Document ID: EPA-HQ-OAR-2009-0234-20377
Agency: epa
Document Type: Proposed Rule
Title: Reconsideration of Certain Startup/Shutdown Issues: National Emission Standards for Hazardous Air Pollutants From Coal- and Oil-Fired Electric Utility Steam Generating Units, etc.
Posted Date: 2013-06-25T04:00Z

[Federal Register Volume 78, Number 122 (Tuesday, June 25, 2013)]
[Proposed Rules]
[Pages 38001-38005]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2013-15146]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 60 and 63

[EPA-HQ-OAR-2009-0234; EPA-HQ-OAR-2011-0044, FRL-9827-1]
RIN 2060-AR62

Reconsideration of Certain Startup/Shutdown Issues: National 
Emission Standards for Hazardous Air Pollutants From Coal- and Oil-
Fired Electric Utility Steam Generating Units and Standards of 
Performance for Fossil-Fuel-Fired Electric Utility, Industrial-
Commercial-Institutional, and Small Industrial-Commercial-Institutional 
Steam Generating Units

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule; Reopening of Comment Period.

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SUMMARY: On November 30, 2012, the EPA published in the Federal 
Register the proposed rule, ``Reconsideration of Certain New Source and 
Startup/Shutdown Issues: National Emission Standards for Hazardous Air 
Pollutants from Coal- and Oil-fired Electric Utility Steam Generating 
Units and Standards of Performance for Fossil-Fuel-Fired Electric 
Utility, Industrial-Commercial-Institutional, and Small Industrial-
Commercial-Institutional Steam Generating Units.'' That proposal opened 
for reconsideration certain issues, including those related to startup 
and shutdown. On April 24, 2013, we finalized reconsideration of all 
the issues included in the proposed rule except those related to 
startup and shutdown. The EPA is reopening the public comment period 
for the proposed reconsideration to solicit additional input on 
specific issues raised during the initial public comment period related 
to the proposed revisions to the requirements and definitions related 
to periods of startup and shutdown. The EPA also requests comment on 
the additional technical analyses it conducted in response to public 
comments on this subject in Docket ID EPA-HQ-OAR-2009-0234. The 
National Emission Standards for Hazardous Air Pollutants (NESHAP) rule 
is referred to as the Mercury and Air Toxics Standards (MATS), and the 
New Source Performance Standards rule is referred to as the Utility 
NSPS.

DATES: Comments. Comments must be received on or before August 26, 
2013.

ADDRESSES: Comments. Submit your comments, identified by Docket ID. 
EPA-HQ-OAR-2011-0044 (NSPS action) or Docket ID EPA-HQ-OAR-2009-0234 
(NESHAP/MATS action), by one of the following methods:
     www.regulations.gov: Follow the on-line instructions for 
submitting comments.
     Email: a-and-r-docket@epa.gov.
     Fax: (202) 566-1741.
     Mail: Air and Radiation Docket and Information Center, 
Environmental Protection Agency, Mailcode: 2822T, 1200 Pennsylvania 
Ave. NW., Washington, DC 20460. Please include a total of two copies. 
The EPA requests a separate copy also be sent to the contact person 
identified below (see FOR FURTHER INFORMATION CONTACT).
     Hand Delivery: Air and Radiation Docket and Information 
Center, U.S. EPA, Room B102, 1301 Constitution Avenue NW., Washington, 
DC. Such deliveries are only accepted during the Docket's normal hours 
of operation, and special arrangements should be made for deliveries of 
boxed information.
    Instructions. All submissions must include agency name and 
respective docket number or Regulatory Information Number (RIN) for 
this rulemaking. All comments will be posted without change and may be 
made available online at http://www.regulations.gov, including any 
personal information provided, unless the comment includes information 
claimed to be confidential business information (CBI) or other 
information

[[Page 38002]]

whose disclosure is restricted by statute. Do not submit information 
that you consider to be CBI or otherwise protected through http://www.regulations.gov or email. The http://www.regulations.gov Web site 
is an ``anonymous access'' system, which means the EPA will not know 
your identity or contact information unless you provide it in the body 
of your comment. If you send an email comment directly to the EPA 
without going through http://www.regulations.gov, your email address 
will be automatically captured and included as part of the comment that 
is placed in the public docket and made available on the Internet. If 
you submit an electronic comment, the EPA recommends that you include 
your name and other contact information in the body of your comment and 
with any disk or CD-ROM you submit. If the EPA cannot read your comment 
due to technical difficulties and cannot contact you for clarification, 
the EPA may not be able to consider your comment. Electronic files 
should avoid the use of special characters, any form of encryption, and 
be free of any defects or viruses.
    Docket. All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some 
information is not publicly available (e.g., CBI or other information 
whose disclosure is restricted by statute). Certain other material, 
such as copyrighted material, will be publicly available only in hard 
copy form. Publicly available docket materials are available either 
electronically in http://www.regulations.gov or in hard copy at the EPA 
Docket Center, Room 3334, 1301 Constitution Avenue NW., Washington, DC. 
The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday 
through Friday, excluding legal holidays. The telephone number for the 
Public Reading Room is (202) 566-1744, and the telephone number for the 
Air Docket is (202) 566-1742.

FOR FURTHER INFORMATION CONTACT: For the NESHAP action: Mr. William 
Maxwell, Energy Strategies Group, Sector Policies and Programs Division 
(D243-01), Office of Air Quality Planning and Standards, U.S. 
Environmental Protection Agency, Research Triangle Park, North Carolina 
27711; Telephone number: (919) 541-5430; Fax number (919) 541-5450; 
Email address: maxwell.bill@epa.gov. For the NSPS action: Mr. Christian 
Fellner, Energy Strategies Group, Sector Policies and Programs Division 
(D243-01), Office of Air Quality Planning and Standards, U.S. 
Environmental Protection Agency, Research Triangle Park, North Carolina 
27711; Telephone number: (919) 541-4003; Fax number (919) 541-5450; 
Email address: fellner.christian@epa.gov.

SUPPLEMENTARY INFORMATION: On February 16, 2012, the EPA issued the 
final MATS and Utility NSPS (77 FR 9304). In the final MATS rule, the 
EPA included a work practice standard applicable during periods of 
startup and shutdown rather than finalizing the proposed requirement 
that sources comply with numerical limits during such periods. In the 
Utility NSPS, the EPA included the same work practice for particulate 
matter (PM) emissions during periods of startup and shutdown. The work 
practice standard was designed to minimize emissions of hazardous air 
pollutants (HAP) and PM during periods of startup and shutdown by 
requiring sources to maximize the use of clean fuels during such 
periods when electric utility steam generating unit (EGU) temperatures 
and air flow may not be sufficient to effectively engage certain air 
pollution control devices (APCD). Because the agency did not propose a 
work practice standard for periods of startup and shutdown, the EPA 
determined that it was appropriate to reconsider the startup and 
shutdown provisions to allow the public an opportunity to comment on 
the requirements.
    On November 30, 2012, the EPA published in the Federal Register the 
proposed rule, ``Reconsideration of Certain New Source and Startup/
Shutdown Issues: National Emission Standards for Hazardous Air 
Pollutants from Coal- and Oil-fired Electric Utility Steam Generating 
Units and Standards of Performance for Fossil-Fuel-Fired Electric 
Utility, Industrial-Commercial-Institutional, and Small Industrial-
Commercial-Institutional Steam Generating Units'' (77 FR 71323). The 
November 30, 2012, action announced, among other things, 
reconsideration of certain new source standards for MATS and the 
requirements applicable during periods of startup and shutdown for MATS 
and the startup and shutdown provisions related to the PM standard in 
the Utility NSPS and proposed revisions to these identified provisions. 
The EPA also proposed certain technical corrections. On April 24, 2013, 
the EPA finalized reconsideration on all issues except those related to 
startup and shutdown (including related technical corrections) (78 FR 
24073).
    During the comment period, the EPA received data and other 
information from industry about EGU startup, and the industry 
commenters recommended that the startup and shutdown provisions as 
proposed be further amended. The comments raised several significant 
issues regarding the definition of startup, the types of ``clean 
fuels'' that must be used during startup, the means by which non-
mercury (Hg) emissions are calculated during periods of startup and 
shutdown (e.g., requests for the use of a default diluent cap and for 
the use of a default electrical production rate),\1\ and the manner in 
which EGUs that share a common stack demonstrate compliance during 
periods of startup and shutdown. Given the significance of these 
comments, the EPA believes it is appropriate to request additional 
comment on these issues. Therefore, we are reopening the public comment 
period so that the public can review the industry-provided information 
and data and comment on the suggested revisions to the startup and 
shutdown provisions. We are only reopening for comment the startup and 
shutdown provisions in the MATS rule and the startup and shutdown 
provisions related to PM in the Utility NSPS. We are not seeking 
comment on any other issues and will not respond to comments outside 
the scope of this notice.
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    \1\ In the May 3, 2011, proposed MATS rule (76 FR 25028), the 
EPA proposed default diluent gas values of 10 percent for oxygen or 
of the fuel-specific carbon dioxide concentration (obtained from a 
stoichiometric analysis of fuel combustion), as well as a default 
nominal electrical production rate of 5 percent of rated capacity to 
be used when calculating emissions rates during periods of startup 
and shutdown. The EPA did not finalize the provision because the 
agency finalized a work practice standard for startup and shutdown 
periods instead of numerical emission limits. Commenters indicated 
that the EPA should have retained the proposed diluent cap because 
the rule requires monitoring during startup and shutdown periods 
when continuous emission monitoring systems (CEMS) or sorbent traps 
are used to demonstrate compliance with the emission standards.
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    In the November 2012 reconsideration proposal, the EPA proposed to 
revise the definitions of startup and shutdown to clarify the 
definitions and include a reference to making useful thermal energy. 
Specifically, in Sec.  63.10042 we proposed to define the end of 
``startup'' as being ``. . .when the EGU generates electricity that is 
sold or used for any other purpose (including on site use), or the EGU 
makes useful thermal energy (such as heat or steam) for industrial, 
commercial, heating, or cooling purposes. . .whichever is earlier.'' 77 
FR 71339. We also proposed several revisions to the finalized work 
practice standards. These revisions included the addition of certain 
synthetic natural gas, syngas, propane and ultra low-sulfur diesel 
(ULSD) to the list of clean fuels.

[[Page 38003]]

Further, we proposed to require EGU source owners and operators, when 
firing coal, solid oil-derived fuel, or residual oil in the EGU during 
startup and shutdown, to vent emissions to the main stack(s) and 
operate all control devices necessary to meet the operating standards 
that apply at all other times under the final rule (with the exception 
of limestone injection in fluidized bed combustors (FBC) EGUs, dry 
scrubbers, selective non-catalytic reduction systems (SNCRs) and 
selective catalytic reduction systems (SCRs)).\2\ Moreover, we proposed 
that owners and operators of EGUs would be responsible for starting 
limestone injection in FBC EGUs, dry scrubbers, SNCRs and SCRs as 
expeditiously as possible, but, in any case, when necessary to comply 
with other CAA standards applicable to the source that require 
operation of those control devices. Additionally, we proposed to revise 
the final rule's work practice standards to recognize constraints of 
certain EGUs and APCDs. The proposed revised standards would allow 
limestone injection to start after appropriate temperatures have been 
attained in FBC EGUs that inject limestone for acid gas control and 
allow SNCR, SCR and dry scrubber systems to start as soon as 
technically feasible after the appropriate temperature has been 
reached. With regard to integrated gasification combined cycle (IGCC) 
EGUs, we proposed two options for IGCC EGUs for the handling of syngas 
that is not fired in the combustion turbine: (1) Syngas must be flared, 
not vented; or (2) syngas must be routed to duct burners, which may 
need to be installed, and the flue gas from the duct burners must be 
routed to the heat recovery steam generator. 77 FR 71330-71331.
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    \2\ Fluidized bed combustor (FBC) EGUs as a class include 
circulating fluidized bed (CFB) EGUs.
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    The commenters' primary issue with the proposed standards for 
startup and shutdown concerned the definition of ``startup'' in the 
reconsideration notice (particularly with regard to the end of 
``startup''). Specifically, the commenters objected to the EPA's 
proposed definition which defined the end of startup to be ``. . . when 
the EGU generates electricity that is sold or used for any other 
purpose (including on site use),'' or ``the EGU makes useful thermal 
energy (such as heat or steam) for industrial, commercial, heating, or 
cooling purposes,'' whichever is earlier.'' 77 FR 71339. As discussed 
below, the commenters advocated a different end point for startup. The 
EPA also received comments on the types of fuels considered ``clean,'' 
the required use of clean fuels throughout startup, the specifics of 
startup as related to IGCC EGUs, the use of diluent caps and sorbent 
trap monitoring during startup, and the application of the work 
practice standards to EGUs with a common stack. Below is a summary of 
some issues raised in the industry comments on which we are now 
requesting comment. The complete comments are contained in the MATS and 
Utility NSPS rulemaking dockets (see EPA-HQ-OAR-2009-0234 and EPA-HQ-
OAR-2011-0044, respectively).
    The commenters asked the EPA to define ``startup'' as the setting 
in operation of an affected source.\3\ According to the commenters, 
this involves igniting fuel in the boiler, producing steam to begin 
generating electricity either before or after the primary fuel is added 
to the boiler and getting all of the APCDs operational to meet the 
applicable requirements. The commenters maintained that ``startup'' 
does not end ``when any steam from the boiler is used to generate 
electricity for sale over the grid or for any other purpose'' as the 
EPA proposed. The commenters asserted that an EGU remains in 
``startup'' mode beyond the first generation of electricity because, 
according to the commenters, at that point in time many of the APCDs 
needed to comply with the requirements of this subpart may not be 
technically or safely capable of operation and those that are may be 
operating far from design conditions because the requisite 
temperature(s) and/or flow conditions have not been achieved. For 
example, the commenters expressed concern that operating electrostatic 
precipitators (ESPs) at temperatures less than the temperatures 
recommended by the manufacturer/supplier could create a safety risk.\4\
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    \3\ See, e.g., EPA-HQ-OAR-2009-0234-20257, EPA-HQ-OAR-2009-0234-
20271, EPA-HQ-OAR-2009-0234-20277, EPA-HQ-OAR-2009-0234-20279, EPA-
HQ-OAR-2009-0234-20282.
    \4\ See, e.g., EPA-HQ-OAR-2009-0234-20248, EPA-HQ-OAR-2009-0234-
20251, EPA-HQ-OAR-2009-0234-20255, EPA-HQ-OAR-2009-0234-20267, EPA-
HQ-OAR-2009-0234-20269, EPA-HQ-OAR-2009-0234-20272, EPA-HQ-OAR-2009-
0234-20275, EPA-HQ-OAR-2009-0234-20280, EPA-HQ-OAR-2009-0234-20286, 
EPA-HQ-OAR-2009-0234-20289, EPA-HQ-OAR-2009-0234-20306, EPA-HQ-OAR-
2009-0234-20308.
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    The commenters also stated that electricity generation may begin 
when the boiler's steam load is as low as 10 percent of nameplate 
capacity.\5\ At this point, the commenters stated that startup fuel is 
still being burned, either alone or in combination with primary fuel, 
but many major components of the EGU (e.g., APCDs) may neither be 
online nor fully functioning. The commenters further noted that at many 
EGUs the boiler igniters have low capacity (e.g., 5 percent of the EGU 
capacity).\6\ So, according to these commenters, the igniters as 
currently constructed may not be able to bring an EGU to flue gas 
temperatures at which APCD can be made operational. The commenters 
stated that this inability to use igniters alone to bring the EGU and 
APCD to the proper temperatures stems from a number of reasons, among 
which is the fact that some igniters offer only a low heating value 
and, thus, cannot serve a heating function well over long periods of 
time.\7\ As noted above, the commenters asserted that some igniters may 
not have sufficient capacity (i.e., size) and were generally not 
designed to preheat the APCD without the co-firing of the primary fuel 
and, for this reason, the commenters maintained that some igniters may 
not be able to generate adequate heat to preheat the APCD even if they 
were operated for an ``extended period of time.'' \8\ Commenters also 
stated that certain EGU facilities do not have sufficient natural gas 
capacity to bring their EGUs up to the temperatures necessary to engage 
certain APCDs (e.g., because the natural gas burners or pipeline are 
currently too small).\9\ The commenters maintained that, generally, the 
igniters (and warm-up guns in some cases) are used to begin to raise 
boiler pressure, supply steam to heat plant equipment (e.g., piping, 
steam turbine, pulverizers) and raise the furnace temperature to a 
point where the primary fuel can be burned. Therefore, the commenters 
asserted that the startup period involves (and in some cases must 
involve) co-firing of startup and primary fuels.\10\
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    \5\ See, e.g., EPA-HQ-OAR-2009-0234-20291.
    \6\ See, e.g., EPA-HQ-OAR-2009-0234-20297.
    \7\ See, e.g., EPA-HQ-OAR-2009-0234-20254.
    \8\ See, e.g., EPA-HQ-OAR-2009-0234-20272.
    \9\ See, e.g., EPA-HQ-OAR-2009-0234-20254 (``natural gas 
pipeline capacity has limited supply''), EPA-HQ-OAR-2009-0234-20269 
(``lacks sufficient natural gas capacity for the unit to complete 
the startup process,'' ``units do not have easy access to natural 
gas due to distributional limitations''), EPA-HQ-OAR-2009-0234-20321 
(``[a]dditional natural gas transmission capacity would also have to 
be constructed to increase delivery to the JEA units'').
    \10\ See, e.g., EPA-HQ-OAR-2009-0234-20246, EPA-HQ-OAR-2009-
0234-20248, EPA-HQ-OAR-2009-0234-20252, EPA-HQ-OAR-2009-0234-20254, 
EPA-HQ-OAR-2009-0234-20269, EPA-HQ-OAR-2009-0234-20272, EPA-HQ-OAR-
2009-0234-20283, EPA-HQ-OAR-2009-0234-20287, EPA-HQ-OAR-2009-0234-
20303, EPA-HQ-OAR-2009-0234-20321.
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    The commenters also stated that, in its proposal, the EPA did not 
adequately account for the operational differences among different 
types of EGUs. The

[[Page 38004]]

commenters stated, for example, that the startup process for 
supercritical pulverized coal (PC) EGUs is different from that for 
subcritical EGUs.\11\ The commenters stated that supercritical EGUs are 
designed to commence startup producing subcritical steam to the steam 
turbine, and then transition to supercritical operation at a certain 
point as steam production and electricity generation are increased. The 
commenters asserted that a supercritical EGU does not complete its 
startup until its transition from subcritical to supercritical 
operation is complete. The commenters recommended that the end of 
startup for supercritical EGUs should correspond with the point in time 
corresponding to 6 hours past the time when the EGU achieves 
supercritical mode of operation.\12\
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    \11\ See, e.g., EPA-HQ-OAR-2009-0234-20270, EPA-HQ-OAR-2009-
0234-20277, EPA-HQ-OAR-2009-0234-20281, EPA-HQ-OAR-2009-0234-20282.
    \12\ See, e.g., EPA-HQ-OAR-2009-0234-20281, EPA-HQ-OAR-2009-
0234-20282.
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    For subcritical EGUs, the commenters provided information 
reflecting the sequence of events during startup for two subcritical 
EGUs, stating that the baghouse, the activated carbon injection (ACI) 
and the SCR are not operational when the EGU goes online (i.e., 
connected to the grid). However, the comments indicate that the 
baghouse and the ACI controls are operational approximately 4 hours 
after the EGU reaches the 25-percent load point. The commenters stated 
that the SCR system is operational about 12 hours after the EGU goes 
online. The commenters requested that the end of startup be changed to 
be 4 hours after 25-percent load is first reached or 12 hours after 
first electricity generation, whichever occurs first.\13\ The 
commenters explained that the 4-hour timeframe would provide for a 
transition period during which a facility phases out the supplemental 
fuel, shuts down a dedicated startup system (like a startup boiler feed 
pump, if applicable) and transitions to bring emission controls online 
safely and within the manufacturer's intended design capabilities. The 
commenters maintained that the 12-hour alternative definition would 
allow for situations where the startup sequence is delayed for 
unexpected reasons, but provided assurance that an EGU will not idle at 
low load.
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    \13\ See, e.g., EPA-HQ-OAR-2009-0234-20262, EPA-HQ-OAR-2009-
0234-20281, EPA-HQ-OAR-2009-0234-20282.
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    Relative to FBC EGUs, the commenters stated that if limestone is 
added too early in the startup sequence, the flame could be 
extinguished. According to the commenters, FBC EGUs that inject 
limestone must reach a minimum bed temperature of approximately 
1,500[deg]F for the limestone to calcine, and, thus, become effective 
at reducing acid gases. The commenters stated that these EGUs often 
burn coal for about 45 minutes before limestone is added, and 
additional time is then required for the bed chemistry to stabilize. 
They stated that normally the bed is stable and up to temperature when 
approximately 40-percent load is reached. The commenters requested that 
the EPA apply the same definition of ``startup'' to FBC EGUs as was 
suggested for the other types of EGUs (i.e., 4 hours after 25-percent 
load is first achieved, or 12 hours after first electricity generation, 
whichever occurs first).\14\
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    \14\ See, e.g., EPA-HQ-OAR-2009-0234-20282.
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    The commenters also provided input on the types of fuels considered 
``clean,'' the specifics of startup as related to IGCC EGUs, the use of 
diluent caps and sorbent trap monitoring during startup and the 
application of the work practice standards to EGUs with a common stack. 
The commenters suggested that the EPA should expand the proposed list 
of ``clean fuels'' to include biodiesel and other renewable fuels that 
meet the 40 CFR Part 80, subpart M, requirements and that biodiesel and 
other biofuels be among the clean fuels allowed.\15\ The commenters 
stated that it is important that either flaring syngas or routing it to 
duct burners remain as options for IGCC EGUs and indicated that flaring 
should remain an option for routine startups and shutdowns of IGCC EGUs 
and as a viable option for non-routine events such as unit ``trips'' 
when the combustion turbine cannot combust syngas.\16\
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    \15\ See, e.g., EPA-HQ-OAR-2009-0234-20271, EPA-HQ-OAR-2009-
0234-20272, EPA-HQ-OAR-2009-0234-20276, EPA-HQ-OAR-2009-0234-20279, 
EPA-HQ-OAR-2009-0234-20282, EPA-HQ-OAR-2009-0234-20295, EPA-HQ-OAR-
2009-0234-20304, EPA-HQ-OAR-2011-0044-5803.
    \16\ See, e.g., EPA-HQ-OAR-2009-0234-20243, EPA-HQ-OAR-2009-
0234-20245, EPA-HQ-OAR-2009-0234-20281, EPA-HQ-OAR-2009-0234-20282, 
EPA-HQ-OAR-2009-0234-20299.
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    The commenters suggested that the EPA should reinstate the use of 
the diluent cap and/or provide for a diluent cap for non-mercury 
pollutants, as is allowed for Hg in Appendix A of subpart UUUUU. 77 FR 
9606. Commenters believed the use of a diluent cap is appropriate when 
complying with a heat input-based emission standard because emissions 
must be reported during periods of startup and shutdown, and using the 
actual carbon dioxide or oxygen concentrations in the stack during 
startup and shutdown will, according to the commenters, grossly 
overstate emissions, as the initial (or final) concentrations during 
those periods are close to ambient levels.\17\ Moreover, because EGU 
owners or operators who use CEMS, continuous parameter monitoring 
systems (CPMS) or sorbent traps will be required to report emission 
rates during periods of startup and shutdown, some commenters 
recommended that a default electrical output rate (in terms of 
megawatt-hours (MWh) or gigawatt-hours (GWh)) be established for use 
during startup and shutdown periods.\18\ According to the commenters, 
use of such a default electrical output rate would prevent EGU owners 
or operators from reporting infinite emissions, which is what the 
commenters state would occur when no (or zero) electrical output for 
these periods was placed in the denominator when performing these 
calculations. One commenter recommended that an EGU should not have to 
sample for Hg with sorbent traps until startup has ended because, 
unlike a CEMS, a sorbent trap system collects an integrated sample over 
an extended time period and does not provide real-time data.\19\ 
Therefore, according to the commenter, it is not possible to separate 
the Hg compliance data from data collected during startup and shutdown 
periods. The commenter noted that although startup and shutdown events 
are generally short, if startup and shutdown emissions are included in 
the compliance calculations, this could potentially skew the results.
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    \17\ See, e.g., EPA-HQ-OAR-2009-0234-20282.
    \18\ See, e.g., EPA-HQ-OAR-2009-0234-20282, EPA-HQ-OAR-2009-
0234-20306.
    \19\ See, e.g., EPA-HQ-OAR-2009-0234-20308.
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    The final rule contains specific requirements for EGUs that use a 
common stack (see Sec.  63.10010(a)(2) and (3)). Even with these 
requirements, some commenters asserted that the rule does not 
adequately account for startup and shutdown periods for individual 
EGUs. Some commenters stated that the proposed rule does not resolve 
how the startup and shutdown definitions and work practice provisions 
apply to EGUs that share a common stack. Several commenters 
acknowledged that the work practice standards would be applied 
separately on each EGU that shares a common stack, but they argued that 
the rule should provide that the numerical emission limits do not apply

[[Page 38005]]

if even one EGU sharing the common stack is starting up or shutting 
down.\20\
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    \20\ See, e.g., EPA-HQ-OAR-2009-0234-20256, EPA-HQ-OAR-2009-
0234-20277, EPA-HQ-OAR-2009-0234-20281, EPA-HQ-OAR-2009-0234-20282, 
EPA-HQ-OAR-2009-0234-20294.
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    The EPA requests comment on the information and data provided in 
the public comments regarding the startup and shutdown provisions and, 
in particular, the commenters' recommendations concerning the 
definition of ``startup.'' The EPA requests additional input on the 
following startup/shutdown-related issues that were raised by 
commenters on the proposed rule:
     The use of default diluent gas cap values during periods 
of startup and shutdown;
     How to calculate startup/shutdown emissions when multiple 
affected EGUs share a common stack; and
     The use of a default electrical production rate value to 
calculate output-based emission limits during startup and shutdown 
hours where the electrical load is zero.
    In addition, the EPA requests comment on the additional technical 
analyses it conducted in response to the above comments concerning the 
end of startup. See ``Assessment of startup period at coal-fired 
electric generating units'' in Docket ID EPA-HQ-OAR-2009-0234. In this 
analysis of EGUs, the EPA examined several indicators that can aid in 
assessing the time required to achieve operating benchmarks.
    Using these indicators, we found no significant difference in 
performance related to startup between the different groups assessed in 
this analysis. We believe these results could support defining the end 
of startup at coal-fired EGUs as occurring at 25 percent of nameplate 
capacity plus 3 hours or the start of electricity generation plus 6 
hours, whichever comes first, and we are soliciting comment on the 
analysis.
    We are only reopening for comment the startup and shutdown issues 
described above. We are not seeking comment on any other issues and 
will not respond to comments submitted that are outside the scope of 
this notice.

List of Subjects in 40 CFR Parts 60 and 63

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Hazardous substances, Intergovernmental 
relations, Reporting and recordkeeping requirements.

    Dated: June 18, 2013.
Gina McCarthy,
Assistant Administrator.
[FR Doc. 2013-15146 Filed 6-24-13; 8:45 am]
BILLING CODE 6560-50-P