer and Advancement Act

O&M operation and maintenance

OAQPS Office of Air Quality Planning and Standards

OECA Office of Enforcement and Compliance Assurance

OHEA Office of Health and Environmental Assessment

OMB Office of Management and Budget

PB-HAP hazardous air pollutants known to be persistent and bio-accumulative in the environment

PM particulate matter

ppmv parts per million by volume

RACT reasonably available control technology

RBLC RACT/BACT/LAER Clearinghouse

REL reference exposure level

RFA Regulatory Flexibility Act

RfC reference concentration

RfD reference dose

RIA regulatory impact analysis

RTR residual risk and technology review

SAB Science Advisory Board

SBA Small Business Administration

SCC source classification codes

SF3 2000 Census of Population and Housing Summary

SIP state implementation plan

SOP standard operating procedures

SSM startup, shutdown, and malfunction

TEF toxic equivalency factors

TEQ toxic equivalency quotient

THC total hydrocarbons

TOSHI target organ-specific hazard index

tpy tons per year

TRIM Total Risk Integrated Modeling System

TTN Technology Transfer Network

UBC used beverage containers

UF uncertainty factor

μg/m

microgram per cubic meter

UMRA Unfunded Mandates Reform Act

UPL upper predictive limit

URE unit risk estimate

VOC volatile organic compounds

VOHAP volatile organic hazardous air pollutants

WHO World Health Organization

WWW worldwide web

Organization of this Document.

The information in this preamble is organized as follows:

I. General Information

A. What is the statutory authority for this action?

B. Does this action apply to me?

C. Where can I get a copy of this document and other related information?

D. What should I consider as I prepare my comments for the EPA?

II. Background

A. What is this source category and how did the MACT standard regulate its HAP emissions?

B. What data collection activities were conducted to support this action?

III. Analyses Performed

A. How did we estimate risks posed by the source category?

B. How did we consider the risk results in making decisions for this proposal?

C. How did we perform the technology review?

D. What other issues are we addressing in this proposal?

IV. Analytical Results and Proposed Decisions

A. What are the results of the risk assessments?

B. What are our proposed decisions regarding risk acceptability and ample margin of safety?

C. What are the results and proposed decisions based on our technology review?

D. What other actions are we proposing?

E. Compliance dates

V. Summary of Cost, Environmental, and Economic Impacts

A. What are the affected sources?

B. What are the air quality impacts?

C. What are the cost impacts?

D. What are the economic impacts?

E. What are the benefits?

VI. Request for Comments

VII. Submitting Data Corrections

VIII. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory 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 Risks and Safety Risks

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

I. National Technology Transfer and Advancement Act

J. Executive Order 12898: Federal Actions To Address Environmental Justice in Minority Populations and Low-Income Populations

I. General Information

A. What is the statutory authority for this action?

Section 112 of the CAA establishes a two-stage regulatory process to address emissions of hazardous air pollutants (HAP) from stationary sources. In the first stage, after the EPA has identified categories of sources emitting one or more of the HAP listed in section 112(b) of the CAA, section 112(d) of the CAA calls for us to promulgate national emission standards for hazardous air pollutants (NESHAP) for those sources. “Major sources” are those that emit or have the potential to emit (PTE) 10 tons per year (tpy) or more of a single HAP or 25 tpy or more of any combination of HAP. For major sources, these technology-based standards must reflect the maximum degree of emission reductions of HAP achievable (after considering cost, energy requirements and non-air quality health and environmental impacts) and are commonly referred to as maximum achievable control technology (MACT) standards.

MACT standards must require the maximum degree of emissions reduction achievable through the application of measures, processes, methods, systems or techniques including, but not limited to, measures which (1) reduce the volume of or eliminate emissions of pollutants through process changes, substitution of materials or other modifications, (2) enclose systems or processes to eliminate emissions, (3) capture or treat pollutants when released from a process, stack, storage or fugitive emissions point, (4) are design, equipment, work practice or operational standards (including requirements for operator training or certification) or (5) are a combination of the above. CAA section 112(d)(2)(A)-(E). The MACT standard may take the form of a design, equipment, work practice or operational standard where the EPA first determines that either (1) a pollutant cannot be emitted through a conveyance designed and constructed to emit or capture the pollutant or that any requirement for, or use of, such a conveyance would be inconsistent with law, or (2) the application of measurement methodology to a particular class of sources is not practicable due to technological and economic limitations. CAA sections 112(h)(1)-(2).

The MACT “floor” is the minimum control level allowed for MACT standards promulgated under CAA section 112(d)(3) and may not be based on cost considerations. For new sources, the MACT floor cannot be less stringent than the emission control that is achieved in practice by the best-controlled similar source. The MACT floors for existing sources can be less stringent than floors for new sources, but they cannot be less stringent than the average emission limitation achieved by the best-performing 12 percent of existing sources in the category or subcategory (or the best-performing five sources for categories or subcategories with fewer than 30 sources). In developing MACT standards, we must also consider control options that are more stringent than the floor. We may establish standards more stringent than the floor based on consideration of the cost of achieving the emissions reductions and any non-air quality health and environmental impacts and energy requirements.

Under CAA section 112(d)(6), the EPA is then required to review these technology-based standards and to revise them “as necessary (taking into account developments in practices, processes, and control technologies)” no less frequently than every 8 years. In conducting this review, the EPA is not obliged to completely recalculate the prior MACT determination.

NRDC

EPA,

529 F.3d 1077, 1084 (DC Cir. 2008).

The second stage in standard-setting focuses on reducing any remaining “residual” risk according to CAA section 112(f). This provision requires, first, that the EPA prepare a

Report to Congress

discussing (among other things) methods of calculating risk posed (or potentially posed) by sources after implementation of the MACT standards, the public health significance of those risks, and the EPA's recommendations as to legislation regarding such remaining risk. The EPA prepared and submitted this report (

Residual Risk Report to Congress,

EPA-453/R-99-001) in March 1999. Congress did not act in response to the report, thereby triggering the EPA's obligation under CAA section 112(f)(2) to analyze and address residual risk.

CAA section 112(f)(2) requires us to determine, for source categories subject to certain MACT standards, whether the emissions standards provide an ample margin of safety to protect public health. If the MACT standards for HAP “classified as a known, probable, or possible human carcinogen do not reduce lifetime excess cancer risks to the individual most exposed to emissions from a source in the category or subcategory to less than one in one million,” the EPA must promulgate residual risk standards for the source category (or subcategory), as necessary, to provide an ample margin of safety to protect public health. In doing so, the EPA may adopt standards equal to existing MACT standards if the EPA determines that the existing standards are sufficiently protective.

NRDC

EPA,

529 F.3d 1077, 1083 (DC Cir. 2008). (“If EPA determines that the existing technology-based standards provide an ‘ample margin of safety,' then the agency is free to readopt those standards during the residual risk rulemaking.”) The EPA must also adopt more stringent standards, if necessary, to prevent an adverse environmental effect

but must consider cost, energy, safety and other relevant factors in doing so.

“Adverse environmental effect” is defined in CAA section 112(a)(7) as any significant and widespread adverse effect, which may be reasonably anticipated to wildlife, aquatic life or natural resources, including adverse impacts on populations of endangered or threatened species or significant degradation of environmental qualities over broad areas.

Section 112(f)(2) of the CAA expressly preserves our use of a two-step process for developing standards to address any residual risk and our interpretation of “ample margin of safety” developed in the

National Emission Standards for Hazardous Air Pollutants: Benzene Emissions From Maleic Anhydride Plants, Ethylbenzene/Styrene Plants, Benzene Storage Vessels, Benzene Equipment Leaks, and Coke By-Product Recovery Plants (Benzene NESHAP)

(54 FR 38044, September 14, 1989). The first step in this process is the determination of acceptable risk. The second step provides for an ample margin of safety to protect public health, which is the level at which the standards are set (unless a more stringent standard is necessary to prevent, taking into consideration costs, energy, safety, and other relevant factors, an adverse environmental effect).

The terms “individual most exposed,” “acceptable level,” and “ample margin of safety” are not specifically defined in the CAA. However, CAA section 112(f)(2)(B) preserves the EPA's interpretation set out in the Benzene NESHAP, and the United States Court of Appeals for the District of Columbia

Circuit in

NRDC

EPA

concluded that the EPA's interpretation of subsection 112(f)(2) is a reasonable one. See

NRDC

EPA,

529 F.3d 1077 1083 (DC Cir. 2008) (“[S]ubsection 112(f)(2)(B) expressly incorporates the EPA's interpretation of the Clean Air Act from the Benzene standard, complete with a citation to the

Federal Register

”); see also

A Legislative History of the Clean Air Act Amendments of 1990,

volume 1, p. 877 (Senate debate on Conference Report). We notified Congress in the

Residual Risk Report to Congress

that we intended to use the Benzene NESHAP approach in making CAA section 112(f) residual risk determinations (EPA-453/R-99-001, p. ES-11).

In the Benzene NESHAP, 54 FR at 38044-38045, we stated as an overall objective:

In protecting public health with an ample margin of safety under section 112, EPA strives to provide maximum feasible protection against risks to health from hazardous air pollutants by (1) protecting the greatest number of persons possible to an individual lifetime risk level no higher than approximately 1 in 1 million; and (2) limiting to no higher than approximately 1 in 10 thousand [i.e., 100 in 1 million] the estimated risk that a person living near a plant would have if he or she were exposed to the maximum pollutant concentrations for 70 years.

The agency stated that “[t]he EPA also considers incidence (the number of persons estimated to suffer cancer or other serious health effects as a result of exposure to a pollutant) to be an important measure of the health risk to the exposed population. Incidence measures the extent of health risk to the exposed population as a whole, by providing an estimate of the occurrence of cancer or other serious health effects in the exposed population.” 54 FR at 38045. The agency went on to conclude that “estimated incidence would be weighed along with other health risk information in judging acceptability.” 54 FR at 38046. As explained more fully in our

Residual Risk Report to Congress,

the EPA does not define “rigid line[s] of acceptability,” but considers rather broad objectives to be weighed with a series of other health measures and factors (EPA-453/R-99-001, p. ES-11). The determination of what represents an “acceptable” risk is based on a judgment of “what risks are acceptable in the world in which we live” (

Residual Risk Report to Congress,

p. 178, quoting the

Vinyl Chloride

decision at 824 F.2d 1165) recognizing that our world is not risk-free.

In the Benzene NESHAP, we stated that “EPA will generally presume that if the risk to [the maximum exposed] individual is no higher than approximately 1 in 10 thousand, that risk level is considered acceptable.” 54 FR at 38045. We discussed the maximum individual lifetime cancer risk (or maximum individual risk (MIR)) as being “the estimated risk that a person living near a plant would have if he or she were exposed to the maximum pollutant concentrations for 70 years.”

Id.

We explained that this measure of risk “is an estimate of the upper bound of risk based on conservative assumptions, such as continuous exposure for 24 hours per day for 70 years.”

Id.

We acknowledge that maximum individual lifetime cancer risk “does not necessarily reflect the true risk, but displays a conservative risk level which is an upper bound that is unlikely to be exceeded.”

Id.

Understanding that there are both benefits and limitations to using maximum individual lifetime cancer risk as a metric for determining acceptability, we acknowledged in the 1989 Benzene NESHAP that “consideration of maximum individual risk * * * must take into account the strengths and weaknesses of this measure of risk.”

Id.

Consequently, the presumptive risk level of 100 in 1 million (1 in 10 thousand) provides a benchmark for judging the acceptability of maximum individual lifetime cancer risk, but does not constitute a rigid line for making that determination.

The agency also explained in the 1989 Benzene NESHAP: “[i]n establishing a presumption for MIR, rather than a rigid line for acceptability, the Agency intends to weigh it with a series of other health measures and factors. These include the overall incidence of cancer or other serious health effects within the exposed population, the numbers of persons exposed within each individual lifetime risk range and associated incidence within, typically, a 50 km [kilometer] exposure radius around facilities, the science policy assumptions and estimation uncertainties associated with the risk measures, weight of the scientific evidence for human health effects, other quantified or unquantified health effects, effects due to co-location of facilities, and co-emission of pollutants.”

Id.

In some cases, these health measures and factors taken together may provide a more realistic description of the magnitude of risk in the exposed population than that provided by maximum individual lifetime cancer risk alone. As explained in the Benzene NESHAP, “[e]ven though the risks judged ‘acceptable’ by the EPA in the first step of the

Vinyl Chloride

inquiry are already low, the second step of the inquiry, determining an ‘ample margin of safety,' again includes consideration of all of the health factors, and whether to reduce the risks even further * * *.” Beyond that information, additional factors relating to the appropriate level of control will also be considered, including costs and economic impacts of controls, technological feasibility, uncertainties and any other relevant factors. Considering all of these factors, the Agency will establish the standard at a level that provides an ample margin of safety to protect the public health, as required by CAA section 112.” 54 FR at 38046.

As discussed above, we apply a two-step process for developing standards to address residual risk. In the first step, the EPA determines whether risks are acceptable. This determination “considers all health information, including risk estimation uncertainty, and includes a presumptive limit on maximum individual lifetime [cancer] risk (MIR)

of approximately 1 in 10 thousand [i.e., 100 in 1 million].” 54 FR at 38045. In the second step of the process, the EPA sets the standard at a level that provides an ample margin of safety “in consideration of all health information, including the number of persons at risk levels higher than approximately 1 in 1 million, as well as other relevant factors, including costs and economic impacts, technological feasibility, and other factors relevant to each particular decision.”

Id.

Although defined as “maximum individual risk,” MIR refers only to cancer risk. MIR, one metric for assessing cancer risk, is the estimated risk were an individual to be exposed to the maximum level of a pollutant for a lifetime.

In past residual risk determinations, the EPA presented a number of human health risk metrics associated with emissions from the category under review, including: The MIR; the numbers of persons in various risk ranges; cancer incidence; the maximum noncancer hazard index (HI); and the maximum acute noncancer hazard. In estimating risks, the EPA considered source categories under review that are located near each other and that affect the same population. The EPA estimates risk based on the actual emissions from the source category under review as well as based on the emissions allowed pursuant to the source category MACT standard. The EPA also discussed and considered risk estimation uncertainties. The EPA is providing this same type of information in support of these actions.

The agency acknowledges that the Benzene NESHAP provides flexibility

regarding what factors the EPA might consider in making our determinations and how they might be weighed for each source category. In responding to comment on our policy under the Benzene NESHAP, the EPA explained that: “[t]he policy chosen by the Administrator permits consideration of multiple measures of health risk. Not only can the MIR figure be considered, but also incidence, the presence of noncancer health effects, and the uncertainties of the risk estimates. In this way, the effect on the most exposed individuals can be reviewed as well as the impact on the general public. These factors can then be weighed in each individual case. This approach complies with the

Vinyl Chloride

mandate that the Administrator ascertain an acceptable level of risk to the public by employing [her] expertise to assess available data. It also complies with the Congressional intent behind the CAA, which did not exclude the use of any particular measure of public health risk from the EPA's consideration with respect to CAA section 112 regulations and thereby implicitly permits consideration of any and all measures of health risk which the Administrator, in [her] judgment, believes are appropriate to determining what will `protect the public health.' ” 54 FR at 38057.

For example, the level of the MIR is only one factor to be weighed in determining acceptability of risks. The Benzene NESHAP explains “an MIR of approximately 1 in 10 thousand should ordinarily be the upper end of the range of acceptability. As risks increase above this benchmark, they become presumptively less acceptable under CAA section 112, and would be weighed with the other health risk measures and information in making an overall judgment on acceptability. Or, the agency may find, in a particular case, that a risk that includes MIR less than the presumptively acceptable level is unacceptable in the light of other health risk factors.” 54 FR at 38045. Similarly, with regard to the ample margin of safety analysis, the Benzene NESHAP states that: “EPA believes the relative weight of the many factors that can be considered in selecting an ample margin of safety can only be determined for each specific source category. This occurs mainly because technological and economic factors (along with the health-related factors) vary from source category to source category.” 54 FR at 38061.

B. Does this action apply to me?

The regulated industrial source category that is the subject of this proposal is listed in Table 2 of this preamble. Table 2 of this preamble is not intended to be exhaustive, but rather provides a guide for readers regarding the entities likely to be affected by this proposed action. These standards, once finalized, will be directly applicable to affected sources. Federal, State, local, and tribal government entities are not affected by this proposed action. The EPA defined the Secondary Aluminum source category in 1992 as any establishment using clean charge, aluminum scrap, or dross from aluminum production, as the raw material and performing one or more of the following processes: Scrap shredding, scrap drying/delacquering/decoating, thermal chip drying, furnace operations (i.e., melting, holding, sweating, refining, fluxing, or alloying), recovery of aluminum from dross, in-line fluxing, or dross cooling.

Table 2—NESHAP and Industrial Source Categories Affected by This Proposed Action

Source category

NESHAP

NAICS code

MACT code

Secondary Aluminum Production

331314

0044

Primary aluminum production facilities

331312

Aluminum sheet, plate, and foil manufacturing facilities

331315

Aluminum extruded product manufacturing facilities

331316

Other aluminum rolling and drawing facilities

331319

Aluminum die casting facilities

331521

Aluminum foundry facilities

331524

North American Industry Classification System.

Maximum Achievable Control Technology.

C. Where can I get a copy of this document and other related information?

In addition to being available in the docket, an electronic copy of this proposal will also be available on the World Wide Web (WWW) through the EPA's Technology Transfer Network (TTN). Following signature by the EPA Administrator, a copy of this proposed action will be posted on the TTN's policy and guidance page for newly proposed or promulgated rules at the following address:

http://www.epa.gov/ttn/atw/rrisk/rtrpg.html

. The TTN provides information and technology exchange in various areas of air pollution control including the residual risk and technology review (RTR) and includes source category descriptions and detailed emissions estimates and other data that were used as inputs to the risk assessments.

D. What should I consider as I prepare my comments for the EPA?

Submitting CBI.

Do not submit information containing CBI to the EPA through

http://www.regulations.gov

or email. Clearly mark the part or all of the information that you claim to be CBI. For CBI information on a disk or CD ROM that you mail to the 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. If you submit a CD ROM or disk that does not contain CBI, mark the outside of the disk or CD ROM clearly that it does not contain CBI. Information not marked as CBI will be included in the public docket and the EPA's electronic public docket without prior notice. Information marked as CBI will not be disclosed except in accordance with procedures set forth in 40 CFR part 2. 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, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711, Attention Docket ID Number EPA-HQ-OAR-2010-0544.

II. Background

A. What is this source category and how did the MACT standard regulate its HAP emissions?

The Secondary Aluminum Production source category includes facilities that produce aluminum from scrap aluminum material and consists of the following operations: (1) Preprocessing of scrap aluminum, including size reduction and removal of oils, coatings, and other contaminants; (2) Furnace operations including melting, in-furnace refining, fluxing, and tapping; (3) Additional refining, by means of in-line fluxing; and (4) Cooling of dross. The following sections include descriptions of the affected sources in the secondary aluminum production source category, the origin of HAP emissions from these affected sources, and factors affecting the emissions.

Scrap aluminum is often preprocessed prior to melting. Preprocessing steps may include shredding to reduce the size of aluminum scrap; drying of oily scrap such as machine turnings and borings; and/or heating in a scrap dryer, delacquering kiln or decoating kiln to remove coatings or other contaminants that may be present on the scrap. Heating of high iron content scrap in a sweat furnace to reclaim the aluminum content is also a preprocessing operation.

Crushing, shredding and grinding operations are used to reduce the size of scrap aluminum. Particulate matter (PM) and HAP metals emissions are generated as dust from coatings and other contaminants contained in the scrap aluminum as they are processed.

A chip dryer is used to evaporate oil and/or moisture from uncoated aluminum chips and borings. Chip dryers typically operate at temperatures ranging between 150 °C to 400 °C (300 °F to 750 °F). An uncontrolled chip dryer may emit dioxins and furans (D/F) and total hydrocarbons (THC), of which some fraction is organic HAP.

Painted and/or coated materials are processed in a scrap dryer/delacquering kiln/decoating kiln to remove coatings and other contaminants that may be present in the scrap prior to melting. Coatings, oils, grease, and lubricants represent up to 20 percent of the total weight of these materials. Organic HAP, D/F, and inorganic HAPs including particulate metal HAP are emitted during the drying/delacquering/decoating process.

Used beverage containers (UBC) comprise a major portion of the recycled aluminum scrap used as feedstock by the industry. In scrap drying/delacquering/decoating operations, UBC and other post-consumer, coated products (e.g., aluminum siding) are heated to an exit temperature of up to 540 °C (1,000 °F) to volatilize and remove various organic contaminants such as paints, oils, lacquers, rubber, and plastic laminates prior to melting. An uncontrolled scrap dryer/delacquering kiln/decoating kiln emits PM (of which some fraction is particulate metal HAP), HCl, THC (of which some fraction is organic HAP), and D/F.

A sweat furnace is typically used to reclaim (or “sweat”) the aluminum from scrap with high levels of iron. These furnaces operate in batch mode at a temperature that is high enough to melt the aluminum but not high enough to melt the iron. The aluminum melts and flows out of the furnace while the iron remains in the furnace in solid form. The molten aluminum can be cast into sows, ingots, or T-bars that are used as feedstock for aluminum melting and refining furnaces. Alternately, molten aluminum can be fed directly to a melting or refining furnace. An uncontrolled sweat furnace may emit D/F.

Process (i.e. melting, holding or refining) furnaces are refractory-lined metal vessels heated by an oil or gas burner to achieve a metal temperature of about 760 °C (1,400 °F). The melting process begins with the charging of scrap into the furnace. A gaseous (typically, chlorine) or salt flux may be added to remove impurities and reduce aluminum oxidation. Once molten, the chemistry of the bath is adjusted by adding selected scrap or alloying agents, such as silicon. Salt and other fluxes contain chloride and fluoride compounds that may be released when introduced to the bath. HCl may also be released when chlorine-containing contaminants (such as polyvinyl chloride coatings) present in some types of scrap are introduced to the bath. Argon and nitrogen fluxes are not reactive and do not produce HAPs. In a sidewell melting furnace, fluxing is performed in the sidewell and fluxing emissions from the sidewell are controlled. In this type of furnace, fluxing is not typically done in the hearth and hearth emissions (which include products of combustion from the oil and gas fired furnaces) are typically uncontrolled.

Process furnaces may process contaminated scrap which can result in HAP emissions. In addition, fluxing agents may contain HAPs, some fraction of which is emitted from the furnace. Process furnaces are significant sources of HAP emissions in the secondary aluminum industry. An uncontrolled melting furnace which processes contaminated scrap and uses reactive fluxes emits PM (of which some fraction is particulate metal HAP), HCl, and D/F.

Process furnaces are divided into group 1 and group 2 furnaces. Group 1 furnaces are unrestricted in the type of scrap they process and the type of fluxes they can use. Group 2 furnaces process only clean charge and conduct no reactive fluxing.

Dross-only furnaces are furnaces dedicated to reclamation of aluminum from drosses formed during the melting/holding/alloying operations carried out in other furnaces. Exposure to the atmosphere causes the molten aluminum to oxidize, and the flotation of the impurities to the surface along with any salt flux creates “dross.” Prior to tapping, the dross is periodically skimmed from the surface of the aluminum bath and cooled. Dross-only furnaces are typically rotary barrel furnaces (also known as salt furnaces). A dross-only furnace without controls emits PM (of which some fraction is particulate metal HAP).

Rotary dross coolers are devices used to cool dross in a rotating, water-cooled drum. A rotary dross cooler without controls emits PM (of which some fraction is particulate metal HAP).

In-line fluxers are devices used for aluminum refining, including degassing, outside the furnace. The process involves the injection of chlorine, argon, nitrogen or other gases to achieve the desired metal purity. Argon and nitrogen are not reactive and do not produce HAPs. In-line fluxers are found primarily at facilities that manufacture very high quality aluminum or in facilities with no other means of degassing. An in-line fluxer operating without emission controls emits HCl and PM.

The Secondary Aluminum Production NESHAP was promulgated on March 23, 2000, (65 FR 15690) and codified as 40 CFR part 63, subpart RRR. The rule was amended at 67 FR 79808, December 30, 2002; 69 FR 53980, September 3, 2004; 70 FR 57513, October 3, 2005 and 70 FR 75320, December 19, 2005. The existing subpart RRR NESHAP regulates HAP emissions from secondary aluminum production facilities that are major sources of HAP that operate aluminum scrap shredders, thermal chip dryers, scrap dryers/delacquering kilns/decoating kilns, group 1 furnaces, group 2 furnaces, sweat furnaces, dross only furnaces, rotary dross coolers, and secondary aluminum processing units (SAPUs). The SAPUs include group 1 furnaces and in-line fluxers. The subpart RRR NESHAP regulates HAP

emissions from secondary aluminum production facilities that are area sources of HAP only with respect to emissions of dioxins/furans (D/F) from thermal chip dryers, scrap dryers/delacquering kilns/decoating kilns, group 1 furnaces, sweat furnaces, and SAPUs.

The secondary aluminum industry consists of approximately 161 secondary aluminum production facilities, of which the EPA estimates 53 to be major sources of HAP. Several of the secondary aluminum facilities are co-located with primary aluminum, coil coating, and possibly other source category facilities. Natural gas boilers or process heaters may also be co-located at a few secondary aluminum facilities.

The HAP emitted by these facilities are metals, organic HAP, D/F, hydrogen chloride (HCl), and hydrogen fluoride (HF).

The standards promulgated in 2000 established emission limits for particulate matter (PM) as a surrogate for metal HAP, total hydrocarbons (THC) as a surrogate for organic HAP other than D/F, D/F expressed as toxicity equivalents, and HCl as a surrogate for acid gases including HF, chlorine and fluorine. HAP are emitted from the following affected sources: aluminum scrap shredders (subject to PM standards), thermal chip dryers (subject to standards for THC and D/F), scrap dryers/delacquering kilns/decoating kilns (subject to standards for PM, D/F, HCl and THC), sweat furnaces (subject to D/F standards), dross-only furnaces (subject to PM standards), rotary dross coolers (subject to PM standards), group 1 furnaces (subject to standards for PM, HCl and D/F), and in-line fluxers (subject to standards for PM and HCl). Group 2 furnaces and certain in-line fluxers are subject to work practice standards. Table 3 provides a summary of the current MACT emissions limits for existing and new sources under the 2000 NESAHP and the 2005 amendments.

EP14FE12.031

EP14FE12.032

EP14FE12.033

Control devices currently in use to reduce emissions from affected sources subject to the subpart RRR NESHAP include fabric filters for control of PM from aluminum scrap shredders; afterburners for control of THC and D/F from thermal chip dryers; afterburners plus lime-injected fabric filters for control of PM, HCl, THC, and D/F from scrap dryers/delacquering kilns/decoating kilns; afterburners for control of D/F from sweat furnaces; fabric filters for control of PM from dross-only furnaces and rotary dross coolers; lime-injected fabric filters for control of PM and HCl from in-line fluxers; and lime-injected fabric filters for control of PM, HCl and D/F from group 1 furnaces. All affected sources with add-on controls are also subject to design requirements and operating limits to limit fugitive emissions.

Compliance with the emission limits in the current rule is demonstrated by an initial performance test for each affected source. Repeat performance tests are required every 5 years. Area sources are only subject to one-time performance tests for D/F. After the compliance tests, facilities are required to monitor various control parameters or conduct other types of monitoring to ensure continuous compliance with the MACT standards. Owners or operators of sweat furnaces that operate an afterburner that meets temperature and residence time requirements are not required to conduct performance tests.

B. What data collection activities were conducted to support this action?

For the Secondary Aluminum Production source category, we compiled a dataset from two primary sources: (1) An all-company information collection request (ICR) sent to companies in February 2011, and (2) a nine-company testing ICR, sent in May 2010.

Responses to the all-company ICR contained data on stack release characteristics such as height, volumetric flow rate, temperature, and location (latitude/longitude) coordinates. Responses to the all-company ICR also contained data on maximum production capacity and actual production in tpy and testing results for pollutants regulated under subpart RRR.

As mentioned above, the pollutants regulated under subpart RRR are PM, HCl, THC and D/F. PM is a surrogate for metal HAP and THC is a surrogate for organic HAP. Since subpart RRR compliance testing is performed for the surrogates PM and THC, there are limited test data available for speciated metal HAP and organic HAP emissions. Therefore, responses to the nine-company testing ICR were used to extrapolate the PM and THC testing results reported in the all-company ICR to specific metal and organic HAP emissions. In the nine-company testing ICR, companies were asked to provide speciated metal HAP concentrations (e.g. arsenic, cadmium, cobalt, lead, nickel, etc.) in the particulate collected by fabric filters. For more information on the selection of these facilities, see the Draft

Technical Support Document for the Secondary Aluminum Production Source Category

located in the docket. These data were then used to estimate speciated metal HAP emissions, based on the PM emissions reported in the all-company ICR. For example, if a response to the all-company ICR indicated a particular piece of equipment at a specific secondary aluminum facility had 10 tpy of PM emissions, and based on an analysis of the results of the nine-company testing ICR the EPA determined that the cobalt concentration in the fabric filter particulate matter catch was 20 parts-per-million (ppm), the estimated emissions of cobalt would be 0.0002 tpy. In the nine-company testing ICR, companies were also required to conduct speciated organic HAP and THC emission testing for the two types of equipment that have THC limits under subpart RRR, scrap dryer/delacquering/decoating kilns and thermal chip dryers. The speciated organic HAPs for which data were provided included volatile HAPs (e.g., benzene, chloroprene, toluene, etc.) and semi-volatile HAPs (anthracene, chrysene, naphthalene, etc.).

Using the reported amount of charge or production for the most recent year and the reported test results (in lb per ton of charge) from the all-company ICR, emissions were calculated. Where test results from the all-company ICR responses were expressed in terms of PM and THC surrogates, emissions were

converted to speciated metal and organic HAP emissions using the nine-company test results, as described above. Allowable and actual emissions were calculated for each piece of equipment. The derivation of allowable emissions estimates is described in Section III of this preamble.

The emissions data, calculations and risk assessment inputs for the Secondary Aluminum Production source category are described further in the memorandum

Draft Development of the RTR Risk Modeling Dataset for the Secondary Aluminum Production Source Category

which is available in the docket for this proposed rulemaking.

III. Analyses Performed

In this section we describe the analyses performed to support the proposed decisions for the RTR for this source category.

A. How did we estimate risks posed by the source category?

The EPA conducted risk assessments that provide estimates of the MIR posed by the HAP emissions for each source in the category, the HI for chronic exposures to HAP with the potential to cause noncancer health effects, and the hazard quotient (HQ) for acute exposures to HAP with the potential to cause noncancer health effects. The assessments also provided estimates of the distribution of cancer risks within the exposed populations, cancer incidence and an evaluation of the potential for adverse environmental effects for the source category. The risk assessments consisted of seven primary steps, as discussed below. The docket for this rulemaking contains the following document which provides more information on the risk assessment inputs and models:

Draft Residual Risk Assessment for the Secondary Aluminum Production Source Category.

The methods used to assess risks (as described in the six primary steps below) are consistent with those peer-reviewed by a panel of the EPA's Science Advisory Board (SAB) in 2009 and described in their peer review report issued in 2010;

they are also consistent with the key recommendations contained in that report.

U.S. EPA SAB.

Risk and Technology Review (RTR) Risk Assessment Methodologies: For Review by the EPA's Science Advisory Board with Case Studies—MACT I Petroleum Refining Sources and Portland Cement Manufacturing,

May 2010.

1. Establishing the Nature and Magnitude of Actual Emissions and Identifying the Emissions Release Characteristics

As discussed in Section II.B. of this preamble, we used a dataset based on the estimated actual and allowable emissions as the basis for the risk assessment. This dataset was based on responses to an Information Collection Request (ICR) sent to approximately 425 facilities potentially subject to the subpart RRR NESHAP. Approximately 161 sources subject to the NESHAP responded, approximately 166 facilities confirmed that they were not subject to the NESHAP and no responses were received to approximately 51 ICRs. In addition to these responses, as described in section II.B, an earlier ICR was sent to 9 companies requiring them to provide speciated metal and organic HAP concentrations for purposes of calculating speciated HAP emissions based on reported emissions of the surrogate pollutants, THC and PM. As part of our quality assurance (QA) process, we checked the coordinates of every facility in the dataset using tools such as Google Earth. We corrected coordinates that were found to be incorrect. We also performed QA of the emissions data and release characteristics to identify outliers and then confirmed or corrected the data.

2. Establishing the Relationship Between Actual Emissions and MACT-Allowable Emissions Levels

The available emissions data in the MACT dataset include estimates of the mass of HAP actually emitted during the specified annual time period. These “actual” emission levels are often lower than the emission levels that a facility might be allowed to emit and still comply with the MACT standards. The emissions level allowed to be emitted by the MACT standards is referred to as the “MACT-allowable” emissions level. This represents the highest emissions level that could be emitted by the facility without violating the MACT standards.

We discussed the use of both MACT-allowable and actual emissions in the final Coke Oven Batteries residual risk rule (70 FR 19998-19999, April 15, 2005) and in the proposed and final Hazardous Organic NESHAP residual risk rules (71 FR 34428, June 14, 2006, and 71 FR 76609, December 21, 2006, respectively). In those previous actions, we noted that assessing the risks at the MACT-allowable level is inherently reasonable since these risks reflect the maximum level sources could emit and still comply with national emission standards. But we also explained that it is reasonable to consider actual emissions, where such data are available, in both steps of the risk analysis, in accordance with the Benzene NESHAP. (54 FR 38044, September 14, 1989.)

As discussed above, allowable and actual emissions were calculated for each piece of equipment. The estimates of actual emissions are described in Section II of this preamble.

Allowable emissions for this source category were calculated by assuming emissions were at the maximum level allowed by the MACT standard (i.e., we assume emissions would be emitted at a level equal to the MACT emission limit). Nevertheless, we note that these are conservative estimates of allowable emissions. It is unlikely that emissions would be at the maximum limit at all times because sources cannot emit HAP at a level that is exactly equal to the limit at all times and remain in compliance with the standard due to day-to-day variability in process operations and emissions. On average, facilities must emit at some level below the MACT limit to ensure that they are always in compliance.

The derivation of actual and allowable emissions estimates are discussed in more detail in the document

Draft Development of the RTR Emissions Dataset for the Secondary Aluminum Production Source Category

which is available in the docket for this proposed rulemaking.

3. Conducting Dispersion Modeling, Determining Inhalation Exposures and Estimating Individual and Population Inhalation Risks

Both long-term and short-term inhalation exposure concentrations and health risks from each facility in the source category were estimated using the Human Exposure Model (HEM) (Community and Sector HEM-3 version 1.1.0). The HEM-3 performs three primary risk assessment activities: (1) Conducting dispersion modeling to estimate the concentrations of HAP in ambient air, (2) estimating long-term and short-term inhalation exposures to individuals residing within 50 km of the modeled sources and (3) estimating individual and population-level inhalation risks using the exposure estimates and quantitative dose-response information.

The dispersion model used by HEM-3 is AERMOD, which is one of the EPA's preferred models for assessing pollutant concentrations from industrial

facilities.

To perform the dispersion modeling and to develop the preliminary risk estimates, HEM-3 draws on three data libraries. The first is a library of meteorological data, which is used for dispersion calculations. This library includes 1 year (1991) of hourly surface and upper air observations for more than 158 meteorological stations, selected to provide coverage of the United States and Puerto Rico. A second library of United States Census Bureau census block

internal point locations and populations provides the basis of human exposure calculations (Census, 2000). In addition, for each census block, the census library includes the elevation and controlling hill height, which are also used in dispersion calculations. A third library of pollutant unit risk factors and other health benchmarks is used to estimate health risks. These risk factors and health benchmarks are the latest values recommended by the EPA for HAP and other toxic air pollutants. These values are available at

http://www.epa.gov/ttn/atw/toxsource/summary.html

and are discussed in more detail later in this section.

U.S. EPA. Revision to the

Guideline on Air Quality Models: Adoption of a Preferred General Purpose (Flat and Complex Terrain) Dispersion Model and Other Revisions

(70 FR 68218, November 9, 2005).

A census block is generally the smallest geographic area for which census statistics are tabulated.

In developing the risk assessment for chronic exposures, we used the estimated annual average ambient air concentration of each of the HAP emitted by each source for which we have emissions data in the source category. The air concentrations at each nearby census block centroid were used as a surrogate for the chronic inhalation exposure concentration for all the people who reside in that census block. We calculated the MIR for each facility as the cancer risk associated with a continuous lifetime (24 hours per day, 7 days per week, and 52 weeks per year for a 70-year period) exposure to the maximum concentration at the centroid of an inhabited census block. Individual cancer risks were calculated by multiplying the estimated lifetime exposure to the ambient concentration of each of the HAP (in micrograms per cubic meter) by its unit risk estimate (URE), which is an upper bound estimate of an individual's probability of contracting cancer over a lifetime of exposure to a concentration of 1 microgram of the pollutant per cubic meter of air. For residual risk assessments, we generally use URE values from the EPA's Integrated Risk Information System (IRIS). For carcinogenic pollutants without the EPA IRIS values, we look to other reputable sources of cancer dose-response values, often using California EPA (CalEPA) URE values, where available. In cases where new, scientifically credible dose-response values have been developed in a manner consistent with the EPA guidelines and have undergone a peer review process similar to that used by the EPA, we may use such dose-response values in place of, or in addition to, other values, if appropriate.

Incremental individual lifetime cancer risks associated with emissions from the source category were estimated as the sum of the risks for each of the carcinogenic HAP (including those classified as carcinogenic to humans, likely to be carcinogenic to humans and suggestive evidence of carcinogenic potential

) emitted by the modeled source. Cancer incidence and the distribution of individual cancer risks for the population within 50 km of any source were also estimated for the source category as part of these assessments by summing individual risks. A distance of 50 km is consistent with both the analysis supporting the 1989 Benzene NESHAP (54 FR 38044) and the limitations of Gaussian dispersion models, including AERMOD.

These classifications also coincide with the terms “known carcinogen, probable carcinogen and possible carcinogen,” respectively, which are the terms advocated in the EPA's previous

Guidelines for Carcinogen Risk Assessment,

published in 1986 (51 FR 33992, September 24, 1986). Summing the risks of these individual compounds to obtain the cumulative cancer risks is an approach that was recommended by the EPA's SAB in their 2002 peer review of EPA's NATA entitled,

NATA—Evaluating the National-scale Air Toxics Assessment 1996 Data—an SAB Advisory,

available at:

http://yosemite.epa.gov/sab/sabproduct.nsf/214C6E915BB04E14852570CA007A682C/$File/ecadv02001.pdf.

To assess risk of noncancer health effects from chronic exposures, we summed the HQ for each of the HAP that affects a common target organ system to obtain the HI for that target organ system (or target organ-specific HI, TOSHI). The HQ for chronic exposures is the estimated chronic exposure divided by the chronic reference level, which is either the EPA reference concentration (RfC), defined as “an estimate (with uncertainty spanning perhaps an order of magnitude) of a continuous inhalation exposure to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime,” or, in cases where an RfC from the EPA's IRIS database is not available, a value from the following prioritized sources: (1) The agency for Toxic Substances and Disease Registry Minimum Risk Level, which is defined as “an estimate of daily human exposure to a substance that is likely to be without an appreciable risk of adverse effects (other than cancer) over a specified duration of exposure”; (2) the CalEPA Chronic Reference Exposure Level (REL), which is defined as “the concentration level at or below which no adverse health effects are anticipated for a specified exposure duration;” or (3) as noted above, a scientifically credible dose-response value that has been developed in a manner consistent with the EPA guidelines and has undergone a peer review process similar to that used by the EPA, in place of or in concert with other values.

Screening estimates of acute exposures and risks were also evaluated for each of the HAP at the point of highest off-site exposure for each facility (i.e., not just the census block centroids), assuming that a person is located at this spot at a time when both the peak (hourly) emission rates from each emission point at the facility and worst-case dispersion conditions occur. The acute HQ is the estimated acute exposure divided by the acute dose-response value. In each case, acute HQ values were calculated using best available, short-term dose-response values. These acute dose-response values, which are described below, include the acute REL, acute exposure guideline levels (AEGL) and emergency response planning guidelines (ERPG) for 1-hour exposure durations. As discussed below, we used conservative assumptions for emission rates, meteorology and exposure location for our acute analysis.

As described in the CalEPA's

Air Toxics Hot Spots Program Risk Assessment Guidelines, Part I, The Determination of Acute Reference Exposure Levels for Airborne Toxicants,

an acute REL value (

http://www.oehha.ca.gov/air/pdf/acuterel.pdf

) is defined as “the concentration level at or below which no adverse health effects are anticipated for a specified exposure duration.” Acute REL values are based on the most sensitive, relevant, adverse health effect reported in the medical and toxicological literature. Acute REL values are designed to protect the most sensitive sub-populations (e.g., asthmatics) by the inclusion of margins of safety. Since margins of safety are incorporated to address data gaps and uncertainties, exceeding the acute REL does not automatically indicate an adverse health impact.

AEGL values were derived in response to recommendations from the National Research Council (NRC). As described in

Standing Operating Procedures (SOP) of the National Advisory Committee on Acute Exposure Guideline Levels for Hazardous Substances

(

http://www.epa.gov/opptintr/aegl/pubs/sop.pdf

“the NRC's previous name for acute exposure levels—community emergency exposure levels—was replaced by the term AEGL to reflect the broad application of these values to planning, response, and prevention in the community, the workplace, transportation, the military, and the remediation of Superfund sites.” This document also states that AEGL values “represent threshold exposure limits for the general public and are applicable to emergency exposures ranging from 10 minutes to eight hours.” The document lays out the purpose and objectives of AEGL by stating (page 21) that “the primary purpose of the AEGL program and the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances is to develop guideline levels for once-in-a-lifetime, short-term exposures to airborne concentrations of acutely toxic, high-priority chemicals.” In detailing the intended application of AEGL values, the document states (page 31) that “[i]t is anticipated that the AEGL values will be used for regulatory and nonregulatory purposes by U.S. Federal and state agencies and possibly the international community in conjunction with chemical emergency response, planning, and prevention programs. More specifically, the AEGL values will be used for conducting various risk assessments to aid in the development of emergency preparedness and prevention plans, as well as real-time emergency response actions, for accidental chemical releases at fixed facilities and from transport carriers.”

NAS, 2001.

Standing Operating Procedures for Developing Acute Exposure Levels for Hazardous Chemicals,

page 2.

The AEGL-1 value is then specifically defined as “the airborne concentration of a substance above which it is predicted that the general population, including susceptible individuals, could experience notable discomfort, irritation, or certain asymptomatic nonsensory effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure.” The document also notes (page 3) that, “Airborne concentrations below AEGL-1 represent exposure levels that can produce mild and progressively increasing but transient and nondisabling odor, taste, and sensory irritation or certain asymptomatic, nonsensory effects.” Similarly, the document defines AEGL-2 values as “the airborne concentration (expressed as ppm or mg/m

) of a substance above which it is predicted that the general population, including susceptible individuals, could experience irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape.”

ERPG values are derived for use in emergency response, as described in the American Industrial Hygiene Association's document entitled,

Emergency Response Planning Guidelines (ERPG) Procedures and Responsibilities

(

http://www.aiha.org/1documents/committees/ERPSOPs2006.pdf

) which states that, “Emergency Response Planning Guidelines were developed for emergency planning and are intended as health based guideline concentrations for single exposures to chemicals.”

The ERPG-1 value is defined as “the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing other than mild transient adverse health effects or without perceiving a clearly defined, objectionable odor.” Similarly, the ERPG-2 value is defined as “the maximum airborne concentration below which it is believed that nearly all individuals could be exposed for up to 1 hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual's ability to take protective action.”

ERP Committee Procedures and Responsibilities.

November 1, 2006. American Industrial Hygiene Association.

As can be seen from the definitions above, the AEGL and ERPG values include the similarly defined severity levels 1 and 2. For many chemicals, a severity level 1 value AEGL or ERPG has not been developed; in these instances, higher severity level AEGL-2 or ERPG-2 values are compared to our modeled exposure levels to assess potential for acute concerns.

Acute REL values for 1-hour exposure durations are typically lower than their corresponding AEGL-1 and ERPG-1 values. Even though their definitions are slightly different, AEGL-1 values are often similar to the corresponding ERPG-1 values, and AEGL-2 values are often similar to ERPG-2 values. Maximum HQ values from our acute screening risk assessments typically result when basing them on the acute REL value for a particular pollutant. In cases where our maximum acute HQ value exceeds 1, we also report the HQ value based on the next highest acute dose-response value (usually the AEGL-1 and/or the ERPG-1 value).

To develop screening estimates of acute exposures, we developed estimates of maximum hourly emission rates by multiplying the average actual annual hourly emission rates by a factor to cover routinely variable emissions. We chose the factor to use based on process knowledge and engineering judgment and with awareness of a Texas study of short-term emissions variability, which showed that most peak emissions events, in a heavily-industrialized 4-county area (Harris, Galveston, Chambers, and Brazoria Counties, Texas) were less than twice the annual average hourly emissions rate. The highest peak emissions event was 74 times the annual average hourly emissions rate, and the 99th percentile ratio of peak hourly emissions rate to the annual average hourly emissions rate was 9.

This analysis is provided in Appendix 4 of the

Draft Residual Risk Assessment for Secondary Aluminum Production

which is available in the docket for this action. Considering this analysis, unless specific process knowledge or data are available to provide an alternate value, to account for more than 99 percent of the peak hourly emissions, we generally apply the assumption to most source categories that the maximum one-hour emissions rate from any source other than those resulting in fugitive dust emissions are 10 times the average annual hourly emissions rate for that source. We use a factor other than 10 in some cases if we have information that indicates that a different factor is appropriate for a particular source category. For this source category however, there was no such information available and the default factor of 10 was used in the acute screening process.

See

http://www.tceq.state.tx.us/compliance/field_ops/eer/index.html

or docket to access the source of these data.

When worst-case HQ values from the initial acute screen step were less than 1, acute impacts were deemed negligible and no further analysis was performed. In the cases where any worst-case acute HQ from the screening step was greater than 1, additional site-specific data were considered to develop a more refined estimate of the potential for acute impacts of concern. However, for this source category no acute values were greater than 1 and therefore, further refinement was not performed.

Ideally, we would prefer to have continuous measurements over time to

see how the emissions vary by each hour over an entire year. Having a frequency distribution of hourly emission rates over a year would allow us to perform a probabilistic analysis to estimate potential threshold exceedances and their frequency of occurrence. Such an evaluation could include a more complete statistical treatment of the key parameters and elements adopted in this screening analysis. However, we recognize that having this level of data is rare, hence our use of the multiplier approach.

To better characterize the potential health risks associated with estimated acute exposures to HAP, and in response to a key recommendation from the SAB's peer review of the EPA's RTR risk assessment methodologies,

we generally examine a wider range of available acute health metrics than we do for our chronic risk assessments. This is in response to the SAB's acknowledgement that there are generally more data gaps and inconsistencies in acute reference values than there are in chronic reference values.

The SAB peer review of RTR Risk Assessment Methodologies is available at:

http://yosemite.epa.gov/sab/sabproduct.nsf/4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf.

Comparisons of the estimated maximum off-site 1-hour exposure levels are not typically made to occupational levels for the purpose of characterizing public health risks in RTR assessments. This is because they are developed for working age adults and are not generally considered protective for the general public. We note that occupational ceiling values are, for most chemicals, set at levels higher than a 1-hour AEGL-1.

4. Conducting Multipathway Exposure and Risk Screening

The potential for significant human health risks due to exposures via routes other than inhalation (i.e., multipathway exposures) and the potential for adverse environmental impacts were evaluated in a two-step process. In the first step, we determined whether any facilities emitted any HAP known to be persistent and bio-accumulative in the environment (PB-HAP). There are 14 PB-HAP compounds or compound classes identified for this screening in EPA's

Air Toxics Risk Assessment Library

(available at

http://www.epa.gov/ttn/fera/risk_atra_vol1.html

). They are cadmium compounds, chlordane, chlorinated dibenzodioxins and furans, dichlorodiphenyldichloroethylene, heptachlor, hexachlorobenzene, hexachlorocyclohexane, lead compounds, mercury compounds, methoxychlor, polychlorinated biphenyls, POM, toxaphene, and trifluralin. Since three of these PB-HAP (cadmium compounds, POM and chlorinated D/F) are emitted by at least one facility in this source category, we proceeded to the second step of the evaluation. In this step, we determined whether the facility-specific emission rates of each of the emitted PB-HAP were large enough to create the potential for significant non-inhalation human or environmental risks under, worst-case conditions. To facilitate this step, we developed emission rate thresholds for each PB-HAP using a hypothetical worst-case screening exposure scenario developed for use in conjunction with the EPA's TRIM.FaTE model. The hypothetical screening scenario was subjected to a sensitivity analysis to ensure that its key design parameters were established such that environmental media concentrations were not underestimated (i.e., to minimize the occurrence of false negatives or results that suggest that risks might be acceptable when, in fact, actual risks are high) and to also minimize the occurrence of false positives for human health endpoints. We call this application of the TRIM.FaTE model TRIM-Screen. The facility-specific emission rates of each of the PB-HAP were compared to the TRIM-Screen emission threshold values for each of the PB-HAP identified in the source category datasets to assess the potential for significant human health risks or environmental risks via non-inhalation pathways. See Section IV for results of this screening analysis.

5. Conducting Other Risk-Related Analyses: Facilitywide Assessments

To put the source category risks in context, for our residual risk reviews, we also typically examine the risks from the entire “facility,” where the facility includes all HAP-emitting operations within a contiguous area and under common control. In these facilitywide assessments we examine the HAP emissions not only from the source category of interest, but also emissions of HAP from all other emissions sources at the facility. For the secondary aluminum source category, a facilitywide assessment was performed for all major sources.

A facilitywide assessment was not conducted for area sources. By definition, no major sources of HAP (e.g., primary aluminum production or coil coating operations) are collocated with any of the secondary aluminum area sources. Further, at many area sources, equipment subject to the Secondary Aluminum NESHAP is the only HAP-emitting equipment. Therefore, the most significant HAP emissions from area sources were already being considered under the area source risk assessment, and low levels of HAP emissions from equipment not subject to the Secondary Aluminum NESHAP at these facilities would not contribute appreciably to the risk profile. The results of the facilitywide assessment for major sources are provided in Section IV.

6. Considering Uncertainties in Risk Assessment

Uncertainty and the potential for bias are inherent in all risk assessments, including those performed for the Secondary Aluminum source category addressed in this proposal. Although uncertainty exists, we believe that our approach, which used conservative tools and assumptions, ensures that our decisions are health-protective. A brief discussion of the uncertainties in the emissions datasets, dispersion modeling, inhalation exposure estimates and dose-response relationships follows below. A more thorough discussion of these uncertainties is included in the risk assessment documentation (referenced earlier) available in the docket for this action.

a. Uncertainties in the Emissions Datasets

Although the development of the MACT dataset involved QA/quality control processes, the accuracy of emissions values will vary depending on the source of the data, the degree to which data are incomplete or missing, the degree to which assumptions made to complete the datasets are accurate, errors in estimating emissions values and other factors. The emission estimates considered in this analysis were generally developed from one-time or periodic performance tests that do not reflect short-term fluctuations during the course of a year or variations from year to year.

The estimates of peak hourly emission rates for the acute effects screening assessment were based on a default factor of 10 applied to the average annual hourly emission rate, which is intended to account for emission fluctuations due to normal facility operations.

b. Uncertainties in Dispersion Modeling

While the analysis employed the EPA's recommended regulatory dispersion model, AERMOD, we recognize that there is uncertainty in ambient concentration estimates

associated with any model, including AERMOD. In circumstances where we had to choose between various model options, where possible, model options (e.g., rural/urban, plume depletion, chemistry) were selected to provide an overestimate of ambient air concentrations of the HAP rather than underestimates. However, because of practicality and data limitation reasons, some factors (e.g., meteorology, building downwash) have the potential in some situations to overestimate or underestimate ambient impacts. For example, meteorological data were taken from a single year (1991), and facility locations can be a significant distance from the sites where these data were taken. Despite these uncertainties, we believe that at off-site locations and census block centroids, the approach considered in the dispersion modeling analysis should generally yield overestimates of ambient HAP concentrations.

c. Uncertainties in Inhalation Exposure

The effects of human mobility on exposures were not included in the assessment. Specifically, short-term mobility and long-term mobility between census blocks in the modeling domain were not considered.

The assumption of not considering short or long-term population mobility does not bias the estimate of the theoretical MIR, nor does it affect the estimate of cancer incidence since the total population number remains the same. It does, however, affect the shape of the distribution of individual risks across the affected population, shifting it toward higher estimated individual risks at the upper end and reducing the number of people estimated to be at lower risks, thereby increasing the estimated number of people at specific risk levels.

Short-term mobility is movement from one micro-environment to another over the course of hours or days. Long-term mobility is movement from one residence to another over the course of a lifetime.

In addition, the assessment predicted the chronic exposures at the centroid of each populated census block as surrogates for the exposure concentrations for all people living in that block. Using the census block centroid to predict chronic exposures tends to over-predict exposures for people in the census block who live further from the facility, and under-predict exposures for people in the census block who live closer to the facility. Thus, using the census block centroid to predict chronic exposures may lead to a potential understatement or overstatement of the true maximum impact, but it is an unbiased estimate of average risk and incidence.

The assessments evaluate the cancer inhalation risks associated with continuous pollutant exposures over a 70-year period, which is the assumed lifetime of an individual. In reality, both the length of time that modeled emissions sources at facilities actually operate (i.e., more or less than 70 years) and the domestic growth or decline of the modeled industry (i.e., the increase or decrease in the number or size of United States facilities) will influence the risks posed by a given source category. Depending on the characteristics of the industry, these factors will, in most cases, result in an overestimate both in individual risk levels and in the total estimated number of cancer cases. However, in rare cases, where a facility maintains or increases its emission levels beyond 70 years, residents live beyond 70 years at the same location, and the residents spend most of their days at that location, then the risks could potentially be underestimated. Annual cancer incidence estimates from exposures to emissions from these sources would not be affected by uncertainty in the length of time emissions sources operate.

The exposure estimates used in these analyses assume chronic exposures to ambient levels of pollutants. Because most people spend the majority of their time indoors, actual exposures may not be as high, depending on the characteristics of the pollutants modeled. For many of the HAP, indoor levels are roughly equivalent to ambient levels, but for very reactive pollutants or larger particles, these levels are typically lower. This factor has the potential to result in an overstatement of 25 to 30 percent of exposures.

U.S. EPA.

National-Scale Air Toxics Assessment for 1996.

(EPA 453/R-01-003; January 2001; page 85.)

In addition to the uncertainties highlighted above, there are several other factors specific to the acute exposure assessment. The accuracy of an acute inhalation exposure assessment depends on the simultaneous occurrence of independent factors that may vary greatly, such as hourly emissions rates, meteorology, and human activity patterns. In this assessment, we assume that individuals remain for 1 hour at the point of maximum ambient concentration as determined by the co-occurrence of peak emissions and worst-case meteorological conditions. These assumptions would tend to overestimate actual exposures since it is unlikely that a person would be located at the point of maximum exposure during the time of worst-case impact.

d. Uncertainties in Dose-Response Relationships

There are uncertainties inherent in the development of the dose-response values used in our risk assessments for cancer effects from chronic exposures and noncancer effects from both chronic and acute exposures. Some uncertainties may be considered quantitatively, and others generally are expressed in qualitative terms. We note as a preface to this discussion a point on dose-response uncertainty that is brought out in the

EPA 2005 Cancer Guidelines;

namely, that “the primary goal of the EPA actions is protection of human health; accordingly, as an agency policy, risk assessment procedures, including default options that are used in the absence of scientific data to the contrary, should be health protective.” (

EPA 2005 Cancer Guidelines,

pages 1-7.) This is the approach followed here as summarized in the next several paragraphs. A complete detailed discussion of uncertainties and variability in dose-response relationships is given in the residual risk documentation, which is available in the docket for this action.

Cancer URE values used in our risk assessments are those that have been developed to generally provide an upper bound estimate of risk. That is, they represent a “plausible upper limit to the true value of a quantity” (although this is usually not a true statistical confidence limit).

In some circumstances, the true risk could be as low as zero; however, in other circumstances, the risk could also be greater.

When developing an upper bound estimate of risk and to provide risk values that do not underestimate risk, health-protective default approaches are generally used. To err on the side of ensuring adequate health-protection, the EPA typically uses the upper bound estimates rather than lower bound or central tendency estimates in our risk assessments, an approach that may have limitations for other uses (e.g., priority-setting or expected benefits analysis).

IRIS glossary (

http://www.epa.gov/NCEA/iris/help_gloss.htm

An exception to this is the URE for benzene, which is considered to cover a range of values, each end of which is considered to be equally plausible and which is based on maximum likelihood estimates.

Chronic noncancer reference (RfC and reference dose (RfD)) values represent chronic exposure levels that are intended to be health-protective levels. Specifically, these values provide an

estimate (with uncertainty spanning perhaps an order of magnitude) of daily oral exposure (RfD) or of a continuous inhalation exposure (RfC) to the human population (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. To derive values that are intended to be “without appreciable risk,” the methodology relies upon an uncertainty factor (UF) approach (U.S. EPA, 1993, 1994) which includes consideration of both uncertainty and variability. When there are gaps in the available information, UF are applied to derive reference values that are intended to protect against appreciable risk of deleterious effects. The UF are commonly default values,

e.g., factors of 10 or 3, used in the absence of compound-specific data; where data are available, UF may also be developed using compound-specific information. When data are limited, more assumptions are needed and more UF are used. Thus, there may be a greater tendency to overestimate risk in the sense that further study might support development of reference values that are higher (i.e., less potent) because fewer default assumptions are needed. However, for some pollutants, it is possible that risks may be underestimated. While collectively termed “uncertainty factor,” these factors account for a number of different quantitative considerations when using observed animal (usually rodent) or human toxicity data in the development of the RfC. The UF are intended to account for: (1) Variation in susceptibility among the members of the human population (i.e., inter-individual variability); (2) uncertainty in extrapolating from experimental animal data to humans (i.e., interspecies differences); (3) uncertainty in extrapolating from data obtained in a study with less-than-lifetime exposure (i.e., extrapolating from sub-chronic to chronic exposure); (4) uncertainty in extrapolating the observed data to obtain an estimate of the exposure associated with no adverse effects; and (5) uncertainty when the database is incomplete or there are problems with the applicability of available studies. Many of the UF used to account for variability and uncertainty in the development of acute reference values are quite similar to those developed for chronic durations, but more often they use individual UF values that may be less than 10. UF are applied based on chemical-specific or health effect-specific information (e.g., simple irritation effects do not vary appreciably between human individuals, hence a value of 3 is typically used), or based on the purpose for the reference value (see the following paragraph). The UF applied in acute reference value derivation include: (1) Heterogeneity among humans; (2) uncertainty in extrapolating from animals to humans; (3) uncertainty in lowest observed adverse effect (exposure) level to no observed adverse effect (exposure) level adjustments; and (4) uncertainty in accounting for an incomplete database on toxic effects of potential concern. Additional adjustments are often applied to account for uncertainty in extrapolation from observations at one exposure duration (e.g., 4 hours) to derive an acute reference value at another exposure duration (e.g., 1 hour).

According to the NRC report,

Science and Judgment in Risk Assessment

(NRC, 1994) “[Default] options are generic approaches, based on general scientific knowledge and policy judgment, that are applied to various elements of the risk assessment process when the correct scientific model is unknown or uncertain.” The 1983 NRC report,

Risk Assessment in the Federal Government: Managing the Process,

defined default option as “the option chosen on the basis of risk assessment policy that appears to be the best choice in the absence of data to the contrary” (NRC, 1983a, p. 63). Therefore, default options are not rules that bind the Agency; rather, the Agency may depart from them in evaluating the risks posed by a specific substance when it believes this to be appropriate. In keeping with EPA's goal of protecting public health and the environment, default assumptions are used to ensure that risk to chemicals is not underestimated (although defaults are not intended to overtly overestimate risk). See EPA, 2004,

An Examination of EPA Risk Assessment Principles and Practices,

EPA/100/B-04/001 available at:

http://www.epa.gov/osa/pdfs/ratf-final.pdf.

Not all acute reference values are developed for the same purpose, and care must be taken when interpreting the results of an acute assessment of human health effects relative to the reference value or values being exceeded. Where relevant to the estimated exposures, the lack of short-term dose-response values at different levels of severity should be factored into the risk characterization as potential uncertainties.

Although every effort is made to identify peer-reviewed reference values for cancer and noncancer effects for all pollutants emitted by the sources included in this assessment, some HAP continue to have no reference values for cancer or chronic noncancer or acute effects (see table 3.1-1 of the risk assessment document available in the docket for this proposed rulemaking). Since exposures to these pollutants cannot be included in a quantitative risk estimate, an understatement of risk for these pollutants at environmental exposure levels is possible. For a group of compounds that are either unspeciated or do not have reference values for every individual compound (e.g., POM), we conservatively use the most protective reference value to estimate risk from individual compounds in the group of compounds.

Additionally, chronic reference values for several of the compounds included in this assessment are currently under the EPA IRIS review, and revised assessments may determine that these pollutants are more or less potent than the current value. We may re-evaluate residual risks for the final rulemaking if these reviews are completed prior to our taking final action for this source category and a dose-response metric changes enough to indicate that the risk assessment supporting this notice may significantly understate human health risk. More information regarding the dose-response values used in this assessment is provided in the Draft Residual Risk Assessment for the Secondary Aluminum Production Source Category, which is available in the docket.

e. Uncertainties in the Multipathway and Environmental Effects Screening Assessment

We generally assume that when exposure levels are not anticipated to adversely affect human health, they also are not anticipated to adversely affect the environment. For each source category, we generally rely on the site-specific levels of PB-HAP emissions to determine whether a full assessment of the multipathway and environmental effects is necessary. Our screening methods use worst-case scenarios to determine whether multipathway impacts might be important. The results of such a process are biased high for the purpose of screening out potential impacts. Thus, when individual pollutants or facilities screen out, we are confident that the potential for multipathway impacts is negligible. On the other hand, when individual pollutants or facilities do not screen out, it does not mean that multipollutant impacts are significant, only that we cannot rule out that possibility. For this source category, we only performed a worst-case multipathway screening assessment for PB-HAP. Thus, it is important to note that potential PB-HAP multipathway risks are biased high.

B. How did we consider the risk results in making decisions for this proposal?

In evaluating and developing standards under section 112(f)(2), as discussed in Section I.A of this preamble, we apply a two-step process to address residual risk. In the first step, the EPA determines whether risks are acceptable. This determination

“considers all health information, including risk estimation uncertainty, and includes a presumptive limit on maximum individual lifetime [cancer] risk (MIR)

of approximately 1 in 10 thousand [i.e., 100 in 1 million]” (54 FR at 38045). In the second step of the process, the EPA sets the standard at a level that provides an ample margin of safety “in consideration of all health information, including the number of persons at risk levels higher than approximately one in one million, as well as other relevant factors, including costs and economic impacts, technological feasibility, and other factors relevant to each particular decision”

Id.

Although defined as “maximum individual risk,” MIR refers only to cancer risk. MIR, one metric for assessing cancer risk, is the estimated risk were an individual exposed to the maximum level of a pollutant for a lifetime.

In past residual risk actions, the EPA has presented and considered a number of human health risk metrics associated with emissions from the category under review, including: the MIR; the numbers of persons in various risk ranges; cancer incidence; the maximum non-cancer hazard index (HI); and the maximum acute non-cancer hazard (72 FR 25138, May 3, 2007; 71 FR 42724, July 27, 2006). In more recent proposals the EPA also presented and considered additional measures of health information, such as estimates of the risks associated with the maximum level of emissions which might be allowed by the current MACT standards (see, e.g., 76 FR 72770, November 25, 2011, 76 FR 72508, November 23, 2011, 75 FR 65068, October 21, 2010, and 75 FR 80220, December 21, 2010). The EPA also discussed and considered risk estimation uncertainties. The EPA is providing this same type of information in support of the proposed determinations described in this

Federal Register

notice.

The agency is considering all available health information to inform our determinations of risk acceptability and ample margin of safety under CAA section 112(f). Specifically, as explained in the Benzene NESHAP, “the first step judgment on acceptability cannot be reduced to any single factor” and thus “[t]he Administrator believes that the acceptability of risk under [previous] section 112 is best judged on the basis of a broad set of health risk measures and information” (54 FR at 38046). Similarly, with regard to making the ample margin of safety determination, as stated in the Benzene NESHAP “[in the ample margin decision, the agency again considers all of the health risk and other health information considered in the first step. Beyond that information, additional factors relating to the appropriate level of control will also be considered, including cost and economic impacts of controls, technological feasibility, uncertainties, and any other relevant factors.”

Id.

The agency acknowledges that the Benzene NESHAP provides flexibility regarding what factors the EPA might consider in making determinations and how these factors might be weighed for each source category. In responding to comment on our policy under the Benzene NESHAP, the EPA explained that: “The policy chosen by the Administrator permits consideration of multiple measures of health risk. Not only can the MIR figure be considered, but also incidence, the presence of non-cancer health effects, and the uncertainties of the risk estimates. In this way, the effect on the most exposed individuals can be reviewed as well as the impact on the general public. These factors can then be weighed in each individual case. This approach complies with the

Vinyl Chloride

mandate that the Administrator ascertain an acceptable level of risk to the public by employing [her] expertise to assess available data. It also complies with the Congressional intent behind the CAA, which did not exclude the use of any particular measure of public health risk from the EPA's consideration with respect to CAA section 112 regulations, and, thereby, implicitly permits consideration of any and all measures of health risk which the Administrator, in [her] judgment, believes are appropriate to determining what will `protect the public health' ” (54 FR at 38057).

For example, the level of the MIR is only one factor to be weighed in determining acceptability of risks. The Benzene NESHAP explained that “an MIR of approximately 1-in-10 thousand should ordinarily be the upper end of the range of acceptability. As risks increase above this benchmark, they become presumptively less acceptable under CAA section 112, and would be weighed with the other health risk measures and information in making an overall judgment on acceptability. Or, the agency may find, in a particular case, that a risk that includes MIR less than the presumptively acceptable level is unacceptable in the light of other health risk factors” (54 FR at 38045). Similarly, with regard to the ample margin of safety analysis, the EPA stated in the Benzene NESHAP that: “the EPA believes the relative weight of the many factors that can be considered in selecting an ample margin of safety can only be determined for each specific source category. This occurs mainly because technological and economic factors (along with the health-related factors) vary from source category to source category” (54 FR at 38061).

The EPA wishes to point out that certain health information has not been considered to date in making residual risk determinations. In assessing risks to populations in the vicinity of the facilities in each category, we present estimates of risk associated with HAP emissions from the source category alone (source category risk estimates) and HAP emissions from the entire facility at which the covered source category is located (facilitywide risk estimates). We do not attempt to characterize the risks associated with all HAP emissions impacting the populations living near the sources in these categories. That is, at this time, we do not attempt to quantify those HAP risks that may be associated with emissions from other facilities that do not include the source category in question, mobile source emissions, natural source emissions, persistent environmental pollution, or atmospheric transformation in the vicinity of the sources in these categories.

The agency understands the potential importance of considering an individual's total exposure to HAP in addition to considering exposure to HAP emissions from the source category and facility. This is particularly important when assessing non-cancer risks, where pollutant-specific exposure health reference levels (

e.g.,

Reference Concentrations (RfCs)) are based on the assumption that thresholds exist for adverse health effects. For example, the agency recognizes that, although exposures attributable to emissions from a source category or facility alone may not indicate the potential for increased risk of adverse non-cancer health effects in a population, the exposures resulting from emissions from the facility in combination with emissions from all of the other sources (

e.g.,

other facilities) to which an individual is exposed may be sufficient to result in increased risk of adverse non-cancer health effects. In May 2010, the Science Advisory Board (SAB) advised us “* * * that RTR assessments will be most useful to decision makers and communities if results are presented in the broader context of aggregate and cumulative risks, including background concentrations and contributions from other sources in the area.”

The EPA's responses to this and all other key recommendations of the SAB's advisory on RTR risk assessment methodologies (which is available at:

http://yosemite.epa.gov/sab/sabproduct.nsf/

4AB3966E263D943A8525771F00668381/$File/EPA-SAB-10-007-unsigned.pdf

) are outlined in a memo to this rulemaking docket from David Guinnup, UESPA/OAQPS entitled,

EPA's Actions in Response to the Key Recommendations of the SAB Review of RTR Risk Assessment Methodologies.

While we are interested in placing source category and facilitywide HAP risks in the context of total HAP risks from all sources combined in the vicinity of each source, we are concerned about the uncertainties of doing so. At this point, we believe that such estimates of total HAP risks will have significantly greater associated uncertainties than for the source category or facilitywide estimates hence compounding the uncertainty in any such comparison. This is because we have not conducted a detailed technical review of HAP emissions data for source categories and facilities that have not previously undergone an RTR review or are not currently undergoing such review. We are requesting comment on whether and how best to estimate and evaluate total HAP exposure in our assessments and, in particular, on whether and how it might be appropriate to use information from EPA's National Air Toxics Assessment (NATA) to support such estimates. We are also seeking comment on how best to consider various types and scales of risk estimates when making our acceptability and ample margin of safety determinations under CAA section 112(f).

C. How did we perform the technology review?

Our technology review focused on the identification and evaluation of developments in practices, processes, and control technologies that have occurred since the Secondary Aluminum Production NESHAP was promulgated. In cases where the technology review identified such developments, we conducted an analysis of the technical feasibility of applying these developments, along with the estimated impacts (costs, emissions reductions, risk reductions, etc.) of applying these developments. We then made decisions on whether it is appropriate or necessary to propose amendments to the 2000 NESHAP to require any of the identified developments.

Based on our analyses of the data and information collected from industry and the trade organization representing facilities subject to the NESHAP, our general understanding of the industry, and other available information in the literature on potential controls for this industry, we identified several new developments in practices, processes, and control technologies. For the purpose of this exercise, we considered any of the following to be a “development”:

• Any add-on control technology or other equipment that was not identified and considered during development of the 2000 Secondary Aluminum Production NESHAP.

• Any improvements in add-on control technology or other equipment (that were identified and considered during development of the 2000 Secondary Aluminum Production NESHAP) that could result in significant additional emissions reduction.

• Any work practice or operational procedure that was not identified or considered during development of the 2000 Secondary Aluminum Production NESHAP.

• Any process change or pollution prevention alternative that could be broadly applied to the industry and that was not identified or considered during development of the 2000 Secondary Aluminum Production NESHAP.

In addition to reviewing the practices, processes, or control technologies that were not considered at the time we developed the 2000 NESHAP, we reviewed a variety of data sources in our evaluation of whether there were additional practices, processes, or controls to consider for the Secondary Aluminum Production industry. Among the data sources we reviewed were the NESHAP for various industries that were promulgated after the 2000 NESHAP. We reviewed the regulatory requirements and/or technical analyses associated with these regulatory actions to identify any practices, processes, and control technologies considered in these efforts that could possibly be applied to emissions sources in the Secondary Aluminum Production source category, as well as the costs, non-air impacts, and energy implications associated with the use of these technologies.

Additionally, we requested information from facilities regarding developments in practices, processes, or control technology. Finally, we reviewed other information sources, such as State or local permitting agency databases and industry-supported databases. In particular, we consulted the EPA's RACT/BACT/LAER Clearinghouse (RBLC) to identify potential technology advances. Control technologies classified as RACT (Reasonably Available Control Technology), BACT (Best Available Control Technology), or LAER (Lowest Achievable Emissions Rate) apply to stationary sources depending on whether the sources are existing or new and on the size, age, and location of the facility. BACT and LAER (and sometimes RACT) are determined on a case-by-case basis, usually by State or local permitting agencies. The EPA established the RBLC to provide a central database of air pollution technology information (including technologies required in source-specific permits) to promote the sharing of information among permitting agencies and to aid in identifying future possible control technology options that might apply broadly to numerous sources within a category or apply only on a source-by-source basis. The RBLC contains over 5,000 air pollution control permit determinations that can help identify appropriate technologies to mitigate many air pollutant emissions streams. We searched this database to determine whether it contained any practices, processes or control technologies for the types of processes covered by the Secondary Aluminum Production NESHAP. No such practices, processes or control technologies were identified in this database.

D. What other issues are we addressing in this proposal?

In addition to the analyses described above, we also reviewed other aspects of the MACT standards for possible revision as appropriate and necessary. Based on this review we have identified aspects of the MACT standards that we believe need revision.

This includes proposing revisions to the startup, shutdown and malfunction (SSM) provisions of the MACT rule in order to ensure that they are consistent with the court decision in

Sierra Club

EPA,

551 F. 3d 1019 (D.C. Cir. 2008).

We are also proposing changes to the rule related to affirmative defense for violation of an emission limit during a malfunction. We are proposing other changes to address HF emissions, fugitive emissions during testing and numerous clarifications and corrections related to the existing provisions in the rule. Descriptions of each issue and the proposed revision to address the issue are presented in Section IV of this preamble.

IV. Analytical Results and Proposed Decisions

This section of the preamble provides the results of our RTR for the Secondary Aluminum Production source category and our proposed decisions concerning changes to the Secondary Aluminum Production NESHAP.

A. What are the results of the risk assessments?

For major sources in the Secondary Aluminum source category, we

conducted an inhalation risk assessment for all HAP emitted. In addition, we performed a facilitywide risk assessment for the major sources in the secondary aluminum source category. For area sources, we conducted an inhalation risk assessment for D/F since this is the only HAP covered by the subpart RRR MACT standards at area sources. For all sources, we conducted multipathway screening analyses for PB-HAP emitted (e.g., D/F). Although there are 53 major sources and 108 area sources covered by the subpart RRR MACT standards, 52 major sources and 103 area sources were modeled due to the other sources' lack of equipment subject to the applicable emission standards. Results of the risk assessment are presented briefly below and in more detail in the residual risk documentation referenced in Section III of this preamble, which is available in the docket for this action.

Table 4 of this preamble provides an overall summary of the results of the inhalation risk assessment.

Table 4—Secondary Aluminum Production Inhalation Risk Assessment Results

Category & number of facilities modeled

Maximum individual cancer risk

(in 1 million)

Based on actual emissions level

Based on allowable emissions level

Estimated population at increased risk of cancer ≥ 1 in 1 million

Estimated annual cancer incidence

(cases per year)

Maximum chronic non-cancer TOSHI

Based on actual emissions level

Based on allowable emissions level

Worst-case maximum refined screening acute non-cancer HQ

Major Source (52)

0.0006

0.05

REL

0.7 (HCl)

Area Source (103)

0.4

0.0006

0.0003

0.005

Facility-wide Major Source

62,000

0.006

0.4

Estimated maximum individual excess lifetime cancer risk due to HAP emissions from the source category. We did not have allowable emissions information at the facilitywide level, therefore, risk estimates based on facilitywide allowable emissions were not calculated.

Maximum TOSHI. The target organ with the highest TOSHI for the secondary aluminum source category is the respiratory system.

There is no acute dose-response value for dioxins, thus an acute HQ value for area sources was not calculated. See Section III.B of this preamble for explanations of acute dose-response values.

These estimates are based on actual emissions.

The results of the chronic inhalation cancer risk assessment for major sources indicate that the maximum lifetime individual cancer risk, considering actual emissions, could be up to 1 in 1 million, driven by dioxin emissions. The maximum cancer risks for this source category exceeded a cancer risk of 1 in 1 million at 1 of 52 facilities. The total estimated cancer incidence from this source category based on actual emission levels is 0.0006 excess cancer cases per year, or one excess case in every 1,666 years. No people were estimated to have cancer risks above 10 in a million and approximately 2 people were estimated to have cancer risks above 1 in 1 million considering all major source facilities in this source category. Based on MACT-allowable emissions for the major sources in this category, the MIR could be up to 20 in 1 million.

With respect to chronic inhalation noncancer risk from major sources, we estimate a maximum TOSHI value of 0.05 for the Secondary Aluminum source category, primarily from hydrochloric acid from Group 1 furnaces. Considering MACT-allowable emissions, this maximum TOSHI value is estimated to be 1. Moreover, our worst-case highest acute screening value for major sources was 0.7 based on the REL for HCL.

Considering facility wide emissions at the 52 major sources, the MIR is estimated to be up to 20 in 1 million, the estimated annual incidence is 0.006 cases per year, and the chronic non-cancer TOSHI value is calculated to be 0.4.

In addition, we estimated risks associated with dioxin emissions at the 103 area sources in the Secondary Aluminum Production source category. The results of the chronic inhalation cancer risk assessment indicate that the maximum lifetime individual cancer risk could be up to 0.4 in 1 million and an estimated annual incidence of 0.0006 cases per year. Considering MACT-allowable emissions, the MIR could be up to 6 in 1 million. With respect to chronic inhalation noncancer risk from D/F emissions at area sources, we estimate a maximum TOSHI value of 0.0003. Considering MACT-allowable emissions, this maximum TOSHI value is estimated to be 0.005 for area sources.

In addition to the analyses presented above, to screen for potential multipathway effects from emissions of PB-HAP (such as cadmium, dioxins and PAHs) we compared actual emission rates from major source facilities in this source category to the screening values for these PB HAP described above (see Section III(A)(4)). For dioxins, we also screened for potential multipathway effects from emissions of D/F from area sources by comparing the estimated actual emission rates from these area sources to the screening value for D/F described above. (see Risk Assessment Document Appendix 4 for a more detailed discussion of screening emission rates). Results of this worst-case screen estimate that actual POM emissions from 10 of the 52 major source facilities exceed the POM screening emission rate. With respect to D/F, of the 46 major sources that emitted dioxins, 39 exceeded our screening emission rate. Similarly, 76 out of 103 area sources exceeded our D/F screening rate. These exceedances of the worst-case multipathway screening level for POM and dioxins indicate that there may be potential multipathway impacts of concern due to emissions of POM and dioxins. In general, emission rates below the worst-case multipathway screening level indicate no significant potential for multipathway-related health or environmental effects; whereas emission levels above this worst-case screening level only indicate the potential for multipathway-related health or environmental risks of concern based on a worst-case scenario. Thus, we note that these screening values are biased high for purposes of screening and are subject to significant uncertainties. As such, they do not represent refined estimates of risk and thus, do not necessarily indicate that potential multipathway risks from the source category may be a concern; we can only say that we cannot rule them out.

With respect to the potential for adverse environmental effects from non PB-HAP, we note that for both major

and area sources all chronic non-cancer HQ values for all pollutants considering actual emissions are well below 1 using human health reference values. Thus, we believe that it is unlikely that adverse environmental effects would occur at the actual HAP concentrations estimated in our human health risk assessment.

B. What are our proposed decisions regarding risk acceptability and ample margin of safety?

1. Risk Acceptability

As noted in Section III.C of this preamble, we weigh all health risk factors in our risk acceptability determination, including the MIR, the numbers of persons in various risk ranges, cancer incidence, the maximum noncancer HI, the maximum acute noncancer hazard, the extent of noncancer risks, the potential for adverse environmental effects, distribution of risks in the exposed population, and risk estimation uncertainties (54 FR 38044, September 14, 1989).

For the Secondary Aluminum Production source category, the risk analysis indicates that the cancer risks to the individual most exposed could be up to 1 in 1 million due to actual emissions and up to 20 in 1 million due to MACT-allowable emissions. These risks are considerably less than 100 in 1 million, which is the presumptive upper limit of acceptable risk. The risk analysis also shows very low cancer incidence (0.0006 cases per year), as well as no potential for adverse chronic or acute non-cancer health effects. In addition, the risk assessment indicates no significant potential for adverse environmental effects.

In addition to the analyses presented above, to screen for potential multipathway effects from emissions of D/F and POM, we compared the estimated actual emission rates from facilities in this source category to the multipathway screening levels described in section III.B. With respect to POM and dioxins, both major and area sources in the category exceeded our worst-case screening levels. However, we note that this is a worst-case conservative screening level analysis, therefore these results are biased high for purposes of screening and are subject to significant uncertainties. Moreover, we note that due to data limitations we were unable to further refine this worst-case screening scenario. As such, they do not necessarily indicate that significant multipathway risks actually exist at secondary aluminum facilities, only that we cannot rule them out as a possibility. With regard to facilitywide multipathway risk, based on the low level of risk identified for the source category, a facilitywide multipathway risk analysis was not conducted for this source category.

Considering all of the health risk information and factors discussed above, including the uncertainties discussed in section IV.A.7 of this preamble, we propose that the risks from the Secondary Aluminum Production source category are acceptable.

2. Ample Margin of Safety Analysis

We next considered whether the existing MACT standard provides an ample margin of safety to protect public health. Under the ample margin of safety analysis, we evaluated the cost and feasibility of available control technologies and other measures (including the controls, measures and costs reviewed under the technology review) that could be applied in this source category to further reduce the risks (or potential risks) due to emissions of HAP identified in our risk assessment, along with all of the health risks and other health information considered in the risk acceptability determination described above. In this analysis we considered the results of the technology review, risk assessment and other aspects of our MACT rule review to determine whether there are any cost-effective controls or other measures that would reduce emissions further to provide an ample margin of safety with respect to the risks associated with these emissions.

For POM, THC and metal HAP emissions, our risk analysis indicated very low potential for risk from the facilities in the source category. Our technology review did not identify any new practices, controls or process options that are being used in this industry or in other industries that would be cost-effective for further reduction of these emissions. Based on the estimated low risk levels and absence of new practices or control options, we conclude that the provisions of the current MACT provide for an ample margin of safety for public health with respect to emissions of POM, THC and metal HAP.

Our multipathway screening analysis results indicated exceedances of the worst-case screening levels which do not necessarily indicate any risks, however, they do suggest a potential for risks that cannot be ruled out. To evaluate the potential to reduce D/F emissions to ensure an ample margin of safety, our analysis for D/F focused on two options: (1) Lowering the existing D/F limit from 15 to 10 μg TEQ/Mg feed for Group 1 furnaces processing other than clean charge at all facilities; and (2) lowering the existing D/F limit for Group 1 furnaces processing other than clean charge, after applying a subcategorization based on facility production capacity. The lower D/F limits potentially could be met by using an activated carbon injection (ACI) system. With regard to the option of lowering the emission limit to 10 μg TEQ/Mg feed for Group 1 furnaces handling other than clean charge, we estimate that about 11 facilities would need to reduce their D/F emissions and that the costs would be about $5.9 million in total capital costs with total annualized costs of about $2.7 million. This option would achieve an estimated 1.66 grams TEQ reduction of D/F emissions with an overall cost-effectiveness of about $1.61 million per gram D/F TEQ. The second option of lowering the emission limit based on a subcategorization according to facility production capacity yielded cost-effectiveness estimates of greater than $1 million per gram D/F TEQ reduced. Furthermore, our analysis indicates that these options would not result in significant emissions reductions and would not, therefore, result in significant changes to the potential risk levels. After considering the costs and the small reductions that would be achieved, we have decided not to propose any of these options. For more information, please refer to the Draft Technical Document for the Secondary Aluminum Production Source Category that is available in the public docket for this proposed rulemaking.

We also evaluated possible options based on work practices to achieve further emissions reductions. The current subpart RRR NESHAP includes work practices to minimize D/F emissions which include scrap inspection, limitations on materials processed by group 2 furnaces, temperature and residence time requirements for afterburners controlling sweat furnaces, labeling requirements, capture/collection requirements, and requirements for an operations, maintenance and monitoring plan that contains details on the proper operation and maintenance of processes and control equipment. We searched for and evaluated other possible work practices such as good combustion practices, better scrap inspection and cleaning, and process monitoring. However, none of these potential work practices were determined to be feasible and effective in reducing D/F emissions

for this source category. Thus, we did not identify any feasible or applicable work practices for this industry beyond those that are currently in the MACT rule. Further detail on work practices and control options are provided in the Draft Technology Review for the Secondary Aluminum Production Source Category, which is available in the docket.

In accordance with the approach established in the Benzene NESHAP, we weighed all health risk information and factors considered in the risk acceptability determination, including uncertainties, along with the cost and feasibility of control technologies and other measures that could be applied in this source category, in making our ample margin of safety determination. In summary, we did not identify any cost-effective approaches to further reduce POM, THC, metal HAP or D/F emissions beyond the reductions that are already being achieved by the current NESHAP. Further, our analysis indicates that none of the options considered would result in significant emissions reductions and would not, therefore, result in significant changes to the potential risk levels.

Because of the high cost associated with the use of activated carbon injection systems and because work practices are already required to help ensure low emissions, we propose that the existing MACT standards provide an ample margin of safety to protect public health and prevent an adverse environmental effect.

C. What are the results and proposed decisions based on our technology review?

As described above, the typical controls used to minimize emissions at secondary aluminum facilities include fabric filters for control of PM from aluminum scrap shredders; afterburners for control of THC and D/F from thermal chip dryers; afterburners plus lime-injected fabric filters for control of PM, HCl, THC, and D/F from scrap dryers/delacquering kilns/decoating kilns; afterburners for control of D/F from sweat furnaces; fabric filters for control of PM from dross-only furnaces and rotary dross coolers; lime-injected fabric filters for control of PM and HCl from in-line fluxers; and lime-injected fabric filters for control of PM, HCl and D/F from group 1 furnaces. There have been some developments in practices, processes, or control technologies that have been implemented in this source category since promulgation of the current NESHAP. However, based on information available to the EPA, these technologies do not clearly reduce HAP emissions relative to technologies that were considered by the EPA when promulgating the Secondary Aluminum Production NESHAP in 2000. In addition, we evaluated whether lime-injection fabric filters with activated carbon injection could be used to further reduce D/F from group 1 furnaces in a cost-effective manner.

At least one company supplies multichamber furnaces that combine the functions of a delacquering kiln and a melting furnace. At least 16 of these furnaces are in operation in Europe, Asia and the Middle East, however emission test data for these facilities is not available. One furnace of this type is presently operating in the U.S. and is permitted as a group 1 furnace handling other than clean charge.

However, the limited D/F emission test data available for the one operating U.S. multichamber furnace is within the range of test data for Group 1 furnaces and delacquering kilns that are in compliance with subpart RRR using control technologies considered by the EPA in the subpart RRR NESHAP. Based on available information it is not clear that this technology would reduce HAP emissions relative to technologies that were considered by the EPA in promulgating the subpart RRR NESHAP and are already used by other facilities. Based on our analysis, we conclude that it would not be appropriate at this time to revise subpart RRR standards based on use of this technology.

Eddy current separators are used to separate a concentrated aluminum fraction from a heterogeneous scrap feed. These units operate at ambient temperature and emit no D/F or other gaseous pollutants. They are used on the material output from mechanical shredders that shred automobiles and appliances (not on the scrap shredders used in the secondary aluminum industry). These units can potentially decrease the need for sweat furnaces. However, the product of eddy current separators is not clean charge, as with a sweat furnace. Therefore, the product of eddy current separators must undergo further processing to produce clean charge, and it is not possible to directly compare eddy current separators with sweat furnaces.

Catalytic filtration systems, including catalytic filter bags, are available to reduce D/F emissions. These bags incorporate an expanded polytetrafluoroethylene membrane coated with a precious metal catalyst which promotes the oxidation of D/F. The manufacturer claims that this system is installed in over 100 applications around the world, including at least 1 secondary aluminum processing plant. However, no respondents to our all-company ICR reported using this technology and we have no data on the D/F emission levels that can be achieved at secondary aluminum production facilities using this technology. Therefore we cannot conclude that they are more effective at reducing D/F emissions than the control technologies considered by the EPA in the 2000 subpart RRR NESHAP. We therefore conclude, based on information available to the EPA, that catalytic filtration systems are not at present a demonstrated control technology that should be used as the technical basis to require more stringent emission limits for the secondary aluminum production source category.

We also evaluated the potential to lower D/F emissions under the technology review by lowering the emissions limits based on the broader use of activated carbon injection technology. Under this analysis, we evaluated the same approach that was evaluated under the ample margin of safety analysis described in section IV.B. In summary, we evaluated two main options, as follows: (1) Lower the existing D/F limit from 15 to 10 μg TEQ/Mg feed for Group 1 furnaces processing other than clean charge at all facilities; and (2) lower the existing D/F limit for Group 1 furnaces processing other than clean charge, after applying a subcategorization based on facility production capacity. The lower D/F emissions limits potentially could be met by using an activated carbon injection (ACI) system. With regard to the option of lowering the emission limit to 10 μg TEQ/Mg feed for Group 1 furnaces handling other than clean charge, we estimate that about 11 facilities would need to reduce their D/F emissions and that the costs would be about $5.9 million in total capital costs with total annualized costs of about $2.7 million. This option would achieve an estimated 1.66 grams TEQ reduction of D/F emissions with an overall cost-effectiveness of about $1.61 million per gram D/F TEQ. The second option of lowering the emission limit based on a subcategorization according to facility production capacity yielded cost-effectiveness estimates of greater than $1 million per gram D/F TEQ reduced. Furthermore, our analysis indicates that these options would not result in significant emissions reductions. After considering the compliance costs and the small associated emission reductions that would be achieved, we are not proposing revised subpart RRR standards based on either of these options that rely on the use of ACI

injection technology under section 112(d)(6) of the CAA.

Overall, based on our review of developments in practices, processes, and control technologies, we have not identified any control approaches that clearly reduce HAP emissions in a cost-effective manner relative to technologies that were available and considered by the EPA at the time of promulgation of the Secondary Aluminum Production NESHAP in 2000. Therefore, we are not proposing any revisions to the NESHAP as a result of our technology review. Additional details regarding these analyses can be found in the following technical document for this action which is available in the docket:

Draft Technology Review for the Secondary Aluminum Production Source Category.

D. What other actions are we proposing?

This section discusses revisions that are being proposed to correct and clarify provisions in the rule as well as solicitations of comments and requests for additional information. We are proposing revisions to the rule to address SSM provisions within the rule that were vacated by a court ruling and we are adding a requirement for electronic submission of all test results to increase the ease and efficiency of data submittal and improve data accessibility. In addition, since promulgation of the subpart RRR NESHAP in March 2000 (65 FR 15689), we have received recommendations and suggestions from individual representatives from state regulatory agencies and industry, as well as within EPA, to correct errors in the rule and to help clarify the intent and implementation of the rule. Table 5 provides a summary of these proposed changes. Following Table 5 are detailed descriptions of the proposed revisions.

Table 5—Summary of Technical Corrections/Clarifications to the Secondary Aluminum Production NESHAP

Correction/Clarification

Description

1. Startup, shutdown and malfunctions (63.1503, 63.1506(l) and (m), 63.1506(q),and 63.1520)

• Addresses vacated General Provision (GP) requirements.

• Deletes references to vacated GP sections.

• Requires all sources to comply with emission limits including during periods of startup and shutdown.

• Adds definition for affirmative defense. Adds affirmative defense provisions for malfunctions.

2. Electronic Reporting (63.1516(b)(3))

• Requires owners and operators to report performance test results through the EPA Electronic Reporting System (ERT).

3. ACGIH Guidelines

• The capture and collection provision of § 63.1506(c)(1) that reference the ”Industrial Ventilation: A Manual of Recommended Practice”, is revised to allow 23rd or 27th Editions and take out specific references to chapters 3 and 5.

• Requests comments on methods other than ACGIH Guidelines to ensure capture and collection and alternatives to the currently required hooding requirements.

4. Scrap Inspection Program for Group 1 Furnace without Add-on Air Pollutions Control Devices (63.1510(p))

• Considering improvements to scrap inspection program.

• Requesting comments and information.

5. Multiple Tests for Worst Case Scenarios (63.1511(b)(6))

• Clarifies that multiple tests may be required to reflect the range of emissions likely for each regulated pollutant.

6. Lime Injection Rate Verification (63.1510(i)(4))

• Requires verification of the lime mass injection rate at least once per month.

7. Flux Monitoring (63.1510(j)(4))

• Clarifies that solid flux must be tracked at each addition during the cycle or time period used in the performance test.

8. Cover fluxes (63.1503)

• Clarifies definition of cover flux.

9. Capture and Collection Systems (63.1503)

• Adds a definition of capture and collection systems.

10. Bale Breakers (63.1503)

• Adds a definition of a bale breaker to clarify that a bale breaker is not a scrap shredder.

11. Bag Leak Detection Systems (BLDS) (63.1510(f)(1)(ii))

• Removes reference to an outdated guidance document and requires use of manufacturer's maintenance and operating instructions.

12. Sidewell Furnaces (63.1510(n)(1))

• Requires visual inspection after each tap rather than after each charge.

• Allows other means of measuring molten metal level.

13. Testing Representative Units (63.1511(f)(6))

• Clarifies that all performance test runs must be conducted on the same affected source or emission unit.

14. Inital Performance Tests (63.1511(b))

• Revises performance test requirements to allow 180 days to conduct initial performance test consistent with GP.

15. Definition of Scrap Dryer/Delacquering Kiln/Decoating Kiln and Scrap Shredder (63.1503)

• Clarifies definition of Scrap Dryer/Delacquering/Decoating Kiln to include delamination of aluminum from paper or plastic.

• Clarifies definition of scrap shredder to include granulation and shearing.

16. Transporting metal (63.1503)

• Clarifies definition of Group 2 furnace to exclude pots used to transport metal.

17. Specifications for Cleaning Processes

• Not proposing cleaning specifications at this time.

• Invites comments and solicits information on appropriate cleaning procedures.

18. HF Emissions Compliance Provisions (63.1503, 63.1505, 63.1511(c)(9), 63.1513)

• Adds definition of HF.

• Adds emissions standard for HF.

• Requires EPA Method 26A for measurement of HF.

19. Uncontrolled furnaces that do not Comply with ACGIH Hooding Guidelines (63.1512(e)(4))

• Requires owner/operators with uncontrolled group 1 furnaces to construct hoods for performance testing to demonstrate compliance, or assume 67 percent capture efficiency if hooding does not meet ACGIH guidelines.

• Seeks comments on alternative approaches.

20. Clarify the possible Number of SAPUs (63.1503)

• Revises “SAPU” definition to clarify there can be more than 1 new SAPU.

21. Aluminum Scrap Containing Anodizing Dyes or Sealants (63.1503)

• Clarifies “clean charge” definition to exclude anodized material that contains dyes or sealants that contain organic material.

22. Afterburner Residence Time (63.1503)

• Clarifies “residence time” definition to include refractory lined ductwork up to the control thermocouple.

23. SAPU Feed/Charge Rate (63.1505(k))

• Clarifies that daily throughput must be used to calculate allowable emissions within the SAPU.

24. Changing Furnace Classifications (§ 63.1514)

• Allows owners/operators to change furnace classifications.

• Specifies requirements for changing.

25. Dross Only Versus Dross/Scrap Furnaces

• Clarifies that owners/operators have the option to conduct performance tests under different operating conditions to address charge/flux changes.

26. Annual Hood Inspections (63.1510(d)(2))

• Clarifies that annual hood inspections include flow rate measurements.

27. Applicability of Rule to Area Sources (63.1506(a), 63.1510(a))

• Clarifies which operating, monitoring and other standards apply to area sources.

28. Altering Parameters during Testing with New Scrap Streams (63.1511(b)(1))

• Clarifies that owners/operators can deviate from established parametric limits during performance testing being done to establish new parametric limits.

29. Controlled Furnaces that are Temporarily Idled (63.1506(q)(5))

• Allows control device for furnaces to be shut down if furnace will remain idle for 24 hours or longer.

30. Annual Compliance Certification for Area Sources (63.1516(c))

• Clarifies that area sources must submit an annual compliance certification.

1. Startup, Shutdown and Malfunctions

The United States Court of Appeals for the District of Columbia Circuit vacated portions of two provisions in the EPA's CAA Section 112 regulations governing the emissions of HAP during periods of startup, shutdown and malfunction (SSM).

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551 F.3d 1019 (D.C. Cir. 2008). Specifically, the Court vacated the SSM exemption contained in 40 CFR 63.6(f)(1) and 40 CFR 63.6(h)(1), that are part of a regulation, commonly referred to as the “General Provisions Rule,” that the EPA promulgated under CAA section 112. When incorporated into CAA Section 112(d) regulations for specific source categories, these two provisions exempt sources from the requirement to comply with the otherwise applicable CAA section 112(d) emission standard during periods of SSM.

We are proposing the elimination of the SSM exemption in this rule. Consistent with

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the EPA is proposing standards in this rule that apply at all times. We are also proposing several revisions to Appendix A to subpart RRR of part 63 (the General Provisions Applicability table). For example, we are proposing to eliminate the incorporation of the General Provisions' requirement that the source develop an SSM plan. We also are proposing to eliminate or revise certain recordkeeping and reporting requirements related to the SSM exemption. The EPA has attempted to ensure that we have not included in the proposed regulatory language any provisions that are inappropriate, unnecessary, or redundant in the absence of the SSM exemption. We are specifically seeking comment on whether there are any such provisions that we have inadvertently incorporated or overlooked.

In proposing standards in this rule, the EPA has taken into account startup and shutdown periods and is proposing standards for startup and shutdown periods for all process units.

We are proposing that the subpart RRR standards apply at all times, including periods of startup and shutdown. Because the scrap processed at secondary aluminum production facilities is the source of emissions, we expect that emissions during startup and shutdown would be no higher and probably much lower than emissions during normal operations since no scrap would be processed. We know of no reason why the existing standards should not apply at all times. For production processes in the secondary aluminum production source category where the standards are expressed in units of pounds per ton of feed or similar units (i.e. thermal chip dyers, scrap dryer/delacquering kiln/decoating kilns, dross-only furnaces, in-line

fluxers using reactive flux, and group 1 furnaces), we are proposing certain methods for demonstrating compliance with those limits, as discussed further in the

Technical Document for the Secondary Aluminum Production Source Category

that is available in the docket for this proposed rulemaking.

We solicit comment on the proposed standards during startup and shutdown periods. Specifically, for those processes that have production-based limits (i.e., thermal chip dyers, scrap dryer/delacquering kiln/decoating kilns, dross-only furnaces, in-line fluxers using reactive flux, and group 1 furnaces), we solicit comment as to whether work practices under section 112(h) of the CAA should be applied during startup and shutdown. If you believe work practices would be appropriate for such processes, please explain how the requirements of section 112(h)(2) are met and identify any work practices that would be effective in limiting HAP emissions during periods of startup and shutdown for such processes.

For these processes (thermal chip dryers, scrap dryers/delacquering kilns/decoating kilns, dross-only furnaces, group 1 furnaces, in-line fluxers, dross only furnaces, sweat furnaces, and group 2 furnaces), startup begins with ignition and equipment warming from a cold start or a complete shutdown, using natural gas or other clean fuel. At the point that feed is introduced, startup ends and the process is in normal operation. Similarly for shutdown periods, when an operator halts the introduction of feed or charge to, and has removed all product (e.g., tapped a furnace), the shutdown phase has begun. For more information about the application of subpart RRR standards to periods of Startup and shutdown, including revised methods to demonstrate compliance, see the

Technical Support Document for the Secondary Aluminum Production

Source Category that is available in the docket for this proposed rulemaking.

Periods of startup, normal operations, and shutdown are all predictable and routine aspects of a source's operation. However, by contrast, malfunction is defined as a “sudden, infrequent, and not reasonably preventable failure of air pollution control and monitoring equipment, process equipment or a process to operate in a normal or usual manner * * *” (40 CFR 63.2). The EPA has determined that CAA section 112 does not require that emissions that occur during periods of malfunction be factored into development of CAA section 112 standards. Under section 112, emissions standards for new sources must be no less stringent than the level “achieved” by the best controlled similar source and for existing sources generally must be no less stringent than the average emission limitation “achieved” by the best performing 12 percent of sources in the category. There is nothing in section 112 that directs the agency to consider malfunctions in determining the level “achieved” by the best performing or best controlled sources when setting emission standards. Moreover, while the EPA accounts for variability in setting emission standards consistent with the section 112 case law, nothing in that case law requires the agency to consider malfunctions as part of that analysis. Section 112 of the CAA uses the concept of “best controlled” and “best performing” unit in defining the level of stringency that CAA section 112 performance standards must meet. Applying the concept of “best controlled” or “best performing” to a unit that is malfunctioning presents significant difficulties, as malfunctions are sudden and unexpected events.

Further, accounting for malfunctions would be difficult, if not impossible, given the myriad different types of malfunctions that can occur across all sources in the category and given the difficulties associated with predicting or accounting for the frequency, degree and duration of various malfunctions that might occur. As such, the performance of units that are malfunctioning is not “reasonably” foreseeable. See, e.g.,

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167 F. 3d 658, 662 (D.C. Cir. 1999) (The EPA typically has wide latitude in determining the extent of data-gathering necessary to solve a problem. We generally defer to an agency's decision to proceed on the basis of imperfect scientific information, rather than to “invest the resources to conduct the perfect study.”).