Document ID: EPA-HQ-OAR-2005-0475-0001
Agency: epa
Document Type: Proposed Rule
Title: National Emission Standards for Hazardous Air Pollutants for Organic Hazardous Air Pollutants From the Synthetic Organic Chemical Manufacturing Industry
Posted Date: 2006-06-14T11:38:54Z

[Federal Register: June 14, 2006 (Volume 71, Number 114)]
[Proposed Rules]               
[Page 34421-34446]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr14jn06-29]                         

[[Page 34421]]

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Part II

Environmental Protection Agency

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40 CFR Part 63

National Emission Standards for Hazardous Air Pollutants for Organic 
Hazardous Air Pollutants From the Synthetic Organic Chemical 
Manufacturing Industry; Proposed Rule

[[Page 34422]]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 63

[EPA-HQ-OAR-2005-0475; FRL-8181-3]
RIN 2060-AK14

 
National Emission Standards for Hazardous Air Pollutants for 
Organic Hazardous Air Pollutants From the Synthetic Organic Chemical 
Manufacturing Industry

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule; amendments.

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SUMMARY: In 1994, EPA promulgated National Emission Standards for 
Hazardous Air Pollutants (NESHAP) for the synthetic organic chemical 
manufacturing industry (SOCMI). This rule is commonly known as the 
hazardous organic NESHAP (HON) and established maximum achievable 
control technology (MACT) standards to regulate the emissions of 
organic hazardous air pollutants (HAP) from production processes that 
are located at major sources.
    The Clean Air Act (CAA) directs EPA to assess the risk remaining 
(residual risk) after the application of the MACT standards and to 
promulgate additional standards if required to provide an ample margin 
of safety to protect public health or prevent adverse environmental 
effect. The CAA also requires us to review and revise MACT standards, 
as necessary, every eight years, taking into account developments in 
practices, processes, and control technologies that have occurred 
during that time.
    Based on our findings from the residual risk and technology review, 
we are proposing two options (to be considered with equal weight) for 
emissions standards for new and existing SOCMI process units. The first 
proposed option would impose no further controls, proposing to find 
that the existing standards protect public health with an ample margin 
of safety and prevent adverse environmental impacts, as required by 
section 112(f)(2) of the CAA and would satisfy the requirements of 
section 112(d)(6). The second proposed option would provide further 
reductions of organic HAP at certain process units by applying 
additional controls for equipment leaks and by controlling some storage 
vessels and process vents that are uncontrolled under the current rule. 
This option would also protect public health with an ample margin of 
safety and prevent adverse environmental impacts, as required by 
section 112(f)(2) of the CAA and would satisfy the requirements of 
section 112(d)(6). Under this option, we are proposing that the 
compliance deadlines for additional promulgated requirements would be 
one to three years from the date of promulgation.

DATES: Comments. Written comments must be received on or before August 
14, 2006.
    Public Hearing. If anyone contacts EPA by July 5, 2006 requesting 
to speak at a public hearing, a public hearing will be held on July 14, 
2006.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2005-0475, by one of the following methods:
     Federal eRulemaking Portal: http://www.regulations.gov. 

Follow the on-line instructions for submitting comments.
     E-mail: a-and-r-docket@epa.gov.
     Fax: (202) 566-1741.
     Hand Delivery: Air and Radiation Docket, Environmental 
Protection Agency, 1301 Constitution Avenue, NW., Room B-108, 
Washington, DC 20014. Such deliveries are accepted only during the 
Docket's normal hours of operation and special arrangements should be 
made for deliveries of boxed information.
     Mail: EPA Docket Center (EPA/DC), Environmental Protection 
Agency, Mailcode 6102T, 1200 Pennsylvania Avenue, NW., Washington, DC 
20460.
    Please include a total of two copies. We request that a separate 
copy also be sent to the contact person identified below (see FOR 
FURTHER INFORMATION CONTACT).
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2005-0475. EPA's policy is that all comments received will be included 
in the public docket without change and may be made available online 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 e-mail. The http://www.regulations.gov Web site is an ``anonymous 

access'' system, which means EPA will not know your identity or contact 
information unless you provide it in the body of your comment. If you 
send an e-mail comment directly to EPA without going through http://www.regulations.gov
, your e-mail address will be automatically captured 

and included as part of the comment that is placed in the public docket 
and made available on the Internet. If you submit an electronic 
comment, EPA recommends that you include your name and other contact 
information in the body of your comment with a disk or CD-ROM you 
submit. If EPA cannot read your comment due to technical difficulties 
and cannot contact you for clarification, EPA may not be able to 
consider your comment. Electronic files should avoid the use of special 
characters, any form of encryption, and be free of any defects or 
viruses.
    Docket: All documents in the docket are listed in the 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, 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 Air and Radiation 

Docket, EPA/DC, EPA West, Room B102, 1301 Constitution Ave., NW., 
Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4:30 
p.m., Monday through Friday, excluding legal holidays. The telephone 
number for the Public Reading Room is (202) 566-1744, and the telephone 
number for the Air and Radiation Docket is (202) 566-1742.
    Public Hearing: If a public hearing is held, it will be held at 10 
a.m. at the Environmental Research Center Auditorium, Research Triangle 
Park, NC, or at an alternate site nearby.

FOR FURTHER INFORMATION CONTACT: For questions about the proposed rule, 
contact Mr. Randy McDonald, EPA, Office of Air Quality Planning and 
Standards, Sector Policies and Programs Division, Coatings and 
Chemicals Group (E143-01), Research Triangle Park, NC 27711; telephone 
number (919) 541-5402; fax number (919) 541-0246; e-mail address: 
mcdonald.randy@epa.gov. For questions on the residual risk analysis, 

contact Mr. Mark Morris, EPA, Office of Air Quality Planning and 
Standards, Health and Environmental Impacts Division, Sector Based 
Assessment Group (C404-01), Research Triangle Park, NC 27711; telephone 
number (919) 541-5416; fax number (919) 541-0840; e-mail address: 
morris.mark@epa.gov.

SUPPLEMENTARY INFORMATION: Regulated Entities. Categories and entities 
potentially regulated by the proposed rule are SOCMI facilities that 
are major sources of HAP emissions. The proposed rule would affect the 
following categories of sources:

[[Page 34423]]

------------------------------------------------------------------------
                                      NAICS \1\   Example of potentially
              Category                   code       regulated entities
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Industry............................        325  Chemical manufacturing
                                                  facilities.
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\1\ North American Industrial Classification Code.

    This table is not intended to be exhaustive, but rather provides a 
guide for readers regarding entities likely to be regulated by the 
proposed rule. To determine whether your facility would be regulated by 
the proposed rule, you should carefully examine the applicability 
criteria in 40 CFR 63.100 of the rule. If you have any questions 
regarding the applicability of the proposed rule to a particular 
entity, contact the person listed in the preceding FOR FURTHER 
INFORMATION CONTACT section.
    Submitting CBI. Do not submit this information to EPA through 
http://www.regulations.gov or e-mail. 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 EPA, mark the outside of the disk or CD-ROM 
as CBI and then identify electronically within the disk or CD-ROM the 
specific information that is claimed as CBI. In addition to one 
complete version of the comment that includes information claimed as 
CBI, a copy of the comment that does not contain the information 
claimed as CBI must be submitted for inclusion in the public docket. 
Information so marked will not be disclosed except in accordance with 
procedures set forth in 40 CFR part 2.
    Public Hearing. Persons interested in presenting oral testimony or 
inquiring as to whether a hearing is to be held should contact Randy 
McDonald, Coatings and Chemicals Group, Sector Policies and Programs 
Division (Mail Code C504-04), U.S. EPA, Research Triangle Park, North 
Carolina, 27711, telephone number (919) 541-5402, electronic mail 
address mcdonald.randy@epa.gov, at least two days in advance of the 
potential date of the public hearing. Persons interested in attending 
the public hearing also must call Mr. Randy McDonald to verify the 
time, date, and location of the hearing. A public hearing will provide 
interested parties the opportunity to present data, views, or arguments 
concerning the proposed amendments.
    World Wide Web (WWW). In addition to being available in the docket, 
an electronic copy of the proposed rule is also available on the WWW 
through the Technology Transfer Network Web site (TTN Web). Following 
signature, a copy of the proposed rule will be posted on the TTN's 
policy and guidance page for newly proposed or promulgated rules at 
http://www.epa.gov/ttn/oarpg. The TTN provides information and 

technology exchange in various areas of air pollution control.
    Organization of this Document. The information presented in this 
preamble is organized as follows:

I. Background
    A. What is the statutory authority for regulating hazardous air 
pollutants?
    B. What are SOCMI facilities?
    C. What are the health effects of HAP emitted from SOCMI 
facilities?
    D. What does the HON require?
II. Summary of Proposed Revised Standards
III. Rationale for the Proposed Rule
    A. What is our approach for developing residual risk standards?
    B. How did we estimate residual risk?
    C. What are the residual risks from HON CMPUs?
    D. What is our proposed decision on acceptable risk?
    E. What is our proposed decision on ample margin of safety?
    F. What is EPA proposing pursuant to CAA section 112(d)(6)?
IV. Solicitation of Public Comments
    A. Introduction and General Solicitation
    B. Specific Comment and Data Solicitations
V. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination with 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From 
Environmental Health and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer Advancement Act
    J. Executive Order 12898: Federal Actions to Address 
Environmental Justice in Minority Populations and Low-Income 
Populations

I. Background

A. What is the statutory authority for regulating hazardous air 
pollutants?

    Section 112 of the CAA establishes a two-stage regulatory process 
to address emissions of HAP from stationary sources. In the first 
stage, after EPA has identified categories of sources emitting one or 
more of the HAP listed in section 112(b) of the CAA, section 112(d) 
calls for us to promulgate national performance or technology-based 
emission standards for those sources. For ``major sources'' that emit 
or have the potential to emit any single HAP at a rate of 10 tons or 
more per year or any combination of HAP at a rate of 25 tons or more 
per year, these technology-based standards must reflect the maximum 
reductions of HAP achievable (after considering cost, energy 
requirements, and non-air health and environmental impacts) and are 
commonly referred to as MACT standards. We published the MACT standards 
for SOCMI on April 22, 1994 at 59 FR 19402 (codified at 40 CFR part 63, 
subparts F, G, and H). 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 eight years, under CAA 
section 112(d)(6).
    The second stage in standard-setting is described in CAA section 
112(f). This provision requires, first, that 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, the 
means and costs of controlling them, actual health effects to persons 
in proximity to emitting sources, and 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. The Congress did not act on any of the recommendations in the 
report, thereby triggering the second stage of the standard-setting 
process, the residual risk phase.
    Section 112(f)(2) requires us to determine for source categories 
subject to certain section 112(d) standards whether the emissions 
limitations protect public health with an ample margin of safety. 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 1-in-1 million,'' 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. The EPA must also adopt more stringent standards if necessary 
to prevent adverse environmental effect (defined in section 112(a)(7) 
as ``any significant and widespread adverse effect * * * to wildlife, 
aquatic life, or natural resources * * *.''), but must consider cost, 
energy, safety, and other relevant factors in doing so.

[[Page 34424]]

B. What are SOCMI facilities?

    The SOCMI is a segment of the chemical manufacturing industry that 
includes the production of many high-volume organic chemicals. The 
products of SOCMI are derived from approximately 10 petrochemical 
feedstocks. Of the hundreds of organic chemicals that are produced by 
the SOCMI, some are final products and some are the feedstocks for 
production of other non-SOCMI chemicals or synthetic products such as 
plastics, fibers, surfactants, pharmaceuticals, synthetic rubber, dyes, 
and pesticides. Production of such non-SOCMI end products is not 
considered to be part of SOCMI production and, as a result, the current 
MACT standards do not (and the proposed standards would not) apply to 
downstream synthetic products industries, such as rubber production or 
polymers production, that use chemicals produced by SOCMI processes.
    The HON currently applies to chemical manufacturing process units 
(CMPUs) that: (1) Are part of a major source as defined in CAA section 
112; (2) produce as a primary product a SOCMI chemical listed in table 
1 of 40 CFR part 63, subpart F; and (3) use as a reactant or 
manufacture as a product, by-product, or co-product one or more of the 
organic HAP listed in table 2 of 40 CFR part 63, subpart F.
    The HON defines a CMPU as the equipment assembled and connected by 
pipes or ducts to process raw materials and to manufacture an intended 
product. For purposes of the HON, a CMPU includes air oxidation 
reactors and their associated product separators and recovery devices; 
reactors and their associated product separators and recovery devices; 
distillation units and their associated distillate receivers and 
recovery devices; associated unit operations; and any feed, 
intermediate and product storage vessels, product transfer racks, and 
connected ducts and piping. A CMPU includes pumps, compressors, 
agitators, pressure relief devices, sampling connection systems, open-
ended valves or lines, valves, connectors, instrumentation systems, and 
control devices or systems.
    A SOCMI plant site can have several CMPUs, which could produce 
totally separate and non-related products. In the background 
information document for the HON, it was estimated that there were 729 
CMPUs nationwide. Two hundred thirty-eight facilities have been 
identified as subject to the HON. These HON facilities were identified 
after extensive review of facility lists compiled by the EPA's Office 
of Enforcement and Compliance Assurance, EPA Regional Offices, and the 
American Chemistry Council (ACC).
    The five kinds of HAP emission points that are currently regulated 
by the HON are storage vessels, process vents, wastewater collection 
and treatment operations, transfer operations, and equipment leaks. 
Each emission source type is briefly described below.
1. Storage Vessels
    Storage vessels contain chemical raw materials, products, and co-
products. Different types of vessels are used to store various types of 
chemicals. Gases (chemicals with vapor pressures greater than 14.7 
pounds per square inch absolute (psia)) are stored in pressurized 
vessels that are not vented to the atmosphere during normal operations. 
Liquids (chemicals with vapor pressures of 14.7 psia or less) are 
stored in horizontal, fixed roof, or floating roof tanks, depending on 
chemical properties and volumes to be stored. Liquids with vapor 
pressures greater than 11 psia are typically stored in fixed roof tanks 
that are vented to a control device. Volatile chemicals with vapor 
pressures up to 11 psia are usually stored in floating roof tanks 
because such vessels have lower emission rates than fixed roof tanks 
within this vapor pressure range.
    Emissions from storage vessels typically occur as working losses. 
As a storage vessel is filled with chemicals, HAP-laden vapors inside 
the tank become displaced and can be emitted to the atmosphere. Also, 
diurnal temperature changes result in breathing losses of organic HAP-
laden vapors from storage vessels.
2. Process Vents
    Many unit operations at SOCMI facilities generate gaseous streams 
that contain HAP. These streams may be routed to other unit operations 
for additional processing (i.e., a gas stream from a reactor that is 
routed to a distillation unit for separation) or may be vented to the 
atmosphere. Process vents emit gasses to the atmosphere, either 
directly or after passing through recovery and/or control devices. The 
primary unit operations in a SOCMI unit from which process vents 
originate are reactor and air oxidation process units, and from the 
associated product recovery and product purification devices. Product 
recovery devices include condensers, absorbers, and adsorbers used to 
recover products or co-products for use in a subsequent process, for 
use as recycle feed, or for sale. Product purification devices include 
distillation operations. The HON applies only to process vents that are 
associated with continuous (non-batch) air oxidation, other reactor 
processes, or distillation unit operations within a SOCMI process unit.
3. Process Wastewater
    For some synthetic organic chemicals, the manufacturing process 
generates wastewater streams that contain HAP. Sources of wastewater 
include: Water formed during the chemical reaction or used as a 
reactant in a process; water used to wash impurities from organic 
products or reactants; water used to cool organic vapor streams; and 
condensed steam from vacuum vessels containing organics. Organic 
compounds in the wastewater can volatilize and be emitted to the 
atmosphere from wastewater collection and treatment units if these 
units are open or vented to the atmosphere. Potential sources of HAP 
emissions associated with wastewater collection and treatment systems 
include drains, manholes, trenches, surface impoundments, oil/water 
separators, storage and treatment tanks, junction boxes, sumps, basins, 
and biological treatment systems.
4. Transfer Operations
    Synthetic organic chemical products are often transported by 
railcars or tank trucks. Chemicals are transferred to these vehicles 
through a loading rack, which can have multiple loading arms for 
connection to several transport vehicles. Emissions can occur during 
loading operations when residual vapors in transport vehicles and 
transfer piping are displaced by chemicals being loaded.
5. Equipment Leaks
    Equipment leaks are fugitive releases of process fluid or vapor 
from process equipment. These releases occur primarily at the interface 
between connected components of equipment. The basic equipment 
components that are prone to develop leaks include pumps, compressors, 
process valves, pressure relief devices, open-ended lines, sampling 
connections, flanges and other connectors, agitators, product 
accumulator vessels, and instrumentation systems.

C. What are the health effects of HAP emitted from SOCMI facilities?

    Of the 131 organic HAP regulated by the HON (table 2 to subpart F 
of part 63), EPA lists four as known carcinogens, 33 as probable 
carcinogens, and 15 as possible carcinogens. The EPA classified agents 
as carcinogens based on the weight of evidence in long-

[[Page 34425]]

term human studies of the association between cancer incidence and 
exposure to the agent and in animal studies conducted under controlled 
laboratory conditions. After evaluating the evidence, the agents were 
placed into one of the following five categories: A--human carcinogen, 
B--probable human carcinogen, C--possible human carcinogen, D--not 
classifiable as to human carcinogenicity, and E--evidence of 
noncarcinogenicity for humans. Category B is divided into two 
subcategories: B1--indicates limited human evidence and B2--indicates 
sufficient evidence in animals and inadequate or no evidence in humans.
    With the March 2005 publication of revised Guidelines for 
Carcinogen Risk Assessment, EPA no longer uses the ``known, possible, 
probable'' nomenclature for classifying the weight of evidence for 
carcinogenicity of chemical compounds. Instead, EPA provides narrative 
descriptions of the weight of evidence for carcinogenicity, as well as 
the classifications ``carcinogenic to humans,'' ``likely to be 
carcinogenic,'' ``suggestive evidence of carcinogenic potential,'' 
``inadequate information,'' and ``not likely.'' In time, the older 
classification scheme described above will be replaced.
    The International Agency for Research on Cancer (IARC) also 
classifies carcinogens based on the ``strength of the evidence for 
carcinogenicity arising from human and experimental animal data.'' 
There are four groups under the IARC classification system: Group 1--
the agent is carcinogenic to humans, Group 2A--the agent is probably 
carcinogenic to humans, Group 2B--the agent is possibly carcinogenic to 
humans, Group 3--the agent is not classifiable as to its 
carcinogenicity to humans, and Group 4--the agent is probably not 
carcinogenic to humans. Of the 51 HON HAP classified by IARC, four are 
Group 1, 33 are Group 2, and 14 are Group 3.
    Additionally, many of the HAP regulated by the HON may result in 
noncarcinogenic effects at sufficient exposures. There is a wide range 
of effects due to chronic exposures to HON HAP, such as the 
degeneration of olfactory epithelium, peripheral nervous system 
dysfunction, and developmental toxicity. Effects from acute exposures 
range from mild to severe, and include skin, eye, and respiratory 
system irritation. More detail on the health effects of individual HON 
HAP may be found in numerous sources, including http://www.epa.gov/iris.html, http://www.atsdr.cdc.gov/mrls.html, and http://

http://www.oehha.ca.gov/air/acute_rels/index.html.

D. What does the HON require?

    The HON was proposed December 31, 1992 (57 FR 62608), and the final 
rule was published April 22, 1994 (59 FR 19402). Subsequently, several 
revisions to the rule have been issued: the first dated September 20, 
1994 (59 FR 48175) and the last dated December 23, 2004 (69 FR 76859).
    The HON regulates organic HAP emissions from five types of emission 
points: Storage vessels, process vents, wastewater collection and 
treatment systems, transfer operations, and equipment leaks. For 
storage vessels, process vents, process wastewater streams, and 
transfer operations, the HON establishes applicability criteria to 
distinguish between Group 1 emission points and Group 2 emission 
points. Controls are required only for emission points meeting the 
Group 1 criteria. Group 2 emission points are subject to recordkeeping 
requirements only. Before implementation of the HON, total HAP 
emissions were estimated to be 570,000 tons per year (tpy). We 
estimated that after implementation of the HON, total HAP emissions 
would be 66,000 tpy.
    The HON provides many different control options, but the primary 
control requirements are summarized below.
1. Storage Vessels
    The HON requires that Group 1 vessels be equipped and operated with 
an internal or an external floating roof, or reduce organic HAP 
emissions by at least 95 percent. A Group 1 vessel has a capacity 
greater than or equal to 40,000 gallons and contains a HAP with a vapor 
pressure greater than or equal to 0.75 psia. A vessel is also Group 1 
if it has a capacity greater than or equal to 20,000 gallons and less 
than 40,000 gallons and contains a HAP with a vapor pressure greater 
than or equal to 1.9 psia.
2. Process Vents
    The HON requires that the organic HAP emissions from Group 1 
process vent streams be reduced by at least 98 percent by weight or 
achieve an outlet concentration of 20 parts per million by volume 
(ppmv) or less. A Group 1 process vent stream has a total organic HAP 
concentration of greater than or equal to 50 ppmv and a total resource 
effectiveness (TRE) of less than or equal to 1.0. Facilities also have 
the option of sending the process vent to a flare or maintaining a TRE 
index greater than 1.0. The TRE index is a measure of how costly a 
particular process vent is to control (the higher the TRE index, the 
more costly the control).
3. Process Wastewater
    The HON requires that Group 1 wastewater streams be treated to 
reduce the HAP mass in the streams. Group 1 wastewater streams are 
streams that meet one of several minimum flow and HAP concentration 
criteria in the rule. The required mass removals are HAP-specific and 
range from 31 percent (e.g., for methanol) to 99 percent (e.g., for 
benzene). Emissions from collection and management units must be 
suppressed from the point of generation to the treatment device. Air 
emissions from treatment systems (except for open biological treatment 
systems which have different requirements) must be collected in a 
closed vent system and conveyed to a control device that reduces HAP 
emissions by 95 percent (or achieves an outlet concentration of 20 ppmv 
or less for combustion devices).
4. Transfer Operations
    The HON requires control of Group 1 transfer racks to achieve a 98 
percent reduction of organic HAP or an outlet concentration of 20 ppmv. 
Alternatively, facilities can use vapor balancing systems. A Group 1 
transfer rack is a transfer rack that annually loads greater than or 
equal to 0.17 million gallons of liquid products that contain organic 
HAP with a rack weighted average vapor pressure greater than or equal 
to 1.5 psia.
5. Equipment Leaks
    The HON requires equipment and work practice standards (in the form 
of a leak detection and repair program) to reduce equipment leak 
emissions. The equipment leak provisions apply to all equipment 
components that are associated with a process subject to the HON and 
that are in organic HAP service for 300 hours per year or more. The HON 
requires valves to be monitored once per month (or implementation of a 
quality improvement program) at each process unit with two percent or 
greater leaking valves. The monitoring frequency may be decreased as 
the percentage of leakers decreases or if the equipment leaks standards 
are met over consecutive periods.

II. Summary of Proposed Revised Standards

    This proposal provides two options that we expect to choose between 
for revising the HON rule. The first option is to retain the current 
HON rule. The second option is to revise subparts F, G, and H to 
require more stringent standards for process vents, storage vessels, 
and equipment leaks that emit

[[Page 34426]]

or store certain HAP. As explained below, we propose that either option 
would meet the requirements of both section 112(f)(2) and 112(d)(6). 
Their difference results from how we weigh certain risk factors 
(specifically, maximum individual lifetime cancer risk versus cancer 
incidence, and their relative relationship to costs) within our 
determination of what is necessary to protect public health with an 
ample margin of safety under section 112(f)(2), and of what changes are 
necessary under section 112(d)(6).

A. Summary of Option 1

    Under this option, the control requirements of 40 CFR subpart F, G, 
and H would remain the same as under the current rule, and we would not 
revise applicability criteria to require currently uncontrolled storage 
vessels and process vents to control emissions, nor would we reduce the 
percentage of leaking valves.

B. Summary of Option 2

    Under this option, the control requirements of 40 CFR subpart G 
would remain the same as under the current rule, but the applicability 
criteria for Group 1 storage vessels and process vents would be revised 
so that additional emission points would be required to control 
emissions. For equipment leaks, the first option would reduce, in 
subpart H, the percentage of leaking valves.
    The existing applicability criteria for equipment leaks and Group 1 
criteria for storage vessels and process vents would continue to apply. 
After the rule becomes effective, an additional criterion would be 
added. The additional criterion would apply only to emission points 
that emit maleic anhydride, methyl bromide, acrolein, and any HAP for 
which inhalation cancer unit risk estimates (UREs) have been 
developed.\1\ A list of these HAP is given in proposed table 38 of 40 
CFR, part 63, subpart G. This list may be amended over time as more 
information indicates that some HAP should be added or removed.
---------------------------------------------------------------------------

    \1\ The URE is the upper-bound excess lifetime cancer risk 
estimated to result from continuous exposure to an agent at a 
concentration of 1 microgram per cubic meter ([mu]g/m3) 
in air. For example, if a URE of 1.5 x 10-6 per [mu]g/
m3 is reported, then 1.5 excess cancer cases are expected 
to develop per 1,000,000 people if exposed daily for a lifetime to 1 
ug of the chemical in 1 cubic meter of air.
---------------------------------------------------------------------------

    The proposed changes to the standards, based on the second control 
option, are summarized below:

------------------------------------------------------------------------
       Emission source          Proposed changes to standards (Option 2)
------------------------------------------------------------------------
Storage vessels..............  A group 1 storage vessel means a Group 1
                                storage vessel as currently defined in
                                Sec.   63.111 to subpart G of part 63.
                                On or after [DATE THE FINAL RULE IS
                                PUBLISHED IN THE FEDERAL REGISTER], a
                                group 1 storage vessel also includes
                                storage vessels that store one or more
                                HAP listed in table 38 to subpart G of
                                part 63, and have a combined HAP
                                emission rate greater than 4.54
                                megagrams per year (5.0 tons HAP per
                                year) on a rolling 12-month average.
Process vents................  A group 1 process vent means a Group 1
                                process vent as currently defined in
                                Sec.   63.111 to subpart G of part 63.
                                On or after [DATE THE FINAL RULE IS
                                PUBLISHED IN THE FEDERAL REGISTER], a
                                group 1 process vent also includes
                                process vents for which the vent stream
                                emits one or more HAP listed in table 38
                                to subpart G of part 63, and the TRE
                                index value is less than or equal to
                                4.0.
Equipment leaks..............  For CMPUs containing at least one HAP
                                listed in table 38 to subpart G of part
                                63, on or after [DATE THE FINAL RULE IS
                                PUBLISHED IN THE FEDERAL REGISTER],
                                monthly monitoring of equipment
                                components is required until the process
                                unit has fewer than 0.5 percent leaking
                                valves in gas/vapor service and in light
                                liquid service.
------------------------------------------------------------------------

    For storage vessels, emissions would be computed using the 
procedures in Sec.  63.150. Group 2 storage vessels that contain table 
38 HAP would be required to maintain records of rolling 12-month 
average HAP emissions. For equipment leaks, the frequency of monitoring 
could be reduced to quarterly, semi-annually, and annually if 
successive monitoring periods show that facilities are able to maintain 
less than 0.5 percent leakers. Monthly monitoring would be required if 
the percent leakers exceeds 0.5 percent.
    Under Option 2, we are also proposing compliance dates for sources 
subject to the proposed revised standards pursuant to section 112(i) of 
the CAA. When Congress amended the CAA in 1990, it established a new, 
comprehensive set of provisions regarding compliance deadlines for 
sources subject to emissions standards and work practice requirements 
that EPA promulgates under section 112. However, as discussed later in 
this section of this preamble, Congress also left in place other 
provisions in section 112(f)(4) that in certain respects are redundant 
or conflict with the new compliance deadline provisions. These 
provisions also fail to accommodate the new State-administered air 
operating permit program added in title V of the amended CAA.
    For new sources, section 112(i)(1) requires that after the 
effective date of ``any emission standard, limitation, or regulation 
under subsection (d), (f) or (h), no person may construct any new major 
source or reconstruct any existing major source subject to such 
emission standard, regulation or limitation unless the Administrator 
(or State with a permit program approved under title V) determines that 
such source, if properly constructed, reconstructed and operated, will 
comply with the standard, regulation or limitation.'' Section 112(a)(4) 
defines a ``new source'' as ``a stationary source the construction or 
reconstruction of which is commenced after the Administrator first 
proposes regulations under this section establishing an emission 
standard applicable to such sources.'' Under sections 112(e)(10) and 
112(f)(3), any section 112(d)(6) emission standards and any residual 
risk emission standards shall become effective upon promulgation. This 
means generally that a new source that is constructed or reconstructed 
after this proposed rule is published must comply with the final 
standard, when promulgated, immediately upon the rule's effective date 
or upon the source's start-up date, whichever is later.
    There are some exceptions to this general rule. First, section 
112(i)(7) provides that a source for which construction or 
reconstruction is commenced after the date an emission standard is 
proposed pursuant to subsection (d) but before the date a revised 
emission standard is proposed under subsection (f) shall not be 
required to comply with the revised standard until 10 years after the 
date construction or reconstruction commenced. This provision ensures 
that new sources that are built in compliance with MACT will not be 
forced to

[[Page 34427]]

undergo modifications to comply with a residual risk rule unreasonably 
early.
    In addition, sections 112(i)(2)(A) and (B) provide that a new 
source which commences construction or reconstruction after a standard 
is proposed, and before the standard is promulgated, shall not be 
required to comply with the promulgated standard until three years 
after the rule's effective date, if the promulgated standard is more 
stringent than the proposed standard and the source complies with the 
proposed standard during the three-year period immediately after 
promulgation. This provision essentially treats such new sources as if 
they are existing sources in giving them a consistent amount of time to 
convert their operations to comply with the more stringent final rule 
after having already been designed and built according to the proposed 
rule.
    For existing sources, section 112(i)(3)(A) provides that after the 
effective date of ``any emission standard, limitation or regulation 
promulgated under this section and applicable to a source, no person 
may operate such source in violation of such standard, limitation or 
regulation except, in the case of an existing source, the Administrator 
shall establish a compliance date or dates * * * which shall provide 
for compliance as expeditiously as practicable, but in no event later 
than 3 years after the effective date of such standard[.]'' This 
potential 3-year compliance period for existing sources under section 
112(i)(3) matches the 3-year compliance period provided for new sources 
subject to section 112(d), (f), or (h) standards that are promulgated 
to be more stringent than they were proposed, as provided in sections 
112(i)(1) and (2).
    As for new sources, there are exceptions to the general rule for 
existing sources under section 112(i)(3), the most relevant being 
section 112(i)(3)(B) allowance that EPA or a State title V permitting 
authority may issue a permit granting a source an additional one year 
to comply with standards ``under subsection (d)'' if such additional 
period is necessary for the installation of controls. As explained 
below, EPA now believes that this reference to only subsection 112(d), 
rather than to section 112 in general, was accidental on Congress' part 
and presents a conflict with the rest of the statutory scheme Congress 
enacted in 1990 to govern compliance deadlines under the amended 
section 112.
    Even though, in 1990, Congress amended section 112 to include the 
comprehensive provisions in subsection 112(i) regarding compliance 
deadlines, the enacted CAA also included provisions in section 112(f), 
leftover from the previous version of the Act, that apply compliance 
deadlines for sources subject to residual risk rules. These deadlines 
differ in some ways from the provisions of section 112(i). First, 
section 112(f)(4) provides that no air pollutant to which a standard 
``under this subsection applies may be emitted from any stationary 
source in violation of such standard * * *'' For new sources, this is a 
redundant provision, since the new provisions added by Congress in 
sections 112(i)(1), (2), (3), and (7)--which explicitly reach standards 
established under section 112(f)--already impose this prohibition with 
respect to new sources and provide for the allowable exceptions to it. 
In contrast, for new sources, the prohibition in section 112(f)(4) 
provides for no exception for a new source built shortly before a 
residual risk standard is proposed, makes no reference to the new title 
V program as an implementation mechanism, and, where promulgated 
standards are more stringent than their proposed versions, makes no 
effort to align compliance deadlines for new sources with those that 
apply for existing sources. From the plain language of section 112(i), 
it is clear that Congress intended in the 1990 amendments to 
comprehensively address the compliance deadlines for new sources 
subject to any standard under either subsections 112(d), (f), or (h), 
and to do so in a way that accommodates both the new title V program 
added in 1990 and the fact that where circumstances justify treating a 
new source as if it were an existing source, a substantially longer 
compliance period than would otherwise apply is necessary and 
appropriate. It is equally clear that the language in section 112(f)(4) 
fails on all these fronts for new sources.
    In addition, for existing sources, section 112(f)(4)(A) provides 
that a residual risk standard and the prohibition against emitting HAP 
in violation thereof ``shall not apply until 90 days after its 
effective date[.]'' However, section 112(f)(4)(B) states that EPA ``may 
grant a waiver permitting such source a period up to two years after 
the effective date of a standard to comply with the standard if the 
Administrator finds that such period is necessary for the installation 
of controls and that steps will be taken during the period of the 
waiver to assure that the health of persons will be protected from 
imminent endangerment.'' These provisions are at odds with the rest of 
the statutory scheme governing compliance deadlines for section 112 
rules in several respects. First, the 90-day compliance deadline for 
existing sources in section 112(f)(4)(A) directly conflicts with the 
up-to-3-year deadline in section 112(i)(3)(A) allowed for existing 
sources subject to ``any'' rule under section 112. Second, the section 
112(f)(4)(A) deadline results in providing a shorter deadline for 
ordinary existing sources to comply with residual risk standards than 
would apply under section 112(i)(2) to new sources that are built after 
a residual risk standard is proposed but a more stringent version is 
promulgated. Third, while both section 112(i)(1), for new sources 
subject to any section 112(d), (f), or (h) standard, and section 
112(i)(3), for existing sources subject to any section 112(d) standard, 
refer to and rely upon the new title V permit program added in 1990 and 
explicitly provide for State permitting authorities to make relevant 
decisions regarding compliance and the need for any compliance 
extensions, section 112(f)(4)(B) still reflects the pre-1990 statutory 
scheme in which only the Administrator is referred to as a decision-
making entity, notwithstanding the fact that even residual risk 
standards under section 112(f) are likely to be delegated to States for 
their implementation, and will be reflected in sources' title V permits 
and need to rely upon the title V permit process for memorializing any 
compliance extensions for those standards.
    While we appreciate the fact that section 112(i)(3)(B) refers 
specifically only to standards under subsection 112(d), which some 
might argue means that subsection 112(i)(3), in general, applies only 
to existing sources subject to section 112(d) standards, we believe 
that Congress inadvertently limited its scope and created a statutory 
conflict in need of our resolution. Notwithstanding the language of 
subparagraph (B), section 112(i)(3)(A) by its terms applies to ``any'' 
standard promulgated under ``section'' 112, which includes those under 
subsection 112(f), in allowing up to a three year compliance period for 
existing sources. Moreover, Congress clearly intended the section 
112(i) provisions applicable to new sources to govern compliance 
deadlines under section 112(f) rules, notwithstanding the language of 
section 112(f)(4). This is because sections 112(i)(1) and (2) 
explicitly reach standards under section 112(f). To read section 
112(i)(3)(B) literally as reaching only section 112(d) standards, with 
section 112(f)(4)(B) reaching section 112(f) standards, leaves the 
question as to whether there can be compliance extensions for section

[[Page 34428]]

112(h) standards completely unaddressed by the statute, even though it 
may in fact be necessary in complying with a section 112(h) work 
practice standard to install equipment or controls. A narrow reading of 
the scope of section 112(i)(3) also ignores the fact that in many 
cases, including that of this proposed rule, the governing statutory 
authority will be both section 112(f)(2) and section 112(d)(6)--the 
only reasonable way to avoid a conflict in provisions controlling 
compliance deadlines for existing sources in these situations is to 
read the more specific and comprehensive set of provisions, those of 
section 112(i), as governing both aspects of the regulation.
    Nothing in the legislative history suggests that Congress knowingly 
intended to enact separate schemes for compliance deadlines for 
residual risk standards and all other standards adopted under section 
112. Rather, comparing the competing Senate and House Bills shows that 
each bill contained its own general and/or specific versions of 
compliance deadline provisions, and that when the bills were reconciled 
in conference the two schemes were both accidentally enacted, without 
fully modifying the various compliance deadline provisions in accord 
with the modifications otherwise made to the section 112 amendments in 
conference.
    We recognize that our existing regulations in the part 63 General 
Provisions currently reflect the dual scheme presented by sections 
112(f)(4) and 112(i) (See 40 CFR 63.6(c)(2), 63.6(i)(4)(ii)). In the 
near future, we intend to revise those regulations to comport with our 
interpretation, as explained above, to avoid confusion and situations 
where a rule incorporates those provisions by reference such that 
compliance deadlines are inconsistent with our interpretation. In the 
meantime, notwithstanding the part 63 General Provisions, we are 
proposing a compliance deadline for existing sources, under Option 2, 
of three years for process vents and storage vessels and one year for 
equipment leaks. The proposed compliance deadline for existing sources 
of three years for process vents and storage vessels is realistic for 
any affected facility that has to plan their control strategy, purchase 
and install the control device(s), and bring the control device online. 
Less time is required for compliance with the new equipment leak 
requirements, but plants will have to identify affected equipment and 
modify their existing leak detection and repair program to meet the new 
requirements for monitoring frequency.

III. Rationale for the Proposed Rule

A. What is our approach for developing residual risk standards?

    Following our initial determination that the individual most 
exposed to emissions from the category considered exceeds a 1-in-1 
million individual lifetime cancer risk, our approach to developing 
residual risk standards is based on a two-step determination of 
acceptable risk and ample margin of safety. The first step is the 
consideration of acceptable risk. The second step determines 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 required to 
prevent adverse environmental effect after the consideration of costs, 
energy, safety, and other relevant factors).
    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) refers positively to the 
interpretation of these terms in our 1989 rulemaking (54 FR 38044, 
September 14, 1989), ``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),'' 
essentially directing us to use the interpretation set out in that 
notice. 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 a report on residual risk that we 
intended to utilize the Benzene NESHAP approach in making CAA section 
112(f) residual risk determinations (see Residual Risk Report to 
Congress, March 1999, EPA-453/R-99-001, p. ES-11).
    In the Benzene NESHAP (54 FR 38044, September 14, 1989), we stated 
as an overall objective: * * * in protecting public health with an 
ample margin of safety, we strive 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 
facility would have if he or she were exposed to the maximum pollutant 
concentrations for 70 years.''
    The Agency also stated that, ``The 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.'' The Agency 
went on to conclude that ``estimated incidence would be weighed along 
with other health risk information in judging acceptability.\2\'' As 
explained more fully in our Residual Risk Report to Congress, 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).
---------------------------------------------------------------------------

    \2\ In the benzene decision, the Agency considered the same risk 
measures in the ``acceptability'' analysis as in the ``margin of 
safety'' analysis, stating: ``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 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 a level that provides an ample margin of 
safety to protect the public health, as required by section 112.''
---------------------------------------------------------------------------

B. How did we estimate residual risk?

    The Residual Risk Report to Congress provides the general framework 
for conducting risk assessments to support decisions made under the 
residual risk program. As acknowledged by the report, the design of 
each risk assessment would have some common elements, including a 
problem formulation phase, an analysis phase, and the risk 
characterization phase.
    The primary risk assessment for the SOCMI source category focused 
on inhalation exposures, both chronic and acute, to HAP emissions from 
CMPUs that are subject to the HON. The primary risk assessment was 
reviewed by Agency scientists before being used for this proposed 
rulemaking. The emissions estimates used in the primary risk assessment 
represented actual emissions that remain after the application of MACT, 
not emissions at the rate allowed by the HON requirements 
(``allowable'' emissions) that may be higher than actual emissions. 
Some of the emission points subject to the HON may be controlled to a 
higher level than required by the rules and some Group 2 points may be 
controlled even though the rule does not require them to be. This may 
be due to some State or local rules that are more stringent than the 
HON, or because some facilities may reduce emissions for reasons other 
than regulatory requirements. This means that the

[[Page 34429]]

estimated risks based on allowable emissions would be higher than the 
risks estimated using actual emissions.
    For some HON emission points, we could estimate allowable 
emissions; for others, it is nearly impossible. For equipment leaks, 
because the standards are work practice standards the actual emissions 
and allowable emissions are likely the same for equipment in the leak 
detection and repair program required by the HON. More frequent 
monitoring of equipment components (for example, monthly instead of 
quarterly) could result in actual emissions being lower than allowable 
emissions, but few, if any, sources monitor more frequently than 
required by the HON. For wastewater and process vents, if a facility 
chooses to control an emission point (to the level required in the 
HON), there is no requirement to determine whether the point is 
actually required to be controlled. A requirement to determine the 
applicability of controls for such emission points was intentionally 
not included in the HON because it was seen as an unnecessary burden 
for points that would be controlled anyway. Consequently, there are 
some emission points for which there is no readily available data that 
can be used to determine the applicability of control requirements. 
Without such data, there is no accurate way to determine allowable 
emissions under the current rule. In addition, HAP emissions from 
wastewater sources are likely controlled to a greater extent than the 
rules require, but this overcontrol is impossible to estimate. 
Emissions from transfer operations are small relative to the emissions 
from other points, with emissions from controlled points nationally 
accounting for less than one percent of total HON HAP emissions. Given 
the small contribution to total emissions from transfer operations, any 
differences between actual and allowable emissions would not be 
significant relative to the total emissions from all HON emission 
points.
    While we acknowledge that there is some uncertainty regarding the 
differences between actual and allowable emissions, we believe that 
there is neither a substantial amount of overcontrol of Group 1 sources 
nor control of Group 2 sources so that actual emissions are a 
reasonable approximation of allowable emissions. Basing this analysis 
on actual emissions provides an acceptable approach to determining the 
remaining risks to public health and the environment after application 
of the MACT standards. Indeed, in this case, given the impossibility of 
definitively estimating allowable emissions, we have no choice but to 
rely upon the best available alternative information for assessing 
remaining risks after application of MACT, industry supplied actual 
emissions data. Uncertainty in the use of this data can be considered 
in the selection of the standards as appropriate.
    Screening level assessments were also conducted to examine human 
health and ecological risk due to multipathway exposure and to examine 
the risks from entire plant sites (i.e., HON CMPUs and other HAP-
emitting processes). A full discussion of the primary and screening 
level assessments is provided in the risk characterization document in 
the public docket.
1. How did we estimate the atmospheric dispersion of HAP emitted from 
HON CMPU sources?
    To estimate the dispersion of HAP emitted from HON CMPUs for the 
inhalation and multipathway assessments, we used the Human Exposure 
Model, version 3 (HEM-3), which incorporated the Industrial Source 
Complex Short-term model, version 3 (ISCST-3). The ISCST3 dispersion 
model is one of EPA's recommended models for assessing pollutant 
concentrations from industrial facilities. The ISCST3 model handles a 
wide range of different source types that may be associated with an 
industrial source complex, including stack sources, area sources, 
volume sources, and open pit sources.
    Inputs to the HEM-3 include source data to characterize the 
emissions from the facility, the emission sources at the facility, and 
the location of the facility. For the inhalation and multipathway 
assessments, we used site-specific information for the base year 1999 
for 104 of the 238 existing HON facilities. These data were collected 
by the ACC through a voluntary survey and provided to EPA. These data 
consisted of organic HAP emissions from five types of emission points 
subject to the HON and included stack parameters, emission rates, and 
location coordinates. Data were provided for 271 HON CMPUs in the 1999 
data collection. When scaled to 238 HON facilities, 732 HON CMPUs would 
be estimated for the industry. In the background information for the 
HON, it was estimated that there were 729 HON CMPUs nationwide. The 
similarities in the structure of the industry indicate that the 1999 
collected data provide a reasonable picture of post-compliance 
emissions of organic HAP, and that the process unit information used in 
the residual risk analysis is representative of the CMPUs for the 
entire industry.
    We recognize that the 1999 survey data have some uncertainties 
regarding the sources responding to a voluntary data request and the 
emissions reported. It is unclear the amount of bias that may exist in 
the data and the extent to which the 104 facilities in the survey are 
representative of the risks posed by the remaining facilities (see 
section III.C.1. of this preamble for additional discussion). However, 
the 1999 survey data are still the most detailed and comprehensive data 
available, and we conclude that the data are appropriate for use in 
conducting this residual risk assessment. Uncertainty in the use of 
this data can be considered in the selection of the standards as 
appropriate.
    Some inorganic HAP, such as hydrochloric acid and chlorine, may be 
emitted from HON sources. However, these compounds were not considered 
in this risk assessment because data were not available to characterize 
emissions of those HAP. The HON regulates emissions of organic HAP only 
and the 1999 ACC data provided information on organic HAP emissions 
only. As discussed below in III.B.4, an additional analysis was 
conducted using information in the National Emissions Inventory (NEI) 
to estimate the risk from the entire plant site at which the HON CMPU 
are located. The NEI information contained information on both organic 
and inorganic HAP emitted from each facility. A comparison between the 
analyses using the two different data sets showed that there were no 
cases where the concentration of an inorganic HAP emitted from a HON 
CMPU exceeded its reference value. Therefore, we concluded that not 
including inorganic HAP in the primary risk assessment does not affect 
the results of the analysis and that no further assessment of inorganic 
HAP emissions is necessary.
2. How did we assess public health risk associated with HAP emitted 
from HON CMPUs?
    The primary tool used to estimate individual and population 
exposures in the inhalation and multipathway assessments was the Human 
Exposure Model, Version 3 (HEM-3). The HEM-3 incorporates the ISCST3 
air dispersion model and 2000 Census data, along with HAP dose response 
and reference values, to estimate chronic and acute human health risks 
and population exposure. This model is considerably more sophisticated, 
and less conservative, than tools traditionally associated with 
scoping-type analyses

[[Page 34430]]

(such as use of the Human Exposure Model, version 1.5). More 
information on HEM-3 is available from the HEM-3 User's Guide.
    The HEM-3 performs detailed analyses of acute and chronic air 
pollution risks for populations located near industrial emission 
sources. The HEM-3 performs three main operations: dispersion modeling, 
estimation of human health risks, and estimation of population 
exposure. In order to perform these calculations, HEM-3 draws on three 
data libraries provided with the model: A library of meteorological 
data for over 60 stations, a library of census block internal point 
locations, populations, and elevations to provide the basis for human 
exposure calculations, and a library of pollutant unit risk factors and 
reference concentrations used to calculate risks.
    In our assessment of public health risk associated with HAP emitted 
from HON CMPUs, we considered risks of cancer and other health effects. 
Cancer risks associated with inhalation exposure were assessed using 
lifetime cancer risk estimates (i.e., assuming 70 years of exposure 24 
hours a day for all individuals in a given location). The noncancer 
risks were characterized through the use of hazard quotient (HQ) and 
hazard index (HI) estimates. The HQ and HI also assume continuous 
lifetime exposures. An HQ compares an estimated chemical intake (dose) 
with a reference level below which adverse health effects are unlikely 
to occur. Within the context of inhalation risk, EPA uses a ``Reference 
Concentration (RfC)''. An RfC is 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. It can be derived from a NOAEL, LOAEL, or benchmark 
concentration, with uncertainty factors generally applied to reflect 
limitations of the data used. An HQ is calculated as the ratio of the 
exposure concentration of a pollutant to its health-based reference 
concentration. If the HQ is calculated to be less than 1, then no 
adverse health effects are expected as a result of the exposure. 
However, an HQ exceeding 1 does not translate to a probability that 
adverse effects will occur. Rather, it suggests the possibility that 
adverse health effects may occur. An HI is the sum of HQ for pollutants 
that target the same organ or system. As with the HQ, values that are 
below 1.0 are considered to represent exposure levels with no 
significant risk of adverse health effects.
3. How did we assess multipathway impacts of HAP emissions from HON 
CMPUs?
    The HON CMPUs at six of the 238 facilities emit HAP that are of 
concern for potential adverse health impacts from pathways other than 
inhalation (e.g., soil or fish ingestion). These HAP are often termed 
persistent bioaccumulative toxics (PBTs). When deposited into soil and 
water, PBT may be taken up by organisms and passed along the food 
chain. The concentration of PBT in tissues can increase beyond the 
concentration of the surrounding environment from one link in a food 
chain to another (i.e., bioaccumulation and biomagnification). The 
multipathway assessments estimated both human health and ecological 
adverse impacts. Ecological impacts increase with PBTs because plants 
and wildlife are exposed to pollutants in soil, water, and the food 
chain, in addition to the air.
    Modeling the fate and transport of the PBTs through air, soil and 
the food chain, and watersheds is a more complex and uncertain task 
than estimating air transport for the inhalation pathway. Because of 
the complexity and increased level of effort in both time and resources 
and because gas phase compounds emitted from HON CMPUs are not 
transferred to other media to any appreciable degree, we conducted a 
simplified screening level approach to estimating media concentrations 
of the PBTs. Due to the wide variety of species of plants and animals 
potentially exposed, we needed to simplify fate and transport inputs 
and methods through a health-protective, screening level approach and 
screening level dose-response values.
    Adverse impacts on individuals of the most sensitive species 
potentially exposed for each exposure pathway and HAP were first 
estimated to indicate whether there is a potential problem to the 
ecosystem. If no adverse impacts to the most sensitive species are 
predicted, no adverse ecosystem impacts would be expected. If risks are 
estimated to exceed a level of concern in the screening assessment, 
more refined inputs and modeling techniques would be employed in 
further assessments.
4. How did we assess risks for the entire plant site?
    Due to the substantial co-location of HON CMPUs with other HAP-
emitting processes, we also characterized how the risks resulting from 
emissions from HON CMPUs relate to the risks resulting from emissions 
from all processes (HON and non-HON processes) at the entire plant 
site. In addition, we were interested in learning how well the HON CMPU 
data, available for approximately half of the industry, represented the 
entire industry. Therefore, an additional analysis was conducted to 
estimate the risk from all HAP emitting processes at the entire plant 
site.
    This analysis was conducted for 226 facilities where CMPUs subject 
to the HON are located. The 1999 data submitted by the ACC that were 
used in the CMPU analysis described in section B.1 could not be used 
for this plant-level analysis because data were provided only on HON 
CMPUs. However, the 1999 NEI contained information on HAP emissions 
from the entire facility and was used for the analysis (hereafter 
referred to as the NEI Assessment). On the other hand, the NEI data 
were not used for the primary risk assessment because of the difficulty 
in apportioning emissions to only HON CMPUs.
    The NEI Assessment considered only chronic cancer and noncancer 
risk (not acute risk) because focusing only on chronic risk is adequate 
to compare the risk posed by the HON CMPUs to the risk posed by the 
entire plant site. Also, without additional information, it would be 
difficult to characterize short-term emissions of sources that are not 
affected by the HON. Whereas the HON CMPUs at a facility are typically 
continuous and assumptions can be made about the temporal variability 
of emissions, other processes may not be continuous and characterizing 
the short-term emissions would be difficult.
    The HEM-3 model was used to estimate the maximum individual 
lifetime cancer risks and lifetime noncancer HI values estimated to 
result from emissions at each of these facilities. In addition, a brief 
analysis was conducted to compare how the HON CMPUs contributed to the 
situations where there is substantial co-location of SOCMI process 
units with other HAP-emitting processes

C. What are the residual risks from HON CMPUs?

1. Health Risks From Chronic Inhalation Exposure
    Table 1 of this preamble shows the estimated maximum individual 
lifetime cancer risk, maximum HI resulting from lifetime exposure, 
population risk, and cancer incidence associated with HON CMPUs at 104 
of the 238 existing facilities for which emissions data were available. 
The size of the population at risk and cancer incidence estimated to be 
associated with HON CMPUs were

[[Page 34431]]

extrapolated to the entire source category of 238 existing facilities 
with HON CMPUs using the ratio of 2.3 (238/104). An inherent assumption 
in using the simple 238/104 ratio is that the population densities 
around the plants not assessed are similar to those of the 104 plants 
that were assessed.
    The maximum individual lifetime cancer risk associated with any 
source in the category is estimated to be approximately 100-in-1 
million. This estimate characterizes the lifetime risk of developing 
cancer for the individual facing the highest estimated exposure over a 
70-year lifetime. With respect to chronic noncancer effects, HON CMPUs 
at two facilities have a maximum respiratory HI that barely exceeds 1, 
with only 20 people estimated to be exposed to HI levels greater than 
1. As noted earlier, even an HI of 1 does not necessarily suggest a 
likelihood of adverse effects.

 Table 1.--Risk Estimates Due to HAP Exposure Based on 70-Year Exposure
                                Duration
------------------------------------------------------------------------
                                                            Results
                                    Results for 104     extrapolated to
            Parameter                  surveyed            all  238
                                      facilities          facilities
------------------------------------------------------------------------
Maximum individual lifetime                   100                  100
 cancer risk (in a million).....
* Maximum hazard index (chronic                 1                    1
 respiratory effects)...........
Estimated size of population at
 risk from all HON CMPUs:
    >1-in-1 million.............          850,000            2,000,000
    >10-in-1 million............            4,000                9,000
    >100-in-1 million...........                0                    0
Annual cancer incidence (No. of                 0.06                 0.1 
 cases).........................
------------------------------------------------------------------------
* An HQ exceeding 1 does not translate to a probability that adverse
  effects will occur. Rather, it suggests the possibility that adverse
  effects may occur.

    We compared the highest risks (maximum individual lifetime cancer 
risk and maximum chronic HI) estimated for HON CMPUs at facilities in 
the source category to the highest estimated risks from the NEI 
Assessment. In the HON CMPU assessment conducted on the 104 facilities, 
HON CMPUs at one facility were estimated to have a maximum individual 
lifetime cancer risk of 100-in-1 million. Extrapolating this result to 
the rest of the industry (i.e., 238 facilities) suggests that HON CMPUs 
at two facilities are likely to be associated with a cancer risk of 
100-in-1 million. In the NEI Assessment, three facilities were 
estimated to have a maximum individual lifetime cancer risk greater 
than 100-in-1 million where the risk was driven by HAP emissions from a 
HON CMPU. The maximum individual lifetime cancer risk estimated for the 
NEI Assessment was 300-in-1 million.
    For noncancer effects, the HON CMPUs at one of the 104 facilities 
were estimated to have an HI of 1 in the HON CMPU assessment. 
Extrapolating these results to the rest of the industry suggests HON 
CMPUs at two facilities are estimated to have an HI of 1 for chronic 
respiratory effects. In the NEI Assessment, five facilities were 
estimated to have a maximum HI greater than 1 where risk was driven by 
HAP emissions from HON CMPUs. The maximum estimated HI from the NEI 
Assessment was 6.
    In comparing the two risk assessments, the extrapolated results 
from the HON CMPU assessment are relatively consistent with the NEI 
Assessment in terms of the number of facilities where HON CMPUs pose 
risks in the range of 100-in-1 million. In addition, the magnitude of 
the risks from the two studies is relatively close, considering the 
health-protective nature of the NEI Assessment. Therefore, we 
determined it was appropriate to use the estimated risks from the HON 
CMPU assessment, which represents about half of the facilities in the 
industry, to represent the risks from the entire industry. 
Nevertheless, we acknowledge that the risks associated with HON 
facilities not specifically included in this assessment may be higher 
or lower than those assessed. Uncertainty in the use of this data can 
be considered in the selection of the standards as appropriate.
    EPA toxicological assessments are currently underway for several 
HAP emitted from HON CMPUs. For example, the cancer inhalation URE for 
ethylene oxide is under review. Ethylene oxide is one of the HAP that 
contributes significantly to the cancer risks for several HON CMPUs. 
EPA has not yet completed a full evaluation of the data on which it 
will determine a cancer URE for ethylene oxide. The schedule for the 
ethylene oxide review and the reviews of other HAP can be found at: 
http://cfpub.epa.gov/iristrac.

    Under section 112(o)(7) of the CAA, we are required to issue 
revised cancer guidelines prior to the promulgation of the first 
residual risk rule under section 112(f) (an implication being that we 
should consider these revisions in the various residual risk rules). We 
have issued revised cancer guidelines and also supplemental guidance 
that specifically address the potential added susceptibility from 
early-life exposure to carcinogens. The supplemental guidance provides 
guidance for adjusting the slope of the dose response curve by applying 
``age-dependent adjustment factors'' (which translates into a factor of 
1.6 for lifetime exposures) to incorporate the potential for increased 
risk due to early-life exposures to chemicals that are thought to be 
carcinogenic by a mutagenic mode of action.
    Some evidence indicates that several HAP that are emitted from HON 
CMPUs and that dominate the risks in our assessment may be carcinogenic 
by a mutagenic mode of action, although for most carcinogenic HAP the 
formal determination of mode of action has not yet been made. Thus, we 
did not apply age-dependent adjustment factors to the cancer risk 
estimates in our residual risk assessment for HON CMPUs.
2. Health Risks From Acute Inhalation Exposure
    In addition to chronic cancer and noncancer effects, acute effects 
were also assessed. We used the ratio analogous to the HQ in which we 
compared the maximum 1-hour average air concentration for each HAP 
emitted from HON CMPUs at each facility with the lowest (i.e., most 
health protective) of the available acute reference values for that 
HAP. In this analysis, exposure estimates for 10 HAP exceeded at least 
one acute reference value for HON CMPUs in at least one facility. 
However, for eight of those HAP (acrylonitrile, benzene, chloroform, 
ethylene glycol, formaldehyde, methyl bromide, methyl chloride, and 
toluene) the estimated exceedances were only for no-effect reference 
values. All estimated exposures were lower than available

[[Page 34432]]

mild-effect reference values. Given the protective nature of these no-
effect reference values, and the fact that the estimated exposures to 
which they were compared are the highest expected for any 1-hour period 
in five years, we concluded that the eight HAP do not pose a 
significant health threat by acute inhalation.
    Estimated exposures to the other two HAP, acrolein and ethyl 
acrylate, exceeded a mild-effect reference value at a single facility 
with a HON CMPU. The estimated acrolein exposure of 100 micrograms per 
cubic meter ([mu]g/m\3\) exceeded the acute exposure guideline level of 
69 [mu]g/m\3\, and the estimated ethyl acrylate exposure of 50 [mu]g/
m\3\ exceeded the emergency response planning guideline value of 41 
[mu]g/m\3\. Both exposure estimates were well below corresponding 
reference values for more severe effects. Because these estimated 1-
hour exposures reflect the highest 1-hour concentrations near the 
facility in a 5-year period and would at worst cause only mild, 
reversible effects, EPA does not consider them to pose a significant 
health threat.
    For 15 HAP, no mild-effects reference values were available, and 
the lowest acute reference values for emergency planning uses are 
associated with severe health effects. For these HAP, the 1-hour 
exposure estimates were compared to these severe effects reference 
values. The highest acute HQ is 0.02, suggesting that these HAP also 
are very unlikely to pose health threats by acute inhalation exposure.
3. Multipathway Risks
    The lifetime cancer risk and noncancer adverse health impacts 
estimated to result from multipathway exposure are well below levels 
generally held to be of concern. Only two HAP emitted by HON CMPUs, 
hexachlorobenzene and anthracene, were estimated to pose any potential 
for exposures via routes beyond direct inhalation. The maximum cancer 
risk estimated for exposures to these HAP is 0.2-in-1 million. For 
noncancer impacts, the maximum HQ is 0.0004. From these low risk 
estimates, we concluded that multipathway risks do not pose a higher 
risk than inhalation exposure.
    As with human health impacts, all the ecological HQ values are well 
below levels of concern, with the highest HQ being 0.05 from benthic/
sediment exposure by aquatic life to anthracene. The highest HQ is 0.02 
from surface water exposure by aquatic life to hexachlorobenzene. We do 
not believe these levels are high enough to pose adverse environmental 
effects as defined in CAA section 112(a)(7).

D. What is our proposed decision on acceptable risk?

    Section 112(f)(2)(A) of the CAA states that if the MACT standards 
applicable to a category of sources emitting 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 * * * to less than 1-in-1 million, the Administrator 
shall promulgate [residual risk] standards * * * for such source 
category.'' Processes that would be subject to the proposed amendments 
under our first proposed option emit known, probable, and possible 
human carcinogens, and, as shown in table 1 of this preamble, we 
estimate that the maximum individual lifetime cancer risk (discussed 
below) associated with the standards of the 1994 HON is 100-in-1 
million. Since the maximum individual lifetime cancer risk is greater 
than 1 in a million, we are required to consider (residual risk) 
standards.
    As discussed in section IV.A of this preamble, we used a two-step 
process in establishing residual risk standards. The first step is the 
determination of acceptability (i.e., are the estimated risks due to 
emissions from these facilities ``acceptable''). This determination is 
based on health considerations only. 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'' (54 FR 38045, 
quoting the Vinyl Chloride decision at 824 F.2d 1165) recognizing that 
our world is not risk-free.
    In the 1989 Benzene NESHAP, we stated that a maximum individual 
lifetime cancer risk of approximately 100-in-1 million should 
ordinarily be the upper end of the range of acceptable risks associated 
with an individual lifetime cancer source of pollution. We discussed 
the maximum individual lifetime cancer risk 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.'' 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.'' 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.''
    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.'' Consequently, 
the presumptive risk level of 100-in-1 million provides a benchmark for 
judging the acceptability of maximum individual lifetime cancer risk, 
but does not constitute a rigid line for making that determination. In 
establishing a presumption for the acceptability of maximum risk, 
rather than a rigid line for acceptability, we explained in the 1989 
Benzene NESHAP that risk levels should also be weighed with a series of 
other health measures and factors, including the following:
     The numbers of persons exposed within each individual 
lifetime risk range and associated incidence within, typically, a 50 
kilometer (km) (about 30 miles) 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; and
     The overall incidence of cancer or other serious health 
effects within the exposed population.
    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.
    Based upon the criteria identified above, for purposes of both of 
our proposed options discussed below, we judge the level of risk of the 
current HON rule to be acceptable for this source category. The 
calculated maximum individual lifetime cancer risk associated with HON 
CMPUs is 100-in-1 million. There are no people with estimated risks 
greater than 100-in-1 million, which is the presumptively acceptable 
level of maximum individual lifetime cancer risk under the 1989 Benzene 
NESHAP criteria. The HON CMPUs at 32 facilities are estimated to pose 
risks of between 10 and 100-in-1 million, with 9,000 people estimated 
to be exposed in this risk range. The HON CMPUs at the remaining 206 
facilities are estimated to pose risks of 10-in-1 million or less. For 
the exposed population, total annual cancer incidence is estimated at 
0.1 cases per

[[Page 34433]]

year. In addition, significant non-cancer health effects are not 
expected. The HON CMPUs at only two of the 238 facilities are 
associated with an HI greater than 1, with less than 20 people 
estimated to be exposed at levels associated with an HI greater than 1.

E. What is our proposed decision on ample margin of safety?

    The second step in the residual risk decision framework is the 
determination of standards with corresponding risk levels that are 
equal to or lower than the acceptable risk level and that protect 
public health with an ample margin of safety. In making this 
determination, we considered the estimate of health risk and other 
health information along with additional factors relating to the 
appropriate level of control, including costs and economic impacts of 
controls, technological feasibility, uncertainties, and other relevant 
factors, consistent with the approach of the 1989 Benzene NESHAP.
    Many HON sites are located near other HON sites or other industrial 
sites, and people who live in these areas may be exposed to HAP emitted 
from multiple sources. We analyzed the effects of facility clusters on 
cancer risk levels by modeling all facilities with HON CMPUs that are 
located within 50 km of one another. The maximum individual lifetime 
cancer risk of clustered emissions was similar to the highest maximum 
individual lifetime cancer risk of a facility with a HON CMPU in that 
cluster. We concluded, therefore, that cluster effects have little or 
no significant effect on the risks to the individuals most exposed. The 
individuals potentially exposed to the highest risks would typically 
reside very near one of the facilities, and the resulting risk would be 
almost entirely caused by that closest facility. While these 
individuals may also be exposed to emissions from neighboring 
facilities, we found that the risks are sufficiently lower than the 
maximum risk posed by the nearby facility.
    Before developing our two general proposed options under sections 
112(f)(2) and 112(d)(6), we considered three regulatory alternatives 
for providing an ample margin of safety, assuming some degree of 
additional control is warranted. In developing the regulatory 
alternatives that assumed additional control is warranted, we wanted to 
target further emission reductions to the extent possible to reduce 
public health risks. Therefore, the alternatives were crafted to apply 
only at CMPUs that emit either carcinogenic HAP, or HAP that are not 
carcinogens but for which estimated exposure concentrations after 
application of MACT exceed chronic noncancer thresholds. Acrolein, 
methyl bromide, and maleic anhydride are the only three which exceed 
chronic noncancer thresholds. These 47 carcinogenic and three 
noncarcinogenic HAP are listed in proposed table 38 of 40 CFR, part 63, 
subpart G.
    We did not have sufficiently detailed information to analyze the 
possibility of controls on the various specific sources within a 
facility but outside the HON source category. Because the facilities in 
this source category also frequently have other non-HON processes we 
could not always associate the reported emissions from the NEI 
Assessment to a particular source category. As a result, we could not 
evaluate the existing levels of control or the potential for applying 
additional controls at the facilities where HAP emissions from non-HON 
processes contributed to the risk. Our position on the potential 
consideration of both source category-only emissions and facilitywide 
emissions is fully discussed in the final coke oven batteries NESHAP 
(70 FR 19996-19998, April 15, 2005).
    To develop possible regulatory alternatives, we first identified 
the additional control measures that could be applied at a specified 
cost to each of the five kinds of emission points regulated by the HON. 
The feasible control measures then were combined to develop the 
regulatory alternatives for assessing ample margin of safety. Control 
measures were defined in terms of both an emission control technology 
and the number of emission points controlled.
    The current HON standards for storage vessels, process vents, 
equipment leaks, wastewater collection and treatment operations, and 
transfer loading operations require the use of technologies such as 
thermal oxidizers, carbon adsorbers, and steam strippers to reduce HAP 
emissions by 95 to 98 percent. We did not identify any other 
technically feasible control technologies that would reduce HAP 
emissions beyond these levels.
    Consequently, to select control measures that would further reduce 
HAP emissions from HON CMPUs, we considered changing the applicability 
criteria to require control of uncontrolled emission points (i.e., 
certain Group 2 emission points under the original rule would become 
Group 1 emission points under the revised rule). For equipment leaks, 
we focused on reducing emissions from leaking valves in gas/vapor 
service and in light liquid service since these equipment components 
tend to have the highest emissions and, therefore, the greatest 
influence on risks from equipment leaks. Our evaluation of the feasible 
control measures for each of the five kinds of emission points is 
contained in memoranda in the public docket, and our proposed 
conclusions are summarized below.
1. Process Vent Control Measures
    To develop possible additional control measures for process vents, 
we applied the current level of control (i.e., reduce HAP emissions by 
98 percent) to the uncontrolled process vents reported in the ACC 
survey. For CMPUs that emit at least one HAP listed in table 38, each 
uncontrolled process vent emitting one or more of the HAP listed in the 
proposed table 38 of subpart G of part 63, we calculated a TRE index 
value, arrayed the TRE index values in ascending order (a higher TRE 
index value means higher control costs), and evaluated the emission 
reductions achieved by controlling each process vent. The TRE index 
value is a measure of the cost of applying a thermal oxidizer on a vent 
stream, based on vent HAP emissions, stream flow rate, net heating 
value, and corrosion properties (i.e., presence of halogenated 
compounds).
    The current HON rule requires 98 percent control of process vents 
with a TRE of 1.0 or less at existing process units (corresponding to a 
cost of approximately $3,000 per ton). The miscellaneous organic NESHAP 
(40 CFR part 63, subpart FFFF) also affects the chemical manufacturing 
industry and requires control of process vents with a TRE of 1.9 at 
existing sources and a TRE of 5.0 at new sources. A TRE of 5.0 
corresponds to a cost of approximately $15,000 per ton. In constructing 
a risk-based alternative for process vents containing table 38 HAP and 
considering control technology and cost, we analyzed impacts of further 
reducing table 38 HAP without exceeding the control level for the 
miscellaneous organic NESHAP (MON) for new sources (TRE of 5). We 
considered control of new and existing HON process vents with a TRE 
index value of 4.0 to be most reasonable.
    A TRE cut-off of 4.0 will reduce emissions of total HAP by 640 tpy 
at HON CMPUs at 14 out of 238 total facilities that emit table 38 HAP. 
The total capital cost would be $13 million with a total annualized 
cost of $3.7 million. A TRE cut-off of 4.0 will also reduce emissions 
of total volatile organic compounds (VOC) by 1,100 tpy at HON CMPUs at 
14 facilities that emit table 38 HAP. This control measure is included 
in our second proposed option

[[Page 34434]]

discussed below, but not in our first proposed option.
2. Storage Vessel Control Measures
    To develop possible additional control measures for storage 
vessels, we applied the current HON MACT level of control (95 percent 
reduction) to the uncontrolled tanks reported in the ACC survey. We 
calculated the HAP emission reduction and cost for installing an 
internal floating roof on existing fixed-roof vessels that contain any 
HAP listed in the proposed table 38 of subpart G of part 63. We sorted 
the storage vessels by decreasing emission reductions and determined 
the cost per ton of HAP removed of controlling each tank. To achieve 
emission reductions at the least cost, we selected a control measure 
with the same cost as the process vent control measure. We evaluated 
internal floating roofs on storage vessels with cost of approximately 
$12,000 per ton of total HAP reduced or less for any individual vessel. 
Since it is impracticable to develop a TRE for storage vessels, another 
parameter was needed to characterize storage vessels with a cost of 
$12,000 per ton removed. After analyzing the data, we expect that an 
emission cutoff of five tons of HAP per year will ensure that no 
individual storage vessel that contains a HAP from proposed table 38 of 
40 CFR, part 63, subpart G would incur a control cost that exceeds 
$12,000 per ton of HAP reduced. This emission cutoff would affect 7 out 
of 238 facilities and would reduce total HAP emissions by 120 tpy, at a 
total capital cost of $950,000 and a total annualized cost of $120,000. 
The average cost of controlling storage vessels at the 7 facilities 
would be $1,000 per ton of total HAP. The emission cut-off would also 
reduce emissions of VOC by 210 tpy.
3. Process Wastewater Control Measures
    To develop possible additional control measures for process 
wastewater streams, we applied the current HON MACT level of control 
(i.e., steam stripper with control of overhead gases) to the emissions 
from uncontrolled wastewater streams reported in the ACC survey. To 
estimate HAP emission reductions, the removal performance of the steam 
strippers was determined using the compound-specific fraction removed 
values specified in tables 8 and 9 of subpart G of the HON. The 
destruction of the overhead gases from the steam strippers was assumed 
to be 95 percent (the same performance that is required in the current 
HON standards). The estimated total HAP emission reduction for the ACC 
facilities for which wastewater data were available was 495 tons/year.
    While the ACC data contained sufficient information to estimate HAP 
emission reductions, flow rate data for individual streams, which is 
necessary to estimate control costs, were not available. To determine 
whether control of Group 2 wastewater streams would be feasible and 
whether additional data gathering would be warranted, we estimated cost 
per ton of HAP removed for each facility using the calculated HAP 
emission reductions and steam stripper cost estimates developed for 
model streams. The model streams were based upon comparable chemical 
manufacturing processes and wastewater HAP emissions data from 
rulemaking docket for the NESHAP for miscellaneous organic chemical 
manufacturing (40 CFR part 63, subpart FFFF). These data were grouped 
into HAP loading (kg/liter) ranges and default flow rates were 
estimated for each range. The default flow rates were assigned to 
wastewater streams for the facilities in the ACC survey data based upon 
the HAP loading for each stream.
    Based on this analysis, 96 percent of the facilities had cost per 
ton of HAP removed exceeding $12,000 per ton of total HAP reduced. The 
average cost per ton of HAP removed for controlling Group 2 wastewater 
streams was approximately $410,000 per ton of HAP reduced. Considering 
these high costs, we concluded that it is not reasonable to require 
additional controls for Group 2 wastewater streams, in light of the 
minimal risk reduction obtained if additional controls were to be 
imposed. As a result, additional controls for Group 2 wastewater 
streams are not included in either of our two proposed options 
discussed below.
4. Equipment Component Control Measures
    For leaking valves in gas/vapor service and in light liquid 
service, the possible additional control measures available to reduce 
HAP emissions are to either lower the leak definition, replace valves 
with leakless valves, or conduct more frequent monitoring by reducing 
the allowable percentage of leaking valves. We evaluated requiring 
replacement of existing valves in gas/vapor service and in light liquid 
service with leakless valves. However, we concluded that this method of 
control is not appropriate because it is extremely expensive. To 
implement this alternative, total industry capital costs would exceed 
$5.7 billion, and total annualized costs were calculated to be $780 
million. The alternative would reduce total HAP emissions by 1,800 tpy 
and total VOC emissions by 3,200 tpy. The average cost of total HAP 
removed of this control alternative would be $430,000 per ton of HAP.
    We also evaluated lowering the leak definition. Under Phase III of 
the current HON equipment leak standards, facilities are required to 
use a leak definition of 500 ppmv. However, we do not consider it 
appropriate to reduce the leak definition below the 500 ppmv level. We 
do not have any data that would indicate the emissions reduction or 
effectiveness in reducing risks associated with lowering the 
definition. Additionally, we do not have field data that validates that 
lower concentrations can be identified using Method 21.
    The final method we evaluated to reduce HAP emissions from leaking 
valves was to reduce the allowable percent of valve population that can 
leak. Under the current HON standards, facilities are allowed to 
conduct less frequent monitoring (quarterly, semiannually, annually) if 
the percentage of leaking valves is less than two percent, but must 
monitor more frequently (monthly) if the percentage of leaking valves 
is more than two percent.
    We evaluated requiring facilities to reduce the number of leaking 
valves in gas/vapor service and in light liquid service. Data supplied 
by the industry indicated that the average percent leaking valves at 
HON CMPUs is 0.5 percent. Requiring no more than 0.5 percent leakers 
would reduce total HAP emissions by 910 tpy, and total VOC emissions by 
1,600 tpy, from HON CMPUs at 174 facilities. The annual cost of 
requiring 0.5 percent leakers was calculated to be $9.7 million per 
year. This regulatory alternative would require no capital expenditures 
but would impose additional labor costs. The average cost per ton of 
total HAP removed of requiring 0.5 percent leakers is $11,000 per ton 
of HAP.
    We also evaluated requiring no more than 1.0 percent leakers. The 
total HAP emission reduction was estimated to be 420 tpy at an annual 
cost of $10 million per year. For less than five percent increase in 
annual cost, the 0.5-percent leak limit more than doubles the HAP 
reduction achieved by a 1.0-percent limit.
    Under this control measure, facilities would conduct monthly 
monitoring until the 0.5-percent limit is achieved. The monitoring 
frequency would be reduced to quarterly, semi-annually, or annually if 
successive monitoring periods show that facilities are able to maintain 
0.5 percent leakers or less. However, monthly monitoring would be 
required if the percent leakers exceeds 0.5 percent. While neither 
requiring

[[Page 34435]]

leakless equipment nor lowering the leak definition are included in 
either of our two proposed options discussed below, requiring 0.5 
percent leaking valves (or less) is included in our second proposed 
option, but not in our first proposed option.
5. Transfer Operation Control Measures
    We did not further evaluate controls for transfer operations 
because the HAP emissions remaining after compliance with the HON are 
very low. A total of 400 tpy of total HAP are emitted from controlled 
and uncontrolled transfer operations at HON sources, but only 200 tpy 
are from uncontrolled transfer operations. An additional 100 tpy are 
from transfer operations that did not specify whether they are 
controlled or uncontrolled. These emissions comprise less than three 
percent of total HAP emissions from all HON CMPUs, and less than one 
percent of the total risk from all HON CMPUs. Therefore, further 
control of transfer operations would provide no significant reduction 
of risk. The cost of controlling emissions from transfer operations 
ranges from approximately $10,000 per ton of HAP to over $100,000 per 
ton of HAP if there are already existing control devices that may be 
used to reduce emissions. If a new combustion device or vapor recovery 
device is also needed, the cost increases significantly. As a result, 
further controls for transfer operations are not included in either of 
our two proposed options discussed below.
6. Regulatory Alternatives
    The three regulatory alternatives are presented in table 2 of this 
preamble along with the associated costs and emission reductions. 
Alternative I would require control of storage vessels that store a HAP 
listed in the proposed table 38 of 40 CFR part 63 of subpart G and emit 
more than five tpy of HAP. Alternative II would require the same 
controls as Alternative I plus control of process vents that have a TRE 
index value less than or equal to 4.0 and emit one or more HAP listed 
in the proposed table 38 of 40 CFR part 63, subpart G. Alternative III 
would require the same controls as Alternative II plus the requirement 
to reduce the number of leaking valves in gas/vapor service and in 
light liquid service to less than 0.5 percent for valves that contain 
at least one HAP listed in proposed table 38 of 40 CFR part 63, subpart 
G. Table 3 of this preamble summarizes the risk reduction associated 
with each regulatory alternative.

                                  Table 2.--Impacts of Regulatory Alternatives
----------------------------------------------------------------------------------------------------------------
                                                    Total
                                                  installed      Total      Total HAP     Average    Incremental
       Alt.           Control  requirement\*\      capital     annualized    emission     cost per     cost per
                                                  costs  ($     cost  ($    reduction    ton of HAP   ton of HAP
                                                   million)     million)      (tpy)       ($/ton)      ($/ton)
----------------------------------------------------------------------------------------------------------------
I.................  Reduce HAP emissions by 95             1         0.12          120        1,000
                     percent from storage
                     vessels that emit greater
                     than 5 tons per year of
                     HAP.
II................  Same as Alternative I plus            14            4          800        5,000        5,700
                     reduce HAP emissions by 98
                     percent from process vents
                     with a TRE value less than
                     or equal to 4.0.
III...............  Same as Alternative II plus           14           13        1,700        7,600      10,000
                     conduct monthly monitoring
                     of process unit valves
                     until the process unit has
                     fewer than 0.5 percent
                     leaking valves in gas/
                     vapor and in light liquid
                     service.
----------------------------------------------------------------------------------------------------------------
\*\ Applies to units that emit HAP listed in proposed table 38 of 40 CFR 63, subpart G.

                                Table 3.--Risk Impacts of Regulatory Alternatives
----------------------------------------------------------------------------------------------------------------
                                                                     Regulatory alternative
                  Parameter                   ------------------------------------------------------------------
                                                     Base              I                II              III
----------------------------------------------------------------------------------------------------------------
Risk to most exposed individual:
     Cancer (in a million)...................            100              100              100             60
    \*\ Noncancer (H1).......................              1                1                0.9            0.9
Size of population at cancer risk:
    >100-in-1 million........................              0                0                0              0
    >10-in-1 million.........................          9,000            9,000            9,000          7,000
    >1-in-1 million..........................      1,950,000        1,900,000        1,900,000      1,500,000
Number of plants at cancer risk level:
    >100-in-1 million........................              0                0                0              0
    >10-in-1 million.........................             32               32               32             32
    >1-in-1 million..........................            117              117              117            112
\*\ Population with HI >1....................             20               20                0              0
\*\ No. of Plants with HI >1.................              2                2                0              0
Cancer incidence.............................              0.1              0.1              0.1            0.09
Cancer incidence reduction (percent).........  ...............              2                2             10
HAP emission reduction (percent).............  ...............              1                6            13
----------------------------------------------------------------------------------------------------------------
\*\ If the HI is calculated to be less than 1, then no adverse health effects are expected as a result of the
  exposure. However, an HI exceeding 1 does not translate to a probability that adverse effects occur. Rather,
  it suggests the possibility that adverse health effects may occur.

7. Regulatory Decision for Residual Risk
    Based on the information analyzed for the regulatory alternatives, 
we are proposing two options for our rulemaking on whether to establish 
additional emissions standards to protect public health with an ample 
margin of safety. The first proposed option is to maintain the current 
level of control in the HON (i.e., the baseline option in table 2 of 
this preamble) with no further modifications. The second proposed 
option corresponds to Regulatory Alternative III. In the final rule, we 
expect to select one of these

[[Page 34436]]

options, with appropriate modifications in response to public comments.
a. Rationale for Option 1
    For the first option of the proposed rulemaking, we are proposing 
to make no changes to the current HON rule, instead proposing to find 
that the current level of control called for by the existing MACT 
standard represents both an acceptable level of risk (the cancer risk 
to the most exposed individual is approximately 100-in-1 million) and 
provides public health protection with an ample margin of safety. This 
proposed finding is based on considering the additional costs of 
further control (as represented by Option 2 [Regulatory Alternative 
III]) against the relatively small reductions in health risks that are 
achieved by that alternative.
    The Agency would conclude under this proposal that the $13 million 
per year cost of Regulatory Option III would be unreasonable given the 
minor associated improvements in health risks. Baseline cancer 
incidence under the current HON rule is estimated at 0.1 cases per 
year. Proposed Option 2 would reduce incidence by about 0.01 cases per 
year. Statistically, this level of risk reduction means that Option 2 
would prevent 1 cancer case every 100 years. Accordingly, the cost of 
this option could be considered to be disproportionate to the level of 
incidence reduction achieved. In addition, the Agency proposes to 
conclude that the changes in the distribution of risks reflected in 
table 3 of this preamble (i.e., the maximum individual cancer risk is 
reduced by 40 percent to 60 in a million, 450,000 people's cancer risks 
are shifted to levels below 1 in a million, and 20 people's noncancer 
Hazard Index values would be reduced from above to below 1) are do not 
warrant the costs. This change in the distribution of risk, that is, 
the aggregate change in risk across an affected population of more than 
one in a million reduces cancer risk by 0.01 cancers per year (i.e., 
one cancer across this population every on hundred years). 
Consequently, under Option 1 we are proposing that it is not necessary 
to impose any additional controls on the industry to provide an ample 
margin of safety to protect public health. Compared to Option 2, the 
rationale for Option 1 reflects a relatively greater emphasis on 
considering changes in cancer incidence in determining what is 
necessary to protect public health with an ample margin of safety and 
correspondingly less emphasis on maximizing the total number of people 
exposed to lifetime cancer risks below 1-in a million.
b. Rationale for Option 2
    For the second option, we are proposing that Regulatory Alternative 
III provides an ample margin of safety to protect public health. This 
option reduces HAP emissions and risks beyond the current MACT standard 
using controls that are technically and economically feasible and that 
pose no adverse environmental impacts. The controls will reduce cancer 
risks to the most exposed individual by about 40 percent to 60 in a 
million. Exposures for approximately 450,000 people will be reduced 
from above the 1 in a million cancer risk level to below 1 in a million 
cancer risk level, and no individual will be exposed to a noncancer HI 
greater than 1. Note that these changes would reduce cancer incidence 
by 0.01 cases per year (i.e., prevent one cancer case every hundred 
years). The rationale for this option reflects a relatively greater 
emphasis on maximizing the total number of people exposed to lifetime 
cancer risks below 1 in a million, compared to that in Option 1, while 
reflecting correspondingly less emphasis on various other public health 
metrics such as incidence reduction.
    The annualized cost of Option 2 is $13 million. Our economic 
analysis (summarized later in this preamble) indicates that this cost 
will have little impact on the price and output of chemical and 
petroleum feedstocks. However, the Agency is considering the adoption 
of an approach, described elsewhere in this preamble, to allow sources 
to avoid additional controls if they can demonstrate that the risks 
posed by their HAP emissions already fall below certain low-risk 
thresholds. Depending on the public comments received, we may include 
this approach in the final rule, and this could result in some cost 
saving at individual facilities. We did not include this potential cost 
savings in our control cost calculations. It should be noted that the 
avoidance of controls would also result in fewer incidence and VOC 
reductions than those estimated above.

Discussion of Other Factors

    Besides HAP emission reductions, the second option (Regulatory 
Alternative III) would reduce emissions of VOC by 2,900 tpy. Reducing 
VOC provides the added benefit of reducing ambient concentrations of 
ozone and may reduce fine particulate matter. We have not estimated the 
benefits of these reductions but previous work suggests that the ozone 
benefits per ton of VOC removed would span a large range, rarely 
exceeding $1000 to $2000 per ton. The cost of this option translates 
into about $4,300 per ton of VOC removed.
    While we believe that the risk assessment for this proposal is 
appropriate for rulemaking purposes, we recognize that there are a 
variety of uncertainties in the underlying models and data. These 
include the uncertainties associated with the cancer potency values (of 
the 52 HAP identified as ``carcinogens'', EPA classifies only four as 
``known carcinogens,'' while the remaining carcinogens are classified 
as either ``probable'' or ``possible'' carcinogens (using the 1986 
nomenclature)), reference concentrations, uncertainties underlying 
emissions data, emissions dispersion modeling in the ISCST3 model, and 
the human behavior modeling (including assumptions of exposure for 24 
hours a day for 70 years). One source of uncertainty is the reliance on 
industry-supplied data that represent only a segment of the industry. 
These data were not collected under the information collection 
authority of section 114 of the CAA, but were the result of a voluntary 
survey conducted by the industry trade association. It is unclear what 
bias may exist in the data or the extent to which the 104 facilities in 
the survey are representative of the maximum risks posed by the 
remaining 134 facilities. Another source of potential uncertainty is 
the use of data based on actual HAP emissions, rather than the maximum 
allowable emissions under the current HON rule (which, as explained 
above, are unknown and impossible to determine). An additional source 
of uncertainty comes from our use of 1999 year emissions inventories. 
Some HON facilities may have reduced their emissions since then to 
comply with other CAA and state requirements; others may have increased 
their emissions as a result of growth.

F. What is EPA proposing pursuant to CAA section 112(d)(6)?

    Section 112(d)(6) of the CAA requires us to review and revise MACT 
standards, as necessary, every 8 years, taking into account 
developments in practices, processes, and control technologies that 
have occurred during that time. This authority provides us with broad 
discretion to revise the MACT standards as we determine necessary, and 
to account for a wide range of relevant factors.
    We do not interpret CAA section 112(d)6) as requiring another 
analysis of MACT floors for existing and new sources. Rather, we 
interpret the provision as essentially requiring us to

[[Page 34437]]

consider developments in pollution control in the industry (``taking 
into account developments in practices, processes, and control 
technologies''), and assessing the costs of potentially stricter 
standards reflecting those developments (69 FR 48351). As the U.S. 
Court of Appeals for the DC Circuit has found regarding similar 
statutory provisions directing EPA to reach conclusions after 
considering various enumerated factors, we read this provision as 
providing EPA with substantial latitude in weighing these factors and 
arriving at an appropriate balance in revising our standards. This 
discretion also provides us with substantial flexibility in choosing 
how to apply modified standards, if necessary, to the affected 
industry.
    We took comment in two recently proposed residual risk rules on 
whether, when we make a low-risk finding under section 112(f) (as would 
occur under the first option proposed today), and ``barring any 
unforeseeable circumstances which might substantially change this 
source category or its emissions,'' we would need to conduct future 
technology reviews under CAA section 112(d)(6). See Proposed Rule: 
Magnetic Tape Manufacturing Operations, 70 FR 61417 (October 24, 2005); 
Proposed Rule: Industrial Process Cooling Towers, 70 FR 61411 (October 
24, 2005). Earlier, in the final residual risk rule for Coke Ovens, we 
discussed the relationship between the findings underlying a section 
112(f) determination and section 112(d)(6) revisions. National Emission 
Standards for Coke Oven Batteries, 70 FR 19992, 20009 (April 15, 2005). 
Today we further elaborate on how we expect we would address the need 
for future reviews under certain circumstances, and we refine our 
position regarding when revisions may be likely under section 
112(d)(6). First, the Agency now interprets the language of section 
112(d)(6) as being clear in requiring a periodic review no less 
frequently than every 8 years. We also believe that the periodic review 
should be of whatever section 112 standard applies to the relevant 
source category, regardless of whether the original section 112(d) and/
or 112(h) NESHAP has, or has not, been revised pursuant to section 
112(f)(2). We recognize that one could read the section 112(f)(2) 
language to authorize EPA's setting a standard under subsection (f)(2) 
separate from the NESHAP standard set under subsections (d) and/or (h). 
Following this reading, one might argue that any review under (d)(6) 
should be only of the (d)(2), (d)(4), or (d)(5) NESHAP standard, as 
applicable. It is our position, however, that the better reading of 
(f)(2) allows EPA to revise the relevant subsection (d) standard if the 
agency determines residual risk so justifies under (f)(2); indeed, our 
practice has been to follow this approach. See Coke Ovens, 70 FR 19993; 
40 CFR 63.300-.311. This approach results in clearer and more effective 
implementation because only one part 63 NESHAP would apply to the 
source category, and is supported by the fact that section 112(d)(6) 
refers to ``emission standards promulgated under this section'' 
(emphasis added), as opposed to ``subsection,'' in defining the scope 
of EPA's authority to review and revise standards.
    Although the language of section 112(d)(6) is nondiscretionary 
regarding periodic review, it grants EPA much discretion to revise the 
standards ``as necessary.'' Thus, although the specifically enumerated 
factors that EPA should consider all relate to technology (e.g., 
developments in practices, processes and control technologies), the 
instruction to revise ``as necessary'' indicates that EPA is to 
exercise its judgment in this regulatory decision, and is not precluded 
from considering additional relevant factors, such as costs and risk. 
EPA has substantial discretion in weighing all of the relevant factors 
in arriving at the best balance of costs and emissions reduction and 
determining what further controls, if any, are necessary. This 
interpretation is consistent with numerous rulings by the U.S. Court of 
Appeals for the DC Circuit regarding EPA's approach to weighing similar 
enumerated factors under statutory provisions directing the agency to 
issue technology-based standards. See, e.g. Husqvarna AB, v. EPA, 254 
F.3d 195 (DC Cir. 2001).
    For example, when a section 112(d)(2) MACT standard alone obtains 
protection of public health with an ample margin of safety and prevents 
adverse environmental effects, it is unlikely that it would be 
``necessary'' to revise the standard further, regardless of possible 
developments in control options.\3\ Thus, the section 112(d)(6) review 
would not need to entail a robust technology assessment.
---------------------------------------------------------------------------

    \3\ Although, as discussed below, EPA might still consider 
developments that could be substantially reduce or eliminate risk in 
a cost-effective manner.
---------------------------------------------------------------------------

    Two additional possible circumstances involving step 2 of the 
benzene analysis also could lead to a similar result. First, if, under 
step 2 of the benzene analysis, the ample margin of safety 
determination that resulted in lifetime cancer risks above 1-in-1 
million based on emissions after implementation of the (d)(2) MACT 
standard was not founded at all on the availability or cost of 
particular control technologies and there was no issue regarding 
adverse environmental effect or health effects, and the facts 
supporting those analyses (e.g., the public health and environmental 
risk) remain the same, it is unlikely that advances in air pollution 
control technology alone would cause us to revise the NESHAP because 
the existing regulations would continue to assure an adequate level of 
safety and protection of public health and prevention of adverse 
environmental effects.
    Second, if, under step 2, we determined that additional controls 
were appropriate for ensuring an ample margin of safety and/or to 
prevent adverse environmental effects, and the revised standards 
resulted in remaining lifetime cancer risk for non-threshold pollutants 
falling below 1-in-1 million and for threshold pollutants falling below 
a similar threshold of safety and prevented adverse environmental 
effect, and the facts supporting those analyses (e.g., the 
environmental and public health risks) remain the same, then it is 
unlikely that further revision would be needed. As stated above, under 
these circumstances we would probably not require additional emission 
reductions for a source category despite the existence of new or 
cheaper technology or control strategies, the exception possibly being 
the development of cost-effective technology that would greatly reduce 
or essentially eliminate the use or emission of a HAP. Therefore, in 
these situations, a robust technology assessment as part of a review 
under section 112(d)(6) may not be warranted.
    Note that the circumstances discussed above presume that the facts 
surrounding the ample margin of safety and environmental analyses have 
not significantly changed. If there have been significant changes to 
fundamental aspects of the risk assessment then subsequent section 
112(d)(6) reviews with robust technology assessments (and relevant risk 
considerations) may be appropriate.
    Finally, if the availability and/or costs of technology were part 
of either the rationale for an ample margin of safety determination 
that resulted in lifetime cancer risk for non-threshold pollutants 
above 1-in-1 million (or for threshold pollutants falling below a 
similar threshold of safety) or affected the decision of whether to 
prevent adverse environmental effect, it is reasonable to conclude that 
changes in those costs or in the availability of technology could alter 
our conclusions, even if risk factors (e.g., emissions profiles, RfC, 
impacts on

[[Page 34438]]

listed species) remained the same. Under these circumstances, 
subsequent section 112(d)(6) reviews with robust technology assessments 
(and relevant risk considerations) would be appropriate.
    For HON process vents, storage vessels, process wastewater, and 
transfer operations, we are not aware of advances in control techniques 
that would achieve greater HAP emission reductions than the control 
technologies that are used to comply with the current HON rule. These 
technologies reduce HAP emissions by 95 to 98 percent for the various 
regulated emission points. The only feasible options for additional 
control would be to apply the existing HON reference technologies to 
some Group 2 emission points that are not required to be controlled by 
the current rule.
    For equipment leaks, leakless components could be installed to 
reduce emissions from process equipment. Leakless components were 
considered during the development of the current rule and were 
determined not to represent MACT because of the high cost of replacing 
thousands of equipment components and concern that equipment was not 
available for all applications. The cost of leakless components has not 
substantially declined since the promulgation of the current rule. 
Therefore, we still consider the cost of leakless components to be 
infeasible for broad application throughout the industry.
    Accordingly, for the section 112(d)(6) review, we considered the 
same regulatory alternatives described above for residual risk (table 2 
of this preamble). Based on the information analyzed for the regulatory 
alternatives, we are proposing two options for emissions standards to 
satisfy the requirements of section 112(d)(6) review. The first 
proposed option is to maintain the current level of control in the HON 
(i.e., the baseline option in table 3 of this preamble) with no further 
modifications, tracking the first proposed option for residual risk. 
The second proposed option corresponds to our second proposed option 
under our residual risk analysis and proposes the additional control 
requirements of Regulatory Alternative III. In the final rule, we 
expect to select one of these options, with appropriate modifications 
in response to public comments.
1. Rationale for Option 1
    Under the first option we are proposing to make no changes to the 
current HON rule under our section 112(d)(6) authority. Section 
112(d)(6)requires us to revise the NESHAP ``* * * as necessary (taking 
into account developments in practices, processes, and control 
technologies) * * *'' Our review found no new or improved control 
technologies or practices for reducing HAP emissions beyond the 
controls that are required by the current rule. Control costs have not 
declined significantly. We found no changes in industry production 
processes or practices that would lead to increased HAP emissions from 
HON processes.
    Whether or not it is necessary to revise the current rule, 
therefore, depends on the benefits of imposing additional emission 
reductions and the associated cost. Option 2 would extend the 
applicability of the current HON control requirements to some emission 
points that currently are not subject to control requirements and would 
require more frequent monitoring of equipment leaks. These emission 
reductions would reduce cancer incidence by about 0.01 cases per year 
and reduce the HI below 1 for about 20 individuals. Because these 
controls would not reduce these particular factors significantly, 
Option 1 proposes that the additional control costs are not necessary 
under section 112(d)(6).
2. Rationale for Option 2
    By requiring additional control of storage vessels, process vents, 
and equipment leaks, Option 2 (i.e., Regulatory Alternative III) would 
reduce total HAP emissions by 1,700 tons/year. The capital costs are 
estimated at $14 million with annualized costs of $13 million. The 
second option has an average cost per ton of HAP of about $8,000 per 
ton HAP removed and an incremental cost per ton of HAP of $10,000 per 
ton HAP removed. Option 2 would satisfy the requirements of section 
112(d)(6) because the controls have been demonstrated in practice and 
can be implemented at an annual cost of $13 million with no adverse 
energy or non-air environmental impacts. In addition, this second 
option would reduce the total number of people exposed to maximum 
lifetime cancer risks of at least 1-in-1 million by 450,000 and reduce 
cancer incidence by 0.01 cases per year (an average of one case every 
one hundred years). This option would apply controls only to CMPUs that 
emit HAP listed in table 38 of the proposed rule. We estimate that 
CMPUs that emit HAP not on table 38 of the proposed rule pose such low 
risk (i.e., the current HON rule already protects public health with an 
ample margin of safety for these pollutants) that imposing any 
additional cost beyond the original MACT controls would not be 
necessary. These units pose no cancer risk, no significant noncancer 
risk, and no adverse ecological risks.

IV. Solicitation of Public Comments

A. Introduction and General Solicitation

    We request comments on all aspects of the proposed rulemaking. All 
significant comments received during the public comment period will be 
considered in the development and selection of the final rulemaking.

B. Specific Comment and Data Solicitations

    In addition to general comments on the proposed options (and, for 
Option 2, the proposed revised standards), we particularly request 
comments and data on the following issues:
1. Format of Control Alternatives
    We request comment on the format of the proposed standards under 
Option 2 (i.e., Regulatory Alternative III). We structured regulatory 
alternatives to build on the emission and risk reductions obtained by 
controlling storage vessels, process vents, and equipment leaks. The 
regulatory alternatives could have been structured differently (e.g., 
as singular alternatives considering risk). We are requesting comments 
on other possible combinations of the proposed standards.
2. ``Low-risk'' Alternative Compliance Approach
    We request comment on whether the final rule should incorporate a 
``Low-risk'' approach that would allow a facility to demonstrate that 
the risks posed by HAP emissions from the HON affected sources (storage 
vessels, process vents, process wastewater, transfer operations, and 
equipment leaks) are below certain health effects thresholds. If 
sources demonstrate that risks are below these levels, then the 
requirements of proposed Option 2, if finalized, would not apply to 
them. Possible models for health-based approaches to use for HON 
sources are contained in 40 CFR part 63, subparts DDDD (Plywood and 
Composite Wood Products Manufacture NESHAP) and DDDDD (Industrial/
Commercial/Institutional Boilers and Process Heaters NESHAP).
    Each facility that would choose to use the ``Low-risk'' approach 
would be required to determine maximum hourly emissions under worst-
case operations and conduct a site-specific risk assessment that 
demonstrates that the HON CMPUs at the facility do not cause a maximum 
individual lifetime cancer risk exceeding 1-in-1 million, an HI

[[Page 34439]]

greater than 1, or any adverse environmental impacts.
    For the risk assessment, facilities would be allowed to use any 
scientifically-accepted, peer-reviewed risk assessment methodology. An 
example of one approach for performing a site-specific compliance 
demonstration for air toxics can be found in the EPA's ``Air Toxics 
Risk Assessment Reference Library, Volume 2, Site-Specific Risk 
Assessment Technical Resource Document'', which may be obtained through 
the EPA's Air Toxics Web site at http://www.epa.gov/ttn/fera/risk_atoxic.html
.

    At a minimum, the site-specific alternative compliance 
demonstration would have to:
     Estimate long-term inhalation exposures through the 
estimation of annual or multi-year average ambient concentrations;
     Estimate the inhalation exposure for the individual most 
exposed to the facility's emissions;
     Use site-specific, quality-assured data wherever possible;
     Use health-protective default assumptions wherever site-
specific data are not available, and;
     Document adequately the data and methods used for the 
assessment so that it is transparent and can be reproduced by an 
experienced risk assessor and emissions measurement expert.
    To ensure compliance with the ``Low-risk'' alternative compliance 
demonstration, emission rates from the approved demonstration would be 
required to be included the facility's Title V permit as Federally 
enforceable emission limits. EPA requests comment on the possible means 
for approving such demonstrations (e.g., by EPA affirmative review, by 
the State permitting authority, by EPA audit, by third-party, or by 
self-certification plus EPA audit), and on the risk thresholds that 
would be used for the basis of compliance demonstration. We are also 
requesting comment on the method of peer review for the site-specific 
risk assessments. We also request comment on the legal authority for 
such an approach, under sections 112(f)(2) and 112(d)(6), of tailoring 
the further emissions reduction requirement to apply only where it is 
specifically necessary to reduce risks to levels that assure public 
health is protected with an ample margin of safety.
3. Gas Imaging Equipment
    The HON currently requires that emissions from leaking equipment be 
controlled using a leak detect and repair program (LDAR). The primary 
work practice currently employed to detect leaking equipment requires 
the use of a portable instrument to detect leaks of VOC or HAP at the 
leak interface of the equipment component. The instrument must meet the 
performance specifications of EPA Reference Method 21.
    Under section 112(d)(6) of the CAA, EPA has the general authority 
to review and amend its regulations as appropriate and to provide 
additional work practice alternatives as new technology becomes 
available. In recent years, a new technology, known as gas imaging, has 
been developed that could be used to detect leaking components. The 
effective use of gas imaging technology may significantly reduce the 
costs of LDAR programs because owners or operators will be able to 
reduce the time necessary to monitor a component. The technology may 
also allow the identification of larger leaks more quickly than Method 
21, thereby, allowing them to be repaired quicker, and ultimately 
decrease emissions.
    Currently available gas imaging technologies fall into two general 
classes: active and passive. The active type uses a laser beam that is 
reflected by the background. The attenuation of the laser beam due to 
passing through a hydrocarbon cloud provides the optical image. The 
passive type uses ambient illumination to detect the difference in heat 
radiance of the hydrocarbon cloud.
    The principle of operation of the active system is the production 
of an optical image by reflected (backscattered) laser light, where the 
laser wavelength is such that it is absorbed by the gas of interest. 
The system would illuminate the process unit with infrared light and a 
video camera-type scanner picks up the backscattered infrared light. 
The camera converts this backscattered infrared light to an electronic 
signal, which is displayed in real-time as an image. Since the scanner 
is only sensitive to illumination from the infrared light source and 
not the sun, the camera is capable of displaying an image in either day 
or night conditions.
    The passive instrument has a tuned optical lens, which is in some 
respects like ``night-vision'' glasses. It selects and displays a video 
image of light of a particular frequency range and filters out the 
light outside of that frequency range. In one design, by superimposing 
the filtered light (at a frequency that displays VOC gas) on a normal 
video screen, the instrument (or camera) displays the VOC cloud in real 
time in relationship to the surrounding process equipment. The operator 
can see a plume of VOC gas emanating from a leak.
    We are requesting comment on the appropriateness of allowing gas 
imaging technology as an alternative work practice for identifying 
leaking components. While gas imaging may be applicable to monitor 
leaking components at many source categories, we are specifically 
requesting comment on the application of gas imaging technology to 
CPMUs regulated by the HON.
4. Monitoring, Applicability, Implementation, and Compliance
    Based on issues which have arisen over the past 14 years through 
inspections, requests for clarification, and discussions with industry, 
EPA has identified the following areas for which we solicit comments 
relating to monitoring, applicability, implementation, and compliance 
with the rule.
    Liquid Streams from Control Devices: The EPA is clarifying that 
liquid streams generated from control devices (e.g., scrubber effluent) 
are wastewater. Since the concept of wastewater does not exist until 
the point of determination (i.e., where the liquid stream exits the 
CMPU), and a control device (e.g., scrubber) is not specifically 
defined as part of the CMPU as a control device, there is an 
inconsistent understanding in the industry as to whether wastewater 
provisions apply.
    Non-continuous Gas Streams from Continuous Operations: The EPA is 
clarifying that non-continuous vents from continuous HON unit 
operations (i.e., reactors, distillation units, and air oxidation 
units) are subject to the HON if they are generated during the course 
of startup, shutdown, or malfunction. These are currently not 
specifically defined by either the HON or the MON since they are 
generated from continuous operations and are not batch process vents as 
defined in 40 CFR 63.101 or covered by 40 CFR 63.100(j)(4).
    Boiler Requirements versus Fuel Gas System Requirements: The EPA 
solicits comment as to whether the need exists to have exclusions for 
boilers and exclusions for fuel gas systems. The EPA also proposes to 
include monitoring provisions and/or certifications that the boilers 
are compliant.
    Group Status Changes for Wastewater: The Agency proposes to include 
language similar to 40 CFR 63.115(e), which requires a redetermination 
of TRE of process vents if process or operational changes occur for 
wastewater. Although Sec.  63.100(m)

[[Page 34440]]

generally applies to Group 2 wastewater streams becoming Group 1, 
explicit language similar to Sec.  63.115(e) that would require 
redetermination of group status for wastewater does not exist.
    Leaking Components Found Outside of Regularly Scheduled Monitoring 
Periods: On October 12, 2004, the EPA issued a formal determination to 
Louisiana Department of Environmental Quality clarifying that subpart H 
of the HON requires that leaks found outside of the regularly scheduled 
monitoring period must be repaired, recorded, and reported as leaking 
components. The EPA proposes to incorporate clarifying edits to subpart 
H to make this explicit in the regulation.
    Redetermination of Primary Product: Unlike other rules, such as the 
NESHAP for Polymers and Resins IV (40 CFR part 63, subpart JJJ), the 
HON does not have specific provisions for performing a periodic 
redetermination for a primary product. The EPA has issued formal 
applicability determinations for site specific situations clarifying 
that, at the point that a facility meets the applicability of the rule, 
they would be subject to the rule regardless of the lack of specific 
provisions for periodic redeterminations. The EPA proposes to codify 
procedures and compliance schedules for flexible operating units which 
have a change in primary product. The EPA intends to model the HON 
provisions after the NESHAP for Polymers and Resins IV which requires 
annual redetermination of a primary product for equipment which is not 
originally designated as part of a HON CMPU, but which produces HON 
products. Therefore, compliance with the HON for a flexible operating 
unit which previously produced a non-HON primary product would be 
required to be in compliance with the HON immediately upon 
determination that the primary product is a HON product.
    Common Recovery Devices for Wastewater: The EPA clarifies that 
liquid streams routed to a recovery device receiving streams from 
multiple CMPU's would be wastewater. Under the HON, the concept of 
recovery is tied integrally to a specific CMPU. Additionally, a common 
recovery device serving multiple CMPU's would, by definition, be 
outside the CMPU. Therefore, streams routed to it would be considered 
wastewater discharged from the CMPU.
    Net Positive Heating Value: The EPA proposes to define ``net 
positive heating value'' to incorporate the concept that, for fuel 
value, the stream must provide useful energy by using less energy to 
combust and produce a stable flame than would be derived from it. This 
difference must have a positive value when used in the context of 
``recovering chemicals for fuel value'' (e.g., in the definition of 
``recovery device'').
    Pressure Testing for Equipment Leaks: Based on field inspections, 
the Agency has found a poor correlation between the results of batch 
pressure testing and Method 21 results. It has been the Agency's 
experience that high leak rates are found by Method 21 results on 
components which routinely pass either a gas or liquid pressure test. 
Additionally, the annual pressure test frequency does not adequately 
address leaking components which are not otherwise disturbed and 
required to be tested on a more frequent basis. The Agency proposes to 
change the frequency of the pressure testing to quarterly and 
supplement the pressure tests with a statistical sample of Method 21 
results.

V. Statutory and Executive Order Reviews

    Because this notice proposes two options for rulemaking, the 
analysis conducted and determinations made in this section of the 
preamble are based on the option with the higher cost and regulatory 
burden.

A. Executive Order 12866: Regulatory Planning and Review

    Under E.O. 12866 (58 FR 51735, October 4, 1993), EPA must determine 
whether the regulatory action is ``significant,'' and therefore, 
subject to review by the Office of Management and Budget (OMB) and the 
requirements of the E.O. The E.O. defines a ``significant regulatory 
action'' as one that is likely to result in a rule that may:
    (1) Have an annual effect on the economy of $100 million or more, 
or adversely affect in a material way the economy, a sector of the 
economy, productivity, competition, jobs, the environment, public 
health or safety, or State, local, or tribal governments or 
communities;
    (2) Create a serious inconsistency or otherwise interfere with an 
action taken or planned by another agency;
    (3) Materially alter the budgetary impact of entitlements, grants, 
user fees, or loan programs or the rights and obligations of recipients 
thereof; or
    (4) Raise novel legal or policy issues arising out of legal 
mandates, the President's priorities, or the principles set forth in 
the E.O.
    An economic impact analysis was performed to estimate changes in 
prices and output for affected HON sources and their consumers using 
the annual compliance costs estimated for proposed Option 2. This 
option would impose the highest costs of the alternatives considered. 
All estimates are for the fifth year after promulgation.
    The price increases from the market reactions to the HON compliance 
costs are less than 0.02 percent, and the output changes are less than 
0.01 percent. The affected output in this case includes major chemical 
and petroleum feedstocks for use in major chemical and refinery 
production. The small reductions in price and output reflect the 
relatively low cost of the proposal relative to the size of the 
affected industries. The overall annual social costs, which reflect 
changes in consumer and producer behavior in response to the compliance 
costs, are $3.77 million (2004 dollars). For more information, refer to 
the economic impact analysis report that is in the public docket for 
this rule.
    Pursuant to the terms of E.O. 12866, this proposed rule has been 
determined to be a ``significant regulatory action'' because it raises 
novel legal and policy issues. The EPA has submitted this action to OMB 
for review. Changes made in response to OMB suggestions or 
recommendations will be documented in the public record.

B. Paperwork Reduction Act

    The information collection requirements in this proposed rule have 
been submitted for approval to the Office of Management and Budget 
(OMB) under the Paperwork Reduction Act, 44 U.S.C. 3501, et seq. An 
Information Collection Request (ICR) document prepared by EPA has been 
assigned EPA ICR number 2222.01 and OMB Control Number XXXX-XXXX.
    The ICR estimates the increased burden to industry that results 
from the proposed standards. Burden means the total time, effort, or 
financial resources expended by persons to generate, maintain, retain, 
or disclose or provide information to or for a Federal agency. This 
includes the time needed to review instructions; develop, acquire, 
install, and utilize technology and systems for the purpose of 
collecting, validating, and verifying information, processing and 
maintaining information, and disclosing and providing information; 
adjust the existing ways to comply with any previously applicable 
instructions and requirements; train personnel to respond to a 
collection of information; search data sources; complete and review the 
collection of information; and transmit or otherwise disclose the 
information.
    For this rule, the increased burden is associated with developing 
and maintaining Group 2 storage vessel emission determinations and TRE

[[Page 34441]]

determinations for Group 2 process vents, and recording and maintaining 
equipment leak information. The projected hour burden is 4,500 hours at 
a cost of $104,000.
    An Agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for EPA's 
regulations in 40 CFR part 63 are listed in 40 CFR part 9.
    To comment on the Agency's need for this information, the accuracy 
of the provided burden estimate, and any suggested method for 
minimizing respondent burden, including the use of automated collection 
techniques, EPA has established a public docket for this rule, which 
includes this ICR, under Docket ID number EPA-HQ-OAR-2005-0475. Submit 
any comments related to the ICR for this proposed rule to EPA and OMB. 
See ADDRESSES section at the beginning of this notice for where to 
submit comments to EPA. Send comments to OMB at the Office of 
Information and Regulatory Affairs, Office of Management and Budget, 
725 17th Street, NW., Washington, DC 20503, Attention: Desk Office for 
EPA. Since OMB is required to make a decision concerning the ICR 
between 30 and 60 days after June 14, 2006, a comment to OMB is best 
assured of having its full effect if OMB receives it by July 14, 2006. 
The final rule will respond to any OMB or public comments on the 
information collection requirements contained in this notice.

C. Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) generally requires an agency 
to prepare a regulatory flexibility analysis of any rule subject to 
notice and comment rulemaking requirements under the Administrative 
Procedure Act or any other statute unless the agency certifies that the 
proposed rule will not have a significant economic impact on a 
substantial number of small entities. Small entities include small 
businesses, small organizations, and small governmental jurisdictions.
    For the purposes of assessing the impacts of the proposed rule on 
small entities, small entity is defined as, (1) a small business as 
defined by the Small Business Administration (SBA); (2) a small 
governmental jurisdiction that is a government of a city, county, town, 
school district or special district with a population of less than 
50,000; and (3) a small organization that is any not-for-profit 
enterprise that is independently owned and operated and is not dominant 
in its field.
    For sources subject to this proposed rule, the relevant NAICS and 
associated employee sizes are listed below:

NAICS 32511--Petrochemical Manufacturing--1,000 employees or fewer.
NAICS 325192--Cyclic Crudes and Intermediates Manufacturing--750 
employees or fewer.
NAICS 325199--All Other Organic Chemical Manufacturing--1,000 employees 
or fewer.

    After considering the economic impacts of this proposal on small 
entities, I certify that this action will not have a significant 
economic impact on a substantial number of small entities. The small 
entities directly regulated by this proposed rule are businesses within 
the NAICS codes mentioned above. There are 51 ultimate parent 
businesses that will be affected by this proposal. Three of these 
businesses are small according to the SBA small business size 
standards. None of these three small firms will have an annualized 
compliance cost of more than 0.03 percent of sales associated with 
meeting the requirements of this proposed rule. For more information on 
the small entity impacts, please refer to the economic impact and small 
business analyses in the rulemaking docket.
    Although the proposed rules will not have a significant economic 
impact on a substantial number of small entities, EPA nonetheless tried 
to reduce the impact of the proposed rule on small entities. When 
developing the HON proposal, EPA took special steps to ensure that the 
burdens imposed on small entities were reasonable. Our economic 
analysis indicates compliance costs are reasonable and no other adverse 
impacts are expected to the affected small businesses. The proposed 
rule will therefore not impose any significant additional regulatory 
costs on affected small entities.
    We continue to be interested in the potential impacts of the 
proposed rule on small entities and welcome comments on issues related 
to such impacts.

D. Unfunded Mandates Reform Act

    Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public 
Law 104-4, establishes requirements for Federal Agencies to assess the 
effects of their regulatory actions on State, local, and tribal 
governments and the private sector. Under section 202 of the UMRA, EPA 
generally must prepare a written statement, including a cost-benefit 
analysis, for proposed and final rules with ``Federal mandates'' that 
may result in expenditures to State, local, and tribal governments, in 
the aggregate, or to the private sector, of $100 million or more in any 
one year. Before promulgating an EPA rule for which a written statement 
is needed, section 205 of the UMRA generally requires EPA to identify 
and consider a reasonable number of regulatory alternatives and adopt 
the least costly, most cost-effective, or least-burdensome alternative 
that achieves the objectives of the rule. The provisions of section 205 
do not apply when they are inconsistent with applicable law. Moreover, 
section 205 allows us to adopt an alternative other than the least-
costly, most cost-effective, or least-burdensome alternative if the 
Administrator publishes with the final rule an explanation why that 
alternative was not adopted. Before we establish any regulatory 
requirements that may significantly or uniquely affect small 
governments, including Tribal governments, it must have developed under 
section 203 of the UMRA a small government agency plan. The plan must 
provide for notifying potentially affected small governments, enabling 
officials of affected small governments to have meaningful and timely 
input in the development of EPA regulatory proposals with significant 
Federal intergovernmental mandates, and informing, educating, and 
advising small governments on compliance with the regulatory 
requirements.
    The proposed rule contains no Federal mandates (under the 
regulatory provisions of title II of the UMRA) for State, local, or 
tribal governments or the private sector. We have determined that the 
proposed rule does not contain a Federal mandate that may result in 
expenditures of $100 million or more for State, local, and Tribal 
governments, in the aggregate, or to the private sector in any one 
year. The total capital costs for this proposed rule are approximately 
$14 million and the total annual costs are approximately $13 million. 
Thus, the proposed rule is not subject to the requirements of sections 
202 and 205 of the UMRA.
    The EPA has determined that this action contains no regulatory 
requirements that might significantly or uniquely affect small 
governments because it contains no requirements that apply to such 
governments or impose obligations upon them. Therefore, the proposed 
rule is not subject to section 203 of the UMRA.

E. Executive Order 13132: Federalism

    Executive Order 13132 (64 FR 43255, August 10, 1999) requires EPA 
to develop an accountable process to ensure ``meaningful and timely 
input by

[[Page 34442]]

State and local officials in the development of regulatory policies 
that have federalism implications.'' ``Policies that have Federalism 
implications'' is defined in the E.O. to include regulations that have 
``substantial direct effects on the States, on the relationship between 
the national Government and the States, or on the distribution of power 
and responsibilities among the various levels of government.''
    The proposed rule does not have Federalism implications. It will 
not have substantial direct effects on the States, on the relationship 
between the national government and the States, or on the distribution 
of power and responsibilities among the various levels of government, 
as specified in E.O. 13132. None of the affected SOCMI facilities are 
owned or operated by State governments. Thus, E.O. 13132 does not apply 
to the proposed rule.

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

    Executive Order 13175 (65 FR 67249, November 9, 2000) requires EPA 
to develop an accountable process to ensure ``meaningful and timely 
input by tribal officials in the development of regulatory policies 
that have tribal implications.''
    The proposed rule does not have tribal implications, as specified 
in E.O. 13175. It will not have substantial direct effects on tribal 
governments, on the relationship between the Federal Government and 
Indian tribes, or on the distribution of power and responsibilities 
between the Federal Government and Indian tribes. No tribal governments 
own SOCMI facilities subject to the HON. Thus, E.O. 13175 does not 
apply to the proposed rule.

G. Executive Order 13045: Protection of Children From Environmental 
Health and Safety Risks

    Executive Order 13045 (62 FR 19885, April 23, 1997) applies to any 
rule that: (1) Is determined to be ``economically significant'' as 
defined under E.O. 12866, and (2) concerns an environmental health or 
safety risk that EPA has reason to believe may have a disproportionate 
effect on children. If the regulatory action meets both criteria, the 
Agency must evaluate the environmental health or safety risk of the 
planned rule on children and explain why the planned regulation is 
preferable to other potentially effective and reasonably feasible 
alternatives considered by the Agency.
    The proposed rule is not subject to the E.O. because it is not 
economically significant as defined in E.O. 12866, and because the 
Agency does not have reason to believe the environmental health or 
safety risks addressed by this action present a disproportionate risk 
to children. This conclusion is based on our assessment of the 
information on the effects on human health and exposures associated 
with SOCMI operations.

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

    Today's final decision is not a ``significant energy action'' as 
defined in E.O. 13211 (66 FR 28355, May 22, 2001) because it is not 
likely to have a significant adverse effect on the supply, 
distribution, or use of energy. Further, we have concluded that today's 
final decision is not likely to have any adverse energy impacts.

I. National Technology Transfer Advancement Act

    Section 112(d) of the National Technology Transfer and Advancement 
Act (NTTAA) of 1995 (Pub. L. 104-113, 12(d) (15 U.S.C. 272 note), 
directs EPA to use voluntary consensus standards (VCS) in its 
regulatory activities unless to do so would be inconsistent with 
applicable law or otherwise impractical. The VCS are technical 
standards. (e.g., materials specifications, test methods, sampling 
procedures, and business practices) that are developed or adopted by 
VCS bodies. The NTTAA directs EPA to provide Congress, through OMB, 
explanations when the Agency decides not to use available and 
applicable VCS.
    The proposed rule revisions do not include technical standards 
beyond those already provided under the current rule. Therefore, EPA is 
not considering the use of any VCS.

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

    Executive Order 12898, ``Federal Actions to Address Environmental 
Justice in Minority Populations and Low-Income Populations,'' requires 
Federal agencies to consider the impact of programs, policies, and 
activities on minority populations and low-income populations. 
According to EPA guidance, agencies are to assess whether minority or 
low-income populations face risks or a rate of exposure to hazards that 
are significant and that ``appreciably exceed or is likely to 
appreciably exceed the risk or rate to the general population or to the 
appropriate comparison group.'' (EPA, 1998)
    The Agency has recently reaffirmed its commitment to ensuring 
environmental justice for all people, regardless of race, color, 
national origin, or income level. To ensure environmental justice, we 
assert that we shall integrate environmental justice considerations 
into all of our programs and policies, and, to this end have identified 
eight national environmental justice priorities. One of the priorities 
is to reduce exposure to air toxics. Since some HON facilities are 
located near minority and low-income populations, we request comment on 
the implications of environmental justice concerns relative to the two 
options proposed. While no exposed person would experience unacceptable 
risks under either of the proposed options, the distribution of risks 
is lower under option 2 than option 1 as reflected in table 3 of this 
preamble. We note, however, that the distributional impacts of the cost 
of option 2 were not quantified in our economic analysis.

List of Subjects in 40 CFR Part 63

    Environmental protection, Air pollution control, Hazardous 
substances, Reporting and recordkeeping requirements.

    Dated: June 1, 2006.
Stephen L. Johnson,
Administrator.

    For the reasons stated in the preamble, title 40, chapter I of the 
Code of Federal Regulations is proposed to be amended as follows:

PART 63--[AMENDED]

    1. The authority citation for part 63 continues to read as follows:

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

Subpart F--[Amended]

    2. Amend Sec.  63.100 by:
    a. Revising paragraph (k) introductory text;
    b. Revising paragraph (m) introductory text; and
    c. Adding paragraph (r) to read as follows:

Sec.  63.100  Applicability and designation of source.

* * * * *
    (k) Except as provided in paragraphs (l), (m), (p), and (r) of this 
section, sources subject to subparts F, G, or H of this part are 
required to achieve compliance on or before the dates specified in 
paragraphs (k)(1) through (k)(8) of this section.
* * * * *
    (m) Before [DATE THE FINAL RULE IS PUBLISHED IN THE FEDERAL

[[Page 34443]]

REGISTER], if a change that does not meet the criteria in paragraph 
(l)(4) of this section is made to a chemical manufacturing process unit 
subject to subparts F and G of this part, and the change causes a Group 
2 emission point to become a Group 1 emission point (as defined in 
Sec.  63.111 of subpart G of this part), then the owner or operator 
shall comply with the requirements of subpart G of this part for the 
Group 1 emission point as expeditiously as practicable, but in no event 
later than 3 years after the emission point becomes Group 1. After 
[DATE THE FINAL RULE IS PUBLISHED IN THE FEDERAL REGISTER], the owner 
or operator subject to this paragraph must comply with subpart G of 
this part no later than three years after the emission point becomes a 
Group 1 emission point (as defined in Sec.  63.111 of subpart G of this 
part).
* * * * *
    (r) Compliance with standards to protect public health and the 
environment. On or after [DATE THE FINAL RULE IS PUBLISHED IN THE 
FEDERAL REGISTER], the owner or operator must comply with the 
provisions of paragraphs (r)(1) and (r)(2) of this section to protect 
public health and the environment.
    (1) Process vents and storage vessels. On or after [DATE THE FINAL 
RULE IS PUBLISHED IN THE FEDERAL REGISTER], the definitions of Group 1 
process vent and Group 1 storage vessel change such that some Group 2 
emission points may become Group 1 emission points. Notwithstanding the 
provisions of paragraph (k) of this section, any existing Group 2 
process vent or Group 2 storage vessel that becomes a Group 1 emission 
point on [DATE THE FINAL RULE IS PUBLISHED IN THE FEDERAL REGISTER] as 
a result of the revised definition must be in compliance with subparts 
F and G of this part no later than [DATE THREE YEARS AFTER THE DATE THE 
FINAL RULE IS PUBLISHED IN THE FEDERAL REGISTER]. New sources that 
commence construction or reconstruction after [DATE OF PUBLICATION OF 
FINAL RULE IN THE FEDERAL REGISTER] must be in compliance with subparts 
F and G of this part upon start-up or by [DATE FINAL RULE IS PUBLISHED 
IN THE FEDERAL REGISTER], whichever is later.
    (2) Equipment leaks. On or after [DATE THE FINAL RULE IS PUBLISHED 
IN THE FEDERAL REGISTER], an existing chemical manufacturing process 
unit containing at least one HAP from table 38 of subpart G of part 63, 
that is subject to Sec.  63.168 of subpart H of this part (Standards: 
Valves in gas/vapor service and light liquid service) must comply with 
paragraph (k) in Sec.  63.168 of subpart H of this part no later than 
[DATE ONE YEAR AFTER THE DATE THE FINAL RULE IS PUBLISHED IN THE 
FEDERAL REGISTER]. New sources that commence construction or 
reconstruction after [DATE OF PUBLICATION OF FINAL RULE IN THE FEDERAL 
REGISTER] must be in compliance with subparts F and G of this part upon 
start-up or by [DATE FINAL RULE IS PUBLISHED IN THE FEDERAL REGISTER], 
whichever is later.

Subpart G--[Amended]

    3. Amend Sec.  63.110 by revising paragraphs (b)(3) and (i)(1)(i) 
and (ii) to read as follows:

Sec.  63.110  Applicability.

* * * * *
    (b) * * *
    (3) On or after the compliance dates specified in Sec.  63.100 of 
subpart F of this part, a Group 2 storage vessel that is also subject 
to the provisions of 40 CFR part 61, subpart Y is required to comply 
only with the provisions of 40 CFR part 61, subpart Y. The 
recordkeeping and reporting requirements of 40 CFR part 61, subpart Y 
will be accepted as compliance with the recordkeeping and reporting 
requirements of this subpart. On or after [DATE THREE YEARS AFTER THE 
DATE THE FINAL RULE IS PUBLISHED IN THE FEDERAL REGISTER], the owner or 
operator must also keep records of the emissions of hazardous air 
pollutants listed in table 38 of this subpart as specified in Sec.  
63.123(b). New sources that commence construction or reconstruction 
after [DATE OF PUBLICATION OF FINAL RULE IN THE FEDERAL REGISTER] must 
keep records of the emissions of hazardous air pollutants listed in 
table 38 of this subpart as specified in Sec.  63.123(b) upon start-up 
or by [DATE FINAL RULE IS PUBLISHED IN THE FEDERAL REGISTER], whichever 
is later.
* * * * *
    (i) * * *
    (1) * * *
    (i) For Group 1 and Group 2 process vents, 40 CFR part 65, subpart 
D, satisfies the requirements of Sec. Sec.  63.102, 63.103, 63.112 
through 63.118, 63.148, 63.151, and 63.152. On or after [DATE THREE 
YEARS AFTER THE DATE THE FINAL RULE IS PUBLISHED IN THE FEDERAL 
REGISTER], for process vents emitting a hazardous air pollutant listed 
in table 38 of this subpart, a TRE value of 4.0 replaces references to 
a TRE value of 1.0 in 40 CFR part 65, except in 40 CFR 65.62(c), and 
requirements for Group 1 process vents in 40 CFR part 65 also apply to 
Group 2A process vents. The provisions of this paragraph apply to new 
sources that commence construction or reconstruction after [DATE OF 
PUBLICATION OF FINAL RULE IN THE FEDERAL REGISTER] upon start-up or by 
[DATE FINAL RULE IS PUBLISHED IN THE FEDERAL REGISTER], whichever is 
later.
    (ii) For Group 1 storage vessels, 40 CFR part 65, subpart C 
satisfies the requirements of Sec. Sec.  63.102, 63.103, 63.112, 63.119 
through 63.123, 63.148, 63.151, and 63.152. On or after [DATE THREE 
YEARS AFTER THE DATE THE FINAL RULE IS PUBLISHED IN THE FEDERAL 
REGISTER], the owner or operator must also keep records specified in 
Sec.  63.123(b). New sources that commence construction or 
reconstruction after [DATE OF PUBLICATION OF FINAL RULE IN THE FEDERAL 
REGISTER] must keep records of the emissions of hazardous air 
pollutants listed in table 38 of this subpart as specified in Sec.  
63.123(b) upon start-up or by [DATE FINAL RULE IS PUBLISHED IN THE 
FEDERAL REGISTER], whichever is later.
* * * * *
    4. Amend Sec.  63.111 by revising the following definitions of 
Group 1 process vent, Group 2 process vent, and Group 1 storage vessel 
to read as follows:

Sec.  63.111  Definitions.

* * * * *
    Group 1 process vent means a process vent for which the vent stream 
flow rate is greater than or equal to 0.005 standard cubic meter per 
minute, the total organic hazardous air pollutant concentration is 
greater than or equal to 50 ppmv, and the total resource effectiveness 
index value, calculated according to Sec.  63.115, is less than or 
equal to 1.0. On or after [DATE THE FINAL RULE IS PUBLISHED IN THE 
FEDERAL REGISTER], a Group 1 process vent also means a process vent for 
which the vent stream flow rate is greater than or equal to 0.005 
standard cubic meters per minute, the total organic HAP concentration 
is greater than or equal to 50 ppmv, the process vent contains at least 
one hazardous air pollutant listed in table 38 of this subpart, and the 
total resource effectiveness index value, calculated according to Sec.  
63.115, is less than or equal to 4.0.
    Group 2 process vent means a process vent that does not meet the 
definition of Group 1 process vent.

[[Page 34444]]

    Group 1 storage vessel means a storage vessel that meets the 
criteria for design storage capacity and stored-liquid maximum true 
vapor pressure specified in table 5 of this subpart for storage vessels 
at existing sources, and in table 6 of this subpart for storage vessels 
at new sources. On or after [DATE THE FINAL RULE IS PUBLISHED IN THE 
FEDERAL REGISTER], a Group 1 storage vessel also means a storage vessel 
that stores at least 1 hazardous air pollutant listed in table 38 of 
this subpart, and has a total hazardous air pollutant emission rate 
greater than 4.54 megagrams per year.
* * * * *
    5. Amend Sec.  63.113 by revising paragraphs (a)(3) and (d) to read 
as follows:

Sec.  63.113  Process vent provisions--reference control technology.

    (a) * * *
    (3) Comply with paragraph (a)(3)(i), (a)(3)(ii), or (a)(3)(iii) of 
this section.
    (i) Prior to [DATE THE FINAL RULE IS PUBLISHED IN THE FEDERAL 
REGISTER], achieve and maintain a TRE index value greater than 1.0 at 
the outlet of the final recovery device, or prior to release of the 
vent stream to the atmosphere if no recovery device is present. If the 
TRE index value is greater than 1.0, the process vent shall comply with 
the provisions for a Group 2 process vent specified in either paragraph 
(d) or (e) of this section, whichever is applicable.
    (ii) On or after [DATE THREE YEARS AFTER THE DATE THE FINAL RULE IS 
PUBLISHED IN THE FEDERAL REGISTER], for process vents containing a 
hazardous air pollutant listed in table 38 of this subpart, achieve and 
maintain a TRE index value greater than 4.0 at the outlet of the final 
recovery device, or prior to release of the vent stream to the 
atmosphere if no recovery device is present. If the TRE index value is 
greater than 4.0, the process vent shall comply with the provisions for 
a Group 2 process vent specified in either paragraph (d) or (e) of this 
section, whichever is applicable. The provisions of this paragraph 
apply to new sources that commence construction or reconstruction after 
[DATE OF PUBLICATION OF FINAL RULE IN THE FEDERAL REGISTER] on or after 
[DATE FINAL RULE IS PUBLISHED IN THE FEDERAL REGISTER].
    (iii) On or after [DATE THREE YEARS AFTER THE DATE THE FINAL RULE 
IS PUBLISHED IN THE FEDERAL REGISTER], for process vents not containing 
a hazardous air pollutant listed in table 38 of this subpart, achieve 
and maintain a TRE index value greater than 1.0 at the outlet of the 
final recovery device, or prior to release of the vent stream to the 
atmosphere if no recovery device is present. If the TRE index value is 
greater than 1.0, the process vent shall comply with the provisions for 
a Group 2 process vent specified in either paragraph (d) or (e) of this 
section, whichever is applicable. The provisions of this paragraph 
apply to new sources that commence construction or reconstruction after 
[DATE OF PUBLICATION OF FINAL RULE IN THE FEDERAL REGISTER] upon start-
up or by [DATE FINAL RULE IS PUBLISHED IN THE FEDERAL REGISTER], 
whichever is later.
* * * * *
    (d) The owner or operator of a Group 2 process vent meeting the 
conditions of paragraphs (d)(1) or (d)(2) shall maintain a TRE index 
value greater than 1.0 and shall comply with the monitoring of recovery 
device parameters in Sec.  63.114(b) or (c) of this subpart, the TRE 
index calculations of Sec.  63.115 of this subpart, and the applicable 
reporting and recordkeeping provisions of Sec. Sec.  63.117 and 63.118 
of this subpart. Such owner or operator is not subject to any other 
provisions of Sec. Sec.  63.114 through 63.118 of this subpart.
    (1) Prior to [DATE THE FINAL RULE IS PUBLISHED IN THE FEDERAL 
REGISTER], the process vent has a flow rate greater than or equal to 
0.005 standard cubic meters per minute, a hazardous air pollutant 
concentration greater than or equal to 50 parts per million by volume, 
and a TRE index value greater than 1.0 but less than or equal to 4.0.
    (2) On or after [DATE THE FINAL RULE IS PUBLISHED IN THE FEDERAL 
REGISTER], the process vent does not emit any hazardous air pollutants 
listed in table 38 of this subpart, but has a flow rate greater than or 
equal to 0.005 standard cubic meters per minute, a hazardous air 
pollutant concentration greater than or equal to 50 parts per million 
by volume, and a TRE index value greater than 1.0 but less than or 
equal to 4.0
* * * * *
    6. Amend Sec.  63.114 by revising paragraphs (b) introductory text 
and (c)(2) to read as follows:

Sec.  63.114  Process vent provisions--monitoring requirements.

* * * * *
    (b) Each owner or operator of a Group 2 process vent that complies 
by following Sec.  63.113(a)(3) or Sec.  63.113(d) of this subpart that 
uses one or more recovery devices shall install either an organic 
monitoring device equipped with a continuous recorder or the monitoring 
equipment specified in paragraph (b)(1), (b)(2), or (b)(3) of this 
section, depending on the type of recovery device used. All monitoring 
equipment shall be installed, calibrated, and maintained according to 
the manufacturer's specifications or other written procedures that 
provide adequate assurance that the equipment would reasonably be 
expected to monitor accurately. Monitoring is not required for process 
vents with TRE index values greater than 4.0 as specified in Sec.  
63.113(e) of this subpart.
* * * * *
    (c) * * *
    (2) Complies by following the requirements of Sec.  63.113(a)(3) or 
Sec.  63.113(d), and maintains a TRE greater than 1.0 but less than or 
equal to 4.0 without a recovery device or with a recovery device other 
than the recovery devices listed in paragraphs (a) and (b) of this 
section; or
* * * * *
    7. Amend Sec.  63.115 by revising paragraph (e)(2) to read as 
follows:

Sec.  63.115  Process vent provisions--methods and procedures for 
process vent group determination.

* * * * *
    (e) * * *
    (2) Where a process vent with the recalculated TRE index value 
meets the Group 1 definition, or where the recalculated TRE index 
value, flow rate, or concentration meet the specifications of Sec.  
63.113(d) of this subpart, the owner or operator shall submit a report 
as specified in Sec.  63.118 (g), (h), (i), or (j) of this subpart and 
shall comply with the appropriate provisions in Sec.  63.113 of this 
subpart by the dates specified in Sec.  63.100 of subpart F of this 
part.
* * * * *
    8. Amend Sec.  63.117 by revising paragraph (a) introductory text 
and paragraph (a)(7) introductory text to read as follows:

Sec.  63.117  Process vent provisions--reporting and recordkeeping 
requirements for group and TRE determinations and performance tests.

    (a) Each owner or operator subject to the provisions for process 
vents with a TRE index value less than or equal to 4.0 shall:
* * * * *
    (7) Record and report the following when achieving and maintaining 
a TRE index value of 4.0 or less, as specified in Sec.  63.113(a)(3) or 
Sec.  63.113(d) of this subpart:
* * * * *

[[Page 34445]]

    9. Amend Sec.  63.118 by revising paragraphs (b) introductory text, 
paragraph (c) introductory text, and paragraph (h) introductory text to 
read as follows:

Sec.  63.118  Process vent provisions--periodic reporting and 
recordkeeping requirements.

* * * * *
    (b) Each owner or operator using a recovery device or other means 
to achieve and maintain a TRE index value less than or equal to 4.0 as 
specified in Sec.  63.113(a)(3) or Sec.  63.113(d) of this subpart 
shall keep the following records up-to-date and readily accessible:
* * * * *
    (c) Each owner or operator subject to the provisions of this 
subpart and who elects to demonstrate compliance with the TRE index 
value greater than 4.0 under Sec.  63.113(e) of this subpart or less 
than or equal to 4.0 under Sec.  63.113(a)(3) or Sec.  63.113(d) of 
this subpart shall keep up-to-date, readily accessible records of:
* * * * *
    (h) Whenever a process change, as defined in Sec.  63.115(e) of 
this subpart, is made that causes a Group 2 process vent with a TRE 
greater than 4.0 to become a Group 2 process vent with a TRE less than 
or equal to 4.0, the owner or operator shall submit a report within 180 
calendar days after the process change. The report may be submitted as 
part of the next periodic report. The report shall include:
* * * * *
    10. Amend Sec.  63.119 by revising paragraph (a)(1) and (a)(2) to 
read as follows:

Sec.  63.119  Storage vessel provisions--reference control technology.

    (a) * * *
    (1) For each Group 1 storage vessel storing a liquid for which the 
maximum true vapor pressure of the total organic hazardous air 
pollutants in the liquid is less than 76.6 kilopascals, the owner or 
operator shall reduce hazardous air pollutants emissions to the 
atmosphere either by operating and maintaining a fixed roof and 
internal floating roof, an external floating roof, an external floating 
roof converted to an internal floating roof, a closed vent system and 
control device, routing the emissions to a process or a fuel gas 
system, or vapor balancing in accordance with the requirements in 
paragraph (b), (c), (d), (e), (f), or (g) of this section, or 
equivalent as provided in Sec.  63.121 of this subpart.
    (2) For each Group 1 storage vessel storing a liquid for which the 
maximum true vapor pressure of the total organic hazardous air 
pollutants in the liquid is greater than or equal to 76.6 kilopascals, 
the owner or operator shall operate and maintain a closed vent system 
and control device meeting the requirements specified in paragraph (e) 
of this section, route the emissions to a process or a fuel gas system 
as specified in paragraph (f) of this section, vapor balance as 
specified in paragraph (g) of this section, or equivalent as provided 
in Sec.  63.121 of this subpart.
* * * * *
    11. Amend Sec.  63.120 by revising paragraph (b)(1)(iv) to read as 
follows:

Sec.  63.120  Storage vessel provisions--procedures to determine 
compliance.

* * * * *
    (b) * * *
    (1) * * *
    (iv) If any storage vessel ceases to store organic hazardous air 
pollutants for a period of 1 year or more, or if the storage vessel 
ceases to meet the definition of a Group 1 storage vessel for a period 
of 1 year or more, then measurements of gaps between the vessel wall 
and the primary seal, and gaps between the vessel wall and the 
secondary seal, shall be performed within 90 calendar days of the 
vessel being refilled with organic hazardous air pollutants.
* * * * *
    12. Amend Sec.  63.123 by adding paragraph (b) to read as follows.

Sec.  63.123  Storage vessel provisions--recordkeeping.

* * * * *
    (b) On or after [DATE THREE YEARS AFTER THE DATE THE FINAL RULE IS 
PUBLISHED IN THE FEDERAL REGISTER], an owner or operator must keep 
records of the uncontrolled hazardous air pollutant emissions from each 
Group 2 storage vessel, containing at least one hazardous air pollutant 
listed in table 38 of this subpart, on a 12-month rolling average. 
Calculate uncontrolled hazardous air pollutant emissions 
(ESiu) using the equations and procedures in Sec.  
63.150(g)(3)(i). The provisions of this paragraph apply to new sources 
that commence construction or reconstruction after [DATE OF PUBLICATION 
OF FINAL RULE IN THE FEDERAL REGISTER] upon start-up or by [DATE FINAL 
RULE IS PUBLISHED IN THE FEDERAL REGISTER], whichever is later.
* * * * *
    13. Amend Sec.  63.150 by revising paragraph (g)(2)(iii)(B)(2) to 
read as follows:

Sec.  63.150  Emissions averaging provisions

* * * * *
    (g) * * *
    (2) * * *
    (iii) * * *
    (B) * * *
    (2) For determining debits from Group 1 process vents, recovery 
devices shall not be considered control devices and cannot be assigned 
a percent reduction in calculating EPViACTUAL. The sampling 
site for measurement of uncontrolled emissions is after the final 
recovery device. However, as provided in Sec.  63.113(a)(3), a Group 1 
process vent may add sufficient recovery to raise the TRE index value 
to a level such that the vent becomes a Group 2 process vent.
* * * * *
    14. Amend the appendices to subpart G by adding Table 38 to subpart 
G of part 63--List of Hazardous Air Pollutants Subject to Additional 
Requirements to Protect Public Health and the Environment.

------------------------------------------------------------------------
                         Pollutant                             CAS No.
------------------------------------------------------------------------
1,1,2,2-Tetrachloroethane..................................        79345
1,1,2-Trichloroethane......................................        79005
1,2-Diphenylhydrazine......................................       122667
1,3-Butadiene..............................................       106990
1,3-Dichloropropene........................................       542756
1,4-Dioxane................................................       123911
2,4-Dinitrotoluene.........................................       121142
2,4-Toluene diamine........................................        95807
2,4-Toluene diisocyanate...................................       584849
2-Nitropropane.............................................        79469
3,3'-Dichlorobenzidine.....................................        91941
3,3'-Dimethylbenzidine.....................................       119937
Acetaldehyde...............................................        75070
Acetamide..................................................        60355
Acrolein...................................................       107028
Acrylamide.................................................        79061
Acrylonitrile..............................................       107131
Allyl chloride.............................................       107051
Aniline....................................................        62533
Benzene....................................................        71432
Benzotrichloride...........................................        98077
Benzyl chloride............................................       100447
Bis (chloromethyl) ether...................................       542881
Bromoform..................................................        75252
Carbon tetrachloride.......................................        56235
Chrysene...................................................       218019
Dichloroethyl ether........................................       111444
Epichlorohydrin............................................       106898
Ethyl acrylate.............................................       140885
Ethylene dibromide.........................................       106934
Ethylene dichloride........................................       107062
Ethylene oxide.............................................        75218
Ethylidene dichloride......................................        75343
Formaldehyde...............................................        50000
Hexachlorobenzene..........................................       118741
Hexachlorobutadiene........................................        87683
Hexachloroethane...........................................        67721
Isophorone.................................................        78591
Maleic anhydride...........................................       108316
Methyl bromide.............................................        74839
Methyl tert-butyl ether....................................      1634044
Methylene chloride.........................................        75092
Naphthalene................................................        91203
o-Toluidine................................................        95534
p-Dichlorobenzene..........................................       106467
Propylene dichloride.......................................        78875
Propylene oxide............................................        75569
Tetrachloroethene..........................................       127184
Trichloroethylene..........................................        79016

[[Page 34446]]

Vinyl chloride.............................................        75014
------------------------------------------------------------------------

Subpart H--[Amended]

    15. Amend Sec.  63.160 by revising paragraph (g)(1)(i) and 
(g)(1)(ii) to read as follows:

Sec.  63.160  Applicability and designation of source.

* * * * *
    (g) * * *
    (1) * * *
    (i) For equipment, 40 CFR part 65 satisfies the requirements of 
Sec. Sec.  63.102, 63.103, and 63.162 through 63.182. When choosing to 
comply with 40 CFR part 65, the requirements of Sec.  63.180(d) 
continue to apply. On or after [DATE ONE YEAR AFTER THE DATE THE FINAL 
RULE IS PUBLISHED IN THE FEDERAL REGISTER], owners or operators must 
comply with the valve monitoring frequencies and valve leak frequencies 
in Sec.  63.168(k) instead of Sec.  65.106(b)(3) for processes that 
contain at least one hazardous air pollutant listed in table 38 of 
subpart F. New sources that commence construction or reconstruction 
after [DATE OF PUBLICATION OF FINAL RULE IN THE FEDERAL REGISTER] must 
comply with the valve monitoring frequencies and valve leak frequencies 
in Sec.  63.168(k) instead of Sec.  65.106(b)(3) for processes that 
contain at least one hazardous air pollutant listed in table 38 of 
subpart F upon start-up or by [DATE FINAL RULE IS PUBLISHED IN THE 
FEDERAL REGISTER], whichever is later.
    (ii) For Group 1 and Group 2 process vents, Group 1 and Group 2 
storage vessels, and Group 1 transfer operations, comply with Sec.  
63.110(i)(1).
* * * * *
    16. Amend Sec.  63.168 by revising paragraph (a) introductory text 
and adding paragraph (k) to read as follows:

Sec.  63.168  Standards: Valves in gas/vapor service and in light 
liquid service.

    (a) The provisions of this section apply to valves that are either 
in gas service or in light liquid service. On or after [DATE ONE YEAR 
AFTER THE DATE THE FINAL RULE IS PUBLISHED IN THE FEDERAL REGISTER] the 
owner or operator of a process unit containing at least one HAP from 
table 38 of subpart G of part 63, must comply with monitoring frequency 
and leak frequency requirements in paragraph (k) of this section. New 
sources that commence construction or reconstruction after [DATE OF 
PUBLICATION OF FINAL RULE IN THE FEDERAL REGISTER] must comply with the 
provisions of this paragraph upon start-up or by [DATE FINAL RULE IS 
PUBLISHED IN THE FEDERAL REGISTER], whichever is later.
* * * * *
    (k) On or after [DATE ONE YEAR AFTER THE DATE THE FINAL RULE IS 
PUBLISHED IN THE FEDERAL REGISTER], the owner or operator of a source 
subject to this subpart shall monitor all valves at process units 
containing at least one HAP from table 38 of subpart G of part 63, 
except as provided in Sec.  63.162(b) of this subpart and paragraphs 
(h) and (i) of this section, at the intervals specified in paragraph 
(k)(2) of this section and shall comply with all other provisions of 
this section, except as provided in Sec. Sec.  63.171, 63.177, 63.178, 
and 63.179 of this subpart. New sources that commence construction or 
reconstruction after [DATE OF PUBLICATION OF FINAL RULE IN THE FEDERAL 
REGISTER] must comply with the provisions of this paragraph by upon 
start-up or [DATE FINAL RULE IS PUBLISHED IN THE FEDERAL REGISTER], 
whichever is later.
    (1) The valves shall be monitored to detect leaks by the method 
specified in Sec.  63.180(b) of this subpart. The instrument reading 
that defines a leak is 500 parts per million.
    (2) The owner or operator shall monitor valves for leaks at the 
intervals specified in paragraphs (k)(2)(i) through (k)(2)(v) of this 
section. Monitoring data generated before [DATE THE FINAL RULE IS 
PUBLISHED IN THE FEDERAL REGISTER], may be used to qualify for less 
frequent monitoring under paragraphs (k)(2)(ii) through paragraphs 
(k)(2)(v) of this section.
    (i) At process units with 0.5 percent or greater leaking valves, 
calculated according to paragraph (e) of this section, the owner or 
operator shall monitor each valve once per month.
    (ii) At process units with less than 0.5 percent leaking valves, 
the owner or operator shall monitor each valve once each quarter, 
except as provided in paragraphs (k)(2)(iii) through (k)(2)(v) of this 
section.
    (iii) At process units with less than 0.5 percent leaking valves 
over two consecutive quarters, the owner or operator may elect to 
monitor each valve once every 2 quarters.
    (iv) At process units with less than 0.5 percent leaking valves 
over three out of four consecutive quarters, the owner or operator may 
elect to monitor each valve once every 4 quarters.
    (v) At process units with less than 0.25 percent leaking valves 
over two consecutive periods, the owner or operator may elect to 
monitor each valve once every two years.

[FR Doc. 06-5219 Filed 6-13-06; 8:45 am]

BILLING CODE 6560-50-P