[Federal Register: December 1, 2008 (Volume 73, Number 231)]
[Proposed Rules]
[Page 72961-73003]
[DOCID:fr01de08-26]

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Part III

Environmental Protection Agency

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40 CFR Part 60

Standards of Performance for New Stationary Sources and Emission
Guidelines for Existing Sources: Hospital/Medical/Infectious Waste
Incinerators; Proposed Rule

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 60

[EPA-HQ-OAR-2006-0534; FRL-8743-1]
RIN 2060-A004

Standards of Performance for New Stationary Sources and Emission
Guidelines for Existing Sources: Hospital/Medical/Infectious Waste
Incinerators

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: On September 15, 1997, EPA adopted new source performance
standards (NSPS) and emission guidelines (EG) for hospital/medical/
infectious waste incinerators (HMIWI). The NSPS and EG were established
under sections 111 and 129 of the Clean Air Act (CAA or Act). The
Sierra Club and the Natural Resources Defense Council (Sierra Club)
filed suit in the U.S. Court of Appeals for the District of Columbia
Circuit (the Court) challenging EPA's methodology for adopting the
regulations. On March 2, 1999, the Court remanded the rule to EPA for
further explanation of the Agency's reasoning in determining the
minimum regulatory ``floors'' for new and existing HMIWI. The Court did
not vacate the regulations, so the NSPS and EG remain in effect and
were fully implemented by September 2002.
    On February 6, 2007, EPA published a proposed response to the
Court's remand and a proposed response to the CAA section 129(a)(5)
requirement to review the NSPS and EG every 5 years. However, following
recent court decisions and receipt of public comments regarding that
proposal, we chose to re-assess our response to the Court's remand.
Therefore, this action provides the results of EPA's reassessment in
the form of another proposed response to the Court's remand and
solicits public comment regarding it. This re-proposal also satisfies
the CAA section 129(a)(5) requirement to conduct a review of the
standards every 5 years.

DATES: Comments. Comments must be received on or before February 17,
2009. Under the Paperwork Reduction Act, comments on the information
collection provisions must be received by the Office of Management and
Budget (OMB) on or before December 31, 2008. Because of the need to
resolve the issues raised in this action in a timely manner, EPA will
not grant requests for extensions beyond these dates.
    Public Hearing. If anyone contacts EPA by December 22, 2008
requesting to speak at a public hearing, EPA will hold a public hearing
on January 15, 2009.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2006-0534, by one of the following methods:
    http://www.regulations.gov: Follow the on-line instructions for
submitting comments.
    E-mail: Send your comments via electronic mail to a-and-r-
<EMAIL_ADDRESS>Attention Docket ID No. EPA-HQ-OAR-2006-0534.
    Facsimile: Fax your comments to<PHONE_NUMBER>, Attention Docket ID
No. EPA-HQ-OAR-2006-0534.
    Mail: Send your comments to: EPA Docket Center (EPA/DC),
Environmental Protection Agency, Mailcode 6102T, 1200 Pennsylvania
Ave., NW., Washington, DC 20460, Attention Docket ID No. EPA-HQ-OAR-
2006-0534. 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).
    Hand Delivery: Deliver your comments to: EPA Docket Center (EPA/
DC), EPA West Building, Room 3334, 1301 Constitution Ave., NW.,
Washington, DC, 20460, Attention Docket ID No. EPA-HQ-OAR-2006-0534.
Such deliveries are accepted only during the normal hours of operation
(8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal
holidays), and special arrangements should be made for deliveries of
boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2006-0534. The EPA's policy is that all comments received will be
included in the public docket 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 and with any
disk or CD-ROM you submit. If EPA cannot read your comment due to
technical difficulties and cannot contact you for clarification, EPA
may not be able to consider your comment. Electronic files should avoid
the use of special characters, any form of encryption, and be free of
any defects or viruses.
    Public Hearing: If a public hearing is held, it will be held at
EPA's Campus located at 109 T.W. Alexander Drive in Research Triangle
Park, NC, or an alternate site nearby. Contact Ms. Pamela Garrett at
(919) 541-7966 to request a hearing, to request to speak at a public
hearing, to determine if a hearing will be held, or to determine the
hearing location. If no one contacts EPA requesting to speak at a
public hearing concerning this proposed rule by December 22, 2008, the
hearing will be cancelled without further notice.
    Docket: EPA has established a docket for this action under Docket
ID No. EPA-HQ-OAR-2006-0534 and Legacy Docket ID No. A-91-61. 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 form. Publicly
available docket materials are available either electronically at
http://www.regulations.gov or in hard copy at the EPA Docket Center
EPA/DC, EPA West, Room 3334, 1301 Constitution Ave., NW., Washington,
DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday
through Friday, excluding legal holidays. The telephone number for the
Public Reading Room is<PHONE_NUMBER>, and the telephone number for the
EPA Docket Center is<PHONE_NUMBER>.

FOR FURTHER INFORMATION CONTACT: Ms. Mary Johnson, Energy Strategies
Group, Sector Policies and Programs Division (D243-01), Environmental
Protection Agency, Research Triangle Park, North Carolina 27711;
telephone number:<PHONE_NUMBER>; fax number:<PHONE_NUMBER>; e-mail
address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION: Organization of This Document. The following
outline is provided to aid in locating information in this preamble.

I. General Information

    A. Does the proposed action apply to me?
    B. What should I consider as I prepare my comments?
II. Background
III. Summary
    A. Litigation and Proposed Remand Response
    B. Proposed CAA Section 129(a)(5) 5-Year Review Response
    C. Other Proposed Amendments
    D. Proposed Implementation Schedule for Existing HMIWI
    E. Proposed Changes to the Applicability Date of the 1997 NSPS
IV. Rationale
    A. Rationale for the Proposed Response to the Remand
    B. Rationale for the Proposed CAA Section 129(a)(5) 5-Year
Review Response
    C. Rationale for Other Proposed Amendments
V. Impacts of the Proposed Action for Existing Units
    A. What are the primary air impacts?
    B. What are the water and solid waste impacts?
    C. What are the energy impacts?
    D. What are the secondary air impacts?
    E. What are the cost and economic impacts?
VI. Impacts of the Proposed Action for New Units
    A. What are the primary air impacts?
    B. What are the water and solid waste impacts?
    C. What are the energy impacts?
    D. What are the secondary air impacts?
    E. What are the cost and economic impacts?
VII. Relationship of the Proposed Action to Section 112(c)(6) of the
CAA
VIII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination with
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children from
Environmental Health and Safety Risks
    H. Executive Order 13211: Actions That Significantly Affect
Energy Supply, Distribution or Use
    I. National Technology Transfer Advancement Act
    J. Executive Order 12898: Federal Actions to Address
Environmental Justice in Minority Populations and Low-Income
Populations

I. General Information

A. Does the proposed action apply to me?

    Regulated Entities. Categories and entities potentially affected by
the proposed action are those which operate HMIWI. The NSPS and EG for
HMIWI affect the following categories of sources:

------------------------------------------------------------------------
                                                 Examples of potentially
            Category               NAICS Code       regulated entities
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Industry.......................          622110  Private hospitals,
                                                  other health care
                                                  facilities, commercial
                                                  research laboratories,
                                                  commercial waste
                                                  disposal companies,
                                                  private universities
                                         622310
                                         325411
                                         325412
                                         562213
                                         611310
Federal Government.............          622110  Federal hospitals,
                                                  other health care
                                                  facilities, public
                                                  health service, armed
                                                  services
                                         541710
                                         928110
State/local/Tribal Government..          622110  State/local hospitals,
                                                  other health care
                                                  facilities, State/
                                                  local waste disposal
                                                  services, State
                                                  universities
                                         562213
                                         611310
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    This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be affected by the
proposed action. To determine whether your facility would be affected
by the proposed action, you should examine the applicability criteria
in 40 CFR 60.50c of subpart Ec and 40 CFR 60.32e of subpart Ce. If you
have any questions regarding the applicability of the proposed action
to a particular entity, contact the person listed in the preceding FOR
FURTHER INFORMATION CONTACT section.

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

1. Submitting CBI
    Do not submit information that you consider to be CBI
electronically through http://www.regulations.gov or e-mail. Send or
deliver information identified as CBI to only the following address:
Ms. Mary Johnson, c/o OAQPS Document Control Officer (Room C404-02),
U.S. EPA, Research Triangle Park, NC 27711, Attention Docket ID No.
EPA-HQ-OAR-2006-0534. Clearly mark the part or all of the information
that you claim to be CBI. For CBI information in a disk or CD ROM that
you mail to EPA, mark the outside of the disk or CD ROM as CBI and then
identify electronically within the disk or CD ROM the specific
information that is claimed as CBI. In addition to one complete version
of the comment that includes information claimed as CBI, a copy of the
comment that does not contain the information claimed as CBI must be
submitted for inclusion in the public docket. Information marked as CBI
will not be disclosed except in accordance with procedures set forth in
40 CFR part 2.
    If you have any questions about CBI or the procedures for claiming
CBI, please consult the person identified in the FOR FURTHER
INFORMATION CONTACT section.
2. Tips for Preparing Your Comments
    When submitting comments, remember to:
    a. Identify the rulemaking by docket number and other identifying
information (subject heading, Federal Register date and page number).
    b. Follow directions. EPA may ask you to respond to specific
questions or organize comments by referencing a Code of Federal
Regulations (CFR) part or section number.
    c. Explain why you agree or disagree; suggest alternatives and
substitute language for your requested changes.
    d. Describe any assumptions and provide any technical information
and/or data that you used.
    e. If you estimate potential costs or burdens, explain how you
arrived at your estimate in sufficient detail to allow for it to be
reproduced.
    f. Provide specific examples to illustrate your concerns, and
suggest alternatives.
    g. Explain your views as clearly as possible, avoiding the use of
profanity or personal threats.
    h. Make sure to submit your comments by the comment period

deadline identified in the preceding section titled DATES.
3. Docket
    The docket number for the proposed action regarding the HMIWI NSPS
(40 CFR part 60, subpart Ec) and EG (40 CFR part 60, subpart Ce) is
Docket ID No. EPA-HQ-OAR-2006-0534.
4. Worldwide Web (WWW)
    In addition to being available in the docket, an electronic copy of
the proposed action is available on the WWW through the Technology
Transfer Network Web site (TTN Web). Following signature, EPA posted a
copy of the proposed action 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.

II. Background

    Section 129 of the CAA, entitled ``Solid Waste Combustion,''
requires EPA to develop and adopt NSPS and EG for solid waste
incineration units pursuant to CAA sections 111 and 129. Sections
111(b) and 129(a) of the CAA (NSPS program) address emissions from new
HMIWI, and CAA sections 111(d) and 129(b) (EG program) address
emissions from existing HMIWI. The NSPS are directly enforceable
Federal regulations, and under CAA section 129(f)(1) become effective 6
months after promulgation. Under CAA section 129(f)(2), the EG become
effective and enforceable the sooner of 3 years after EPA approves a
State plan implementing the EG or 5 years after the date they are
promulgated.
    An HMIWI is defined as any device used to burn hospital waste or
medical/infectious waste. Hospital waste means discards generated at a
hospital, and medical/infectious waste means any waste generated in the
diagnosis, treatment, or immunization of human beings or animals, in
research pertaining thereto, or in the production or testing of
biologicals (e.g., vaccines, cultures, blood or blood products, human
pathological waste, sharps). As explained in EPA's regulations,
hospital/medical/infectious waste does not include household waste,
hazardous waste, or human and animal remains not generated as medical
waste. An HMIWI typically is a small, dual-chamber incinerator that
burns on average about 800 pounds per hour (lb/hr) of waste. Smaller
units burn as little as 15 lb/hr while larger units burn as much as
3,700 lb/hr, on average.
    Incineration of hospital/medical/infectious waste causes the
release of a wide array of air pollutants, some of which exist in the
waste feed material and are released unchanged during combustion, and
some of which are generated as a result of the combustion process
itself. These pollutants include particulate matter (PM); heavy metals,
including lead (Pb), cadmium (Cd), and mercury (Hg); toxic organics,
including chlorinated dibenzo-p-dioxins/dibenzofurans (CDD/CDF); carbon
monoxide (CO); nitrogen oxides (NOX); and acid gases,
including hydrogen chloride (HCl) and sulfur dioxide (SO2).
In addition to the use of pollution prevention measures (i.e., waste
segregation) and good combustion control practices, HMIWI are typically
controlled by wet scrubbers or dry sorbent injection fabric filters
(dry scrubbers).
    Waste segregation is the separation of certain components of the
healthcare waste stream in order to reduce the amount of air pollution
emissions associated with that waste when incinerated. The separated
waste may include paper, cardboard, plastics, glass, batteries, or
metals. Separation of these types of wastes reduces the amount of
chlorine- and metal-containing wastes being incinerated, which results
in lower potential emissions of HCl, CDD/CDF, Hg, Cd, and Pb.
    Combustion control includes the proper design, construction,
operation, and maintenance of HMIWI to destroy or prevent the formation
of air pollutants prior to their release to the atmosphere. Test data
indicate that as secondary chamber residence time and temperature
increase, emissions decrease. Combustion control is most effective in
reducing CDD/CDF, PM, and CO emissions. The 2-second combustion level,
which includes a minimum secondary chamber temperature of 1800[deg]F
and residence time of 2 seconds, is considered to be the best level of
combustion control (i.e., good combustion) that is applied to HMIWI.
Wet scrubbers and dry scrubbers provide control of PM, CDD/CDF, HCl,
and metals, but do not influence CO, or NOX and have little
impact on SO2 at the low concentrations emitted by HMIWI.
(See Legacy Docket ID No. A-91-61, item II-A-111; 60 FR 10669, 10671-
10677; and 61 FR 31742-31743.)
    On September 15, 1997, EPA adopted NSPS (40 CFR part 60, subpart
Ec) and EG (40 CFR part 60, subpart Ce) for entities which operate
HMIWI. The NSPS and EG are designed to reduce air pollution emitted
from new and existing HMIWI, including HCl, CO, Pb, Cd, Hg, PM, CDD/CDF
(total, or 2,3,7,8-tetrachlorinated dibenzo-p-dioxin toxic equivalent
(TEQ)), NOX, SO2, and opacity. The NSPS apply to
HMIWI for which construction began after June 20, 1996, or for which
modification began after March 16, 1998. The NSPS became effective on
March 16, 1998, and apply as of that date or at start-up of a HMIWI,
whichever is later. The EG apply to HMIWI for which construction began
on or before June 20, 1996, and required compliance by September 2002.
    The CAA sets forth a two-stage approach to regulating emissions
from incinerators. EPA has substantial discretion to distinguish among
classes, types and sizes of incinerator units within a category while
setting standards. In the first stage of setting standards, CAA section
129(a)(2) requires EPA to establish technology-based emission standards
that reflect levels of control EPA determines are achievable for new
and existing units, after considering costs, non-air quality health and
environmental impacts, and energy requirements associated with the
implementation of the standards. Section 129(a)(5) then directs EPA to
review those standards and revise them as necessary every 5 years. In
the second stage, section 129(h)(3) requires EPA to determine whether
further revisions of the standards are necessary in order to provide an
ample margin of safety to protect public health. See, e.g., NRDC and
LEAN v. EPA, 529 F.3d 1077, 1079-80 (D.C. Cir. 2008) (addressing the
similarly required two-stage approach under CAA sections 112(d) and
(f), and upholding EPA's implementation of same).
    In setting forth the methodology EPA must use to establish the
first-stage technology-based NSPS and EG, CAA section 129(a)(2)
provides that standards ``applicable to solid waste incineration units
promulgated under section 111 and this section shall reflect the
maximum degree of reduction in emissions of [certain listed air
pollutants] that the Administrator, taking into consideration the cost
of achieving such emission reduction, and any non-air quality health
and environmental impacts and energy requirements, determines is
achievable for new and existing units in each category.'' This level of
control is referred to as a maximum achievable control technology, or
MACT standard.
    In promulgating a MACT standard, EPA must first calculate the
minimum stringency levels for new and existing solid waste incineration
units in a category, generally based on levels of emissions control
achieved or required to be achieved by the subject units. The minimum
level of stringency is called

the MACT ``floor,'' and CAA section 129(a)(2) sets forth differing
levels of minimum stringency that EPA's standards must achieve, based
on whether they regulate new and reconstructed sources, or existing
sources. For new and reconstructed sources, CAA section 129(a)(2)
provides that the ``degree of reduction in emissions that is deemed
achievable [* * *] shall not be less stringent than the emissions
control that is achieved in practice by the best controlled similar
unit, as determined by the Administrator.'' Emissions standards for
existing units may be less stringent than standards for new units, but
``shall not be less stringent than the average emissions limitation
achieved by the best performing 12 percent of units in the category.''
    The MACT floors form the least stringent regulatory option EPA may
consider in the determination of MACT standards for a source category.
EPA must also determine whether to control emissions ``beyond-the-
floor,'' after considering the costs, non-air quality health and
environmental impacts, and energy requirements of such more stringent
control. EPA made such MACT floor and beyond-the-floor determinations
in the 1997 HMIWI rulemaking, and the Court remanded them in 1999 for
further explanation, leaving the standards in force in the meantime. As
mentioned above, every 5 years after adopting a MACT standard under
section 129, CAA section 129(a)(5) requires EPA to review and, if
appropriate, revise the incinerator standards. In addition to
responding to the Court's remand in Sierra Club v. EPA, 167 F.3d 658
(D.C. Cir. 1999), the proposed action constitutes the first 5-year
review of the HMIWI standards.

III. Summary

A. Litigation and Proposed Remand Response

1. What is EPA's general methodology for determining MACT?
    In general, all MACT analyses involve an assessment of the air
pollution control systems or technologies used by the better performing
units in a source category. The technology assessment can be based
solely on actual emissions data, on knowledge of the air pollution
control in place in combination with actual emissions data, or on State
regulatory requirements that may enable EPA to estimate the actual
performance of the regulated units. For each source category, the
assessment of the technology involves a review of actual emissions data
with an appropriate accounting for emissions variability. Where there
is more than one method or technology to control emissions, the
analysis may result in a series of potential regulations (called
regulatory options), one of which is selected as MACT.
    Each regulatory option EPA may consider must be at least as
stringent as the CAA's minimum stringency ``floor'' requirements.
However, MACT is not necessarily the least stringent regulatory option.
EPA must examine, but is not necessarily required to adopt, more
stringent ``beyond-the-floor'' regulatory options to determine MACT.
Unlike the floor minimum stringency requirements, EPA must consider
various impacts of the more stringent regulatory options in determining
whether MACT standards are to reflect ``beyond-the-floor''
requirements. If EPA concludes that the more stringent regulatory
options have unreasonable impacts, EPA selects the ``floor-based''
regulatory option as MACT. But if EPA concludes that impacts associated
with ``beyond-the-floor'' levels of control are acceptable in light of
additional emissions reductions achieved, EPA selects those levels as
MACT.
    As stated earlier, the CAA requires that MACT for new sources be no
less stringent than the emissions control achieved in practice by the
best controlled similar unit. Under CAA section 129(a)(2), EPA
determines the best control currently in use for a given pollutant and
establishes one potential regulatory option at the emission level
achieved by that control with an appropriate accounting for emissions
variability. More stringent potential regulatory options might reflect
controls used on other sources that could be applied to the source
category in question.
    For existing sources, the CAA requires that MACT be no less
stringent than the average emissions limitation achieved by the best
performing 12 percent of units in a source category. EPA must determine
some measure of the average emissions limitation achieved by the best
performing 12 percent of units to form the floor regulatory option.
More stringent beyond-the-floor regulatory options reflect other or
additional controls capable of achieving better performance.
2. What was EPA's methodology in the 1997 HMIWI rulemaking?
    On February 27, 1995, EPA published a notice of proposed rulemaking
regarding emissions standards for HMIWI (60 FR 10654). The proposal was
the result of several years of reviewing available information. During
the public comment period for the proposal, EPA received new
information that led EPA to consider the need for numerous changes to
the proposed rule, and on June 20, 1996, the Agency published a re-
proposal (61 FR 31736). EPA published the final rule on September 15,
1997 (62 FR 48348).
    During the data-gathering phase of developing the 1995 proposal,
EPA found it difficult to obtain an accurate count of the thousands of
HMIWI that then operated nationwide, or to find HMIWI with add-on air
pollution control systems in place. A few HMIWI with combustion control
were tested to assess performance of combustion control in reducing
emissions. One unit with a wet scrubber, and a few units with dry
scrubbing systems were tested to determine performance capabilities of
add-on controls. (See 61 FR 31738.)
    Altogether, data were available from only 7 out of the estimated
then-operating 3,700 existing HMIWI (60 FR 10674). EPA developed the
proposed regulations with the existing data, but EPA specifically
requested comment on EPA's MACT determinations and on EPA's conclusions
about the performance capabilities of air pollution control
technologies on HMIWI in light of the relatively small database (60 FR
10686).
    a. EPA's Methodology in the 1997 Rulemaking for New HMIWI. In
determining the MACT floor for new HMIWI in the 1997 rulemaking, EPA
first examined the data available for various air pollution control
technologies applied to HMIWI to determine the performance capabilities
of the technologies (60 FR 10671-73, 61 FR 31741-43). To determine the
performance capabilities, EPA grouped all of the test data by control
technology and established the numerical value for corresponding
emission limitations somewhat higher than the highest test data point
for each particular control technology. (See Legacy Docket ID No. A-91-
61, items IV-B-46, 47, 48, and 49.) Following the determination of
performance capability, EPA identified the best control technology for
each air pollutant for each subcategory of HMIWI, and established the
numerical values for the floor regulatory option at the emission
limitation associated with that particular control technology. (See 60
FR 10673; Legacy Docket ID No. A-91-61, item IV-B-38; 61 FR 31745-46.)
Other, more stringent, beyond-the-floor regulatory options were
developed reflecting the actual performance of other, more effective,
control technologies (61 FR 31766-68).
    In EPA's 1997 final standards, EPA selected a regulatory option for
new HMIWI that was, overall, more stringent

than the identified MACT floor (62 FR 48365). The final standards were
based on emission limits achievable with good combustion and a
moderate-efficiency wet scrubber for new small HMIWI (units with
maximum waste burning capacity of less than or equal to 200 lb/hr), and
good combustion and a combined dry/wet control system with carbon for
new medium HMIWI (units with maximum waste burning capacity of more
than 200 lb/hr but less than or equal to 500 lb/hr) and new large HMIWI
(units with maximum waste burning capacity of more than 500 lb/hr). Id.
These standards reflected the MACT floor emissions levels for new small
and large HMIWI, but were more stringent than the MACT floor for new
medium HMIWI, based on the floor-determination methodology EPA used as
described above. Id. EPA estimated that the standards would reduce
emissions from these units of HCl by up to 98 percent, PM and Pb by up
to 92 percent, Cd by up to 91 percent, CDD/CDF by up to 87 percent, Hg
by up to 74 percent, and CO, SO2, and NOX by up
to 52 percent (62 FR 48366).
    b. EPA's Methodology in the 1997 Rulemaking for Existing HMIWI. For
existing units, EPA did not have sufficient emissions data to fully
characterize the actual emissions performance of the best performing 12
percent of existing HMIWI. Based exclusively on the data it did have,
EPA concluded that it did not have a clear indication of the technology
used by the best 12 percent of units. As a result, EPA used emission
limits included in State regulations and State-issued permits
(hereinafter referred to as regulatory limits) as surrogate information
to determine emissions limitations achieved by the best performing 12
percent of units in each subcategory (60 FR 10674). At that time, EPA
expected this information reflected levels of performance achieved on a
continuous basis by better-controlled units, since the units had to
meet these limits or risk violating enforceable requirements. EPA
assumed that all HMIWI were achieving their regulatory limits (60 FR
10674). Where there were regulatory limits for more than 12 percent of
units in a subcategory, the regulatory limits were ranked from the most
stringent to least stringent, and the average of the regulatory limits
for the top 12 percent of units in the subcategory was calculated. Id.;
61 FR 31744-45. Where the number of units subject to specific emissions
limitations did not comprise 12 percent of the population in a
subcategory, EPA assumed those units with regulatory limits were the
best performing units, and the remaining units in the top 12 percent
were assigned an emission value associated with ``combustion control.''
(See 60 FR 10674; 61 FR 31745; Legacy Docket ID No. A-91-61, item IV-B-
24 at 2.) In previous Federal Register notices regarding HMIWI (60 FR
10654, 61 FR 31736, and 62 FR 48348), this level of control was
referred to as ``uncontrolled,'' which is misleading because sources
with combustion control emit lesser amounts of CDD/CDF, CO, and PM than
would a truly ``uncontrolled'' source. Where regulatory limits did not
fill 12 percent of the source category, the average of the regulatory
limits plus enough combustion-controlled emission values to account for
12 percent of units in the subcategory was calculated. (See Legacy
Docket ID No. A-91-61, item IV-B-24 at 2-4.)
    After calculating the averages of regulatory limits and combustion-
controlled emission values, EPA examined the resulting calculated
values to determine what level of air pollution control would be needed
to meet the calculated average values. (See 60 FR 10675-78; 61 FR
31755-56.) For many pollutants, the calculated averages presented no
clear indication of the type of air pollution control used by the best
performing units. However, the calculated values for three key
pollutants, PM, CO, and HCl, did provide a good indication of the type
of air pollution control used on the best performing 12 percent of
units. The level of air pollution control associated with the
calculated average values for PM, CO, and HCl formed the technical
basis of the MACT floor regulatory option considered by EPA (61 FR
31756, Table 13). The emission limitations assigned to each pollutant
reflected the actual performance of the technology on which they were
based. Finally, EPA developed a series of regulatory options based on
progressively more stringent technologies and assigned emission
limitations to each regulatory option based on the actual performance
capabilities of the technologies (61 FR 31757, Table 14).
    In EPA's final standards promulgated in 1997, EPA selected a
regulatory option for existing HMIWI that was overall more stringent
than the floor, based on the floor determination methodology described
above (62 FR 48371). The final standards were based on emission limits
achievable with good combustion and a low-efficiency wet scrubber for
most existing small HMIWI, good combustion and a moderate-efficiency
wet scrubber for existing medium HMIWI, and good combustion and a high-
efficiency wet scrubber for existing large HMIWI (62 FR 48371). The
final standards allow small HMIWI that meet certain rural criteria to
meet emissions limits achievable with good combustion alone. Id. These
standards reflected the identified MACT floor emissions levels for
existing small HMIWI meeting rural criteria, medium HMIWI, and large
HMIWI, but were more stringent than the MACT floor for most existing
small HMIWI (i.e., non-rural), based on the methodology EPA used then
(62 FR 48371-72). The final standards for existing medium and large
HMIWI were structured so that either a dry scrubber or a wet scrubber
could be used to achieve the emission limits. EPA estimated that the
final EG would reduce emissions of CDD/CDF by up to 97 percent, Hg by
up to 95 percent, PM by up to 92 percent, Pb by up to 87 percent, Cd by
up to 84 percent, CO by up to 82 percent, HCl by up to 98 percent, and
SO2 and NOX by up to 30 percent (62 FR 48372).
Table 1 of this preamble summarizes the emission limits for the NSPS
and EG promulgated in 1997.

                                 Table 1--Summary of Promulgated Emission Limits
----------------------------------------------------------------------------------------------------------------
                                                                   Limit for existing
          Pollutant  (units)                Unit size \1\              HMIWI \2\         Limit for new HMIWI \2\
----------------------------------------------------------------------------------------------------------------
HCl (parts per million by volume       L, M, S................  100 or 93% reduction...  15 or 99% reduction
 (ppmv)).
                                       SR.....................  3,100..................  N/A \3\
CO (ppmv)............................  L, M, S................  40.....................  40
                                       SR.....................  40.....................  N/A
Pb (milligrams per dry standard cubic  L, M...................  1.2 or 70% reduction...  0.07 or 98% reduction
 meter (mg/dscm)).                                                                        \3\
                                       S......................  1.2 or 70% reduction...  1.2 or 70% reduction

                                       SR.....................  10.....................  N/A
Cd (mg/dscm).........................  L, M...................  0.16 or 65% reduction..  0.04 or 90% reduction
                                       S......................  0.16 or 65% reduction..  0.16 or 65% reduction
                                       SR.....................  4......................  N/A
Hg (mg/dscm).........................  L, M , S...............  0.55 or 85% reduction..  0.55 or 85% reduction
                                       SR.....................  7.5....................  N/A
PM (grains per dry standard cubic      L......................  0.015..................  0.015
 foot (gr/dscf)).
                                       M......................  0.03...................  0.015
                                       S......................  0.05...................  0.03
                                       SR.....................  0.086..................  N/A
CDD/CDF, total (nanograms per dry      L, M...................  125....................  25
 standard cubic meter (ng/dscm)).
                                       S......................  125....................  125
                                       SR.....................  800....................  N/A
CDD/CDF, TEQ (ng/dscm)...............  L, M...................  2.3....................  0.6
                                       S......................  2.3....................  2.3
                                       SR.....................  15.....................  N/A
NOX (ppmv)...........................  L, M, S................  250....................  250
                                       SR.....................  250....................  N/A
SO2 (ppmv)...........................  L, M, S................  55.....................  55
                                       SR.....................  55.....................  N/A
Opacity (%)..........................  L, M, S, SR............  10.....................  10
----------------------------------------------------------------------------------------------------------------
\1\ L = Large; M = Medium; S = Small; SR = Small Rural.
\2\ All emission limits are measured at 7 percent oxygen.
\3\ Not applicable.

    c. Compliance by HMIWI. At the time of promulgation (September
1997), EPA estimated that there were approximately 2,400 HMIWI still
operating in the United States. Those units combusted approximately 830
thousand tons of hospital/medical/infectious waste annually. Of those
existing HMIWI, about 48 percent were small units, 29 percent were
medium units, and 20 percent were large units. About 3 percent of the
HMIWI were commercial units. EPA projected that no new small or medium
HMIWI would be constructed, and that up to 60 new large units and 10
new commercial units would be constructed.
    After approximately 98 percent of the HMIWI that were operating in
1997 shut down or obtained exemptions, there remain only 52 existing
HMIWI at 47 facilities from the set of 2,400 that operated at
promulgation. Additionally, only 5 new HMIWI at 4 facilities began
operation following the 1997 rulemaking. The total 57 existing and new
units are estimated to combust approximately 146,000 tons of waste
annually. Of the 52 existing HMIWI subject to the EG, 33 are large
units, 16 are medium units, and 3 are small units (2 of which meet the
rural criteria). Twenty-three percent of the existing HMIWI (i.e., 14
units) are commercially owned. Of the five new HMIWI, three are large
units, one is a medium unit, and one is a small unit. Two of the new
units are county-owned but accept waste from other sources, similar to
commercial units. The actual emissions reductions achieved as a result
of implementation of the standards exceeded the 1997 projections for
all nine of the regulated pollutants. A comparison of the estimated
pollutant reductions versus the actual reductions is presented in Table
2 of this preamble.

            Table 2--Comparison of Estimated Pollutant Reductions Versus Actual Pollutant Reductions
----------------------------------------------------------------------------------------------------------------
                                                            Actual
                                   Estimated emissions     emissions    Emissions reduction  Emissions reduction
            Pollutant               reduction, percent    reduction,     due to  shutdowns/   due to  compliance
                                                          percent \1\        exemptions         with standards
----------------------------------------------------------------------------------------------------------------
HCl..............................  98.................            98.4  98.3...............  0.1
CO...............................  75 to 82...........            98.0  94.8...............  3.2
Pb...............................  80 to 87...........            98.2  95.9...............  2.3
Cd...............................  75 to 84...........            98.7  95.4...............  3.3
Hg...............................  93 to 95...........            97.8  94.6...............  3.2
PM...............................  88 to 92...........            95.6  92.8...............  2.9
CDD/CDF, total...................  96 to 97...........            99.4  97.3...............  2.0
CDD/CDF, TEQ.....................  95 to 97...........            99.4  97.2...............  2.2
                                                                       -----------------------------------------
NOX..............................  0 to 30............            56.7               see footnote 2
SO2..............................  0 to 30............            76.2               see footnote 2
----------------------------------------------------------------------------------------------------------------
\1\ Reflects the effect of unit shutdowns and exemptions that were obtained, as well as the effect of compliance
  with the promulgated standards.
\2\ Percentages cannot be accurately calculated because units were not required to conduct emissions testing for
  NOX and SO2.

3. What was the Sierra Club's challenge?
    On November 14, 1997, the Sierra Club and the Natural Resources
Defense Council (Sierra Club) filed suit in the U.S. Court of Appeals
for the District of Columbia Circuit (the Court). The Sierra Club
claimed that EPA violated CAA section 129 by setting emission standards
for HMIWI that are less stringent than required by section 129(a)(2);
that EPA violated section 129 by not including pollution prevention or
waste minimization requirements; and that EPA had not adequately
considered the non-air quality health and environmental impacts of the
standards. For new units, the Sierra Club argued that to satisfy the
statutory phrase ``best controlled similar unit'' in CAA section
129(a)(2), EPA should have identified the single best performing unit
in each subcategory and based the MACT floor on that particular unit's
performance, rather than consider the performance of other units using
the same technology. The Sierra Club also argued that EPA erroneously
based the new unit floors on the emissions of the worst performing unit
using a particular technology. Regarding existing units, the Sierra
Club claimed that CAA section 129(a)(2)'s words, ``average emissions
limitation achieved by the best performing 12 percent of units,''
preclude the use of regulatory data, and that the legislative history
reflects congressional intent to prohibit EPA from relying on
regulatory data. Moreover, the Sierra Club claimed that using
regulatory data was impossible because such data existed for fewer than
12 percent of HMIWI, and that using it impermissibly imported an
achievability requirement into the floor determination. Finally, the
Sierra Club argued that EPA failed to require HMIWI to undertake
programs to reduce the Hg and chlorinated plastic in their waste
streams, in violation of CAA section 129(a)(3).
4. What was the Court's ruling?
    On March 2, 1999, the Court issued its opinion in Sierra Club v.
EPA, 167 F.3d 658 (D.C. Cir. 1999). While the Court rejected the Sierra
Club's statutory arguments under CAA section 129, the Court remanded
the rule to EPA for further explanation regarding how EPA derived the
MACT floors for new and existing HMIWI. Furthermore, the Court did not
vacate the regulations, and the regulations remain in effect during the
remand.
    a. The Court's Ruling on New Units. Regarding EPA's treatment of
new units, the Court first opined that EPA would be justified in
setting the floors at a level that is a reasonable estimate of the
performance of the ``best controlled similar unit'' under the worst
reasonably foreseeable circumstances. The Court observed that if an
emissions standard is as stringent as ``the emissions control that is
achieved in practice'' by a particular unit, then that particular unit
will not violate the standard. But this would result only if ``achieved
in practice'' means ``achieved under the worst foreseeable
circumstances.'' The Court then stated that in National Lime Ass'n v.
EPA, 627 F.2d 416, 431 n. 46 (D.C. Cir. 1980), it held that where a
statute requires that a standard be ``achievable,'' it must be
achievable ``under most adverse circumstances which can reasonably be
expected to recur,'' and the same principle should apply when a
standard is to be derived from the operating characteristics of a
particular unit. Sierra Club v. EPA, 167 F.3d at 665.
    The Court refused to rule that EPA's approach of considering
emissions of units other than the single best controlled unit was
unlawful, and suggested that considering all units with the same
technology might be a justifiable way to predict the worst reasonably
foreseeable performance of the best unit. The Court also supposed that
EPA may have considered all units with the same technology equally
``well-controlled,'' so that each unit with the best technology is a
``best-controlled unit'' even if they vary in performance. Sierra Club
v. EPA, 167 F.3d at 665.
    However, the Court concluded that the possible rationale for this
treatment of new units was not presented in the rulemaking record with
enough clarity for the Court to determine that EPA's path may
reasonably be discerned, and that EPA had not explained why the phrase
best controlled similar unit could encompass all units using the same
technology as the unit with the best observed performance, rather than
just the single best unit. Sierra Club v. EPA, 167 F.3d at 665. The
Court further directed EPA to provide additional explanation regarding
how the Agency had calculated the upper bound of the best-controlled
unit's performance through rounding. Id.
    b. The Court's Ruling on Existing Units. With respect to existing
units, the Court first rejected the Sierra Club's statutory objections
to using regulatory data and ``uncontrolled'' (i.e., combustion-
controlled) emissions values. Then, after analyzing and rejecting the
Sierra Club's arguments that the plain language of the CAA and its
legislative history forbid EPA's methodology, the Court held that the
use of regulatory data is permissible as long as it allows a reasonable
inference as to the performance of the top 12 percent of units.
Similarly, as long as there is a reasonable basis for concluding that
some of the best performing 12 percent of units are combustion
controlled, EPA may include data points giving a reasonable
representation of the performance of those units. Sierra Club v. EPA,
167 F.3d at 662, 663.
    However, the Court concluded that, although EPA said that it
believed the combination of regulatory and combustion-controlled data
gave an accurate picture of HMIWI performance, EPA did not account for
the possibility that HMIWI might be substantially overachieving the
permit limits, which would cause permit limits to be of little value in
estimating the top 12 percent of HMIWI performance. In addition, EPA
did not give a reason for assuming that HMIWI that were not subject to
permit requirements did not deploy emission controls of any sort. Id.,
at 663-664. The Court further questioned the rationality of EPA using
the highest of its test run data in cases where the regulatory data did
not alone comprise the necessary 12 percent. Id., at 664.
5. What was EPA's methodology in the 2007 proposed remand response?
    Following the 1999 remand of the HMIWI MACT floors in Sierra Club
v. EPA, but prior to EPA's February 6, 2007, proposed response to the
Court remand, the Court issued a series of rulings in other cases
addressing MACT rules that were relevant to and guided EPA's
development of the February 2007 proposed response regarding HMIWI.
Those rulings and their relevance are fully explained in sections
III.A.4.c. and IV.A. of the preamble to EPA's February 2007 proposal
(72 FR 5510). The first of these was Nat'l Lime Ass'n v. EPA, 233 F.3d
625 (D.C. Cir. 2000) (NLA II), which involved EPA's MACT standards
under CAA section 112(d) for portland cement manufacturing facilities.
In that case, the Sierra Club argued that EPA should have based its
estimate of the top performing 12 percent of sources on actual
emissions data. But the Court determined that EPA's approach of
selecting the median performing plant out of the best twelve percent of
the plants for which EPA had information and setting the floor at the
level of the worst performing plant in the database using the same
technology as the median plant had not been shown to be unreasonable.
NLA II, 233 F.3d at 633.
    In addition, the Court partially clarified its position regarding
EPA's approach of accounting for emissions

performance variability by setting floors at a level that reasonably
estimates the performance of the ``best controlled similar unit'' under
the worst reasonably foreseeable circumstances. First, the Court
stressed that EPA should not simply set floors at levels reflecting the
worst foreseeable circumstances faced by any worst performing unit in a
given source category. Second, the Court stated that considering all
units with the same technology may be a justifiable way to predict the
worst reasonably foreseeable performance of such technology only if
pollution control technology were the only factor determining emission
levels of that HAP. NLA II, 233 F.3d at 633.
    In Cement Kiln Recycling Coalition v. EPA, 255 F.3d 855 (D.C. Cir.
2001) (CKRC), the Court again addressed when it is appropriate for EPA
to base MACT floors on the performance of air pollution control
technology. The Sierra Club challenged EPA's MACT standards for
hazardous waste combustors (HWC), and argued that factors other than
MACT technology influenced the emissions performance of the best
performing sources.
    The Court agreed that since the HWC rulemaking record showed that
factors besides technological controls significantly influenced HWC
emission rates, emissions of the worst-performing source using
technology may not reflect what the best-performers actually achieve.
CKRC, 255 F.3d at 864. EPA had claimed that MACT floors must be
achievable by all sources using MACT technology, and that to account
for the best-performing sources' operational variability we had to base
floors on the worst performers' emissions. But the Court stressed that
whether variability in the control technology accurately estimates
emissions variability of the best performing sources depends on whether
factors other than technological control contribute to emissions. The
Court stated that the relevant question is whether the variability
experienced by the best-performing sources can be estimated by relying
on emissions data from the worst-performing sources using technological
controls. Id., at 865. However, the Court also reiterated that if the
Agency can demonstrate with substantial evidence that MACT technology
significantly controls emissions, or that factors other than
technological control have a negligible effect, the MACT approach could
be a reasonable means of satisfying the statute's requirements. Id., at
866.
    EPA's February 2007 proposed response to the HMIWI remand was based
on a reassessment of information and data that were available at the
time of promulgation in 1997, in light of the Agency's understanding of
the Court's rulings in the Sierra Club, NLA II, CKRC and other cases
discussed in our 2007 proposal notice. The proposed response would have
revised some of the emission limits in both the NSPS and EG. Relative
to the NSPS, the emission limits for CO, Pb, Cd, Hg, PM, and CDD/CDF
would have been revised. Relative to the EG, the emission limits for
HCl, Pb, Cd, and CDD/CDF would have been revised. EPA believed that the
revised emission limits proposed in February 2007 as a result of its
response to the remand could be achieved with the same emission control
technology currently used by HMIWI to meet the 1997 rule.
    a. EPA's Methodology in the 2007 Proposal for New HMIWI. The
revised standards for new HMIWI in the 2007 proposal were based on the
same technologies upon which the 1997 final standards were based. In
general, we proposed emission limits for each air pollutant for each
subcategory of new HMIWI based on the highest observed data points
associated with the control technologies upon which the emission
standards were based, since we identified the ``best controlled similar
unit'' as one using the relevant control technologies for each
subcategory of new units. This was a similar MACT determination
approach to that used at the time of promulgation, with two significant
differences--the proposed limits did not include the addition of 10
percent to the highest observed emissions levels, nor did it include
the rounding up of those figures. The 2007 proposal's revised MACT
determination approach for new HMIWI and its rationale were explained
in detail in section IV.A.1. of the preamble to EPA's February 2007
proposal (72 FR 5510).
    b. EPA's Methodology in the 2007 Proposal for Existing HMIWI.
Although the proposed revised standards for existing HMIWI in the 2007
proposal were generally based on the same technologies upon which the
1997 final standards were based, they also reflected a number of
changes to the MACT determination approach used at promulgation. In
determining the best performing existing HMIWI, regulatory limits that
reflected higher emissions levels than those corresponding to EPA's
combustion-controlled emission estimates were not used. Furthermore,
where actual emissions test data reflecting emissions performance were
available in the 1997 record, those data took precedence over other
types of data (i.e., regulatory limits or performance values) and were
the initial type of pollutant-specific values considered. Additionally,
where we had some indication that add-on controls may have been used
but there were no test data or regulatory limits for that source, we
did not use combustion-controlled emission estimates in the floor
calculations to represent the performance of those sources. Rather, an
average of the maximum dry and wet control system performance was
determined for each pollutant, and those values were added to the data
set towards comprising the best performing 12 percent. These default
performance values also were used where regulatory limits existed but
were higher than the default performance values.
    In the 2007 proposal, the average emission limitation achieved by
the best performing 12 percent of existing sources was determined using
the median as a measure of central tendency. This approach resulted in
the emission level that corresponds to that of the best performing 6
percent of sources (i.e., the 94th percentile) representing the MACT
floor control level. MACT floors for each pollutant within each
subcategory were based on this approach. We then determined the
technology associated with each ``average of the best-performing 12
percent'' value by comparing the average values to average performance
data for wet scrubbers, dry injection fabric filters (also known as dry
scrubbers), and combustion controls (no add-on air pollution controls).
The technology needed to meet the average values reflected the
technology used by the 94th percentile unit and served as the basis for
the proposed revised MACT floor.
    Numerical emission limits were determined by combining the
appropriate average emission value for each pollutant within each
subcategory of HMIWI with a variability factor. The 2002 compliance
test data for HMIWI were used in calculating pollutant-specific
variability factors. While these data were not available at the time of
promulgation of the 1997 rule, we believed that they were the best data
available in 2007 for providing a quantitative assessment of
variability of emissions from well-controlled HMIWI. To determine the
pollutant-specific variability factors, a statistical analysis was
conducted. Specifically, the emission limit for each pollutant was
determined based on the combination of actual emissions test data,
regulatory data, and estimated performance levels (as described
earlier) and a statistics-based variability factor calculated for each
pollutant. A detailed explanation of the 2007 proposed revised MACT
determination approach for existing

HMIWI and its rationale was set forth in section IV.A.2. of the
preamble to EPA's February 2007 proposal (72 FR 5510).
6. Why is EPA re-proposing a response to the remand?
    EPA's decision to re-propose its response to the Court's remand is
based on a number of factors, including further rulings by the U.S.
Court of Appeals that issued after our 2007 proposal was published. In
addition, public comments regarding the 2007 proposal raised issues
that, upon further consideration, we believe are best addressed through
a re-proposal. One issue regards the use of emission limits included in
State regulations and State-issued permits as surrogates for estimated
actual emissions limitations achieved. As previously stated, EPA used
regulatory limits in its MACT floor determinations supporting the 1997
rulemaking for HMIWI. At that time, we believed this information could
be expected to reliably reflect levels of performance achieved by HMIWI
on a continuous basis. In the 2007 proposed response to the Court's
remand, with adjustments to our methodology as described above, we
continued to use some of the regulatory limits to determine achieved
MACT floor emissions limitations. Upon reassessment of the regulatory
limits and minimal emissions test data in the 1997 record, however, it
is uncertain how well the regulatory limits represented the performance
of each HMIWI. Given the uncertainty regarding whether the regulatory
limits that specific HMIWI were subject to at the time of promulgation
provided a reasonable estimate of emissions limitations achieved by
those HMIWI, the inability to gather additional information regarding
non-operational units (approximately 98 percent shut down or obtained
exemptions), and the fact that we now have some actual emissions data
from the HMIWI remaining in operation, we believe the best course of
action is to re-propose a response to the remand based on data from the
57 currently operating HMIWI. This data is the most reliable we have
obtained that reflects the emissions levels achieved in practice by the
best performing HMIWI.
    Another issue regards EPA's previous reliance on control technology
performance as the sole indicator of HMIWI performance in making MACT
floor determinations, which did not necessarily account for other
factors that affect emissions (e.g., waste mix, combustion conditions).
Commenters on our 2007 proposal specifically asked that we revisit this
issue. Our treatment of this issue also addresses the Court's concern
with our 1997 rule's use of highest data points of units with best
performing technology, where control technology is not the only factor
that affects emissions. As we discuss in detail later in this notice,
although our work to-date in regulating HMIWI shows that control
technology significantly controls emissions, we are not able to
conclude that factors other than the controls have a negligible effect
on emissions performance and on the levels achieved in practice by the
best performing sources. While it is not possible to precisely quantify
the additional emissions reduction that is associated with waste
segregation or combustion conditions, we have found that it is possible
to account for those measures (and any other emission reduction
strategies) through the identification and use of actual emissions
levels in floor determinations, since these levels reflect emissions
performance resulting from the use of add-on controls and other
measures known to be used at HMIWI. Thus, the proposed revised MACT
emission limits are based on performance data from the best-performing
12 percent of existing HMIWI and the best-performing unit for new
HMIWI.
    Following publication of our 2007 proposed remand response, the
Court issued a ruling in another case challenging EPA's MACT
methodology, specifically as applied to brick and ceramic kilns. In
Sierra Club v. EPA, 479 F.3d 875 (D.C. Cir. 2007), the Court reiterated
its holding in CKRC that EPA may not justify MACT floors by claiming
that floors must be achievable by all sources using MACT technology.
Sierra Club v. EPA, 479 F.3d at 880. The Court concluded that by
excluding a certain control technology from the agency's ranking of
best-performing kilns, EPA had impermissibly ignored the emission
levels actually achieved by best performers in order to ensure that the
MACT floor is achievable by all kilns. Sierra Club, 479 F.3d at 880-81.
    The Court then referred to its ruling in CKRC declaring unlawful
EPA's method of estimating emissions among best performing sources by
basing MACT floors on levels achieved by worst performers using MACT
technology, and held that in the kilns rule EPA failed to show that the
emission levels achieved by the worst performers using a given
pollution control device actually predict the range of emission levels
achieved by the best performers using that device. Sierra Club, 479
F.3d at 882. The Court distinguished EPA's approach to kilns from the
permissible approach the agency had performed in Mossville
Environmental Action Now v. EPA, 370 F.3d 1232 (D.C. Cir. 2004), in
which EPA's record evidence demonstrated that the floor reasonably
estimated actual emissions variability of the best-performing sources.
There, the Court held that MACT floors may legitimately account for
variability because each source must meet the specified standard every
day and under all operating conditions. Mossville, 370 F.3d at 1242.
    The Sierra Club Court then addressed EPA's approach to considering
non-technology factors in the brick and ceramic kiln rule. The Court
stressed that EPA may not refuse to consider such factors in the MACT
floor merely because it is impossible to reliably quantify their effect
on emissions performance. Consequently, the Court rejected EPA's
approach in the kiln rule, in which the agency acknowledged that a non-
technology factor (clay type) had an appreciable effect on emissions
but for which EPA lacked data to quantify such effects. Sierra Club,
479 F.3d at 882-83. The Court further rejected EPA's argument that
since the non-technology factor in the kiln rule did not reflect a
deliberate step taken to reduce emissions, it did not amount to an
emission control or limitation achieved by kilns: The Court stated that
NLA II requires neither an intentional action nor a deliberate strategy
to reduce emissions, and that the Clean Air Act requires the EPA to set
MACT floors based upon the ``average emission limitation[s] achieved''
without suggesting that this achievement must be the product of a
specific intent. Sierra Club, 479 F.3d at 883.
    The Court's treatment of each of these issues caused us to reassess
our MACT floor approach in the HMIWI remand response.
7. Are the emission limits being revised as a result of the re-
proposal?
    Yes, the proposed response to the remand would revise all of the
emission limits in both the NSPS and EG. Table 3 of this preamble
summarizes the emission limits being proposed in this action in
response to the Court remand for new HMIWI.

 Table 3--Summary of Emission Limits Proposed in Response to the Remand
                              for New HMIWI
------------------------------------------------------------------------
                                                             Proposed
                                                  Unit        remand
              Pollutant  (units)                size \1\     response
                                                             limit \2\
------------------------------------------------------------------------
HCl (ppmv)....................................         L         0.75
                                                      M          1.8
                                                      S          4.5

CO (ppmv).....................................         L         2.9
                                                      M          1.9
                                                      S          8.2
Pb (mg/dscm)..................................         L         0.00047
                                                      M          0.016
                                                      S          0.18
Cd (mg/dscm)..................................         L         0.00012
                                                      M          0.0071
                                                      S          0.012
Hg (mg/dscm)..................................         L         0.00093
                                                      M          0.0020
                                                      S          0.0075
PM (gr/dscf)..................................         L         0.0048
                                                      M          0.0099
                                                      S          0.017
CDD/CDF, total (ng/dscm)......................         L         0.60
                                                      M          0.35
                                                      S          8.3
CDD/CDF, TEQ (ng/dscm)........................         L         0.014
                                                      M          0.0097
                                                      S          0.0080
NOX (ppmv)....................................         L       110
                                                   M, S         38
SO2 (ppmv)....................................         L         1.9
                                                   M, S          0.78
Opacity (%)...................................         L, M, S  2
------------------------------------------------------------------------
\1\ L = Large; M = Medium; S = Small
\2\ All emission limits are measured at 7 percent oxygen.

    Table 4 of this preamble summarizes the emission limits being
proposed in this action in response to the Court remand for existing
HMIWI.

 Table 4--Summary of Emission Limits Proposed in Response to the Remand
                           for Existing HMIWI
------------------------------------------------------------------------
                                                             Proposed
                                                  Unit        remand
              Pollutant  (units)                size \1\     response
                                                             limit \2\
------------------------------------------------------------------------
HCl (ppmv)....................................         L          2.4
                                                      M           2.5
                                                      S           4.5
                                                     SR         440
CO (ppmv).....................................         L          3.9
                                                      M           3.0
                                                      S           8.2
                                                     SR          12
Pb (mg/dscm)..................................         L          0.013
                                                      M           0.017
                                                      S           0.18
                                                     SR           0.35
Cd (mg/dscm)..................................         L          0.0041
                                                      M           0.0071
                                                      S           0.012
                                                     SR           0.068
Hg (mg/dscm)..................................         L          0.0095
                                                      M           0.0079
                                                      S           0.0075
                                                     SR           0.0040
PM (gr/dscf)..................................         L          0.0056
                                                      M           0.012
                                                      S           0.017
                                                     SR           0.030
CDD/CDF, total (ng/dscm)......................         L          1.6
                                                      M           0.63
                                                      S           8.3
                                                     SR         130
CDD/CDF, TEQ (ng/dscm)........................         L          0.029
                                                      M           0.0097
                                                      S           0.0080
                                                     SR           2.6
NOX (ppmv)....................................         L        140
                                                   M, S         200
                                                     SR         110
SO2 (ppmv)....................................         L, M, S    2.8
                                                     SR          43
Opacity (%)...................................         L, M, S,  2
                                                     SR
------------------------------------------------------------------------
\1\ L = Large; M = Medium; S = Small; SR = Small Rural
\2\ All emission limits are measured at 7 percent oxygen.

B. Proposed CAA Section 129(a)(5) 5-Year Review Response

    Section 129(a)(5) of the CAA requires EPA to conduct a review of
the NSPS and EG at 5 year intervals and, in accordance with sections
129 and 111, revise the NSPS and EG. We do not interpret section
129(a)(5), together with section 111, as requiring EPA to recalculate
MACT floors in connection with this periodic review. See, e.g., 71 FR
27324, 27327-28 (May 10, 2006) (``Standards of Performance for New
Stationary Sources and Emission Guidelines for Existing Sources: Large
Municipal Waste Combustors; Final Rule''); see also, NRDC and LEAN v.
EPA, 529 F.3d 1077, 1083-84 (D.C. Cir. 2008) (upholding EPA's
interpretation that the periodic review requirement in CAA section
112(d)(6) does not impose an obligation to recalculate MACT floors).
    Rather, in conducting such periodic reviews, EPA attempts to assess
the performance of and variability associated with control measures
affecting emissions performance at sources in the subject source
category (including the installed emissions control equipment), along
with developments in practices, processes and control technologies, and
determines whether it is appropriate to revise the NSPS and EG. This is
the same general approach taken by EPA in periodically reviewing CAA
section 111 standards, as section 111 contains a similar review and
revise provision. Specifically, section 111(b)(1)(B) requires EPA,
except in specified circumstances, to review NSPS promulgated under
section 111 every 8 years and to revise the standards if EPA determines
that it is ``appropriate'' to do so, 42 U.S.C. 7411(b)(1)(B). In light
of the explicit reference in section 129(a)(5) to section 111, which
contains direct guidance on how to review and revise standards
previously promulgated, EPA reasonably interprets section 129(a)(5) to
provide that EPA must review and, if appropriate, revise section 129
standards.
    Section 129 provides guidance on the criteria to be used in
determining whether it is appropriate to revise a section 129 standard.
Section 129(a)(3) states that standards under sections 111 and 129
``shall be based on methods and technologies for removal or destruction
of pollutants before, during and after combustion.'' It can be
reasonably inferred from the reference to ``technologies'' that EPA is
to consider advances in technology, both as to their effectiveness and
their costs, as well as the availability of new technologies, in
determining whether it is ``appropriate'' to revise a section 129
standard. This inference is further supported by the fact that the
standards under review are based, in part, on an assessment of the
performance of control technologies currently being used by sources in
a category or subcategory.
    This approach is also consistent with the approach used in
establishing and updating NSPS under section 111. Consistent with the
definition of ``standard of performance'' in section 111(a)(1),
standards of performance promulgated under section 111 are based on
``the best system of emission reductions'' which generally equates to
some type of control technology. Where EPA determines that it is
``appropriate'' to revise section 111 standards, section 111(b)(1)(B)
directs that this be done ``following the procedure required by this
subsection for promulgation of such standards.'' In updating section
111 standards in accordance with section 111(b)(1)(B), EPA has
consistently taken the approach of evaluating advances in existing
control technologies, both as to performance and cost, as well as the
availability of new technologies and then, on the basis of this
evaluation, determined whether it is appropriate to revise the
standard. See, for example, 71 FR 9866 (Feb. 27, 2006) (updating the
boilers NSPS) and 71 FR 38482 (July 6,

2006) (updating the stationary combustion turbines NSPS). In these
reviews, EPA takes into account, among other things, the currently
installed equipment and its performance and operational variability. As
appropriate, we also consider new technologies and control measures
that have been demonstrated to reliably control emissions from the
source category.
    The approach is similar to the one that Congress spelled out in
section 112(d)(6), which is also entitled ``Review and revision.''
Section 112(d)(6) directs EPA to every 8 years ``review, and revise as
necessary (taking into account developments in practices, processes,
and control technologies)'' emission standards promulgated pursuant to
section 112. There are a number of significant similarities between
what is required under section 129, which addresses emissions of
hazardous air pollutants (HAP) and other pollutants from solid waste
incineration units, and section 112, which addresses HAP emissions
generally. For example, under both section 112(d)(3) and section
129(a)(2) initial standards applicable to existing sources ``shall not
be less stringent than the average emissions limitation achieved by the
best performing 12 percent of units in the category.'' Also, as stated
above, both sections require that standards be reviewed at specified
intervals of time. Finally, both sections contain a provision
addressing ``residual risk'' (sections 112(f) and 129(h)(3)). As a
result, EPA believes that section 112(d)(6) is relevant in ascertaining
Congress' intent regarding how EPA is to proceed in implementing
section 129(a)(5).
    Like its counterpart CAA section 112(d)(6), section 129(a)(5) does
not state that EPA must conduct a MACT floor analysis every 5 years
when reviewing standards promulgated under sections 129(a)(2) and 111.
Had Congress intended EPA to conduct a new floor analysis every 5
years, it would have said so expressly by directly incorporating such
requirements into section 129(a)(5), for example by referring directly
to section 129(a)(2), rather than just to ``this section'' and section
111. It did not do so, however, and, in fact, section 129 encompasses
more than just MACT standards under section 129(a)(2)--it also includes
risk-based standards under section 129(h)(3), which are not determined
by an additional MACT analysis. Reading section 129(a)(5) to require
recalculation of the MACT floor would be both inconsistent with
Congress' express direction that EPA should revise section 129
standards in accordance with section 111, which plainly provides that
such revision should occur only if we determine that it is
``appropriate'' to do so. It would also result in effectively reading
the reference to section 111 out of the Act, a circumstance that
Congress could not have intended. Required recalculation of floors
would completely eviscerate EPA's ability to base revisions to section
129 standards on a determination that it is ``appropriate'' to revise
such standards, as EPA's only discretion would be in deciding whether
to establish a standard that is more stringent than the recalculated
floor. EPA believes that depriving the agency of any meaningful
discretion in this manner is at odds with what Congress intended.
    Further, required recalculation of floors would have the inexorable
effect of driving existing sources to the level of performance
exhibited by new sources on a 5-year cycle, a result that is
unprecedented and that should not be presumed to have been intended by
Congress in the absence of a clear statement to that effect. There is
no such clear statement. It is reasonable to assume that if the floor
must be recalculated on a 5-year cycle, some, if not most or all, of
the sources that form the basis for the floor calculation will be
sources that were previously subject to standards applicable to new
sources. As a result, over time, existing sources which had not made
any changes in their operations would eventually be subject to
essentially the same level of regulation as new sources. Such a result
would be unprecedented, particularly in the context of a standard that
is established under both sections 129 and 111. Under section 111, an
existing source only becomes a new source and thus subject to a new
source standard when it is either modified (section 111(a)(2)) or
reconstructed (40 CFR 60.15). Given this context, it is not reasonable
to assume that Congress intended for existing sources subject to
section 129 standards to be treated as new sources over time where
their circumstances have not changed.
    We believe that a reasonable interpretation of section 129(a)(5) is
that Congress preserved EPA's discretion in reviewing section 129
standards to revise them when the Agency determines it is
``appropriate'' to do so, and that the D.C. Circuit's recent ruling
regarding section 112(d)(6) supports this view (see NRDC and LEAN v.
EPA, 529 F.3d 1077, 1084 (D.C. Cir. 2008). In that case, petitioners
had ``argued that EPA was obliged to completely recalculate the maximum
achievable control technology--in other words, to start from scratch.''
NRDC and LEAN, 529 F.3d at 1084. The Court held: ``We do not think the
words `review, and revise as necessary' can be construed reasonably as
imposing any such obligation.'' Id. The Court's ruling in NRDC and LEAN
is consistent with our interpretation of section 129(a)(5) as providing
a broad range of discretion in terms of whether to revise MACT
standards adopted under sections 129(a)(2) and 111.
1. What was EPA's Approach in the 2007 Proposal Regarding the 5-Year
Review Requirement?
    In the 2007 proposed response to the Court's remand, EPA also
proposed amendments that reflected changes determined to be appropriate
after completing the 5-year review. Following compliance with the EG in
2002, EPA gathered information on the performance levels actually being
achieved by HMIWI that were operating under the guidelines. Those HMIWI
that remained in operation either continued operation with their
existing configuration or were retrofitted with add-on air pollution
control devices in order to meet the 1997 standards. The 2002
compliance test information provided the first quantitative assessment
of the performance of the installed control equipment's ability to
attain the NSPS and EG limits. The compliance data indicated that the
control technologies that were installed and the practices that were
implemented to meet the 1997 NSPS and EG achieved reductions somewhat
superior to what we had expected, based on the regulatory data we had
used to establish the limits, under the 1997 limits for many of the
pollutants.
    EPA used the compliance test data to develop the revised emission
limits proposed in February 2007 in response to the 5-year review
requirement. The proposed amendments did not reflect adoption of new
control technologies or processes, but reflected more efficient
practices in operation of the control technologies that sources used in
order to meet the 1997 MACT standards. The proposed amendments also
would have resulted in some changes to the performance testing and
monitoring requirements based on information received during
implementation of the HMIWI NSPS and EG. EPA's approach was explained
in detail in sections III.B. and IV.B. of the preamble to EPA's
February 2007 proposal (72 FR 5510).
    We did not regard the proposed revised amendments under the 5-year
review as reflecting a recalculation of the MACT floors for their own
sake, or, as some have put it, ``MACT-on-MACT.'' Rather, consistent
with our

overall interpretation of the requirements of section 129(a)(5), the
proposed revised amendments reflected what we viewed as a more accurate
translation into numeric emissions rates of the emissions performance
achieved by the MACT technological controls we had identified in the
1997 final rule. This seemed a reasonable approach, since we now had,
for the first time, actual emissions data that indicated the emissions
levels achieved through application of the MACT technology, rather than
just the regulatory data and combustion-control emissions factors to
which we have been previously limited, and which, as discussed above,
we have since learned did not provide the most accurate estimation of
the emissions levels achieved by the best performing sources.
2. Why is EPA Re-Proposing Different Revised Standards under the 5-Year
Review?
    Although we believe that the approach used in our 2007 proposed
response to the 5-year review of the HMIWI emission standards, as
promulgated in 1997, correctly addressed the intent of the CAA section
129(a)(5) requirement and resulted in proposed revisions to the
emission standards that would have appropriately reflected the
emissions levels achieved by the control technologies imposed by the
1997 final rule, we are re-proposing our response to the remand in
Sierra Club such that the proposed revised MACT standards, reflecting
floor levels determined by actual emissions data, would be more
stringent than what we proposed in 2007 for both the remand response
and the 5-year review, with the exceptions noted and discussed in
sections IV.A. and IV.B of this preamble. Consequently, we believe that
our obligation to conduct a 5-year review based on implementation of
the 1997 emission standards will also be fulfilled through this
action's re-proposal of the remand response. This is supported by the
fact that the revised MACT floor determinations and emission limits
associated with the remand response are based on performance data for
the 57 currently operating HMIWI that are subject to the 1997
standards, and by the re-proposal's accounting for non-technology
factors that affect HMIWI emissions performance, which the 2007
proposed remand response and 5-year review did not fully consider.
Thus, the proposed remand response more than addresses the technology
review's goals of assessing the performance efficiency of the installed
equipment and ensuring that the emission limits reflect the performance
of the technologies required by the MACT standards. In addition, the
proposed remand response addresses whether new technologies and
processes and improvements in practices have been demonstrated at
sources subject to the emissions limitations. Accordingly, the remand
response in this proposed action fulfills EPA's obligations regarding
the first 5-year review of the HMIWI standards and, therefore, replaces
the 2007 proposal's 5-year review proposed revisions.

C. Other Proposed Amendments

    This proposed action puts forward the same changes based on
information received during implementation of the HMIWI NSPS and EG
that were proposed in 2007. The proposal also includes additional
changes regarding requirements for NOX and SO2 emissions
testing for all HMIWI, performance testing requirements for small rural
HMIWI, monitoring requirements for HMIWI that install selective non-
catalytic reduction (SNCR) technology to reduce NOX
emissions, and procedures for test data submittal. A summary of these
changes follows.
1. Performance Testing and Monitoring Amendments
    The proposed amendments would require all HMIWI to demonstrate
initial compliance with the revised NOX and SO2
emission limits. Testing and demonstration of compliance with the
NOX and SO2 emission limits are not currently
required by the standards. In addition to demonstrating initial
compliance with the NOX and SO2 emission limits,
small rural HMIWI would be required to demonstrate initial compliance
with the other seven regulated pollutants' emission limits and the
opacity standard. Currently, small rural HMIWI are only required to
demonstrate initial compliance with the PM, CO, CDD/CDF, Hg, and
opacity standards. Small rural HMIWI also would be required to
determine compliance with the PM, CO, and HCl emission limits by
conducting an annual performance test. On an annual basis, small rural
HMIWI are currently required to demonstrate compliance with the opacity
limit. The proposed amendments would allow sources to use results of
their previous emissions tests to demonstrate initial compliance with
the proposed revised emission limits as long as the sources certify
that the previous test results are representative of current
operations. Only those sources who could not so certify and/or whose
previous emissions tests do not demonstrate compliance with one or more
revised emission limits would be required to conduct another emissions
test for those pollutants (note that most sources are already required
to test for HCl, CO, and PM on an annual basis, and those annual tests
are still required).
    The proposed amendments would require, for existing HMIWI, annual
inspections of scrubbers, fabric filters, and other air pollution
control devices that may be used to meet the emission limits, as well
as a one-time Method 22 of appendix A-7 visible emissions test of the
ash handling operations to be conducted during the next compliance
test. For new HMIWI, the proposed amendments would require CO
continuous emissions monitoring systems (CEMS), bag leak detection
systems for fabric-filter controlled units, annual inspections of
scrubbers, fabric filters, and other air pollution control devices that
may be used to meet the emission limits, as well as Method 22 visible
emissions testing of the ash handling operations to be conducted during
each compliance test. For existing HMIWI, use of CO CEMS would be an
approved alternative, and specific language with requirements for CO
CEMS is included in the proposed amendments. For new and existing
HMIWI, use of PM, HCl, multi-metals, and Hg CEMS, and integrated
sorbent trap Hg monitoring and dioxin monitoring (continuous sampling
with periodic sample analysis) also would be approved alternatives, and
specific language for those alternatives is included in the proposed
amendments. HMIWI that install SNCR technology to reduce NOX
emissions would be required to monitor the reagent (e.g., ammonia or
urea) injection rate and secondary chamber temperature.
2. Electronic Data Submittal
    Compliance test data are necessary for conducting 5-year reviews of
CAA section 129 standards, as well as for many other purposes including
compliance determinations, development of emission factors, and
determining annual emission rates. In conducting 5-year reviews, EPA
has found it burdensome and time consuming to collect emission test
data because of varied locations for data storage and varied data
storage methods. One improvement that has occurred in recent years is
the availability of stack test reports in electronic format as a
replacement for burdensome paper copies.
    In this action, we are taking a step to improve data accessibility.
HMIWI sources will have the option of submitting, to an EPA electronic
data base, an electronic copy of annual stack

test reports. Data entry requires only access to the internet and is
expected to be completed by the stack testing company as part of the
work that they are contracted to perform. This option would become
available as of December 31, 2011.
    Please note that the proposed option to submit source test data
electronically to EPA would not require any additional performance
testing. In addition, when a facility elects to submit performance test
data to WebFIRE, there would be no additional requirements for data
compilation; instead, we believe industry would greatly benefit from
improved emissions factors, fewer information requests, and better
regulation development as discussed below. Because the information that
would be reported is already required in the existing test methods and
is necessary to evaluate the conformance to the test method, facilities
would already be collecting and compiling these data. One major
advantage of electing to submit source test data through the Electronic
Reporting Tool (ERT), which was developed with input from stack testing
companies (who already collect and compile performance test data
electronically), is that it would provide a standardized method to
compile and store all the documentation required by this rule. Another
important benefit of submitting these data to EPA at the time the
source test is conducted is that it will substantially reduce the
effort involved in data collection activities in the future.
Specifically, because EPA would already have adequate source category
data to conduct residual risk assessments or technology reviews, there
would be fewer data collection requests (e.g., Section 114 letters).
This results in a reduced burden on both affected facilities (in terms
of reduced manpower to respond to data collection requests) and EPA (in
terms of preparing and distributing data collection requests). Finally,
another benefit of electing to submit these data to WebFIRE
electronically is that these data will greatly improve the overall
quality of the existing and new emissions factors by supplementing the
pool of emissions test data upon which the emission factor is based and
by ensuring that data are more representative of current industry
operational procedures. A common complaint we hear from industry and
regulators is that emissions factors are out-dated or not
representative of a particular source category. Receiving most
performance tests would ensure that emissions factors are updated and
more accurate. In summary, receiving these test data already collected
for other purposes and using them in the emissions factors development
program will save industry, state/local/tribal agencies, and EPA time
and money.
    The electronic data base that will be used is EPA's WebFIRE, which
is a Web site accessible through EPA's TTN. The WebFIRE Web site was
constructed to store emissions test data for use in developing emission
factors. A description of the WebFIRE data base can be found at http://
cfpub.epa.gov/oarweb/index.cfm?action=fire.main. The ERT will be able
to transmit the electronic report through EPA's Central Data Exchange
(CDX) network for storage in the WebFIRE data base. Although ERT is not
the only electronic interface that can be used to submit source test
data to the CDX for entry into WebFIRE, it makes submittal of data very
straightforward and easy. A description of the ERT can be found at
http://www.epa.gov/ttn/chief/ert/ert_tool.html. The ERT can be used to
document the conduct of stack tests data for various pollutants
including PM (EPA Method 5 of appendix A-3), SO2 (EPA Method
6C of appendix A-4), NOX (EPA Method 7E of appendix A-4), CO
(EPA Method 10 of appendix A-4), Cd (EPA Method 29 of appendix A-8), Pb
(Method 29), Hg (Method 29), and HCl (EPA Method 26A of appendix A-8).
Presently, the ERT does not handle dioxin/furan stack test data (EPA
Method 23 of appendix A-7), but the tool is being upgraded to handle
dioxin/furan stack test data. The ERT does not currently accept opacity
data or CEMS data.
    EPA specifically requests comment on the utility of this electronic
reporting option and the burden that owners and operators of HMIWI
estimate would be associated with this option.
3. Miscellaneous Other Amendments
    The proposed amendments would revise the definition of ``Minimum
secondary chamber temperature'' to read ``Minimum secondary chamber
temperature means 90 percent of the highest 3-hour average secondary
chamber temperature (taken, at a minimum, once every minute) measured
during the most recent performance test demonstrating compliance with
the PM, CO, and dioxin/furan emission limits.''
    The proposed amendments would require HMIWI sources to submit,
along with each test report, a description, including sample
calculations, of how operating parameters are established during the
initial performance test and, if applicable, re-established during
subsequent performance tests.

D. Proposed Implementation Schedule for Existing HMIWI

    Under the proposed amendments to the EG, and consistent with CAA
section 129, revised State plans containing the revised existing source
emission limits and other requirements in the proposed amendments would
be due within 1 year after promulgation of the amendments. That is,
revised State plans would have to be submitted to EPA 1 year after the
date on which EPA promulgates revised standards.
    The proposed amendments to the EG then would allow existing HMIWI
to demonstrate compliance with the amended standards within 3 years
from the date of approval of a State plan or 5 years after promulgation
of the revised standards, whichever is earlier. Consistent with CAA
section 129, EPA expects States to require compliance as expeditiously
as practicable. However, because we believe that many HMIWI will find
it necessary to retrofit existing emission control equipment and/or
install additional emission control equipment in order to meet the
proposed revised limits, EPA anticipates that States may choose to
provide the maximum compliance period allowed by CAA section 129(f)(2).
    In revising the emission limits in a State plan, a State would have
two options. First, it could include both the current and the new
emission limits in its revised State plan, which would allow a phased
approach in applying the new limits. That is, the State plan would make
it clear that the current emission limits remain in force and apply
until the date the new existing source emission limits are effective
(as defined in the State plan). States whose existing HMIWI do not find
it necessary to improve their performance in order to meet the revised
emission limits may want to consider a second approach where the State
would insert the revised emission limits in place of the current
emission limits, follow procedures in 40 CFR part 60, subpart B, and
submit a revised State plan to EPA for approval. If the revised State
plan contains only the revised emission limits (i.e., the current
emission limits are not retained), then the revised emission limits
must become effective immediately since the current limits would be
removed from the State plan.
    EPA will revise the existing Federal plan to incorporate any
changes to existing source emission limits and other requirements that
EPA ultimately promulgates. The Federal plan applies to HMIWI in any
State without an approved State plan. The proposed amendments to the EG
would allow

existing HMIWI subject to the Federal plan up to 5 years after
promulgation of the revised standards to demonstrate compliance with
the amended standards.

E. Proposed Changes to the Applicability Date of the 1997 NSPS

    HMIWI would be treated differently under the amended standards, as
proposed, than they were under the 1997 standards in terms of whether
they are ``existing'' or ``new'' sources, and there would be new dates
defining what are ``new'' sources and imposing compliance deadlines
regarding any amended standards. Since under this proposed rule the EG
for each pollutant and each subcategory would be more stringent than
the NSPS as promulgated in 1997, all NSPS units, with respect to the
standards as promulgated in 1997, would become ``existing'' sources
under the proposed amended standards and would be required to meet the
revised EG by the applicable compliance date for the revised
guidelines. However, those sources would continue to be NSPS units
subject to the standards as promulgated in 1997, until they become
``existing'' sources under the amended standards. Units for which
construction is commenced after the date of this proposal, or
modification is commenced on or after the date 6 months after
promulgation of the amended standards, would be ``new'' units subject
to more stringent NSPS emission limits than units for which
construction or modification was completed prior to those dates.
    Thus, under these specific proposed amendments, units that
commenced construction after June 20, 1996, and on or before December
1, 2008, or that are modified before the date 6 months after the date
of promulgation of any revised final standards, would continue to be or
would become subject to the 40 CFR part 60, subpart Ec NSPS emission
limits that were promulgated in 1997 until the applicable compliance
date for the revised EG, at which time those units would become
``existing'' sources. Similarly, EG units under the 1997 rule would
need to meet the revised EG by the applicable compliance date for the
revised guidelines. HMIWI that commence construction after December 1,
2008 or that are modified 6 months or more after the date of
promulgation of any revised standards would have to meet the revised
NSPS emission limits being added to the subpart Ec NSPS within 6 months
after the promulgation date of the amendments or upon startup whichever
is later.

IV. Rationale

A. Rationale for the Proposed Response to the Remand

    This action responds to the Court's remand by proposing a response
that is based on data from currently operating HMIWI. This proposed
action replaces the February 2007 proposal that responded to the remand
based on data in the public record that supported the 1997 HMIWI
rulemaking.
1. New HMIWI
    The Court raised three issues with regard to EPA's treatment of the
MACT floor for new units and the achievable emission limitations.
First, the Court asked EPA to explain why the floor was based on the
highest emissions levels of the ``worst-performing'' unit employing the
MACT technology rather than on the lowest observed emissions levels of
the best performing unit using the MACT technology. (See Sierra Club v.
EPA , 167 F.3d at 665.) Second, the Court requested further explanation
of why EPA considered multiple units employing the MACT technology,
rather than identify the single best-performing unit and basing the
floor on that particular unit's performance with that technology. Id.
Third, the Court requested further explanation of EPA's procedure for
determining the achievable emission limitation from the available data,
where EPA selected a numerical value somewhat higher than the highest
observed data point. Id.
    The methodology used to determine the MACT floor and proposed
revised emission limits for new HMIWI addresses the three issues raised
by the Court. The methodology that supports this action does not base
the MACT floor for new units on the highest emissions levels of the
``worst-performing'' unit employing the MACT technology, nor does it
consider multiple units employing the MACT technology. As explained in
section III of this preamble, EPA relied on control technology
performance as the sole indicator of unit performance in making MACT
floor determinations that supported the 1997 rulemaking as well as the
2007 proposal. However, based on recently obtained information, we now
understand that factors other than the controls (e.g., waste mix and
combustion conditions) affect HMIWI performance, and those emission
reduction strategies must be accounted for in MACT floor
determinations.
    In November 2007, we solicited information regarding waste
segregation practices from nine entities that own or operate HMIWI. The
nine entities chosen include various: (1) Types of facilities (i.e.,
hospitals, pharmaceutical operations, universities, and commercial
operations), (2) incinerator sizes (i.e., large, medium, and small
HMIWI), (3) incinerator ages (i.e., existing versus new), and (4)
control techniques (e.g., dry control systems, wet control systems, and
combustion controls). The responses to EPA's request for information
indicate that waste segregation is a common practice at HMIWI
facilities. Onsite waste segregation is practiced at the six hospitals,
the pharmaceutical facility, and the university that responded to the
questionnaire. Materials separated from the waste stream include
batteries, fluorescent light bulbs, paper and/or cardboard, glass, and
plastics. The commercial operations that dispose of waste generated
offsite indicated in their responses that they encourage waste
segregation from their clients through various efforts, including waste
management plans, contract requirements, and waste acceptance
protocols.
    a. Development of the MACT Floors and Proposed Emission Limits for
New Units. Section 129(a)(2) of the CAA requires that EPA determine the
emissions control that is achieved in practice by the ``best controlled
similar unit'' when establishing the MACT floors for new units. Section
129 requires EPA to develop standards based on emission levels already
achieved in practice by one or more units. Thus, the MACT floor for new
units is based on the ``emissions control'' that is attained by any
emission reduction strategies at the best similar unit. The use of
actual emissions levels in the MACT floor determinations supporting the
proposed emission limits for new HMIWI accounts for all emission
reduction strategies (i.e., add-on controls or other emission reducing
measures) used by individual HMIWI.
    MACT floors were determined for each air pollutant for each
subcategory of HMIWI using emissions data from the 57 currently
operating HMIWI. As explained in section III of this preamble, we
believe it is appropriate to re-propose a response to the remand based
on data from the currently operating HMIWI given the uncertainty
regarding the reliability of the regulatory limits for units operating
in 1997 and the lack of other more reliable data for those units. We
are retaining the large, medium, and small subcategories from the 1997
rulemaking. We continue to consider these subcategories to be
``classes'' of similar units in that all units within each ``class''
have been subject to the same regulatory requirements in the 1997 HMIWI
standards. Thus, when

determining MACT floors and proposed emission limits using data for
HMIWI within each ``class,'' we believe it is appropriate to continue
to apply those emission limits to HMIWI of similar size (e.g., data
from existing medium HMIWI would be used to determine emission limits
for new medium HMIWI).
    Within each subcategory and for each pollutant, EPA determined the
best performing HMIWI based on an examination of the average emissions
levels for each HMIWI. That is, the MACT floor for each pollutant is
based on one unit (i.e., the unit with the lowest average emissions
level). MACT floors for each pollutant within each subcategory, with
the exceptions of NOX and SO2 for small HMIWI,
were based on this approach. We do not have any NOX or
SO2 emissions data for the two small HMIWI because they have
not tested for NOX or SO2 and are not required to
do so by the 1997 HMIWI standards. Both small units use wet scrubbers.
The best performing medium HMIWI with respect to NOX and
SO2 use wet scrubbers as well. In both of these instances,
the NOX and SO2 emission limits being proposed
for new medium HMIWI also are being proposed for new small units.
Although use of data from the medium units does not account for any
control strategies in addition to the wet scrubbers being used by the
small units, we believe that using the NOX and
SO2 emission limits for new medium HMIWI as surrogate
emission limits for new small HMIWI is the most appropriate way to
address these two instances. A summary of the add-on control
technologies used, in addition to any other emission reductions
measures, by the single best performing HMIWI on a pollutant-specific
basis within each subcategory is presented in Table 5 of this preamble.

                    Table 5--Summary of Add-On Control Technologies for Best Performing HMIWI
----------------------------------------------------------------------------------------------------------------
              Pollutant                      Large HMIWI              Medium HMIWI             Small HMIWI
----------------------------------------------------------------------------------------------------------------
HCl..................................  Wet scrubber...........  Wet scrubber...........  Wet scrubber.
CO...................................  Wet scrubber...........  Dry scrubber...........  Wet scrubber.
Pb...................................  Carbon adsorber/wet      Dry scrubber...........  Wet scrubber.
                                        scrubber.
Cd...................................  Carbon adsorber/wet      Dry scrubber...........  Wet scrubber.
                                        scrubber.
Hg...................................   Fabric filter.........  Wet scrubber...........  Wet scrubber.
PM...................................  Dry scrubber...........  Dry scrubber...........  Wet scrubber.
CDD/CDF..............................  Dry scrubber...........  Wet scrubber...........  Wet scrubber.
NOX..................................  Carbon adsorber/wet      Wet scrubber...........  Wet scrubber.
                                        scrubber.
SO2..................................  Dry scrubber...........  Wet scrubber...........  Wet scrubber.
----------------------------------------------------------------------------------------------------------------

    We then used emissions data for those best performing HMIWI to
determine emission limits to be proposed, with an accounting for
variability. EPA must exercise its judgment, based on an evaluation of
the relevant factors and available data, to determine the level of
emissions control that has been achieved by the best performing HMIWI
under variable conditions. The Court has recognized that EPA may
consider variability in estimating the degree of emission reduction
achieved by best-performing sources and in setting MACT floors. See
Mossville Envt'l Action Now v. EPA, 370 F.3d 1232, 1241-42 (D.C. Cir
2004) (holding EPA may consider emission variability in estimating
performance achieved by best-performing sources and may set the floor
at level that best-performing source can expect to meet ``every day and
under all operating conditions'').
    MACT and other technology-based standards are necessarily derived
from short-term emissions test data, but such data are not
representative of the range of operating conditions that the best
performing facilities face on a day-to-day basis. In statistical terms,
each test produces a limited data sample, not a complete enumeration of
the available data for performance of the unit over a long period of
time. (See Natrella, Experimental Statistics, National Bureau of
Standards Handbook 91, chapter 1 (revised ed., 1966).) EPA, therefore,
often needs to adjust the short-term data to account for these varying
conditions. The types of variability that EPA attempts to account for
include operational distinctions between and within tests at the same
unit.
    ``Between-test variability'' can occur even where conditions appear
to be the same when two or more tests are conducted. Variations in
emissions may be caused by different settings for emissions testing
equipment, different field teams conducting the testing, differences in
sample handling, or different laboratories analyzing the results.
Identifying an achieved emissions level needs to account for these
differences between tests, in order for ``a uniform standard [to] be
capable of being met under most adverse conditions which can reasonably
be expected to recur[.]'' (See NLA I, 627 F.2d at 431, n. 46.) (See
also Portland Cement Ass'n, 486 F.2d at 396 (noting industry point that
``a single test offered a weak basis'' for inferring that plants could
meet the standards).)
    The same types of differences leading to between-test variability
also cause variations in results between various runs comprising a
single test, or ``within-test variability.'' A single test at a unit
usually includes at least three separate test runs. (See 40 CFR
63.7(e)(3) (for MACT standards under section 112 of the CAA), and 40
CFR 60.8(f) (for NSPS under CAA section 111).) Each data point should
be viewed as a snapshot of actual performance. Along with an
understanding of the factors that may affect performance, each of these
snapshots gives information about the normal, and unavoidable,
variation in emissions that would be expected to recur over time.
    To account for pollutant-specific variability at the best
performing HMIWI, we used emissions data for each test run conducted by
the best performing units. The amount of pollutant-specific test data
for the single best performing HMIWI within each subcategory varies
from 3 data points to 18 data points for large units; 3 data points to
21 data points for medium units; and 3 data points to 12 data points
for small units (excluding NOX and SO2 for which
there is no data for small units). Given the limited amount of test
data and the uncertainty regarding that short-term emissions test data,
we determined use of the 99.9 percent upper confidence level (UCL) to
be an appropriate method of estimating variability. The UCL represents
the statistical likelihood that a value, in this case an emission value
from the best performing source, will fall at or below the UCL value.
The average (or sample mean) and sample standard deviation, which are
two statistical measures calculated from the sample data, are used to
calculate the UCL. The average

is the central value of a data set and the standard deviation is the
common measure of the dispersion of the data set around the average.
The 99.9 percent UCL is appropriate for use in this analysis because
sources must meet the standards at all times, and as mentioned above,
the limited amount of test data introduces a degree of uncertainty.
    To calculate the achieved emission limit, including variability, we
used the equation: 99.9 percent UCL = mean + 3.09 * standard deviation.
The mean and standard deviation are based on the test runs for the
single best performing HMIWI for each pollutant. Accounting for
variability using the 99.9 percent UCL means: ``For each pollutant, the
performance of the best performing HMIWI, on average, is estimated to
meet (i.e., not exceed) the emission limit 99.9 percent of the time.''
The emission values adjusted for variability are presented with two
significant figures according to standard engineering practices, and
these values represent the MACT floor-based emission limits being
proposed. The second significant figure was rounded up to the next
place value. EPA has, at times, presented emission limits with either
two or three significant figures. For the low concentrations being
proposed, two significant figures provide the appropriate precision. In
all cases, the significant figure approach and associated rounding does
not meaningfully change the proposed emission limits.
    After determining the MACT floor-based emission limits for each
pollutant, EPA examined additional measures that could be taken to
further reduce emissions, but as discussed in section IV.A.1.b of this
preamble, EPA determined that these additional ``beyond-the-floor''
measures are not reasonable based on the high costs that would be
incurred and the minimal additional emissions reductions that could be
achieved. Therefore, all of the emission limits proposed in this action
for new HMIWI are based on the MACT floor level of control.
    A summary of the pollutant-specific average emissions associated
with the best performing HMIWI, the emission values adjusted for
variability, and the emission limits being proposed for new HMIWI are
presented in Table 6 of this preamble.

Table 6--Summary of Average Emission Values, Emission Values With Variability, and Emission Limits for New HMIWI
----------------------------------------------------------------------------------------------------------------
                                                                                Emission value
                                                                     Average          with           Proposed
               Pollutant (units)                  Unit size \1\  emission value    variability    emission limit
                                                                       \2\             \2\             \2\
----------------------------------------------------------------------------------------------------------------
HCl (ppmv).....................................               L        0.190           0.745             0.75
                                                              M        0.46            1.73              1.8
                                                              S        1.03            4.47              4.5
CO (ppmv)......................................               L        0.87            2.88              2.9
                                                              M        0.68            1.86              1.9
                                                              S        2.27            8.18              8.2
Pb (mg/dscm)...................................               L        0.000296        0.000470          0.47
                                                              M        0.0040          0.0154            0.016
                                                              S        0.073           0.174             0.18
Cd (mg/dscm)...................................               L        0.000106        0.000116          0.12
                                                              M        0.00106         0.00807       \3\ 0.0071
                                                              S        0.0026          0.0115            0.012
Hg (mg/dscm)                                                  L        0.000695        0.000925          0.00093
                                                              M        0.00084         0.00200           0.0020
                                                              S        0.00292         0.00742           0.0075
PM (gr/dscf)...................................               L        0.00106         0.00471           0.0048
                                                              M        0.00294         0.00983           0.0099
                                                              S        0.0076          0.0167            0.017
CDD/CDF, total (ng/dscm).......................               L        0.152           0.594             0.60
                                                              M        0.097           0.344             0.35
                                                              S        2.89            8.28              8.3
CDD/CDF, TEQ (ng/dscm).........................               L        0.0038          0.0135            0.014
                                                              M        0.00291         0.00972       \3\ 0.0097
                                                              S        0.00453         0.00792           0.0080
NOX (ppmv).....................................               L       66.9           101.0             110
                                                              M       15.0            37.8              38
                                                              S   \4\ 15.0        \4\ 37.8          \4\ 38
SO2 (ppmv).....................................               L        0.46            1.82              1.9
                                                              M        0.336           0.773             0.78
                                                              S    \4\ 0.336       \4\ 0.773         \4\ 0.78
----------------------------------------------------------------------------------------------------------------
\1\ L = Large; M = Medium; S = Small.
\2\ All values are measured at 7 percent oxygen.
\3\ Proposed emission limit reflects the proposed emission limit for existing HMIWI.
\4\ Emission value reflects data from best performing medium HMIWI.

    Using the procedure described above for Cd and CDD/CDF, TEQ for new
medium units would result in emission limits slightly less stringent
than the proposed emission limits for existing medium units. In these
two instances, the proposed emission limits have been lowered to
reflect the Cd and CDD/CDF, TEQ emission limits for existing medium
HMIWI. Cadmium has been lowered from 0.0081 mg/dscm to 0.0071 mg/dscm,
and CDD/CDF, TEQ has been lowered from 0.0098 ng/dscm to 0.0097 ng/
dscm. These are not significant differences that we are adjusting for
and the differences are functions of the emissions data and data
operations (e.g., statistical procedures). The adjustments, however,
are necessary such that the MACT standards for new sources are no less
stringent than the MACT standards for existing sources.
    Table 7 of this preamble summarizes the emission limits promulgated
in

1997, the emission limits proposed in 2007 in response to the Court's
remand, and the emission limits being proposed in this action in
response to the Court's remand for new HMIWI.

    Table 7--Summary of 1997 Promulgated Emission Limits, Emission Limits Proposed in 2007 in Response to the
          Remand, and Emission Limits Currently Being Proposed in Response to the Remand for New HMIWI
----------------------------------------------------------------------------------------------------------------
                                                                                Proposed
                                      Unit size                            Remand response limit      remand
          Pollutant (units)              \1\      Promulgated limit \2\    proposed in 2007 \2\   response limit
                                                                                \2\
----------------------------------------------------------------------------------------------------------------
HCl (ppmv)..........................          L  15 or 99% reduction....  15 or 99% reduction...         0.75
                                             M   15 or 99% reduction....  15 or 99% reduction...         1.8
                                             S   15 or 99% reduction....  15 or 99% reduction...         4.5
CO (ppmv)...........................          L  40.....................  25....................         2.9
                                             M   40.....................  25....................         1.9
                                             S   40.....................  25....................         8.2
Pb (mg/dscm)........................          L  0.07 or 98% reduction..  0.060 or 98% reduction         0.00047
                                             M   0.07 or 98% reduction..  0.060 or 98% reduction         0.016
                                             S   1.2 or 70% reduction...  0.64 or 71% reduction.         0.18
Cd (mg/dscm)........................          L  0.04 or 90% reduction..  0.030 or 93% reduction         0.00012
                                             M   0.04 or 90% reduction..  0.030 or 93% reduction         0.0071
                                             S   0.16 or 65% reduction..  0.060 or 74% reduction         0.012
Hg (mg/dscm)........................          L  0.55 or 85% reduction..  0.33 or 96% reduction.         0.00093
                                             M   0.55 or 85% reduction..  0.33 or 96% reduction.         0.0020
                                             S   0.55 or 85% reduction..  0.33 or 96% reduction.         0.0075
PM (gr/dscf)........................          L  0.015..................  0.0090................         0.0048
                                             M   0.015..................  0.0090................         0.0099
                                             S   0.03...................  0.018.................         0.017
CDD/CDF, total (ng/dscm)............          L  25.....................  20....................         0.60
                                             M   25.....................  20....................         0.35
                                             S   125....................  111...................         8.3
CDD/CDF, TEQ (ng/dscm)..............          L  0.6....................  0.53..................         0.014
                                             M   0.6....................  0.53..................         0.0097
                                             S   2.3....................  2.0...................         0.0080
NOX (ppmv)                                    L  250....................  212...................       110
                                          M, S   250....................  212...................        38
SO2 (ppmv)..........................          L  55.....................  28....................         1.9
                                          M, S   55.....................  28....................         0.78
----------------------------------------------------------------------------------------------------------------
\1\ L = Large; M = Medium; S = Small
\2\ All emission limits are measured at 7 percent oxygen.

    With one exception, the emission limits for new HMIWI being
proposed in this action are more stringent than the emission limits
proposed in 2007. The PM emission limit for new medium units being
proposed in this action is slightly higher than the limit proposed in
2007 (0.0090 gr/dscf versus 0.0099 gr/dscf). There are several
potential causes for this difference in emission limits. There are
three fewer medium HMIWI now, we have more emissions data to consider,
and, most importantly, the methodology used to determine the MACT
floors and emission limits in this action is different than in the 2007
proposal.
    b. Consideration of Options More Stringent Than the MACT Floor for
New HMIWI. After establishing the MACT floor emission level for each
pollutant for new sources, EPA is required to look ``beyond-the-floor''
at additional measures that that could be taken to further reduce
emissions, considering the cost of achieving such additional reduction
and any non-air quality health and environmental impacts and energy
requirements associated with imposing additional requirements. For each
subcategory, EPA looked for control measures not anticipated to be
required by the new source floors, and where options were identified,
EPA estimated costs of the options for a model unit in each
subcategory. For large units, SNCR was identified as a potential option
to reduce NOX emissions. For this beyond-the-floor option,
total NOX reductions for new large HMIWI are estimated at
7,900 lb/yr at a cost of $110,000 per year. For medium units, the floor
level of control includes all known measures for reducing emissions,
and, consequently, no beyond-the-floor options were identified. For
small units, addition of a dry injection fabric filter (DIFF) and
activated carbon injection were identified as potential options to
reduce emissions of lead, mercury, and dioxin. For this beyond-the-
floor option, the total cost for a new small HMIWI is $210,000, and EPA
estimates emissions reductions of 0.45 lb/yr of lead, 0.0073 lb/yr of
mercury, and 0.0091 grams/yr of total CDD/CDF. A memorandum entitled
``Analysis of Beyond-the-Floor Options'' is included in the docket, and
presents detailed results of the beyond-the-floor options, including
estimates of reductions of air pollutants, costs, and secondary