NATIONAL EMISSION STANDARDS FOR HAZARDOUS AIR POLLUTANTS FROM COAL

AND OIL

- FIRED ELECTRIC UTILITY STEAM GENERATING UNITS

– RECONSIDERATION OF CERTAIN STARTUP/SHUTDOWN ISSUES ; SUMMARY OF PUBLIC COMMENTS AND RESPONSES

U.S. Environmental Protection Agency Office of Air Quality Planning and Standards Sector Policies and Programs Division Research Triangle Park, North Carolina 27711

November 201 4ii THIS PAGE INTENTIONALLY LEFT BLANKiii Contents

1.0 DEFINITIONS AND WORK PRACTICES

................................ ................................ ........................ 1

1.1. Definitions

................................ ................................ ................................ ................................ ........ 1

1.1.1 Definition of startup

................................ ................................ ................................ ................... 1

1.1.1.1 25 percent plus 3 hours, or generation plus 6 hours

................................ ............................ 7

1.1.1.3 25 percent plus 7 or 8 hours

................................ ................................ ............................... 21

1.1.1.4 25 percent plus 7 hours or generation plus 10 hours

................................ ......................... 22

1.1.1.5 50 percent plus 3 hours or generation plus 9 hours

................................ ........................... 25

1.1.1.6 Generation plus 12 hours

................................ ................................ ................................ ... 25

1.1.1.7 APCD’s in service

................................ ................................ ................................ .............. 25

1.1.1.8 Supercritical EGUs

................................ ................................ ................................ ............ 33

1.1.1.9 CFB EGUs

................................ ................................ ................................ ......................... 35

1.1.1.10 Dry FGD EGUs

................................ ................................ ................................ ................ 39

1.1.1.11 Use of SO 2 /NOx Data

................................ ................................ ................................ ...... 47

1.1.1.12 Failed Starts

................................ ................................ ................................ ..................... 50

1.1.1.13 NSPS

................................ ................................ ................................ ................................ 53

1.1.1.14 Definition of Startup

- Other

................................ ................................ ............................ 53

1.1.2 Definition of shutdown

................................ ................................ ................................ ............ 59

1.1.2.1 NSPS

................................ ................................ ................................ ................................ .. 61

1.1.3 Clean fuel s

................................ ................................ ................................ ............................... 62

1.2 Work Practices

................................ ................................ ................................ ................................ 67

1.2.1 General Support

................................ ................................ ................................ ....................... 67

1.2.2 Not Support Further Changes

................................ ................................ ................................ .. 70

1.2.3 Standard Already Accounts for Variability

................................ ................................ ............. 74

1.2.4 Legal issues

................................ ................................ ................................ .............................. 79

1.2.5 Common stack

................................ ................................ ................................ ......................... 84

1.2.6 Allow site

- specific standards

................................ ................................ ................................ ... 94

1.2.7 Title V, state, or local permitting

................................ ................................ ............................. 98

1.2.8 Petition the Administrator

................................ ................................ ................................ ........ 99

1.2.9 Flexibility to reflect equipment variability

................................ ................................ ............ 100

2.0 CLEAN FUELS

................................ ................................ ................................ ................................ 106iv

2.1 Oppose

................................ ................................ ................................ ................................ .......... 111

2.2 Co

- firing with other fu els

................................ ................................ ................................ .............. 112

2.3 Edit to standard

................................ ................................ ................................ ............................. 118

3.0 APCD OPERATION

................................ ................................ ................................ ........................ 118

3.1 Startup

................................ ................................ ................................ ................................ ........... 118

3.2 General

................................ ................................ ................................ ................................ .......... 122

3.3 Multiple APCDs

................................ ................................ ................................ ............................ 125

3.4 Acid Gas APCDs

................................ ................................ ................................ .......................... 128

3.4.1 Wet flue gas desulfurization

– wet FGD

................................ ................................ .................... 128

3.4.2 Dry FGDs and CFBs

................................ ................................ ................................ .................. 128

3.6 Selective catalytic reduction

- SCR

................................ ................................ .............................. 146

3.7 Selective noncatalytic reduction

- SNCR

................................ ................................ ..................... 148

3.8 Activated sorbent injection (ACI)/Hg control

................................ ................................ .............. 148

3.9 Limestone injection

................................ ................................ ................................ ....................... 150

3.10 Shutdown

................................ ................................ ................................ ................................ .... 151

3.11 Other

................................ ................................ ................................ ................................ ........... 153

4.0 WORK PRACTICE STANDARDS: TREATMENT OF IGCC

................................ ...................... 154

4.1 Option 1 Flares

................................ ................................ ................................ .............................. 155

4.2 Option 2 Duct Burners

................................ ................................ ................................ .................. 158

5.0 OTHER

................................ ................................ ................................ ................................ ............. 160

5.1 Use of diluent cap

................................ ................................ ................................ ......................... 164

5.2 Use of default MW value

................................ ................................ ................................ .............. 173

5.3 Sorbe nt trap monitoring systems

................................ ................................ ................................ .. 177

5.4 Other concerns

................................ ................................ ................................ .............................. 182

5.5 Support for other commenters/comments

................................ ................................ ..................... 184

5.6 Out of Scope

................................ ................................ ................................ ................................ . 1841

1

. 0 DEFINITIONS AND WORK PRACTICES

1 .1. Definitions

1.1.1 Definition of startup

Summary of Comments Received Following November 30, 2012, Proposal

C omment 1 : Commenters 2 0252, 20255

, 20257 , 20262, 20270, 20271, 20272, 20277, 20279, 20280, 20281, 20282, 20288, 20291, 20294, 20295, 20306, 20308, and 2032 1 comment ed on the proposed definition for the end of the startup period. Commenters state that even though a n EGU is producing electricity or useful steam, that EGU has not necessarily completed startup from an operational standpoint. Commenters request that the EPA should modify how it defines startup to allow all emission control devices to reach operational effectiveness before startup ends. Commenters note that per the

EPA ’ s definition of startup even internally used steam could inaccurately m ark the end of the startup and thereby terminate applicability of the work practice standards.

Commenters note that spikes in emissions can occur after the EPA ’ s defined end of startup. Consequently, electric utility steam generating units ( EGUs ) may hav e difficulty complying with a 30

- operating day average if the end of startup is tied to electricity generation. Commenters further state that the problem will be compounded by the fact that it is possible for the EGUs to startup more than once in a single 30

- day averaging period, and the need for startups is not predictable. Commenters emphasize

that the EPA ’ s definition of “ startup ” that requires EGUs to begin to measure hazardous air pollutant ( HAP ) emissions does not match with the EPA ’ s startup work pra ctice standards, , which correctly recognize that certain air pollution controls cannot be immediately started without damaging the controls or putting plant workers at a safety risk.

Commenters ask that the determination as to when startup ends should b e determined on a unit

- by

- unit basis and placed in a unit

- specific startup and shutdown plan. Commenters suggest that if the EPA does

not want to use a case

- by

- case approach for determining startup, then the EPA should develop different startup definitions based on generation type because of related differences in startup processes.

Commenter s discussed different types of EGUs and provide specific suggestions for startup definitions by EGU types including: (1) supercritical EGUs, ( 2 ) subcritical EGUs, (3) fluidized bed combustors ( FBCs ) , and (4) integrated gasification combined cycle ( IGCC ) EGUs. Commenters note that these definitions should apply unless the owner/operator demonstrates the need for an alternative EGU

specific “ startup ” because of unique EGU conditions. In that case, the permitting authority would approve an alternative definition in the EGU ’ s Title V permit.

Some commenter s ask that the EPA apply the Part 63 General Provisions definitions of “ startup ” and

“ shutdown ” to subpart UUUUU. Other s recommend that the Mercury and Air Toxics Standards ( MATS ) be revised to specify that EGUs have a startup plan incorporated into its Part 70 permit. A

commenter state s that for EGUs that select the site

- specific option, startup/shutdown (SS) plans would allow owners and operators to determine when startup and shutdown begins and ends based on parameters that are easily monitored at that EGU

. Commenter further state that these parameters could be based on requirements in other rules to which EG Us are already subject. Commenter notes that as an example, EGUs subject to the Acid Rain Program are already required to define the EGU ’ s ranges of2

operation and normal load ( see 40 CFR Part 75, Appendix A, section 6.5.2.1 )

. Commenter s state that startup and shutdown for such EGUs could easily be based on these ranges of operation.

A commenter state s that allowing EGUs the option to develop SS plans would avoid potential conflicts between the MATS and other applicable requirements, would reg ulate SS more efficiently than applying multiple, overlapping SS requirements, and would reduce unnecessary administrative burdens on regulated sources. Commenter s urged the EPA to allow EGUs to elect to either follow the proposed definitions of startup an d shutdown, or to follow an individualized SS plan.

Individual comments are as follows.

Commenter 20288 recommends that the definition of startup be revised to provide that startup does not end until all emissions control devices for a particular EGU reaches operational effectiveness.

Commenter 20269 notes that the generation of electricity is not always the optimal time to begin using air pollution control equipment.

Commenter 20282 recommends that the EPA should modify the definition of “ startup ” to allow all emission control devices to reach operational effectiveness before “ startup ” ends. Commenter provides discussion about the incentives EGUs have to exit startup as quickly as possible.

Commenters 20255, 20281, 20282, and 20295 state that endi ng “startup” when electricity is first produced does not account for the time needed to set the boiler and its associated air pollution control equipment into operation, and that electricity production and startup typically overlap.

Commenter 5803 agreed with the proposed language defining startup and shutdown. Commenter states that the confusion of whether it is the use of steam or the generation of electricity that ends the startup period is adequately addressed in the reconsideration. Commenter agreed with similar references to steam use that are proposed to be removed from the definition of shutdown events.

C ommenter 20291 states that the EPA should modify how it defines startup to allow all emission control devices to reach operational effec tiveness before startup ends. Commenter suggests that the definition should reflect the length of time actually needed to set a n EGU into operation.

Commenter 20308 states that for existing sources, the work practice must be clear that the end of startup occurs when conditions meet a minimum level that is associated with the pollution control equipment

and method utilized.

Commenter 20255 states that emission control systems do not reach optimal performance when either electricity or steam is first produ ced. Commenter states that the definition of startup must take into account the limits of control equipment to meet the emission limits and EGUs must be permitted to ramp up their operations (temperature, flow, velocity, chemistry) to the point pollution c ontrol equipment may be effectively engaged. Commenter listed nine main steps ( supplemental fuel fire; steam usage; coal fire; ESP energized; unit online (i.e., selling electricity to the grid); scrubber in service; SCR inlet opening (ready for ammonia inj ection once the appropriate temperature is reached); ammonia flow for the SCR; 25 percent load) that occur during startup, with the EGU online and selling electricity as step3

five. Commenter states that control systems must be phased in during startup according to their unique time, temperature and pressure requirements. Commenter states that the EPA regulations must be clear that the end of startup occurs when conditions meet minimum levels specifi c to the pollution control equipment and methods used.

Commenter 20277 states that controls will not be fully functional when the EPA defines startup as ending. Commenter states that electricity production and startup are not by definition distinct modes, and instead typically overlap. Commenter provides examples to highlight this point. Commenter urged

the EPA to modify “ startup ” to provide additional time to allow all emission control devices to reach operational effectiveness before “ startup ” ends so th at the definition reflects the actual length of time needed to set an EGU and its associated control devices into operation.

Commenter 20291 states that ending startup when electricity is first produced does not account for the time needed to set into operation the boiler and associated pollution control equipment. Commenter

states that the EPA fails to recognize that electricity production and start up are not by definition distinct modes, and typically overlap. According to commenter , electricity generation can begin when a boiler ’ s

steam load is less than 10 percent, at which point startup fuel is still being burned, alone or in

combination with coa l, and major components of the EGU , including air pollution controls, are neither online nor fully functioning.

Commenter 20291 states that although the EPA has recognized the operational constraints of pollution control equipment during startup, the Age ncy fails to recognize that those controls will not be fully

functional when the EPA defines startup as ending. As a result, commenter notes that spikes in

emissions can occur after the EPA ’ s defined end of startup.

Commenter 20294 states that the EPA should more clearly define that period of time when compliance monitoring begins and ends for coal

- fired EGUs. Commenter states that, as written, the definitions of startup and shutdown do not reflect the temporary and transient operating conditions that exist to ensure the safe and reliable transition from shutdown to normal operation. Commenter states that even internally used steam could inaccurately mark the end of the startup and thereby terminate applicability of the work practice standards.

Comment ers 20257, 20262, 20270, 20271

, and 20321 state that the EPA ’ s determination that startup ends when an EGU generates electricity or makes useful thermal hea t is not an appropriate cutoff for startup. Each of the commenter s provide s discussion about the processes leading up to electricity generation and the processes after that point. Commenter s discussed the engineering and safety issues of the process.

Commenter 20257 states that the boiler is not fully finished with startup until all available cyclones are online, which could take 20 hours or more for a normal startup.

Commenter 20262 suggests defining the end of startup for subcritical coal

- fired EGUs as 4 hours after 25 percent load is first reached, or 12 hours after first electricity generation, whichever occurs first.

Commenter states that the 4

- hour timeframe would provide for a transition period to complete primary fuel firing and bring in emission con trol equipment safely. Commenter states that the 12

- hour alternative4

definition is designed to cover situations where the startup sequence is delayed for unexpected reasons, but still provides assurance that a n EGU will not idle at low load.

Commenters 20 281 and 20282 recommend that the EPA set a bright line test for defining the startup of a supercritical EGU as the transition point from subcritical mode to supercritical mode plus 6 hours and for subcritical (i.e., conventional drum) EGUs , the startup per iod should end 4 hours after 25 percent load is first reached, or 12 hours after first electricity generation, whichever occurs first . For FBC EGUs, Commenter 20282 recommends the startup period should end 4 hours after 25 percent load is first reached, or 12 hours after first electricity generation, whichever occurs first.

Commenter 20270 states that during the period of bringing control equipment to normal operating conditions, the equipment may operate far from its design conditions and emissions may be unpredictable.

Commenter 20271 states that startup ends and normal operation of the EGU beg ins when the EGU has achieved minimum stable load and the APCDs have been properly placed in service. For this purpose,

commenter states that the EPA should use the minimum load for an EG U as defined for the Acid Rain

P rogram. Commenter notes that this val ue is reported to the EPA in each EGU ’ s monitoring plan.

Commenters 20281, 20282, and 20291 state that EGUs may have difficulty complying with a 30

- operating day average if the end of startup is tied to electricity generation.

Commenter 20291 states that the problem will be compounded by the fact that it is possible for the

EGUs to startup more than once in a single 30

- day averaging period, and the need for startups is not predictable.

Commenter 20257 states that the conditions for a fully functioni ng activated carbon injection ( ACI ) and selective catalytic reduction ( SCR ) systems will occur well beyond the time that electricity or useful thermal energy is initially achieved. Commenter notes that having to incorporate these startup concentrations in the 30 day compliance average will make it even more difficult to comply with the MACT standards, and this will be compounded if the EGU has multiple startups during the 30 day averaging period. T herefore, commenter states , the EPA should define the end of startup as the time when emission controls and boiler systems are in stable operation.

Commenter s 20277 and 20282 state that the EPA ’ s definition of “ startup ” that requires EGUs to begin to

meas ure HAP emissions does not match with the EPA ’ s startup work practice standards, which correctly recognize that certain air pollution controls cannot be immediately started without damaging the controls or putting plant workers at a safety risk. Commenter s state that the EPA fails to recognize that those controls will not be fully functional when the EPA defines startup as ending.

Commenter s 20269 and 20279 ask that the EPA allow EGUs the choice of using the definitions of startup and shutdown provided in the rule or be allowed to create site

- specific definitions for startup and

shutdown.

Commenter 20288 states that the determination as to when startup ends should be determined on a unit

by

- unit basis and placed in a unit

- specific startup and shutdown pla n.5

Commenters 20270, 20277, 20281, and 20282 suggest that if the EPA does not want to use a case

- by

case approach for determining startup, then the EPA should develop different startup definitions based on generation type. Commenters recommend startup de finitions based on generation type: (1) supercritical EGUs ; and ( 2 ) subcritical EGUs ; and ( according to Commenter s 20270, 20277, and 20282), (3) FB C s; and (4) IGCC EGUs (as the definitions relate to the gasifier)

. Commenter s provide discussion about each of these types of EGUs , with suggestions for startup definitions by EGU type.
Commenters 20281 and 2028 2 provide a series of diagrams that show the steps for a supercritical EGU ’ s startup.

Commenter 2028 2 notes that these definitions should apply unless the owner/operator demonstrates the

need for an alternative EGU

- specific “ startup ” because of unique EGU conditions. Commenter states that in that case, the permitting authority would approve an alternative definition in the EGU ’ s Title V permit.

Commenters 20306 and 2030 8 support the definitions based on type of generation EGU proposed by

Commenter 2028 2 for startup and shutdown.

Commenter 2029 4 states that although the EPA recognizes the importance of temperature in the startup of some controls, the Agency did not address all pollution control equipment. Commenter request s that the definition of startup for subcritical EGUs be changed to that recommended by Commenter 20282

.

Commenter 2030 8 recommends that the EPA include startup and shutdown definitions that take into consideration distinctions between both the EGU sources and their air pollution control devices (APCDs) , and define startup and shutdown based on individual E GUs and their control devices, for new and existing EGUs

.

Commenters 20277, 20280, 20282, 20288, 20295, and 2030 6 suggest that in place of a specific definition and work practice standard that applies to all EGUs, the EPA consider imposing a requirement that each EGU that is an affected source under the MATS Rule comply with a unit

- specific startup

definition. Comment er s state that the definition would be developed by the EGU owner or operator and submitted and approved by the permitting authority using the Title V permitting program.

Commenter 2030 6 recommends that the start

- up and shutdown plans be approved separate ly from the Title V permit to allow flexibility for approvable changes as operators learn from repeated startup and

shutdown events.

Commenter 2028 8 recommends that start

- up or shutdown should be revised in the plan by reaching a specified load, emission control equipment reaching full efficiency, or the EGU reaching other specified operating conditions. Commenter notes that the startup process could require 12

- 36 hours or more depending upon the situation, and the shutdown periods would generally be short er, but also vary in

duration.

Commenter 2028 2 provides discussion about the differences in startup times between different EGUs

.6

Commenters 20281 and 2029 1 recommend that the EPA apply the Part 63 General Provisions

definitions of “ startup ” and “ shutdown ” to s ubpart UUUUU.

Commenter 2028 1 recommends that as an alternative to the standard definition of startup, an EGU operator would be allowed to develop a unit

- specific startup plan. Commenter discussed its recommendations for individual startup plans, including using the HAP and Title V permitting program to review plant

- specific startup plans. Commenter recommends these changes as an alternative to expanded definitions for startup and shutdown periods.

Commenter 2029 1 recommends that MATS be re vised to specify that EGUs have a startup plan incorporated into its Part 70 permit. Commenter states that the plan could define when specific pollution control equipment will be brought online for that EGU , and could be submitted to the permitting authority. Commenter states that the plan could also specify that best operational practices will be followed to startup the EGU as quickly and safely as possible to minimize emissions.

Commenter 2027 9 states th at for EGUs that select the site

- specific option, SS plans would allow owners and operators to determine when startup and shutdown begins and ends based on parameters that are easily monitored at that EGU

. Commenter states that these parameters could be ba sed on requirements in other rules to which EGUs are already subject. Commenter notes that as an example, EGUs subject to the Acid Rain Program are already required to define the EGU ’ s ranges of operation and normal load ( see 40 CFR Part 75, Appendix A, section 6.5.2.1 )

. Commenter states that startup and shutdown for such EGUs could easily be based on these ranges of operation. Commenter notes that other EGUs may decide that startup will end at the time the EGU is synchronized with the utility electric di stribution system and that shutdown will begin when the EGU ceases to be synchronized with the utility electric distribution

system. Commenter states that this is a more precise delineation of the boundaries of startup and

shutdown for EGUs that produce el ectricity during startup prior to connecting with the grid.

Commenter 2027 9 states that allowing EGUs the option to develop SS plans would avoid potential conflicts between the MATS and other applicable requirements, would regulate SS more efficiently than applying multiple, overlapping SS requirements, and would reduce unnecessary administrative burdens on regulated sources. Commenter urged the EPA to allow EGUs to elect to either follow the proposed definitions of startup and shutdow n, or to follow an individualized SS plan.

Commenter 2028 1 provides examples of emissions variation during extended startup conditions.

Commenter 20282 provides attachments showing mercury (Hg) emissions spikes prior to full engagement of the SCR, and ot her examples of commenter’s point that control systems have a transition period before full emission control effectiveness.

Commenter 2027 3 states that based on the start

- up profile for its facility, the new definition of start

- up will likely shorten the period of time defined as start

- up by one or 2 hours. Commenter states that its facility start

- up profile provides that petroleum coke is not burned until sometime after main steam flow

is e stablished. Commenter states that therefore, at the end of the EPA prescribed start

- up period, the

EGUs will be burning primarily natural gas or propane. Commenter states that because the reconsidered

MATS are based on 30

- operating day rolling averages, the shorter start

- up period may result in higher

initial sulfur dioxide ( SO 2 ) emissions counted in the first averaging period after a n EGU start.7

Commenter states that this is due to the higher SO 2 emissions as the circulating fluidized bed ( CFB ) boilers are transitioned to petroleum coke with stabilization of limestone injection in the CFB bed, and

the circulating dry scrubber

– flue gas desulfurization ( CDS

- FGD ) system is brought into service.

Commenter states

, thus, SO 2 emissions could spike as petroleum coke is fired and could result in an exceedance of the tight SO 2 MATS. Commenter states that at this time, there is insufficient information to understand the impact of a shorter start

- up period on SO 2 MATS compliance. Commenter notes that in a D.C. Circuit filing made on January 6, 2012, Case No. 12

- 1100, Document No. 1413644, the EPA has acknowledged that it is continuing its reconsideration of start

- up in the MATS rule and, hopefully, will appropriat ely address the issue described above.

Commenter 2025 1 suggests that the definition of startup should cover the time where emissions may be higher due to the startup event. Commenter provides the following revised language for the definition of startup gi ven in 40 CFR 63.10042 of the MATS rule:

Startup means the period in which operation of an EGU is initiated for any purpose. Startup begins with either the first

- ever firing of fuel in an EGU for the purpose of producing electricity or useful thermal ene rgy (such as heat or steam) for industrial, commercial, heating, or cooling purposes or the firing of fuel in an EGU for any purpose after a shutdown event. Startup ends when all pollution control equipment that is necessary to comply with the applicable e mission limits under this Subpart are engaged. Needed pollution control equipment shall be engaged as expeditiously as possible, considering safety, good engineering practices and manufacturers ’ recommendations. the EGU generates electricity that is sold o r 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 (16 U.S.C. 796(18)(A) and 18 CFR 292.202(c)), whichever is earlier

.

Summary of Comments Received Following June 25, 2013, Reopening of Public Comment Period

1.1.1.1 25 percent plus 3 hours, or generation plus 6 hours

Comment 2 : Commenters 20384 and 20389 support defining the end of startup as occurring at 25 percent of nameplate capacity (or greater) plus 3 hours, or the start of electricity generation plus 6 hours,

whichever comes first.

Commenter 20387 supports defining the end of startup as engaging all APCD equipment (except SCR) at 25 percent of nameplate capacity (or greater) plus 3 hours, or the start of electricity generation plus 6 hours, whichever comes first.

Commenter 20390 supports a default nominal electrical production rate of 25 percent of rate d capacity for startup and shutdown or until the EGU achieves steady state of 10 percent oxygen ( O 2 ) , whichever

comes first.

Commenter 20418 states that the definition applied to the end of startup should be based solely on achieving 25 percent nameplate capacity plus a certain number of hours. Commenter states that the8

number of hours should be more than 3 to ensure facilities can adequately comply with the MATS requirements.

1.1.1.2 25 percent plus 4 hours, or generation plus 12 hours

Comment 3 : Commenter 20391 states that the EPA should redefine the end of startup to adequately reflect the length of time needed to set an EGU into operation. Commenter states that the EPA ’ s choice of defining “ end of startup ” as the initial production of electrici ty is still problematic because it does not fully consider whether emission controls are still being “ set into operation, ” and thus whether an EGU has a steady

- state emissions profile. Commenter states that ending startup when electricity is first produced does not account for the time needed to set the boiler and its associated air pollution control equipment into operation and fails to recognize that electricity production and startup are not by definition distinct modes, but instead typically overlap. Co mmenter states electricity generation normally begins when the boiler ’ s steam load is less than 10 percent. Commenter states that at this point in the startup process, startup fuel is still being burned, either alone or in combination with coal, and major components of the EGU including pollution control equipment are neither online nor fully functioning. Commenter states that as a result, spikes in HAP emissions can occur after the defined end

of “ startup ” as currently proposed. Commenter states that EGUs may have difficulty complying with a

30

- day operating day average if the end of startup is tied to initial electricity generation. Commenter

states that this problem will be compounded by the fact that it is not uncommon for EGUs to start up

more than once in a single 30

- day averaging period because EGU startups are controlled by a third party regulator (e.g., the regional transmission authority). Commenter states that the demand for starts is driven by weather, customer actions and the reliability of other EGU ’ s in a regional generation system, none of which are always predictable.

Commenter 20391 states that the EPA should modify how it defines “ startup ” to provide additional time to complete startup operations so as to allow all emission control devices to reach full operational

effectiveness before “ startup ” ends. Commenter states that the definition should reflect the length of time actually needed to set an EGU into operation. Commenter states that for these reasons, it generally

support s , as an option, the concept of setting a presumptive (or default) definition for the end of startup that is tied to gross load levels (electricity generation as a percentage of nameplate capacity) and the time needed for control equipment to reach operatio nal effectiveness. Commenter states that this concept was recommended by Commenter 20282 in its comments on the initial reconsideration proposal, suggesting that the end of startup for EGUs be defined as occurring at least 4 hours after 25 percent of

namep late capacity is first achieved or 12 hours after first electricity generation, whichever occurs first,

for subcritical coal EGUs and fluidized bed EGUs ( “ the 4/12 test ” ).

Commenter 20391 states that the EPA appears to have endorsed this approach, and has solicited comment on defining the end of startup as 3 hours after 25 percent load is first achieved or 6 hours after first electricity generation, whichever occurs first (a “ 3/6 ” test), based on an analysis discussed in the technical support document ( Startup TSD) “ Assessment of startup period at coal

- fired electric generating units ” (EPA

- HQ

- OAR

- 2009

- 0234

- 20378). Commenter states that the EPA ’ s definition proposed in the reopening notice is a sub stantial improvement over the definition based solely on first electricity generation that was proposed in the initial reconsideration notice. Commenter states however, the analysis supporting the “ 3/6 test ” focuses on “ normal ” or average startups and does not capture the inherent variability in how any given EGU starts up Commenter states that for example, an analysis9

performed in support of Commenter 20428’s “4/12 test” suggests that startups at EGUs sharing a common stack extend well beyond 6 hours after first electricity generation. Commenter states that in addition, the EPA ’ s analysis is focused only on SO 2 and nitrogen oxides ( NOx ) emissions and does not include Hg emissions or particulate matter ( PM ) emissions (that are used as a surrogate for non

- mercury metals in the Utility MATS rule), whereas its analysis included Hg and PM. Commenter states that accordingly, it believe s that lengthening the time periods to the “ 4/12 test ” suggested by Commenter

2 0428 would better serve as a presumptive definition for end of startup and better capture the variability of startups across the universe of EGUs subject to the MATS rule.

Comment 4 : Commenter 20400 states that the MATS definition of startup excludes oper ations that are part of the startup process. Commenter states that although the generation of electricity is a very bright line which is easy to define, many startup activities continue well past this point. Commenter states that

emissions are also differe nt because the control equipment has not reached the operating conditions that

allow it to function at full effectiveness. Commenter states that as an example, certain types of FGD systems will not have reached proper chemistry conditions which will influe nce SO 2 and Hg emissions.

Commenter states that fluidized bed EGUs that inject limestone must reach a minimum temperature of approximately 1,500 ° F for the limestone to calcine, and thus become effective at reducing acid gases.

Commenter states that in the current rule making, the EPA has recognized comments from various parties, including the commenter that show that startup activities continue well past the time that electricity is first generated. Commenter states that as a result, the EPA ha s the justification to modify and expand the definition of a startup from its current form.

Commenter 20400 states that the EPA designed the Utility MACT information collection request ( ICR ) so that no data was collected during these periods and operators generally have had no reason to collect

such data either. Commenter states that startup and shutdown periods have highly variable operating conditions and consequently, reference test methods cannot be utilized because the sources do not operate in a stea dy state as required by the methods. Commenter states that in addition, the EPA lacked

sufficient information from continuous emission monitoring systems ( CEMS ) because the use of PM, Hg

, and hydrogen chloride ( HCl ) CEMS were not in wide spread use and ins ufficient data was available to develop standards during these periods. Commenter states that without this information, the EPA has no way of knowing if emissions standards based on 30

- day rolling averages are appropriate to address less predictable emissi ons during startups and shutdowns.

Although Commenter 20400 agrees that the EPA ’ s selection of work practice standards during startup and shutdown periods is appropriate, it disagrees with the EPA ’ s determination that a startup ends when electricity is fi rst generated. Commenter states that rather, that there are additional important steps that occur after the generation of electricity begins and that the EPA should acknowledge these steps by expanding the startup definition. Commenter is concerned that if the EPA does not expand the definition, then EGUs, including the well

- controlled EGUs used to set the emission standards, will have difficulty complying with the emissions standards, specifically Hg, because of the higher emission rates occurring during these periods. Commenter states that although startups ideally occur infrequently, it i s highly certain that all sources will at some times experience times with two or more startups during a single 30

- day averaging period. Commenter believes this hinders a source ’ s ability to average down the potentially higher startup emissions and greatly increases the potential for non

- compliance.10

Commenter 20400 does not have the same issue with regards t o the EPA ’ s shutdown definition and i t believes EGUs will spend little time in that shutdown period, and

, therefore

, there is not a problem of

the same severity. Commenter notes that when an EGU trips offline suddenly, the combustion of fuel stops in less than a minute. Commenter states that d uring a controlled shutdown, load is gradually reduced to a lower level, and then the EGU is intentionally trippe d and fuel flow also stops in less than a

minute. Commenter notes that IGCC EGUs have a different shutdown process.

Commenter 20400 states that it is important that the regulation account for the full period of startup activities, not just the time until the generator first produces electricity. Commenter states that by nature, startup is a period of suboptimal operation where the operators are engaging numerous systems and processes to bring the EGU to normal operation. Commenter states that the sub

- optim al conditions not only affect the performance of pollution control systems (and the mass of emissions leaving the stack) but also affect the generation efficiency. Commenter states that because each of the MATS emissions standards include an output

- based s tandard (required for new EGUs and optional for existing EGUs ), including periods where electricity generation has begun but the EGU has not yet achieved normal, stable operation is not appropriate because the output

- based emissions rate during this period will not be representative of the emissions rate during normal EGU operation.

Commenter 20400 continues to recommend that for a supercritical EGU ( one that generates steam that is in excess of 3,206.2 pounds per square inch, atmospheric ( psia ) and 705. 40 °F ), startup should end 6 hours after the transition from subcritical to supercritical mode concludes. Commenter states that for

subcritical EGUs ’ (from commenter ’ s perspective, a subcritical EGU is one that does not operate with supercritical steam and i ncludes conventional drum EGUs

, EGUs that are stoker fired, or EGUs utilizing FBC)

, the startup period should end 4 hours after the EGU reaches 25 percent of full load capacity.

Comment 5 : Commenter 20400 disagrees with the EPA ’ s analysis and conclusions concerning the length of an EGU startup. Commenter states that in the current rulemaking notice the EPA states “ 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. ” Commenter states that the EPA ’ s Startup

TSD states that “ all types of EGUs in this study can reach 25 percent of nameplate cap acity in 3 hours or less after the start of generation. Commenter states that in its Startup TSD, the EPA also quotes the Babcock and Wilcox Company (B&W), a major boiler equipment manufacturer, to conclude that “ larger

coal

- fired EGUs may need 4 to six ho urs for startup. ” C ommenter disagrees with these three statements. Beginning with the quotation that the EPA took from EPA

- HQ

- OAR

- 2009

- 0234

- 20381

, commenter
finds that the EPA has taken a short passage and has read it completely out of context. C ommenter

p rovides the complete paragraph is as follows:

Cold start and low load operation

Cold boiler startup requires firing at low heat input for long periods of time to avoid expansion difficulties and possible overheat of the superheaters or reheaters. Low pre ssure ( 200 psig (1.38 MPa gauge )) boilers without superheaters may need only about an hour of low load operation. Larger high pressure units however, may need four to six hours for startup. During startup, combustion efficiency is typically poor, especiall y with residual oils, due largely to low furnace and combustion air temperatures.11

Commenter 20400 states that as a first matter, this quotation comes from a chapter entitled “Oil and Gas Utilization.” Commenter states that although the EPA may be relying on this chapter to justify a startup period for oil

- fired EGUs, the chapter is clearly not intended to refer to an oil

- fired EGU. Commenter

states that even to the extent that it could apply to any EGU, according to the EPA, B&W states that an EGU startup only requires 4 to 6 hours. Commenter states that however as seen in the actual paragraph, B&W is not referring to an entire EGU and all its components; rather it is referring only to the boiler portion of an EGU. Commenter states that the boiler by itself must be started before it is capable of delivering steam to the turbine so that the first electricity can be generated. Commenter states that the passage that the EPA quotes is very general in nature and applies across the wide variety of products that

B& W provides for many industries. C ommenter notes that the boilers supplied for EGUs are generally the largest made and are very specialized. Commenter states that as a result it is not appropriate for the EPA to use such a general comment to characterize pe rformance in a very specialized application.

Commenter 20395 states that the EPA misquotes the B&W Steam book by citing that large coal

- fired

EGUs “ may need four to six hours for startup. ” Commenter notes that, in fact, this statement by B&W is

not in the section for coal

- fired EGUs at all, rather in the oil and gas chapter and that even if this were true for the boiler, the EPA must consider the startup of the system, not just the boiler. Commenter maintains that actual EGU startup for purposes of emissio ns reduction involves the “ setting in operation ” of the boiler and its APCDs

.

Commenter 20400 states that a major flaw in the EPA ’ s Startup TSD analysis is that it determines an average performance and attempts to characterize that all EGUs are capable of attaining that average performance. Commenter states that this analysis fails for two reasons. Commenter states that first it assumes that all EGUs are constructed similarly and have pretty much the same startup process.

Commenter states that second, it f ails to recognize that even at the same EGU, startup times will vary and that there are differences between the length required for hot, warm and cold startups. Commenter

also states that in its analysis, the EPA recognizes that the hours of fossil fuel co mbustion before generation are different for different types of startup. Commenter states that however it fails to recognize that the length of time after electricity is first generated until the EGU reaches 25 percent load will vary.

Commenter 20400 states that although there are many causes, an easily explained scenario concerns the

steam turbine. Commenter states that the firing of fuel in a boiler allows it to be warmed well before electricity is first generated. Commenter states that however full warming of a steam turbine can occur only after steam is admitted and the generator is connected to the grid. Commenter states that once high temperature steam is admitted to the turbine the rotating elements and the shell begin to heat up and to expand. C ommenter states that because the components expand at different rates, the rate of heating must be controlled and limited to prevent internal damage. Commenter states that the amount of turbine heating required is different for cold, warm and hot starts. C ommenter states that this can lead to extended startup periods.

Commenter 20400 states that in addition to the steam turbine example, EGU operators experience many different circumstances that protract a startup period. Commenter states that an EGU is an extremely complicated assembly comprised of dozens of sub systems and thousands of individual components.

Commenter states that all components must work together, and any one component not operating properly may delay the startup process. Commenter states that these delays are caused by physical12

constraints ( i.e., the EGU just cannot physically produce more electricity), are necessary to prevent damage to equipment (such as insuring proper water and steam chemistry, or thermal requirements) or for personnel safety. Commenter states that many of these constraints regularly occur in the period from

when a n EGU first generates electricity until after it reaches 25 percent of its full load capability.

Commenter provides six specific examples as follows:

• For r emoving SO 2 and Hg, some EGUs have multiple FGD scrubber modules. Commenter has one facility that has six scrubber modules. When starting that EGU, only three modules may be in service. As power increases, additional modules are placed into

service. Each m odule goes through its own startup process and requires time before it reaches the right chemical equilibrium that produces the full effectiveness.

• When an EGU is not producing electricity, it must be supplied with electric power from the outside grid. Once the EGU generates sufficient power (typically less than 25 percent load) the power supply for station equipment is transferred to the output of the generator. This involves switching ve r y high voltage transformers and must be done under

controlled con ditions. Failure to execute this step properly will result in a failed startup.

• During a startup, it is common to have hold points for boiler water chemistry. These holds limit EGU output until the water reaches minimum purity levels. Failure to observe these holds will cause damage to boiler tubing and turbine components.

• The rate of a startup often depends upon the type of shutdown. In many cases an EGU will rapidly trip off line unexpectedly. This can leave pulverizers and burner lines full of

unbu rnt fuel as well as other difficulties. Regardless of whether it is a hot, warm or cold restart, the type of shutdown will impact the length of the next startup.

• As power increases, additional coal pulverizers are placed into service. Oil fired igniters are used to light off the coal flow during a pulverizer startup. Delays are common due to lighter operation, and/or problems with the pulverizer itself. Failure to properly start a pulverizer can result in fire or explosion placing equipment and personnel at severe risk.

• During a startup, bottom ash and flyash handing systems must be placed into service. It is common to have pluggage in these systems during a startup, particularly in flyash hoppers. If ash handling systems do not function properly, then the amount of load must be limited until they are properly in service.

Commenter 20400 states that although this list cites only a limited number of examples, all EGUs will experience extended startups, which is something that EGU operators cannot preven t. Commenter states
that the EPA ’ s analysis characterized that EGUs can startup and achieve 25 percent load in approximately 3 hours. Commenter states that however the EPA arrived at this conclusion based on average performance. Commenter states that this essentially means that half of the EGUs can achieve

these times and half cannot. Commenter states that this matters because EGUs must be in compliance

with the MATS standards at all times. Commenter states that emissions control equipment only r eaches

its full effectiveness once a n EGU can attain the proper load and the control equipment reaches the proper condition. Commenter states that a review of the EPA ’ s own data shows that longer startups are13

very common. Commenter states that using the EP A ’ s spreadsheet analysis ( EPA

- HQ

- OAR

- 2009

- 0234

- 20378 ), Commenter identified 6,522 successful startups where the average time to reach 25 percent load

was about 2.8 hours. Commenter states that the standard deviation of this data was 2.43 hours which

indica tes a large amount of variability. Commenter states that of these successful startups, 1,520 extended to 4 or more hours, and 408 of those startups required 7 or more hours to achieve 25 percent

load. Commenter states that this supports its recommended sta rtup definition of reaching 25 percent of load plus 4 hours for subcritical EGUs and completing transition to super critical mode plus 6 hours for super critical EGUs . From commenter ’ s experience, these time periods are sufficient to allow operators

to wor k through the many challenges it face s in operating EGUs.

Comment 6 : Commenter 20400 states that startup for subcritical EGUs should conclude at least 4 hours

after a n EGU reaches 25 percent capacity. Commenter states that for subcritical, or conventional drum

EGUs , it is harder to identify the same bright line point in the startup process that is tied to an operational change because there are many plant equipment configurations and many different ways in

which subcri tical EGUs startup. Commenter states that some subcritical EGUs generate their first electricity while still combusting only their startup fuel whereas others do not. Commenter states that

some EGUs use steam driven boiler feed pumps for normal operation, but use a lower capacity electric feed pump for startup. Commenter states that startup activities include the closing of boiler and turbine startup vents and drains, but only after sufficient steam temperature and pressure are reached.

Commenter states tha t as a final example, many plant systems such as the coal pulverizers are operated

in manual mode until the EGU reaches a minimum power level. Commenter states that subcritical EGUs share many of the same operational concerns during startup that supercriti cal EGUs face, which contributes to higher emissions immediately after the first generation of electricity. Commenter states that the difference is that they do not face the added delays caused by the transition to supercritical mode of operation.

Comment er 20400 states that the EPA has suggested that one alternative is to extend the use of cleaner fuels such as fuel oil or natural gas for longer periods of time during startup to replace fuels such as coal.

Commenter states that the systems that supply the se fuels to the boiler, however, are generally too small to replace coal. Commenter states that as an example, one type of its coal pulverizer s has seven or eight individual burner lines, and it is used for both subcritical and supercritical EGUs . Commente r states that each of the burner lines is paired with an oil gun that is used to light the coal fire and to stabilize the coal flame when the pulverizer is operated at lower capacity. Commenter states that the heat input from coal for this pulverizer is ab out 1,200 million British thermal units per hour ( MMBtu /h) per hour, whereas the oil guns are only capable of delivering 17.5 MMBtu /h . Commenter states that clearly the oil guns do not have the capacity to deliver the same amount of heat provided by the coal pulverizers. Commenter

states that even if the oil guns were radically increased in total capacity, the rest of the system including tanks, pumps, p iping, controls, etc. would all have to be increased to match. Commenter states that as a result substituting cleaner fuels in place of coal can have only a limited effect or would require extensive modification just to accommodate more use of these fuels during startup periods.

Commenter 20400 states that considering all these factors, it recommends that the end of “ startup ” for subcritical (i.e., conventional drum) coal

- fired EGUs should be defined as 4 hours after 25 percent load is first reached, or 12 hours after first electricity generation, whichever occurs first. Commenter states
that the 4

- hour timeframe would provide for a transition period while a facility removes the startup fuel and transitions to complete primary fuel firing, shuts down a dedi cated startup system (if applicable),14

and ensures that all emission control equipment can come online safely and within intended design capabilities to achieve full effectiveness. Commenter states that the 12

- hour maximum would cover

situations where the s tartup sequence is delayed for unexpected reasons, but still provides assurance that

a n EGU will not idle at low load. Commenter states that the 6

- hour maximum the EPA suggested in its analysis is not sufficient to address events that might delay the compl etion of startup. Commenter states
that although there are different plant configurations and procedures, many subcritical EGUs will also have higher emissions during startup albeit for different reasons. Based on commenter ’ s experience, the

combination of 25 percent load plus four additional hours will reasonably and broadly address the

situation for subcritical EGUs

.

Comment 7 : Commenter 20400 states that expanding the definition of startup is justified because EGU emissions are different during this per iod. Commenter states that as an example of how emissions are different during startup conditions, it included two graphs of SO 2 and EGU load data for its Zimmer Generating Station during two separate startup events. Commenter states that for SO 2 , they illustrate a characteristic peak in emissions while the proper FGD chemistry is established. Commenter states that peak removal was not achieved until a couple days after the EGU reached full load. Commenter states
that it should also be noted that during the first event, the EGU was started, achieved a relatively high load, but then had to shut down and then immediately went into a second start

- up. Commenter notes this particular startup event lasted over 3 days.

Commenter 20400 states that this particular EGU is one of a number of EGUs that utilize magnesium enhanced lime as a reagent. Commenter states that it is well established that these types of FGD systems require 24

- 36 hours after electricity generation begins before they achie ve their full SO 2 reduction potential. Commenter states that it takes this amount of time to achieve the proper chemistry conditions.

Commenter states that higher levels of excess air at lower loads during a startup retard this process.

Commenter states th at in addition to enabling the best SO 2 removal, proper scrubber chemistry is essential to achieving optimal Hg removal in the FGD system.

Commenter 20400 notes that in its comments, Commenter 20428 has conducted an analysis of startup

emissions from a nu mber of EGUs . Commenter has reviewed these results and supports Commenter

20428 ’ s analysis and conclusions

.

Commenter 20395 states that although the EPA ’ s latest suggested revisions represent improvements over the final rule and the proposed reconsiderati on, it falls short of the “ setting in operation ” of the source, including the emission control devices. Commenter indicates that the General Provisions governing all MACT regulations define startup as “ the setting in operation of an affected source or

port ion of an affected source for any purpose. ” Commenter alleges that as the EPA has suggested defining it, startup would always end within 6 hours after the first electricity production. Commenter maintains that 6 hours after electricity production, however, is not enough time to ensure that that the boiler and associated APCD have reached a safe or stable normal operating condition and that emissions are being effectively controlled for normal operation.

Comment 8: Commenters 20414 and 20430 do not believe that “ 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 ” provides adequate flexi bility for coal

- fired EGUs to ensure safe,15

efficient, and compliant operation. Commenters recommend establishing the end of startup at 25 percent of nameplate capacity plus 4 hours.

Commenter s 20414 and 20430 state that roughly half of the ’ nation ’ s coal

- fired EGUs will take longer than the average EGU to bring a control technology online in the case of median data, exactly half will take longer. Commenters say by using average, and at times median, power plant data, the EPA is establishing a startup stand ard that would inappropriately classify half of the country ’ s EGUs as completing startup when, for many of those EGUs , startup would still be continuing. Commenter 20414

states that this means that, under the EPA ’ s definition of startup, roughly half of th e subcritical and supercritical EGUs (whether using wet or dry FGD technologies) would not have a declining SO 2 emissions rate (i.e., operational FGDs) 3 hours after reaching 25 percent load. Commenter 20414 states
that it also means that half of the subcr itical and supercritical EGUs with SCRs will not have operational SCRs within 6 hours after the start of generation and that half of the CFB EGUs will not be demonstrating SO 2 emission rate reductions within 4 to 6 hours after the beginning of generation.

Commenter 20430 states that the EPAs Startup TSD for NOx indicates EGUs that meet the criteria of having APCDs in service would have declining NOx rates at the end of the proposed startup time but does not indicate they will be in compliance with their ai r permit. Commenter maintains that the end of startup should be at the point where the EGU is capable of meeting compliance with its air permit.

Commenters 20414 and 20430 state the EPA ’ s Startup TSD is also based on the control technologies currently in operation at existing EGUs . Commenters say as the MATS rule is implemented, and the

EPA ’ s numerous other air regulations are finalized, many of the Nation ’ s power plants will be adding new control technologies and control technologies in combinations that have never been used at those respective power plants. Commenters say there will inherently be a learning curve and potential unforeseen problems that would require additional time to bring a plant and control technologies online.

Comment 9 : Commenter 20 425 states that the EPA ’ s proposed definition of “ startup ” does not take into account the uniqueness of different EGUs

– even identically designed EGUs have different operating and startup characteristics. Commenter notes that supercritical and once

- throug h subcritical EGU s rely

on a start

- up/bypass system to bring the EGU up to stable, safe, and reliable operation; these startup/bypass systems are typically designed for 25 percent of nameplate capacity. Commenter states, however, many once

- though design EG Us do not obtain stable, safe, and reliable operation until they are fully isolated from the startup/bypass system and are sufficiently above the transition point from the startup/bypass system to once through operation which is approximately 30 percent of nameplate capacity. Commenter alleges, therefore, that the start

- up period should be tied to 30 percent and not 25 percent for once

- through supercritical and once

- through subcritical EGUs.

Commenter 20425 states EGU startups involve managing and coordina ting the startup and operation of a number of complex systems which must be done in a safe, environmentally compliant and efficient manner. Commenter notes that these systems are typically operating outside of their normal design conditions during startup which makes the control of these systems difficult and susceptible to issues during startup that can lead to unexpected delays in bringing the EGU to a safe, environmentally compliant, stable, and reliable operation. Commenter states that if the startup de finition is based on EGU type then the following criteria should be applied:16

Supercritical and Subcritical once through EGU s

– whichever comes first : 4 hours after achieving 30 percent nameplate capacity, or 12 hours after achieving electrical generation.

Subcritical Drum EGU s

– whichever comes first : 4 hours after achieving 25 percent nameplate capacity, or 12 hours after achieving electrical generation.

FB C EGU s

– whichever comes first : 3 hours after the bed temperature reaches 1500 °F,

or 12 hours aft er achieving electrical generation. As an alternative

– whichever comes first : 4 hours after achieving 25 percent nameplate capacity, or 12 hours after achieving electrical generation.

Commenter 20426 recommends and supports the startup definition propose d by Commenters 20396, 20397, and 20428 . Commenter states that, as an example, Commenter 20428 suggests that the simplest way to define the end of “ startup ” for subcritical (i.e., conventional drum) coal

- fired EGU s like the 11

EGU s Commenter 20426 operates is 4 hours after 25 percent load is first reached, or 12 hours after first electricity generation, whichever occurs first.

Commenter 20426 states that the EPA ’ s proposed definitions do not consider material differences in either the source or the associated air pollution control equipment; a one

- size

- fits

- all definition must expressly allow consideration of the air pollution control processes used in determining the emission limitations that depend on temperature, flow, and/or chemical equilibrium to be effective. Commenter notes that, for safety and operational reasons, when an EGU at one of its facilities is being returned to service, it goes through a startup sequence that includes introducing fire in the boiler with oil lighters and then introducing coal. Commenter states that the coal is introduced one mill at a time until a stable flame is achieved and the oil lighters can be taken out of service; each EGU h as seven mills and at least two or three need to be in service to get a stable flame. Commenter indicates that during this startup period, combustion gases are not routed through the SCRs, but the gas is routed through all other pollution control equipment , including the ESPs and the scrubber

– the SCRs are bypassed during startup for safety and operational reasons as oil carryover during a startup can contaminate the catalyst in the SCR rendering it useless and it can even cause a fire; thus, the gases byp ass the SCR during startup until a stable flame is achieved and the oil lighters are taken out of service. Commenter states

that o nce this step is achieved, the gases are routed through the SCR , it is heated up and, o nce operating

temperatures are achieved, then the ammonia injection is initiated and the SCR becomes operational for

NOx control.

Commenter 20429 notes that should the EPA choose to implement a generic approach, it supports
Commenter 20428 ’ s suggestion that startup should end 4 hours a fter 25 percent load is reached or 12 hours after first electricity generation, whichever occurs first. Commenter states that although this additional time would accommodate more of the startup variability for different EGU designs and from

EGU to EGU and as conditions vary from startup to startup, the third prong of this approach ( “ whichever occurs first ” ) ensures that a n EGU will not be idled at low load.

Comment 10 : Commenter 20417 states that in the June 25, 2013, notice reopening the public comment period (78 FR 38001)

, the EPA suggests that its data analysis supports the possibility of defining the end of startup at coal

- fired EGU as occurring at 25 percent of nameplate capacity plus 3 hours, or the start of17

electricity generation plus 6 hours, whic hever comes first. Commenter states that, as stated in the proposal, commenter s suggest allowing more time for startup by defining the end of startup as occurring at 25 percent of nameplate capacity plus 4 hours or the start of electricity generation plus 12 hours, whichever comes first. Commenter appreciates the EPA ’ s consideration of adding some flexibility to the startup definition. Commenter states that both options do allow for some extra time to bring emission

controls on

- line during startup activitie s.

Commenter 20417 notes, however, taking a “one

- size

- fits

- all” approach to defining how all EGUs are to complete their startup activities will likely force many plants to choose between compliance with the proposed definition of startup (even with the ad ded time noted above) or disregarding manufacturer recommendations, disregarding existing plant procedures that are based on good engineering practices, incurring damage to plant emission control equipment, or creating potentially unsafe work environments, in order to comply with the proposed definition. Commenter states that many of the emission controls (e.g., ESPs and baghouses) that will be used to ensure compliance with the MATS Rule are dependent on temperature for determining the safe and appropriate time to begin their operation. Commenter states that not every EGU at every plant will be able to achieve the appropriate temperatures for proper operation of emission control equipment even within the additional time proposed by the EPA in the proposal.

Commenter 20417 states that, in the EPA ’ s November 30, 2012, proposal ( 77 FR 71323), the EPA recognized that some control equipment takes longer to place in operation than others. Commenter states that, more specifically, in the November 30, 2012, notice, the EPA proposed to exclude additional emission controls from the requirement to be in service when certain fuels were first fired because the

EPA recognized there are certain constraints to their operation. Commenter stat es that, the final MATS Rule currently states that those exempted controls must be started as “ expeditiously as possible. ”

Commenter states that, in the November 30, 2012, notice

, the EPA states that the exempted control systems should “ start as soon as te chnically feasible after the appropriate temperature has been reached. ” Commenter believes this is the better approach than defining startup in the way that the EPA has stated in the June 25, 2013, notice as it recognizes the unique operating constraints o f emission control equipment.

Commenter 20417, in its comments on the November 30, 2012, proposal ( EPA

- HQ

- OAR

- 2011

- 0044

- 5803, p. 5 )

, supports the EPA ’ s proposed expansion of the “ exempted ” emission controls and asks that

the EPA consider adding additional emission control equipment to the discussion due to similar operating constraints. Commenter states that, considering the multitude of issues that are involved in safely bringing emission control equipment online, and that every EGU is different in their operating needs, the best approach may be to provide even greater flexibility in the definition of startup similar to the approach the EPA has taken when additional controls need to be in service when certain fuels are

first fire d.

Comment 11 : Commenter 5840 notes that the time required for startup at each EGU is dependent upon a number of factors including, but not limited to, the EGU type, length of time the EGU has been down, the amount of process water cleanup that is re quire d, and the specifi c work performed during the EGU

down time. Commenter states that e ach step of the startup process is driven by equipment temperature constraints such that boiler steel, fans, turbine

- generator equipment , and other rotating part s are heate d at predetermined rates to allow for expansion and avoid potential damage from metal fatigue.18

Commenter maintains that a startup following outages th at include significant maintenan ce on large components of the boiler (process tubing, piping, headers , duc twork, etc., steam turbine, generator, or other support equipment) can take significan tly more time than if the EGU had simply experienced a trip and was quickly restarted. Commenter alleges that the additional time is required not just for predeterm ined heating rates, but also for chec k and reset of control points, instrument calibration, balancing of rotating equipment, ass u ming that boiler water qual ity requirements are met and other work

necessary to ret u rn the EGU to service and that l ocal weather con ditions can also be a factor in th e length of time it takes to he at EGU components and to retain that heat as startup steps proceed.

Commenter 5840 suggests modification to the EPA ’ s proposed definition of the end of startup.

C ommenter propose s that the e nd of startup be defined as reaching 25 percent of nameplate generation capacity plus 4 hours. C ommenter states that the whichever

- comes

- first approach does account for some of the variability among EGU startup profiles and EGU equipment , but results in a complicated data management challenge and additional burden for emission reporting personnel. Commenter maintains that determining which threshold was reached first will require additional data review and

documentation at all facilities and that this burde n is ignored in the development of the proposed rule. If

the EPA retains a generation plus time definition for the end of startup, Commenter recommends

g eneration plus 12 hours be used

. C ommenter states that the additional time would help avoid

shutdowns t hat could occur due to problems encountered in setup. Commenter believes that in many cases there is little time difference in reality in the EPA ’ s proposed 25 percent capacity plus 3 hours and generation plus 6 hours.

Commenter 5840 maintains that operat ors may have to choose to bring an EGU down rather than continuing a difficult startup to avoid risking failure to meet numerical limits at the point corresponding

to the EPA ’ s suggested end of startup definition which would have the undesirable effect of actually increasing emissions by increasing the number of startups and shutdowns. Given the variability in EGU startup times and the potential for reducing the number of startups, commenter believes that these minor adjustments in the EPA ’ s recommended def inition of the end of startup will result in lower overall emissions, and more efficient and effective engagement of APCD. Commenter believes that the EPA ’ s own assessment of a startup period at coal

- fired EGUs shows that there are supercritical EGUs that do not reach 10 percent of nameplate generating capacity until 6 hours after generation of electricity begins.

Commenter 20428 states that if the EPA insists on an across

- the

- board definition of startup, then the

EPA must lengthen the time periods ; the EP A ’ s suggested 3/6 definition still does not provide adequate time for control equipment to be “ set in operation ” safely and reliably when startup is defined as ending

. Commenters 20395, 20397, 20413, 20414, 20428, and 20430 state the EPA should define star tup as ending: 4 hours after 25 percent nameplate capacity is reached, or 12 hours after initial electricity generation, whichever occurs first. Commenter 20395 further notes that this default definition would apply unless the permitting authority approved an alternative due to unique EGU conditions. Commenter

20428 further clarifie s the three components of its suggested startup definition: 4 hours after 25 percent load is first reached; 12 hours after first electricity generation; and whichever comes first

. Commenter 20428 notes that it intentionally designed its three

- part startup test to provide necessary compliance flexibility to EGU owners and operators during the inherently unpredictable and variable period of startup while providing assurance to the E PA that owners and operators would not “ game the system ” and stay in “ startup. ” Commenters 20414 and 20430 state that the 4 / 12 startup definition would ensure19

that the definition of the end of startup is derived in a mathematically supportable fashion and would provide certainty without undue complexity.

Commenter 20415 notes that the EPA has moved from its initial focus in the 2012 f inal MATS on one

element ( energy production ) to two elements

– boiler load and time

– to define the end of startup and

indicates that this is an improvement over the earlier single

- element approach. Commenter believes that, when considered with the further development of the fuel and emission controls elements of the work practice standards, the EPA ’ s proposed definition o f the end of startup is more reflective of the realities of boiler operations. However, commenter maintains that focusing solely on boiler load is not technically correct or rational because the load at which a boiler reaches stable operations varies widel y, based on fuel type, furnace and boiler design (combustion method), and operating methodologies. Commenter notes that most solid fuel boilers do not reach stable operations until 50 percent load or higher whereas some oil and gas fired boilers can functi on at 20 percent load or less for long duration.

Commenter states that f

ocusing solely on heat or steam production is li kewise unworkable and irrational; u sing that approach, a boiler supplying even a small amount of steam would no longer be in startup and would be required at that point in time to engage emission controls. However, commenter
states that according to equipment specifications and established safe boiler operations, a boiler operator should not engage emission controls until specific paramete rs are met.

Commenter 20415 states that the EPA ’ s more recent thinking

– to combine the boiler load or the energy production with a period of time increases the adaptability of the rule to a wider range of EGU s. Commenter states that this provides a wider compliance margin for boilers that are still operationally in startup at 25 percent load or when electricity generation begins, such that they will still be subject to work practice standards for 3 or 4 hours after 25 percent load, or 6 or 12 hours after electricity generation. Commenter states that the length of time after the load or electricity generation trigger is a very important variable for the EPA to adequately account for as many boiler scenarios as possible.

Commenter states that the greatest flexibility would then be the timeframes at the outer end of those under consideration, i.e., 4 hours after 25 percent load or 12 hours after electricity generation.

Commenter states that if there are boilers that need to operate outside of these parameters, this definition will not rationally reflect all regulated boilers and their operational constraints.

Commenter ’ s 20413 historic plant data reveals that in most startup events the required temperatures

and/or flow conditions can be reached within 25 percent of nameplate capacity plus 4 hours (actual time not Part 75 operating hours) or from the time electricity generation occurs plus 12 hours (actual time not Part 75 operating hours), whichever comes first. Commenter notes however, t here are instances when problems occur during the startup process that will not allow the required temperatures and/or flow conditions to be met in order for all of the pollution control equipment to become properly operational

within the above mentioned t ime

- frame and the EPA final rule must make provisions for such

occurrences.

Commenter 20428 states that the EPA ’ s proposed formulation suggests that the Agency may not fully appreciate the distinct situations that the different parts of commenter ’ s defini tion were intended to

address. Commenter alleges that u nder the EPA ’ s proposed formulation, only during optimal startups

would all control equipment be operating before startup was defined as ending because both time periods under the 3/6 definition would be met at approximately the same time

– a n EGU would reach effective pollution controls about 3 hours after 25 percent load is reached, which will be about 6 hours20

after first electricity generation (because the EGU, according to the EPA, will take 3 hours to reach 25 percent load). Commenter maintains that by stripping the two time periods in the definition of their independent purposes, the EPA renders the “whichever occurs first” language redundant.

Commenter 20428 notes that the “4 hours after 25 perce nt load is reached” is intended to recognize that at EGUs startup, APCDs are not immediately operational. For example, commenter notes that SCRs are not functional until they gradually come up to temperature, and proper scrubber chemistry is not

establishe d until after electricity generation. Commenter states that startup is not over until the EGU has reached normal HAP emissions profile through the operation of fully functional APCD. Commenter states the EPA’s data support providing a minimum of 4 hours af ter 25 percent generation, and not 3 hours. Commenter cites average SO 2 emissions continuing to fall well past 6 hours, further SO 2 reductions after 3 hours, NOx emissions continue to fall between 3 and 4 hours, and the EPA’s average

curve continues to fla tten been 4 to 5 hours, meaning SCRs are still not optimally controlling NOx between hours 4 and 5. Commenter alleges that, given that many EGUs burning eastern bituminous coal will rely on SCRs and scrubbers for Hg control, having a “startup” cutoff of 25 percent capacity plus a minimum of 4 hours is of critical importance to compliance for a significant segment of the utility industry. Commenter states that one member analyzed a dataset of 232 startups (all part of the CAMD data used in the EPA’s Startup TSD) to estimate that during a cold startup for supercritical EGU, the time required to achieve NOx reduction well below uncontrolled emissions, i.e., effective control, is nearly 7 hours after first reaching 25 percent of gross load. Commenter states Hg e missions data support a “4 hours after 25 percent power” test at a minimum.

Commenter 20428 notes the “12 hours after first electricity generation” is intended to deal with situations where startup is delayed for unexpected reasons, equipment consideratio ns, or other reasons out of the operator’s control. Commenter states that this provision will prevent EGUs from operating at low load (i.e., less than 25 percent) indefinitely. Commenter states a 6 hour cutoff is insufficient and clearly inadequate. Commen ter states that the EPA’s Startup TSD shows that during many startup events, subcritical and supercritical EGUs have not even reached 25 percent load 6 hours after generation. Commenter notes that supercritical EGUs lag subcritical EGUs by at least 1 hour in attaining 25 percent power after initial generation. Commenter states the EPA admits that APCD are not fully functional when 25 percent load is first reached. Commenter maintains that the EPA’s Startup TSD confirms 6 hours after initial generation on “a verage” is not when pollution controls are fully functional. Commenter states that the EPA asserts that average and median NOx emission rates begin to decline around hour 6. Commenter notes that pollutant levels for both supercritical and subcritical EGUs continue to fall between hours 6 and 12 after first generation, average NOx emissions for supercritical EGUs continue to fall significantly between hours 6 and 12, and average SO 2 emission for subcritical EGUs with dry scrubbers fall noticeably between hou rs 6 and 12. Commenter states Hg data support extending the time period because there are marked spikes in subcritical EGUs in 9 out of 10 startup events after hour 6 following initial electricity generation.

Commenter 20428 notes that the “whichever occu rs first” language is to ensure that any startup event will be as short as possible. Commenter states that it only supports use of the “whichever occurs first” language if it functions as originally intended, and its purpose is lost under the EPA’s 3/6 def inition.

Commenter 20397 states a one

- size fits all definition is inappropriate.21

1.1.1.3 25 percent plus 7 or 8 hours

Comment 12: Commenter 20406 suggests that the startup definition allow for at least 8 hours to elapse which would allow both stages of the PM controls to be adequately functioning. Commenter notes that this period would be in accord with its Title V permit, which allows a startup period of up to 8 hours for staged startup of the emissions controls to occur from the synchronization of the EGU to the grid (which requires the start of coal firing in the EGU). Commenter notes that after that time, the ACI injection must still be initiated. In addition, commenter’s facility utilizes a halogen based sorbent enhancement additive (SEA) injected d irectly into the furnace of the EGU as part of the Hg removal system. Commenter states that, as the injection of the SEA can increase halogen acid

- gases if it is started prior to startup of the wet FGD, the FGD must be brought on

- line and stabilized prior to startup of the SEA portion of the Hg emission controls. Commenter concedes that it does not always take the full 8 hours to achieve operation of all the control equipment, but that time is required when performing a cold startup.

Commenter 20406 mainta ins that, additionally, large EGUs like those at its facility cannot sustain operation at 25 percent of nameplate capacity without supplemental firing of oil or natural gas. Therefore, commenter’s EGUs typically attain 25 percent of nameplate capacity with in the first 1 to 3 hours of firing coal. Commenter explains that requiring that startup end within 3 hours of attaining 25 percent of nameplate capacity is impractical for large EGUs and can substantially shorten the proposed time allowed for startup with out actually reducing the time required to get all the emissions controls operational. Commenter states that the requirement for initiating operation of all emission controls related to 25 percent of nameplate capacity must be eliminated or extended to all ow startup of all the required emission controls. Commenter maintains that if a time period following 25 percent capacity is included, then a period of 7 hours following 25 percent capacity must be allowed. Commenter

recommends that the EPA define the end of startup as “The start of electricity generation plus 8 hours of continuous operation” as this gives a definite period and allows adequate startup of large EGUs.

Commenter 20418 recommends the removal of any reference to a strict hour limitation from th e definition of the end of startup and recommends instead a load value of 25 percent plus 7 hours.

C ommenter states that a startup period solely defined by a certain time allotment after grid synchronization cannot account for the various conditions and re quirements that must be met following specific maintenance activities. Commenter maintain s that it is more appropriate to define the end of a startup period by the percentage of rated load, providing flexibility during situations where there is an

unavoida ble extended cold start.

Commenter 20418 states that hot starts are the most common type of start and are typically the result of processes being slightly out of control causing an EGU trip and that a warm start is often the result of a failed component w ithin the boiler itself (such as a tube) that requires repair. Commenter indicates that the time period between combustion within the furnace is typically driven by temperature exposure concerns, requiring some duration of time to allow the boiler to cool to a temperature that makes it safe for employees to perform the appropriate repair. Commenter notes that cold starts (which often are not a matter of choice) are typically the result of a maintenance outage in which necessary repairs are made to

the steam turbines, combustion equipment, and APCDs to correct any operational or performance issues and that the time required to successfully control emissions after a cold start is typically longer than that of a warm or hot start, primarily due to the numerous safety checks required after such intensive work.22

Commenter 20418 indicates that cold starts requires several hours, if not days, to get the EGU to an appreciable load; these slow starts are costly to the utility because of the low levels of electricity

g enerated during these time periods. However, commenter alleges that it is important to maintain the slow ramp rate for the health of the equipment, the integrity of the structural materials, and most importantly, for the safety of plant personnel.

Comment er 20418 discusses the approach that the EPA used to develop the point to define the end of startup as 3 hours after 25 percent load. Commenter notes that the EPA’s analysis only addresses time periods in which the average facility begins to indicate that it has achieved a minimum level of pollutant control and alleges that this method does not adequately determine the point at which emission rates are “well below” uncontrolled levels. Commenter maintains that it is inappropriate to point to the first chang es in the average trend to indicate that it is appropriate to end startup at that point. Instead, commenter states that the EPA must evaluate the point at which emission levels are “well below” uncontrolled startup levels. Commenter reviewed the dataset in the proposed rule’s docket and derived a smaller data set of only cold starts in order to look at how many hours may be necessary to achieve NOx emissions “well below” uncontrolled levels after the EGU has achieved 25 percent of the gross rated

load. Comm enter states that because of the wide variety of start events and scenarios that can be incurred, it is impossible to establish a time limit that would be appropriate for every start event, but commenter stepped through its analysis and concludes that the end of start

- up at a coal

- fired EGU occurs when the EGU load reaches 25 percent of nameplate capacity plus 7 hours.

1.1.1.4 25 percent plus 7 hours or generation plus 10 hours

Comment 13 : Commenter 20420 states that the EPA should define the end of the startup period as occurring when an EGU reaches a steady state controlling SO 2 at th e MATS emission limit of 0.20 pounds (lb) /MMBtu. Alternatively, commenter states that the EPA should define the end of startup differently for PC and CFB EGU s. C ommenter suggests that for PC EGU s, startup should end 7 hours

after the EGU achieves 25 percent nameplate capacity or 10 hours after the onset of generation,

whichever occurs later. Commenter suggests that for CFB EGU s, startup should end 13 hours after the

EGU achieves 25 percent nameplate capacity or 19 hours after initial generation of electricity,

whichever occurs later.

Commenter 20420 operates its EGUs under the “ Start

- up and Loading Instructions ” (SALI) prepare d by GE, the manufacturer of its PC and CFB turbine generators. Commenter notes that the SALI requires that the turbines heat soak to allow metal temperature equilibration of the crossover and turbine for 60 minutes after the onset of generation up to or a t 2 percent load. This heat soak period is designed to prevent temperature mismatch, which is detrimental to the turbine generator sets according to

manufacturers ’ recommendations. Therefore, commenter maintains that per SALI, one hour is required during e very EGU startup for the turbine soak to be completed before startup may continue.

Commenter 20420 provides an analysis (utilizing the Part 75 diluent cap) of hourly EGU operating data obtained from the CAMD database for January 1, 2012, through March 31, 2013, for the four coal

- fired EGUs at its Spurlock Generating Station (Spurlock) and Unit 2 at Cooper Generating Station (Cooper)

to determine whether the EPA ’ s Startup TSD conclusions support actual operating experience with these EGUs. Commenter states that the results show that Spurlock 1 and 2 (wall

- and corner

- fired PC EGUs, respectively) achieved 25 percent of the rated nameplate capacity within 3 hours of generation for warm23

and hot start events, although both EGUs do not consistently achieve 25 percent of the rated nameplate capacity within 3 hours of generation for cold start events. Commenter notes that b oth EGUs were able to achieve 25 percent of the r ated nameplate capacity within 4 hours of g eneration in all cases, however,

but that t he data also show significant variation in the time required to achieve controlled SO 2 emissions.

Commenter indicates that f or Unit 1, controlled emissions were achieved within 4 hours of generation

and within 3 hours of achieving 25 percent nameplate capacity in all cases whereas for Unit 2, the time required to achieve controlled emissions varied significantly between all startup events and each type of

startup. Commente r states that data for cold start events, which require the longest startup duration, showed the average time to achieve controlled emissions was approximately 8 hours after generation and over 4 hours after achieving 25 percent nameplate capacity. Comment er states that although average

cold

- start duration is comparable to both of EPA’s proposed startup definitions, the range in duration significantly exceeds these thresholds and the data show that it may require up to 14 hours after generation and 10 hours after achieving 25 percent of the nameplate capacity to achieve controlled SO 2 emissions.

Commenter 20420 states that f or Spurlock Units 3 and 4 (CFB EGUs) the data show that neither EGU typically achieves 25 percent nameplate capacity within 3 hours of generation and achieving this load takes much longer than for Units 1 and 2, particularly for cold

- start events. Commenter indicates that the data for Unit 3 show that up to 12 hours may be required to achieve 25 percent nameplate capacity for

some cold st art events and the data for some cold

- starts show that up to 15 hours after the onset of generation or 7 hours after the EGU achieves 25 percent nameplate capacity may be required for the EGU to achieve controlled emissions. Commenter states that for Unit 4, the data show that up to 20 hours after generation or 15 hours after achieving 25 percent nameplate capacity may be requi red for the EGU to achieve controlled emissions. Commenter observes that both boilers have identical designs and the difference in startup duration between the two boilers highlights the variability in CFB startup profiles.

Commenter 20420 states that the SO 2 emissions profile for Spurlock 4 for a selected warm

- start event shows that the limestone feed is engaged approximately 5 hours after the onset of generation; it then takes an additional 8 hours for the bed to stabilize and to obtain partially control led SO 2 emissions below 0.20 lb/MMBtu. Commenter indicates that the spray dryer adsorber (SDA) is engaged approximately 28 hours after startup once the EGU achieves the minimum flue gas temperature after which the EGU operates with fully controlled SO 2 emi ssions. Commenter maintains that this example clearly demonstrates that the proposed alternative startup definitions do not adequately characterize

controlled SO 2 emissions for a typical CFB startup.

Commenter 20420 states that the SO 2 emissions profile f or Spurlock 4 for a selected cold

- start event where the data show that emissions are substantially controlled approximately 44 hours after startup. Commenter maintains that this example demonstrates the variability in startup duration for CFB EGUs

and furt her illustrates that the proposed alternative startup definitions do not adequately characterize SO 2 emissions for a typical CFB startup.

Commenter 20420 states that the results for Cooper 2 (wall

- fired PC EGU) were similar to those of the Spurlock PC EGU s. Commenter indicates that the EGU achieved 25 percent of the rated nameplate capacity within 3 hours of generation for both of the startups evaluated; the data also show significant variation in the time required to achieve controlled SO 2 emissions

– 3 t o 13 hours from the onset of24

generation or 8 to 13 hours after achieving 25 percent nameplate capacity. Commenter alleges that greater variability and duration of EGU startup is expected for this EGU compared with the Spurlock PC EGUs and other EGUs equipp ed with dry FGD because the EGU is equipped with a unique circulating dry scrubber (CDS) which has minimum operating temperature requirements similar to conventional SDA, although it also requires additional time to establish a stable fluidized bed, which is complicated by the dynamic nature of a EGU startup.

Commenter 20420 notes that the EPA Startup TSD concludes that there are no significant differences in the startup characteristics of PC and CFB EGU s. Commenter disagrees with this statement based on i ts analysis of emission data from typical operation of the Spurlock EGUs where the elapsed time required to achieve initial generation, 25 percent nameplate capacity, and controlled emissions is notably different between the PC EGUs (Spurlock Units 1 and 2 and Cooper Unit 2) and the CFB EGUs (Spurlock Units 3 and 4). Commenter believes this finding is not surprising considering the fundamental differences in operation and the method of SO 2 emissions control noting that for Spurlock Units 1 and 2,

the wet sc rubbers begin operation on first fire, and

, therefore, begin to provide some immediate emissions reduction where limestone injection on Spurlock Units 3 and 4 requires a minimum operating bed temperature which is typically achieved only at about 70 MWg for a cold start. Commenter maintains that additional time is required to achieve the minimum flue gas temperature necessary to engage the SDA, which is typically achieved at about 170 MWg for a cold start event.

Commenter 20420 finds there are two fundament al flaws that contribute to its findings. First, commenter

believes that the EPA assumes that the SO 2 emissions control system stabilizes at each of the proposed operating points resulting in emissions that are substantially controlled. Commenter alleges t hat although its data shows that this is generally true for the conventional boilers at Spurlock, it is definitely

not true for the CFB EGU s, particularly for cold start events. Commenter recommends that the EPA consider an alternative approach to selectin g the termination of EGU startup based on when the EGUs

achieve controlled emissions that are below the MATS SO 2 emissions standard (in order to remove any bias in this analysis, commenter recommends only including data from those EGUs that can meet the

em issions standard with a 10

– 20 percent margin of compliance). Commenter believes that this approach provides a clear indication of when the SO 2 control equipment is fully in service that is still somewhat conservative because EGUs will operate below this level during normal operation. Commenter also concludes that the EPA did not properly characterize variability in the startup duration for individual EGUs and between different EGUs. Commenter notes that the EPA’s analysis is based on the average values of its sample population, which suggests that half of the startup events are not adequately characterized by the proposed operating points. Commenter’s analysis of its data shows that the range in startup duration can be significant for individual boilers of the same type, particularly for

the CFB EGU s. Commenter recommends that the EPA provide further consideration of EGU operating variability in selecting the termination of EGU startup. Commenter believes that alternatives could include selecting the approp riate range based on the 90 th or 95 th percentile values or by applying an upper prediction limit (UPL) approach similar to the one used in the MATS floor analysis. Based on commenter’s findings, it recommends that the termination of EGU startup for PC boil ers should be 7 hours after achieving 25 percent nameplate capacity or 10 hours after the onset of generation, whichever

occurs later and for the CFB EGU s, the termination of EGU startup should be 13 hours after achieving 25 percent nameplate capacity or 1 9 hours after initial generation of electricity, whichever occurs later.

Commenter indicates that these recommendations are based on the 90 th percentile value for the available cold start data for each respective boiler type.25

1.1.1.5 50 percent plus 3 hours or generation plus 9 hours

Comment 14 : Commenter 20398 states that the EPA ’ s end of startup definition would likely pose compliance issues for affected facilities. Commenter suggests end of startup at coal

- fired EGUs be

defined as when the affected EGU achieves 50 percent of nameplate capacity plus 3 hours or the start of electricity generation plus 9 hours, whichever comes first.

1.1.1.6 Generation plus 12 hours

Comment 15 : Commenter 20401 states that the definitions of startup and shutdown incorrectly identify their ending and starting points, respectively, because EGU startup does not end at first electric generation, and the EPA ’ s proposed definition of shutdown does not adequately characterize the time at which shutdown begins.

1.1.1.7 APCD ’ s in service

Comment 16 : Commenter 20389 supports defining startup to include placing APCD equipment into service using manufacturer recommended practices that protect APCDs.

Comment 17 : Commenter 5834 expresses general support of the proposed bright

- line test (78 FR 38005) for defining the end of startup, but only if changes are made to Table 3 to subpart UUUUU to acknowledge that APCD operation must be phased in until they can be operated in a safe and feasible

manner.

Comment 18 : Commenters 20396, 20397 and 20428 disagree with the EPA ’ s proposed definition , but they did not provide suggestions for other definitions. Commenter 20396 seeks a workable definition of startup that is both environmentally protective and allows for safe operation of APCDs. Commenter

20396 states EGUs cannot comply with the stringent standard unless APCDs are functioning optimally.

Commenter 20397 states the EPA m ust allow consideration of the nature of the APCD used in determining emission limitations, some of which depend on temperature, flow, and/or chemical equilibrium to be effective , and recommends that the EPA include startup and shutdown definitions that

ta ke into consideration distinctions between both the EGU sources and their APCDs . Commenter s 20397 and 20426 note that when defining work practices, the definitions of both the source and control

device will dictate when “ startup and shutdown ” periods begin and end, such that compliance with the emission limits, which were based mainly on a one

- time full load steady state condition, better match the conditions utilized when setting the limits

. Commenter 20426 notes that although this may make the compliance plans for individual EGUs somewhat more complicated, the owners and operators will be in a better position to assure compliance and that

, because the rule requires monitoring at all times, the

EPA can request and evaluate whether there are excess emissions during those periods and address those

conditions on a case

- by

- case basis.

Commenter 20396 states many APCDs require certain temperatures and pressures in order to achieve

maximum emissions reductions.26

Commenter 20428 states that the EPA ’ s end of startu p definition does not provide adequate time for APCD equipment to be “ set in operation ” safely and reliably. Commenter 20398 states that additional time is needed for APCD equipment to be operated safely and effectively to meet emission limits.

Commenter 2 0405 believes it imperative that the EPA provisions associated with periods of startup and

shutdown recognize the practical workings of APCD equipment. Commenter 20405 further states the rules should ensure the safe operation of the source, control equipme nt and auxiliary equipment such that the owner does not have to endanger plant personnel to comply with startup, shutdown, or

malfunction (SSM) provisions.

Commenters 20396 and 20408 express concerns that any attempt at a “bright

- line” generic rule cannot safely and adequately address all EGU types and APCD configurations. Commenter 20408 provides three examples where having to incorporate the measured concentrations, as required by the current definition of end of startup, in the 30

- day compliance average will make it even more difficult to comply with stringent utility MACT standards and will be compounded if the EGU has multiple startups during

the 30

- day averaging period. Commenter 20408 maintains that the EPA needs to define the end of startup as the t ime when emission controls and boiler system are in stable operation which, typically, is dependent on the boiler type; tangential boilers will reach stable load sooner than cyclone boilers.

Commenter 20408 states that cleaning of the internals of boiler tubes and other boiler steam

- carrying components are required on a periodic basis and that typically the chemicals used in the boiler steam handling system cleanings require the cleaning solution to be heated as it is circulated thru the steam system which is typically done by heating the boiler with its startup fuel. Commenter indicates that under the current MATS rule language, this would be considered a startup even though there is no intention for the boiler to generate steam or electricity. Commenter s tates that additionally at times during startup or shutdown a boiler will maintain fire in the boiler but will not generate MW (e.g., where you are curing refractory, performing turbine bearing rub outs, or turbine and boiler feed pump testing).

Commenter states that the EPA needs to specifically exclude such operations from emissions monitoring where it is clear that there is no intention to perform a normal startup or shutdown.

Comment 19 : Commenter 20404 notes that utilizing a more flexible definition m ight exclude certain

EGU s from complying with the rule, and an alternative petition approach should be available to such

EGU s.

Commenter 20401 agrees with other commenter s that using the point when an EGU generates electricity as the end of startup is not appropriate. Commenter states that electric generation and startup are two distinct processes; start

- up ends and operating begins only after the EGU has achieved stable load and air quality control devices are properly placed in operation, which is typica lly well after electric generation has begun to occur. Commenter notes that electrical generation typically begins before primary air (PA) fans to coal mills are turned on or coal is first introduced and that the introduction of coal does not signal that t he startup process is over because the EGU is still ramping up in load with additional coal mills and associated PA fans being put into service; it is only after these steps have occurred and the boiler is in stable operation that startup for the boiler it self has ended. Commenter maintains, however, that even at that time, startup of the entire EGU has not ended because additional time is needed to achieve safe operating conditions for some emission control devices (i.e., SCRs)

.27

Commenter 20401 notes that startup duration can vary significantly, depending on whether the EGU goes through a cold startup (e.g., after a long maintenance outage) or a hot startup (e.g., after a short outage). Commenter states that in the case of one of its wall

- fired boilers, a typical hot startup process takes approximately 12 hours

– 3 of which are after electric generation has already begun whereas a cold startup for this boiler typically takes approximately 26 hours

– 8 of which occur after electric generation has already beg un. Commenter maintains that these estimates do not consider the additional time required if boiler equipment issues occur, or if the EGU trips during startup, which is not uncommon. Commenter alleges, therefore, that first electric generation is not in re ality a true indicator of the end of startup and beginning of normal operation.

Comment 20: Commenter 20404 requests the definition of “startup” ensure emissions during these periods are minimized to the extent possible in a manner that is consistent with safe and effective operation of EGUs and pollution control equipment. Commenter concurs wit h Commenter 20428’s comments that the EPA’s data set for setting the “3/6” option neglects too many outliers in the data set which show true operational variability and that the data analysis demonstrates that more time is needed

to ensure that controls ar e operating adequately across the range of EGUs to which the generic definition of “startup” would apply. Commenter agrees that the definition of startup should be revised to note that startup ends 4 hours after 25 percent nameplate capacity is reached or 12 hours after first electricity generation, whichever comes first.

Commenter 20408 states that ending “startup” when electricity is first produced does not account for the time needed to set the boiler and its associated air pollution control equipment i nto operation, and that the full startup can take 20 hours or more. Commenter provided an informative example of a staged startup with a cyclone boiler EGU. Typically, cyclone boilers have 10

- 20 individual cyclones. A typical startup procedure for a cycl one boiler is to warm 1

- 3 cyclones using startup fuel and as these cyclones come up to temperature the operator begins feeding the primary fuel (e.g., coal). After these initial cyclones are on line and using coal the EGU will typically begin generating electricity rather than waste this energy in the steam cycle. The remaining cyclones are brought on line in the same manner incrementally. The boiler is thus not fully finished with startup until all available cyclones are online

which could take 20 hours or more for a normal startup. Commenter indicates that the definition should reflect the length of time or achievement of operational parameters actually needed to set an EGU into stable operation. Commenter states further that it is not to the benefit of an EGU to delay in startup as heat rates during startups are 15

- 20 percent higher and, thus, the longer the startup the more energy wasted which drives up costs.

Comment 21 : Commenter 20393 states that an examination of the historical data in the EPA ’ s Startup

TSD for the proposed “ one size fits all ” approach clearly demonstrates the infeasibility of the EPA ’ s initial proposal of defining the end of startup as being when the EGU first generates electricity for sale and, specifically, shows that coal

- fuel ed EGUs, on average, will need much longer periods of time after first generation of electricity before they can begin normal operations and properly start up all of its

APCDs.

Comment 22: Commenter 20390 provides several points regarding the EPA’s Startup TSD document. Commenter agreed that the EPA correctly identified the three general classifications of startup used in the power industry. Commenter notes that in analysis of data in Figure s 9, 10, 12, 13, 14, 16, 21, 22, etc., the EPA did not appear to analyze the data for each of the three startup conditions separately but28

appears to aggregate the startup data. Commenter states the emissions and time limitations should be evaluated separat ely and the EPA did not differentiate startup requirements or timing based on the differences. Commenter also notes that the EPA’s “average” start is skewed heavily by hot restarts. Commenter states that the EPA should use the upper boundary of the 95 perc ent confidence levels to make certain that plants can comply and not use the average or median to develop conclusions. Commenter notes that the quartile data range is significant in every chart and indicates many EGUs many not be able to comply with the ti me limits the EPA proposed. Commenter also notes that several consent decrees require NOx emission in the range of 0.05 to 0.07 lb/MMBtu, however data in Figures 13, 14, 21, and 22 indicate SCRs do not reach these levels. Commenter states that the EPA did a startup analysis of SCRs but that they are not integral to MATS.

Comment 23: Commenter 20419 states that the proposed definitions for the end of startup will force many EGUs to choose between compliance and risking equipment damage and emissions increas es. Commenter states that although the proposed definitions for the end of startup in the Proposed Reopening are workable for some EGUs, they are impracticable for others. Commenter states that the Proposed Reopening states that commenters request that the end of startup be changed to 4 hours after 25 percent load is first reached, or 12 hours after first electricity generation, whichever occurs first. (Commenter notes that this proposed definition does not represent a consensus approach among industry

comm enters .) Commenter states that the EPA alternatively proposes to define 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. As expl ained in commenter’s prior comments, defining the end of startup based on when electricity is first generated will not work at many EGUs due to site

specific limitations on startup procedures. Commenter maintains its position on this issue . Commenter

state s that these proposed definitions are appropriate for some EGUs but are too restrictive for others

due to site

- specific factors. Commenter states that, as a result, the proposed definition could force many EGUs to choose between noncompliance and risking c ontrol equipment damage and increased emissions, because such EGUs will be unable to start their emissions control equipment safely by the end of “startup” as the EPA proposes to define it.

Commenter 20419 agrees with the EPA that certain emissions contro l devices have specific temperature requirements for proper operation. Commenter urges the EPA to consider that, in addition to implementation of emissions control devices depending on temperature, the time it takes to reach the requisite temperature is di fferent at every plant. Commenter states that although MATS, as finalized,

allows EGU s to start their “ SCRs ” and dry scrubbers “ appropriately to comply with relevant standards applicable during normal operation, ” in recognition of this unit

- by

- unit diversi ty, it appears that the

EPA ’ s proposal to change the definitions for the end of startup could instead require EGU s to put all control devices into service at the end of startup. Commenter indicates that the EPA ’ s Startup TSD suggests that the EPA believes that SCR and FGD can be put into service 3 hours or less after reaching 25 percent of nameplate capacity or 6 hours or less following the start of electricity generation. Commenter supports the current language in the MATS that allows EGU s to sta rt their SCRs and dry scrubbers as appropriate to comply with the numerical emissions limits applicable during normal operations. Further, commenter urges the EPA to consider that operation of other types of controls are similarly temperature

- dependent; ce rtain EGU s are unable to put such controls into service at the end of startup as the EPA proposes to define it.29

Commenter 20419 notes that at certain members ’ EGUs, the minimum temperature and air flow conditions required for starting SCRs and scrubbers s imply are not achieved by the time the EGU reaches 25 percent of nameplate capacity plus 3 hours, or the start of electricity generation plus 6 hours. Commenter states that influencing factors include how long the EGU was down, the ambient

temperatures, an d delays in being able to raise EGU load. Further, certain of commenter ’ s members ’ EGUs are still burning 100 percent natural gas by the time the EGU reaches 25 percent of nameplate capacity plus 3 hours, or the start of electricity generation plus 6 hours

. Commenter believes that these EGUs should not be required to start operating scrubbers when they are still burning only natural gas simply because the EPA has defined startup as ending within a certain number of hours; if natural gas or

another clean fue l is the only fuel being burned, the implementation of control equipment should be allowed to be delayed until operating conditions are acceptable to place the control equipment in service. Commenter provides an example of 16 startup events over the past 1 2 months (which included hot, warm, and cold startups) where one member ’ s 3 EGUs have been (1) unable to put scrubbers into service by the time the EGUs reached 25 percent of nameplate capacity plus 3 hours, or the start of electricity generation plus 6 ho urs, whichever came first; and (2) unable to put the scrubber into operation within 4 hours after 25 percent load was first reached, or 12 hours after first electricity generation, whichever occurred first. Commenter alleges that these data confirm that th e EPA ’ s proposed definitions for the end of startup are not workable at these EGUs, and that the end of startup for some EGUs must be based on temperature instead of hours.

Commenter 20419 maintains that the EPA ’ s proposed approach unnecessarily risks equipment and emissions increases by forcing plant workers to disregard existing plant procedures and start controls before it is safe to do so to avoid noncompliance. Commenter states that flowing ammonia to the SCR or reagent to the scrubber when temperatures are too low will result in equipment damage and that if dry scrubbers are placed into service before the proper temperatures have been reached, the reagent may plug the scrubber, rendering the scrubber ineffect ive and requiring the EGU to shut down to clear out the

vessel. Commenter notes that at one member ’ s EGU, the operator must use hot flue gas to warm the 800,000 gallons of cold lime slurry for several hours before allowing the flue gas to pass through the

scrubber towers. Commenter states that i f it were to allow the flue gas to pass through the scrubber towers instead of a by

- pass before the slurry reaches the necessary temperature, the cold, moist gas exiting the module would turn the stack into a wet sta ck; because the stack was not designed for wet gas, the moisture in the stack would increase the likelihood of corrosion of the stack lining. Commenter alleges that s tarting SCRs or selective no n

- catalytic reduction systems (SNCR ) before the requisite

temp erature is reached also may lead to increased emissions. Commenter further notes that i f EGUs were required to flow ammonia to an SCR, or ammonia or urea to an SNCR, before the flue gas reached the necessary temperature for the reagent to optimally react w ith NOx, then ammonia slip would increase; a mmonia slip results in higher emissions of PM 2.5 and PM 10

.

Commenter 20419 acknowledges that particulate control equipment and Hg control equipment may be ready to put into service by the time the EGU reaches 25 percent of nameplate capacity plus 3 hours, or the start of electricity generation plus 6 hours. Commenter believes that t he EPA could address this through issuance of a work practice standard for such equipment rather than developing a definition of startup that is unreasonable for certain site

- specific applications of air pollution control technology

. Commenter states that the EPA ’ s proposed definitions would require plants to put controls into service before it is technically possible to do so witho ut damaging equipment and increasing emissions.

Commenter states that the EPA ’ s one

- size

- fits

- all approach to startup is inappropriate and unworkable30

given the broad diversity of plant equipment, pollution control devices, and startup procedures that are

d esigned to protect equipment. Comment concludes companies should not have to choose between operational safety and noncompliance during startup.

Comment 24: Commenter 20419 urges the EPA to recognize that its own data demonstrate that many plants will be unable to comply with the proposed definitions for the end of startup. Commenter states

that the 3

- hour definition is based on average performance of EGUs examined in the Startup TSD, meaning that a number of EGUs take longer than 3 hours to implement thei r emission control devices. Commenter states that the EPA should not set a standard that is fundamentally incompatible with the operation of certain EGUs. Commenter states that it is technologically impossible for such EGUs to start

their emissions control equipment any sooner in the startup process without risking equipment damage and creating environmental concerns. Commenter states that the EPA has offered no justification for developing a proposed definition of startup that a certain percentage of EGUs will simply be unable to meet according to the Agency ’s own analysis.

Commenter 20419 also believes that the Startup TSD supports identifying a later endpoint for the startup process than the one proposed by the EPA. Commenter states that the EPA bases it s proposed startup definition on the average time it takes for EGUs to begin operating their emission controls, rather than the time it takes for control devices to reach removal efficiency consistent with normal operations.

Commenter states that this guar antees that EGUs will be unable to comply with the emissions limits that apply at the end of startup, as the EPA proposes to define it. Commenter states that the Startup TSD

notes that “ on average, all types of EGUs in this study...can begin controlling SO 2 and NOx emissions 3 hours or less after reaching 25 percent of nameplate capacity... ” Commenter states that the EPA focuses its analysis on when emission controls appear to begin reducing emissions, but its own data show that

emissions continue to trend d ownward for multiple hours until they reach a steady state. Commenter

states that accordingly, defining the end of startup as the beginning of the downward trend identified in

the EPA ’ s own data and before EGUs enter normal operations will result in many E GUs operating above their emission limit for several hours, which would jeopardize compliance. Commenter indicates

that a 30

- day rolling average compliance period may not be sufficient to allow a n EGU to operate for several hours above its emission limit, particularly if the EGU has more than one startup in a 30

- day rolling average period

.

Comment 25 : Commenters 20414 and 20430 note that the EPA ’ s 3

- hour and 6

- hour time frames are based on the findings of the EPA ’ s Startup TSD , , which commenter s believe to be flawed. Commenters said that the EPA should not have relied on an average (or median) time of emissions reduction to establish the time period to declare the end of startup.

Commenter 20410 notes in the Startup TSD , the EPA states that on average, all types of EGUs in the study can begin controlling SO 2 and NOx emissions 3 hours or less after reaching 25 percent of nameplate capacity or 6 hours or less following the start of electricity generation. Commenter states that

if the thre sholds provided are the average time for a n EGU , then half of the time EGU s will not begin controlling emissions within the given timeframes. Commenter states that it is not reasonable to establish a requirement in a regulation where it is expected that co mpliance will be met only 50 percent

of the time.31

Comment 26 : Commenters 20417 and 20419 support the definition of “ startup ” as “ the setting in operation of an affected source, ” provided that this definition includes the ignition of fuel in the boiler, production of steam to begin generating electricity either before or after the primary fuel is added to the boiler, and placing in

- service the emissions control equipment. Commente rs note, “ startup ” must include the requisite time to achieve the temperatures necessary to engage emission control equipment.

Comment 27 : Commenter 5840 states that a definition for the end of startup that does not allow for the

EGU to achieve its normal state of operation with all equipment fully functional will result in the

inclusion of emissions rates in 30

- day averages that are actually associated with startup conditions rather than normal (design) operations.

Comment 28 : Commenter 20421 expresses c oncern that the definition of startup does not reflect actual boiler operating characteristics of its coal

- fired stoker boilers. Commenter shares the principal concern of the majority of other commenters that startup does not end when electricity or useful thermal energy is produced. C ommenter recommends that , to be rational, the end of the startup period must be at a time when the boiler operating conditions have stabilized and all APCDs are in service. C ommenter defined this point as when all associated o perator control functions have been completed, the plant is capable of steady state operation, normal boiler

- related and steam cycle temperatures and pressures have been achieved, and all systems normally required for continuous operation have been placed into service.

Comment 29 : Commenter 20401 suggests that the EPA revise the requirement in the final rule that all emission control devices, with the exception of limestone injection in FBC EGUs, dry scrubbers and selective catalytic, and non

- catalytic reduction systems shall operate when coal, solid oil

- derived fuel, or residual oil is fired. Commenter states that the startup definition in the final MATS rule should be revised to account for the time needed for proper and safe operation of air quality control equipment, which will, in turn, lead to reduced overall emis sions.

Commenter 20416 supports the revised definition for the end of startup, however; the EPA needs to take into consideration that the revised startup definition is not specific to all combustion technologies.

Comment 3 0 : Commenter 20410 suggests the following ways to handle startup and shutdown periods in the MATS rule, listed in order of preference:

(1) Commenter states that review the data and set the end of startup based on when a significant majority, say 95 percent, of the startups would have a ll pollution control equipment effectively operating, not using the point where the average source will have

controls on

- line (and presumably 50 percent of sources wouldn ’ t have controls effectively on

- line). Commenter states that the defined end of startu p and beginning of shutdown should be used to define when the source must start and end, respectively, using emissions data in demonstrating compliance with the MATS limits. Commenter

states that the regulation should not include provisions that require co ntrol equipment be brought on line at a specified point in time during startup or remain on

- line until a specified point in time during shutdown. Commenter states that the fact that startup ends at a given point in time and emissions begin to be counted to ward compliance with the emissions limits will be incentive for sources to get all controls to optimal operation in a timely manner. Commenter states that this will serve the purpose of the regulation,32

limiting emissions of HAP, but will not force sources to operate equipment in a manner that may be unsafe or that may damage the control equipment.

(2) Commenter states that review the data and set the end of startup based on when a significant majority, say 95 percent, of the startups would have all polluti on control equipment effectively operating, not using the point where the average source will have

controls on

- line (and presumably 50 percent of sources wouldn ’ t have controls effectively on

- line). Commenter states that the defined end of startup and begi nning of shutdown should be used to define when the source must start and end, respectively, using emissions data in demonstrating compliance with the MATS limits. Commenter

states that if the EPA determines that the regulation needs to address use of cont rol equipment relating to startup and shutdown, it suggest s that the following language be

used:

During or shortly after a startup period, needed pollution control equipment shall be engaged as expeditiously as possible, considering safety, good engineeri ng practices and manufacturers ’ recommendations. Shutdown begins when pollution control equipment that is necessary to comply with the applicable emission limits under this Subpart are disengaged. Needed pollution control equipment shall remain engaged prior to shutdown as long as possi ble, considering safety, good engineering practices and manufacturers ’ recommendations

.

(3) Commenter states that define the end of startup and beginning of shutdown based on when pollution control equipment can be engaged or disengaged considering safety and

manufacturers ’ recommendations, as follows:

Startup ends when all pollution control equipment that is necessary to comply with the applicable emission limits under this Subpart are engaged. Needed pollution control equipment shall be engaged as exped itiously as possible, considering safety, good engineering practices

and manufacturers ’ recommendations. Shutdown begins when pollution control equipment that is necessary to comply with the applicable emission limits under this Subpart are disengaged. Nee ded pollution control equipment shall remain engaged prior to shutdown as long as possible, considering safety, good engineering practices and

manufacturers ’ recommendations

.

(4) Commenter states that define startup as suggested in bullet item 1 above for purposes of defining when emissions are included in the compliance demonstration. Commenter

states that use the following criteria for engagement of control equipment:

If your EGU is ... 3. A co al

- fired, liquid oil

- fired, or solid oil

- derived fuel

fired EGU during startup. You must meet the following ... Once you start firing coal, residual oil, or solid oil derived fuel, you must vent emissions to the main stack(s) and engage all of the applicab le control devices except33 limestone injection in FBC EGUs, dry scrubber, ESP, baghouse. DSI

, SNCR, and SCR You must start your limestone injection in FBC EGUs, dry scrubber, ESP, baghouse. DSI , SNCR, and SCR systems control equipment systems as expeditious ly as possible, but, in any case, when necessary to comply with other standards applicable to the source that require operation of the control devices.

1.1.1.8 Supercritical EGU s

Comment 31: Commenter 20400 states that startup for supercritical EGUs should conclude at least 6 hours after an EGU transitions from subcritical to supercritical operation. Commenter notes that there are approximately 120 EGUs with supercritical steam generators currently operating and they constitute

about 90 GWs of the 330 GWs of coal fired EGU capacity in the U.S. and that these are generally the most modern and most efficient EGUs in the utility fleet. Commenter states that the EPA’s reconsideration proposal and the applicable docket materials still do not properly charac terize the startup process of a supercritical EGU. Commenter states that although all EGUs have startup activities that continue after electricity is first generated, supercritical EGUs also have a very distinct step in the startup process where the EGU tr ansitions from subcritical mode to supercritical operation. Commenter states that the subcritical mode of operation involves the use of a start

- up steam drum or flash tank, specialized valving and other equipment to ensure that steam is of high enough qual ity to prevent moisture droplets from damaging the steam turbine. Commenter states that once the EGU transitions to supercritical mode, that start

- up equipment has been phased out of operation.

Commenter 20400 states that unfortunately the EPA ’ s analysis in EPA

- HQ

- OAR

- 2009

- 0234

- 20224 misses the key technical issues associated with a supercritical EGU . Commenter states that the EPA does understand the importance of having steam quality high enough to prevent damage to turbine blading and other components. C ommenter states that the EPA explains in a footnote that “ We understand that a steam turbine should not be exposed to water droplets at its inlet at any load, to prevent blade erosion and other problems, and that boiler/turbine systems are designed to prev ent this, and we do not consider the proposed definition to be problematic in this regard. ” Commenter states that however this statement is true for both subcritical and supercritical EGU s during all phases of operation.

Commenter states that the distincti on is in how different EGUs accomplish this requirement.

Commenter 20400 states that in a conventional subcritical EGU , mixtures of steam and liquid are returned from the furnace wall tubes and are separated in the steam drum by cyclone separators based o n their different densities. Commenter states that the steam then passes through separators and driers

before it leaves the steam drum. Commenter states that it then passes through primary and secondary super heaters which superheat the steam well above the saturation point at the operating pressure.

Commenter notes that it is important to remember that as steam increases in pressure, the saturation

tempe rature or point at which water droplets can form will increase. A typical subcritical drum EGU operates at about 2,400 psia. At this pressure , t he saturation temperature is about 662 °F

. Commenter

states that because a subcritical EGU has a separating stea m drum followed by super heaters, it is easier to assure that the steam generated is of high enough quality to be used in the turbine.

Commenter 20400 states that by comparison, a supercritical steam generator uses a specialized and dedicated startup syst em to operate like a drum EGU when it first generates electricity until a point34

much later when it begins the transition to supercritical operation. Commenter states that once that transition is completed, the EGU is considered to have completed the major phases of startup.

Commenter states that at that time the EGU is considered to be in “ once through ” operation meaning that there is no equipment in place to separate out moisture droplets from the steam. Commenter states that provided it exceeds the superc ritical conditions of 3,206.2 psia and 705.40 ° F the fluid leaving the steam generator will be free of moisture and no separation equipment is necessary. Commenter states that in normal operation the steam is superheated to 1,000 ° F or higher which provide s additional protection. Commenter notes that the major functions of the startup system were:

• Control water/steam circulation in all sections of the furnace to prevent tubing damage due to overheating;

• Provide a means of cleaning and conditioning the feed water;

• Protect the super heater and turbine from thermal shock during startup;

• Providing a heat recovery system during startup and very low load operation;

• Matching the steam pressure and temperature to the conditions needed by the turbine during warming, startup, and low load operation; and

• Providing a receiver for overpressure steam after a trip, or during excursions.

Commenter 20400 provides a series of single line drawings that show 11 major steps of a startup for one particular supe rcritical EGU design. Commenter states that the EGU referenced has a gross capacity of about 1,400 MW. Commenter notes that i ndividual steam generator manufacturers have different bypass system designs. Commenter states that as can be seen by the drawings, the process is rigorous and each step must be performed in the proper sequence and there are process conditions such as temperature, pressure, fuel flow, and others that must be met before an operator can proceed from one step to the

next. Commenter state s that referring to Attachment 1, the major components of a steam generator start up system include the primary and secondary superheater bypass valves, a high pressure flash tank, a low pressure flash tank, flash tank return valves, and steam dump valves that lead to a heat sink such as an auxiliary condenser. Commenter states that in addition, this steam generator has large division valves and sliding pressure valves between the primary and secondary super heater. Commenter states that these valves are initially closed when a n EGU is started, but are gradually and carefully opened during the transition from subcritical to supercritical operation. Commenter states that initial circulation in the steam generator occurs in steps 1 thr ough 3. Commenter states that steam generated by a smaller startup boiler is used for warming the feed water and the feed pump is started at the beginning of step 4.

Commenter states that the first firing of fuel in the steam generator occurs at the end of step 4.

Commenter states that operation of the turbine generator begins in step 7 and electricity is first produced. Commenter states that in steps 8 and 9, additional subsystems are placed into service as the level of electricity generation increases. Co mmenter states that the transition from subcritical to supercritical operation occurs between steps 10 and 11 and is commonly called “ flow transfer

. ”

Commenter states that once the steam generator completes flow transfer, the startup equipment is phased

ou t of operation.35

Commenter 20400 states that there is a lag of several hours between when the startup system equipment ceases operation and when all emissions control equipment is fully operational under normal conditions and the EGU’s emissions are repres entative of normal operations. Commenter states that for example, once the flue gas reaches minimum operating temperature, it can take hours to properly warm up the large volume of catalyst in an SCR. Commenter states that similarly an FGD system contains a very large mass of lime or limestone slurry. Commenter states that often the higher level of excess air during startup can drive extra O 2 into the slurry and change its chemical nature. Commenter states that operators must be careful to prevent condition s that would cause scaling which in turn could foul components such as mist eliminators. Commenter states that it again takes time to turn over the large volume of slurry and allow the chemistry to reach equilibrium.

Commenter 20400 states that pollution control equipment is also designed to operate most effectively within a specified range. Commenter states that the highly variable operating conditions during startup (in particular, large swings in temperature, flue gas flow rate, and dew point) may preve nt operation of some control systems (SCR or sorbent injection) or affect the performance of systems which are in operation (scrubbers, ESP s, baghouses). Commenter states that operators often must take care not to

“ over feed ” certain systems such as activa ted carbon to prevent it from accumulating and causing fire, pluggage or other risks. Commenter states that all these factors result in higher startup emissions. Commenter recommends that the EPA expand the startup period for supercritical EGU s to conclude 6

hours after a n EGU finishes the flow transfer step and completes the transition from subcritical to supercritical operation.

1.1.1.9 CFB EGU s

Comment 32: Commenter 20403 states that the suggested language does not address the problems

related to coal refuse

- fired CFB (or FBC)’s as it may take upwards of 24

- hours to allow for bed stabilization which is a critical aspect of startup as well as initiating procedures and APCDs to insure emission requirement are being achieved.

Commenter 20403 disagreed with the EPA ’ s assumption that the start

- up requirements are not affected by technology. Commenter states that coal refuse

- fired CFB boilers ( particularly low Btu , high sulfur (on a lb Sulfur/MM Btu basis), high ash coal refuse ) ar e significantly different, than high Btu , low ash, and low sulfur (on a lb Sulfur/MM Btu basis) coal. Commenter states that more coal refuse is needed to meet the same heat input as coal. Commenter also states that, in addition, if the percentage of sulfur is the same, there would be twice as much sulfur delivered to a coal refuse

- fired CFB EGU. Commenter

states that the amount of limestone to control SO 2 emissions would, at a minimum be twice as much for

the coal refuse

- fired CFB EGU than for a coal

- fired CFB EGU and that the total amount of ash being

delivered to the boiler would be 3

- to

- 4 times; the net result would be 4 times more ash being delivered

to the CFB coal refuse

- fired EGU than to a coal

- fired CFB EGU. Commenter states that, as a result of the increase in mass related to the Btu, sulfur, and ash content of the coal refuse and the amount of

limestone needed to control SO 2 emissions, it takes a considerably longer period to produce the load

needed to sustain and stabilize the bed. Commenter states that based on the limited data collected from

coal refuse

- fired CFB, these considerations were not fully considered in the EPA’s Startup TSD. Commenter states that generally, high sulfur coal refuse

- fired CFB boilers without back

- end SO 2 polishing controls can take up to 24 hours to reach stabilized conditions. Commenter notes that these time limits are tied to bringing the load up to a point that the bed is stabilized and can be maintained.36

The load needed to insure bed stabiliza tion is typically greater than 25 percent. Most coal refuse

- fired CFB EGUs generally need a load in excess of 60 percent or higher (in the 70 percent range) and once such an EGU boiler reaches full load, it usually takes additional time for the bed to stab ilize and reach optimal furnace temperatures needed to meet the SO 2 and NO X emission rates. Commenter alleges that if CFB EGUs drop the load below the 60 to 70 percent range, the bed begins to cool below the solid firing permissive temperature causing the bed to slump causing the EGU to malfunction or shut down.

Commenter 20403 notes that with back

- end SO 2 polishing devices (e.g., dry scrubbers or ash reinjection with humidification), the CFB boiler is typically designed for about 80 percent SO 2 removal and the polishing scrubber is designed for about 90 percent SO 2 removal for an overall SO 2 removal rate of 95 percent. Commenter indicates that the use of the polishing scrubbers allows the boiler to stabilize its bed quicker because less limeston e is used in the furnace as less SO 2 removal is required and less limestone

is needed to meet the lower SO 2 removal efficiencies.

Commenter 20403 indicates that it has found the key requirement for the start

- up of a CFB boiler is bed

stabilization. Commen ter notes that a stabilized bed requires, among other things, the proper particle size distribution which allows proper heat transfer rates in the CFB boiler ’ s various heating zones such as the evaporative and/or steam heating zones; once proper heat trans fer rates are obtained, the bed temperatures become optimal which is required for effective limestone utilization in the removal of acid gases and the minimization of NO X emissions. Commenter alleges that this is critical as NO X emissions are highly sensit ive to both temperature and the amount of limestone present in the bed whereas SO 2 removal is highly sensitive to bed temperatures. Commenter maintains that t he majority of the bed material during start

- up comes from the introduction of ash and/or limestone into the furnace where t he limestone tends to fracture into small particles which

, depending on the boiler design

, are not optimal for

heat transfer in the evaporative zone. Hence, according to commenter

, the time it takes to create a stabilized bed and optimal temperature s is much longer in duration

– if too much limestone is added, the bed stabilization process becomes stagnant as the bed contains too many fine particles to achieve sufficient heat transfer, resulting in even longer time duration to stabilize the bed.

Comment 3 3 : Commenter 20403 states that t he coal refuse

- fired CFB ’ s startup period as based on the final approved definition and the proposed revised definition would have startup ending before the facility is running on solid fuel , its bed stabilized, and the environmental controls, including APCD, to address air emissions are brought on line. As a result, commenter alleges that a CFB EGU is in jeopardy for having not met its emission requirements and most likely would have violations.

Commenter 20403 indicates that from the data base EPA used to develop the Startup TSD, there appear

to be two coal refuse

- fired CFB EGUs identified (Marion and W estwood) , both of both which have indicated that it requires approximately 24 hours to bring the EGUs up from cold start safely to being operational with a stabilized bed and the emission control processes and devices operational and functioning. Commenter alleges that the Startup TSD data appears to be looking at emissions and emission compliance, not stable operating conditions. Commenter also alleges that although Westwood seems to be able to achieve certain emissions ( SO 2 and NO X ), the data for Marion i s less conclusive. Commenter notes that the data represents a sequencing of startup fuel and co

- firing of startup fuel and

coal refuse with limestone and/or ash but there is no indication when the co

- firing has ceased.

Commenter believes that the EPA has m ade the quantum leap to correlate emissions stabilization with

bed stabilization in a CFB EGU. Commenter maintains that a n important aspect of the Marion d ata is37

fundamental to its comments and its reconsideration request. Commenter indicates that CFB EG Us (especially those firing higher sulfur coal refuse) are unable to determine an economic and technical control strategy to meet either HCl or the SO 2 surrogate; t o achieve the SO 2 surrogate emission rate of

0.2 lb/MMBtu , the coal refuse

- fired CFB EGUs bu rning high sulfur coal refuse will need to achieve upwards of 98 percent capture in the boiler and a s such, significantly additional limestone and fuel will need to be injected into the CFB EGU and more ash will need to be managed. Therefore, commenter

ass erts , it will take more time to stabilize the bed, have adequate fuel and sorbent injected to control SO 2 which will result in additional time t o bring the other emission control systems/devices online per manufacturer specifications.

Commenter 20415 note s that the EPA seeks comment on its analysis of coal

- fired EGU startup period data, as presented in the Startup TSD referenced in 78 FR 38005. Commenter states that it is unknown to what extent the data incorporates the diverse universe of EGUs, but it app ears waste coal

- fired CFBs in particular are under

- represented. Commenter states that as reflected in the data and considering the potential limitations of the Startup TSD , there are some EGU s that do not complete startup within the

EPA ’ s proposed timeframe. Commenter states that the included data appears to support the EPA ’ s conclusions that for coal

- fired EGUs, different types of EGUs may be able to reach a certain output in some time after start of generation; and they can begin contro lling SO 2 and NOx emissions in some time following the start of electricity generation. Commenter states that thus, many EGU s may be able to use a combination of output and time or the start of generation and time as defining the end of startup.

Commenter states that this type of analysis depends on having adequate representative data available for analysis, which was to some extent the case for EGUs with CEMS. Commenter states that therefore, based on the data and analysis provided by the EPA, the EPA ’ s ap proach using some time following output reaching a percent of design capability or time following electricity generation would provide compliance certainty and could be applicable to a high percentage of EGUs, if the time is adequate. Commenter notes a key issue is the specific values to be used in such an approach.

Commenter 20415 states that the EPA ’ s data indicates that there are specific EGU s that would not be able to meet the conditions proposed by the EPA , for various reasons. Commenter adds, there a re other

EGU s subject to the MATS rule

– coal refuse

- fired CFBs

– whose data does not appear to be included in the EPA’s analysis. Commenter states that coal refuse

- fired CFBs may take 24 hours or longer to start up, based on greater volumes of fuel and lo nger periods needed for bed stabilization than is the case for

conventional fuel

- fired CFBs. Commenter states that manufacturers provide specifications regarding temperatures and timing for these EGU s, fuels, and controls relative to startup and when they are fully

functional. Commenter states that, also, the refractory thickness in coal refuse

- fired CFB EGU is greater

than conventional fuel

- fired CFB EGU s requiring more time to bring up its temperature. Commenter

states that, for example, a coal refuse

- fired CFB cannot typically operate successfully below ~60 percent load or the bed begins to slump and not be stable. Commenter states that therefore, using 25 percent design capability as a baseline for defining startup is not appropriate or valid a s applied to these EGU s. Commenter adds, the total volume of material (coal refuse, limestone and ash) to be introduced into the bed in order to meet emission limits will extend the time to bring the EGU up to stable effective

conditions. Commenter states that if the EPA decides to pursue this approach to defining startup of a baseline load or capacity measure plus a timeframe, and provides no alternative regulatory path for

EGU s such as CFBs, then it must consider appropriate baselines and extended periods for specific designs/fuels. Commenter states that in the context of the pending 40 CFR 63, subpart DDDDD

, rule (Boiler and Process Heater MACT, Boiler MACT) , because there are very diverse designs, fuels and38

operating modes utilized by industrial, commerc ial, and institutional ( ICI ) boilers and process heaters,

the alternative unit

- specific compliance approach becomes more important for ICI boilers and process

heaters.

Commenter 20415 states that in order to accommodate those designs/limitations, a more c omprehensive

unit

- specific approach is necessary as an alternative compliance method for EGUs that cannot meet the proposed EGU capacity/time definition. Commenter states that this is a necessary corollary to the EPA ’ s proposed one size fits all approach w ith no further flexibility and would be equally environmentally protective. Commenter recommends, as it has in the Boiler MACT context, that the EPA revise the startup definition to allow facilities an alternative approach to determine the minimum stable o perating

conditions on a unit

- specific basis and include the minimum stable operating load that defines startup and shutdown and the proper procedures to follow during startup and shutdown in a site

- specific plan.

Commenter states that establishment of the minimum stable operating load on a site

- specific basis is analogous to setting other boiler and control device operating parameter limits on a site

- specific basis.

Commenter states that this alternative would effectively be the only option for EGU s whose startup
characteristics fall outside of the EPA ’ s proposed capacity/time definition of startup.

Commenter 20415 states that the following types of concepts could be used as being indicative of a boiler reaching the end of a startup period:

• Boiler firin g its primary fuel for a period of time adequate to provide stable and non

interrupted fuel flow, stable and controlled air flows, and adequate operating temperatures to allow proper fuel drying and air preheat as applicable.

• Emissions controls in servi ce with operating parameters such as flow rates and temperatures being controlled and stable.

• Boiler supplying steam to a common header system or energy user(s) at normal operating conditions including pressure, temperature, and above minimum operationa l stable output flow rate, as applicable to the EGU

.

Commenter 20415 states that under that alternative approach, boiler owners/operators would establish specific operating conditions and parameters defining startup and shutdown in standard operating

proc edures for each affected EGU so that it is clear when each EGU is in either startup or shutdown

mode. Commenter states that procedures should also be used to guide operations purposely through startup or shutdown periods so that protracted periods in startup or shutdown mode beyond that envisioned in the procedures are avoided. Commenter states that each startup and shutd own should be documented relative to elapsed time and timing of actions prescribed in the procedure so that problems are effectively identified and corrected in a timely manner. Commenter states that sources covered by the rule are highly variable and the amount of time needed for startup and shutdown may be different depending on the specific EGU . Commenter states that the EPA has adopted a source

- specific approach in other programs, such as Part 75 (40 CFR Part 75 Appendix A 6.5.2.1).

Commenter 20415 sta tes that this alternative approach can be drafted so that “ units cannot cycle in and out of startup or shutdown ” and to provide “ clarity regarding which periods of operation are subject to the work practice standards rather than numeric emission limits and the associated requirements. ”39

Commenter states that enough specificity would also address the EPA ’ s concern that startup periods must be subject to standards that are more robust than the general duty clause ; t hese site

- specific parameters would be includ ed in the permit and thereby subject to approval and enforcement.

Commenter 20403 suggests that a requirement that the startup period should end for c oal r efuse

- f ired

EGU s when all emission controls are engaged and the bed is stabilized is the correct app roach to address the issue of when startup ends.

Comment 3 4 : Commenter 5830 states that the EPA did not adequately consider the issues concerning

CFB EGUs burning coal refuse in regard to the definition of startup end. C ommenter states that the EPA should consider startup and shutdown issues for CFB EGUs burning coal refuse separately, as 40 percent of startup events at CFB EGUs showed extended periods (i.e., 10

- 75 hours) of fossil fuel combustion before electricity generation commenc ed. Therefore, commenter maintains that it appears that it is appropriate for the EPA to consider startup and shutdown issues for CFB boilers burning coal refuse separately. Commenter also recommends the start of electricity generation for startup purposes must be due to firing coal/coal refuse.

1.1.1.10 Dry FGD EGU s

Comment 35: Commenter 20423 states that as a general matter it believes the EPA document (EPA

HQ

- OAR

- 2009

- 0234 at p. 14.) describing FGD startup and shutdown operations does not specifically describe a separate class of EGUs that are represented by its EGUs with dry FGDs (Antelope Valley Station Units 1 and 2; Laramie River Station Unit 3) and includes perhaps as many as a dozen other EGUs similarly equipped. Commenter states that dry FGD SO 2 control technology uses recycle fly ash in fabricating reagent slurry. Comme nter states that although this difference does not matter significantly for a hot restart, it dramatically alters the cold startup FGD performance as an adequate amount of slurry with recycle ash is necessary and the flue gas temperature must be brought up for slurry injection to avoid wet ash deposits.

Commenter 20423 states that there is no recycle fly ash available to formulate a slurry mix for several hours after a cold restart. Commenter states that the EPA analysis actually does indicate the impact o f this circumstance in Figure 16 of the Startup TSD. Commenter notes, however, because the analysis does not specifically discuss or distinguish between hot and cold restarts the impact is masked by averaging hot and cold restarts together. Commenter belie ves that the EPA needs to modify its technical document to include this discussion and analyze the hot/cold startup impacts separately and then modify the conclusions and the definition of startup accordingly.

Response to Comments 1

- 3 5 : In the May 3, 2 011

, proposed MATS rule, the EPA proposed to establish numerical standards that apply at all times at EGUs. 76 FR 24976. The EPA received comments stating that a work practice standard should be imposed during startup and shutdown periods

in lieu of numerical standards. In the February 16, 2012

, final rule, the EPA finalized a work practice during periods of “ startup ” and “ shutdown ”, as those terms were defined in th at final rule

. 77 FR 9304. The work practice required the use of clean fuels (e.g.

, na tural gas and distillate oil) during startup and defined the end of startup as the time the EGU generates electricity or thermal energy for sale or for on

site use

. The EPA stated that it saw no technical barriers to burning clean fuels for longer periods if necessary to bring the EGU and associated equipment up to temperatures necessary to engage APCDs.40

77 FR 9304, 9381. EPA also stated its understanding that some EGUs engage all their controls at the time they beg i n generating electricity or thermal energy. But at the same time, the EPA recognized the re may be operational constraints with certain controls (notably dry scrubbers and SCR).

The EPA received petitions for reconsideration of the final startup and shutdown work practice. On November 30, 2 012, the EPA issued a notice requesting comment on the work practice requirement s for startup and shutdown periods and on the definitions of “ startup ” and “ shutdown

. ” The proposed work practice requirements and definitions in the November 30, 2012

, reconsideration proposal were very similar to the startup and shutdown provisions in the February 2012 final MATS rule.

The EPA received numerous comments on the definitions and work practice standards and, based in part on those comments, the EPA develo ped a technical support document (“ Startup TSD”) evaluating all startup and shutdown events a t EGUs based on CEMS information EPA has on SO 2 and NO X from the Acid Rain Program database . T he EP A then made th e Startup TSD publicly available (EPA

- HQ

- OAR

2009

- 0234

- 20378) and reopened the comment period for the November 2012 reconsideration proposal to provide an opportunity for public comment on the Startup TSD and the comments submitted during the first comment period. The EPA’s analysis ( see Startup TSD entitled “Assessment of Startup Period

At Coal

- Fired Electric Generating Units

, ” docket ID EPA

- HQ

- OAR

- 2009

- 0234

- 20378 ) reviewed hourly

SO 2 and NO X emissions from continuous emission monitor system (CEMS) installations from all of the nearly 9,500 distinct startup events at more than 400 coal

- fired EGUs, including CFB boilers, and subcritical and supercritical pulverized coal boilers equipped with SO 2 APCDs (e.g., wet or dry FGD)

and/or NO X APCDs (e.g., SCR). The EPA analyzed hourly SO 2 and NO X emissions primarily because

the data could be used to deter mine when sources engaged the controls for those pollutants and that time frame would provide a reas onable metric of when to end the startup period and require compliance with

the numerical standards

. W e are confident sources will be able to capture and accurately monitor HAP

emissions at th e defined end of startup using continuous emissions monitoring m ethodologies

. 1 In addition, we concluded evaluation of these emissions could provide relevant information because SO 2 emissions may be used as a surrogate for acid gas HAP and because SCR can impact Hg levels and the effectiveness of Hg controls. 2 The goal of the analysis was to identify the approximate time it took, on average, to initiate operation of APCDs to determine an appropriate end to startup for purposes of defining the end of the work practice standard. The goal was not to seek the time it took for APCDs at

1 Sources that demonstrate compliance with quarterly stack testing will not be required to test during the period directly after the end of startup under either alternative included in this final rule, and, for this reason, we do not find commenters concerns with compliance with the 30

- day rolling average well founded for those sources using that compliance demonstration method. For sources using CEMS or CPMS, the EPA is confident that sources will be able to comply with the 30

- day rolling average because

the final MACT standards contain sufficient variability to include startup and shutdown periods and the periods directly thereafter, and because we believe that HAP emissions during those periods, as defined, are likely as low as or lower than HAP emissions d uring other periods, particularly at the best performing sources. We are setting a work practice for startup and shutdown because the agency is not currently capable of capturing and accurately measuring HAP emissions during that period, not because

we bel ieve the numerical standards cannot be achieved during the defined startup and shutdown period.

2 The EPA did not include hourly PM data in this analysis because PM CEM data are not available, but

we ha ve information indicating that EGUs are able to engage PM controls at approximately the same

time as coal or oil is added to the unit.41

all EGUs to become fully operational. The analysis indicated that some EGUs are able to engage all their controls once they begin generation, but that a significant majority of EGUs are not able to engage

all controls at that time. We suggested in the Startup TSD that the end of startup may be at some time after the start of electricity generation (i.e.

, 6 hours after the EGU begins generating power or 3 hours after the EGU reached 25 percent of nameplate capacity, whichever comes first ).

The EPA received additional comments during the extended comment period both in favor of and opposed to the approach suggested in the Startup TSD

. Some comments stat ed that it was not appropriate for the EPA to establish the end of startup based on the average time it takes for all EGUs to startup, but instead that the Agency should identify the EGU s it believes are the best performing units

and establish the final standard based on the average time it takes the best performing EGU s to start up

. Other commenters stated that the EPA erred by considering the average performance of all EGUs and

instead should focus on the EGUs that take the longest time to complete startup. Considering these comments in light of the statute, the EPA finds that its approach in the Startup TSD of looking at all

EGUs was not consistent with Clean Air Act ( CAA ) section 112(h)(1) because that provision requires a work practice standards consistent with the requirements of CAA sections 112(d) or (f). Because the

EPA is establishing CAA section 112 (d) standards for EGUs for the first time, and not residual risk

standards under CAA section 112 (f), it is appropriate to consider the requirements of CAA section

112 (d) when establishing the work practice standards in this rule. That provision provides that the

MACT standards for new EGUs must be no less stringent than the performance of the best performing

similar source and that the standards for existing EGU must b e no less stringent than the average performance of the best performi ng 12 percent of sources in the category for categories with 30 or more sources or the top 5 sources for categories with less than 30 sources. Although we do not believe we

have to use th e exact same approach to setting work practice standards as we do for setting MACT

standards , we maintain that the EPA may reasonably follow that approach in light of the statutory requirement to establish work practice standards consistent with CAA sectio n 112 (d) and the fact that

the Agency has an almost complete data set fo r the relevant metric (i.e.

, information on all startup events

at units that have the relevant NOx and SO 2 controls)

. Thus, we do not believe the approach of looking at the average time it takes all EGUs to engage their controls i s consistent with the statute.

The EPA has revised the final rule to include two alternative definitions of the end of startup

. First, we have determined that it is appropriate to retain the defini tion of the end of startup that was including in

the February 2012 final MATS rule. We have information that some existing sources are able to engage

all control devices (except SCR) at the time they begin generating electricity or thermal energy for any use; therefore, we believe that it is appropriate to retain that definition as a compliance option ( see , e.g. , EPA

- HQ

- OAR

- 2009

- 0234

- 20427)

. We are also providing an alternative definition of the end of startup

based on the revised analysis

, which we have revised in this final action ( see Revised TSD entitled “Assessment of startup period at coal

- fired electric generating units

- Revised” in docket ID EPA

- HQ

OAR

- 2009

- 0234) (“Revised TSD”) . Specifically, the EPA determined that an appropriate metric for identifying the best performing units for purposes of defining the end of startup was to identify those units that are able to most quickly engage their SO 2 and NOx controls after electricity or thermal energy generation begins because we are confident that stack conditions will be sufficiently stable at this time

for HAP emissions to be accurately measured using CEMS

. The EPA revised the analysis in the Startup

TSD to determine the EGUs that are best performers based on that metric and averaged the time it took

those EGUs to engage their controls to determine an appropriate time after generation to end startup. See

Revised TSD

. We concluded that the best performing EGUs are on average abl e to get all of their42

controls on line within less than 4 hours after electricity generation and we rounded the time up to 4

hours. We determined that incorporating additional variability into the average time, besides rounding

up to 4 hours , was not neces sary because we believe the data we have includes all the startup events at

the units evaluated in the Startup TSD and Revised TSD.

Many industry commenters state that the times included in the Startup TSD were not sufficient for all EGUs to end startup and that the EPA is required to establish a work practice standard that accounts for the time it takes all EGUs to complete startup

. Several commenters made specific note of the EGUs they operate that are not able to comply with the time frames discussed in the Startup TSD. We do not agree

with the comments. As discussed above, a valid work practice standard under CAA section 112(h) must be based on the performance of the best performing units in the categ ory . A work practice that would allow all sources to comply with the standard without making any changes to their systems would not be consistent with the statute unless all units in the category were identical, which is not the case here

where the record indicates that some sources are able to use clean fuel to sufficiently warm their units and others are able to engage all their controls when they begin generating electricity

. The definition of

the end of startup for the work practice standard finalized i n this action complies with the statute because it is based on the performance of the best performing units as detailed in the Revised TSD. Concerning the specific EGU s that commenters identified as unable to meet the standards at all time,

some of the EGU s were not identified by EPA as best performing EGU s for purposes of startup so it is expected that those non

- best performing sources will have to take some actions at their facility to comply with the work practice

, whereas others did not provide enough s pecificity to allow for analysis

. Even best performing s ources may be require to make adjustment s to and /or operate their EGUs in a

more efficient and safe manner , as other sources have demonstrated an ability to bring their EGUs, including their APCDs, on line safely within the times provided. Whether that is because they have greater clean fuel capacity, better tuned equipment, more competent staff, a more efficient o r otherwise better design structure, or a combination of factors, will be for the source owners to determine and make necessary changes at the facility to comply with the requirements. We note that our analysis included all types of EGUs (e.g., CFB, sub

- a nd supercritical).

In response to commenters ’ concerns that their APCDs may not be functioning as well during and immediately after startup, we note that, with the exception of PM controls, the final rule does not require sources to operate their controls during startup or immediately following the end of startup. Instead, the rule establishes a work practice standard that applies during startup and requires sources to meet specific

numerical emission limits after the startup period ends. As explained belo w, these emission limits can be met a number of different ways

, for example

, by continuing to maximize clean fuel usage

. T he EPA believes that maximized clean fuel usage throughout the startup period in conjunction with PM controls being engaged and operat ed within 1 hour of primary fuel use will sufficiently offset the HAP emissions during startup after coal , residual oil, or solid oil

- derived fuel is added to the boiler. W e also believe the

continued maximization of clean fuel use after the initiation of coal, residual oil, or solid oil

- derived fuel

use will be sufficient to offset any lack of efficiency in the APCD that commenter s may be concerned

about during the startup period

. In any case, sources will not be required to comply with the numeric

standar ds during the startup period

. As we indicate elsewhere in this response to comments ( RTC ) and in the preamble, the EPA is establishing a work practice standard for these sources because the Agency does not have HAP emissions testing data during startup and shutdown periods and, absent that data , we are unable to establish numerical standards

. W e do not know at this time whether th e best performing EGUs maximizing clean fuels during startup, as defined, are emitting more or less HAP than is required43

under th e regulation for sources in operational periods other than startup or shutdown, but we believe that HAP emission may actually be lower during those periods. In addition, our HAP continuous emissions monitoring methodologies are not certified to accurately measure HAP emissions during the defined startup and shutdown periods. After startup ends, sources that are concerned about compliance because they are unable to address efficiency issues with their controls or other facility specific problems may continue to burn clean fuels with the primary fuels to minimize HAP emissions during those periods

. Further more
, we believe that any additional HAP emissions that may occur after the startup period ends will be offset over the 30

- day averaging period , as we explai ned in the MATS

record

. Sources will need to determine the necessary adjustments to their equipment and/or work practices (e.g., increased clean fuel capacity) to comply with the rule requirements.

Several commenters said that the EPA erred by not evaluat ing cold, warm

, and hot starts separately for purposes of defining startup because the cold start units will take longer to get up to the temperatures necessary to engage controls

. We do not agree with the comments and have not included a separate analysis based on the status of the EGU at startup for the following reasons

. The work practice standard requires EGUs to startup their units on only clean fuels until the EGU begins combusting coal , and startup ends 4 hours after electricity generation. We recogn ize that cold units will have to combust clean fuels alone for a longer period of time in order to get their systems up to the temperature necessary to
ensure that the EGU will be able to complete startup within the defined time

. C ommenter s did not provide much if any information questioning the technical ability of EGUs to warm their systems on clean fuels alone, though the comments do indicate that some EGUs do not currently have sufficient clean fuel capacity to bring their units up to the necessary temp eratures. Those units will likely have to increase their clean fuel capacity or otherwise modify their units to ensure that they can bring their boiler and APCDs up to a temperature that will allow them to comply with the final standards at the end

of star tup , if they believe they are unable to comply with their current system

. 3

In the Startup TSD issued during the reconsideration for startup and shutdown, the EPA suggested defining the end of startup, as 6 hours after the start of electricity generation or 3 hours after a coal

- fired EGU reaches 25 percent of nameplate capacity, whichever occurs first. In other words, 6 hours after the start of generation or 3 hours after reaching electricity generation equal to 25 percent of nameplate capacity, whichever comes first, an EGU would have to start monitoring and reporting its HCl , PM, and Hg emissions for the purpose of calculating whether it is in compliance with the 30

- day average emission limits. This approach was intended to provide sufficient time to init iate the operation of

APCDs , and to provide a reasonable time to ensure that EGUs could reasonably capture and accurately measure HAP emissions with continuous emissions monitoring systems such that a work practice would no longer be warranted

.

3 The EPA is aware that some coal

- fired EGUs subject to MATS have the ability to operate at full capacity on natural gas, and that others have requested 1

- year extensio ns to the compliance date for the purpose of increasing their clean fuel capacity through installation of natural gas pipelines, gas conditioning equipment, and/or new igniters and warm

- up guns. See, e.g. , “Significant Revision of Part

70 Source Operation Permit” for the Weston Plant dated September 23, 2014, in docket ID EPA

- HQ

OAR

- 2009

- 0234 (p. 5: “B02 is capable of operating at full load on natural gas.”) ; EPA

- HQ

- OAR

- 2009

- 0234

- 20438

.44

As stated above, t he EPA received many constructive and detailed comments on th e analysis . Although

commenter s’ opinions varied, the EPA identified three distinct groups of comments. The first group agreed with the EPA’s approach to define a time limit following the start of generation, but many

commenter s suggested that more time was necessary to safely and/or fully engage APCDs. The second

group (noted later in this document) proposed that CAA section 112 requires the EPA to establish standards based on the average of the best performing 12 percent of EGUs, not the average of the fleet. The third group disagreed with the EPA’s approach, stating that many APCDs could not be fully functional within the time limits specified by the EPA, and citing the need for greater flexibility.

In the R evised TSD issued with this final rule , t he EPA developed an analysis of distinct startup events that took place at 414 EGUs during a 2

- year period. The analysis shows the time and operating characteristics required for EGUs to control emissions using APCDs. The analysis was divided into two parts. The first portion analyzed the startup events at all the EGUs with the relevant data

. For the second part, we determ in ed that the EGUs that, on average, were able to engage their APCDs the fastest are the best performing sources for purposes defining the end of startup for this rule, and we looked at the startup events at th ose EGUs. We selected the units that were able to most quickly engage their controls

because we determined that su ch units were likely the most efficient sources and would likely begin controlling their HAP emissions sooner and more effectively than sources that took longer to engage their controls. The data indicate that the sources that are engaging their controls a re significantly reducing their NO X and SO 2 emissions so we are confident that the controls are working at least moderately well by the end of startup. 4 We are also confident that sources will be able to accurately

measure HAP emissions with CEMS at th e end of the startup period

.

The EPA evaluated the information provided by commenter s and considered the different approaches to

defin ing the end of startup. It is important to remember that the hour at which startup ends is the hour at which compliance wit h the numeric limits begins , but sources are not in fact required to operate any specific control other than PM controls at this time as long as the source s are able to comply with the 30

- day rolling average under the operating mode at the time . Therefore, EGUs must collect and report all required emissions and heat input or generation data necessary to demonstrate compliance with the

numerical limits that take effect following the end of startup. These data are used in calculating whether an EGU is in comp liance with the 30

- day average emission limits. The final rule does not mandate that all APCDs be fully operational at the end of startup. A s stated above , the EPA chose to define the end of startup as the time it takes for APCDs to become operational at t he best performing EGUs. The EPA chose this option because it believes it most closely follows the requirements of CAA section 112 (h), which requires work practice standards consistent with CAA sections 112(d) and (f) , and because we are

confident that sou rces will be able to capture and accurately measure HAP emissions at th e end of the startup period

.

The EPA’s analysis of startup events at coal

- fired EGUs indicates that the best performing EGUs can, on average, initiate operation of their SO 2 and NO X APCDs within 4 hours following the start of generation ( see Revised TSD ) , and these are generally the controls that take the longest to engage

. Therefore, the EPA has chosen to include an alternative defin ition of the end of startup as the end of the

4 Instead of using the alternate equivalent SO 2 emission limit, sources have the option of complying with the HCl limit which, based on our information, is easier to remove than SO 2

.45

4 th hour following the start of generation of electricity or useful thermal steam for use for any purpose

. The EPA notes that this definition is broadly applicable to different types of EGUs.

The EPA is also finalizing a revised work practice related to the PM control devices that applies to the EGUs complying with the alternative definition of the end of startup . In the February 2012 final MATS

rule and in the November 2012 reconsideration proposal, the EPA stated that once an EGU starts firing coal, residua l oil, or solid oil

- derived fuel, all of the applicable control devices had to be engaged (with certain listed exceptions). See

, e.g. , 77 FR 9304, 9381. The listed exceptions did not include controls for PM emissions and, thus, the EPA ’s intent was that PM controls would be engaged (i.e., operational) at

the moment electricity is generated, which generally coincides with the time coal

, residual oil , or solid

oil

- derived fuel are fired . W e did not receive comments making us question the ability of most EGUs to engage their PM controls quickly after generation, but there were comments suggesting that there may need to be some flexibility

. For this reason, we are providing a 1

- hour period of time following the initiation of firing of coal, residual oil, or soli d oil

- derived fuel before PM control s (including FGD systems if an EGU is able to effect PM control through this APCD) must be engaged

. Therefore, we are finalizing as part of the alternative work practice that PM control must be engaged within 1 hour of t he

time coal, residual oil, or solid oil

- derived fuel are introduced into the boiler. We have also added requirements to document that PM control is being achieved through the operation of the PM controls.

In response to comment s that EGUs subject to the Acid Rain Program are already required to define the EGU’s ranges of operation and normal load ( see 40 CFR Part 75, Appendix A, section 6.5.2.1 ) and that startup and shutdown for such EGUs under MATS could easily be based on these rang es of operation

,

we considered this provision early on but discarded it. The minimum safe stable load in Part 75 is arbitrarily set by the source to enable the identification of an operational load range for the EGU . Based on this operational range, Part 7 5 requires that certain QA tests (mostly relating to flow) be conducted at several levels within that range. This works very well for these QA tests in Part 75 and we have not changed our position on this provision as it applies to Part 75. However, b e caus e this range is arbitrarily set by sources and not enforceable, we did not think that it would be adequate for defining periods of startup and shutdown under MATS.

The EPA note s that the SCR is not the main control device for Hg, but it will likely facilitate remo val by oxidizing a portion of the Hg

. However, w e analyzed NO X (and NO X controls) because we have data on all startup events

, NO X is measured with CEM S

, and the NO X controls are often the last controls to be engaged , not because of the poten tial to help remove Hg

. NO X control is an indicator of the end of EGU

startup. In addition, b ecause our analysis shows that SCR achieve at least 20 percent NO X reduction at the best performing EGUs by the end of startup , some Hg oxidation will be occurring and this will facilitate subsequent removal in the FGD

. As with SCR, the FGD controls at the best performing EGUs

are reducing the SO 2 emissions by at least 20 percent and also reducing acid gas HAP as well as PM and Hg

. We do not agree that spike concent rations directly after our defined end of startup , to the extent they

may occur, are likely to cause EGUs to violate the MATS limits. As we have indicated elsewhere in the record, we maintain that the standards contain sufficient variability to account for spikes in emissions, particularly when averaged over a 30

- day rolling period

.

The data available to the EPA indicate that, o n average, EGUs begin firing coal at about 10 hours after

the start of fossil fuel combustion. That does not mean they rapidly tr ansition to 100 percent coal and commenters have not indicated that they cannot continue to fire clean fuel for longer periods. Further, on46

average, electricity generation begins at about 8 hours after the start of fossil fuel combustion and, o n

average, FGD

- controlled EGUs’ SO 2 emission rates are 85 percent lower than SO 2 emissions at uncontrolled EGUs at the start of electricity generation. We believe that these data indicate that many sources are able to bring their SO 2 controls online prior to the intr oduction of coal , solid oil

- derived fuel,

or residual oil

.

Finally, t he EPA acknowledges the comments asserting safety issues that must be considered during startup of PM controls (e.g., carbon monoxide (CO) buildup, fabric blinding). We believe that almo st all

EGUs will be able to alter their source through any number of means, including increasing clean fuel capacity and modifying burn er s or fan systems

, and comply with the final work practice requirements; however, we recognize that there may be rare occasions that preclude a viable compliance option. Therefore, we are finalizing a provision that provides that an owner/operator may apply for an EGU

specific case

- by

- case emission standard consistent with 40 CFR 63.6(g). However, the EP A will only

consider such requests for EGUs that can provide evidence of a documented manufacturer

- identified safety issue and can provide proof that the PM control device is adequately designed and sized to meet

the final PM emission limit and that it is not feasible to make changes at the facility to otherwise address

the identified issue . In its request for the case

- by

- case determination, the owner/operator must provide, among other materials, documentation that: (1) the EGU is using clean fuels to the m aximum extent possible to bring the EGU and PM control device up to the temperature necessary to alleviate or prevent the safety issues prior to the combustion of coal or oil in the EGU, (2) the EGU has explicitly followed the manufacturer’s procedures to alleviate or prevent the safety issue, (3) the source provides details of the manufacturer’s statement of concern, and (4) the source provides evidence that the PM control device is adequately designed and sized to meet the final PM emission limit. In addi tion, the source will

have to indicate the other measures it will implement to limit HAP emissions during periods of startup and shutdown to ensure a control level consistent with the final work practice requirements

The final rule allows affected EGUs to use the definition of startup that was in the February 2012 final

MATS rule (i.e., that startup ends when electricity generation begins) for all pollutant emissions. Alternatively, the end of startup may be defined as 4 hours after the hour in which electricity generation begins. Further, 40 CFR 63. 6(g) allows the owner or operator to petition the Administrator for an alternative definition, in cases where, for valid technical and/or safety reasons, additional startup time may be needed.

We address comments related to common stack issues in section 1.2.5 of this document.

With regard to commenter’s not e that a quotation used by the EPA in the Startup TSD that comes from a chapter entitled “Oil and Gas Utilization” bei ng inappropriate as it does not apply to oil

- fired EGUs, the

EPA has deleted use of this reference.

Commenters also noted maintenance activities that required heating the boiler with no intent of producing electricity. As long as these activities are done with clean fuels alone , the EPA believes the EGUs are being compliant with the rule even if there is no intent to startup. In addition , if a failed startup occurs before ge neration plus 4 hours, then the EGU would not have reached the end of startup

when the numeric emissions apply; however, the source would have to restart its EGU on clean fuel

alone

. Our analysis took into consideration startup data from most EGU s, including EGU s that perform hold points.47

The EP A recognizes that to meet the standard some EGUs may need to operate their controls differently from previous practices (e.g., EGU s may need to start more FGD modules tha n they currently use during

EGU startup )

. Not every plant will have the capacity to comply with the work practice without mak ing

some modification to the affected EGU s, and a standard that resulted in sources doing nothing more than current practice would almost certainly not be compliant with the requirements of CAA section 112(h). To comply with this final rule, sources will n eed to have sufficient clean fuel capacity to bring their

EGU s to a temperature sufficient to bring PM controls on line, and this amount of heat has been shown sufficient at other facilities to bring all controls on line before introducing coal , solid oil

- derived fuel, or residual oil. Sources will have to evaluate their system to determine what modifications will be necessary to comply with the final work practice standard.

1.1.1.11 Use of SO 2 /NOx Data

Comment 3 6 : Commenter s 20400 and 20428 state that the EPA ’ s Startup TSD inappropriately uses SO 2 and NOx emissions data and not HAP data to judge when a startup should conclude. Commenter s state that the EPA analyzes NOx and SO 2 emissions of EGUs to support its conclusion that startup should be defined as ending 3 hours after 25 percent power, or 6 hours after initial generation of electricity,

whichever occurs first. Commenter 20400 states that SO 2 is a surrogate for the HAP aci d gas emissions regulated under MATS, however EGUs are not required to use it ; instead they can opt to measure and comply with HCl directly. Commenter s state that NOx emissions are not subject to regulation under the

rule. Commenter s no te that the EPA ’ s an alysis does not plot Hg emissions, and does not explain if/how the NOx emissions that it has chosen to analyze correlate with Hg. Commenter s state that similarly, the EPA does not analyze PM emissions, which serve as a surrogate for the non

- mercury metal e missions regulated by the MATS. Commenter s maintain that the EPA is therefore attempting to draw general conclusions about HAP emissions during startup based on incomplete HAP data.

Commenter 20428 attempted to fill this information gap by analyzing Hg CE MS and PM CEMS data, but with noteworthy constraints. Commenter s 20400 and 20428 state that the practical reality is that because the compliance date for the MATS rule is not until 2015, few sources have Hg CEMS installed that follow the protocols of the M ATS rule. Commenter 20428 notes that the limited Hg CEMS data it reviewed presents a somewhat different picture than the SO 2 and NOx data reviewed by the EPA. Commenter 20428 reviewed emissions information obtained during 10 separate startups of a 500 MW

s ubcritical coal

- fired boiler that has an SCR, cold

- side ESP, and wet FGD. Commenter 20428 alleges that in all but one of these startups, the EGU had elevated Hg levels well after 6 hours after first electricity generation. Commenter 20428 notes that it als o analyzed PM CEMS data during startup and indicates that the challenge with that analysis is that PM CEMS are not correlated during startup and shutdown and, thus, the data they produce are of questionable reliability. Nonetheless, Commenter

20428 maintai ns that the PM data suggest that startups can extend well beyond 6 hours after first electricity generation (which would no longer be “ startup ” under the EPA ’ s suggested 3/6 definition), particularly for EGUs sharing a common stack.

Commenter 20400 states that this failure to consider the emissions of pollutants regulated under the MATS introduces uncertainty into the EPA ’ s analysis and supports providing additional flexibility in defining the end of startup. Commenter 20428 notes that the limited data use d in the EPA ’ s Startup TSD introduce uncertainty into the analysis and support providing additional flexibility in defining the end of48

startup. Commenter s 20400 and 20428 state that based on the SO 2 and NOx data that the EPA does have, it is obvious that t here is certainly variability in NOx and SO 2 emissions during startup.

Commenter s state that the EPA has generated smooth curves to plot out “ average ” performance in its figures, but these curves “ obscure ” the inherent variability in how each EGU starts up . Commenter s no te
that close review of the box

- and

- whisker plots in many of the figures shows the wide variation of the data points. Commenter 20428 maintains that this startup variability is confirmed by comparison of an

individual EGU ’ s emissions during startup events. Commenter 20428 alleges that there is an additional uncertainty in the SO 2 and NOx control information presented in the EPA Startup TSD. Commenter 20428 states that the technical analysis does not explain whether these data compilations inc lude emissions data from facilities where EGUs share a common stack; the inclusion of common stack data for an EGU startup, where other common stack EGUs were already operating, could skew the emissions performance data and indicate earlier emissions contr ol than would be the case had the other EGUs (and their associated control equipment) not been operating. Commenter 20400 states that the EPA’s Startup TSD is flawed because it analyzes SO 2 and NOx performance and asserts that performance of those

emission s is the basis for determining a startup period under MATS.

Commenter 20400 states that Hg emissions cannot be characterized by looking at SO 2 and NOx

emissions. Commenter states that by not specifically analyzing Hg emissions during startup, the EPA ’ s analysis misses another important point. Commenter states that many EGUs will use additional materials to aid in Hg removal. Commenter states that these include sorbent injection systems such as ACI, FGD additives to control Hg re

- emissions, and other ch emical agents to aid in the oxidation of elemental Hg.

Commenter states that although these additives are effective at normal operating conditions, they are not during startup conditions. Commenter states that ACI for example has been well documented to re quire a minimum gas velocity to properly disperse the material into the flue gas. Commenter states that if ACI is required for Hg emissions control, Commenter ’ s position is that it cannot be placed in operation until

the EGU load has reached at least 25 pe rcent of full load. Commenter states that this is necessary among other reasons to prevent fires in the air heaters and ESP hoppers.

Commenter 20400 states that the EPA ’ s analysis has an additional deficiency in that it did not consider the impact of star tup on the output based limits. Commenter states that startups by their very nature result in less efficient operation. Commenter states that the amount of fuel required to generate a unit of electricity during certain phases of a startup may be 25 percent to 40 percent higher than during normal full load operation. Commenter states that a higher fuel consumption rate during startup compounds with a lower HAP removal efficiency to produce an even higher emission rate using the output based limits as compare d to the heat input limits.

Commenter 5833 thinks it inappropriate to choose the performance of NOx controls when determining a startup period for controls of PM and other MATS pollutants

– the SCR controls NO X on larger EGUs and is not put into service u ntil it reaches half of its full load output (in accordance with manufacturer guidelines concerning minimum temperatures) to avoid making wet ammonia deposits downstream in the air heaters and ductwork which would damage the equipment and make it necessary to take a plant off line.

Response to Comment 3 6 : The EPA is establishing a work practice for periods of startup and shutdown

because the Agency does not have data on HAP emissions from those periods. Moreover, accurate HAP data from those periods is unlikely to be available from either emissions testing ( which is designed for49

periods of steady state operation ) or monitoring instrumentation such a s CEMS ( which are designed for measurements occurring during periods other than during startup or shutdown when emissions flow are

stable and consistent ) . Even though the CEMS data may not accurately reflect HAP emissions during periods of startup or shutd own, the data are useful in showing emission trends relative to emission control device operation. 5 As shown in the figures provided by commenters, PM and Hg emissions generally decrease in the hours after initial generation as control devices come online. The work practice requirement to start on clean fuels and maximize the use of those cleans fuels throughout the startup period is designed to minimize HAP emissions during those periods, but sources are not required to comply with the numerical limits dur ing startup and shutdown. 6 Integral in the step of developing the work practice is determining the point at which startup ends and EGUs must comply with the numerical limits. The EPA’s analysis of the time it takes the best performing EGUs to engage their SO 2 and NOx controls provides a reasonable gauge as to when startup ends, because those controls are generally the last to come on line because of the operating requirements (i.e., requiring a higher flue gas temperature, the use of slurry obtained from th e PM APCDs) and we are confident that emissions can be captured and reasonably measured at this time. Sources are not required to comply with the numerical limits during startup and shutdown. For this reason, the EPA does not need HAP emissions data for pu rposes of the work practice standard EPA is finalizing.

The rule has added an alternative definition of startup ( see 40 CFR 63.10042): this new definition (2) includes additional reporting, monitoring, and recordkeeping requirements for those EGUs without PM CEMS or not having LEE status. Should an EGU owner or operator choose to employ this new definition, collection and repo rting of this information will provide additional detail regarding startup conditions; this detail will help establish whether or not additional revisions to startup definition (2)

and /or work practices may be required. Of course, an EGU owner or operator may continue to rely on startup definition (1), which has not changed. Reliance on definition (1) means no additional costs, whereas selection of definition (2) may cause a minimal increase in costs for monitoring, reporting, and recordkeeping. See the add itional requirements in 40 CFR 63.10020(e)(3) and 63.10030(e)(8).

The rule also allows EGU owners or operators who choose to use definition (2) and who have demonstrated concerns about safely engaging and operating PM control(s) within 1 hour of first fi ring of coal, residual oil, or solid oil

- derived fuel, to submit requests for alternative non

- opacity emissions

standard s. Such requests are subject to notice and comment rulemaking per 40 CFR 63. 6(g)(1). Until

5 Commenters did not provide actual data; rather, charts summarizing data from six PM CEMS were provided. The PM CEMS ar e identified by commenter as being certified but no means of checking that claim were provided. Commenter notes that “absolute accuracy” of PM CEMS cannot be attested “because the instruments are not correlated (calibrated) during such periods of operation [startup or shutdown].” Strictly speaking, neither NOx nor SO 2 CEMS are calibrated at the levels found during startup or shutdown; rather, they are calibrated between a range of values expected to be seen during

non

- startup and shutdown periods . What thes e instruments can provide during these periods is an indication or trend of emissions, rather than actual values. Of course, the trends are impacted by use (or

non

- use) of diluent caps, as shown in the graphs provided by the commenter.

6 Sources that demonstrate compliance with either a sorbent trap or CEMS are required to collect data during startup and shutdown, but the data are not used for compliance purposes. The EPA is collecting data during these periods so that it will have startu p and shutdown HAP data when it reviews the rule pursuant to CAA sections 112(d)(6) and (f).50

promulgation in the Federal Register of the f inal alternative non

- opacity emission standard, an EGU

owner or operator shal l comply with definiti on (1) of startup contained in 40 CFR 63.10042. See the

details in 40 CFR 63. 10011(e)(4).

The EPA’s analysis considered the best performing sources at the EGU level, not the sector level. The analysis included common and multi

- stack configurations.

The EGU is responsible for meeting either input

- based or output

- based standards (this is a decision for owner/operator) during periods other than startup and shutdown because we believe HAP emissions can be accurately measures at these times . This includes periods of operation a t lower loads and the standards have been set to account for variability associated with all periods , including startup and

shutdown pe riods and low load periods that may occur as the EGU s are ramping up after the end of

startup

.

See the response to comments 130 and 131 related to the time to engage PM APCDs.

1.1.1.12 Failed Starts

Comment 3 7 : Commenter 20415 states that the rule should also address this possible circumstance: a n EGU reaches 25 percent load and continues startup, then drops below 25 percent load before the end of the startup period. Commenter states that in that situation, the full 3 or 4

- hour time a llowance should recommence, once 25 percent load is again reached, as the EGU would need to recommence each phase of the startup process. Commenter believes clarity on this point in the regulation would provide compliance certainty.

Comment 3 8 : Commenter 20423 states that a startup failure can conclude with shutdown occurring within the proposed allowed startup time, or the startup failure can extend beyond the proposed allowed startup time. Commenter states that, as pointed out in the Startup TSD the EPA submitted in this rulemaking docket and o f which the EPA requests comment, “

... failed starts occur for a variety of safety and operating reasons. ” ( at p. 4. ) Commenter questioned whether a startup failure that concludes within the proposed time for startup might still present compliance issues with respect to this proposal?

Commenter 20423 states that even a series of failed startups can necessitate EGU operation beyond the proposed time for startup to end in the definition. Commenter states that, as the EPA identified on the final paragraph of page 4 of the Startup TSD there are many reasons for combustion to cease prior to the

“ completion of startup ” as suggested by the EPA definitions. Commenter states that it is unclear, both in the technical paper and in the EPA ’ s explanation in the proposed reconsidered rule, whether the EPA intends this cessation of combustion prior to the completion of a startup to “ end ” the startup or merely

“ stay the startup clock ” until the resolution of the “ reason ” for the interruption is satisfied. Commenter asks the EPA to clarify its intent in this situation.

Comment 39: Commenter 20409 states that the definition of “failed start” should be clarified such that a startup ends when EGU combustion ceases. Commenter states that a startup failure can end with a shutdown occurring within the proposed allowed startup time, or a startup failure can extend beyond the proposed allowed startup time. Commenter states that, first, as pointed out in the Startup TSD, “...failed starts occur for a variety of safety and operating reasons.” Commenter states that as it understands the51

proposal , a startup failure that concludes within the proposed time for startup would not present compliance issues with respect to this proposal. Commenter asks whether this supposition is correct. For clarity, Commenter requests the EPA to restate its position t hat a failed start within the proposed startup time period poses no compliance issues for HAP SSM.

Commenter 20409 states that the EPA ’ s Startup TSD recognizes many reasons for combustion to cease prior to the “ completion of startup ” as startup is defined in the proposed HAP SSM definition.

Commenter states that under the proposal the EPA presumably would classify situations where combustion ceases during a startup as a “ failed start, ” whereas many in the industry would define an attempted startup where co mbustion ceases as an “ interruption ” during startup. Commenter states that although it presume s the EPA intends to end startup when combustion ceases and thus a “ failed start ” has occurred, it is not clear from the EPA ’ s Startup TSD or from the HAP SSM proposal whether the EPA intends this cessation of combustion prior to the completion of a startup to “ end ” the startup or merely “ stay the startup clock ” until the resolution of the problem for the interruption is found and

combustion is again started. Commenter states that it is imperative that under the proposal a startup ends when combustion ceases prior to startup completion, resulting in a “ failed start ” where the clock stops and the startup ends.

Commenter 20409 states that as n oted by the EPA, the normal progress of startup activities may involve the cessation of fuel combustion following the initial combustion of ignition or startup fuel. Commenter

reiterate s that many in the industry would call these “ interruptions. ” Commenter states that as a practical

matter “ interruptions ” may include planned or unplanned multiple stop/starts of the combustion process.

Commenter no tes that planned interruptions may include, for example, establishing stable igniter operation and flame safety safeguard systems, proof of boiler and/or turbine interlocks, chemical cleaning operation, initial turbine warming, and turbine shakedown operations including those for safety and insurance purposes. Commenter adds that unplanned interruptions may include, for example, sudden and unexpected flame stability problems; temperature and/or pressure excursions; and unavoidable operational equipment problems with fans, air heaters, and pumps, for which normal stable expected operational ranges have not been achiev ed. Commenter states that unplanned interruptions may also include unexpected tube leaks which may take multiple days to repair.

Commenter 20409 states that its members have experienced planned and unplanned interruptions in startups ranging in duration from a few hours to multiple days. Commenter states that one member

references four occasions within the 2

- year 2011

- 2012 study period of startups used in the EPA ’ s Startup TSD where a major coal

- based EGU startup sequence was interrupted between one and three times before the EGU reached normal operation. Commenter states that the interruptions ranged

between 1 hour and 4 hours; in all but one case, the interrupti on occurring events arose before coal fuel

to the boiler had been established. Commenter states that but in that one case

, coal combustion was initiated and terminated without startup. Commenter states that in a separate prolonged shutdown

situation follow ing a n EGU trip ( and while using natural gas fuel ) , an exhaustive troubleshooting exercise was conducted to isolate an electrical problem on the plant control system; several days were required to rectify the problem once the source was identified. Comment er states that in this occasion coal combustion was not initiated prior to the “ interruption ” but it is quite plausible to envision circumstances where coal combustion could have commenced followed by an interruption, where several days would be required t o correct underlying problems. Commenter states that under these or52

similar circumstances

, it is imperative that when combustion ceases

, the startup ends with a failed start and the startup clock ends rather than being stayed.

Comment 4 0 : Commenter 20409 states that the startup rule should clearly incorporate the “ malfunction

defense ” where unforeseen failures cause startup to exceed the time limit allowed for startup.

Commenter states that although not detailed in the EPA ’ s Startup TSD , t he data supplied show failed starts can and do exceed the time proposed to end startup under unexpected or unavoidable

circumstances. Commenter believes the affirmative malfunction defense contained in 40 CFR 63.10001 is and should be applicable to these e vents to avoid noncompliance penalties. Commenter notes the

definition of “ malfunction ” contained in 40 CFR 63.2 to be used in 40 CFR 63.10001 references “ ...not reasonably preventable failure of...process equipment, or a process to operate in a normal or usua l manner which causes, or has the potential to emission limitations in an applicable standard to be

exceeded. ” Commenter believes the 40 CFR 63.3 malfunction definition in combination with the

affirmative malfunction defense on 40 CFR 63.10001 is available to avoid noncompliance penalties for startup failures that exceed the proposed startup time. Commenter requests that the EPA clarify its position on failed starts that exceed the proposed time period.

Comment 4 1 : Commenter 5831 notes that a startup failure can conclude with shutdown occurring within the proposed allowed startup time, or the startup failure can extend beyond the proposed allowed startup time. Commenter indicates that, as pointed out in the Startup TSD, “ ...failed s tarts occur for a variety of safety and operating reasons. ” Commenter asks if a startup failure that concludes within the proposed time for startup might still present compliance issues with respect to this proposal.

Commenter 5831 notes that even a series of failed startups can necessitate EGU operation beyond the proposed time for startup to end in the definition. Commenter indicates that, as identified in the Startup TSD, there are many reasons for combustion to cease prior to the “ completion of startup ” as suggested by the EPA definitions. Commenter states that it is unclear, both in the technical paper and in the EPA ’ s explanation in the proposed reconsidered rule, whether the EPA intends an end of combustion prior to the complet ion of a startup due to a failed startup to “ end ” the startup or merely “ stay the startup clock ”

until the resolution of the “ reason ” for the interruption is satisfied. C ommenter asks for clarification.

Response to Comments 37

- 4 1 : Under the final rule, a failed startup event restarts the startup clock if the source ceases all combustion before beginning a new startup event. The source would be required to combust only clean fuels to begin the new startup. Units that begin a startup event that fails befor e electricity is generated and coal , residual oil, or solid oil

- derived fuel is added will similarly not be in jeopardy of noncompliance with the standards because the clock will not have started in that situation. Commenter does not specify the conditions but the EPA believes the examples where tube leaks need to be repaired would necessitate cessation of fuel firing and/or generation (i.e., a shutdown) and, thus, not be included within the startup period.

Concerning the comment on the affirmative defense , we note that on April 18, 2014, the U.S. Court of Appeals for the District of Columbia Circuit vacated an affirmative defense provision analogous to the provision included in the final MATS rule for the numerical standards. Natural Res. Def. Council v.

E PA , 749 F.3d 1055 (D.C. Cir. 2014). In light of that decision , the EPA does not believe it can provide

an affirmative defense provision with respect to the startu p and shutdown work practice. The EPA will evaluate any such occurrence on a case

- by

- case basi s.53

1.1.1.13 NSPS

Comment 4 2 : Commenter 5848 states that the November 2012 definition for startup was vague and

need s clarification. C ommenter states that it is not appropriate to end startup when the EGU first begins

to generate any electricity, or when the EGU first makes thermal energy for industrial, commercial, heating, or cooling purposes, whichever is earlier. C ommenter supports the June 2013 definition because

it is consistent with commenter ’ s operating experience with its biom ass

- fired boilers. C ommenter states
that the definition is also consistent with commenter ’ s Title V operating permit definition of the end of boiler startup. C ommenter provides revised language:

Startup means the period in which operation of an EGU is initiated for any purpose. Startup begins with either the first

- ever firing of fuel in an EGU for the purpose of producing electricity or useful thermal energy (such as heat or steam) for industrial, commercial, heating, or cooling purposes or the firing of fuel in an EGU for any purpose after a shutdown event. Startup ends 6 hours after when the EGU starts to generate s electricity that is sold or used for any other purpose (including on site use), or 3 hours

after the EGU achieves 25 percent of nameplate capacity while make s ing useful thermal energy (such as heat or steam) for industrial, commercial, heating, or cooling purposes (16 U.S.C. 796(18)(A) and 18 CFR 292.202(c)), whichever is earlier.

Comm enter 5848 also provides an alternative definition that could apply to all EGUs or, at the EPA ’ s discretion, be limited to biomass

- fired EGUs only:

Startup means the period in which operation of an EGU is initiated for any purpose. Startup begins with eit her the first

- ever firing of fuel in an EGU for the purpose of producing electricity or useful thermal energy (such as heat or steam) for industrial, commercial, heating, or cooling purposes or the firing of fuel in an EGU for any purpose

after a shutdown event. Startup ends when the EGU generates electricity that is sold or used for any other purpose (including on site use), or the EGU makes provides useful thermal energy (such as heat or steam) at the proper pressure, temperature and flow rate

to a common header system or energy user(s) for use as either process steam, or for motive power (steam

- driven equipment), or for industrial, commercial, heating, or cooling purposes (16 U.S.C. 796(18)(A) and 18 CFR 292.202(c)), whichever is earlier.

Response to Comment 4 2 : This comment was submitted to the NSPS docket (EPA

- HQ

- OAR

- 2011

- 0044) but is similar to comments presented above submitted to the NESHAP docket (EPA

- HQ

- OAR

2009

- 0234). Therefore, the responses provided to those comments also apply to this on e. We would note

that a biomass

- fired boiler that does not meet the definitions in 40 CFR 63.10042 would not be subject to 40 CFR Part 63, subpart UUUUU.

1.1.1.14 Definition of Startup

- Other

Comment 4 3 : Commenter 20428 states that the EPA focuses on normal or average startups and fails to capture the unpredictability and variability in how any given EGU starts up. Commenter 20428 states that characterizations of startups as “ normal ” suggests that it is predictable and consistent event, but it is54

not, even on well

- operated and maintained EGU s. Commenter s 20395, 20396, and 20428 state that every startup is unique. Commenter 20428 states that startups for a given EGU can vary based on (1) length of time EGU has been down; (2) testing or other needs for specific equipment during startup; (3) equipment glitches; (4) unexpected ambient conditions; and (5) natural variability of fuel characteristics. Commenter 20428 notes that because EGU startups require thousands of individual yet interrelated

co mponents and dozens of subsystems to be “ set into operation, ” if even one component or subsystem fails to operate as intended, the entire startup process for an EGU can be delayed. Commenter 20428

cites examples of issues that cause startups to exceed the times in the EPA ’ s definition, including: water chemistry hold; turbine differential expansion; turbine crossover soak; and testing of equipment following an outage.

Commenter 20428 states that plant personnel monitor water chemistry closely during startu p and when

out

- of

- limit water chemistry parameters are detected, the boiler will be held at current load/steam flow while water treatment facilities purify process water (i.e., a water chemistry hold) . Commenter states that water sample collection and anal ysis requires approximately 1 hour and 2 to 4 hours if multiple samples and adjustments are made. Commenter states that following boiler chemical cleaning or a long period of shutdown, a water chemistry hold can last 12 hours or longer. Commenter states th at as temperatures and water flows increase during startup, water impurities can plate out on the turbine, degrading EGU performance and efficiency, and corrode boiler tubes, leading to boiler tube failures.

Commenter 20428 states that during startup, op erat ors carefully monitor and control heating of rotational and stationary turbine metal, as different parts of the turbine heat up at different rates; for example

, turbine rotors heat up faster than the shell. Commenter states that if load is increased too quickly, the rotor metal will expand quicker than the stationary shell metal, closing gaps between rotating and stationary components, leading to vibration issues or turbine trip. Commenter no tes that to prevent excessive str ess cause by differential expansion of the metal of different turn parts, the boiler

must often hold at low load (e.g., 5 percent of capacity) for 2 to 3 hours to allow the machine to stretch slowly before the EGU proceeds to next step; this is common for cold start s . Commenter states that a turbine trip requires resetting the process, which could take another 8 hours, prolonging startup (although the turbine may trip in this event, in order to maintain boiler temperature, boiler combustion may not be halte d)

.

Commenter 20428 states that manufacturers require turbine crossover soak on all cold startups, where steam piping from intermediate pressure ( IP ) and low pressure ( LP ) sections of the turbine are allowed to heat to the proper temperature. Commenter st ates that total soak time is usually 3 to 4 hours, and the time required varies based on initial turbine and crossover metal temperature and is dictated by starting and loading charts provided by the manufacturer; for example, holding at 5 percent electric ity generation load until crossover temperature reaches 350 ° F ( it may require 2 to 3 hours to reach 350 ° F) and then

hold for 1 hour. Commenter states that if load is increased too quickly, a fracture in crossover steam piping is likely.

Commenter 20428 stated that when equipment or parts are changed out during a maintenance outage, testing must occur when the EGU brought back online to ensure the equipment is working properly and optimally. Commenter provides as an example when pulverizer coal piping is replaced during an outage period, coal line balancing must be performed. Commenter states that a boiler may have seven or eight pulverizers and each pulverizer may have up to eight coal lines, and each pulverizer must be tested55

separately and each coal lin e must be tested to ensure even distribution of combustion in the boiler ; thus, testing of a single pulverizer can take 6 to 8 hours

. Commenter maintains that before an EGU can be brought to full load following this type of work, each pulverizer must be se parately tested ; some of this testing can be performed prior to bringing the EGU back online, but some testing necessarily must occur with coal flowing through the piping

. Commenter states that startup process and time following electricity generation prio r to 25 percent load can easily require much longer than 6 hours. Commenter provides as another example vibration issues following maintenance work, when replaced/repaired parts interact with existing parts for the first time. Commenter states that if vibr ation is detected, plant personnel must perform diagnostics to determine whether the vibration level is acceptable, and the EGU may be held at low load (less than 25 percent) for as long as 12 hours. Commenter states that if vibration level is unacceptable , special analysis and calculations are required at this reduced state.

Commenter 20428 states that characterization of startups as “ normal ” suggests that any given EGU ’ s startup is a predictable and consistent event

– it is not; even well

- operated and maintained EGUs will often have protracted startups due to the type of situations commenter provides. Commenter provides an attachment with figures of NOx emissions from fo ur EGUs from the CAMD database (for subcritical and supercritical EGUs ) over a number of startup events that demonstrate the variable nature of the startup period, even for a given EGU

.

Response to Comment 4 3 : As stated above, t he EPA maintains that its analysis of the startup p ractices of the top performing EGUs, which included all types of EGUs, and its final definition of “startup” adequately balance commenter s’ concerns with the requirements of CAA section 112 (h)

. The definition of startup accommodate s protracted startups and provides flexibility for dealing with “out

- of

- the

ordinary” startup events. The requirement to maximize the use of clean fuels during the startup period (which may mean burning more clean fuels and for a longer period of time) wil l assist in safely bringing the necessary equipment up to operational temperatures

– while minimizing emissions of HAP. Further, if the boiler and/or turbine generator “trips” during a startup period and the EGU is no longer generating electricity, the sta rtup process and time periods begin anew when the EGU begins generating electricity again. However, if electricity generation began before the “trip,” the shutdown work practices would be applicable. The work practice requirement of engaging and operating the PM APCDs within 1 hour of coal, residual oil, or solid oil

- derived fuel firing remains in effect regardless of whether electricity is generated.

Comment 4 4 : Commenter 20403 states that the EPA Startup TSD did not deal with the differences

between coal and coal refuse or bed stabilization but were instead fixated on emissions. C ommenter also

states that the startup analysis for the EGU s analyzed in the document was premised on its existing permits and not o n requirements that will be imposed under MATS.

Commenter 20403 states that the EPA Startup TSD does not reflect startup under the MATS rule, when additional controls will be implemented in starting up the facility

.

Response to Comment 44 : As noted above , the analysis included in the Revised TSD follows CAA section 112, which requires that the standards be based on the practices of the top performing existing sources for which EPA has emissions information.56

The EPA has chosen to define the end of startup as the end of the 4 th hour following the start of generation of electricity or useful thermal steam. The EPA notes that this definition is broadly applicable to different types of EGUs and EGUs in our analysis currently have control configuration s that will allow them to comply with the final work practice standard.

Comment 4 5: Commenter 20403 suggests wording for the startup definition, using one of two concepts

as follows:

Concept No. 1 “ S tartup means the period in which operation of an EGU is initiated for any purpose. Startup begins with either the first

- ever firing of fuel in an EGU for the purpose of producing electricity or useful thermal energy (such as heat or steam) for industrial, commerc ial, heating, or cooling purposes or the firing of fuel in an EGU for any purpose after a shutdown event. Startup ends when the EGU generates electricity that is sold or used for any other purpose (including on site use), or the EGU makes

useful thermal en ergy (such as heat or steam) for industrial, commercial, heating, or cooling purposes (16 U.S.C. 796(18) (A) and 18 CFR 292.202(c)) as a result of being fired on solid fuel (coal or coal refuse) in a stable operational mode, whichever is later,

- OR

Concept No. 2 “ Startup means the period in which operation of an EGU is initiated for any purpose. Startup begins with either the first

- ever firing of fuel in an EGU for the purpose of producing electricity or useful thermal energy (such as heat or steam) for industrial, commercial, heating, or cooling purposes or the firing of fuel in an EGU for any purpose after a shutdown event. Startup ends 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 (16 U.S.C. 796(18) (A) and 18 CFR 292.202(c)), and the unit is operating in a stable mode burning coal or coal refuse. ”

Commenter believes that by using the concept of a “ Stable Bed, ” a standard would be established which would allow APCD or process controls to start as soon as technically feasible and not “ at all times during startup ” as previous written ; t able 3 also addresses the concern of limes tone injection in coal

fired CFBs allowing that to happen and addresses the need to bring on other APCDs or process controls.

Commenter states that t he m anufacturers have established permissive temperatures when APCD should be started along with other crit eria and that a ll APCD should be able to meet their permissive temperatures in the time allotted under the p roposed “ end of startup ” language related to bed

stabilization.

Comment 4 6 : Commenter 20393 states that it is unclear whether the new definition will only apply to the exclusion of data for purposes of calculating the 30

- day rolling average emissions rates, or whether it will also apply to the work practice standards for operating ESPs and other APCDs. Commenter

suggests that the EPA should expressly confirm that the new definition of startup does in fact also apply to work practice standards so that coal

- fueled EGUs will not be required to operate their APCDs until the end of startup under commenter ’ s suggested new startup definition. Commenter maintains that the57

rationale for the same relief in both cases is that coal

- fueled EGUs will encounter the same technical feasibility and safety concerns regarding their compliance with the work practice standard s and their

calculation of the 30

- day emissions limitations.

Comment 4 7 : Commenter 20407 states that the startup period should be defined to conclude only when the EGU as a whole is in operation. Commenter concurs with many of the comments provided on this reconsideration, in that the startup of an EGU is not complete until fuel is being ignited in the boiler, steam and electricity are being generated, and the operating conditions of the EGU meet the criteria for safe and technically feasible operation of all “ APCDs ” associated with the EGU. Commenter reiterates its original comments to the November 30, 2012, proposed rule, in that the emission standards established by MATS were based on the EGU, including all APCDs, operating in a normal manner.

Commen ter states that until such time that an EGU ’ s operating parameters allow for safe and technically feasible operation of the APCDs, the EGU should be considered in startup mode, as it is not being operated in a manner with which the standards were establish ed.

Commenter 20407 states that as expressed by several commenter s in reconsideration comments , an EGU experiences significant economic losses while in a startup condition, both in actual costs, due to the 15

- 20 percent decline in heat rate, and in the loss of electric sales. Commenter states that this provides the EGU with a significant incentive to complete the startup in the most expeditious manner within the safety and operational boundaries of the specific EGU

.

Comment 48: Commenter 20404 supports the concerns and technical assertions of the EGU industry

commenter s regarding the definition of startup, particularly with regard to when “startup” ends and the technical impracticability for EGUs to comply with the definition as written in the February 16, 2012,

rule.

Comment 49: Commenter 20413 supports the idea of keeping flexibility in the final rule’s startup definition by allowing one or the other definitions.

Response to Comments 45

- 4 9 : The EPA based its definition of t he end of startup on the performance

of the units EPA identified as the top performing 12 percent of EGUs . The top performing group included all types of EGUs, and the final definition of the end of startup adequately balances

commenter s’ concerns with the requirements of CAA section 112 (h)

. The EPA similarly looked to the units we defined as best performers when determining the other requirements applicable during startup

and shutdown.

Comment 50 : Commenter 20425 states that additional flexibility in the startup definition is warranted

due to the fact that the EPA ’ s Startup TSD does not address Hg and PM emissions and NOx emissions (considered in the EPA ’ s analysis) are not regulated by MATS

. Commenter notes that the EPA ’ s assessment is based on an average of hot, warm, and cold startups combined and that there are conditions and challengers that are unique based on the startup conditions (hot, warm, or cold) due in part to the amount of time that systems have been shutdown, maintenance work performed, and the time frame involved to bring systems up to design operating conditions. Commenter notes that, again, additional flexibility in the startup definition is warranted.58

Response to Comment 50: See Response to Comment 36. In addition, as shown in the Revised TSD analysis, the best performing sources with respect to NOx and SO 2 emissions were those whose control devices were operational within 4 hours

. T he EPA also maintains that the best performers are able to engage their PM control devices within on e hour of coal , solid oil

- derived fuel, or residual oil

combustion . The analysis looked at hot, warm, and cold starts individually and found 4 hours after electricity generation to be a common time in which emissions control devices began to be effective f or any type of start. Although NO X is not a HAP, control for NO X can impact Hg levels and, in any case

, the EPA determined it was appropriate to consider NO X controls in its analysis because those controls are often the last to be engage d , not because of their ability to facilitate Hg removal

.

Comment 5 1 : Commenter 5840 asks if in the proposed definition of the end of startup, “ nameplate capacity ” means the capacity included in the EIA 860 report for each individual EGU.

Response to Comment 5 1 : The term “nameplate capacity” is not used in the definition of “startup” contained in the November 30, 2012, proposed rule

. Therefore, the EPA is unclear as to commenter’s

intent and we are unable to respond.

Comment 5 2 : Commenter 5840 asks for clarifica tion on the startup and end of startup definitions when

two boilers (e.g., individual FBCs) that start separately, operate individually

, and have emissions monitoring equipment on their own stack, but share a turbine/generator. C ommenter not es that the

sta rtup of the second boiler while the first is generating electricity will need to be contemplated differently in terms of when numerical limits apply to the second stack; the second boiler has temperature thresholds that must be achieved prior to adding limestone to the fluidized bed and the effective use of the APCD. Commenter indicates that the EPA should clarify that the definitions of startup and end of startup are to be applied to individual boilers in cases where an FBC has two boilers

that can star tup and shutdown independently of each other and have separate stacks.

Response to Comment 52 : The EPA agrees that the definitions of startup and shutdown apply to individual, separate EGUs which can startup and shutdown independently and which have indiv idual, separate stacks, but share a generator or turbine, provided that the EGUs have individual, separate monitoring systems. The EPA notes that for those EGU owners or operators who choose to demonstrate compliance with a generation

- based standard, appro priate means to determine electrical generation for each EGU will need to be provided.

Comment 5 3 : Commenter 20428 states the EPA could exempt startup periods from reporting.

Response to Comment 53 : The rule retains the monitoring, recordkeeping, and reporting requirements associated with startup and shutdown periods , and includes additional requirements . As explained in the preamble to the February 2012 final rule, 7 collection of startup and shutdown data will provide the EPA

with information to more fully analyze the ability and appropriateness of establishing numeric emissions

standards and operating limits during periods of startup or shutdown so the issue can be addressed as part of the ongoing 8

- year review of the rule. Collection of these data as part of the rule will also serve to reduce, if not eliminate, future ICRs on this topic

. Finally, we intend to use the data to evaluate

, to the

7 See 77 FR 9382 (February 16, 2012)

.59

extent possible

, the accuracy of HAP CEMS during periods of startup and shutdown and determine

whether it is fe asible to establish numerical limits at a later time.

Comment 54 : Commenter 20408 states that the ICR data used to develop the MATS rule did not include data collected during a startup or shutdown, and that all testing was performed at normal EGU

loads where all APCDs we re operating normally. Commenter indicates that the EPA, in its assessment of startup periods in EPA

- HQ

- OAR

- 2009

- 0234

- 20378, states “ ...that average and median NO X emission rates for the full range of normal starts at SCR

- equipped supercritical PC EGUs begin to decline around hour 6, indicating that, on average, SCR effectively controls NO X approximately 6 hours or less after the start of generation. ” Commenter believes that t his statement is very misleading and states that, e.g., ( referring to Figure 13) although at hour 6 NO X begins to decrease, it does not reach a stable (and 50 percent lower) level of control until about 20 hours after startup. Commenter indicates that this stable level of control is what was tested as part of the 2010 ICR and the emission rates that the MATs rule

were based on and states that startup should not end until the boiler and air pollution control equipment operating conditions are reach ed as was tested in the 2010 ICR.

Response to Comment 54 : The EPA believes that the analysis of the startup practices of the top performing 12 percent of EGUs, and its final definition of the end of startup adequately balance

commenter s’ concerns with the requirements of CAA section 112 (h)

. The EPA notes that the goal of the analysis was to identify the approximate time it took, on average, to initiate operation of APCDs by the top performing 12 percent of EGUs. The goal was not to seek the time it took fo r APCDs at all EGUs to become fully operational. The EPA believes that EGUs will be able to reasonably capture and accurately

measure HAP emissions at the end of startup because of the expected emissions flow and also be able to comply with the numerical limits as discussed above and in the preamble to the final rule

. In addition, sources that want an additional compliance margin may also continue to co

- fire clean fuels after the end of startup to further minimize HAP e missions. The EPA believes that sources almost always operate with a compliance margin to ensure continuous compliance with numeric standards. The fact that

sources are generally able to operate with a compliance margin is further evidence that EPA ’ s MACT standards are achievable and contain sufficient variability to absorb spikes in HAP emissions that may

occur.

1.1.2 Definition of s hutdown

Summary of Comments Received Following November 30, 2012, Proposal

Comment 5 5 : Commenter 2028 1 notes that although it is in favor of expanding the time defining startups, this is not necessary for shutdown periods.

Response to Comment 55 : The EPA thanks the commenter . Considering the comments received, the EPA did not consider it necessary to change the proposed definition for shutdown periods.

Summary of Comments Received Following June 25, 2013, Reopening of Public Comment Period

Comment 5 6 : Commenter 20404 requests shutdown be defined as the period 12 hours before last electricity generation because when an EGU is brought out of steady state for shutdown, the air60

pollution controls lose effectiveness in a reverse fashion as temperatures and pressures drop requiring the disengagement of control equipment.

Commenter 20408 notes that from an APCD perspective SCRs and ACI systems will be in shutdown mode well before electricity generation ceases and fuel is shut off to the boiler (e.g., for an SCR, the ammonia will be shutoff once the inlet temperature falls below the critical temperature for n ormal operation; for the ACI system, injection will cease once the boiler falls below its minimum stable load to avoid safety issues with the ESP). Commenter notes that in both of these situations, electricity is still being generated and fuel is being sup plied to the boiler. However, the control efficiency for NO X and Hg begins dropping at this time as these control systems are not operating in their normal mode. These conditions were not tested as part of the 2010 ICR so commenter requests that the beginn ing of shutdown be defined as that point in time when the required control devices are not operating in their normal manner as part of a shutdown sequence and that the EPA should not define a bright line for when shutdown begins.

Comment 57 : Commenter 20 403 states concern about the combustion of residuals in the bed once the fuel feed has been stopped. C ommenter states that combustion residuals in the bed will have unburned coal refuse/carbon that will continue to combust even though no fuel is being fire d. Commenter states that a suggested temperature (lower bed temperature < 500 °F) may address this concern. Commenter provides the following suggested text:

Shutdown means the period in which cessation of operation of an EGU is initiated for

any purpose. Shutdown begins when the EGU no longer generates electricity or makes useful thermal energy (such as heat or steam) for industrial, commercial, heating, or cooling purposes or when no coal, liquid oil, syngas, or solid oil

- derived fuel is being fired in the EGU, whichever is earlier. Shutdown ends when the EGU no longer generates electricity or makes useful thermal energy (such as steam or heat) for industrial, commercial, he ating, or cooling purposes, and no fuel is being fired in the EGU.

Commenter 20421 recommends that the definition for shutdown be clarified to “ no...fuel is being fed to

the EGU ” from the current “ no...fuel is being fired in the boiler. ” C ommenter notes tha t although in some EGU technologies, the term “ fired ” is synonymous with the term “ fed, ” EGUs utilizing stoker technology will still have combustion of fuel residuals on the grates for a period of time after the fuel feed has stopped.

Comment 58 : Commenter 20401 states that the proposed definition of “ shutdown ” does not accurately reflect the point at which shutdown begins. Commenter explains that “ shutdown begins at the point where igniters are placed in the boilers for flame stabilization to sup port cessation of the primary fuel

source, ” and recommends that the definition of “ shutdown ” should be revised to reflect the actual time at which shutdown begins.

Comment 59 : Commenter 20413 states that the controlled shutdown process, a shutdown that is not caused by equipment malfunction, for its cyclone boiler is a process of gradually taking all systems, including pollution control equipment, down until the boiler is no longer operating. Commenter states that the coal combustion process begins slowly to be reduced which in

- turn reduces the load MW generated. Commenter states that the required temperatures and/or flow conditions for the pollution61

control equipment cannot be maintained below approximately 7 0 percent of nameplate capacity.

Commenter states that, therefore, pollution control equipment such as the SCR and FGD must be turned

off while coal continues to be combusted. Commenter states that, as per the manufacturer ’ s specifications the combustion o f coal is gradually reduced until the load MW has reached approximately 5 percent of nameplate capacity before the boiler is completely shut off and produces zero emissions.

Response to Comments 56

- 59 : The EPA received a limited number of comments on th e definition of “shutdown.” Based on those comments and its analysis of startup events, the EPA is maintaining the definition of “shutdown” proposed in the November 2012 action and we are continuing the requirement that all APCDs must be operated as long a s coal, residual oil, or solid oil

- derived fuel is being burned in

the EGU , and EGUs must continue to operate the APCDs as long as possible thereafter as feasible, considering technological and safety issues

. We also believe that, similar to startup, the use of clean fuels during shutdown must be maximized to reduce HAP emissions and we have added language to that

effect

. The EPA is also aware of industry practice that involves “buttoning up” the EGU in anticip ation of a startup in the near future. We understand this to involve ceasing fossil fuel firing and closing dampers so that there is no air flow through the system (and, thus, no emissions). However, the equipment is maintained such that as little heat as possible is lost (with no additional fuel being fired during this period) , facilitating a more rapid startup.

1.1.2.1 NSPS

Comment 6 0 : Commenter 5848 agreed that the proposed definition of shutdown is appropriate, but that the beginning of shutdown can begin sooner

– an unplanned shutdown of steam

- using equipment (e.g., a turbogenerator or sugar cane grinding mill) can occur and this event can lead to one or more boilers immediately venting steam and initiating a shutdown sequence; in such cases, a parti cular boiler may no longer be generating electricity or producing useful thermal energy, but the boiler will begin the process of shutting down.

. C ommenter provides revised language:

Shutdown means the period in which cessation of operation of an EGU is i nitiated for any purpose. Shutdown can begin s up to 6 hours prior to when the EGU no longer generates electricity or up to 3 hours prior to when the EGU no longer makes useful thermal energy (such as heat or steam) for industrial, commercial, heating, or c ooling

purposes or when no coal, liquid oil, syngas, or solid oil

- derived fuel is being fired in the EGU, whichever is earlier . Shutdown ends when the EGU no longer generates electricity or makes useful thermal energy (such as steam or heat) for industrial , commercial, heating, or cooling purposes, and no fuel is being fired in the EGU.

Commenter 5848 provides an alternative definition which could apply to all EGUs or be limited to

biomass

- fired EGUs:

Shutdown means the period in which cessation of operation of an EGU is initiated for any purpose. Shutdown begins when the EGU no longer generates electricity or makes useful thermal energy (such as heat or steam) at the proper pressure, temperature and

fl ow rate to a common header system or energy user(s) for use as either process steam, for motive power (steam

- driven equipment), or for industrial, commercial, heating, or cooling purposes or when no coal, liquid oil, syngas, or solid oil

- derived fuel is be ing62

fired in the EGU, whichever is earlier . Shutdown ends when the EGU no longer generates electricity or makes useful thermal energy (such as steam or heat) for industrial, commercial, heating, or cooling purposes, and no fuel is being fired in the EGU.

Response to Comment 60 : This comment was submitted to the NSPS docket (EPA

- HQ

- OAR

- 2011

- 0044) but is similar to comments presented above submitted to the NESHAP docket (EPA

- HQ

- OAR

2009

- 0234). Therefore, the responses provided to those comments also apply to this one. We would note

that a biomass

- fired boiler that does not meet the definitions in 40 CFR 63.10042 would not be subject to 40 CFR Part 63, subpart UUUUU.

1.1.3 Clean f

uel s

Summary of Comments Received Following November 30, 2012, Proposal

Comment 6 1 : Commenter s 20243, 20247, 20269, 20299, and 2030 2 support the EPA ’ s inclusion of synthetic natural gas and propane as clean fuels that may be used during startup and shutdown.

Commenter s 20269, 20279

, and 580 3 support the EPA ’ s plan to expand the clean fuels list.

Commenter 2030 8 agreed with expanding and clarifying the definition of clean fuels used for startup.

Commenter agreed that the source is required to use one of the listed fuels, but not necessarily the

cleanest fuel available.

Comme nter 2025 2 supports the inclusion of propane as a clean fuel.

Commenter 2029 7 support s the EPA ’ s decision to include ultra

- low sulfur diesel ( ULSD ) as a “ clean

fuel ” with negligible emissions that can be used for startup without the need for operation of the ESPs or

FGD.

Response to Comment 6 1 : The EPA is finalizing an expanded list of clean fuels

.

Comment 6 2 : Commenters 20282 and 2029 5 state that should the definition of clean fuels become final as proposed, it is not clear that the use of a distillate oil/biodiesel blend during boiler startup would be allowed, which would pose a serious operational challenge to many EGUs. Commenter s sug gest that the EPA should provide greater flexibility in the “ clean fuels ” definition by adding the language “ and other clean fuels as approved by the permitting authority. ” Commenter s suggest that if the EPA is unwilling to make that change, the EPA should expand the proposed list of “ clean fuels ” to include biodiesel and

other renewable fuels that meet the 40 CFR Part 80, s ubpart M requirements.

Commenter 2029 5 suggests that the EPA also should revise the definition to provide that “ ULSD,

NRLM S

- 15 or equ ivalent fuels ” may be used.

Commenter 578 5 supports the EPA ’ s proposal that ULSD be considered a clean fuel, and states that ULSD is the only other fuel on the island of Guam that can be used for startup of the EGUs subject to

this rule.63

Commenter s 20279, 20304

, and 580 3 state that biodiesel and renewable fuels should be included in the

list of clean fuels.

Commenter 2027 9 notes that two of its facilities are permitted to burn biodiesel in its current Title V permits. Commenter notes that including biodiesel would provide EGUs that have fuel constraints with important operational flexibility. Commenter observes that some EGUs do not have easy access to natural gas, and the proposed change ensures that these plants have additional alte rnative clean fue ls from which to choose (syngas, propane, and ULSD in addition to the currently listed natural gas and distillate oil).

Commenter s 202 8 2 and 580 3 state that the EPA must provide greater flexibility in the “ clean fuels ” definition by adding the language “ and other clean fuels as approved by the permitting authority. ”

Commenter 202 8 2 states that several of its members ’ coal

- fired EGUs fire distillate oil during startup

and for flame stabilization. Commenter learned that some EGUs who also use distillate oil during startup have been informed by their fuel suppliers of their plans to go to a 5

- percent (B

- 5) biodiesel blend

because of the EPA ’ s renewable fuel mandate set forth under 40 CFR Part 80, s ubpart M. Commenter

stat es that once the current distillate oil inventory depletes, these EGUs will have no other choice but to begin to burn a distillate oil/biodiesel blend during startup. Commenter states that it is not clear that the

use of a distillate oil/biodiesel blend du ring boiler startup would be allowed under the proposed rule, which would pose a serious operational challenge should suppliers no longer provide 100 percent
distillate oil.

Comment 6 3 : Commenter 2027 1 believe s the specific listing of ULSD confuses the definition as the definition already includes distillate oil. According to commenter , ULSD is a subset of distillate oil and by default would be included in the definition. Commenter notes that by specifically lis ting ULSD as a clean fuel, it could be interpreted that the EPA is specifically listing the distillate oils that are acceptable clean fuels, making ULSD the only distillate oil acceptable as a clean fuel. Commenter states that it do es not believe that it w as the EPA ’ s intent to limit distillate fuels to only ULSD. To clarify the language,

Commenter suggests that the EPA list all acceptable grades of distillate oils, or remove ULSD from the list of clean fuels in the definition and add language stating “ ...propane, distillate oils (including, but not

limite d to, ULSD)

... ”

Response to Comments 6 2 and 6 3 : The EPA sees no correlation between HAP (including any surrogate) emissions and fuels in the requirements of 40 CFR Part 80, subpart M, as this subpart deals

with renewable fuel standards and greenhouse gas ( GHG ) emissions which are outside the scope of this rulemaking. Thus, the EPA does not believe it appropriate to include renewable fuels subject to the requirements of 40 CFR Part 80, subpart M in the definition of “ clean fuels. ” However, the EPA does see merit, as suggested by some commenter s, of broadening the definition

. After reviewing other rules which use or require clean fuels, we believe that inclusion of those fue ls meeting the requirements of 40 CFR Part 80, subpart I ( “ Subpart I

— Motor Vehicle Diesel Fuel; Nonroad, Locomotive, and Marine Diesel Fuel; and ECA Marine Fuel ” ) is appropriate . Specifically, the definitions and provisions of 40 CFR 80.2, 80.501, 80.510, and 80.520 address sulfur content restrictions relating to distillate, diesel (including ULSD ), and biomass fuels. The EPA believes that requiring cleaner fuel for EGUs will significantly limit or reduce the emissions of regulated air pollutants emitted fr om these sources, further protecting public health and the environment. Information provided to the EPA on another rulemaking64

(found in EPA

- HQ

- OAR

- 2008

- 0708

- 1459) 8 showed that the use of ULSD will significantly reduce emissions of air toxics, including metallic HAP (e.g., nickel, zinc, lead ( Pb ) ). The EPA believes that the other 40 CFR Part 80, subpart I, fuels meeting the subject definitions will also significantly reduce emissions of air toxics and protect public health and the environment during startup events

. The EPA has made the appropriate changes to the definition of “ clean fuel ” in the final rule.

Comment 6 4 : Commenter s 2 0269 and 2027 9 request that the EPA clarify that when switching from higher sulfur distillate to ULSD, EGUs are allowed to use oil already in distillate tanks. Commenter

suggests that the EPA add to the proposed definition of “ clean fuel ” the following language: “ After the

effective date of the rule, all distillate receipts will be ULSD. ” Commenter s state that this revision would make clear that EGUs may use existing fuel supplies.

Response to Comment 6 4 : The EPA does not believe a change or clarification is necessary. The

revised definition of “ clean fuel ” does not require the use of ULSD; all distillate fuel (whi ch includes all

forms of diesel under the 40 CFR 80.2 definition) meet the definition of “ clean fuel

. ”

Comment 6 5 : Commenter 2 027 6 disagreed with the limitation in the clean fuels definition with the fuel options and states that the list should be expanded to include non

- fossil fuel options such as biomass during periods of startup. Commenter said some coal

- fired EGUs implement more traditional methods of startup that consist of burning a combination of biomass (i.e.

, wood chips, wood pallets) and distillate

fuels. Commenter states that these EGUs do not have the capability of burning gaseous or liquid fuels, and would be forced to implement costly retrofits to demonstrate compliance with a work practice

standard. Commenter urged the EPA to provide greater flexibility and clarifications by expanding the

list of “ Clean Fuels ” by recognizing non

- fossil fuels (biomass) that meet the 40 CFR Part 63, s ubpart

DDDDD

, requirements during boiler startups.

Response t o Comment 66 : The EPA does not have information relating to the HAP emissions resulting

from biomass in EGUs subject to the MATS rulemaking and, therefore, as opposed to the use of (e.g.) ULSD noted above, the EPA is not in a position to say that burning such materials would result in sufficiently lower HAP emissions than burning the EGU ’ s normal fuel during periods of startup. T hus

, the EPA has not made this change to the definition of “ clean fuel. ” It appears that commenter also

indicates that distillate fuels are used and the EPA believes that it is this distillate fuel that is the “startup” fuel rather than the biomass (which is simply being used as a substrate) ; as long as these

distillate fuels meet the definition of “ clean fuel ” in the final rule, they would be appropriate for use during startup.

Summary of Comments Received Following June 25, 2013, Reopening of Public Comment Period

Comment 6 7 : Commenter 20397 agreed with expanding and clarifying the definition of clean fuels used for startup

. Commenter agreed that the source is required to use one of the listed fuels, but not necessarily the cleanest fuel avai lable. Commenter supports the revised language in 40 CFR 63.10011.

8 Email and attachments from Paul Miller, NESCAUM, to Melanie King, EPA. NESCAUM’ s RICE

NESHAP comments . October 11, 2012 (EP A

- HQ

- OAR

- 2008

- 0708

- 1459). Also found in docket ID

EPA

- HQ

- OAR

- 2009

- 0234.65

Commenter 20426 agrees with and supports the EPA ’ s proposal to expand and clarify the definition of clean fuels used for startup. Specifically, commenter agrees that the source is required to use one of the listed fuels, but not necessarily the “ cleanest ” fuel available. Commenter states that, having the flexibility to choose from a menu of options gives utilities flexibility to evaluate local economic

con siderations when selecting a startup fuel such as delivery costs, price and availability as the industry plans for MATS compliance activities.

Commenter 20403 supports the expanded list of clean fuels as proposed in the rule for reconsideration

and contin ues to support the change.

Commenter 20389 supports addition of other fuels such as synthetic NG, syngas, propane, and ULSD to the list of clean fuels used during startup.

Response to Comment 6 7 : The final rule authorizes sources to use any of the clean fuels included in the definition during startup and shutdown periods

. Moreover, the final rule clarifies clean fuel monitoring, reporting, and recordkeeping requirements, in conjunction with clarifying startup monitoring, reporting, and recordkeeping requi rements ( see 40 CFR 63.10020(e)(1) and (2)).

Comment 68 : Commenter 20400 states that the EPA ’ s November 2012 proposed revisions to 40 CFR 63.10011(f) appropriately provide greater flexibility for a source to choose among available clean fuels.

Commenter s tates however, in addition to the fuels in the expanded list, biodiesel should be allowed as a fuel for startup and shutdown. Commenter states that biodiesel is a regulated fuel product subject to ASTM specifications for pure product and in various blends with No. 2 distillate fuels. Commenter

states that biodiesel may be blended with fuel, including ULSD, at up to 5 percent blend with no required disclosure to the purchaser.

Commenter 20400 states that the proposed revisions also include a new definition for the term “ clean

fuel ” in 40 CFR 63.10042. Commenter states that biodiesel fuel should also be added to that definition.

Commenter states that in addition, the term “ distillate oil ” in 63.10042 needs to be revised to be

consistent with the fuels allowed under the definition of “ clean fuels. ” Commenter states that as currently defined, distillate oil refers only to heating oil defined as ASTM D396

- 10. Heating oil and diesel fuel are essentially in terchangeable for use in boilers and combustion turbines (CT) , and the product delivered will depend largely on the local fuel market (which in many areas is dominated by the transportation sector and diesel fuel). Commenter recommends that the subpart UUU UU definitions should adopt the same definition as found in 40 CFR 60.41b and 60.41c (which were added to the NSPS rules in the same February 16, 2012

, Federal Register notice that published the subpart UUUUU MATS rule):

Distillate oil means fuel oils th at contain 0.05 weight percent nitrogen or less and comply with the specifications for fuel oil numbers 1 and 2, as defined by the American Society of Testing and Materials in ASTM D396 (incorporated by reference, see § 60.17), diesel

fuel oil numbers 1 an d 2, as defined by the American Society for Testing and Materials in ASTM D975 (incorporated by reference, see § 60.17), kerosene, as defined by the American Society of Testing and Materials in ASTM D3699 (incorporated by reference, see § 60.17), biodiesel as defined by the American Society of Testing and Materials in ASTM D6751 (incorporated by reference, see § 60.17), or biodiesel blends as defined by66

the American Society of Testing and Materials in ASTM D7467 (incorporated by reference, see § 60.17).

Re sponse to Comment 68 : As noted above, the EPA does see merit of broadening the definition to include those fuels meeting the requirements of 40 CFR Part 80, subpart I. Specifically, the definitions and provisions of 40 CFR 80.2, 80.501, 80.510, and 80.520 address sulfur content restrictions re lating to distillate, diesel (including ULSD ), and biomass fuels. The EPA believes that requiring cleaner fuel for EGUs will significantly limit or reduce the emissions of regulated HAP emitted from these sources during startup and shutdown periods , furthe r protecting public health and the environment. We do not believe a further expansion of the available clean fuels is warranted or necessary at this time.

Comment 69 : Commenter 20415 supports defining clean fuels in the MATS rule to include biodiesel and other renewable fuels, as well as the additional clean fuels noted above that EPA has identified in the final subpart DDDDD rule. Commenter states that biodiesel and o ther renewable fuels that meet the EPA renewable fuels standards are by those rules considered equivalent to conventional commercial fuels and similar or preferred in nature to fossil based fuels. Commenter states that to the extent EGUs

utilize those rene wable fuels for SS purposes, the rule should allow their use as “ clean fuels

. ”

Commenter states that in addition, as the EPA is advancing biofuel production through the 40 CFR 80, subpart M

, rules, it is logical that those fuels also be allowed as startup fuels in this rule.

Commenters 20417 and 20419 agree that the clean fuels list should be expanded. Commenter 20417

believes that the list should include other clean fuels, such as biodiesel and other renewable fuels. Commenter 20419 suggests the list sho uld also include biofuels and refinery gas. Commenters state expanding the list of clean fuels will increase regulatory flexibility without major impacts to the

environment.

Commenter 20402 supports the EGU industry commenter s that advocated that the EPA should expand its proposed list of “ clean fuels ” to include biodiesel and other renewable fuels that meet the 40 CFR Part 80, subpart M, requirements

. Commenter states that, at a minimum, the EPA should expand the

definition of “ clean fuels ” in the MATS r ule to mirror that in the final Boiler MACT rule, which

includes “ natural gas, synthetic natural gas, propane, distillate oil, syngas, ultra

- low sulfur diesel, fuel

oil

- soaked rags, kerosene, hydrogen, paper, cardboard, refinery gas, and liquefied petroleu m gas ” and notes that this list is broader than the one included in the MATS rule. However, commenter maintains that this list is still not reflective of all the fuels that are fired during startup, and the EPA should take

another look at how units utilize fuels during startup; many EGU units need to co

- fire “ clean fuels ” with the primary fossil fuel at some point during the startup process in order to make the necessary transition to full operations using the primary fuels.

Commenter 20416 states that the definition of “ Clean Fuels, ” which must be used under the MAT ’ s startup and shutdown work practice standards should be further expanded. Commenter states that the EPA proposed several modifications to finalize the “ clean fuels ” work practice standards inc luding the addition of synthetic natural gas (NG) , syngas, propane
, and ULSD . Commenter states that, however,

the EPA has failed to consider the use of non

- fossil fuel sources such as wood scrap as a “ clean fuel ” in order to further expand its list of “ clean fuels ” within the June 25, 2013

, reopening of the public comment period . Commenter states that, as provided in its comments filed on January 7, 2013, many

older coal

- fired EGUs implement more traditional methods of startup which consists of burning a67

combination of biomass or bio

- based solid fuel (i.e.

, wood chips, wood pallets, scrap wood products)

and distillate fuels.

Commenter 20416 states that the EPA has not provided adequate guidance for those EGU ’ s which incorporate more traditional methods o f startup consisting of burning bio

- based solid fuels (scrap wood products) and distillate fuels. Commenter states that if EGU ’ s are required to startup while burning gaseous or liquid fuels only, EGUs will be forced to implement costly retrofits and poten tially require the establishment of firm natural gas delivery contracts to demonstrate compliance with the work practice standards that applies for only short and limited durations annually.

Commenter 20416 urges the EPA to provide greater flexibility and clarifications by expanding the

definition of “ clean fuels ” by recognizing non

- fossil fuels such as wood products, to be combusted during boiler startups in a manner consistent with the Biomass or bio

- based solid fuel definition found in
40 CFR Part 63, s ubpart DDDDD.

Response to Comment 69 : The EPA does not have information relating to the HAP emissions resulting from biomass or other materials identified in the final 40 CFR Part 63, subpart DDDDD, rule in EGUs subject to the MATS rulemaking and, therefo re, as opposed to the use of (e.g.) ULSD noted above, is not in a position to say that burning such materials would result in sufficiently lower emissions than burning the EGU ’ s normal fuel during periods of startup. Thus, the EPA has not made these changes to

the definition of “ clean fuel. ” Commenters note that distillate oil is used in the “ traditional methods ” of

startup and the EPA believes that it is this distillate fuel th at is the “startup” fuel rather than the biomass (which is simply being used as a substrate); as long as these distillate fuels meet the definition of “ clean

fuel ” in the final rule, they would be appropriate for use during startup.

Comment 7 0 : Commenter 20421 supports the expansion of clean fuels definition to include propane

distillate oil and ULSD because it accounts for the design limitations to certain startup fuels of some

boilers.

Response to Comme nt 7 0 : The EPA is finalizing an expanded list of clean fuels that includes the

identified fuels.

1

. 2 Work Practices

Summary of Comments Received Following November 30, 2012, Proposal

1.2.1 General Support

Comment 7 1 : Commenters 2 0252, 20271, 20281, 20288, 20295, 20302, and 2030 4 support the use of work practice standards during periods of startup and shutdown. Commenter ’ s r easons for its support
included the EPA ’ s lack of data to establish emission limits for startup and shutdown and because it is not feasible to conduct valid tests during startup and shutdown periods.

Response to Comment 7 1 : The se comments require no response

.

Summary of Comments Received Following June 25, 2013, Reopening of Public Comment Period68

Comment 7 2 : Commenter 5834 asks that the bright line test for defining the end of startup also be applied to the work practice standards that apply to coal

- fired EGUs during the startup period.

Comment 7 3 : Commenters 20389, 20401, and 20424 support work practice sta ndards in lieu of numeric standards for startup.

Commenter 20393 generally supports the proposed refinements to the work practices but still has concerns regarding the application of the startup work practice requirement to ESPs installed at coal

fired EGU s for limiting filterable PM emissions. Commenter notes that the use of work practice standards in lieu of numeric emissions limits is justified for several important reasons: (1) emissions during startup and shutdown are not representative of normal op eration because the ESPs and other APCDs are either not operating or operating at low removal efficiency levels because the APCDs are operating far from their design conditions; the MATS limits were calculated based on the EGUs operating full load with all pollution control equipment running at maximum control efficiencies and therefore failed to account for the variation of much higher emissions during startup and shutdown periods; the EPA did not have the necessary data to set numeric standards during sta rtup and shutdown given that it is not feasible to monitoring emissions due to the transient nature of these periods.

Response to Comments 72 and 73 : Commenter’s assertion that the numeric standards only account for emissions during maximum control effici ency fails to acknowledge that the EPA applied a variability

factor to the HAP emissions data when establishing the MACT floors and those floors represent a level that can be achieved at all times, including during low load periods and the defined startup and shutdown periods

. T he EPA also provided additional variability through application of the 30

- day rolling average to further offset any spikes in emissions for sources demonstrating compliance using continuous emissions monitoring systems to account for variability in emissions during non

- peak periods. The EPA had initially proposed to apply the numerical standard during startup and shutdown periods believing that the va riability included when setting the standards was sufficient to address those

emissions , and no commenter has provided any information or data that legitimately call that conclusion into question . The EPA never indicated that it needed to include a work pr actice for startup and shutdown periods because we believed the numerical standards could not be achieved i f the startup and

shutdown emissions were included in the 30

- day average ( the EPA successfully defended all challenges to MATS, including the existin g source MATS limits, in White Stallion Energy Center v. EPA . 748 F.3d 1222 (D.C. Cir. 2014)).

Commenter ’ s concerns about the efficiency of controls directly after startup is not supported in the

record . As explained above, we do not have HAP emissions data from those period s . However, we do

have an analysis of NO X and SO 2 emissions and that analysis shows a quick decline in those emission s immediately after controls are engaged at EGUs. This fact suggests commenters’ concerns are misplaced, and, as we s aid above, sources can combust clean fuels alone without generating electricity for a longer period of time to warm up the system and continue to maximize those clean fuels to offset

any inefficiency that may occur at individual EGUs after the end of start up.

Finally, commenter asserts

, without data

, that HAP emissions are always higher during startup and shutdown periods such that it would not be possible to comply with the 30

- day rolling average if startup and shutdown periods were included . We do not agree with this assertion, particularly for the best69

performing EGUs upon which the standard is based. For those EGU s , we believe it likely that their HAP

emissions are actually lower during those periods

, even before fully complying with the final work

pr actice

. We believe that had the EPA determined not to establish a work practice standard during these periods, sources that were concerned about compliance with the 30

- day rolling average would have employed some of the work practice requirements or made other modifications to the EGU s to ensure compliance with a 30

- day rolling average that included the defined startup and shutdown period s . But

, we continue to note that we do not have HAP data during startup and shutdown periods and the testing methodologies are not currently certified to accurately measure at these times. For these reasons, any

assertions that the February 2012 final MATS standards do not include suffici ent variability to account for HAP emissions during startu p and shutdown are without foundation, and the information we have leads us to conclude that the best performing EGUs would have HAP emissions during startup and shutdown periods that are as low or lower than HAP emissions during periods other than startup and

shutdown such that compliance with the 30

- day rolling average would not be a problem

.

Comment 7 4 : Commenter 20389 states that CEMS are designed to collect and measure pollutants in

very narrow ( flue ) gas concentration ranges under stable operating conditions. Commenter states unsteady conditions during startup interfere with CEMS ability to accurately sample and measure pol lutants, data from CEMS under unsteady conditions are known not to be representative, and CEMS provided out

- of

- range values.

Response to Comment 74 : The EPA believes the commenter ’s concerns are misplaced, because the monitoring information during startup or shutdown periods is to be collected, recorded, and reported, but not used for compliance purposes, so the magnitude of CEMS values during those periods do not affect compliance . However, collection of this monitoring information during these periods ma y provide insights on EGU and CEMS operation and performance, which could lead to additional rulemaking in the future. Without the data, the EPA will remain in a perpetual state of ignorance concerning these and other characteristics during startup or shut down periods. Consistent with the final rule, no numeric standard applies during startup or shutdown periods , as defined . Moreover, as mentioned below, emissions during startup or shutdown periods are expected to be minimized due to the short duration of

t he period, the application of PM emissions controls within 1 hour of primary fuel combustion , and the combustion of clean fuels. Furthermore, as explained below, use of diluent caps and/ or minimum electrical production is expected to mitigate out

- of

- range CEMS values for sources that share a common

stack

.

Comment 7 5 : Commenter 20420 states that the revisions to the APCD operation provisions of the startup and shutdown work practice standards proposed as part of the new source MATS reconsideration

on November 30, 2012

, should be finalized.

Commenters 20390, 20414, and 20430 support the work practice standard during startup and shutdown assuming the SS periods are appropriately defined.

Commenter 20403 supports the proposed revisions to Table 3 of su bpart UUUUU of Part 63. Commenter states that the EPA correctly acknowledged that it takes a sequence of steps that involve achieving certain temperatures, sequencing the introduction of coal refuse and limestone to bring the bed temperature up to level wh ere the bed is stable; and the timing of addressing NOx controls or other APCDs to be engaged.70

Comment 76 : Commenter 20400 believes it is appropriate that the EPA did not establish numerical emission limits during startup and shutdown periods because it l acked the necessary data to do so.

Commenter states that assuming that the EPA expands the definition of a startup, any operations during that period would continue to be subject to the work practice standards.

Response to Comments 75 and 76 : The se comment s require no response.

1.2.2 Not Support Further Changes

Comment 77 : Commenters 20422 , 20427, 204 36 , and 20438 opposed changes to startup.

Commenter 20422 opposed any changes in the startup definition and opposed exempting EGUs from numeric limits at any point after electricity is generated. Commenter did not believe industry or the EPA has established either a legal rationale or factual basi s for these changes. Commenter states any further rollbacks will undermine this regulation, reduce its benefits, and create confusion within the regulated community and state agencies.

Commenter 20427 opposed weakening of the startup work practice standa rds. Commenter states the

EPA should not and cannot lawfully extend the work practice standard to a greater portion of coal

- fired

EGU operations. Commenter states readily available APCDs allow compliance with the standards as

finalized. Commenter states an expanded exemption would diverge from the statutory mandate to provide work practices equivalent to the maximum achievable pollution reductions. Commenter states the fundamental obligation imposed by the CAA’s air toxics provision is to spur the installat ion of state

of

- the

- art APCD technologies.

Commenter 20427 states that startup and shutdown events have historically caused disproportionate and enormous pollution ( noted in a February 2013 memorandum regarding State implementation plans, SIPs). Commenter states that an expanded exemption for startup and shutdown would vitiate much of

the rule ’ s benefit; it would allow older EGU s with outdated APCD to avoid upgrading those controls ( provides a summary showing SSM emissions that range from 11 to 300 tons per year PM, for 2011 from EGUs in Texas). Commenter states that the resulting harm would be concentrated on vulnerable communities working and residing in close proximity to older, less efficient plants.

Commente r 20422 states the EPA has already conceded that uncontrolled emissions of HAP during startup can pose significant risks to human health, and the EPA will have to explain how expanding the startup exemption affects these risks.

Commenter 20427 cites the E PA ’ s data of 9,719 startup events in 2011 and 2012, with 9 to 10 startups per year on average, and a small number of older EGU s experienced over 100 startup events in 2011 and

83 in 2012. Based on the EPA ’ s data, commenter states the current proposed rule would exempt 9 hours

of fossil

- fuel combustion for each start (or 43,736 hours of coal and oil

- fired operation per year) ( 9,719 starts divided by 2, times 9 hours ) , and expanding the definition by another 6 hours would exempt another 27,157 hours ( 9,719 st arts divided by 2, times 6 hours ) . Commenter states pollution would be highest at older, sub

- critical EGU s with large numbers of startup events, and these older EGU s are generally located in urban areas, densely populated by poor and minority populations.71

Commenter 20427 states that as coal

- fired EGU s are forced to load

- following or intermittent use by gas

fired EGU s and renewables, the number of startups for coal

- fired EGU s has increased. Commenter notes
that more than half of the nation ’ s coal

- fired EGU s operated at less than 70 percent capacity factor in 2012, suggesting a move toward intermittent operations and frequent startups ( provides an attachment to

its comment letter, showing capacity/utilization factor for coal

- fired EGU s reporting under the Aci d Rain Program).

Commenter 20427 notes that recent studies indicate that the EPA estimates of Hg health impacts may be underestimated, and underscores the importance of setting stringent standards, including during startup

and shutdown. Commenter cites re cent studies that found some individuals might be more genetically predisposed to negative effects of Hg exposure than others, and notes a study that found approximately 10 percent of the more than 1,000 children studied had mutations in their genes that p ossibly contributed to a steeper decline in IQ from exposure to Hg compared to others without the mutation. In another study, commenter notes that very high concentrations of methyl Hg were found in rice gown in farms contaminated by Hg released from minin g activities, further notes that these studies question the assumption that most methyl Hg exposure (the neurotoxic organic form of Hg that accumulates in food chains) comes from consuming fish. Commenter states the science on interaction between climate

c hange and Hg pollution is evolving; climate change will worsen Hg pollution by increasing inorganic Hg deposition on waters, methyl Hg production, and methyl Hg bioaccumulation in the food chain over

the next few decades.

Commenter 20436 notes that the fi nal rule required that APCD be fully operative before coal combustion begins and that it does not believe any weakening of these requirements is warranted or lawful when the pollution control requirements are the methods used to assure compliance with the standards that must apply continuously. Commenter states that many power plants have already installed fabric filters and alleges that many others will do so soon. Commenter maintains that when properly sized, these filters can effectively control PM as so on as coal combustion begins.

Commenter 20438 states that startup periods are not necessarily brief or infrequent

– as coal

- fired

EGUs have been forced into intermediate

- cycling roles by cheaper natural gas EGUs, coal

- fired EGUs are starting up and shutti ng down with increased frequency and older, less efficient EGUs (typically with older controls, and thus very high startup and shutdown

- related emissions) experience the largest

number of re

- starts. Commenter alleges that, although less rigorous than the n umeric standard in the proposed rule, the work practice standard in the final MATS rule, if it is rigorously enforced, should directly and effectively solve the central concern associated with startup and shutdown: uncontrolled

coal combustion. Commenter m aintains that the EPA is conducting reconsideration proceedings that could drastically weaken the MATS’ work practice standard. Commenter states that there is no reason for such weakening and that the standard is eminently achievable. Commenter alleges tha t the MATS’ work practice would require EGUs that currently do not operate their PM APCDs during periods of startup to update their pollution controls, reducing their PM pollution by as much as 20 percent per year. Commenter further alleges that certain EG Us in Texas currently refuse to operate pollution

- controls, even when generating power; they produce, at times, over 300 MW per hour for several hours before activating PM controls. Commenter maintains that producing this much electricity without any

opera tional PM controls leads to very high pollution levels and that the work practice, if implemented and enforced faithfully, would effectively end that pollution.72

Commenter 20438 states that legally and practically, there are no grounds to weaken the work p ractice standard included in the final MATS and as an administrative matter, the work practice standard could

– if retained

– provide the EPA with a very straightforward means of ending uncontrolled pollution during startup and shutdown. Commenter maintain s that the increasingly tangled state implementation plan provisions governing startup and shutdown demand substantial EPA oversight resources to accomplish their desired effect. Commenter alleges that the work practice should directly achieve the same end

– ensuring that pollution controls are used during routine startup and shutdowns

– for one large source category, by directly requiring such operation.

Response to Comment 77 : The EPA maintains that the alternative definition of startup include d in the final rule is appropriate considering the available information. In the original MATS proposal, the EPA proposed to apply the numerical standards at all times, including periods of startup and shutdown, but we finalized a work practice in response to comments and consistent with our understanding of the EGU startup and shutdown processes at the time. The petitions for reconsideration provided some additional information, though it was not until the first comment period that the EPA obtained informat ion that caused us to conclude that the work practice we finalized may not fully account for the performance variability of the best performing EGUs during periods of startup and shutdown , or fully address the monitoring issues associated with startup and shutdown periods . In addition, the EPA during the initial comment period developed the analysis included in the Startup TSD , and the A gency provided an additional opportunity for comment on the analysis in that TSD

. The EPA subsequently revised the Startup TSD in response to comments and developed the Revised TSD included in the docket for this

final action. Based on all o f this information , the EPA decided to provide an alternative definition for the end of startup that we maintain represents the av erage performance of the best performing 12 percent of EGUs, consistent with CAA sections 112(d) and (h)

.

Some commenter s state that all EGUs can get all of their APCDs on line at the time electricity generation begins, but the data do not support that conclusion. While the record indicates that some sources are able to engage all APCDs at the same time as the start of generation, the record does not support a conclusion that such ability is widespread. Conversely, the record as demonstrated in the

R evis ed TSD does support a conclusion that the best performing EGUs on average engage all APCDs within 4 hours of electricity generation. T he requirements to maximize clean fuel use and to engage the

PM control within 1 hour of combusting coal represent what th e best performing EGUs are doing during startup, consistent with CAA sections 112(h) and (d). In any case, these commenters do not address the

EPA ’s concern with HAP measurement accuracy during the defined startup period.

Commenters also maintain that th e proposed changes to the final work practice undermine the rule for

various reasons and weaken and/or remo ve the benefits of the final rule. It appears that the se

c ommenters are asserting that the work practice in the final rule was sufficiently stringent to ensure that the HAP emissions during startup and shutdown would be at or below the numerical limit applicable during all other periods, but that the proposed rev isions make the work practice less stringent tha n the

numerical limits. But that is not the statutory test for a work practice and there are no HAP data from the periods of startup and shutdown as we have defined them in th is final rule . It is the lack of data and the

fact that the EPA does not currently have HAP measurement methodologies that are certified to monitor emissions during those perio ds that caused the A gency to establish a work practice for startup and shutdown period

.73

Furthermore, based on the information provided to the EPA and our own analysis, the A gency believes

that the final rule establishes a work practice that is consistent with the statute and protective of human

health and the environment. We do not disagree t hat the work practice contained in the February 2012

final MATS rule is likely more stringent than the alternative provided in this final action on

reconsideration , but that fact does not negate the validity of the alternative in light of the facts and the statutory requirements as discussed elsewhere . In addition, we believe that under either alternative the level of HAP emissions during the defined startup period may in fact be less than the HAP emissions during all other periods when the numerical limits apply because of the requirement to maximize the use

of clean fuels for what at times may be an extended period ; prior to this work practice sources would be

able to co

- fire coal , solid oil

- derived fuel, or residual oil with minimal clean fuel almost immediately

after initial fuel combustion absent the work practice , and our ability to accurately monitor emissions during those periods does not exist

. The requirement to continue to maximize clean fuel use throughout the startup period and to engage and operate the PM control within 1 hour of adding coal , residual oil , or solid oil

- derived fuel to the EGU also ensure that HAP emissions will be reduced during startup

. Neither of these requirements would exist if sources were required to comply with the numerical limits during startup and shutdown , though sources may have employed such approaches to ensure compliance with the numerical limits if they applie d during startup and shutdown and the HAP emissions could be accurately measured dur ing those periods . Finally, the work practice is currently practically enforceable during periods of startup and shutdown because it relies on information that can be effectively obtained

and reviewed without HAP emissions data . We question the ability to practically enforce the numerical limits during periods of startup and shutdown given the legitimate concerns with our current ability to effectively capture and accurately measure HAP emissions during the defined startup and shutdown periods.

Comment 78 : Commenter 20436 states that should the EPA propose to relax the standard, then

, at a
minimum

, it should require that EGUs :

• disclose the methods used to calculate and report emissions when APCD are not fully
effective, and to include such emissions when determining compliance with the 30

- day rolling averages. Such disclosure should include a full explanation of any “drop

- out” factors that are alleged to reduce PM emissions during SS, and an estimate as to how much of these particulates are later released to the atmosphere during maintenance or normal operations;

• certify that APCD is designed to accommodate the maximum flow of gas from the boilers it serves, and is suitable for the type of fuel used for combustion; and

• disclose the temperature and flow rate required for full operation of APCD, based on a certification from the designer or vendor of such equipment.

Response to Comment 78 : The EPA has revised the final definition of “startup” for the reasons discussed in this RTC and the preamble to the final rule. Given the additional information the rule now requires for EGUs that choose not to use CEMS for compliance purposes (e.g., hourly flow and temperature data, fuel use, and control device parameter measurements), the EPA finds the specific

disclosures and c ertifications suggested by the commenter to be unnecessary.74

1.2.3 Standard Already Accounts for Variability

Comment 79 : Commenters 20422 and 20427 state the emission limits already account for startup.

Commenter 20422 indicates the emission limits were designed to accommodate emissions during startup periods. Commenter states that emission limits for Hg, non

- mercury metals, and acid gases were established through a four

- step process and notes that the EPA first identified the limits already achieved in p ractice by the best performing EGUs, based on an extensive review of multiple stack tests from

EGU s representing at least 12 percent of the industry. Because stack test results measure performance

over a 3

- to 4

- hour time period, commenter indicates that the EPA then inflated those results

– by more

than a factor of 10 for non

- mercury metals

– to account for any operational variability that might affect

emissions. Commenter states that this adjustment was designed to ensure that the best performers c ould meet these standards on a short term basis (equivalent to the several hours needed to complete a stack test) at least 99 percent of the time. Commenter alleges that the EPA then further relaxed the standard by allowing EGUs to determine compliance bas ed on a 30

- day rolling average, rather than the much shorter time periods used in stack testing and then, finally, EGUs were exempt from these limits during the startup period between boiler ignition and electricity generation or heat transfer, but require d the use of clean fuels (natural gas, distillate, or ULSD ) until startup ended.

Commenter 20422 states the EPA never fully explained why it lengthened the averaging period to 30 days, but the record shows the EPA intended the longer averaging time to add ress any short

- term emission spikes associated with startup or shutdown (citing 76 FR 25044

- 45) . Commenter states the

EPA must explain why a 30

- day rolling average is still needed if EGUs are not required to comply for much longer periods after power is fi rst generated. Commenter states if the EPA decides to extend the startup exemption, there is no real justification for such a long

- term average, especially after the EPA has already determined the best performers can meet limits over a much shorter time pe riod at least 99 percent of the time. Commenter states that because emission limits shrink when exemptions are expanded, the EPA cannot consider one without reopening the other.

Commenter 20422 states industry comments do not establish that emission limit s cannot be met over the

30

- day averaging period. Commenter states that most industry comments provide no data to evaluate the vague concerns cited, and broad statements or expressions of concern with no supporting evidence should not be enough to reopen a standard that the EPA finalized more than 18 months ago. Commenter

states that compliance is based on a 30

- day rolling average, and emission spikes that may occur a few hours after power is generated are averaged out by the lower emissions that occur over long periods of normal operation when APCDs are fully engaged. Commenter states industry comments provide no actual data to show the impact and only state that some plants “ might ” have a problem complying.

Commenter states this is the third opportunity th at the EPA has given industry to document why startup over a few hours makes it impossible to meet the emission limits averaged over 30 days. Commenter

further notes that CEMS data are available (for SO 2 ); one industry expert testified that stack testing is possible during startups as long as flow rates are relatively stable during the test period; data reported to CAMD show that flow rates (and heat rates, a proxy for flow rates) can remain relatively stable for several hours over startup, providing suffi cient opportunity to complete stack tests, and it is unclear why industry comments chose not to conduct emissions testing during startup ( citing to expert testimony provided by industry ). Commenter states the EPA identified specific technologies or work pr actices that could be used to limit emissions until APCDs become fully operational but industry commenters have75

not explained why none of these options are workable to meet the standards. Comment er states neither

the EPA nor industry commenters have provid ed enough data to show that unless startup exemption is widened, it will be impossible to comply with pollutant or surrogate limits.

Commenter 20433 rebutted that the UPLs can only predict the 99 th percentile of the data actually represented by the distribution used to determine those UPLs. Commenter notes that the EPA ’ s ICR database contained no startup emissions data, as testing was conducted at full load as required by the EPA. Thus, commenter al leges that the EPA ’ s UPL analysis does not account for emissions variability during startup events, as during startup events, not all pollution control equipment can be operated in accordance with manufacturer specifications and an owner/operator thus coul d not have certified such

data. Commenter believes that Commenter 20422 ’ s assertion that EGUs can meet the standards “ at least

99% of the time ”

– if startup events are included

– is unsubstantiated.

Commenter 20433 further indicates that industry has subm itted data showing how EGUs would not be

able to meet 30

- day emission limits if startup emissions were included (e.g., Attachments 3 and 4 to

EPA

- HQ

- OAR

- 2009

- 0234

- 17775 contain detailed analysis of several sets of PM CEMS data). Commenter 20433 alleges tha t the PM data from Cross Unit 1 is especially pertinent to the assertion by Commenter 20422, noting that Cross Unit 1 endured a difficult startup in April 2010, and its 30

- day emissions average would have exceeded the 0.030 lb/10 6 Btu PM MATS limit as a re sult.

Commenter 20433 states that it does not dispute that data could be collected using stack tests during startup and shutdown but maintains that the data collected would not be accurate . In the deposition testimony cited by Commenter 20422, it was never said that accurate stack testing was possible during startup, noting that Method 5 (a method used to measure PM emissions) “ [i]s designed to test the steady

state conditions. ” (emphasis a dded). Commenter 20433 notes that, a s explained in the testimony, the key to running an accurate Method 5 test is to have stable flow rates during the performance of the manual

test run and that s table or volumetric flow is not present during the startup o f a n EGU because EGU startup is characterized by rapidly increasing fuel and air flows. Method 5 requires that sampling be performed isokinetically, which means that the sampling rate must be matched to a constant flue gas velocity. Commenter 20433 maintai ns that although Commenter 20422 claims that there are data to

support its assertion that “ flow rates can remain relatively steady, ” Commenter 20422 provide s no such

data for review ; i nstead, Commenter 20422 provide limited heat rate data showing that the heat rate at Duke Energy ’ s Wm. H. Zimmer plant reported a relatively consistent heat rate for a 3

- hour window during one startup event. Commenter 20433 alleges that Commenter 20422 provide s no support for its

assertion that “ [h]eat input can generally be u sed as a proxy for flow rates. ” Commenter 20433 states that although Commenter 20422 cite s one very short time period in its comments, simply looking at the periods immediately before and afterwards shows that the analysis fails completely and maintains th at

e ven if such a general relationship were established, the existence of a general correlation between flow rate and heat input does not mean that the flow rate is stable enough to conduct stack tests whenever heat input is relatively stable (a precisely stable flow rate is the relevant parameter in assuring stack test

accuracy )

.

Commenter 20422 states that a handful of EGUs emit significant PM during (SSM) events whereas most EGUs emit less than 10 ton PM during these events ( provides an attachment to its comment letter, a summary showing SSM emissions that range from 0.0 to 310 tons per year TSP, for 2011 from coal

- and

oil

- fired EGUs in Texas). Commenter states an expanded exemption for startup would allow easier76

compliance for the worst

- performing fa cilities but have no effect on most EGUs in Texas to meet the

limits. Commenter states plants that report large PM emissions during SSM events release only a few pounds of individual HAP such as arsenic (As) and Pb and most plants report no HAP releases du ring

SSM events.

Commenter 20436 states that permits issued in Texas in 2011 for 10 plants (20 EGUs) authorize PM emissions during SSM periods up to 7,616 pounds per hour, far higher than allowable during “normal” operations. Commenter notes that these pe rmits do not restrict the number of SSM events or hours during which these higher limits apply but alleges that if the allowable limits are reached for just 80 hours per year (about 1 percent of operating time), SSM emissions would account for between 15 a nd 66 percent of annual emissions the remainder of the year at these plants (based on 2012 emission inventory data). Commenter maintains that exempting these emission spikes would not only be unlawful but would leave the public exposed to higher levels of the hazardous metal that are associated with PM and would significantly undermine what the EPA has accomplished with the MATS rule.

Commenter 20433 alleges that the data contained in Attachment A to Commenter 20422 ’ s comments do

not advance its assertion that industry would not have difficulty meeting the limits. Commenter 20433 notes that first, the data provided are only for total suspended particulates, which is not a HAP and not used as a surrogate under the MATS rule and moreover, the data are provide d on a ton/year basis, with no information about what the emission rates are for the averaging periods relevant in determining compliance with MATS limits.

Commenter 20422 states industry ’ s request to develop “ plans ” that would be “ reviewed ” by state

agen cies is based on the “ general duty ” provisions of CAA section 112, which the D.C. Circuit has already held is not sufficient rationale for substituting work practice standards for emission limits (cited

Sierra Club v. EPA ). Commenter states many states lack capacity or inclination to “ review ” SS plans and generally accept whatever the regulated industry defines as a “ plan

. ” Commenter states allowing regulated industries to decide when emission limits apply and when they do not invites the fo x to guard the henhouse and does not square with a statute that requires emission limits be met at all times.

Commenter provides an example where a state

- approved PM and Pb emissions at rates 10 times higher than the allowable emissions limits that apply d uring normal operation for up to 900 hours per year. Although one industry commenter proposed startup not end until 4 hours after generation has reached 25 percent capacity, commenter states that the industry commenter has not demonstrated that any extensi on is needed to assure compliance with limits based on 30

- day rolling averages.

Commenter 20427 states that the EPA ’ s reconsideration notice cites, as its impetus, concern that a

limited number of coal

- fired EGUs may not be able to operate their current p ollution controls at low temperatures. Commenter maintains that those claimed temperature constraints do not justify further exemptions from the MATS ’ numeric limits, that the EPA has vastly inflated the standards in the name

of “ variability, ” including

– expressly

– variability resulting from operations at lower loads, and that the EPA has further provided “ additional allowance of variability ” by expanding the averaging period to 30 days.

Commenter 20427 states the standards already allow eas y compliance at all times, including periods of low load following startup, because the EPA inflated the standards to account for variability, including variability resulting from lower loads, and the EPA further provided for variability with an averagin g77

period of 30 days. Commenter notes that the PM standard is generous at 0.03 lb/MMBtu, averaged over

30 boiler

- operating days, and allows 4 to 5 hours with PM emissions at 10 to 100 times that level over any 30

- day period, which is adequate to accommodate a ny startup related concerns ( commenter provides a spreadsheet simulating PM emissions and 30

- day averaging period emission values). Commenter

further notes that both ESPs and baghouses for PM may be operated during startup and shutdown to

lower these value s and that SO 2 rates have only minor variations during startup. Commenter alleges that readily available pollution control methods permit compliance with the MATS ’ numeric limits whenever electricity is being generated (indeed, whenever coal is being burne d at an EGU); industry may be reluctant to invest in those methods, but that provides no grounds to exempt EGUs from compliance. Commenter maintains that the primary purpose of the CAA ’ s air toxics provisions is to compel that investment, and the resulting protection of public health.

Comment 80 : Commenter 20436 states that it does not believe that the EPA will be able to show that EGUs operating above the MATS floor cannot comply with the filterable PM limit of 0.03 lb/MMBtu

based on a 30

- day rolling aver age or that the EPA could make this determination without reviewing and perhaps revising the methodology used to determine the floor. Commenter alleges that, according to the Energy Information Administration, 70 percent of existing power plants have alrea dy installed APCD needed to comply with the MATS limits.

Commenter 20427 states that readily available APCD allow compliance with the numeric limits when electricity is being generated, and when coal is being burned at a n EGU . Commenter states that industry may be reluctant to invest in those APCD methods but this provides no grounds to exempt EGU s from compliance. Commenter states the primary purpose of the air toxic ’ s program is to compel investment, and the resulting protection of public hea lth.

Comment 8 1 : Commenter s 20422 and 20436 state the EPA may not expand the startup definition without reopening the emission limits and averaging periods of the rule. Commenter s state redefining startup definition amounts to a constructive reopening of the numeric emission limits. Commenter s state the numeric limit and averaging period were explicitly crafted, according to the EPA , to reflect variability experienced by the best

- performing plants, including low load and startup operations, and the

EPA can not now exempt those operations without providing more stringent limits that reflect the lesser variability in emissions when those operations are excluded. Commenter s state the data does not illustrate how emission spikes during a few hours of startup aff ect compliance with limits based on 30

- day rolling averages. Commenter 20436 states that the final rule required EGUs to meet the 30

- day limit whenever coal was burned to generate electricity and alleges that the EPA cannot exempt periods of coal

combustio n without reopening the emission limit and the 30

- day averaging period.

Commenter 20436 alleges that reopening the rule through expanding the startup definition may also require re

- evaluating the multi

- EGU averaging option because the emis si on rate for multi

- EGU averaging is calculated by dividing the total mass (pounds per hour) by the total heat input for each

covered EGU within the 30

- day averaging period. Commenter maintains that individual EGUs not covered by this average add up the emis sion rate (e.g., lb/ MMBtu) for each hour and divid e the sum by

the total hours within a 30

- day averaging period to determine compliance. Commenter states that these conflicting methods can yield very different results and may be subject to review if the EP A decides now to reopen the averaging times established under MATS.78

Response to Comments 79

- 81 : We do not agree with the commenters’ position that the existing

source MACT limits are flawed because the EPA finalized a work practice standard for startup and shutdown periods . In addition

, comments on the existing source standards are outside the s cope of this rulemaking because we are not reconsidering those standards

. Furthermore, th e argument raised in these

comments could have been raised in the challenges to the final MATS rule that was recently concluded

in the D.C. Circuit. See White Stallion Energy Center v. EPA

. In addition , as stated in the preamble and

this RTC , we believe that the work practice standard in the final rule may result in HAP emissions that are less than the HAP emissions that may be emitted when the numerical standards apply , but that in any case the emissions will be comparable when averaged over the entire startup period . For th ese reason s
, we maintain that the numerical lim its adequately and appropriately account for variability whether or not the sources are required to include HAP emissions during startup and shutdown periods.

Substantively, commenter s make a number of unproven and unsupported assertions about the amount of emissions during startup. For example, one commenter assumes based on its examples that HAP emissions during startup are always higher than at other periods of time. But at the same time

, the commenter notes that we have no data on HAP emissions during startup and shutdown period s

. The best performing sources in the category most likely have HAP emissions that are lower during the startup period as we have defined it because they are using clean fuels up to the time that they add coal to the

boiler and they turn on their APCDs at the same time. Due to the inherently low HAP content of clean fuels like distillate oil and natural gas, it is likely that those best performing sources are emitting below the existing source standards in the final rule during t hat period. Furthermore, the record indicates that even before MATS virtually all EGUs were start ing using clean fuels. Even with the additional 4 hours after generation necessary to ensure the sources’ ability to accurately measure HAP emissions

, we belie ve that the continued clean fuel use during th at 4 hour period will offset any HAP emissions from

the coal

- or solid

- oil derived fuel, particularly if averaged over the entire startup period which will in many cases have longer periods of time where only c lean fuels are combusted. So the record is not clear that HAP emissions during startup and shutdown periods at the best performing EGUs are actually higher than during normal operations. The EPA is requiring sources that measure HAP emissions with

sorbent traps and/or CEMS to measure emissions during startup and shutdown periods so that we can obtain some data on HAP emissions during those periods , even if th ose data may have some uncertainty

and the data are not used for compliance determination purposes. 9 As the EPA stated in the proposed rule, we hope to have sufficient HAP emissions data for the CAA sections 112(d)(6) and (f) reviews to
determine whether numerical standards are feasible and appropriate for periods of startup and shutdown.

Compliance is assured through the provisions of 40 CFR 63.10032(f) (records of the occurrence and duration of each startup or shutdown), 40 CFR 63.10032(i) (records of the type(s) and amount(s) of fuel used during each startup or shutdown), and 40 CFR 63.10020(b) (opera te and collect data at all times the EGU is operating).

Concerning comments that HAP emissions can be measured during startup periods, the EPA is unaware of HAP measurement methodologies that c an be used to accurately measure HAP emissions during those periods at EGUs (even sorbent traps may be problematic due to emissions flow during startup and

shutdown )

. The commenter is correct that there have been HAP testing studies that addressed emission

9 CEMS are certified at low, medium, and high load levels, but not during periods of startup or

shutdown as defined in the final rule.79

f low and other issues associated with testing during startup periods, but the testing issues are not

resolved for broad application and the costs of the tests are significantly more expensive tha n the already expensive certified HAP testing required in the rule methodologies.

The EPA also disagrees with the notion that EGUs will not have to do anything to comply with the final work practice requirements. Sources that do not have sufficient clean fuel capacity will have to increase that capacity. Sources wi ll have to utilize the clean fuel for a longer period of time and to a greater degree. Finally, sources may determine that additional physical changes may be necessary to ensure that sources will be able to engage and operate their controls within the time necessary to comply with the numerical standards at the end of startup

.

1.2.4 L egal i ssues

Summary of Comments Received Following June 25, 2013, Reopening of Public Comment Period

Comment 8 2 : Commenter 20427 states that the startup exemption is based on industry ’ s desire that every EGU, even those of older design, be able to achieve the work practice standard without any investment in improved pollution control. Commenter states that the statute does not allow the E PA to set a standard of universal, low

- cost achievability for the statutory requirement of controls reflecting the maximum reduction achievable (cited Sierra Club v. EPA , 2007).

Commenter 20422 states CAA s ection 112 is designed to reduce HAP emissions us ing APCDs that are based on best available technology. Commenter states MACT is intended to advance facility operations to keep pace with technological advancements in APCDs. Commenter states unless industry can demonstrate that plants that comprise the floor will not be able to meet the limit, which industry has not done, it is irrelevant whether other EGU s are unable to meet the limit. Commenter states industry commenters have not presented any data to show that any plant in the floor will be unable to meet 30

- day emission limits, because of startup emissions or for any other reason.

Commenter 20422 states the EPA must reconcile any expansion of startup exemption with the D.C. Circuit ruling that HAP emission limits under CAA section 112 must apply at all times (cited Sierra

Club v. EPA , 2008). Commenter states that the EPA ’ s proposal to exempt post

- generation emissions from compliance with CAA section 112 emission limits violates this clear requirement. Commenter

states that neither industry nor the EPA have explained how this requirement can be satisfied by expanding the exemptions during startup already in the final rule. Commenter notes that the EPA cited a

40

- year old case, Portland Cemen t v. Ruckelshaus , 1973) that predates the Sierra Club 2008 decision and relies on language in a different section of the CAA that is not identical to the CAA section 112 mandate that emission limits apply continuously. Commenter further notes that the EPA found that the emission standard could accommodate any variability in emissions that might occur after dispatch of electricity. Commenter states industry comments cited in the June 2013 notice do not reference the

Sierra Club 2008 decision and do not explain how the EPA might expand the startup exemption consistent with that opinion and the EPA ’ s duty to establish and enforce CAA section 112 standards on

a continuous basis. Commenter states it did not challenge the startup exe mption in the final rule because it was narrowly tailored, limited to a few hours of combustion, and required use of clean fuels.

Commenter states it reserve s the right to seek judicial review of any decision to lengthen the startup period during which emi ssion limits would not apply or authorize use of coal prior to the generation of80

electricity, which would result in emissions well abo ve the standards that apply during so

- called normal operations. Commenter states that in any case, the EPA will need to ex plain how such a decision is

consistent with Sierra Club v. EPA , 2008. Commenter 20436 states a similar position.

Commenter 20427 states the work practice standards exempting EGU s from compliance with numeric standards during coal

- fired operations are unl awful. Commenter states the EPA has not found, and could not lawfully find, that a numeric emissions standard is infeasible during startup. Commenter states that CAA section 112(h) allows the EPA to substitute a work practice standard for a numeric emissio ns standard only where it is not feasible to prescribe or enforce an emission standard, i.e., a HAP cannot be emitted through a conveyance designed and constructed to emit or capture the pollutant, or if the conveyance would be consistent with Federal, Sta te, or local law, or the application of measurement methodology is not practicable due to technological or economic limitations. Commenter states APCD methods are readily available to capture each pollutant and there are technically and economically

feasib le measurement methodologies available to measure those pollutants. Commenter states the EPA cannot justify an expanded exemption from the numeric limits under that legal standard and cannot justify any exemption from numeric limits during coal

- and oil

- fired operations. Commenter states the

EPA has not made a determination that the measurement o r capture of Hg, PM, or acid gases from coal

and oil

- fired plants is not feasible. Commenter states that if the EPA were to make that determination, it would be obligated under CAA section 112(h) to specify a “ particular class of sources ” to which the

det ermination applied; an overbroad work practice standard, applying to classes for which the EPA has

not made a well

- supported determination of infeasibility under CAA section 112(h), would be unlawful.

Commenter states the EPA ’ s rationale to support its wor k practice standard, i.e., that there is not sufficient data on emissions during startup and shutdown, has no bearing upon that governing legal standard (i.e., the feasibility of capture and measurement of emissions). In fact, commenter states that

the rec onsideration record (an hour

- by

- hour analysis of startup events using emissions, heat input, and electric output data) directly contradicts the proffered rationale, in that the reconsideration is premised upon the data whose absence provide the rationale f or the EPA ’ s original refusal to impose numeric

standards.

Commenter 20422 states the EPA has not proposed new work practice standards in lieu of emission

limits

, has no evidence to support such a proposal. Commenter states CAA section 112(h) allows the

E PA to substitute a work practice standard for a numeric emissions standard only where it is not feasible to prescribe or enforce an emission standard. Commenter states the EPA ’ s June 2013 notice does not propose or justify such an action, identify any spec ific work practices it may substitute for emission limits, or give the public an opportunity to review and comment on a specific proposal. Commenter

states the EPA needs to explain how the specific work practice standards satisfy the requirements of

CAA se ction 112(h). Commenter alleges that the EPA may not base any work practice proposal on a scattering of self

- serving and incomplete anecdotes offered by industry commenters 20 months after the final rule was promulgated. As an example, commenter states that although industry raises concerns about access to clean fuels during startup, the EPA must determine whether more than 12 percent of

coal

- burning EGUs already have the needed capacity and if so, that defines the MACT floor and other

facilities must in vest in upgrades that increase their use of clean fuels (also noting that the EPA has not demonstrated that partial operation of pollution controls for a few hours after electricity is generated makes compliance with emission standards “ not infeasible ” wit hin the meaning of CAA section 112(h))

.81

Commenter 20427 states the work practice standards under consideration violate CAA section 112(d).

Commenters 20422 and 20427 state that CAA section 112(h) requires any work practice that substitutes

for an emission standard under CAA section 112(d) to be consistent with the provisions of subsection (d), i.e., work practice standards must obtain the “ maximum degree of reduction in emissions ” that is

“ achievable ”

. ” Commenters 20422 and 20427 state the “ maximum degree of reduction ” for new sources and the standards for existing sources cannot be “ less stringent than the emissions control that is achieved in practice by the best controlled similar source ” and cannot be less stringent than “ the average

emission limitation achieved by the best performing 12 percent of the existing sources, ” respectively.

Commenter 20427 states the work practice standards under consideration do not meet those requirements. Commenter states the EPA has made no effort to square its work practices for startup with any of the governing legal standards. Commenter states the record suggests only that handful of older

EGU s would need to improve their APCD in order to meet the standards in the final rule; most existing

EGU s and any new EGU using readily available ACPD technologies can operation PM, Hg, and acid gas APCDs at all times coal is burned; and coal

- fired EGU s can meet the numeric limits whenever they generate electricity. Commenter states the EPA has not and cannot demonstrate that any of the work practice standards it has proposed or considered during the rulemaking (except for clean fuels requirement) reflect the maximum achievable reduction in toxic emissions. Commenter states industry

comments ask for a work practice that can be met by all EGU s, with no improvement in the APCD equipment installed in EGU s of older design, but further states the D.C. circuit has firmly established the

EPA may not set its MACT standards “ at the worst emission leve l experienced by any source using the

MACT control ” (cited Cement Kiln Recycling Coalition v. EPA , D.C. Cir. 2001). Commenter states the

EPA cannot set its standard to reflect the emissions experienced by sources that lack state

- of

- the

- art
controls.

Comme nter 20422 states the rulemaking record and industry comments does not provide any basis for substituting work practice standards for the emission limits that apply after boiler s begin generating electricity.

Response to Comment 82 : T he commenter asserts that the final work practice standard is set at a level that all sources can meet, but that assertion is not supported by the information in the docket, most significantly the Revised TSD. As discussed above, the requirement to maximize the use of clean fuels during startup and to engage the PM controls within one hour will result in HAP emissions that are likely comparable to if not below the final standards due to the inherently low levels of HAP emission s attendant to the use of clean fuels. Any source that is not currently equipped with clean fuel capacity sufficient to bring the PM controls up to temperature will have to invest in additional clean fuel capacity.

T he commenter also incorrectly asserts that CAA section 112 standards must involve APCDs. That is not correct, and, in any case, commenter has not identified any APCD that would operate during startup much less one that would have HAP emissions lower than achieved through the use of clean fuels.

T he commenter incorrectly characterizes the startup and shutdown work practice as an exemption and then cites case law to support its argument that the numerical standards must apply at all times. But the cited case concerned an actual exemption . The February 2012 final MATS rule did not contain any exemptions and no exemptions are added through this final action on reconsideration

. Instead, the EPA’s MATS rule has numerical standards that apply at all times except during startup and shutdown as82

defined in this final rule. During those periods, E GUs are required to comply with work practice standards issued pursuant to CAA section 112(h). Th e work practice was established by evaluating the performance of the best performing sources as determined by the EPA

.

T he commenter asserts without data fro m the best performing units, that the work practice we finalized today will cause more HAP emissions than if the numerical emissions limits applied during those periods. As discussed above, we question that assertion and believe it likely that HAP emission s during startup and shutdown under the final rule will be lower than required by the numerical standards.

Finally, the EPA complied with the requirements of CAA section 112(h) when determining that a work practice is authorized for startup and shutdown p eriods and in the establishment of the final work practice. In the February 2012 final MATS rule, the EPA indicated that it was establishing a work practice standard for startup and shutdown periods because the EPA did not have HAP emissions data during such periods. We did not receive any petitions for reconsideration that questioned the CAA

section 112(h) authority to establish a work practice standard from these or any other commenters, and, for that reason, we d id not address the issue in further detail in the proposed reconsideration rule. Since that time, we have confirmed that in addition to the lack of HAP emissions data for periods of startup and shutdown, we do not have measurement methodologies that are cu rrently able to accurately measure HAP emissions during periods of startup and shutdown. We maintain that collectively these conclusions support a determination that “the application of measurement methodology to [EGUs] is not practical due to technologica l and economic limitations

, ” consistent with CAA section 112(h)(2)(B). Commenters’ assertions that testing methodologies are available for HAP emissions are not supported in
the record, and the technological difficulties associated with accurately measurin g HAP emissions

cannot be immediately resolved for EGUs, notwithstanding whether in the future the EPA will have the ability to accurately measure such emissions because the technological issues associated with capturing and measuring a represe ntative samp le may be addressed.

The EPA also maintains that it would be very difficult to prescribe and enforce numeric emission limits during startup and shutdown periods because of the testing issues that currently exist

. See CAA section 112(h)(1). Conversely, the work practice that the EPA is finalizing today will be enforceable, and, contrary to assertions of the commenter s , will achieve significant HAP emission reductions from EGUs during periods of startup and shutdown. We also maintain that the final work practice is consistent with

CAA section 112(d) because it is based on the performance of the best performing EGUs.

Comment 8 3 : Commenter 20421 states that “ startup period ” does not constitute an emission standard,

but is a defined term. Commenter maintains that the term “ startup period ” describes a basic boiler operation that is determined by a number of factors including boiler design, function, fuel, associated peripheral equipment and other factors; these factors combined establish fo r each EGU what constitutes

“ startup. ” C ommenter states that because the definition of startup is not an emission standard, it does not fall under the purview of the CAA section 112(d) focus on the average of the best performing sources,

and the EPA cannot ignore subpopulations of covered sources when defining terms applicable to all

covered sources. C ommenter states that in order for the rule to be rational, it must begin by correctly defining the mode of operation, and the definition must be capacious eno ugh to accurately define that mode for every boiler regulated by the rule

– standards can then be applied to regulate emissions during the startup period

.83

Commenter 20421 states that the “ startup period ” at a power plant also reflects a specific level of engagement by engineers and others responsible for plant operations. Commenter notes that plant operators interface with the machinery in a power plant on three well

- understood levels: monitor, control, and diagnostic

– as the plant moves from one level t o the next, plant operators adjust their interface as appropriate for each level and undertake different tasks and different responsibilities. Commenter maintains that at the monitor level, operators monitor overarching parameters to ensure that the plant is meeting the parameters within an acceptable performance band, representing satisfactory performance of the overall plant and its critical systems and that in this monitor mode, the operator ’ s role is mostly passive and reactive. Commenter indicates that during control mode, operators actively engage with plant systems

– for example, starting equipment, changing valve positions, performing adjustments

– to affirmatively alter operating conditions to move the plant toward a different configuration or to im plement a specific procedure that requires a series of adjustments to plant systems. Commenter states that the diagnostic mode begins when troubleshooting is called for and that as a practical matter and viewed from the perspective of the plant operators, the startup period requires full engagement by plant personnel in control mode. Commenter states that control mode for startup does not conclude until all systems and equipment required for normal, steady state operation, including APCDs, have been placed into service and the plant is capable of steady state operation at its minimum

load level

– only at that point can plant operators shift to monitor mode, monitoring plant performance with specified parameters.

Commenter 20421 states that the EPA ’ s definit ion of startup as a percent load plus a period of time may accurately describe the timeframe during which plant personnel are in control mode for startup at a majority of power plants. However, commenter alleges that the timeframe is arbitrary as applied t o plants where plant operators are still fully engaged in control mode for startup beyond the period of time

the EPA identifies

– at those plants, operators may still be in control mode for startup, with the responsibility for overseeing and actively adjus ting plant systems to satisfy the requirements of the startup procedure, at a time when the EPA ’ s definition declares startup complete. Commenter maintains

that f rom a plant operations perspective, that definition is completely arbitrary and does not refle ct the continuing control mode of the plant operations. Therefore, to more precisely reflect this condition,

commenter states that the EPA should define the end of startup to correspond with the point when boiler operating conditions have stabilized and all APCDs are in service; if a timeframe must be utilized, the EPA should define startup to include a longer period of time under unusual circumstances. In this scenario, commenter request s that this additional language in quotes be inserted to define the end of

startup as

4 (or 3) hours after 25

- percent load is first reached or 12 (or 6) hours after first electricity generation, whicheve r occurs first, “ or in limited circumstances beyond those times when the permissive temperatures for an APCD extends beyond the periods of time used to define the end of startup. ”

Response to Comment 83 : In this final rule, the EPA is establishing definitions for startup and shutdown designed specifically to function as part of the work practice standards. Th e definition s

are necessary to define the period when the work practice will apply in lieu of the numerical

standards. We are unclear about what the commenter ’ s issue is with our use of definitions in this manner, but they provide no legal basis to support their claim that we erred by doing so.84

The remainder of the comment appears to be an argument for a more flexible standard that would

lik ely allow sources to set their own schedule without change. As explained above, we do not think that is consistent with the statute because work practice standards are required to be

consistent with CAA sections 112(d) or (f) and only available when it is infeasible to measure

HAP emissions

. The EPA acknowledges that plant operators may be “fully engaged” in adjusting their system beyond the defined end of startup in the final rule . However, as noted elsewhere in this document, the EPA believes that its ana lysis of the startup practices of the top performing EGUs and its final definition of “startup” adequately balances commenter s’ concerns with the requirements of CAA section 112. The EPA also notes that the goal of the Revised TSD analysis was to identify the approximate time it took, on average, to initiate operation of APCDs by the top performing 12 percent of EGUs to determine the appropriate time to end the startup period because we believe at that time sources will be able to capture and adequately mea sure HAP emissions using continuous emissions monitoring systems . The goal was not to seek the time it took for APCDs at all EGUs to become operational , a s that approach would not be consistent

with the statute , nor do we require that the identified controls be functioning at th e end of startup

. Instead, we require sources to comply with the numerical emissions limits at th at time in whatever manner necessary, including engagement of controls and/or continued use of clean

fuels.

1.2.5 Common stack

Summary of Comments Received Following November 30, 2012, Proposal

Comment 8 4 : Commenters 2 0256, 20277, 20281, and 2029 4 state 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. Commenter s recommend that the rule should make clear that the emission limits do not apply unless all EGUs sharing the common stack are not starting up or shutting down. Commenter

2 027 7 states that EGUs that share a common stack have the option of monitoring in the common stack and demonstrating compliance based on their combined emissions (40 CFR 63.10010(a)(2)).

Summary of Comments Received Following June 25, 2013, Reopening of Public Comment Period

Comment 8 5 : Commenters 20387, 20397, 20398, 20408, 20425, and 20428 state that the EPA should exempt all EGU s on a common stack from emission standards for periods when any EGU sharing the common stack is starting up or shutting down. Commenter 20387 indicates that t o do otherwise would create scenarios both many and confusing because of the number and type of EGUs that may exhaust through a common stack as well as the variety of APCDs (in common and/or otherwise).

Commenters 20399 and 20408 state that there is no wa y to accurately apportion emission rates back to the individual EGUs or assess the emissions contribution an EGU in startup has on the performance of a control device to accurately report emission rates for the EGU operating outside of startup. Commenters 20399, 20408, and 20409 ask that all emissions occurring during a startup or shutdown should be exempted from the 30

- boiler operating day rolling average.

Commenter 20428 states that EGUs that share a common stack have the option of monitoring in the

comm on stack and demonstrating compliance based on their combined emissions. Commenter notes85

that, although the work practice standards required during EGU startup and shutdown can be applied separately on each EGU, emission controls necessary to meet applicab le emission standards at the common stack may not be operating, or operating at the necessary efficiency, during an EGU ’ s startup and shutdown process; that could be true regardless of whether the EGUs on a common stack share all control devices, or have s ome individual controls. Commenter provides data for three EGU s sharing a common stack; data are shown for two EGU s already in operation with startup of the third EGU that is equipped with its own SCR. Commenter 20428 notes that Hg emissions measured in the common stack spike as the third EGU starts up before its SCR is operational. Commenters 20408 and 20428 note similar PM emission spikes for common stacks when one EGU is starting up, and potentially after a n EGU shuts dow n. Commenter 20428 states that, given the variable and significant change in measured emissions through a common stack when one EGU sharing the stack startups (or shuts down), the

MATS rule should make clear that the numerical emission limits do not apply to any of the EGUs sharing the common stack, if any one EGU on the common stack is starting up or shutting down.

Commenter 20408 notes that EGU ’ s with individual stacks are not required to monitor emissions after

an EGU enters shutdown. For a common stack

, commenter states that the MATS rule currently requires emissions monitoring any time any of the EGUs are operating which can be particularly difficult for continuous PM monitoring. Commenter indicates that when an EGU goes offline, there is a period of u p to 8 hours when air flow is maintained high through the EGU to cool it in preparation for maintenance; because of shedding of ash in the EGU and ductwork during cool down and diluted CO 2 emissions, calculated PM (as well as HCl and Hg) emission rates wil l appear to be high and will not be correct for an EGU or EGUs that were operating normally during this period. Commenter recommends that the EPA consider excluding up to 8 hours of monitored data after a n EGU has shutdown in a common stack configuration.

Commenter 20398 notes there is no obvious solution to calculating SS emissions from a common stack that does not involve installing separate monitoring systems at great expense.

Commenter 20421 supports language to address startup and shutdown impacts for common stacks.

Commenter states that in order to accurately attribute emissions from each boiler, the periods when one boiler is in startup or shutdown should exclude the emissions measured at the commo n stack from the

MATS air emission limits.

Commenters 20417 and 20419 support commenter s that have interpreted how the startup and shutdown definitions and work practice provisions apply to EGUs that share a common stack. Commenters agree

that although wo rk practice standards would be applied separately to each EGU that shares a common stack, numerical emission limits should not apply if one EGU sharing a common stack is starting up or shutting down. Commenters state this is the only way for EGU s which sha re a common stack to comply with the prohibition on the use of data recorded during startup or shutdown to demonstrate continuous compliance. Commenters say, further, application of numerical emissions limits while one EGU sharing

a common stack is startin g up or shutting down defeats the purpose of providing work practice standards during periods of startup and shutdown.

Commenter 20420 states that MATS is not clear on how the work practice standards should be applied

when one EGU venting to a common stack is starting up or shutting down while another EGU venting to the common stack is in operation. C ommenter states that when emissions are being measured in the86

common stack, emissions from the EGU starting up or shutting down canno t be differentiated from the

EGU s that are operating normally. Commenter states that the startup and shutdown work practice standards should apply to all EGU s venting to a common stack when any one of the EGU s is starting up or shutting down while any othe r EGU is in operation.

Commenter 20403 supports language to address startup and shutdown impacts for common stacks.

C ommenter states that the startup and shutdown of a boiler that shares a common stack with another boiler will impact the emissions in the common stack. Commenter states that due to this impact the periods when one boiler is in startup or shutdown should exclude the emissions measured at the common

stack from the MATS air emission limits. C ommenter suggests that additional language be added stating that the boiler remaining in operation maintains its APCD throughout the period during which the other boiler is starting up or shutting down.

Commenter 20391 states that the rule must reconcile application of st artup and shutdown provisions to

common stacks. Commenter states that the proposed reconsideration rule also does not resolve how the startup and shutdown definitions and work practice provisions apply to EGU s that share a common

stack. Commenter states th at EGUs that share a common stack have the option of monitoring in the common stack and demonstrating compliance based on their combined emissions. Commenter states that although the work practice standards can be applied separately on each EGU , emission c ontrols necessary to meet applicable emission standards at the common stack may not be operating, or operating at the necessary efficiency, during a n EGU ’ s startup and shutdown process (regardless of whether the

EGU s on a common stack share all control dev ices or have some individual controls). Commenter states that for this reason, the rule should make clear that the emission limits do not apply to any of the EGU s sharing a common stack flue if any one EGU on the common stack is in the process of starting up or shutting down.

Commenter 20391 states that the current definition of shutdown in the MATS rule starts when either none of the steam from the boiler is used to generate electricity for sale over the grid or for any other purpose, or at the point of n o fuel being fired in the boiler, whichever is earlier, and ends when there is both no electricity being generated and no fuel being fired. Commenter states that for a single stack, there are no further reporting requirements after no fire or no generation , even though there is still hot gas being emitted through the stack with the continued operation of fans until cool down. Commenter

states that on a common stack, however, you can have one EGU operating and the other shut down with hot gases being emitted in the common stack until the fans are shutdown. Commenter states that consequently, there can be significant spikes in PM emissions in the common stack during a shutdown

until the fans of the shutdown EGU are turned off. Commenter states that

, therefore, the EPA should define shutdown as beginning with the end of firing fuel or no generation, and ending when the ID fans

of the shutdown EGU are turned off.

Commenter 20399 states that numerical emission limits should not apply if any one EGU sharing a

comm on stack is starting up or shutting down. Commenter urges the EPA to not attempt to calculate startup and shutdown emissions from common stacks, but rather apply its proposed startup and shutdown language anytime any one EGU that shares a common stack with another affected EGU starts up or shuts down. Commenter states that the effect of low diluent gas concentrations and electrical loads of zero from the EGU in startup further complicates the issue of common stack emission rates with one EGU in startup.87

Co mmenter 20400 states that the proposed reconsideration rule does not clearly resolve how the startup and shutdown definitions and work practice provisions apply to EGU s that share a common stack and

common emissions controls.

Commenter 20400 states that i t’s Allen and Marshall Stations are examples of this situation. Commenter

states that at Allen, three EGU s share one common FGD system and exhaust into one stack flue, and the

other two EGU s share another common FGD system and exhaust into a second stack flue. Commenter

states that Marshall Units 1 and 2 share a common FGD system and a single stack flue, whereas Units 3 and 4 each have their own FGD system and stack flue. Commenter states th at each of the generating

EGU s at Marshall and Allen has its own particulate control system, which is operated during startup and shutdown in accordance with good practice as defined in a state

- approved work practice manual.

Commenter states that the Allen units and Marshall Units 1 and 2 have no SCR (SNCR and low NOx burners are used for NOx control), but any future installation of SCR would most likely include a separate SCR for each EGU . Commenter states that in each of these installations, the CEMS are located

on the common flue for each EGU or group of EGU s sharing an FGD system, and all emissions compliance tests are performed on these common flues.

Commenter 20400 states that under the current MATS rule, compliance with emissions standards for

affect ed EGU s sharing a common stack (that is, through the same exhaust flue) may be determined as if the group of EGU s was a single source (40 CFR 63.10009(l)), and in that case the measured emissions rate must be assigned to each EGU that shares the common sta ck. Commenter states that however, the work practice standards for startup and shutdown apply to each individual EGU . Commenter supports applying the work practice standards at an EGU level. Commenter notes that is important because the startup or shutdown of each individual EGU creates a process imbalance that will affect emissions, and the contribution to the measured stack emissions from that startup will render the measurement not representative of normal operation.

Commenter 20400 recommends that all periods should be excluded from the compliance averages

whenever one or more affected EGU s sharing a common stack is considered in startup or shutdown.

Commenter states that for example, if the EPA defines startup as the period from initial combustion of

f uel through 25 percent of the maximum load on an EGU plus 3 hours, that criteria would apply when any of the individual EGU s feeding a common flue meet that criteria, or if any EGU is considered in a

shutdown.

Commenter 20400 states that including periods of startup and shutdown in an output

- based measured emissions rate would present particular problems when one EGU is in startup or shutdown and is not generating electricity. Commenter states that in those situations, emissions from the EGU in startup or shutdown would be included in the compliance average for the other on

- line EGU s but the denominator would not include any generation associated with that EGU . Commenter states that compliance with an input

- based standard would also be impacted because the flue gas from the EGU in startup or shutdown will be subject to process imbalance, which may impact either the performance of the control equipment or the ability to accurately measure emissions. Commenter states that it would be inappropriate to conduct an emissions test during these unstable and non

- routine conditions. Commenter states that also, the ICR database used to develop the MATS standards did not include any data obtained during periods

where one or mor e EGU s tied to a common stack were in startup or shutdown conditions. Commenter88

states that as a result the EPA had no emissions data or CEMS data during those periods so that it could appropriately set emissions limits during these periods where the emiss ions control equipment is not functioning at its intended design conditions. Commenter states that the EPA should therefore consider these periods as being subject to the work practice standards and not included that data when determining compliance averag es.

Commenter 20400 recommends that the EPA use the following approaches to address startup and

shutdown emissions for EGU s that share a common stack:

• For affected EGU s the either share a common final control device such as an FGD, or have completely s eparate control devices, share a common stack, and report a single measure value from CEMS, define startup and shutdown periods as any period of time where any of the individual generating EGU s meets the criteria for startup and shutdown. For example, if t he EPA defines startup for a single EGU as the period from initial firing of fuel through 25 percent of maximum generating capacity plus 3 hours (not to exceed 6 hours after start of generation), the startup exclusion would apply to any data gathered on

a common stack where any of the EGU s has begun to combust fuel and has not reached 25 percent load plus 3 hours or 6 hours after the EGU has begun generating electricity. For shutdown, data would be excluded whenever any of the common EGU s ceases to
generate electricity until the EGU ceases to fire fuel. This approach is particularly important in cases where EGU s do not share a final control device. In such cases, a

smaller EGU that has completed a startup could be outstripped by the starting of a larger

EGU when the second EGU ’ s control equipment has not reached its full effectiveness.

• Work practice standards will apply individually to each EGU during its startups and shutdowns to provide assurance that all control systems will be operated at all times coal is combusted in accordance with best practice.

• Because the rule requires that CEMS be operated at all times, if a n EGU is in startup or

b egins startup after the startup period has ended for one or more of the other common

EGU s, the CEMS DAHS should still substitute a default generation value (MW) for the

EGU in startup. As noted separately in our comments, commenter recommends a default value of 5 percent of rated capacity for any period where a n EGU is combusting fuel but the electrical generation is below the default value. Likewise, if a n EGU initiates

shutdown while one or more EGU s remain on

- line, the default ge neration value should be

included for that EGU until the shutdown concludes (the EGU ceases to combust fuel or

the EGU comes back on

- line).

Commenter 20415 states that if CEMS or sorbent trap monitoring systems are utilized on a common

stack and one or mo re of the EGU s feeding that stack are in startup or shutdown mode, then the emissions indications in the common stack are not indicative of normal operation of any of the EGU s. Commenter states that this situation could be avoided with use of monitoring sy stems on every individual boiler, but such installations are very expensive and duct arrangements might not be able to accommodate the monitors, so there are legitimate reasons to use monitoring on the common stack.

Commenter states that in such situations

, it recommend s that the EPA consider use of parametric monitoring or other parameters to indicate normal operation of the boiler(s) that are not in SS mode89

while one or more other boilers are in SS , with the monitoring data during that period not used for compliance purposes. Commenter states that then when the SS period ends, emissions data would be included in the compliance data set.

Commenter 20426 requests that the EPA clarify that the time period associated with each individual

EGU sharing a common stack be considered “ startup, ” and that these times are to be excluded from MATS compliance demonstrations.

Commenter 20429 states that exempt excess emissions from a n EGU in SS on a common stack may

cause the stack as a whole to exceed emission limits. Commenter believes the rule should clearly state

that emission limits for EGU s on a common stack do not apply to any of the EGU s if any one EGU on the common stack is in SS mode.

Commenter 20431 states that that EGUs that share a common s tack have the option of monitoring in the common stack and demonstrating compliance based on th eir combined emissions. 40 CFR 63.10010(a)(2). Commenter states that because its Bailly Generating Station has two EGU s that share a common stack, those EGU s are directly affected by the definition in this part of the rule. Commenter

states that although the work practice standards required during EGU startup and shutdown can be applied separately on each EGU , emission controls necessary to meet applicable emissio n standards at the common stack may not be operating, or operating at the necessary efficiency, during the EGU startup and shutdown process. Commenter states that this is true regardless of whether the EGU s on a common stack share a control device ( e.g., FGD), or have some individual controls, as in the case of the Bailly Station generating EGU s. Commenter states that for this reason, the rule should make clear that the emission limits do not apply to any of the EGU s sharing the common stack, if any one EG U on the common stack is starting up or shutting down.

Comment 8 6 : Commenter 20427 states that many older EGU s use shared stacks and an expanded exemption would increase pollution; if all EGU s were exempted when any one EGU is within 4 to 12

hours of star tup, the EGU s would largely avoid the numeric standards. Commenter citing a facility with

3 EGU s that share a common stack, indicates that, individually, startup defined as 4 hours past 25 percent load would exempt numeric limits for a total of 476 hours ( 164 hours, 143 hours, and 169 hours

for each of the 3 EGU s). Commenter then notes that exempting numeric limits when any one EGU fell within the startup period would allow the EGU s to operate for 412 hours ( each ) without numeric limits, and a total of 1,23 6 hours ( provides an attachment to its comment letter, with hour

- by

- hour operating data and startups on 3 EGU s sharing a common stack at 1 facility for 2011). Commenter states there are

over 100 EGU s where at least 3 or more EGU s share a common stack.

Commenter 20427 states there is no reason for the proposed expansion of the startup definition to cover common stacks, and that measurement device placement allows measurement of emissions from

individual EGU s, even where EGU s share a stack. Commenter stat es that concerns can be solved by requiring emission and flow measurement in the duct from each EGU prior to combination in the

common stack or flue. Commenter states that geometry constraints can be addressed by ductwork retrofits, very few EGU s would be incapable of conducting the retrofits, and any expansion in the startup work practice should be limited to only those EGU s incapable of measuring emissions from individual stacks, not all EGU s using a shared stack.90

Commenter 20422 notes that EGUs have 2 o ptions for monitoring emission rates for common stack

EGU s: EGUs can monitor individual EGU emissions at the duct leading to the common stack, or monitor the common stack and attribute the average recorded emission rate to all of the EGU s that share

the co mmon stack. If EGU operators have concerns about emissions from other EGU s that share the common stack during startup or shutdown, commenter states industry has the option to monitor

individual EGU emissions at the duct leading to the common stack and can thus easily avoid any problem related to emissions from other EGU s sharing the common stacks affecting their ability to comply

Commenter 20433 rebutted Commenter 20422 ’ s assertion that it would be “ easy ” to monitor at the duct leading to the common stack as being inaccurate and shows a basic misunderstanding of the character of the ductwork leading to many common stacks. Commenter 20433 notes that the sampling locations available in most utility ductwork arrangements are far from ideal and that the ductwor k leading to the common stack generally does not have an appropriate location in the ductwork, the access, and/or the platforms necessary to support the monitoring systems, much less the reference method testing required to certify and to maintain the syst ems. Commenter 20433 states that over the years, the utility industry has spent millions of dollars installing elevators, constructing platforms, and installing sampling ports at proper stack sampling locations, which are most often within the common stack (for common stack

EGU s) and maintains that ducts leading to common stacks often do not meet the minimum sample location criteria set forth in 40 CFR Part 60, Appendix A, Method 1, Section 11, which requires minimum siting criteria when locating testing lo cations on a duct or stack. Commenter 20433 notes that EPA Performance Specification 2 in 40 CFR Part 60 Appendix B requires a minimum of two duct diameters downstream from the nearest control device and a half duct diameter upstream from the

effluent exha ust or control device and that the majority of common stack EGU s were built without regard for CEMS siting in the ductwork, and there is simply not enough undisturbed duct lengths suitable for proper CEMS siting criteria. Commenter 20433 alleges that due t o the physical configuration of an EGU, it is often not possible to reconfigure the ductwork to create an appropriate sampling location.

Comment 8 7 : Commenter 20390 states that once startup and shutdown have been more clearly defined,

the issue for EGUs with a common stack can be addressed. Commenter not es that

, generally, the impact on the common stack emissions is relatively small as the EGU that is starting up is at minimal flow

conditions when the total emissions are calculated. Commenter states that emission level would be impacted if relatively high load (e.g., 50 percent total capacity) is required prior to starting up APCD.

Response to Comments 84

- 87 : Many commenters suggested that the February 2012 final rule was unclear with respect to startup and shutdown requirements for EGUs that shared a common stack. The

EPA disagrees with those commenters. 40 CFR 63.10010(a)(2) of the final rule required owners or operators of EGUs with common stacks to either monitor the EGUs separately or monitor the common stack and assign the same emissions value to each EGU. The EPA did not include separate specific requirements for monitoring during periods of startup or shutdown because it was not necessary, and we continue to believe that sources should be required to monitor, record

, and report emissions in a manner that ensures compliance with the standards at all times. The use of a common stack is a convenience for sources that may not be used as an excuse to av oid compliance assurance requirements, even if an

additional cost is incurred for sources with a common stack.91

As in the February 2012 final rule, owners and operators of EGUs with common stacks are required to monitor and report emissions at all times t he EGUs are operating. Also, as with the February 2012 final rule, work practice standards appl y during periods of startup or shutdown. Owners or operators of EGUs with common stacks may either monitor each EGU separately upstream of the common stack or fr om the common stack. Monitoring must be operational at all times that fuel is being combusted, and compliance with numeric emission limits is required except for units that are operating in periods of startup or shutdown. Should an owner or operator choose to monitor the common stack, then emissions obtained from the monitoring will be applied to every EGU in an operating mode other than startup or shutdown at the time of measurement. This approach remains consistent with that of the February 2012

final rul e, and is not expected to be problematic emissions

- wise for any EGU using a common stack,

because the EGUs in periods of startup or shutdown are required to use clean fuels and to operate their

PM controls within 1 hour of primary fuel combustion and the E GUs operating not in periods of startup or shutdown are required operate such that they meet their emissions limits. And, as we have stated previously, it is our understanding that sources almost always operate their units to ensure a considerable complian ce margin to ensure that they comply with emissions standards over a continuous period. The fact that sources are able to operate with a compliance margin generally demonstrates that the numerical

standards include sufficient variability to address all operating conditions , including periods of startup and shutdown, and that the standards can be achieved in an economical manner.

As mentioned later, during startup or shutdown periods for EGUs using common stacks, the

reconsidered rule also allows use of a default electrical load and default diluent values ; use of th ese value s should further alleviate commenter concerns about low electrical output calculations.

As described above, the re is no need to resolve how the startup and shutdown provisions apply to EGUs

that share a common stack because the provisions of the February 2012 final rule , with some minor changes to address industry concerns, adequately address the applicable compliance assurance provisions

. See 77 FR 9371, 9382 [concerning measurement instruments to be operated, emissions measured, and emissions reported during periods of startup and periods of shutdown]; 40 CFR 63.10010(a)(2)(i) and (ii) [concerning use of measurement instruments in individual ducts leading to common stacks and in common stack measuring emissions from all EGUs]; and docket ID EPA

- HQ

OAR

- 2009

- 0234

- 20126 ( Volume 2, pages 22, 93, 359, 400, 424, 442, and 460 )

.

More than one commenter suggested that every EGU sharing a common stack should be exempt from numeric emission limits when any EGU sharing the stack is in startup or shutdown mode. The EPA disagrees with those comments. The reconsidered rule does not allow all the EGU s sharing a common

stack to avoid compliance with the numer ic emission limits when any one of those EGU s is in a period of startup or shutdown. We believe that such an allowance would constitute an improper exemption

from the requirement for sources to comply with the applicable NESHAP standards at all times. Thus

, EGUs venting to a common stack that are not in startup mode must continuously comply with the

numerical limits

, even while another EGU sharing the common stack is complying with the work practice requirements.

A number of commenters provided data that they allege supports the exclusion of data from periods of startup and shutdown on a common stack whenever any EGU sharing the stack is in startup or shutdown

mode. As a preliminary matter

, we note that these data were generated before the EGUs were required to compl y with the final MATS standards (i.e.

, the numerical emission limits and the work practice92

requirements), and the commenters do not indicate that the EGUs were operating in compliance with the

final stan dard at the time these data were collected. Furthermore, we do not know if the EGUs tested were among the best performers for either the numerical limits or the work practice requirements (e.g.

, did the EGUs startup on clean fuels alone). We further note t hat the data were collected over periods of time that are inconsistent with the final definition of startup. In any case, w e continue to believe that HAP emissions during startup and shutdown periods at the best performing EGUs is as low as

, or lower

than

, those level s required when the numerical limits apply.

As demonstrated in the figures submitted by one commenter, PM emissions during startup periods as measured in a common stack by a CEMS that did not include use of a diluent cap are about one

- half th e PM limit on an hourly basis within 4 hours after generation starts. As demonstrated in another figure submitted by commenter 20428, hourly Hg emissions values during startup periods as measured in a common stack by a continuous monitoring system appear t o be below the value of the emission limit within 12 hours of control device startup. Given the short 4 hour duration for startups after electricity generation and the low HAP emissions expected due to the work practice requirements, we believe EGUs using a common stack but not operating in periods of startup should be able to comply with the

numeric standards

. As demonstrated in a figure subm itted by C ommenter 20428, PM emissions during shutdown periods as measured in a common stack by a CEMS that did not include use of a diluent cap

are at about the level of the PM limit on an hourly basis within 9 hours after generation ends for 11 of 15 shutdown periods. Given the short duration for shutdowns (when compared to the 30

- boiler operating day rolling average period of the emission limit), emissions from EGUs in a common stack but not operating in periods of shutdown do not appear to be problematic for compliance purposes , and, as with the data from startup periods, they were collected before the source was required to comply with the final work practice standard

.

One commenter is incorrect in stating that EGUs with individual stacks are not required to monitor emissions during shutdown; Table 3 to subpart UUUUU requires EGU s to operate all continuous monitoring systems (CMS) during shutdown and section 63.10000(a) requires EGU owners or operators to meet the work practice requirements of Table 3.

The EPA disagrees with the suggestion by one commenter that no obvious soluti on exists to calculating startup or shutdown emissions from a common stack that does not involve installing separate monitors at great expense, for, as shown in figures submitted by another commenter, CEMS in common stacks

appear to work well

– even when d iluent caps are not used.

Based on the figures submitted by one commenter, the EPA finds no reason not to continue to require assignation of emissions data from CEMS in a common stack to each EGU operating not in a period of startup or shutdown.

The EPA disagrees with commenters who suggest the only way for EGUs with monitoring in a common stack to comply with the prohibition against the use of data recorded during startup or shutdown is not to use those data when any EGU in the common stack is starting u p or shutting down. EGUs not in startup or shutdown periods but in common stacks still have emissions; those emissions are subject to numerical emissions limits. Owners or operators who are concerned about applying the common stack monitoring

values to ind ividual EGUs can install separate monitors for each EGU upstream of the common stack.93

With respect to the commenter who suggests that when emissions are being measured in the common stack, emissions from the EGU starting up or shutting down cannot be diff erentiated from the EGUs that are operating normally, the EPA notes that as mentioned above, o wners or operators who are concerned about being able to differentiate individual EGU emissions in a common stack can install separate monitors for each EGU upstr eam of the common stack.

The EPA agrees that EGUs in periods other than startup or shutdown need to operate their air pollution control devices continuously, but the A gency disagrees that additional requirements in this rule are necessary. These requireme nts are already contained in 40 CFR 6 3.6(e )(1)(i) of the general provisions,

and must be followed

. 10

To the commenter who suggests that because emission controls necessary to meet applicable emission standards at the common stack may not be operating, or operating at the necessary efficiency, during an EGU’s startup and shutdown process (regardless of whether the EGUs on a common stack share all

c ontrol devices or have some individual controls), all EGUs sharing the common stack should be exempt from numerical emission limits when any EGU is in startup or shutdown mode, the EPA disagrees, noting that, as described above, figures showing emissions d ata from EGUs sharing a common stack and in startup and shutdown mode with varying degrees of emissions control do not exhibit problematic conditions for other EGUs sharing the common stack but not in periods of startup or shutdown from showing compliance with the averaging period associated with the emissions limit. The EPA also

believe s that HAP emissions during periods of startup and shutdown are likely to be close to or lower than during other operating periods for the best performing EGUs and the EGUs complying with the final work practice requirements, contrary to the commenters’ implication that startup and shutdown emissions will necessarily lead to greater HAP emissions.

The EPA agrees with the commenter who states that perceived problems with the use of common stack monitoring could be avoided with use of monitoring systems on every individual boiler; the A gency also acknowledges that installation of individual EGU monitoring systems could be expensive and difficult;

however the EPA reminds the co mmenter and others that they are required to provide appropriate

accommodations for performance tests, as described in section 63.7(d)(1), whether from the common

stack or individual stacks. The EPA also notes that in most cases, existing guidance provides instructions for installing monitoring instruments in challenging locations.

Comment 88 : Commenter 20420 suggests that the EPA should clarify the application of the startup and shutdown work practice standards to EGUs demonstrating compliance in accordance with 40 CFR 63.10010(a)(2)(ii) in Table 3 to subpart UUUUU.

Response to Comment 88 : As mentioned earlier, th is final rule cl arifies startup and shutdown work practice standards for EGUs that share a common stack

.

10 See 40 CFR 63.6( e )(1)(i), which says that “...At all times, including periods of startup, shutdown, and malfunction, the owner or operator must operate and maintain any affected source, including associated air pollution control equipment and monitoring equipment, in a manne r consistent with safety and good air pollution control practices for minimizing emissions...”94

1.2.6 Allow site

- specific standards

Summary of Comments Received Following November 30, 2012, Proposal

Comment 8 9 : Commenter s 2 0246, 20248, 20256, 20269, 20276, 20279, and 2028 8 ask that the EPA allow EGUs the option of developing site

- specific or unit

- specific work practices that would apply during periods of startup and shutdown in order to take into consideration different boil er types, air pollution control equipment and other site

- or unit

- specific characteristics that would better reflect the diversity of EGU operations.

Commenters 2 0269 and 2027 9 note that creating SS plans is a time

- consuming process and that it will

be more efficient and cost

- effective for some EGUs to follow the EPA ’ s proposed work practice

standards. Commenter s state h owever, many EGUs would require site

- specific startup and shutdown procedures to ensure safe operating conditions, to comply with requirements established by other EPA rules, or to avoid equipment damage. Commenter s ask that deviations from the site

- specific SS plan (if allowed) not be considered a violation as long as “ the applicable emissions limits are not exceeded and the EGU is operating with the intent of meeting the limit. ”

Commenter 2 028 8 states that work practice standards should reflect that each generating EGU is different in its construction, fuel, emissions controls and th at the characteristics of startup and shutdown events vary greatly. Commenter recommends that separate work practice standards be developed for every affected EGU under various startup and shutdown scenarios, reflecting the capabilities of control equipmen t to operate safely and effectively during different phases of the startup and shutdown process.

Commenter provides further notes regarding specific startup and shutdown work practices and that work practice standards should also recognize that EGUs must c onduct periodic maintenance activities.

Commenter 2 024 8 states that the EPA ’ s current definition (and proposed changes) does not solve the problem of how to account for emissions during startup and shutdown and presents compliance challenges. Commenter states that it has worked with many permitting agencies to develop startup and shutdown requirements in Title V permits and requests that the EPA modify the startup and shutdown work practice standard to enables EGU owners to rely on startup and shutdown p lans in their Title V permits. Commenter states that t his structure would allow EGU owners to work with their permitting agencies to develop a startup and shutdown exemption period that acknowledges challenges specific to

each EGU in addition to having federally enforceable startup and shutdown requirements. According to

commenter , the Proposal would result in instances where existing Title V permits and the MATS rule could conflict, and result in conflicting startup and shutdown c ompliance periods. To illustrate how Title V permit definitions of startup and shutdown can be different to accommodate unit

- specific control equipment, commenter provides examples of startup language from current operating permits.

Commenter 2 024 8 state s that the need for EGU

- specific startup and shutdown language is particularly important for EGUs that cycle (in contrast to base

- load EGUs ) in order to avoid creating a situation

where EGUs would be required to stay on

- line out of merit and displacing mor e efficient EGUs to avoid multiple startups during a 30

- day averaging period. Commenter 2 024 8 states that the EPA has implemented a similar approach of EGU

- specific plans under its existing CEMS regulation (40 CFR

Part 75).95

Commenter 2 024 6 states that the EPA should allow affected sources to operate according to site

- specific

start

- up and shut

- down plans that are approved by designated authorities (state agencies). Commenter said any start

- up and shut

- down requirement should enable the facility to freely g enerate and use electricity during start

- up and shut

- down consistent with equipment and manufacturer requirements and to allow operation according to start

- up and shut

- down plans which identify the proper firing of clean and primary fuels for minimizing em issions in a manner consistent with equipment and safety requirements.

Commenter 2 027 9 states that the proposed requirement that EGUs start certain pollution control technology as expeditiously as possible ’ after startup, whereas all other controls must s tart immediately

illustrates the EPA ’ s limited recognition of operating constraints during startup and shutdown and failure to acknowledge the diverse operating requirements of EGUs subject to the MATS. Commenter

recommends that the EPA adopt additional compliance options that would supplement the proposed work practice standards for startup and shutdown and address the unique operating constraints facing

certain EGUs.

Commenter 2 027 9 states that to accommodate its unique operational constraints, each EGU has a plan for starting up safely in a manner that minimizes emissions, protects equipment, and complies with existing regulations. Commenter states that although the EPA ’ s proposed approach will address safety

and operational concerns at some EGUs, it could lead to unnecessary safety risks and equipment damage if plant workers disregard existing plant procedures and start controls before it is safe to do so in order to avoid noncompliance.

Commenter 20408 suggests that startup and shutdown should be defined on a unit

- by

- unit basis in consultation with the state or local permitting authority. Commenter notes that this should be based on the type of boiler, the emission controls attached, and historical information on previous SS durations;

this SS time or a set of operational criteria could then be included in the Title V operating permit along

with recordkee ping and reporting requirements.

Summary of Comments Received Following June 25, 2013, Reopening of Public Comment Period

Comment 9 0 : Commenter 2039 2 states that it continues to believe and support a unit

- specific approach that would be a part of the ope rating permit under which the EPA would have a decisional role in approving. Commenter maintains that the approach outlined in the June 25, 2013, notice of ending startup 3 hours after achieving 25 percent of nameplate capacity or 6 hours after the first g eneration of electricity would place some of its EGUs into violation situations that it would likely not be able to correct when there were unanticipated startup and shutdowns within the same averaging period due to

EGU malfunctions. Commenter states that extending the time period to 4 and 12 hours would reduce its compliance risk, but would not necessarily address the issues that an EGU

- specific plan would cover.

Commenter 20392 states that approach provided in the June 25, 2013, notice appears to be a su rrogate for achieving an appropriate flue gas temperature at which the EGU and the emissions controls would be able to operate safely and effectively. Commenter believes that, as such, it would be more appropriate to base the end of startup on the achievem ent of a certain flue gas temperature needed to allow for the safe and effective operation of the EGU and the emission control equipment and that this type of approach would most effectively be implemented on a unit

- specific basis considering the overall d esign and96

operation of the boiler, as

- well

- as the mix of pollution control equipment that has been determined appropriate and approved by the permitting authority. Commenter maintains that the imposition of a one size fits all requirement for the numerous differences in the operation of the many different types of EGUs in operation today does not provide a significant environmental benefit over allowing the permitting authority to develop/consider and approve a startup plan in the permit that would reduce

e missions to the greatest extent practicable, while allowing the EGU to operate according to the good engineering practices that would provide for the safety of the plant personnel and the continued life of

the EGU.

Commenter 20396 support s Commenter 20419 ’ s comments to have an approach where a n EGU elects

either to follow the EPA ’ s definition of startup or to work with regulators to develop an individualized

SS plan.

Commenters 20396, 20397, and 20428 prefer development of a unit

- specific plan, and only a s an alternative, support revised definitions of startup.

Commenter 5840 states that ’ its preferred solution is to establish unit

- specific work practices that define the beginning of startup and the end of startup, with the practices and definitions subm itted to and approved by the permitting authority. Commenter notes that it is its experience that there are necessary variations in startup procedures even among “ identical ” or similar supercritical EGUs based on specific design and equipment consideration s and that startup procedures are typically developed based on the equipment at each EGU.

Commenter 20407 states that each individual EGU is unique in its standard protocols for completing a startup and that this uniqueness is derived from the type and ma nufacturer of the EGU, its controls, required auxiliary equipment, type of APCDs, and configuration of the APCDs. Commenter notes that, furthermore, each startup event for a given EGU is unique and poses its own set of challenges.

Commenter does not believ e that it is appropriate, given the large number of operational variables that can occur and affect a startup event, to establish a specified time limit to a startup event applicable to all EGIs as proposed in the reconsideration. Commenter believes that t he most appropriate standard related to startup would be to require EGUs to develop a unit

- specific Startup and Shutdown Plan. Commenter

states that records should be kept to document adherence to the plan. Commenter states that as expressed previously, an EGU experiences significant economic losses while in a startup condition, and as such, there is no incentive to remain in startup mode. Commenter does not believe that it is appropriate or necessary to require that a unit

- specific Startup and Shutdown Pla n be approved by the local permitting authority. Commenter states that however, if the EPA chooses to implement startup and shutdown provisions through approval by a permitting authority, the EPA must formally propose guidance to ensure consistency in appl ying these provisions.

Commenter 20419 states that that the EPA should allow EGUs to either (1) elect to comply with the definitions of the end of startup as proposed in the EPA ’ s Proposed Reopening, or (2) determine the boundaries of startup in a SS plan based on manufacturer specifications or unit

- specific considerations. Commenter urges the EPA to adopt both options for defining startup and shutdown. Commenter states
that creation of SS plans is a time

- consuming process, and some EGUs will prefer t o use the EPA ’ s definition for the end of startup. Commenter states that but for EGUs where site

- specific considerations prohibit placing control equipment in service in a timeframe that would meet the proposed definition of97

the end of startup, SS plans wo uld provide these EGUs with the flexibility necessary to implement efficient and safe operating practices without risking noncompliance with the MATS. As an alternative,

commenter reiterate d its support in its prior comments for the EPA ’ s proposal in the P roposed

Reconsideration Rule to allow EGU s to start limestone injection, dry scrubbers, SNCRs, and SCRs when it is practicable to do so. However, as noted in commenter ’ s prior comments, the EPA should provide that all APCDs begin operating when it is pract icable to do so

.

Commenter 20419 states that as explained in EPA

- HQ

- OAR

- 2009

- 0234

- 20269 , for EGUs that select the second option, SS plans would allow owners and operators to determine when, under the MATS, startup ends based on parameters that are easily monitored at that EGU . Commenter states that these parameters could be based on requirements in other rules to which EGUs are already subject. Commenter states that for example, EGU s subject to 40 CFR Part 75, Appendix A (which governs continuous emission monitoring for affected EGU s under the Acid Rain Program) already are required to define the EGU ’ s ranges of operation and normal load. Commenter states that startup for such EGU s c ould easily be based on these ranges of operation. Commenter notes other EGUs may need to designate the end of startup as the point in time when the EGU reaches a certain temperature so that air pollution control equipment can be safely and effectively ope rated.

Commenter 20419 states that allowing EGUs the option to develop SS plans would ensure that EGUs can operate safely and efficiently without jeopardizing compliance with the MATS. Commenter states that this option also would avoid potential conflicts between the MATS and other applicable requirements, would regulate SS more efficiently than applying multiple, overlapping SS requirements, and would reduce unnecessary administrative burdens on regulated sources. For these reasons, Commenter urges the EP A to allow EGUs to elect to either follow the definition of the end of startup as proposed in the Proposed Reopening, or to follow an individualized SS plan.

Commenter 20417 suggests that the EPA allow EGUs two compliance options

– the y can either (1) ele ct to comply with a definition of the end of startup similar to that described by the EPA or (2) determine their individual boundaries of startup in a SS plan based on site

- specific considerations. Commenter

states that, creation of SS plans is a time

- cons uming process, and some EGUs may prefer to use the MATS Rule definition for the end of startup and will be able to do so without compromising safety or reliability. Commenter goes on to say, but for EGUs where site

- specific considerations require the use o f a different definition, SS plans would provide these EGUs with the flexibility necessary to implement efficient and safe operating practices without risking noncompliance with the MATS.

Response to Comments 89 and 90 : The EPA is finalizing definitions and work practice standards for startup and shutdown periods based on the performance of the best performing sources during those periods. The EPA does not believe individual startup and shutdown plans

, essentially allowing sources

to continue their curren t approach without change

, are consistent with the statute. Regarding the

co mmenter’s suggestion to establish a process by which an EGU may petition for the establish ment of a unit

- specific startup period on a case

- by

- case basis to ensure the efficient and safe operation of the APCD, the EPA notes that such a process for developing an alternative emissions limitation already exists in the general provisions of EPA’s P art 63 regulations

. See 40 CFR 63.6(g). In addition, we are including provisions related to th e petition process at 40 CFR 63.10030.98

1.2.7 Title V, state, or local permitting

Summary of Comments Received Following June 25, 2013, Reopening of Public Comment Period

Comment 9 1 : Commenter 20401 requests the Reopened Rule be revised to allow EGUs to develop their

own site

- specific work practice standards for startup based on the manufacturer ’ s specifications for the AQC equipment at each site, and states that that startup should be defined on a site

- specific basis that

rests on the recommended specifications and requirements for the AQC equipment associated with the EGU, and is submitted and approved by the permitting authority and placed in the facility ’ s Title V permit. Commenter maintains that EGUs already have considerable incentive to deve lop efficient startup plans since it is economical for EGUs to end startup quickly and reach stable operation with efficient heat rates. Commenter would, as an alternative, support the option offered by other commenter s that startup ends 12 hours after fir st electricity generation.

Commenter 5833 suggests that the startup period be defined by “ work practices ” rather than a fixed time period of several hours and indicates that these work practices could be developed for individual EGUs and written into perm its issued by the facility ’ s state regulatory agency. If this approach is not acceptable, commenter supports the approach provided by Commenter 20428.

Commenter 5840 states that work practices for periods of startup and terms such as the “ end of startup ”

should be defined on an individual basis for each EGU , with the definition submitted to and approved by the permitting authority.

Commenter 20390 states that depending on the APCD installed and permitted, each plant requires review to define startup and shutdown operating conditions and determine if improvements can be made to the existing design to minimize emissions during startup and shutdown.

Commenter 20403 states that the timeframe of each specific step needed for start

- up can be addressed as

part of the Title V permit , where the permittee can provide the State Regulatory Authority the basic procedures with anticipated time frames when startup would end.

Commenter 20393 states that if the EPA decides to establish a bright line test, commenter urge s the EPA to also establish a process in which an electric utility may petition the relevant permitting authority to

establish a unit

- specific startup period on a case

- by

- case basis to ensure the efficient and safe operation

of the APCD

. C ommenter states that this alternative approach, the final MATS regulations would authorize the permitting authority to set a different end of the startup period for an APCD at a particular

coal

- fueled EGU based on specific design and operating parameters at the EGU

.

Com menters 20395, 20396, 20423, 20425, 20428, and 20429 agree with Commenter 20428 ’ s earlier comment that the optimal way for the EPA to address startup is to allow Title V permitting authorities to approve unit

- specific startup plans for each EGU. Commenter 20425 states that startup definition should be determined by the permitting agency on a unit

- by

- unit basis due to the complexity and variances

between different EGU. Commenter 20429 notes that startup periods are dependent on specific EGU designs and speci fic EGU equipment conditions during the startup and maintains that the EPA ’ s generic

“ one size fits all ” approach based on averages of Clean Air Markets Division (CAMD) SO 2 and NOx99

data for hundreds of EGUs is not the best approach to ensure startup ends when air pollution controls may be placed in service and functioning.

Commenters 5833 and 20393 suggest that the EPA adopt a more flexible approach that allows state permitting authorities to define the end of startup for the respective coal fueled EGU ’ s in their jurisdiction on a case

- by

- case basis. Commenter s state that EG U s of different sizes, age, and control device configurations will have different startup times in accordance to each EGU ’ s operational design,

manufacturer ’ s operating specifications, and safety requirements and that these requirements would be best addressed on a case by case basis instead of a blanket definition of the end of startup. Commenter

5833 expresses concern that the EPA is trying to establish a “ time

- certain ” requirement as to when coal fueled EGUs must begin to operate APCDs under a wide range of design parameters and operating

conditions.

Commenter 20390 urged the EPA to be consistent with the established permit requirements for many

sources in its definition of startup an d shutdown. Commenter states that most state and local air permits and many consent decrees for new and existing sources exempt startup and shutdown periods , and that this has been the trend for over 10 years . Commenter states the exemptions typically incl ude a fixed period of time or when the source is able to get APCD in operation and stable. Commenter states the period of time is typically adjusted for type of startup (e.g., hot, cold) due to restrictions on the turbine or boiler in heat ramp and tempera ture.

Commenter 20416 supports Commenter 20396 ’ s comments and agrees with the EPA ’ s recent efforts to establish a safe and effective work practice standard for startup and shutdown periods. Commenter states that startup periods involve the co

- firing of startup and primary fuels prior to engaging APCDs ; therefore, commenter recommends that the EPA allow utilities and delegated permitting authorities the flexibility of establishing unit

- specific practices for SS periods. Commenter states that the EPA should

allow EGU ’ s to implement procedures specific to manufacturer specifications which will ensure optimum and safe operations during periods of startup and shutdown.

Response to Comment 91 : The EPA is finalizing definitions and work practice standards for startup and shutdown periods based on the performance of the best performing sources during those periods. The commenters advocate for site specific work practice plans, but the commenters do not expla in how their proposed approach complies with the requirements of CAA section 112(h). For these reasons, we are not adopting the alternative approaches suggested in these comments. Regarding the co mmenter ’s suggestion to establish a process by which an EGU may petition for the establish ment of a unit

- specific startup period on a case

- by

- case basis to ensure the efficient and safe operation of the APCD, as noted in the response to comments 89 and 90 above, such a process for developing an alternative emissio ns limitation already exists in the Part 63 G eneral P rovisions

.

1.2.8 Petition the Administrator

Summary of Comments Received Following June 25, 2013, Reopening of Public Comment Period

Comment 9 2 : Commenter 20399 appreciates the effort and thoroughness of the EPA ’ s Startup TSD and agrees with the EPA that:100

on average, all types of EGUs...can begin controlling SO 2 and NOx emissions 3 hours or less after reaching 25 percent of nameplate capacity or 6 hours or less following the start of electricity generat ion units can ending the startup exemption 3 hours after a unit reaches 25 percent nameplate capacity or 6 hours after electricity generation.

Commenter 20399 states that the EPA ’ s use of “ on average ” makes it apparent that the EPA recognizes the ability to control SO 2 and NOx within the specified time frame will not apply to every EGU

. Commenter states that accordingly, it request s that the EPA consider amending the definition to enable individual gen erators to petition the Administrator for alternate language that would (1) define startup or shutdown (or both) for a particular source , and (2) provide an alternative compliance pathway for EGUs with unique conditions and operating concerns . Commenter st ates that requesting generators should have the ability to petition the Administrator through development of a n SSM plan according to 40 CFR 63.6(e)(3)(i). Commenter states that this process would give EGU s with control devices that take longer to bring on line the same exemption given EGU s with control devices that can be brought online in less

time.

Commenter 2 0399 states that the EPA ’ s analysis demonstrates that not all APCDs are capable of reaching MATS compliance within the proposed startup window. Com menter states that according to

the EPA ’ s data, some dry FGD EGU s are at twice the SO 2 rate for the HCl surrogate limit as the proposed startup period ends. Commenter states that this rate may not be an issue if a particular EGU has limited startups in a month, but for a cycling EGU this rate could become a considerable compliance

hurdle. Commenter states that the EPA should avoid creating a situation where EGU s would be incented

to stay on

- line out of merit, displacing more effi cient EGU s in order to avoid multiple startups during a

30

- day averaging period.

Response to Comment 92 : The EPA is finalizing definitions and work practice standards for startup and shutdown periods based on the performance of the best performing sources during those periods.

The commenter ’ s characterization of the work practice as an exemption is misplaced as discussed above.

To the extent the commenters ’ units are unable to achieve the final work practice standard, the EGU will

have to be modif

ied and/ or the clean fuel capacity increased, as appropriate. If necessary, the EGU owner or operator may seek an alternative emission limitation consistent with the requirements of 40

CFR 63.6 (g)

.

1.2.9 Flexibility to reflect equipment variability

Summary of Co mments Received Following June 25, 2013, Reopening of Public Comment Period

Comment 9 3 : Commenter 20391 states that in addition to the use of a presumptive definition, the EPA should provide flexibility for compliance during SS through an alternative option that recognizes the diverse operating characteristics and constraints of EGUs. Commenter states that although the concept of a presumptive (or default) definition for the end of startup may serve to provide many EGUs the time needed to achieve operating benchmarks, it may not be readily applicable to all boilers, which have a wide variety of operating modes. Commenter states that the EPA needs to recognize/account for extenuating circumstances when EGU s may fall out of these c ategorical definitions (startup after a major turbine outage, for example) and provide for alternative options. Commenter states that

, therefore, in order to fully recognize the diverse operating characteristics and operational constraints across EGU ’ s101

sub ject to the Utility MATS rule, the EPA should provide flexibility by allowing affected EGU s the following options:

(1) Comply with the work practice standards using a presumptive definition (as a default option). As noted above, the EPA should adopt the d efinition suggested by Commenter 20428 ( i.e

. , “ the 4/12 test ” ); or

(2) Allow EGU s to develop individual SS plans, subject to approval by the appropriate permitting authority, containing site

- specific work practice standards based on manufacturer specifications or based on the “ default ” approach with alternative timeframes. This would allow source operators to determine when startup and shutdown begins based on parameters that are monitored on a given EGU and could be based on requirements in other rules to which the EGU is already subject. These specifications define startup and shutdown using factors more than load, such as the completion of specific procedures and run time.

Commenter 20391 states that this approach would allow affected EGUs the option of following established work practice standards where it is technically feasible, efficient and cost

- effecti ve to do so and would provide for necessary regulatory flexibility for EGUs with site

- specific, unique operating

constraints. Commenter states that this would better assure that each EGU has a workable SS plan that adequately addresses safe operations, protects equipment, minimizes emissions and complies with existing regulations.

Commenter 20390 states that boiler startup and shutdown are critical periods for the operations of

APCDs and it does not belie ve that there is one set rule that can cover all the diverse designed power plants that exist today. Commenter maintains that there are some external issues that it is not sure some people will recognize and alleges that plants try to synch as fast as poss ible based on equipment

constraints. Commenter indicates that d ue to current grid stability, ISOs and transmission management have very strict requirements for ramp rates and synch schedules. Commenter notes that the North American Electric Reliability Cor poration (NERC) and the Federal Energy Regulatory Commission (FERC) are involved to ensure a stable grid, which has been exacerbated by renewable s and low dark spreads.

Commenter 20390 recommends a work practice procedure to determine when startup and s hutdown start the clock for compliance

– each plant is so unique that the process has to be designed for each plant.

Commenter state s that although this makes enforcement more difficult for the EPA , a w ork p ractice process with guidelines can be developed by industry, the EPA , equipment manufacturers, and

environmentalists.

Commenter 20390 states that periods of operation, especially for boiler startup, are characterized by rapid transient changes in flue gas composition, quantity, temperature, and moistu re conditions.

Commenter notes that the EPA training manuals for FF and ESPs indicate improper startup and shutdown can not only damage the equipment but also result in performance degradation. Commenter

states the problems are further aggravated with mult iple APCDs, including SNCR, SCR, dry sorbent injection ( DSI ) , PAC, scrubber (CDS, SDA, wet FGD), ESP, and/or FF. Commenter states that for startup and shutdown, the APCD cannot be viewed as single stand

- alone entities but must be viewed as102

an integrated AP CD system with proper operation dependent on boiler flue gas characteristics and proper operation of the APCD.

Commenter 20390 states that the EPA should establish a database of startup and shutdown emissions to

better characterize this issue. Commenter s tates the database should identify which APCD are in operation during those periods.

Commenter 20409 believes a more appropriate treatment of the startup would recognize the inherent

differences between EGU designs and configurations that result in non

- uniform startup durations.

Commenter states that in fact, even individual EGU startup durations can vary considerably. Therefore, a more optimal approach would recognize the variability in startup durations de fined by individual EGU characteristics, and based EGU startup requirements on equipment manufacturers, vendor specifications,

or similar technical considerations that could be included in a n EGU ’ s Title V permit for example.

Commenter 20397 recommends th e EPA include startup and shutdown definitions that account for

distinctions between both the EGU sources and their APCDs. Commenter states that the definitions of both the source and APCD will dictate when startup and shutdown periods begin and end, such that compliance with the emission limit, which is based on one

- time full load steady

- state condition, better

match conditions used to set the limit. Commenter states although this may make compliance plans for individual EGUs more complicated, owners and o perators will be better able to assure compliance.

Commenter notes the EPA could request monitoring data ( over time )

, because it is collected at all times,

and evaluate whether there are excess emissions and address those conditions on a case

- by

- case basis

.

Comment 9 4 : Commenter 20415 shares the concerns raised by other commenter s and supports defining the end of startup with as much flexibility as possible, to account for the wide range of operational characteristics among boilers, emissions control systems and types and availability of “ clean ” ignition

fuels. Commenter states th at the highest degree of flexibility would be provided by the EPA addressing the wide variations among boilers by revising the startup definition to allow facilities to determine the minimum stable operating load with emissions controls at stable operating condition on a unit

- specific basis and include the minimum stable operating load and the proper procedures to follow during startup

and shutdown in a site

- specific plan. Commenter states that establishment of the minimum stable operating load on a site

- sp ecific basis is analogous to setting other boiler and control device operating parameter limits on a site

- specific basis, which the EPA does routinely in the Boiler MACT rules.

Response to Comments 93 and 94 : The EPA is finalizing definitions and work pra ctice standards for startup and shutdown periods based on the performance of the best performing sources during those periods. The commenters appear to advocate for site specific work practice plans, but the commenters do not explain how their proposed approaches comply with the requirements of CAA section 112 (h). For these reasons, we are not adopting the alternative approaches s uggested in these comments. Furthermore, these and other commenters make assertions that the work practice may not be feasible for all types of units, but they fail to provide sufficient information and data to support their assertions as they relate to an y specific EGU or aspect of the work practice

. The EPA maintains that sources can make any number of physical (e.g.

, modify startup burners or increase clean fuel capacity ) and operational (e.g.

, combusting clean fuels alone for a longer period to warm the EGU or pre

- coat bags to

prevent blinding ) changes at their facilit ies to comply with the final rule.103

As described above and in figures submitted by one commenter, EGUs sharing common stacks do not appear to have trouble meeting the emission limits, especially when the averaging period is considered, during any combination of operating cond itions ( e.g., periods of startup, shutdown, control device startup, control device shutdown, or normal operation )

. 11 Nonetheless, for those operators of EGUs sharing common stacks who choose not to monitor each EGU individually and who choose to seek an

alternative compliance assurance method , the general provisions at 40 CFR 63. 7 (f) (shown below) provide the requirements for such requests.

(f) Use of an alternative test method

— (1) General. Until authorized to use an intermediate or major change or alternative to a test method, the owner or operator of an affected source remains subject to the requirements of this section and the relevant standard. (2) The owner or operator of an affected source required to do performance testing by a relevant standard may use an alternative test method from that specified in the standard provided that the owner or operator

— (i) Notifies the Administrator of his or her intention to u se an alternative test method at least 60 days before the performance test is scheduled to begin; (ii) Uses Method 301 in appendix A of this part to validate the alternative test method. This may include the use of specific procedures of Method 301 if use of such procedures are sufficient to validate the alternative test method; and (iii) Submits the results of the Method 301 validation process along with the notification of intention and the justification for not using the specified test method. The owner or operator may submit the information required in this paragraph well in advance of the deadline specified in paragraph (f)(2)(i) of this section to ensure a timely review by the Administrator in order to meet the performance test date specified in this s ection or the

relevant standard. (3) The Administrator will determine whether the owner or operator’s validation of the proposed alternative test method is adequate and issue an approval or disapproval of the alternative test method. If the owner or operat or intends to demonstrate compliance by using an alternative to any test method specified in the relevant standard, the owner or operator is authorized to conduct the performance test using an alternative test method after the Administrator approves the us e of the alternative method. However, the owner or operator is authorized to conduct the performance test using an alternative method in the absence of notification of approval/disapproval 45 days after submission of the request to use an alternative metho d and the request satisfies the requirements in paragraph (f)(2) of this section. The owner or operator is authorized to conduct the performance test within 60 calendar days after he/she is authorized to demonstrate compliance using an alternative test met hod. Notwithstanding the requirements in the preceding three sentences, the owner or operator may proceed to conduct the performance test as required in this section (without the Administrator’s prior approval of

the site

- specific test plan) if he/she subs equently chooses to use the specified testing and monitoring methods instead of an alternative.

11 See Figures 1, 2, 3, 6, 8, and 9 from Attachment I and the Figure from Attachment V from

Commenter 20428.104

(4) If the Administrator finds reasonable grounds to dispute the results obtained by an alternative test method for the purposes of demonstrating compliance wit h a relevant standard, the Administrator may require the use of a test method specified in a relevant

standard. (5) If the owner or operator uses an alternative test method for an affected source during a required performance test, the owner or operator of such source shall continue to use the alternative test method for subsequent performance tests at that affected source until he or she receives approval from the Administrator to use another test method as allowed under § 63.7(f). (6) Neither the validation and approval process nor the failure to validate an alternative test method shall abrogate the owner or operator’s responsibility to comply with the requirements of this part.

Comment 9 5 : Commenter 20419 states that the definitions of hot, warm , and cold start

- ups must be

made on a unit

- specific basis. Commenter disagrees with the EPA ’ s definitions of hot, warm, and cold

start

- ups in the Startup TSD . Commenter states that these definitions lack support in EPA

- HQ

- OAR

2009

- 0234

- 20380 and do not ac curately describe startups in the real world. Commenter states that the definitions of hot, warm

, and cold startup vary from EGU to EGU . Commenter states that there are numerous factors that affect how quickly a boiler cools off, and utilizing a “ one

- size

- fits

- all ” definition

makes little sense. Commenter states that for example, a boiler in Texas will cool off much more slowly in July than in December, and a boiler in Wisconsin in January will cool off much quicker than a boiler in Texas in January. Commen ter states that the EPA ’ s definitions are clearly inappropriate, as demonstrated by discrepancies in the times for hot, warm, and cold starts of a commenter ’ s member ’ plant in Wisconsin using the plant ’ s definitions, the EPA ’ s definitions in the Startup TSD, and the definitions in the cited docket entry . Commenter concludes hot, warm

, and cold starts must be defined

on a unit

- by

- unit basis based on equipment temperature instead of hours offline.

Response to Comment 95 : The commenter is incorrect in sugge sting that the EPA is required to define the identified terms in a manner consistent with its perspective. More importantly, the EPA maintains that EGUs can start up on clean fuels no matter whether the EGU is cold, warm, or hot, and then bring the EGU up to the necessary temperature before beginning electricity generation and combustion of coal

or oil. T he commenter s do not provide information that causes us to question this conclusion for the vast majority of EGUs as currently constructed, and we further believe that most of the remaining EGU s will be able to make changes at the facility that will allow the EGUs to comply with the final rule (e.g.

, increasing clean fuel capacity and/or reconfiguring the ducting or clean fuel burners to allow the EGU s to be properly warmed on clean fuels alone).

Comment 9 6 : Commenter 20423 states that startup periods can vary by season and ambient temperature. Comme nter states that, for example, startup in the winter in North Dakota when temperatures can be lower than

- 20 ° F can take longer for equipment, including the PM control systems, to heat up to above acid dew point.

Commenter 20423 states that, as noted by t he EPA , the normal progress of startup activities may involve the cessation of fuel combustion following the initial combustion of ignition or startup fuel. Commenter

states that these interruptions may include planned multiple stop/starts of the combustion process, and105

unplanned but nevertheless necessary cessations in the same combustion process. Commenter states that

in its experience these interruptions range in duration from a few hours to multiple days.

Commenter 20423 states that the EPA Startup TSD focuses on “ normal, ” or average, startups.
Commenter states that the analysis fails to capture the unpredictability and inherent variability in how any given EGU starts up. Commenter states that for any owner/operator, the goal of startup is to bring a n EGU up to steady

- state operation as quickly as can be safely done so that the EGU efficiently generates electricity and controls emissions as soon as possible. Commenter states that startups can vary for each given EGU based on factors inclu ding the length of time the EGU has been down, whether there are equipment malfunctions, etc. Commenter believes characterization of startups as “ normal ” suggests that any given EGU ’ s startup is a predictable and consistent event, which is not the case.

R esponse to Comment 96 : Responses to these comments can be found above in response to comment

95. In addition, we do not agree with commenter ’ s suggest ion that the EPA must account for the variability of all EGUs. For example, when defining the end of startup, the EPA looked at the performance of the best performing sources using the metric we developed . Because we have data on all startup events at the EGU s with the relevant data , we maintain that it would arguably be reasonable to include no additional variability, but, to ensure a reasonable time for the end of startup in the final rule,

we also determined it was reasonable to round the average time up to 4 hours. We looked at all startups during a 2

- year period, including those that were subsequently interrupted ( see Revised TSD).

Comment 9 7 : Commenters 5834 and 5840 state that during startup the work practice standards must allow for a phasing in of the operation of ESPs, as well as other APCD, consistent with safe and technically feasible operations. Commenter 5834 explains that ACI controls for Hg are not effective

until ESPs are engaged. Commenter 5840 states that site specific work plans can incorporate procedures that identify the points when specific APCDs are placed in service. Commenter notes that these site

specific operating procedures could include compliance wit h boiler and APCD manufacturer ’ s operating procedures or the EGU ’ s written Standard Operating Procedures manual during startup and shutdown; they could also include requiring operation in a manner consistent with those procedures to minimize

emissions incl uding starting APCDs as soon as practical. Commenter maintains that such standards could include a reasonable period of time allowed for a startup considering the limitations inherent in starting and balancing operational parameters associated with complex equipment.

Response to Comment 97 : The EPA is finalizing definitions and work practice standards for startup and shutdown periods based on the performance of the best performing sources during those periods. The commenters advocate for site specific work practice plans, but the commenters do not explain how their proposed approach complies with the requirements of CAA section 112(h). For these reasons, we are not adopting the alternative approaches suggested in these comments. Regarding the co mmenter’s

su ggestion to establish a process by which an electric utility may petition for the establish ment of a unit

specific startup period on a case

- by

- case basis to ensure the efficient and safe operation of the APCD, as noted in the response to comments 89 and 90 above, such a process for developing an alternative emissions limitation already exists in the Pa rt 63 G eneral P rovisions . We address the operation of ESPs

elsewhere in this document.

Comment 98 : Commenter 5840 states that its coal fleet is comprised of 11 supercritical and two FBC EGUs. These EGUs typically continue to burn startup fuel after beginn ing to generate electricity for heat106

production and flame stability purposes. Commenter maintains that emission controls may or may not be in service at this time due to good operational practices, manufacturer recommendations, permit conditions, and/or sa fety considerations; those APCDs that are engaged are not operating at design conditions until control equipment

- specific temperature ranges are achieved. Commenter alleges that supercritical EGUs are unstable when operating in subcritical mode and owner/o perators are, therefore, incented to safely move the EGU to supercritical operation as quickly as possible; operators are also incentivized to place APCD in service as quickly and safely as possible.

Response to Comment 98 : The EPA acknowledges that some APCDs may not be operating at design conditions until after the time defined to be the end of startup. However, as noted elsewhere in this document, the EPA believes that its analysis of the startup practices of the top perfo rming 12 percent of EGUs, which included all types of EGUs, and its final definition of “startup” adequately balances

commenter s’ concerns with the requirements of CAA section 112. The EPA notes that the goal of the analysis was to identify the approximate time it took, on average, to initiate operation of APCDs by the top performing 12 percent of EGUs for the purpose of defining the end of startup . The goal was not to seek the time it took for APCDs at all EGUs to become fully operational , as that would no t be consistent with CAA section 112(h)

.

2.0 CLEAN FUELS

Summary of Comments Received Following November 30, 2012, Proposal

Comment 99 : Commenter 2 028 8 agreed that companies should use clean fuels for startup and shutdown to the extent possible and provided those fuels are available at that site.

Response to Comment 99 : Th is comment requires no response

.

Comment 10 0 : Commenter 2 030 5 asks that the EPA clarify that it is not proposing changes to the requirement that sources burn clean fuels during st artup and shutdown. Commenter notes that in the Reconsideration, the EPA is “ proposing to require EGU source owners and operators, when firing coal

, solid oil derived fuel, or residual oil in the EGU during startup or 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

... ” (emphasis added). Commenter observes that this reference to venting

emissions when “ firing coal ” during startup o r shutdown suggests that EGUs can burn coal during startup and shutdown.

Commenter 2 030 5 notes that industry is required to provide emission estimates during startup and

shutdown in its SSM permit applications and that data show that requiring EGUs to bu rn clean fuels during periods of startup and shutdown would result in significant emission reductions. Commenter provides copies of permit applications with startup and shutdown emissions. Commenter notes that the permit applicants projected emissions base d on assumptions about coal feed rate during startup and shutdown, and applying AP 42 factors to estimate emissions during uncontrolled combustion of coal.

Commenter states that these permit applications support the use of clean fuels during startup and

sh utdown.107

Comment 10 1 : C ommenters 2 0246, 20248, 20252, 20254, 20269, 20272, 20283, 20287, 20303, and

2032 1 state that they are not able to complete startup on clean fuels alone.

Commenter 2 024 6 states that in some cases, large boilers may not have sufficient clean fuel firing capacity to fully meet boiler start

- up needs.

Commenter 2 024 8 states that the proposed changes to the existing requirements are problematic for

EGU s that do not have the physical capability or adequate fuel supply to complete “ startup ” as defined by the EPA solely on a clean fuel and that EGUs that need to add coal or heavy oil with “ clean fuel ” in order to generate electricity for sale or make useful thermal energy simply will not be able to comply with the requirement to only use clean fuels during startup. Commenter states that t o satisfy this arbitrary work practice standard, many EGUs would need to modify their oil burner configurations, install additional piping and pumps, and/or increase storage capacity for clean fuels. Commenter states
i n light of the relatively small differences between HAP emissions related to heavy oil when compared

to emissions related to clean fuel, these EGUs should not be required to absorb the additional capital expense to modify its SS process and additional operating expenses for startup , and m odification may not always be economically justifiable and/or possible

. Commenter asks that the EPA clarify that it did not intend to subject limited use liquid oil

- fired EGUs to the startup and shutdown work practice standards, because these EGU s are not subject to numerical standards and therefore do not require a

defined emission limit exemption during these periods of operation. Commenter suggests that the EPA maintain the clean fuel requirement in the finalized MATS rule with modification to reflect the revised

list of clean fuels. Commenter recommends that the existing Table 3 (FR 77 9493) be revised as follows:

“ You must operate all CMS during startup. Startup means either the first

- ever firing of fuel in a boiler for the purpose of producing electricity, or the firing of fuel in a boiler

after a shu tdown event for any purpose. Startup ends when any of the steam from the boiler is used to generate electricity for sale over the grid or for any other purpose (including on site use). For startup of a unit, you must use clean fuels, either natural gas

or distillate or a combination of clean fuels for ignition

. ”

Commenter 2 024 8 states that, alternatively, if the EPA requires that EGUs only use clean fuels for the entire startup process , the EPA should revise the definition of “ startup ” to provide the option for EGUs to voluntarily end the startup emissions exemption period. Commenter states that t his option would allow a source to end its startup when a fuel not meeting the “ clean fuel ” definition is initially

introduced. Commenter reco mmends specific revised definitional language for “ startup. ”

Commenter 2 025 4 indicates that the proposed work practice requirement that bag houses and some other

APCDs must be in use as soon as any coal is burned in the boiler is neither realistic nor consistent with equipment manufacturers ’ specified operating procedures. Commenter notes that this is especially the

case for many older or smaller coal

- fir ed boilers that are not able to achieve the correct tempera ture for the operation of a bag house whil e using the igniter to burn a “ clean fuel ” ( e.g., natural gas) as is required

under the proposed MATS startup work practices standards. Commenter states that the compliance challenges stem from the fact that in many instances the igniter offers only a low heating value, especially on older and smaller EGUs , and therefore it cannot serve a heating function well over long periods of time; i t would require a large number of additional hours in order to reach the proper startup temperatures if an EGU is solely using the igniter and a clean fuel. In the case of two of commenter ’ s108

coal

- fired EGUs , the existing igniters used for startup of the EGUs are not of sufficient capacity to bring the baghouse to recommended operating temperature. In addition, commenter states that it is impractical to require that the igniter fuel, here natural gas, be the only fuel used to get to boiler up to the correct

temperature as t his would require a large amount of natural gas, and there are serious natural gas supply

concerns fo r these EGUs because the natural gas pipeline capacity has limited supply. Commenter indicates that the EPA suggests in technical guidance that there are no constraints on running a boiler on clean fuels for a longer period of time in order to reach the co rrect temperatures, and therefore that sources will be able to delay the use of baghouses until that time. However, commenter believes it is not technically feasible to use a small igniter burning a limited supply of natural gas for a long enough period to have the boiler reach the correct temperature without burning any coal.

Commenter 2 026 9 states that FF are similarly impacted by flue gas temperature and, as a result, certain designs cannot be operated until startup is complete. One of commenter ’ s membe rs owns a coal

- fired EGU that operates a baghouse for PM control during periods of normal operation. The flue gas must reach a certain minimum temperature before the baghouse is put into service to prevent acid corrosion from damaging the baghouse and resulting in its failure. Commenter notes that t his facili ty starts up on natural gas, but lacks sufficient natural gas capacity for the EGU to complete the startup process; d ue to this limitation, coal must be fired about 30 minutes into the startup process but before startup is complete, allowing the flue gas t o reach the necessary temperature for the operation of the baghouse.

Commenter 2 027 2 states that many utility boilers will simply not be able to generate sufficient heat to

achieve the manufacturer ’ s recommended minimum temperature levels for the ESP whil e burning only oil or gas startup fuels. Commenter notes that one reason for this is that the oil or gas igniters for coal

fired EGUs were never designed to preheat the ESP plates without the combustion of coal. Commenter

indicates that t o put it in other words, these boilers

– which tend to be the older design coal

- fired EGUs

– are equipped with igniters that were meant solely to light the fuel, not to provide sufficient heat to warm up the ESP hardware to the manufacturer ’ s specified temperature levels. C ommenter alleges that

to the EPA ’ s claims, these EGUs cannot generate adequate heat to energize the ESP even if they combust only oil or gas startup fuel for an extended period of time.

Commenter 2 028 3 states that many coal

- fueled EGUs must combust coal a long with oil or gas during startup in order for the ESP to achieve adequate temperatures for the proper and safe operation of the control equipment. Commenter notes that without the combustion of coal, many utility boilers will simply not be able to generate sufficient heat to achieve the manufacturer ’ s recommended minimum temperature levels for the ESP while burning only oil or gas startup fuels.

Commenter 2 028 7 st ates that the proposed revisions appear to require clean fuels not only for ignition (as the final MATS rule required) but throughout the startup period. Commenter notes that, like many other facilities, it uses distillate fuel exclusively to ignite its th ree boilers and thereafter to supplement its primary fuel until startup is complete. Commenter ’ s s tation is not designed to exclusively fire distillate to the point that the EGU s produce electricity or useful thermal energy, which is how the EPA proposes to define the end of “ startup. ” Commenter notes that it must introduce coal to complete startup and to increase flue gas temperatures to the level at which its ACPDs are effective. Commenter states that the

cost to retrofit the EGUs to enable the m fire exclusively clean fuel through startup would be substantial and far outweigh any marginal benefit

. Commenter states that the best approach and the only one supported by the record is for the EPA to clarify in Table 3 in the final rule that clean fue ls need only be109

used for ignition of an EGU and that other fuels can be blended into the fuel mix after ignition but before the end of startup without violating the work practice standards

.

Commenter 2 028 7 states that if the EPA requires existing EGUs to use clean fuels beyond ignition, it

recommend s that the EPA not mandate the exclusive use but rather the use permissible with the facility ’ s existing fuel capabilities. Alternatively, commenter suggests the EPA could revise the part of

the definition of startup that defines the end of startup to include “ ...and 18 CFR 292.202(c)), or when fuels other than clean fuels are first used, whichever is earlier. ” This would allow facilities to avoid being in violation of the rule ’ s work practice standards simply because they have insufficient clean fuel firing capacity.

Commenter 2 030 3 states that the design of its EGU does not include large oil guns but is designed with

oil igniters (firing #2 fuel oil) that do not permit the EGU to be synchronized (generate ele ctricity) prior to starting a coal pulverizer.

Commenter 2 032 1 states that the proposed work practice standard to combust clean fuels during periods of startup and shutdown is not feasible for commenter ’ s EGUs. Commenter explains that because of the size of the natural gas igniters , natural gas can produce enough steam to start or “ roll ” the turbine in its

EGU s, but coal

- firing must begin immediately because large steam generators are unstable at such very

low loads. Commenter sta tes that the EGU s would require reconfigured igniters , piping and valves, and additional natural gas transmission capacity. Commenter states that these expensive changes would have little environmental benefit, as the added natural gas firing would only be used for a short time by the

EGU s, very few times during a typical year.

Commenter 2 025 2 states that the EPA should clarify in the regulation that the clean fuel required for startup does not foreclose the burning of solid fuel during startup, as long as emission controls are engaged as set forth in the work practice standard. Commenter notes that the preamble mentions firing coal, solid oil

- derived fuel, or residual oil in the EGU during startup or shutdown, but the regulatory text

does not reflect that understanding. Commenter states that it is not operationally possible for coal

- fired stoker boilers and possibly other solid fuel boilers to burn only clean fuels during the entire startup period. Commenter states that its coal

- fired stoker boiler transitions from offline to fully operational, using clean fuel initially to ignite some coal and then slowly the remaining coal is ignited and builds enough heat for the boiler to be fully operational. Commenter asks for clarific ation to recognize that a transition to solid fuel is an integral and essential step in the startup process and suggests that following alternative language in Table 3 of the rule:

To initiate For startup of an EGU, you must use one or a combination of th e following clean fuels: natural gas, synthetic natural gas, propane, distillate oil, syngas, and ultra

- low

sulfur diesel.

Commenter 204 37 states that “[c]lean fuels” are used for ignition during startup and flame stabilization during shutdown. For most E GUs, primary fuel(s) also must be fired for some period of time during startup because the heat input produced from the ignition burners is not sufficient to achieve the temperatures necessary to bring some control devices on

- line and that during shutdown, most units employ non

- primary fuel, which can be “ clean fuel, ” to keep the flame stable as primary fuel is phased out during the shutdown process; however, during that process, some primary fuel may continue to be110

combusted even after the EGU no longer ge nerates electrical energy or makes useful thermal energy. Commenter expresses concern that other proposed language does not clearly manifest recognition that EGUs will fire primary fuel(s) while in startup or shutdown, and will use “clean fuels” only for i gnition during startup and for flame stabilization during shutdown. As such, commenter recommends revisions

as follows to Table 3 of subpart UUUUU (as proposed in November 2012, see 77 FR 71342, second and third lines of item 3) and to 40 CFR 63.10011(f) (as proposed in November 2012, see 77 FR 71338) to

reflect that intent:

Prior to firing coal. residual oil, or solid oil

- derived fuel during startup of an EGU, you must use one or a combination of the following clean fuels: natural gas, synthetic natural gas, propane, distillate oil, syngas, an d ultra

- low sulfur diesel, and ot her clean fuels as approved by the permitting authority for ignition.

(f) You must use for ignition during startup and flame stabilization during shutdown any one or combination of the following clean fuels: natural gas, synthetic natural gas, propane, di stillate oil, synthesis gas (syngas), and ultra

- low sulfur diesel (ULSD), and other clean fuels as approved by the permitting authority.

Response to Comment s 10 0 and 10 1 : The final rule retains the requirement that EGUs begin startup on

startup (“clean”) fuel and maximize the use of clean fuels until startup has ended. PM control s must be operational within 1 hour of coal combustion

. EGUs that are currently unable to come up to the requisite

temperature due to a lack of clean fuel capacity will be required to increase their clean fuel capacity to the extent necessary to comply with the work practice standard. After the EGU begins firing coal

, residual oil, or solid oil

- derived fuel , the final rule requires the EGU to continue to maximize the use of

the clea n fuels defined in 40 CFR 63.10042 and the EGU must engage its PM control device within 1

hour of when the EGU starts firing coal, residual oil, or solid oil

- derived fuel . Thereafter, the EGUs

must comply with the MATS numerical emission limits within 4 hours of start of electricity generation

.

As noted elsewhere, the EPA believes that its analysis of the startup practices of the top performing EGUs and its final definition of “startup” adequately balances commenter s’ concerns with the requirements of CA A section 112. The EPA notes that the goal of the analysis was to identify the approximate time it took, on average, to initiate operation of APCDs by the top performing 12 percent of

EGUs to determine a reasonable time after electricity generation to defi ne the end of startup . The goal was not to seek the time it took for APCDs at all EGUs to become fully operational , and sources are not in fact required to engage their non

- PM controls within 4 hours unless those controls are necessary to comply with any a pplicable requirement s, including the MATS requirements

. The EPA has determined that it will be possible for sources to accurately measure HAP emissions using CEMS at this time, and, for that reason, the work practice must end and the numerical emission limits must apply consistent with

CAA section s 112(d) and 112(h).

As noted in the final preamble (77 FR 9401), “Liquid oil

- fired EGUs subject to this [limited use liquid

oil

- fired] subcategory would b e required to conduct the same initial and periodic tune

- up as all other affected units, but would have no other emission limit or work practice requirements.” Thus, the startup provisions do not apply to EGUs in this subcategory.

We have addressed specif ic concerns related to PM control equipment in section 3.0 of this document.111

The EPA also received comments related to the safety issues that must be considered during startup of PM controls (e.g., CO buildup, fabric blinding). We note that these concerns are generally associated with temperature issues that we believe can be remedied through an increase in clean fuel capacity or

other modifications to the clean fuel burners or other boiler system modifications. Comments suggest

that the concerns about saf ety can be redress ed with changes to the system that the commenters allege are not worth it. We note that NESHAP standards are designed to force the poorer performing sources to adjust their facilities to meet the HAP emissions levels of the best performing sources, and that mandate almost always come s at a cost to some sources in the category. However , we recognize that there may be

very limited circumstances that compel some alternative approach for a specific EGU. Sources that can

demonstrate th at the ir EGU has a documented manufacturer

- identified safety issue that cannot be resolved should seek an alternative compliance method consistent with 40 CFR 63.6(g) . In its request

for the case

- by

- case determination, the EGU must provide documentation th at demonstrates that it is not technically feasible to bring the PM control device on line safely using clean fuels alone

, and explains what other measure the source will take to ensure comparable HAP emissions to those required under the final work practi ce.

Summary of Comments Received Following June 25, 2013, Reopening of Public Comment Period

2. 1 Oppose

Comment 10 2 : Commenter 20422 opposed eliminating the current requirement that only clean fuels be burned during startup. Commenter states the EPA should set performance standards for clean fuels to

assure that alternatives are as clean as NG or distillate. Commenter states the EPA should define a set of performance standards for clean fuels, based on the properties that produce the lowest levels of toxic pollutants regulated under the rule during startup or shutdown. Commenter notes this approach is protective and would flexible enough to avoid endless review of petitions to add new substances to the

list. Commenter suggests the EPA should limit the S content, Cl content, density viscosity, boil ( ing ) point range, and distillation temperatures (D 10 , D 50 , and D 90 , representing temperature at which 10 percent, 50 percent, and 90 percent of fuel will burn off).

Commenter 20436 states that the final MATS rule required EGUs to use natural gas, distillate, or low sulfur diesel fuels to ignite boilers and warm up pollution control equipment prior to electricity generation. Commenter opposes any weakening of these lim itations (e.g., by requiring that EGUs only “maximize” use of clean fuels prior to generation). Commenter further alleges that the term “maximize” is vague and unenforceable and would create an unlawful new loophole and would not discharge EPA’s obligation to be consistent with CAA section 112(d). Commenter notes that, at a minimum, the EPA must require that the emission limits take effect as soon as coal combustion begins, whether or not electricity is generated.

Response to Comment 102 : The EPA believes that its final definition of “clean fuels” includes fuels that all have inherently low levels of HAP. The EPA does not believe that adding performance standards

as commenter s suggest would be practical nor is it necessary

.

As in the final rule, the EPA is requiring EGUs to maximize the use of clean fuels at the beginning of startup and to continue to maximize the use of clean fuels for as long as necessary to bring the EGU to112

the temperature required to engage and operate the PM controls within one h our of coal, residual oil, or

solid

- oil derived fuel being charged to the unit s

. This requirement is intended to ensure that PM and the

attendant HAP reductions will occur as quickly as possible after primary fuel combustion begins. In addition, throughout the remainder of the startup period, EGUs are required to continue to maximize the use of the clean fuels. We consider this language to mean that EGUs will continue to use the maximum amount of clean fuels possible throughout the startup period to minimiz e HAP emissions

.

2. 2 Co

- firing with other fuels

Comment 10 3 : Commenter 20403 states that the EPA needs to acknowledge in the rule that as part of

start

- up a coal refuse

- fired CFB will initiate startup using clean fuel and slowly transition from just firing with clean fuel to co

- firing with clean fuel and coal refuse (along with limestone and/or ash) with the amount of clean fuel being reduced until the bed is stabilized using ever increasing amounts of fuel,

limestone and ash. Commenter states that once the bed is stabilized the use of clean fuel is stopped.

Response: The CFB will be required to maintain the maximum clean fuel input possible throughout the startup period as it gradually increases its coal refuse and other inputs. See response to previous

comments in section 2.0 above

.

Comment 10 4 : Commenter 20393 disag reed with the statement that no technical barriers exist to burning clean fuels for longer portions of startup or shutdown periods. C ommenter states that with regard to particularly older and smaller EGU s, barriers do exist and that it would take too long to reach the proper combustion temperatures solely on clean fuels. C ommenter states that this is due to the design of the igniters which were not designed to provide temperature regulation.

Commenter 20391 supports expanding the definition of “ clean fuels ” in the context of startup, shutdown periods. Commenter states that however, the EPA should limit the requirement to use clean fuels during startup exclusively to ignition. Commenter generally supports the proposed expansion of the clean fuels

list. Comme nter states that the EPA should provide greater flexibility and clarity in the “ clean fuels ” definition by adding the language “ and other clean fuels as approved by the permitting authority. ”

Commenter 20391 states that the proposed reconsideration rule appears to require the use of clean fuels throughout the startup process, whereas the original final rule required use of clean fuels only for ignition. Commenter states that the EPA provides very limited explanation for the proposed change.

Commenter states that other than asserting that no technical barriers exist to burning clean fuels for longer portions of startup or shutdown and that, if needed, a n EGU could burn clean fuels until the appropriate flue gas condit ions are achieved to engage APCDs

. ( EPA

- HQ

- OAR

- 2009

- 0234

- 20224. )

Commenter states that this requirement, however, would be problematic for EGU s that do not have the physical capability or adequate fuel supply to complete “ startup ” as defined by the EPA sol ely on a

clean fuel. Commenter states that that to satisfy the work practice standards, some EGU s would need to modify their oil burner configurations, install additional piping and pumps, and/or increase storage capacity for clean fuels. Commenter states that in addition, firing clean fuels throughout startup will not allow the necessary temperatures for pollution control equipment to operate sufficiently and to its full potential. Commenter states that producing the initial flame in a PC boiler with oil w orks well, except the operating temperature of the SCR is not reached until 80 percent of coal mills are in service.

Commenter states that having clean fuel capacity to reach this operating point would require significant113

changes to the boiler and would cr eate problems for the add

- on air pollution control, such as ESP ’ s (e.g., fouling of surfaces that would prevent proper PM collection and can take days to restore proper operation), and changing the chemistry in the FGD that would delay proper operation. Co mmenter states
that in a CFB EGU , if gas was required to be used for startup, there could be significant increases in NOx, SO 2 and CO emissions because gas does not have sufficient radiant heat energy to heat the bed of ash up to temperature in a reasonabl e time to allow the calcification process to function to begin injecting coal and limestone.

Commenter 20391 states that to the extent the EPA extends the clean fuels requirement beyond ignition, it should provide affected sources the opportunity to pursu e alternatives with their permitting agency if burner configuration modifications or increased storage capacity that may be necessary to accommodate clean fuels are physically or economically prohibitive. Commenter states that clean fuels can also be

scien tifically not appropriate (e.g., gas fuel does not have the same radiant heat transfer properties as oil) and the use of gas may increase air emissions because of delays in heating up surfaces to allow transferring to the primary fuel.

Response to Comment 104 : The EPA does not agree that the February 2012 final MATS rule only required the use of clean fuels for ignition. The work practice in the final rule required the use of only

clean fuels until EGUs starting generating electricity, at which point the sources would be required to comply with the numerical emission limits. The record indicated that EGU s generally begin combust ing the primary fuel at approximately the same time as they begin generating electricity. As for controls, we

stated in the final rule that PM and other controls had to be engaged at that time a s necessary for the sources to comply with the numerical standards . As many industry commenters note, many PM controls cannot be engaged for some time if it is a cold or warm startup . Logically this would mean that EGUs would be required to combust only clean fuels for extended periods of time for cold and warm startups. Furthermore, the final MATS rule defined the end of startup as the first generation of electricity or thermal energ y for sale or on site use. Again, many industry commenters indicated that they begin generating electricity simultaneously or soon after adding the primary fuel to the EGU. Because sources would be required to comply with the numerical standards at the tim e of electricity generation, which is earlier than under the alternative set forth in this final rule, we believe that clean fuel capacity increases

and other modifications (e.g.

, to burners ) would have been necessary for many EGUs t o allow the m to burn clean fuel alone for a longer period under the final rule definition for sources to be sure they would comply with the numerical standards once generation occurred.

The EPA believes that its analysis of the startup practices of the top performing 12 percent of EGUs, which included all types of EGUs, its final definition of “startup,” and its final definition of “clean fuels” adequately balance commenter s’ concerns with the requirements of CAA section 112. The EPA

continues to believe that commenters’ “technical barriers” associated with using more clean fuel during

startup can be resolved at almost all, if not all, EGUs

. Sources will need to determine the appropriate approach to comply with the final rule consistent with the individual EGU ’ s needs in the same manner owners and operators evaluate their sources when determining how to comply with numerical limits.

The EPA’s final rule is not flawed if it requires sources to make investments that will reduce HAP

emissions

, as the commenters imp ly

.

Comment 10 5 : Commenter 20415 states that th e commenter s submitted data and information showing that it is common and necessary for boilers to begin to fire primary fuel in addition to the startup fuel114

before certain APCDs are engaged. Commenter states that this is most often due to the inability of the boiler igniters to bring the boiler up to temperatures high enough to operate APCDs because igniters and their associated fuel supply systems are typically of very limited heat input capability. Co mmenter states that in addition to these operational limitations, worker safety concerns also require that certain operating conditions be met prior to engaging APCDs. Commenter states that a typical coal

- fired EGU may use clean fuel initially to ignite so me coal and then slowly build enough heat for the boiler to be fully operational. Commenter believes the rule should clearly recognize that a transition to base or primary fuels that are not defined as clean (e.g., coal or biomass) is an integral and essen tial step in the startup process and must be allowed regardless of whether any steam or heat output is generated.

Commenter 20415 states that the EPA has provided additional clarity of this issue in the Boiler MACT Final Reconsideration Rule, which commen ter recommends the EPA adapt to the MATS rule as well, because some EGUs may utilize these types of startup fuels. Commenter states that in the Boiler MACT rule, the EPA expressly recognizes the following as clean fuels for use during startup: natural gas, synthetic natural gas, propane, distillate oil, syngas, ULSD , fuel oil

- soaked rags, kerosene, hydrogen, paper, cardboard, refinery gas, and liquefied petroleum gas. Commenter states that this list is more

inclusive than the MATS rule definition and reflec ts the reality that during startup, boilers are designed for certain startup fuels and only certain fuels may be available. Commenter states that it is important to note, however, a major deficiency of the MATS and Final IB MACT rule definitions of startup is that neither expressly recognizes that many EGU s must co

- fire and then switch over entirely to primary fuels in addition to these clean fuels during the startup period. Commenter states that therefore, an expanded list of clean fuels must be coupled wi th a workable definition of startup, which includes switching over to the primary fuel during the startup period, to rationally reflect the realities of boiler operations.

Commenter 20393 disagreed with the EPA and states that EGUs cannot generate adequate heat to energize the ESP even if they combust only oil or gas startup fuel for an extended period of time and

states that the current work practice requirement is not feas ible for many coal

- fueled EGUs equipped

with ESPs. C ommenter states that many coal

- fueled EGUs must combust coal along with oil or gas during startup in order for the ESP to achieve adequate temperatures for the proper and safe operation of the control equ ipment. Commenter states that without the combustion of coal, many utility boilers will not be able to generate sufficient heat to achieve the manufacturer ’ s recommended minimum temperature levels for the ESP while burning only oil or gas startup fuels. C ommenter states that older design coal

- fired EGUs have oil or gas igniters that were never designed to preheat the ESP plates without the combustion of coal and will be unable to provide sufficient heat to warm up the ESP

hardware to the manufacturer ’ s spe cified temperature levels. Commenter indicated that operational manuals for five different boiler/precipitators used in commenter ’ s facilities require minimum ESP inlet temperatures of between 200 and 275 °F prior to energizing the ESP.

Commenter 20421 as ks that co

- firing of coal be permitted during startup, and asks for language to clarify that co

- firing coal during the startup period is permitted by the regulation. C ommenter states that

most coal

- fired EGUs were not designed nor do they have enough capac ity in their ignition/startup burners to achieve permissive temperatures to operate their APCDs without the use of coal in addition to the use of clean fuels during startup. Commenter maintains that in order for some coal

- fired EGUs to use only clean fuels during startup, significant capital investment in redesign and retrofitting facilities would be required, at a prohibitively high cost that the EPA has not measured or evaluated in developing the rule (presupposing that there is a sufficient supply of cle an fuel available to the EGU, which is not likely115

in many cases). C ommenter notes that the plain language of Reconsideration Rule contemplates the co

firing of startup and primary fuels during startup. C ommenter recommends the following text be

included in Table 3:

Coal

- fired EGUs are permitted to co

- fire coal with their clean fuels when needed to complete the startup phase of operation.

Commenter 20430 states that that its San Miguel EGU is unable to meet the criteria of completing startup as originally proposed using only “ clean fuel

. ” Commenter states that San Miguel requires co

firing of clean fuel with the primary fuel in order to reach a proper temperature to produce electric

generat ion. Commenter states that San Miguel ’ s steam generator design does not include large oil guns but is designed with oil igniters (firing #2 fuel oil) that do not permit the EGU to be synchronized (generate electricity) or safely initiate APCDs prior to fir ing primary fuel. Commenter requests the ability to co

- fire startup fuel and primary fuel through initial synchronization.

Commenter 20408 states that the wording of the proposed rule seems to preclude the use of the primary fuel ( e.g., coal, residual oil ) during startup. Commenter alleges that the EPA apparently does not recognize that the generation of electricity begins typically while both the startup fuel and primary fuel are still being fired together. Commenter provides an informative example of a s taged startup with a cyclone boiler EGU. Typically cyclone boilers have 10

- 20 individual cyclones. A typical startup procedure for a cyclone boiler is to warm 1

- 3 cyclones using startup fuel and as these cyclones come up to temperature the operator begins feeding the primary fuel (e.g., coal). After these initial cyclones are on line and using coal the EGU will typically begin generating electricity rather than waste this energy in the steam cycle. The remaining cyclones are brought on line in the same mann er incrementally. The boiler is thus not fully finished with startup until all available cyclones are online. C ommenter states that

the EPA needs to revise the statement in 40 CFR 63.10011(f) clarifying and recognizing that the primary

fuel can be burned d uring startup.

Response to Comment 105 : The EPA has acknowledged elsewhere in this document that it is aware that both clean fuels and the primary fuel may need to be used together during startup and that such acknowledgement was in both the final rule and proposed reconsideration . The EPA has also noted that

it believe s almost all , if not all, the identified technical barriers to increasing the amount of clean fuel can be addressed through an increase in clean fuel capacity and/or other modifications to the facility or operational practices

. As stated above, the EPA does not believe a work practice standard should be set

at the level all sources can meet unless all sources are virtually identical, as that is not consistent with CAA section 112(h).

Comme nt 10 6 : Commenter 20391 states that the EPA should not apply the clean fuel requirement for

oil

- fired EGUs that fall under the limited use liquid oil

- fired subcategory of the MATS rule. Commenter

states that the limited use EGU s will not be subject to emissions limits if a particular EGU is under the 8 percent annual capacity factor limit. Commenter states that these EGU s should not be required to absorb the additional capital expense to modify their SS process and additional op erating expenses for startup given their limited use and the limited environmental benefit that would be realized. Commenter states
that MATS should be revised to reflect that these limited

- use EGU s are only required to perform the

boiler tune

- up work prac tice standards and keep records to demonstrate compliance with the 8 percent annual capacity factor limit.116

Response to Comment 106 : As noted in the final preamble (77 FR 9401), “Liquid oil

- fired EGUs subject to this [limited use liquid oil

- fired] subcateg ory would be required to conduct the same initial and periodic tune

- up as all other affected units, but would have no other emission limit or work practice requirements.” Thus, we do not interpret the rule to apply the startup (or shutdown) provisions to E GUs in this subcategory. We meant this quoted language to indicate that to be our intent but in light of the comment, we have added exclusionary language to Table 3 of subpart UUUUU for clarification.

Comment 10 7 : Commenter 20407 states that that the definition of fuel that can be used during startup period should be removed from the rule. Commenter supports the EPA ’ s recognition in the

reconsideration that the EGU ’ s primary fuel, in most cases, must be utilized during the startup period to complete the startup process. Commenter states that based on its experience, the temperatures needed to safely start various emission control equipment cannot be achieved without introducing the primary fuel

to the EGU . Commenter states that the startu p and shutdown plan should set forth the procedures, including fuels used, to startup a n EGU as expeditiously as possible. Commenter states that at a minimum, the EPA should revise the work practice standard to clearly indicate that the primary fuel for

th e EGU can be used during the startup period.

Commenter 20390 states it may not be possible at every plant to bring the system up to temperature with clean burning startup fuel and bring APCD into service prior to firing coal. Commenter states that at

some plants startup fuel is co

- fired until half load and at other facilities startup fuel is co

- fired until two

thirds load, and indicates the capacity for auxiliary or startup fuel of each plant is different, noting that some plants burn startup fuel to 10 pe rcent of design heat input whereas others can burn auxiliary fuel up to full load.

Commenters 20417 and 20419 also urge the EPA to consider that defining the end of startup based on when coal, residual oil, or solid oil

- derived fossil fuels are first fir ed is impracticable at certain plants. For example, Commenter 20419 indicates that one member owns a coal

- fired EGU that uses natural gas to ignite the coal, but lacks sufficient natural gas capacity to the plant to allow the EGU to complete the

startup pr ocess. Due to this supply limitation, Commenter 20419 alleges that coal must be fired within the first 30 minutes of the startup process but the plant cannot begin to generate electricity for approximately 7 hours. Commenter 20419 notes that the EGU ’ s ESPs are started when the switch to coal is made and the ESPs are shut off and the baghouse is put in service when the flue gas is up to proper baghouse operating temperatures that are above the moisture dew point (based on further analysis, commenter now believes that that baghouse operations are constrained by the moisture dew point, not the acid dew point). Commenter 20419 maintains that, as written, Table 3 suggests that startup at this EGU ends once the plant begins to burn coal, which is too earl y

– if the EGU puts the baghouse into service before the flue gas is above the moisture dew point, the EGU would experience bag blinding. Commenter 20419 notes that another member ’ s EGU begins startup by firing distillate oil; however, it must fire coal ea rly in the startup process to reach the temperatures necessary to complete the startup process and it is technically infeasible for the EGU to initiate operation of the ESP when it first fires coal, because the EGU still contains oil. Commenter 20419 maint ains that operating the ESP while the EGU contains oil can cause fouling of the ESP, in which a film coats the ESP and can result in substantial equipment damage and a reduction in emissions control efficiency (o perating the ESP while

it still contains oil also can cause serious safety risks; o il residues may combust when the ESP sparks,

which could start a fire )

. Commenters 20417 and 20419 say, for many EGU s the startup of their117

emission controls is dependent on achieving the proper temperatures to safely and appropriately place the emission controls into operation. Commenters state, it is often the case that primary fuel firing (i.e., coal, residual oil or solid oil

- derived fossil fuels) is needed for EGUs to obtain those proper temperatures. Commenters sa y start

- up fuels (i.e., natural gas or distillate oil) alone may not provide the proper heat input to produce the temperatures needed for proper operation of the emission controls.

Commenters

, therefore

, request that the EPA not define the end of startup b ased on when coal, residual oil, or solid oil

- derived fuels are first combusted as currently stated in Table 3.

Response to Comment 107 : See responses above concerning the technical concerns identified in these

comments. The EPA believes that its analysis of the startup practices of the top performing 12 percent of EGUs, which included all types of EGUs, and its final definition of “startup” adequately balances

commenter s’ concerns with the requirements of CAA section 112. The EPA has acknowledged elsewhere in this document that it is aware that both clean fuels and the primary fuel may need to be used together to bring certain non

- PM controls on line and that acknowledgement was in both the final rule and proposed reconsid eration. The EPA believes it is appropriate to define what fuels are “clean” and, therefore, suitable for use during periods of startup and shutdown so as to minimize HAP

emissions.

Comment 1 08 : Commenter 20421 disagreed with the requirement for clean fue l (i.e., natural gas or distillate oil) for SS of stoker coal

- fired boilers. C ommenter states that it s boilers ’ initial design features did not include the ability to start up on natural gas or distillate fuel and the facilities have no gas or

distillate oil available on site. Commenter indicates that switching to natural gas for startup is not

feasible due to the inaccessibility of the natural gas supply and an indefensibly high cost to gain access to natural gas and retrofit facilities to startup on natural gas. C ommenter states that retrofitting each of

its facilities to utilize natural gas or distillate oil sole ly for use during SS periods, is not feasible, is not supported by the rulemaking record, and is not justified by corresponding environmental benefit.

Commenter alleges that the costs for infrastructure to supply natural gas to each of its facilities rende r natural gas a non

- viable compliance option. Commenter provides estimates from natural gas providers for each facility that include the annual costs (over 15 years) of pipeline construction (which include gas system upgrades, new 10,000 foot lateral pipel ine, metering and reducing station, etc. and will take 3 years upon authorization) along with boiler modifications. Commenter states that these estimates ranged from $3.8 to $7 million per EGU. Commenter notes that these estimates do not include the cost o f the natural gas and that one

- time costs for EGU modifications are also estimated. Commenter also provides similar cost estimates for distillate oil that range from $3.1 to $3.2 million per EGU.

Comment 109 : Commenter 20421 states that the required infrastructure (truck unloading and containment stations and distillate storage tanks) necessary to use distillate oil as the startup fuel would be particularly problematic at its Spruance facility due to existing site congestion

– Sprua nce is comprised of 8 boilers, switchyard, coal storage, 2 5

- cell cooling towers, warehouse, craft shops, 8 scrubbers, 8 baghouses, 4 turbine

- generator sets, and all ancillary equipment typically required to support an EGU, all of which is located on just 22 acres.

Response to Comments 108 and 109 : The EPA believes that the final definition of “clean fuels” adequately accounts for comm enters EGUs

. Generally, a valid CAA section 112(h) standard will require

many sources in a category to make investments that will reduce HAP emissions. Commenter does not indicate its current method of startup of its stoker boilers but the EPA believes that if a substrate soaked118

with (e.g.) diesel fuel or distillate oil is used in startup

, it is this diesel fuel or distillate oil that is the “startup” fuel rather than the substrate; as long as these diesel fuels or distillate oil meet the definition of

“ clean fuel” in the final rule, they would be appropriate for use during startup.

Comment 11 0 : Commenter 20413 states that the EPA is proposing the use of cleaner fuels such as fuel oil only or natural gas only during the entire period defined as startup. Commenter operates a coal

- fired cyclone boiler that is designed to combust fuel oil as a startup fuel before slowly transitioning to 100 percent coal combustion. Commenter states that the configuration and design of this boiler does not

allow for the use o f only fuel oil from the time of the initial start of the EGU to the point of electricity generation and full activation of all pollution control equipment. Commenter asks that the EPA take into consideration how startup fuel feed systems must rely on a mi xture of both cleaner fuels and coal in order to complete the defined startup period for coal

- fired cyclone boilers.

Response to Comment 110 : The EPA believes that its responses above concerning technical concerns with compliance address this comment

.

2. 3 Edit to standard

Comment 111 : Commenters 20417 and 20419 ’ say, as written, Table 3 suggests that startup ends, and normal operation begins, once an EGU converts to firing coal, residual oil, or solid oil

- derived fuel. Commenters note, however, this is inconsistent with the proposed definitions for the end of startup in the Proposed Reopening which defines the end of startup based on hours after 25 percent load is first reached or hours after first electricity generation, as well as with the proposed de finition of startup in the Proposed Reconsideration Rule (which defines startup in reference to the generation of electricity that is sold or used for any other purpose). Commenters request that the EPA revise Table 3 to be consistent

with the final defini tion of startup to eliminate regulatory ambiguity.

Response to Comment 111 : The EPA believes that the finalized definition and table eliminate any regulatory ambiguity.

3.0 APCD OPERATION

Summary of Comments Received Following November 30, 2012, Proposal

3 .1 Startup

Comment 11 2 : Commenter s 2 0248, 20251, 20254, 20267, 20269, 20272, 20273, 20275, 20276, 20279, 20286, 20287, 20288, 20289, 20295, 20297, 20303

, and 580 3 express concern over the proposed requirements to start up only the listed control devices when the primary fuels are introduced and state that control devices such as baghouses and ESP, which are not listed, should be included in the list of

controls that need not be operated until it is technically feasible. Commenter s recommend that the rule be revised to allow all control equipment to be started as expeditiously as practicable after initiating startup operations. Commenter s states that t o do otherwise w ould be contrary to manufacturers ’ specifications and good engineering practices, would risk damage to the control equipment and could

result in unsafe conditions.119

Commenter 2 025 4 states that the requirements that baghouses must be in use as soon as any coal is burned in the boiler is not consistent with equipment manufacturers ’ specified operating procedures, especially for older or smaller coal fueled boilers that are not able to achiev e the correct temperature for the operation of a baghouse while using the igniter to burn a “ clean fuel ” as required under the MATS startup work practices standards. Commenter states that in many instances the igniter offers only a low heating value, espec ially on older and smaller EGUs and therefore cannot serve a heating function well over long periods of time and would thus require a large number of additional hours to reach proper startup temperatures if an EGU is solely using the igniter and a clean fuel.

Commenter 2 025 4 states tha t it may be impractical to get the boiler up to the correct temperature where natural gas is the only fuel used as it could require a large amount of natural gas and there may be natural gas supply concerns for these EGUs , for example, where the natural ga s pipeline capacity is

limited. Commenters 2 0254 and 2028 8 state that at EGUs that must burn coal to reach the correct temperature, starting up the baghouse immediately upon combusting coal would be inconsistent with the

manufacturers ’ specification for th e proper and safe operation of the baghouse.

Commenter 2 025 4 states that if the EPA does not allow for baghouse startup flexibility, commenter

urges the EPA to provide clarification that installation of new and additional burners to preheat the baghouse would not be considered a modification for purposes of NSPS and NSR programs.

Commenter 2 032 1 states that its plant follows procedures based on the manufacturer ’ s recommendations and the plant ’ s experience, which require it to maintain flue gas temperatures for over 2 hours before its ESP can be energized. Commenter states that premature starting of controls damages air pollution control device equipment.

Commenter 2 027 2 states that if the EPA does not determine that an exception during startup regarding ESPs is warranted, it must at least ensure that the installation of additional burners to pre

- heat the ESP be classified as a pollution control mechanism and not considered a modification for pu rposes of NSPS and NSR programs.

Commenter 2 026 9 asks that the EPA allow EGUs to start ALL pollution control devices when it is technically feasible. Commenter notes that the type of control device, the local weather conditions, flue gas temperature, and safety concerns influence when startup is technically feasible.

Commenter 2 030 3 suggests the time frame between coal combustion and all air pollution devices in

oper ation be “ as soon as practicable ” allowing a grace period of one hour.

Commenter 5 80 3 requests that the EPA continue to review and reconsider the operating constraints of all other emission control systems as they relate to the startup of EGUs in this rul e.

Commenter 2 027 5 states that due to existing EGU design, it may be necessary for the boilers of certain

low

- rank coal EGUs to reach established air temperatures before pulverization of the coal begins and then require additional time for the phased

- in o peration of environmental controls

- specifically ESPs. It

is commenter ’ s experience that it should take no more than one hour to phase in ESPs once pulverization commences. Commenter states , therefore, the pollution control requirements for coal

- fired

EGUs during startup should be required “ as soon as practicable, ” rather than immediately upon startup,120

or at a minimum , the EPA should provide a grace period of at least one hour after boilers reach temperatures necessary for pulverization to begin operati on of all control technologies.

Commenter s 2 0272 and 2028 8 express concern that many coal

- fueled EGUs must combust coal along with oil or gas during startup in order for the ESP to achieve adequate temperatures for the proper and safe operation of the con trol equipment. Commenter s ask that the EPA should note that the use of oil and coal during startup is not binary, but rather operates on a continuum. Commenter s recommend that the EPA define work practices for control systems, including EPSs, material inj ection systems and baghouses, based on vendor recommendations and engineering practices for each system type, which are outlined by commenter s

.

Commenter 2 028 6 states that the requirement regarding operation of pollution control equipment during

startup operations should be revised to be more general or provide for case

- by

- case exemptions beyond the specific list of equipment the EPA has exempted. Commenter states that the EPA should revise the provision to require the source to start all pollution control equipment as expeditiously as practicable after initiating startup operations. Commenter states that alternatively, the EPA could include a petition process allowing for case

- by

- case exemptions to provide additional flexibility. Commenter states that if only certain pollution control equipment are exempted, then the EPA must periodically reevaluate the exempted equipment as pollution control technology advances and revise the rule accordingly or the provision could become a disincentive to the deployment of newer technology.

Commenter 2 029 7 states that its warm

- up burners, firing ULSD, are rated to supply only about 5 percent of the rated continuous heat input required for EGU operation and cannot bring the EGU and associated air pre

- heaters, two stages of ESP, and FGD up to anywhere near the temperatures required for safe operation. Commenter notes that i t can take up to several hours of coal combustion at minimal operating

lo ads to achieve temperatures necessary for safe operation of the ESPs, ACI, and FGD. Commenter

states that this requirement is part of its Title V permit which allows up to 8 hours for a staged startup of

the emission control from the time the EGU is on the grid. Commenter states that the proposed language does not recognize that there are multiple stages of applicable emission control equipment that must be started up in sequence and in the proper order. Commenter recommends revising section 3 of Table 3

and provides example language.

Commenter 2 027 3 recommends that in Table 3 a qualifier such as “ within the constraints for normal startup of the EGU and dry scrubber, ” after “ as expeditiously as possible ” be added to the language.

Commenter states that this would address the need for the CDS to attain the temperature necessary to start the system.

Commenter 2 024 8 requests ESP to be added to this list of control devices in Table 3 or alternatively, that language be added to the MATS rule allowing for special consideration for unit

- specific issues for safely bringing control devices into operation as may be addressed by local permitting agencies and incorporated into an EGU ’ s operating permit.

Commenter 2 028 7 states that to eliminate ambiguities, the final rule should reflect the temperature constraints of dry scrubber, SNCR and SCR systems explicitly in Table 3 and indicate that operation of these systems is not required unless appropriate temperatures have been rea ched.121

Commenter 2 027 2 states that affected coal

- fired EGUs should not be required to place their ESPs into service until coal has been continuously combusted for 3 hour s and the ESPs have reached safe minimum temperatures in order to prevent fires and/or explosions within the precipitators

. Commenter cites two separate consent decrees that allow for this.

Commenter 2 025 1 states that ESPs, baghouses, and DSI systems should also be treated as SNCR, SCR, and dry scrubber systems, and should not be engaged on ce firing of coal is started. Commenter suggests the following startup language for Table 3 of the proposed rule for coal

- fired, liquid oil

- fired, or solid

oil

- derived fuel

- fired EGU:

Once you start firing coal, residual oil, or solid oil

- derived fuel, yo u must vent emissions to the main stack(s) and engage all of the applicable control devices except limestone injection in FBC EGUs, dry scrubber, SNCR, and SCR . You must start your limestone injection in FBC EGUs, dry scrubber, SNCR, and SCR control equipment systems as expeditiously as possible, but, in any case, when necessary to comply with other standards applicable to the source that require operation of the control devices.

An alternative would be:

Once you start firing coal, residual oil, or solid oil

- derived fuel, you must vent emissions to the main stack(s) and engage all of the applicable control devices except limestone injection in FBC EGUs, dry scrubber, ESP, baghouse, DSI

, SNCR, and SCR. You must start your limestone injection in FBC E GUs, dry scrubber, ESP, baghouse, DSI, SNCR, and SCR systems control equipment systems as expeditiously as possible, but, in any case, when necessary to comply with other standards applicable to the source that require operation of the control devices.

C ommenter 2 028 8 states that companies should be allowed to specify that startup period ends for purposes of the Hg MATS limit when affected EGUs equipped with SCRs and FGDs are both placed into service given that optimal Hg controls will not occur for many EGUs until this combination of emissions control equipment is in full service.

Commenter 2 027 9 urged the EPA to consider that new pollution control devices will be developed in the future which may have similar technological limitations on operation durin g startup and shutdown.

Commenter also states that the EPA should provide that all pollution control technology that cannot operate during startup and shutdown conditions begin operating when it is practicable to do so, rather than specifically providing an exception for limestone injection, dry scrubbers, SNCRs, and SCRs ( commenter notes that certain EGUs cannot start ESPs prior to co m busting coal and that an ESP also requires a two

- to

- one coal

- to

- oil burn ratio to minimize the risk of explosion due to sp arking in an energized field).

Response to Comment 11 2 : As stated in response to other comments on the technical issues associated with compliance with the final work practice, the EPA believes that there are

solutions to all or almost all of those issues

. In addition, t he EPA believes that its analysis of multiple years of data for the startup practices of the top performing 12 percent of EGUs, which included all types of EGUs, and its final definition of “startup” adequately balances commenter s’122

concerns with the requirements of CAA section 112. In addition, as noted in the response to comments 89 and 90 above, we have included a provision whereby EGUs may petition for an alternate time by which PM APCDs must be engaged.

Comment 11 3 : Commenter 5 803 agree d with the EPA ’ s expanded list of exempted controls.

Response to Comment 11 3 : This comment requires no response.

Summary of Comments Received Following June 25, 2013, Reopening of Public Comment Period

3.2 General

Comment 11 4 : Commenter 20427 states that contemporary Hg, PM

, and acid gas APCDs can be operated at all times that coal is burned at an EGU. Commenter states modern PM, acid gas, and Hg APCDs achieve peak pollution reductions within minutes of engagement of the APCD. Commenter

states that e ven were some temperature threshold to exist, which it does not, neither industry nor the

EPA has provided any basis for creating a 4

- to 6

- hour exemption between reaching that threshold and application of the numeric standards, nor is there any basis to e xempt plants from numeric standards when coal is burned prior to electricity generation.

Commenter 20433 rebutted Commenter 20427 ’ s assertion that controls are immediately effective, including in its comments on the proposed reconsideration rule (EPA

- HQ

- OAR

- 2011

- 0044

- 5794).

Commenter 20433 notes , e.g., the Hg emissions of an EGU may spike significantly after electricity generation be gins but before the emission control devices are fully operational. In addition, some SCRs (which will be used for Hg oxidation and control) are designed to operate such that the SCR is bypassed until the startup fuel is removed to prevent catalyst contami nation; once the startup fuel is removed, the SCR inlet dampers are gradually opened at a controlled rate of temperature change over a period of approximately 12 hours, depending on various conditions associated with each startup, to minimize

thermal stres s, ammonium bisulfate formation, and acid corrosion, and to prevent immediate structural damage within the SCR. Commenter 20433 states that the SCR can be fed ammonia only when the critical minimum operating temperature (typically 650 to 700 °F) is reached ; during this period of SCR startup, Hg oxidation and Hg emissions are unpredictable.

Commenter 20427 states that the EPA should, at a minimum, retain the requirement that APCD be operated at all times that coal is burned, and the numeric standards be met whenever electricity is generated. Commenter states that available technologies allow combustion of NG or distillate oil to achieve normal operating temperatures and that operating temperature does not constrain plant

- owners ’ ability to operate pollution controls when coal is being burned in the boiler . Commenter states that the

EPA ’ s argument that some igniters have a low heating value, and some igniters may not have sufficient capacity, and some igniters may not be able to generate adequate heat to prehe at APCD even when operated for extended periods, are only applicable to a handful of older coal

- fired EGU s. In addition,

commenter states that the EPA ’ s argument that some pipelines are too small to provide sufficient NG capacity only affects a limited num ber of older coal

- fired boilers. Commenter states that a few igniters of older design or smaller pipelines that need to upgraded or replaced does not demonstrate that the work practice is impractical or infeasible. Commenter states that igniters capable of reaching normal operating temperatures are readily available and in use at most contemporary coal

- fired EGU s.123

Commenter states the Act ’ s air toxics provisions seek to ensure that older equipment is upgraded and improved, to reduce toxic pollution. Comment er states that with relatively modest investments, NG or distillate oil can be used to reach necessary temperature thresholds for APCDs at all pulverized coal plants.

Commenter 20433 rebutted Commenter 20427 ’ s comment that “ relatively modest investments ” would be needed to reach the appropriate temperature thresholds. Commenter 20433 cites to previously filed comments (EPA

- HQ

- OAR

- 2009

- 0234

- 20400,

- 20281) and notes that the investments required to reach the temperature achieved through coal firing using on ly startup fuel are far from “ modest. ”

The systems that supply [startup] fuels to the boiler...are generally too small to replace coal. As an example, one type of coal pulverizer operated by Duke Energy has seven or eight individual burner lines, and it i s used for both subcritical and supercritical units. Each of the burner lines is paired with an oil gun that is used to light the coal fire and to stabilize the coal flame when the pulverizer is operated at lower capacity. The heat input

from coal for this pulverizer is about 1,200 MMBtu per hour, while the oil guns are only capable of delivering 17.5 MMBtu per hour. Clearly the oil guns do not have the capacity to deliver the same amount of heat provided by the coal pulverizers. Even if the oil guns

were r adically increased in total capacity, the rest of the system including tanks, pumps, piping, controls, etc. would all have to be increased to match. As a result substituting cleaner fuels in place of coal can have only a limited effect or would require ext ensive modification just to accommodate more use of these fuels during startup periods.

Commenter 20433 maintains that the theoretical investments required to get an EGU up to the same temperature reached during stable coal firing using startup fuel would be significant , not modest.

Comment 11 5 : Commenter 20420 supports the EPA ’ s proposal to allow all of the applicable APCDs except limestone injection in ( CFB ) EGUs, dry scrubber, SNCR, and SCR to be engaged during startup and disengaged during shutdown as appropriate based on temperature restrictions and other operational requirements. Commenter notes that the proposed changes will allow it to operate its dry s crubbers, SNCRs, SCRs, and limestone injection systems safely in accordance with manufacturers ’ specifications.

Comment 11 6 : Commenter 20421 states that the proposed definition for the end of startup for coal

- fired EGUs makes compliance with the work prac tice standard possible for most coal

- fired EGUs and agreed that most APCDs should be able to meet their permissive temperatures in the timeframe the EPA has used to define the end of startup, under normal conditions. C ommenter notes , however, that the revi sed rule does not take into consideration unusual circumstances, nor does it consider EGUs whose APCD permissive temperatures extend beyond the period of time that the EPA has proposed that startup ends.

C ommenter states that such a requirement is untenabl e, because it imposes a regulatory requirement that some facilities are operationally incapable of meeting. C ommenter suggest s the following text to be added to the requirement that APCDs be engaged as expeditiously as possible:

in accordance with original equipment manufacturer recommendations and prudent industry practices.124

Commenter notes that even with the addition of this language, which would assist in compliance, the

EPA must also address the more difficult issue of its limit on the timefram e for startup.

Comment 11 7 : Commenters 20402 and 20404 state that the EPA ’ s definition of “ startup ” does not accurately reflect the end of the startup period, given that many of the APCDs need time to safely and effectively startup and operate. Commenter 20402 strongly supports the EPA revising the definition of startup to include the “ end ” point of 25 percent of nameplate capacity plus 3 hours or the start of electricity generation plus 6 hours, whichever comes first because it more accurately c aptures the period of time during which an EGU transitions from offline to fully operational and able to provide the defined electricity or steam demands. Commenter 20402 notes that, in addition, the revision recognizes the real operational differences amo ng EGUs and indicates that clearly and accurately defining the end of startup is critical as it introduces the point in time when specific parameters are to be met, emission controls are to be fully operational, and the source is in compliance with applica ble numeric emission standards. However, Commenter 20402 cautions the EPA that even this more flexible definition may exclude certain EGUs from complying with the rule, and recommends that an alternative petition approach be available to such EGUs.

Commen ter s 5833 and 5834 state that trying to operate or use installed emissions control equipment during SSM periods will damage the equipment , impact their ability to continue operation or meet permit conditions, and could violate manufacturer operational guid elines in many cases

. Commenter

5833 maintains that i f the EPA promulgates the SSM proposal as described, electric reliability will be impacted and an overall increase in emissions could occur because of damage to APCDs.

Commenter 5833 notes that its emis sions control equipment is designed to operate at minimum and full load for extended periods of time and will not operate at full efficiency during startup periods and that emissions during startup and shutdown periods are low due to the short period of ti me and its efforts to minimize startup and shutdown periods. Commenter indicates that some of its facilities and equipment must use alternative fuels during startup periods that emissions control equipment is not designed to target. Commenter alleges that, as the EPA knows, malfunctions cannot be anticipated or predicted and urges the EPA to try to avoid implementing a one

- size

- fits

- all approach, especially given site

- specific issues that may arise.

Commenter 20401 notes that because properly operated and maintained equipment will outperform improperly operated and maintained equipment, the EPA ’ s startup definition should be formulated in a way that maximizes utilities ’ ability to meet the recommended requirements for proper operation as well as to avoid unnecessary safety risks and possible damage that would reduce the overall performance of

the APCD , and that the startup definition should be revised to allow for the boilers and associated APCD to go through all the recommended steps to reach flue gas conditions necessary for safe, stable operation.

Response to Comment 117 : The EPA believes that its analysis of the startup practices of the top performing 12 percent of EGUs, which included all types of EGUs, its final definition of “s tartup,” and its final definition of “clean fuels” adequately balance commenter s’ concerns with the requirements of

CAA section 112. Responses to the specific issues raised by commenters may be found elsewhere in this document. With regard to commenter’s s tatement “ that some of its facilities and equipment must use alternative fuels during startup periods that emissions control equipment is not designed to target”

– we125

are finalizing that all EGUs must use one (or more) of the clean fuels defined to the max imum extent possible during startup.

Comment 118 : Commenter 20403 suggests a revision in the standard which would allow APCD to start as soon as technically feasible and not “ at all times during startup ” as previously written or process control to be implemented as soon as technically feasible. C ommenter states that this addresses the concern of limestone injection in coal

- fired CFBs but also includes other APCDs. C ommenter states that

all the APCDs shoul d be allowed to meet their permissive temperatures in the time allotted under the proposed “ end of startup ” language.

Commenter 20410 states that if the EPA is going to take the current proposed approach, the excluded controls should also include ESPs, ba ghouses, and DSI.

Comment 1 19 : Commenter 5834 recommends that proposed Table 3, work practice 3, paragraph 4 be revised to except other APCDs as follows (revisions indicated with underlines):

Once you start firing coal, residual oil, or solid oil

- derived fuel, you must vent the emissions to the stack(s) and engage all of the applicable control devices except ESPs, ESPs in combination with activated carbon injection , limestone injection in FBC EGUs, dry scrubber, SNCR, and SCR. You must start your ESPs, ES Ps in combination with activated carbon injection , limestone injection in FBC EGUs, dry scrubber, SNCR, and SCR systems as expeditiously as possible, but, in any case, when necessary to comply with other standards applicable to the source that require oper ation of the control devices.

Comment 12 0 : Commenter 20426 recommends that the work practice standard consider the type of

APCDs used and define the startup period (start to end) to accommodate the time necessary for this equipment to be placed into operation. Commenter states that, the period of startup and shutdown needs

to take into consideration the limits of the APCD that is u sed to meet the applicable MATS limits.

Commenter states that the work practice must be clear that the end of startup occurs when conditions meet a minimum level that is associated with the proper operation of the pollution control equipment

and the method utilized. Commenter states that, without this consideration, the period of time between the end of startup of the EGU and the time when a specific pollution control system must start may cause the source to exceed the limit, even considering the 30

- day av eraging period. Commenter states that the testing used for developing and setting the emission limits included stack testing when the EGU s are operating at full load, or the predominately normal operating load, under steady state conditions.

Commenter stat es that startup by definition is a transient condition that exposes the equipment to changing conditions and this reality must be adequately considered in the final rule.

Response to Comments 118

- 120 : The EPA believes that its analysis of the startup pr actices of the top performing 12 percent of EGUs, which included all types of EGUs, and its final definition of “startup” adequately balance commenter s’ concerns with the requirements of CAA section 112. Responses to the specific issues raised by commenter s may be found elsewhere in this document.

3.3 Multiple APCDs126

Comment 12 1 : Commenter 20390 indicates the complicating factor (for multiple APCDs in series) is that SCRs, wet FGD, and dry FGD can be operational at different times during the startup cycle, and each technology ’ s design characteristics mandates different operating conditions that cannot be

s ingularly defined that the entire plant has completed startup.

Commenter 20390 states that the impact on emissions and APCD operations is not directly related to the use of startup fuels, steam flow, or synchronization to the grid. APCD systems’ ability t o function and operate is based on flue gas temperature and volume flow.

Commenter 20390 states coal plant startups are either warm startups or cold startups, and shutdowns are either normal shutdowns or emergency shutdowns. Commenter notes the duration o f startup is dependent on the speed the system can brought up in temperature without causing thermal stress.

Commenter states that facilities sync to the grid after certain temperatures are reached in the steam turbine, and notes the operator cannot put lo ad on the generator until the EGU is synced to the grid so as soon as there is load on the generator (for example, >1 MW), the EGU can be assumed to be on

- line. Commenter notes that at certain plants, coal firing can begin following the sync to the grid wh ich is usually no more than 20 minutes after syncing; other plants require higher loads before firing coal.

Commenter states startup fuel is continued until a certain number of coal mills are brought into service

and that at some plants the startup fuel is co

- fired and continues till 1/2 load and at other facilities it continues till 2/3 load. Commenter indicates that the capacity of each plant is different as to its ability to burn an auxiliary or startup fuel

– some plants only have igniters and can burn startup fuel only to about 10 percent of the design heat input whereas other plants have fuel burners that can burn auxiliary fuel up to full load. Commenter states, therefore, that it may not be possible at every plant to bring the system

up to temperatur e with clean burning startup fuel and to bring APCDs into service prior to firing coal.

Commenter 20390 provides a summary table of typical startup procedures for multiple APCDs for warm and cold startups, see Table 1.

Table 1. Typical Startup Procedure s ( Commenter 20390 )

.

APC Equipment Warm Startup Cold Startup

SCR Require minimum temperature

(independent of load or duration) prior to ammonia injection Require minimum temperature (independent of load or duration) prior to ammonia injection

SNCR Require minimum temperature

(independent of load or duration) prior to ammonia injection Require minimum temperature (independent of load or duration) prior to ammonia injection

Wet FGD No minimum requirements prior to

startup No minimum requirements prior to

startup

Spray dryer/baghouse Require minimum temperature and flue

gas flow prior to lime slurry spray.

Some emissions can be maintained with baghouse s prior to slurry injection Require minimum temperature and flue gas flow prior to slurry spray. Some

emissions can be maintained with baghouse s prior to slurry injection127

CDS/baghouse Require minimum flue gas flow prior to

lime injection and require minimum temperature prior to water spray. Some

emissions can be maintained with baghouses pri or to additional lime and water injection Require minimum flue gas flow prior to lime injection and require minimum temperature prior to water spray. Some

emissions can be maintained with baghouses prior to additional lime and water injection

DSI or carbon injection system Require minimum flue gas flow prior to

sorbent injection. Trona and SBS systems require minimum temperature. Do not inject carbon while firing oil Require minimum flue gas flow prior to sorbent injection Trona and SBS sys tems require minimum temperature. Do not inject carbon while firing oil

Baghouse Pre

- coating of bags required prior to

startup Pre

- coating of bags required prior to

startup

ESP Energize when flue gas temperature

>250 ° F Energize when flue gas temperature
>250 ° F

Response to Comment 121 : The EPA believes that the revised definition of “ startup ” discussed elsewhere in this document adequately addresses commenter ’ s concerns. We would also note that the

definition of “ startup ” does not specifically relate to the terms “ cold startups ” or “ warm startups; ” rather, it is tied to the initiation of firing of fuel following a period where no fuel had been fired through the language “ first

- ever firing of fuel in an EGU for the purpose of produci ng electricity or useful thermal energy (such as heat or steam) for industrial, commercial, heating, or cooling purposes or the firing of fuel in an EGU for any purpose after a shutdown event. ” Sources that are starting a cold or warm EGU

may have to combu st additional clean fuels a lone for a longer period of time to comply with the final work practice ; this may require augmentation of their clean fuel capacity

. Responses to the specific issues raised by commenters may be found elsewhere in this document.

Comment 12 2 : Commenter 20408 states that the EPA should reassess the proposed requirement to

“ vent emissions to the main stack and operate all control devices necessary to meet the operating standards that apply at all other times under the final rule ... ” to recognize for some boiler types (i.e.

, cyclones) that although the APCD will be activated it may not be at its normal operating level of control.

Response to Comment 122 : The EPA has addressed the issues related to startup earlier in this

document an d ESP use in section 3.0 of this document. Further, we believe that the revised definition of

“ startup ” addresses the remainder of commenter ’ s concerns. We have noted elsewhere in this document

that the goal of the analysis was to identify the approximate time it took, on average, to initiate operation of APCDs by the top performing 12 percent of EGUs to determine the appropriate end for startup

– a time at which we are confident sources will be able to accurately monitor their emissions using CEMS

. The goal was not to seek the time it took for APCDs at all EGUs to become operational , nor do sources have to engage all of their control devices at the end of startup

. Instead, sources are required to comply

with the numerical emissions limits in whatever man ner the source determines is appropriate. The EPA

believes that the variability contained in the numerical limits is sufficient to include all periods of EGU operation , including start up and shutdown . We further note that the 30

- day rolling operating day a verage provide EGUs with additional flexibility to meet the emission limits using CEMS, and sources can also

continue to use clean fuel if they want an additional compliance margin

.128

3.4 Acid Gas APCDs

Comment 12 3 : Commenter 20427 states acid gas APCDs at pulverized coal EGU s are not temperature dependent and can meet the MATS ’ numeric limits over a wide variety of temperatures and loads.

Commenter states that basic acid gas APCDs can meet the numeric limits over a wide variety of

tempera tures and loads, and there is no basis for further exempting EGU s from complianc e with those

limits. Commenter notes that scrubbers are routinely designed without bypass and are operational at all loads, and that DSI improves capture at low temperatures. C ommenter states that the MATS ’ acid gas limits do not require either DSI or scrubber systems to operate at the upper ranges of those technologies ’

abilities. Commenter states that complaints that scrubbers may be affected by weather conditions, resulting i n stack corrosion, can be addressed by using liners for wet gas.

Response to Comment 123 : The EPA is not exempting sources from HAP emissions reductions requirements as the commenter states. The EPA maintains that its analysis of the startup practices of the top performing 12 percent of EGUs, which included all types of EGUs and APCDs , and its final

definition of the end of “startup” adequately balances commenter ’s concerns with the requirements of

CAA section 112. Responses to the specific issues raised by commenters may be found elsewhere in this

document.

3.4.1 Wet f

lue gas desulfurization

– wet FGD

Comment 12 4 : Commenter 20387 notes that FGD EGU s are placed in service once the EGU reaches stable operation with coal. Commenter notes that past experience with placing the FGD EGU s in service while firing fuel oil resulted in fouling of the FGD tower and required the entire liquid level to be removed and replaced. Commenter maintains that this operating histor y requires the FGD to be placed

into service once the EGU has reached “ Stable Operation with Coal ”

.

Commenter 20390 states wet FGD systems are capable of maintaining SO 2 emissions during startup and shutdown periods. Commenter states that wet FGD EGU s have fiberglass or plastic components that must be protected against high gas temperatures ( i.e., approximately 220 ° F ) . Commenter states one or two of the lower spray headers must be turned on once the manufacturer ’ s maximum temperature guideline is rea ched regardless of whether auxiliary fuel or coal is being burned. Commenter states a minimum number of recycle pumps must be in service at low load to protect against down draft slurry.

Commenter 20425 states that EGU start

- ups from outages where wet FGD maintenance occurs and recycle tanks are drained may require an extended period of time to establish suitable scrubber chemistry, particularly, alkalinity, to minimize SO 2 emissions. Commenter notes that although limestone forced oxidation (LSFO) systems can reach suitable alkalinity levels very quickly after start

- up, magnesium

- lime (mag

- lime, Mg

- lime) systems require much longer time periods to establish suitable alkalinity, up to 12 hours for some EGUs, and to establish the proper levels of liquid phase magnesium

and sulfite.

Response to Comment 124 : Responses to these comments can be found above.

3.4.2 Dry FGDs and CFBs129

Comment 125: Commenter 20409 states that for EGU s with dry FGD systems and ash recycling, the startup time following planned outages required to introduce coal fuel ranges from about 6 hours for unplanned hot restart events to as many as 32 hours for major scheduled outages. Commenter states that

that d epending on the scrubber system installed, from 6 to 18 hours may be required to achieve

sustainable SO 2 reductions once coal fuel is introduced and the necessary flyash has been collected. Commenter adds, although not specifically identified in the EPA ’ s Startup TSD , cooperatives with CFB boilers equipped with SNCR for NOx reduction would have similar concerns if, for example, NOx compliance obligations commence when the proposed HAP SSM startup ends.

Commenter 20410 states that the Startup TSD indicates that the EPA found no significant difference in performance related to startup events between the different boiler types and APCD technologies assessed in the analysis. Commenter s 20409 , 20410, and 20423 state that, although not specifically

discussed in t he narrative, the data in Figure 16 of the EPA ’ s Startup TSD show a distinct difference between dry and wet FGD SO 2 emissions rates as a function of hours after start after generation for

subcritical EGU s. Commenter s state that although not identified in the EPA ’ s Startup TSD

, it believe s there are subcategories of EGU s within the subcritical dry FGD group that will frequently take a significantly longer time to reach normal operation regarding SO 2 emissions reductions. Com menter 20410 states that, in fact, Figure 16 shows that 6 hours after the start of generation, SO 2 emissions with a dry FGD are still approximately twice the MATS alternate SO 2 limit while the wet FGD shows

emissions below the MATS alternate SO 2 limit thro ughout the startup. Commenter 20410 adds that Figure 16 shows the average SO 2 rate, so presumably there are values below and above the line shown in Figure 16. Commenter s 20409 and 20423 state that subcritical EGU s utilizing ash recycling for proper dry FG D function clearly fall into one of these subcategories because additional time is needed to collect the flyash necessary to properly prepare and mix the slurry for proper FGD function.

Commenter s 20409 and 20423 state that, for example, should subcritical EGU s with dry FGDs that utilize ash recycling be required to demonstrate SO 2 emission compliance at the point in time coinciding with the end of startup as proposed for HAP SSM, many may likely encounter SO 2 compliance problems. Commenter 20409 states tha t to be clear, these EGU s would not encounter SO 2 compliance issues following their currently permitted startup procedures and requirements. Commenter 20409 states that dry FGD SO 2 emission rates may not reach anything close to normal expected operating levels until approximately 18 hours after generation start, whereas wet FGD performance appears to reach anticipated operation almost immediat ely after generation commences. Commente r 20423 states that the startup time following planned outages required to introduce coal fuel ranges from about 6 hours for unplanned events to 1 or 2 days for major scheduled outages.

Commenter 20410 states that because it is more common to use dry FGD on lower sulfur coals and wet FGD on higher sulfur coals, the average SO 2 emission rate at 6 hours after start of generation and beyond likely includes data where the dry FGD control device has not been engaged and shows that there is likely an even bigger difference in the time it takes to bring a wet FGD on

- line versus the time it takes to bring a dry FGD on

- line during startup.

Commenter 20409 thinks subcritical EGUs that utilize dry FGDs and ash recycling for SO 2 control and

EGUs that utilize CFB combu stion with SNCR for NOx control comprise two subcategories that would

not be able to meet SO 2 and NOx compliance obligations under the HAP SSM startup proposal. Commenter suspects there are other EGU subcategories where EGUs would be unable to meet non

- HAP emission compliance obligations immediately after the proposed HAP SSM startup ends.130

Comment 126: Commenter 5831 states that the EPA should modify its technical document to include discussion about the use of recycle flyash in an FGD and analyze the hot/ cold startup impacts separately and then modify the conclusions and the definition of startup accordingly. C ommenter states that although the use of recycle flyash does not matter significantly for a hot restart, there is no recycle flyash available to fab ricate a slurry mix for several hours after a cold restart. C ommenter notes that the EPA analysis somewhat addresses this, but the impact is masked by averaging hot and cold restarts together. Commenter states that there are subcategories of EGU s within the subcritical dry FGD group that will always take a significantly longer time to reach normal operation regarding SO 2 emissions

reductions. C ommenter states that EGU s with dry FGDs that utilize ash recycling may likely encounter

SO 2 compliance problems i f they are required to demonstrate SO 2 emission compliance at the time the proposed SSM startup ends. Commenter notes that a recent extraordinary startup of its Holcomb Unit 1 ( H1 ) EGU, following the installation of new over

- fire air and low NO X burners, r equired 32 hours of

low

- load coal operation before sufficient flyash was available to enable the normal operation of the dry FGD systems. Commenter maintains that the EPA needs to modify the Startup TSD to include this discussion and analyze the hot/cold s tartup impacts separately and then modify the conclusions and the definition of startup accordingly

. Commenter indicates that its H1 EGU does not now encounter any SO 2 compliance issues, following current permitted startup procedures, or with any other com pliance limitations or requirements.

Commenter 5831 states that the startup time following planned outages required to introduce coal fuel ranges from about 6 hours for unplanned events to as many as 32 hours for major scheduled outages.

Commenter notes t hat, although not specifically discussed in the Startup TSD, the data in Figure 16 show a distinct difference between dry and wet FGD SO 2 emissions rates as a function of hours of start after generation for subcritical EGUs. Commenter indicates that following a cold restart, its H1 EGU dry

FGD SO 2 emission rates do not reach normal expected operating levels until approximately 18 hours

afte r generation start. Commenter states that its data show false starts can and do exceed the time proposed to end startup under unexpected and unavoidable circumstances. Commenter provides

attachments with information from commenter’s experience.

Commenter 5831 states that, as noted by the EPA, the normal progress of startup activities may involve the cessation of fuel combustion following the initial combustion of ignition or startup fuel. These interruptions may include planned multiple stop/starts (which may include establishing stable igniter operation and flame safety safeguard systems, proof of boiler and/or turbine interlocks, chemical cleaning operation, initial turbine warming, turbine shakedown operations including those for safety and insurance pur poses) of the combustion process, and unplanned, but nevertheless necessary, cessations in the same combustion process (which may include sudden and unexpected flame stability problems; temperature and/or pressure excursions; unavoidable operational equipm ent problems with fans, air heaters, and pumps, for which normal stable expected operational ranges have not been achieved; and unexpected tube leaks which may take multiple days to repair). Commenter alleges that in the experience of its members, these in terruptions range in duration from a few hours to multiple days.

Commenter 5831 cites to a number of examples for its H1 EGU. Commenter indicates that there were

four occasions within the 2

- year EPA analysis of startups (2011

- 2012) where an H1 startup seq uence was interrupted between one and three times before it reached normal operation. Commenter states that these interruptions ranged between 1 hour and 4 hours; in all but one case, the events arose before coal131

fuel had been est ablished. Commenter notes that in a separate prolonged shutdown situation following an EGU trip while using natural gas fuel, an exhaustive troubleshooting exercise was conducted to isolate an electrical problem on the plant control system; a 2

- day effort was required to rectify th e problem once the source was identified. For the examples cited, commenter indicates that stable dry FGD operation was achieved between 2 and 27 hours following stable coal firing.

Response to Comment 126 : The EPA maintains that its analysis of the start up practices of the top performing EGUs, which included all types of EGUs, and its final definition of “startup” adequately

balance commenter ’s concerns with the requirements of CAA section 112. To the extent the commenters believe that the work practice m ust be achievable by all sources without cost , we disagree for the

reasons stated above. The EPA would note that sources are not required to comply with the alternate

SO 2 emission limits at the conclusion of startup but, rather, can comply with the HCl emission limits. Further, commenter notes that some/many of the startup interruptions occurred prior to the firing of coal; however, commenter does not indicate whether elec tricity generation had begun. The final definition of

the end of “startup” is triggered by the start of electricity generation. In any case, if no coal has been combusted, the EGU s could shut down and reinitiate startup on clean fuel alone and be in compli ance with this final rule. The inherently low HAP content of the clean fuels will thus greatly reduce the HAP emissions associated these types of startup events.

Comment 127 : Commenter 20390 states dry FGD systems may include SDA and CDS (to include

Novel Integrated Desulfurization System, NIDS) and these systems typically include an absorber vessel followed by a baghouse . Commenter states that neither system can be operated with slurry or water addition at low temperatures because of the potential corrosion in the ductwork and baghouse

. Commenter states a minimum flue gas flow and temperature must be maintained for SDA to prevent

lime slur ry buildup on the absorber vessel walls, which may cause structural damage or plugging in the

vessel. Commenter states SDA lime slurry controls are not turned on until a minimum of 250 ° F and 50 percent of design flow, although PM removal can be maintained during startup and shutdown periods.

Commenter states that CDS lime can be injected during startup as soon as lime can be suspended in the absorber vessel, and water can be injected when the flue gas reaches 180 ° F dependent on flue gas properties. Commen ter states flue gas flow is normally required to be approximately 50 percent of design flow, and can operate at 25 percent with flue gas recirculation.

Response to Comment 127 : See above for responses to technical and legal concerns identified in these

c omments. Under the final reconsideration startup and shutdown requirements, operators do not have to engage any controls within a specified time period (other than PM controls which must be engaged within 1 hour of firing of coal, residual oil, or solid oi l

- derived fuel ); rather, they are only responsible for meeting the numerical emission limits no later than 4 hours after electricity generation. The use of clean fuels to the maximum extent possible will assist in heating the system to allow the APCD equipment to get to operating temperatures.

Comment 1 28 : C ommenters 20390 and 20410 state that DSI effectiveness is dependent on flow distribution and operating temperature; flue gas flow required is normally approxim ately 50 percent of design flow ( possi bly 25 percent using flue gas mixing ) , and some sorbents require minimum flue gas temperatures (e.g., 250 or 29 0 °F ) . Commenter 20410 states that the downstream PM control device needs to be engaged to capture the DSI reaction products and unreacted sorben t to minimize emissions

of PM.132

Commenter 20424 believes that the standards should also be revised to allow the recognition of the constraints of application of DSI, which should be revised to allow the start of DSI after appropriate temperature is reached

.

Response to Comment 128 : We address technical concerns above.

Comment 129 : Commenter 20424 states that the proposed revised standards would allow limestone injection to begin 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 technic ally feasible after the appropriate temperature has been reached.

Commenter 20427 states that although acid gas emissions at CFB EGUs using limestone injection can be temperature dependent, that provides no basis to exempt boilers from Hg and PM standards because APCDs for those pollutants can be used at low temperatures for both pulverized coal and CFB boilers.

Commenter states that temperature constraints on acid gas APCDs at CFBs do not justify time or load

based exemptions, as the EPA ’ s analysis demons trates there is no reliable correlation between the number of hours elapsed or electricity generation and the achievement of the temperature needed for acid gas control. Commenter states that if an exemption to compliance is added for acid gas limits at

CF B EGU s, the exemption should be temperature dependent, e.g., numeric standard applies when boiler temperature exceeds 1500 ° F.

Commenter 20433 rebutted by stating that Commenter 20427 misunderstands CFB operation. Depending on where a thermocouple is loca ted, Commenter 20433 maintains that a CFB EGU could

record a 1500 °F “ boiler ” temperature from just an oil burner although scarcely having begun the startup cycle. As Commenter 20433 explained in EPA

- HQ

- OAR

- 2009

- 0234

- 20180 and in EPA

- HQ

- OAR

2011

- 0044

- 5794, in an FBC EGU, if lime is added too early in the startup sequence, the flame will be extinguished. Commenter 20433 notes that FBC EGUs that inject limestone must reach a minimum bed temperature of approximately 1500 oF for the limestone to calcine, and th us become effective at reducing acid gases; FBC EGUs often burn coal for about 45 minutes before lime is added and then

additional time is required before the bed chemistry stabilizes ( i.e., the pollution control is fully effective). Commenter 20433 states that normally, the bed is stable and up to temperature when 40 percent load is reached.

Commenter 20425 states that for FBC EGUs, if limestone is added too early in the startup sequence, the flame will be extinguished and that FBC EGUs that inject limest one must reach a minimum of approximately 1500 °F for the limestone to calcine, and, thus, become effective at reducing acid gases.

Commenter notes that FBC EGUs often burn fuel for about 45 minutes before limestone is added and

that additional time is the n required before the bed chemistry stabilizes; normally, the bed is stable and up to temperature when approximately 40 percent load is reached. Commenter recommends that the

EPA should define “ startup ” for FBC EGUs as 3 hours after the bed temperature rea ches 1500 °F; an alternative would be 4 hours after 25 percent load is first achieved, or 12 hours after first electricity generation, whichever occurs first.

Response to Comment 129 : See responses to comment above for responses to these comments. In

addition

, the EPA notes that the requirement to maximize the use of clean fuels during the startup period133

will assist in getting the EGU and the associated APCD equipment up to proper operating temperatures while minimizing emissions of HAP. EG Us are requi red to engage PM controls within 1 hour of

addition of coal, residual oil, or solid oil

- derived fuel and the startup period will end 4 hours after the generation of electricity or creation of useful thermal energy

, at which time the numerical emission

limits must be met

.

3. 5 PM control

Comment 130: C ommenter 20393 states that the Startup TSD only focuses on the startup of SO 2 and NOx control devices and does not address the startup of ESP and other PM control devices. Commenter

states that t he startup of PM control devices should also have been included in analysis in order to assess the startup issues unique to ESPs. Commenter states that the analysis only provides an assessment as to

when coal

- fueled EGUs, on average, will be able to bring online their APCDs and, as a result, fails to set a specific time frame in which it is feasible to start up and operate all APCDs in a safe and efficient

manner.

Commenter 20418 states that the EPA ’ s analysis does not consider the impact of PM control devices on

an EGU ’ s ability to meet the MATS limit during startup. Both of commenter ’ s coal

- fired EGU plants

use hot

- side ESPs to control PM emissions. Commenter notes that these HS

- ESPs are designed to collect fly

- ash when the resistivity is below a certa in threshold, typically occurring at temperatures in excess of 550 °F and operation of the hot side ESPs below these temperatures can diminish the collection efficiency of the equipment. Commenter maintains that this is an important consideration in determ ining the appropriate definition of startup for a rule that incorporates PM emission limitations as a compliance option.

Commenters 5833 and 5834 state that alternative fuels are used during startup that emissions control equipment is not designed to targ et. Commenter s state that the EPA ’ s Startup TSD omits pollutants

other than NO X and SO 2 and omits APCDs for pollutants other than for NO X and SO 2 and did not address the startup of ESP and baghouses. Commenters state that startup of PM control devices shou ld also have been included in analysis in order to assess the startup issues unique to those devices. Commenter 5834 notes that as it and other commenters have demonstrated, similar to the pollution

controls for NO X and SO 2 , pollution controls for PM canno t safely be engaged at first firing of coal due to a minimum operating temperature necessary for their safe and reliable operation and that although its ESPs are engaged at the “ end of startup, ” as per the discussion in the June 25, 2013, notice , the ESPs cannot safely be engaged at first firing of coal due to a minimum operating temperature necessary for their safe and reliable operation. Accordingly, Commenter 5834 maintains that the work practice standards should except ESPs and associated ACI engagement similar to the exception provided for

other APCDs.

Commenter 5833 states that fuel oil is the main startup fuel for its coal fired plants. Commenter alleges that manufacturers of its emission control devices have stipulated that primary particulate emiss ions equipment (baghouses and ESPs) not be put into service when burning fuel oil at low temperatures as fuel oil coats bags in a baghouses and destroys a bag ’ s ability to collect flyash (baghouses have to be bypassed during startup for this reason). Comme nter also maintains that manufacturers also do not recommend energizing an ESP until certain minimum temperatures are obtained or the plates in a precipitator will get coated with fuel oil residue and impact their ability to collect flyash.134

Commenter 5834 submits that coal

- fired EGUs like its Units 1, 2, and 3 that are equipped with ESPs cannot be safely engaged immediately once firing converts to coal without risking significant equipment degradation or, worse, an explosion. Commenter notes that all three of its EGUs use a “clean fuel” (No. 2 fuel oil) during all startup and shutdown procedures

– during startups, fuel oil is usually fired for several hours; however, for cold startups, when the EGU has been off line for more than 95 to 100 hours, it is not uncommon for fuel oil to be fired for up to 20 consecutive hours. Commenter maintains that this extended oil firing is needed to match steam temperature to turbine metal temperature and prevent catastrophic damage to major equipment components. Commenter n otes that while firing on fuel oil, the steam turbine is rotated and synchronized (i.e., power is provided to the grid), yet the ESP

remains off

- line until at least one coal feeder reaches 50 percent of its capacity; at that time, multiple

fields in each c hamber of the ESP are energized and fuel oil use begins to decrease. Commenter states that the ESP fields are not energized during the initial startup procedure in order to allow sufficient time for flue gases passing through the ESP to preheat the ESPs pr ior to energizing

– otherwise, if the ESP is operated at or below the dew point (approximately 180 to 200 °F), an oil or moisture coating forms a cemented dust layer (crusted coating) on the collection plates which impedes proper operation. Furthermore, co mmenter notes that for EGUs, such as the ones it has, that are started up on distillate fuel oil, the ESP is not energized until coal firing is established so as to prevent the possibility of explosions due to oil carry over or ignition of unburned carbon or other combustible gases. Commenter asserts that the prevention of fires and explosions in the ESP is critical to the safety of plant personnel and equipment, and is also consistent with good engineering practice. C ommenter provides several

attachments c oncerning ESP engagement during startup required to ensure safe and reliable operation

consistent with manufacturer recommendations. Commenter alleges that b ecause it is not technologically feasible to operate its ESPs before a safe operation temperature i s achieved, and, therefore, commenter respectfully requests that the EPA adopt its proposed changes to the work practice

standards to address ESPs and associated ACI

.

Commenter 5834 cites to a manufacturer recommendation for its Unit 3 that states:

As the first mill for coal firing is brought on line and flue gas temperature increases to approximately 200°F, a two (2) hour delay is recommended prior to precipitator energization. This will allow sufficient time for flue gases passing through the precipit ator chambers to pre

- heat the internals prior to energizing the transformer/rectifier sets. Operation at or below dew point may cause a crusted coating to form on the collecting electrodes which will impede proper operation.

Similarly, for its Units 1 and 2 Commenter 5834 provides from the operations manuals:

Allow sufficient time for flue gases passing through the precipitation chambers to preheat the internals prior to energizing the T/R sets to insure operation of the precipitator above dew point. Oper ation at or below dew point may cause a crusted coating to form on the collecting electrodes which will impede proper operation. A thumb rule of 1 hour of de

energized operation for every 100 °F of normal flue gas temperature is satisfactory.

Commenter 5834 notes that the oil igniters for its Units 1, 2, and 3 were not designed to preheat the ESP plates without additional heat provided by the combustion of coal; the oil igniters were designed solely135

to light the fuel and provide flame stabiliza tion and are not large enough to provide sufficient heat to reach the minimum safe and reliable operating temperature in the ESPs regardless of how long the oil igniters are fired.

Commenter 5840 states that some ESPs cannot reach safe startup temperature s on startup fuel no matter how long it could be burned; these ESPs require coal firing to achieve a safe startup temperature.

Commenter recommends that the EPA include ESPs in the list of APCDs that do not have to be in service when first tiring coal.

Co mmenter 20387 states ESPs must be placed into service after the EGU is on

- line with one coal mill in

service. Commenters 20387 and 20410 state the original equipment manufacturer ( OEM ) does not recommend placing the ESP in service until fuel oil is no long er required to startup the boiler; the fuel oil may cause fields to spark and ignite, leading to fires that may damage equipment and place plant personnel at risk. Commenter 20387 maintains that this, therefore, requires the ESPs to be placed into

service after the EGU is put on

- line with one coal mill placed in service.

Commenter 20390 states that startup and shutdown are critical periods for ESP operation that can have a direct impact on achieving performance and maintaining this performance. Commenter s tates two main concerns: operating the ESP below the acid dewpoint and spontaneous combustion or explosion of unburned combustibles that could be ignited by sparking. Commenter states ESPs should not be energized until the flue gas temperature is above the acid dewpoint, to avoid moist ash particles collecting on electrodes and hopper walls forming a damp sludge that is difficult to remove. Commenter

states when this buildup of material is dried upon reaching normal operating temperature, it can form

hard c rusty deposits cemented to the electrodes and hoppers, which cannot be dislodged with rapping, and reducing the ESP performance. Commenter states during startup, the damp ash can create wet conductive coating on surfaces of high voltage support and anti

- sw ay insulators, leading to short circuits and potential failure of the insulators. Commenter states SO 3 formed in the boiler reacts with moisture to create sulfuric acid vapor that condenses below the acid dewpoint temperature. Commenter states
sulfuric aci d dewpoints vary depending on the coal type, and range from approximately 276 to 326 ° F

without SCR and from 289 to 340 ° F with SCR (SCR ma y increase the sulfuric acid dewpoint temperature by 10 to 20 ° F depending on SO 2 to SO 3 conversion in the SCR). Commenter states ESPs are typically not energized for 30 minutes after stable flame has been achieved to avoid hazardous

conditions. Commenter states there is potential for carbonaceous material, CO, or unburned fuel during

startup caused by incomplete combustion, and there is also excessive O 2 in the system, which could cause spontaneous combustion or even an explosion, particularly if there is sparking in the ESP with the ESP energized. Commenter states that CO is extremely unstab le so that general flammability limits are considered as explosion limits and that excessive carbonaceous ash (high LOI) production can lead to a fire of the dust collected on the ESP collecting plates and/or ESP hoppers when excessive oxygen levels

are pr esent in the flue gas during boiler startup

– the ignition source in the ESP is sparking between

electrodes. Commenter states applications with higher probability of fires include wood waste boilers, oil fired boilers, and coal stoker fired boilers.

Comme nter 20408 states that introducing S O 3 (to reduce the ash resistivity and improve ESP collection efficiency) too early in the startup process will cause corrosion in the duct work and ESP because of the lower temperatures during startup. Introduction of S O 3 may not be possible until 50 percent load is achieved where temperatures are high enough to prevent corrosion.136

Commenter 20401 states that the startup definition also fails to acknowledge certain parti culate controls

such as ESPs or fabric filters also have operational constraints during startup. In the case of an ESP, Commenter maintains that after purging the boiler there are manufacturer recommended minimum temperature and moisture requirements that must be met before energizing the ESP

– operating at or below saturation temperature can lead to arcing inside the ESP, a safety hazard, and can cause crust to form on the collector surfaces, which will result in reduced performance; in the case of a baghouse, during startup when combusting distillate fuel oil (included in the EPA ’ s list of approved “ clean fuels ” ) resulting constituents in flue gas can foul and damage the bag material, leading to a higher risk of bag failure and reduced overall performance.

Commenter 20267 states that in the listing of exceptions to the mandatory control device operating requirement, no mention was given to ESPs or baghouses, which, like SCRs and SNCRs, must achieve the appropriate temperature before being placed in service as well as FGDs, which must operate only after the upstream PM controls are in service. Commenter asks the EPA to include the ESP and FGD Systems in the listing of the pollution control exceptions.

Commenter 20289 states that prematurely starting an ESP risks significant equipm ent degradation caused by cemented dust on the ESP collection surfaces or an explosion. Commenter states that a November 16, 2012, the EPA memo ( “ Startup and shutdown provisions ” ) appears to provide some clarity. Commenter states that when responding to co ncerns regarding minimum stable load and the efficient stable and safe operation of air pollution controls, the EPA, although concluding that petitioners have not provided data supporting this claim, suggests that operators can remain compliant by co

- firin g with clean fuel. Commenter states that by advocating co

- firing of clean fuels after startup ends as an appropriate means to achieve compliance, the EPA is recognizing the limitations of certain pollution controls and acknowledges that once startup ends, compliance is based on meeting emission limits, not work practice standards. Commenter described the startup procedures at EGUs equipped with ESPs where the ESPs cannot be brought online until certain operating conditions are attained.

Commenter 20415 sup ports refinements to the requirements for engagement of APCDs on EGUs.

Commenter states that these changes reflect the concerns raised by commenter s. Commenter states that however, two important additional refinements are needed. Commenter states that firs t, the rule should

include this clarification in italics: “ as expeditiously as possible but not before appropriate boiler

conditions are achieved and APCDs are online

. ” Commenter states that the second refinement needed regards ESP operation on coal

- fired EGUs, which is similar to ESP operation on coal

- fired ICI boilers from a safety perspective. Commenter states that specifically, there are fire and explosion hazards with energization of an ESP when unburned fuel may be present and the O 2 level in the flu e gas is high enough that the mixture can be in the flammable range. Commenter states that the EPA needs to reconsider this safety issue and revise the requirements to include ESP energization with the other controls that are to be started as expeditiously as possible rather than when solid fuel firing is first

started.

Commenter 20393 states that the EPA should note that the use of oil and coal during startup is not binary, but rather operates on a continuum. C ommenter states that under usual operating co nditions, the igniter fuel is not completely removed when coal is introduced, but remains a part of the fuel mix as the

EGU reaches proper temperatures. C ommenter states that the ESP plates become covered in an oily137

residue that decreases the effectiveness of the ESP and creates a safety risk because of potential sparking

and unstable combustion.

Commenter 20393 states that it is necessary to refrain from operating the ESP until the EGU has continuously combusted coal for a period of about 3 hours. C omment er suggests that affected coal

- fired EGUs should not be required to place their ESPs into service until coal has been continuously combusted for 3 hours and the ESPs have reached safe minimum temperatures in order to prevent fires and/or explosions within the precipi tators. Commenter maintains that the EPA has

, in fact

, previously recognized that in some facilities it is necessary to provide additional time after coal is continuously burned to safely engage an ESP. Commenter alleges that this approach is consistent wi th its 2004 Consent Decree with the EPA and the South Carolina Department of Health and Environmental Control,

which state s in paragraph 89 that:

... shall continuously operate each ESP in the

... System at all times that the Unit it serves is combusting Fos sil Fuel, except that

... need not commence operation of any ESP until the Unit that the ESP serves has continuously combusted any amount of coal or petroleum coke for a period of two hours (three hours for Units at the Winyah Plant and at the

Jefferies Plan t).

.. shall use good engineering practices for PM control at all times that the Unit is combusting Fossil Fuel.

In addition, commenter maintains that the 2003 consent decree between Virginia Electric and Power Company (VEPCO) and the EPA contains a similar provisio n in paragraph 78, which states in pertinent

part:

Commencing within 30 days after lodging of this Decree, VEPCO shall operate each ESP and baghouse within the VEPCO System to maximize PM emission reductions through the procedures established in this Paragraph. VEPCO shall (A) commence operation no later than two hours after commencement of combustion of any amount of coal in the controlled System Unit, except that this requirement shall apply to Bremo Power Station

Units 3 and 4 commencing two ho urs after cessation of oil injection to the boiler, and provided that, for all ESP

- equipped Units, “ combustion of any amount of coal ” shall not include combustion of coal that is the result of clearing out a Unit ’ s coal mills as t he Unit

is returned to ser vice.

Commenter 20393 states that the work practice requirement will not be technically feasible for many

coal

- fueled EGU s with ESPs and could pose unnecessary safety risks to the operation of the ESP. Commenter notes that early in the implementation of the CAA, the EPA issued a manual on “ Operation and Maintenance of Electrostatic Precipitators, ” which discussed the safe use of an ESP and specifically its temperature and dewpoint requirements. The manu al states:

...when and how much of the ESP should be energized is a much

- debated topic in many applications. Many believe that energization should not be attempted until the moisture dewpoint has been exceeded for several hours, and some like to wait unti l the acid dewpoint temperature has been surpassed, to avoid excessive sparking and the minimize buildup on the ESP internals. Newer, modern, power supplies, however, should be able to energize the ESP with little or no sparking, whereas older controllers probably should be138

set in manual control below the spark threshold. The concern with sticky particulate and sparking is two

- fold. At best, if the sticky particulate fuse or clinker on the plates and wires, the ESP will have to be shut down and washed out. At worst, unstable combustion could lead to unburned carbon, hydrocarbons, and CO in the ESP, which may be set afire or result in an explosion that endangers personnel and could also permanently destroy the

ESP ’ s performance potential. Substantial misalign ment can occur within an ESP as a result of a fire or explosion. Because of the tendency for an ESP to spark during startup and provide a possible ignition source, some plants have approached the explosion potential by lengthening their startup times.

Com menter indicates that it is its understanding that a lengthened startup time as discussed in the manual would include the use of both a clean fuel and coal, to get the facility up to the correct temperature to engage the ESP safely.

C ommenter 20393 urges the EPA to add ESPs to the list of APCDs (such as SNCR, SCR and dry scrubber systems) that need not begin operation until it is technically feasible and safe to do so as the same flexibility afforded these APCDs is warranted for ESPs also

. Commenter states that if the EPA decides not to make an exception for ESPs, then the work practice standard for

filterable PM emissions must be revised to accommodate as to when a coal

- fired EGU must begin to operate its ESP. C ommenter suggests that the EPA could not requ ire the operation of the

ESP until the end of “ startup ” as defined by the new proposed definition. Commenter alleges that this alternative approach could address the technical feasibility problems posed by the current work practice requirement for ESPs, pr ovided that the EPA were to make minor refinements to that new definition of startup.

Commenter 20393 disagree s that an ESP is not “ condition

- specific ” and that there are no constraints with engaging PM controls (ESPs and baghouses), wet scrubber, and sorbent injection systems (ACI and DSI) when firing coal, solid oil

- derived fuel, or residual oil in EGUs during startup and shutdown.

C ommenter states tha t the igniters in older boilers are not equipped to properly pre

- heat the ESP in a reasonable amount of time, and thus there are significant constraints to requiring their operation during the startup period.

Commenter 20390 states flue gas temperature ha s a major effect on ESPs. Commenter states if ESP voltage is energized prior to flue gas being above the acid dewpoint temperature, wet ash particles may collect on the emitting and collecting electrodes and hopper walls. Commenter states the material is

d ifficult to remove with electrode rapping, can form hard crust deposits cemented to electrodes, and fouling of electrodes causes reduced collection efficiency.

Comment 131 : Commenter 20414 asserts that not all EGU s can engage their emissions controls

devi ces, particularly ESPs, upon first generation of electricity or start of coal combustion . Commenter

states that furthermore, with regard to ESPs, it agree s with those commenter s who state that many EGU s may not be able to technically or safely engage their controls due to temperature or flow condition

limitations. Commenter states that additionally, it agree s that operating ESPs at temperatures less than temperatures recommended by the OEM could create safety risks. Commenter believes these concerns are valid, particularly with regard to ESPs in operation at many Texas EGU s, including some operated by its members. Commenter states that these concerns regarding ESPs are well documented in the record139

befor e the EPA, including by environmental lobbying organizations ( see EPA

- HQ

- OAR

- 2009

- 0234

- 17975). These comments provide that:

Some electrostatic precipitators are not turned on during startup and shutdown, because they require minimum temperature for safe o peration...The point at which the ESP can be brought on

- line is dependent on several factors. The most significant factor is inlet gas temperature which is in turn related to quantity of fuel burned, fuel quality, how long the unit has been offline, etc. T his minimum temperature is consistent with that prescribed by the control device manufacturer as a preventative measure against failure, explosive

conditions

, and to ensure long term functionality. Id., at 14. (emphasis added).

During periods of startup, shutdown etc., when exhaust gas temperatures are low and other gas properties may not be optimum (i.e., its moisture content, etc.), it is quite common for ESPs to not be energized until proper operating conditions occur. Id., at 3

- 4

of attached referenced testimony of Dr. Ron Sahu.

Based on discussions with various equipment manufacturers and review of operating manuals, there are often minimum temperature requirements for ESPs in order to avoid issues such as moisture condensation and potential damage (w hich depend on the type of fuel that is used for startup, etc.). Id. at 4. fn 2, of attached referenced testimony of Dr.

Ron Sahu.

Commenter 20419 states that one member specifically is concerned with its ability to comply with the proposed definitions of startup at its coal

- fired EGUs that burn low

- sulfur coal and use only an ESP for emission control. Commenter alleges that the ESPs at these EGUs must be de

- energized at all times when the flue gas temperature may be below the acid dew point and the ESP al so must be de

- energized during the firing of start

- up fuels, such as #2 fuel oil, until coal firing results in volatile gas concentrations that are below levels which would pose an explosive hazard in the ESP. Commenter

indicates that one ESP manufacturer recommends that the ESP remain de

- energized during startup until flue gas temperatures within the ESP remain above 200 °F for 2 hours resulting in periods during startup

and shutdown when the E GU is firing fuel while the ESP is de

- energized. Commenter stat es that, as a result, during these periods the particulate loading of the flue gas downstream of the ESP can be significantly higher than that which is observed while the ESP is in operation. Commenter states that the combination of higher particulate load ing and low flue gas flow rates results in settling of particles within the flue gas ductwork downstream of the ESP and that this settled particulate will remain in the ductwork until the EGU load is raised following startup such that the flue gas flow rat es cross certain threshold velocities upon which re

- entrainment will occur and the PM is “ swept ” into the gas stream and emitted through the stack. Commenter maintains that the exact loads/flue gas velocities that correspond

with re

- entrainment is specific to each individual EGU, but in some cases these “ duct sweeps ” may not
occur until the EGU is br ought to an operating condition at or near full load (corresponding with high flue gas velocity) and, depending on market conditions, a EGU may not reach full

- load operation within the window proposed by EPA for startup. Commenter notes that in these situa tions, “ duct sweeps ” will occur outside of the prescribed startup period. Commenter indicates that this situation may occur more frequently in the future as grid operators work to integrate the growing amount of renewable generation

into the nation ’ s grid; the use of intermittent renewable generating sources can cause additional startups, shutdowns, or low

- load operations for fossil

- fueled EGUs. Commenter maintains that the proposed140

definitions for the end of startup may not allow sufficient time for ESPs t o be put into service and reach the operating efficiencies necessary to comply with MATS and that the EPA should provide an allowance for periods of “ duct sweeps ” to be excluded from the determination of compliance with applicable MATS emission limitations

.

Commenter 20419 notes that EPA ’ s Startup TSD bases its proposed definition of the end of startup on implementation times for FGD and SCR, and does not address the startup of baghouses or ESPs. The Startup TSD, therefore, does not consider whether units employing baghouses or ESPs would be able to comply with the proposed definition of the end of startup.

Commenter 20422 states that the EPA already addressed in the final preamble the issue of ESP equipment degradation, explosions, or destruction of equip ment.

Commenter 20427 states PM limits can be met without further expansion of the startup exception

. Commenter states state

- of

- the

- art PM APCDs can be safely and effectively operated at temperatures achievable within the scope of the current work practic e standard. Commenter alleges that, although it recognizes the importance of avoiding safety risks, the operational experience of several plants suggests that these concerns are, at best, theoretical. Commenter cites the startup and shutdown minimization

p lan for four EGU s at a power plant that uses fuel oil as the startup fuel and routinely operates ESPs during startup and shutdown events. Commenter cites the facility ’ s plan :

Although the equipment is not fully effective until proper temperatures and stable conditions are reached, startup emissions are minimized by placing the electrostatic precipitator and flue gas desulfurization scrubber in service prior to the introduction of fuel to the boiler. Placing the electrostatic precipitator in service ear ly in the process provides for a reduction in particulate matter emissions...

Fuel oil is the initial heat input source used during boiler unit startup, and unit startup begins when fuel oil is introduced into the boiler. As the boiler, turbine equipment and steam temperatures rise to design values, coal mills (pulverizers) are gradually placed into service concurrently with fuel oil firing. (Generally, two pulverizers are operational during the end phase of the boiler startup process.) As steam and equipm ent temperatures
continue to rise while co

- firing on fuel oil and coal, the boiler combustion process stabilizes adequately such that fuel oil firing can cease. Startup ends no later than the point in time when flue gas temperatures to the electrostatic pr ecipitator reach a temperature of 220 °F and two coal pulverizers have been placed into service. Startup does not extend beyond 20 hours per startup period.

Commenter 20427 states the operator further notes that these procedures may be safely followed eve n in the face of contrary manufacturer ’ s recommendations. Commenter states these four EGU s have been operated in this manner since approximately 2007 without the safety and equipment difficulties hypothesized by industry commenter s, and the continued safe operation of these EGU s for years while using challenging startup fuel demonstrates the feasibility of ESP operation during startup and shutdown provided the ESP is kept clean and properly maintained. Commenter cites opacity data for these EGU s that show t he benefits of operating PM APCDs through startup, with low to no opacity exceedances, suggesting low PM emissions. Commenter cites another 900 MW EGU that is capable of energizing its141

ESP throughout, and cites a figure from a December 2012 EPA memorandum showing the ESP is energized at the beginning of oil fire (startup fuel) in the boiler. Commenter alleges that even if the EPA could tailor its standard to a particular (sub

- optimal) pollution control

– which it cannot, according to CAA sections 112(d) and 112(h)

– there is thus no practical reason that ESPs cannot be safely operated

whenever coal is used at an EGU.

Response to Comments 130 and 131 : The EPA proposed that:

Once you start firing coal, residual oil, or solid oil

- derived fuel, you must vent emissions to the main stack(s) and engage all of the applicable control devices except limestone injection in FBC EGUs, dry scrubber, SNCR, and SCR. (77 FR 71342)

Commenters have correctly interpreted that this proposed language required that ESPs be enga ged once coal, residual oil, or solid oil

- derived fuel firing was initiated. Commenters have raised a number of concerns related to operational and safety issues related to the engagement of ESPs this early in the

process.

The EPA believes that the SO 2 an d NO X analysis is appropriate for defining the end of startup because these are usually the last controls to come on line and they, therefore, serve as a proxy for the end of

startup , at which point we are confident sources will be able to accurately monit or HAP emissions . The fact that we have no HAP data is immaterial for purposes of our analysis because we believe the work practice will lead to lower HAP emissions during periods of startup and shutdown and sources do not have to comply with numeric stand ards during periods of startup and shutdown, even if they have CEMS or sorbent traps collecting data during those periods.

Although the EPA is aware of the issues noted, particularly those related to operation below the acid dew point, we had no informati on at proposal that indicated that ESPs could, or would, not be operational at coal firing (w e note the absence of claims that it is not possible to heat the ESP on clean

fuels alone or that clean fuels could not be used for a longer period )

. In fact, our technical understanding

indicated that PM controls could be and w ere engaged prior to engagement of the FGD, either to prevent contamination of the wet FGD scrubber sludge or as part of a dry FGD process. We note that in some

states, EGUs are required to place their PM APCDs in service, or have them operating, before solid fuel or residual oil may be fired . For example, the draft “ Air Pollution Control Operating Permit ; Operating Permit Renewal ” for the Carney’s Point Generating Station includes the following requirement from the State of New Jersey : 12

... No coal or #6 fuel oil may be fired until all air pollution co ntrol apparatus is in operation... ( see p. 55 of 133)

Similarly, the “ Significant Revision of Part

- 70 Source Operation Per mit ” for the Weston Plant includes the following requirements from the State of Wisconsin : 13

12 See draft “Air Pollution Control Operating Permit Operating Permit Renewal” made available for public review on October 10 , 2014, in docket ID EPA

- HQ

- OAR

- 2009

- 0234.

13 See “Significant Revision of Part

- 70 Source Operation Permit” dated September 23, 2014, in docket

ID EPA

- HQ

- OAR

- 2009

- 0234

.142

... (2) (a) The permittee shall operate an electrostatic precipitator whenever solid fuel is fired in boiler B01 in a manner that controls particulate matter emissi ons from boiler B01 so that the emission limitations in condition I.A.1.a.(1) are met. (b) The permittee shall operate an electrostatic precipitator whenever solid fuel is fired in boiler B02 in a manner that controls particulate matter emissions from boiler B02 so that the emission limitations in condition I.A.1.a.(1) are met.

.. ( see p. 1)

... (i) Place ESP in service

... (iv) Introduce coal to the combustion chamber while continuing to operate the startup fuel as the coal begins to ignite

... ( see p. 5)

Comments received on the proposed rule further reinforce the position that the PM APCDs can be operated from the beginning of solid fuel or residual oil firing , although a “ grace ” period of 1 hour may

be indicated. 14 Commenter 20275 states that “ ...it should take no more than one hour to phase in ESPs once pulverization commences. ” Commenter 20303 suggests that “ the time frame between coal combustion and all air pollution devices in operation be ‘ as soon as practicable ’ allowing a grace period

of one ho ur. ” Commenter 20269 states that “ ESPs are started when the switch to coal is made. ”

Commenter 20427 provides operational experience from a number of EGUs indicating that the safety concerns noted by industry commenters “ are, at best, theoretical. ” As not ed above, commenter cites a facility where “ the four units...routinely operate ESPs during startup and shutdown events ” and cites to the plant ’ s “ Startup and Shutdown Minimization Plan

. ” Commenter indicates that the operator of the facility “ notes that these procedures may be safely followed even in the face of contrary manufacturer ’ s recommendations. ” 15 Commenter also cites to EPA

- HQ

- OAR

- 2009

- 0234

- 20240 and the included figures 1(a) and 2(a) indicating that the ESPs are energized prior to the initiation of coal firing.

The EPA notes that there are means of operation of ESPs to mitigate adverse conditions during startup. Certain commenters cited to problems encountered when firing “ fuel oil” during startup. However, problems should not be encountered if n atural gas or number 2 fuel oil (e.g., distillate) are used. 16
Further, rapping intensity can be increased by 50 percent to limit adhesion of damp ash on electrodes. 17
Hoppers and insulators should be heated prior to commencing startup

. 18

, 19 Further, igniters can be

14 The EPA notes that the presence of a different time

- frame in a consent decree as noted by some

commenters does not indicate that quicker action is not possible, merely that the listed time was agreed upon by the parties involved in arriving at the terms o f the consent decree

. 15 “ ...commitment to fully energize the precipitator prior to bringing the unit up to operating

temperature, which is done by first combusting fuel oil followed by gradual introduction of coal, does not follow the Original Equipment Ma nufacturer (OEM) recommendation. That OEM recommendation calls for energizing the precipitator after the unit is at full operating temperature and combustion of fuel

oil has ceased. ”

16 Neundorfer. Lesson 6. ESP Operation and Maintenance. p. 6

- 5.

17 Ibid. p. 6

- 6.

18 U.S. EPA. Operation and Maintenance Manual for Electrostatic Precipitators. EPA/625/1

- 85

- 017. September 1985. p. 5

- 3.

19 Southern Environmental, Inc. Air Pollution Control Systems: Parts and Service Guide.143

redesigned or replaced to accommodate additional clean fuel so as to maximize clean fuel use during

startup. 20

The EPA believes that one commenter is incorrect in stating that by “advocating co

- firing of clean fuels after startup ends as an appropriate means to achieve compliance, the EPA is recognizing the limitations of certain pollution controls” and maintains that the best performing sources can not achieve the limit at the end of startup with a 30

- day rolling average. However, we recogniz e that other sources may want an additional compliance margin because of concerns about their ability to comply because it may be a more cost effective approach than modifying the facility to comply with the work practice in some other

manner

. We continue to believe that sources will be able to engage and operate their controls to comply with the standards at the end of startup, and that sources can make physical and or operational changes at the facility to ensure compliance at the end of startup

.

As note d elsewhere in this document, the EPA believes it appropriate to base its startup/shutdown work practices on those practices employed by the better performers. As the above information indicates that ESPs can be energized within 1 hour of coal firing being started , we are finalizing that ESPs must be engaged within 1 hour of starting to fire coal, residual oil, or solid oil

- derived fuel. We believe any reduced efficiency of the PM control when first engaged will be offset by the continued use of clean fuel and that the efficiency of these ESPs increases quickly with increased temps.

A s noted elsewhere in this document, we recognize that there may be very limited circumstances that compel some alternative approach for a specific EGU. Sources that can demonstrate that their EGU has

a documented manufacturer

- identified safety issue that cannot be resolved should seek an alternative compliance method consistent with 40 CFR 63.6(g). In its request for the case

- by

- case determination, the EGU must provide do cumentation that demonstrates that it is not technically feasible to bring the PM control device on line safely using clean fuels alone, and explains what other measure the source will take to ensure comparable HAP emissions to those required under the fin al work practice.

Comment 13 2 : Commenter 20411 states that there is continuing concern regarding how the MATS startup requirements will apply to EGU s that operate a baghouse. Commenter states that previous reconsiderations have left in place the work prac tice requirement that baghouses and some other APCDs must be in use as soon as any coal is burned in the boiler. Commenter states that however, this requirement is neither realistic nor consistent with equipment manufacturers ’ specified operating procedure s. Commenter states that this is especially the case for many older or smaller coal

- fueled boilers that are not able to achieve the correct temperature for the operation of a baghouse while using the igniter to burn a “ clean fuel ” ( e.g., natural gas ) , as i s required under the MATS startup work practice

standards.

Commenter 20411 appreciates the EPA ’ s reconsideration of the startup definition that would give coal

fired EGUs with baghouses more flexibility in operating the baghouses during startup periods.

Commenter states that although the EPA is asking for comments on changing the definition of startup as

20 The EPA notes that commenters have also cited to the EPA ESP manual but would note that although some practices have not changed in the intervening 30 years (e.g., heating of insulators and hoppers), other practices have changed (e.g., time of energizatio n) as indicated by the references to ESPs that can be, and are being, engaged at first firing of coal, residual oil, or solid oil

- derived fuel.144

“ occurring at 25 percent of nameplate capacity plus 3 hours or the start of electricity generation plus 6 hours, whichever comes first, ” commenter believes that defining startup as on ly occurring at 25 percent of nameplate capacity plus 3 hours would provide coal

- fired EGUs with baghouses sufficient operational flexibility to be able to operate the baghouses during startup safely and in a manner

consistent with manufacturers ’ specified operating procedures. Commenter recommends that during startup if the boiler and/or turbine generator “ trips ” and is no longer generating electricity that the startup process and time periods begin anew when the EGU begins generating electricity again.

C ommenters 20389 and 20390 state that fabric filter life is shortened by acid deposition due to below dew point temperature . Commenters 20389, 20390, and 20410 note that fabric filters can be permanently blinded by low temperature carbon combustion residuals , requiring filter replacement after

every startup.

For FF used for PM control, Commenter 20390 states there are no minimum flow or temperature requirements prior to operation . Commenter states bags require pre

- coating of material to protect them

from cor rosive attack during startup, either with sorbent from an upstream DSI or CDS system or per supplier ’ s recommendations. Commenter also notes that specific manufacturers may limit the number of compartments in service at reduced temperature. Commenter state s bags have a maximum continuous temperature limit of approximately 375 ° F depending on the bag medium. Commenter states a bypass can be included for high temperature excursions.

For SDA and FF in combination, Commenter 20390 states the potential for acid condensation in the FF

can be greatly reduced with the startup procedure requiring the SDA be in operation at the same time as

the FF. Commenter states if the temperature is too low entering the SDA, lime slurry may not dry in the

S DA and will coat the walls of the SDA and carryover moist reagent and ash to blind the filter bags. Commenter reiterated the importance of multiple APCDs being treated as an integrated system with not only the boiler flue gas characteristics in mind but al so the effect on APCD upstream of each APCD

system.

Commenter 20390 indicates that most SDA and CDS systems have fabric filters as the PM control and that particulate removal can be maintained during startup and shutdown operating periods.

Commenter 2042 7 states that baghouses experience no difficulties during startup, are designed to be operated at all time, and cites an EPRI survey in 2010 that concluded baghouses are almost universally not bypassed during startup and experience no significant difficult ies as a result of consistent use during startup. Commenter states the concerns raised by industry (condensation and acid corrosion) are applicable, if at all, to only a limited number of plants using older, suboptimal APCDs and do not justify

further weak ening of the rule. Commenter states that PM APCDs, igniters, and supply lines can be upgraded for those rare plants with concerns.

Commenter 2042 2 states that there is no justification for not operating baghouses during SS . Commenter

cites to a 2010 EPRI “ Power Plant Baghouse Survey ” in which EPRI itself notes the vast majority of baghouses at a wide range of EGU s in its survey do not need to be bypassed during startup. In addition,

commenter states the CAMD indicates 166 EGUs, over 12 percent of all coal

- fired EGU s, have already installed baghouses or FF; as these are more effective in controlling PM immediately after startup and145

during normal operations, the EPA has little reason to weaken emission limits to accommodate outdated

and ineffective ESPs.

Com menter 20433 provides a rebuttal that the 2010 EPRI survey cited involved baghouses at only about

19 EGU s, all of which employed a specific type of baghouse known as a pulse

- jet fabric filter (PJFF) baghouse. Commenter 20433 maintains that Commenter 20422 has provided no reason to extrapolate from that study the broad assertion that EGU owners/operators have “ no justification for failing to operate baghouses. ” Commenter 20433 indicates that from practical experience, EGU owners and operators know that opera tion during startup can damage baghouses, whose fabric filters are made of

woven or felted fabric. Commenter states that, f or example, baghouse operation during startup on oil is

detrimental to its operation. It is impossible to ignite and maintain a stabl e flame on fuel oil without initially producing unburned carbon. These sticky particles can imbed in, and thereby damage, the fabric filters. If these particles imbed, gas pressure drop will increase, the bag ’ s life will be reduced, and there will be poor PM capture. The degraded performance will persist until replacement.

Commenter 20419 states that startups of baghouses are temperature

- dependent, making startup times different at every EGU. For example, one of commenter ’ s members owns a coal

- fired EGU that operates a baghouse for particulate control during periods of normal operation. Commenter notes that the flue gas must reach a certain minimum temperature before the baghouse is put into service to prevent acid corrosion from damaging the baghouse and causing it to fail and that baghouses also may fail if there is moisture carryover from the scrubber (moisture carryover, which can occur when the scrubber is put into service too early, results in bag blinding where the flue gas clogs the fabric pores). Commenter maintains that the bags then must be replaced because delta pressure (DP) increases with blinded bags, which can lead to bag failures and increased emissions; high DP also may require operating the EGU at reduced loads to decrease pressure.

Comm enter 20421 states that the combustion of distillate oil in the EGU (for startup) would require, per

the manufacturer ’ s recommendation, pre

- coating of baghouse bags to minimize the possibility of irreversibly blinding (or plugging) the filter bags by volat ile organic compounds, which are byproducts

of distillate combustion. Commenter alleges that preliminary analysis shows that bag pre

- coating may impact the EGU ’ s ability to meet the dispatch response times that are specified in their Power Purchase Agreeme nts.

Response to Comment 132 : Similar to ESPs, the EPA ’ s February 2012 final rule and the November 2012 proposed rule included language that required fabric filters to be engaged once coal, residual oil, or

solid oil

- derived fuel firing was initiated. Com menters raised a number of concerns related to operational and safety issues related to the engagement of fabric filters this early in the process.

The EPA is aware of the issues noted, particularly those related to operation below the acid dew point. Comments received on the proposed rule further indicate that fabric filters, like ESPs, may be operated through startup after coal combustion as long as minimum temperature s are reached

. We believe that sources can use clean fuels to bring the flue gas to appropriate temperatures and the information in the146

record supports that determination. 21 Furthermore, the information and data submitted by the

commente rs does not support claims to the contrary or otherwise cause us to question our conclusions.

As noted in its comments above, Commenter 20390 indicates that there are means available for ameliorating the impacts of operation of a fabric filter below the a cid dew point (e.g., pre

- coating of the bags; required operation of the SDA, DSI, or CDS system during startup) and that particulate control can be maintained during startup

. The EPA agrees that these practices , along with maximization of clean fuel use, c an be used to minimize impact s on the fabric filter and reduce HAP emissions during startup. Further, Commenter s 20422 and 20427 note that industry information (available through EPRI) indicates that fabric filters may be operated during periods of startup. Further, information available from industry indicates that the recent trend is toward no use of bypass on startup with fabric filters. 22

Therefore, as noted elsewhere in this document, the EPA believes it appropriate to base its SS work practices on those practices employed by the better perform ing EGUs . As the above information indicates that fabric filters can be operated during periods of startup, we are finalizing that fabric filters must be engaged within 1 hour of starting to fire coal, residual oil, or solid oil

- derived fuel. The 1

- hour period is designed to ensure that all sources can safely engage the PM controls, though many sour ces may need to increase their clean fuel capacity or modify their startup burners or take other action to comply.

The EPA agrees with one commenter that if the boiler and/or turbine generator “trips” during a startup period and is no longer generating electricity that the startup process and time periods begin anew when the EGU begins generating electricity again. However, if electricity generation began before the “trip,” the shutdown work practices would be applicable. The work practice requirement of engaging and operating the PM APCDs within 1 hour of coal, residual oil, or solid oil

- derived fuel firing remains in effect regardless of whether electricity is generated.

3. 6 Selective catalytic reduction

- SCR

Comment 13 3 : Commenter 20401 notes that t he EPA ’ s definition of startup does not take into account operating requirements, such as specific minimum temperature conditions that are typically not met until well after electric generation has already begun, the omission of which presents a risk that a utility would be forced to run an SCR below the minimum operating temperature to avoid violating emissions limitations, reducing the efficiency of the SCR and causing substantial damage to the SCR and other associated equipment. Commenter notes that its specifications show that the minimum operating temperature for its planned SCR will be at least 600 °F.

21 For example, Commenter 20390 states that “[a]t some plants the startup fuel is co

- fired and continues

till 1/2 load and at other facilities it continues till 2/3 load. The capacity of each plant is different as to its ability to burn an auxiliary or startup fuel. Some plants only have igniters and can burn startup fuel only to about 10% of the design heat input wh ile other plants have fuel burners that can burn auxiliary fuel up

to full load.” Further, Commenter 20420 not ed that it s manufacturer ’ s startup procedures specified that

the b aghouses were to be “ in opera tion throughout startup process ” ( see EPA

- HQ

- OAR

- 2009

- 0234

- 20420, Attachment 3).

22 Widico, Mike. KC Cottrell, Inc. ICAC Technology Training Workshop: Fabric Filters, July 17, 2014.147

Commenters 20390 and 20408 state that most recent SCR retrofits (i.e., since 2000) have no bypass for startup or shutdown (some ozone season SCRs do ha ve bypass) and the flue gas must flow through the entire air pollution control train at all times

– these inline systems bring certain startup operating issues with them along with certain environmental benefits). Commenters state SCR cannot function until a minimum flue gas temperature is reached

– in general ammonia can only be injected when flue gas is greater than 600°F, and is affected by sulfur content, flue gas moisture, and ammonia content. Commenter 20408 notes that the conditions for a fully funct ioning SCR system will occur well beyond the time that electricity or useful thermal energy is initially achieved. Commenter 20390 indicates ammonium bisulfate is formed at lower temperatures and that shutdown must follow the same critical temperature shut off of ammonia.

Commenter 20390 provides several graphs showing temperature profiles for warm and cold startups. Commenter states that one graph shows a warm startup where the SCR can be brought into service approximately 15 hours after initial firing of startup fuel and approximately 3 hours after the plant achieved 25 percent of nameplate capacity, and another graph shows the same warm startup, the SCR could be brought into service approximately 3 hours after the EGU was on coal, exceeding 6 hours after the start of electricity generation. Commenter indicates this example shows that even for warm startups, it is marginal that the SCR can be placed into service.

Commenter 20390 states one graph shows a cold startup following a long outage where critical

t emperature is not reached in the SCR for 60 to 90 hours after initial startup on auxiliary fuel, and this occurs at 60 percent load, long after the plant changed to coal firing and connected to the grid. Commenter states the SCR could be brought into servi ce approximately 93 hours after initial oil firing and approximately 13 hours after achieving 25 percent of nameplate capacity.

Commenter 20390 states that an economizer bypass can be added to most coal

- fired plants using SCR

and can reduce the time to r each critical temperature. Commenter indicates hot water bypass and a “ flue gas slipstream bypass ” may be used by most (but not all) boilers, although these technologies decrease boiler efficiency and add capital costs. In addition, Commenter states altern ative boiler combustion modifications can minimize NOx emissions during startup and shutdown, such as overfire air (OFA) and/or low NOx burners, which also requires increased capital costs and the impact on boiler efficiency is dependent on system design a nd fuel burned

.

Commenter 20425 states that the time frame to bring an SCR in service can vary based on the manufacturer, design and configuration. Commenter notes that, as directed by the manufactures instructions and specification, many SCR systems are not placed into service until substantial startup oil fire has ceased and proper temperatures at the SCR inlet have been achieved. Commenter maintains that this is per the manufacture ’ s direction to avoid blinding/fouling of the catalyst and also to avoid the potential of a fire within the catalyst. Commenter states that the time it takes to bring the SCR in service with proper ammonia flow can be 10

- 12 hours after the EGU is online or 8

- 10 hours after 25 percent of nameplate capacity is reached.

Respo nse to Comment 133 : See responses to both the legal and technical issues raised in these comments elsewhere in this RTC and the preamble to the final rule

. The EPA also notes that in addition to the practice noted by commenter as a means to reduce the warm

- up time, clean fuel use can be

increased

. The goal of our analysis was to identify the approximate time it took, on average, to initiate148

operation of APCDs to determine an appropriate end to startup for purposes of defining the end of the work practice standard. The goal was not to seek the time it took for APCDs at all EGUs to become fully operational. The EPA does not believe that full functionality of an SCR is required for the purposes of startup under the MATS rule or that the longest times should govern . As noted in the R evised TSD,

the EPA used an emission decline threshold of 20 percent and found that the average of the best performing 12 percent of E GUs initiate NO X control within 4 hours after the start of electricity generation. APCDs do not need to be fully functional at the end of startup. If an EGU is concerned about the efficiency of its controls at that time, it may combust clean fuels alone fo r a longer period to warm the system prior to generating electricity and/or continue to maximize the use of clean fuels after the end of startup to minimize emissions while the controls reach full capacity

.

3. 7 Selective noncatalytic reduction

- SNCR

Comment 13 4 : Commenter 20390 states ammonia is injected for SNCR at flue gas temperatures of

1600 to 1800 ° F, and injection at lower temperatures can result in ammonia slip, and injection at higher temperatures produces less efficient NOx reduction. Commen ter states typically boiler load is used as the control parameter because it is correlated with the proper temperature range, and SNCR is designed for a specific minimum boiler load operating condition. Commenter states SNCR control is often

interlocked so that the SNCR will not be allowed to operate until it reaches the defined minimum boiler load (i.e., minimum temperature). Commenter states that high CO levels in the flue gas in the SNCR temperature range can have a significant effect on SNCR performance and also can affect the effective temperature range and that operating outside the defined temperature range may lead to ammonia slip, which can be detrimental to downstream components such as the air preheater, and PM and FGD

APCDs . Commenter states that on shutdown, SNCR are prevented from operating below the low boiler load/minimum operating temperature setpoint. Commenter states that 25 percent of nameplate capacity may not provide sufficient temperature for SNCR operation, 25 percent is not a typ ical low boiler load where SNCR is effective in reducing NOx, and notes that often 30 to 40 percent is typical for SNCR operation but is unit

- specific and based on furnace temperatures. Commenter states furnace temperature is the key parameter and boiler l oad is only applicable in terms of how it relates to furnace temperature.

Response to Comment 134: See responses to both the legal and technical issues raised in these comments elsewhere in this RTC and the preamble to the final rule. There are no require ments for engagement of SNCR controls. O perators do not have to engage any controls within a specified time period (other than PM controls which must be engaged within 1 hour of firing of coal, residual oil, or

solid oil

- derived fuel ); rather, they are onl y responsible for meeting the emission limits no later than 4 hours after electricity generation using any approach the source deems appropriate . The use of clean fuels to the maximum extent possible will assist in heating the system to allow the APCD equi pment to get to operating temperatures. Further, the EPA is unaware that SNCR has any effect on HAP emissions. Therefore, operators should be able to operate SNCR controls in the manner that best meets the EGU ’s NOx emission requirements.

3. 8 Activated sorbent injection (ACI)/Hg control

Comment 1 35 : Commenter 20427 states the Hg limit can be met without further expansion of the startup exception

. Commenter states that ACI provides effective control at low temperatures and loads, and in fact, is enhanced at lower temperatures. Commenter states industry has not provided any support149

for the proposition that ACI is ineffective at lower temperatures, and the EPA has pr eviously concluded that ACI is consistent across a variety of operating conditions ( cites EPA

- HQ

- OAR

- 2009

- 0234

- 20223 ).

Commenter notes that industry concerns for startup constraints on some SCR APCDs (must bypass to avoid catalyst contamination and gradual ly heat over 12 hours) and duct fallout can be addressed by adding ACI to avoid catalyst contamination and by controlling sorbent size (i.e., finer

- sized), injection rate, and location, respectively. Commenter further notes the startup constraints for some SCR is only a

concern for EGU s relying on co

- benefit of NOx to avoid the reasonable expenses associated with ACI.

Commenter 20433 rebuts by saying nowhere in the docket entry cited by Commenter 20427 does the EPA discuss ACI, much less assert that ACI is “ remarkably consistent ” in its operation under differing conditions. Moreover, there are practical limitations to u sing ACI at low loads because the sorbent simply cannot be entrained in the exhaust gas stream without adequate flue gas velocity. Further, Commenter 20433 notes that, as explained in EPA

- HQ

- OAR

- 2009

- 0234

- 20180, sorbent injection, whether ACI or DSI, can o nly begin when a sufficiently high gas flow rate is achieved in the duct, which typically occurs at about 40 percent load. Commenter 20433 alleges that if injected too soon, the sorbent will not be properly entrained in the gas stream and instead will sett le to the bottom of the duct, where with enough accumulation of material over a long enough period of time, the accumulated additional weight could cause structural damage and lead to duct collapse. Commenter 20433 notes that the sorbents that may be used for acid gas removal, such as Trona, may present worse settling problems ( e.g. , result in accumulation on the ESP ’ s inlet perforated plates) than activated carbon because of their higher density. More importantly, Commenter 20433 states that premature use of ACI also could cause fire, including in the air heaters and ESP hoppers.

Commenter 20424 believes that the standards should also be revised to allow the recognition of the constraints of application of ACI, which should be revised to allow the start of ACI after appropriate temperature is reached.

Commenter 20390 states activated carbon generally performs better at lower temperature. Commenter

notes there is a risk of fire if carbon stands for long periods in a hot environment because oxidation

reacti ons occur on the surface of activated carbon which generates small amounts of heat

– if the carbon is very concentrated, and kept hot a long time (and carbon is a great insulator) enough heat can be built up to lead to smoldering occurring . Commenter state s activated carbon should not be injected in startup

or shutdown conditions while oil

- firing.

Comment 136: Commenter 20408 states that if ACI is injected into the flue gas before the EGU reaches stable load and the associated ESP is operating properly, there is a chance of fires starting in the ESP.

Commenter indicates that ACI should be started only after coal has been introduced t o the boiler and is burning in a stable manner and that the conditions for a fully functioning ACI system will occur well beyond the time that electricity or useful thermal energy is initially achieved. Therefore, commenter
notes that ACI injection is not required under its permits until the EGU reaches stable load defined for the EGU. Because ACI will be one of the major control technologies used for Hg control, commenter
believes that the EPA needs to consider this when defining when startup ends.

Respon se to Comments 135 and 136 : The final work practice standards do not specify when ACI injection must begin. The only specific requirement is that PM controls must be engaged within 1 hour of the introduction of coal or other primary fuel. Under the final r equirements the operator would be150

responsible for measuring HAP emissions for compliance with the numerical limits within 4 hours after generation of electricity or production of thermal energy. At the end of startup (4 hours after generation)

, the PM cont rol device (e.g., an ESP or FF) would have be en in operation for potentially up to 4 hours,

and we believe that w ill be more than enough time for the PM controls to be fully or nearly fully operational before the introduction of activated carbon will be necessary for compliance with the

numerical Hg limit

. In any case, we believe that HAP emissions, including Hg emissions, will be as low if not lower during startup and shutdown due to the final work practice as they will be during all other perio ds

.

3

. 9 Limestone injection

Summary of Comments Received Following November 30, 2012, Proposal

Comment 1 37 : Commenter 2 0282 notes that in an FBC , if limestone is added too early in the startup sequence, the flame will be extinguished. Commenter states that FBUs that inject limestone must reach a minimum of approximately 1500 ° F for the limestone to calcine, and thus become effective at reducing acid gases.

Commenter 2 0285 endorsed the EPA ’ s proposal to revise the startup and shutdown provisions applic able to EGUs that use FBC and that inject limestone for acid gas control, in recognition that such standards should reflect the unique operating conditions of FBCs and increase operational flexibility for

FBC EGUs

.

Commenter 2 0295 states that the E P A ’ s proposed work practice standards regarding limestone injection would prematurely start air pollution control systems, contrary to manufacturer specifications and risking safety concerns.

Commenter 2 0308 notes that where a thiosorbic lime scrubber is used, the chemistry of this system requires time to establish a seed crystal bed to support effective removal. Commenter states that until this seed crystal bed is established resulting in sufficient surface area, the reaction will not efficiently remove acid g ases.

Response to Comment 1 37 : The EPA understands that operational characteristics (including temperature) of APCD s used at power plants depend on manufacturer ’ s design and plant operating conditions and

, therefore

, are site

- specific. Taking the comments into consideration,

the final rule requires EGU source owners and operators to comply with th e numeric MATS standards 4 hours after electricity generation. The rule requires sources to vent emissions to the

main stac k(s) when firing coal, solid oil

- derived fuel, or residual oil in the EGU during startup or

shutdown , and to engage and operate the PM control device (s) within 1 hour of firing those fuels. Aside from the PM control device, sources are required to operate their control devices when necessary to comply with MATS or other applicable standards.

The EPA believes its final requirements for operation of the PM APCD s during periods of startup and shutdown are practical and will not cause any safety risks. The EPA also believes th is requirement in conjunction with the final definitions of startup and shutdown and clean fuels requirement will ensure

that EGU HAP emissions are minimized during s tartup and EGUs will be able to comply with the151

numerical standards appli cable in periods other than startup and shutdown periods. However, as noted elsewhere in this document, we recognize that there may be very limited circumstances that compel some alternative approach for a specific EGU. Sources that can demonstrate that th eir EGU has a

documented manufacturer

- identified safety issue that cannot be resolved should seek an alternative compliance method consistent with 40 CFR 63.6(g). In its request for the case

- by

- case determination, the EGU must provide documentation that de monstrates that it is not technically feasible to bring the PM control device on line safely using clean fuels alone, and explains what other measure the source will take to ensure comparable HAP emissions to those required under the final work practice.

Summary of Comments Received Following June 25, 2013, Reopening of Public Comment Period

Comment 1 38 : Commenter 20397 states injection of lime cannot be safely initiated until the proper flue gas flow is achieved, which enhances mixing and contact of the dry sorbent with the flue gas and ensures lime does not drop out and lay in the flue gas ducts. Commenter states duct deposition initiates corrosion on duct surfaces, and duct support structure is not designed for large physical load that may

result if the sorbent is added prior to reaching a gas velocity that suspends the material.

Response to Comment 138 : See responses to both the legal and technical issues raised in these comments elsewhere in this RTC and the preamble to the final rule. The requirement to maximize the use of clean fuels will assist in heating the APCD equipment to operating temperatures while minimizing HAP emissions. The operator will be accountable for emissions for compliance purposes starting 4 hours after generation of electricity. There is no requirement that any APCD controls be engaged

– other than the PM controls, which must be engaged within 1 hour of firing coal, residual oil, or solid oil

- derived fuel

– only that the numerical emission

limits be met not later than 4 hours aft er generation of electricity.

3 .1 0 Shutdown

Summary of Comments Received Following November 30, 2012, Proposal

Comment 1 39 : Commenter 2 029 7 states that the use of the word “ expeditiously ” in Section 4 of Table

3 in s ubpart UUUUU does not seem to convey the proper requirement for continuing operation of the control equipment though the end of a shutdown. Commenter suggests language similar to: “ You must operate your limestone injection in FBC EGUs, dry scrubber, SNCR, and SCR systems as expeditiously as possible long as practicable... ”

Response to Comment 1 39 : The EPA thanks the commenter and has made appropriate edits to Section

4 of Table 3 in subpart UUUUU.

Summary of Comments Received Following June 25, 2013, Reopening of Public Comment Period

Comment 14 0 : Commenter 20390 states that during normal shutdown, operators follow a set of procedures in which different APCDs are removed from service based on manufacturer recommendations, normally based on flue gas te mperatures, and coal firing is reduced until auxiliary fuel can be brought into service. Commenter indicates that in an emergency shutdown or trip, ammonia to SCR or SNCR would be shut off immediately, water or slurry to a SDA, CDS, or NIDS would be152

discon tinued, but slurry or water would continue to a wet FGD to protect FRP/plastic components.

Commenter state s that during normal shutdown

, an SCR may be taken out of service 2.5 hours prior to

shutdown of the ( boiler ) EGU ; however

, how long the SCR may remai n in service depends on system design.

Commenter 20390 provides a summary table of typical shutdown procedures for multiple APCDs ( see Table 2 )

.

Table 2. Typical Shutdown Procedures ( Commenter 20390 )

.

APC Equipment Normal Shutdown Emergency shutdown

SCR Discontinue ammonia feed at minimum temperature Discontinue ammonia feed immediately, emissions no longer

controlled

SNCR Discontinue ammonia feed at minimum temperature Discontinue ammonia feed immediately, emissions no longer

controlled

Wet FGD System can remain in service during shutdown. The number of recycle pumps in service should be limited to

minimize blow back into inlet

ductwork at reduced flow System can remain in service, number of recycle pumps in service

should be limited to minimize blow

back into inlet ductwork at reduced flow. Emergency quench available to cool flue gas in the event of a blackout situation. If emergency quench is required, emissions no longer controlled

Spray dryer/baghouse Discontinue lime slurry feed at minimum temperature and flue gas

flow Discontinue lime slurry feed immediately, emissions no longer

controlled

CDS/baghouse Discontinue water feed at minimum temperature and discontinue lime feed at minimum flue gas flow Discontinue water feed immediately followed by lime feed, emissions no longer controlled

DSI or carbon injection system Discontinue sorbent feed at minimum flue gas flow

Discontinue Trona and SBS feed at minimum temperature. Shut down carbon injection when firing oil. Discontinue sorbent injection immediately, emissions no longer

controlled

Baghouse System can remain in service during shutdown. May have to place compartments out of service based on flow and or temperature dependent

manufacturers rec ommendations System goes into standby

ESP System can remain in service during shutdown until flue gas temperature

is reduced to 250 ° F System goes into standby153

Comment 14 1 : Commenter 20390 states that the low flue gas temperature problems cited for startups also occur during shutdown.

Response to Comments 140 and 141 : The EPA believes that some of the conditions noted by

commenter may be considered “malfunctions” and addressed under th e final rule provisions applicable

to malfunctions

. We believe that the provisions of the final rule that require that emissions must be vented to the main stack(s) w hile firing coal, residual oil, or solid oil

- derived fuel during shutdown, and require all applicable control devices to be operated as long as practicable throughout the shutdown period address commenter’s concerns and minimize HAP emissions. I n addition to the fuel used prior to initiation of shutdown, if another fuel must be used to support the shutdown process, that additional fuel

must be one or a combination of the clean fuels defined in 40 CFR 63.10042 and must be used to the maximum extent possible.

3 .1 1 Other

Summary of Comments Received Following November 30, 2012, Proposal

Comment 14 2 : Commenter 2 027 1 states that it assume s that the work practice standards in Table 3 to

s ubpart UUUUU of Part 63 for coal

- fired, liquid oil

- fired, or solid oil

- derived fuel

- fired EGU during startup may not delay the startup of an APCD longer than would be needed to comply with a standard made applicable to the EGU by a permit limit or a rule other than s ubpart UUUUU. Commenter states that if this assumption is correct , the EPA should clarify by specifically stating “ a standard made applicable to the EGU by a permit limit or a rule other than this Subpart. ”

Response to Comment 14 2 : The EPA has revised Sections 3 and 4 of Table 3 in subpart UUUUU.

Comment 14 3 : Commenter 2 030 5 states that the proposal to allow plant operators to start “ limestone injection in FGC EGUs, dry scrubbers, SNCRs, and SCRs as expeditiously as possible, ” is sufficiently vague as to be unenforceable. Commenter recommends defining temperature thresholds as part of the work practice standard.

Response to Comment 14 3 : Operational char acteristics (including temperature) of APCD used at power plants depend on manufacturer ’ s design and plant operating conditions. Consequently,

these characteristics are site

- specific and

, therefore

, the EPA does not think it appropriate to prescribe broadl y applicable temperature thresholds.

The EPA maintains that the final requirements for operation of EGUs and attendant APCD s during periods of startup and shutdown are practical and will not cause any safety risks. The EPA also believes these requirement s in conjunction with the final definitions of startup and shutdown periods are

enforceable because of parameter and other operational data collected during these periods that will provide assurances that sources are complying with the work practice requirements

.

Comment 14 4 : Commenter 2 030 2 agreed with work practice standards that require EGU source owners and operators to operate all control devices necessary to meet the operating standards that apply at all other times under the final rule (with t he exception of limestone injection in FBC EGUs, dry scrubbers, SNCRs, and SCRs). Commenter agreed that that owners and operators of EGUs are responsible for154

starting limestone injection in FBC EGUs, dry scrubbers, SNCRs, and SCRs as expeditiously as possi ble, but, in any case, when necessary to comply with other standards applicable to the source that require operation of those control devices.

Response to Comment 14 4 : Th is comment requires no response

.

4.0 WORK PRACTICE STANDARDS: TREATMENT OF IGCC

Summary of Comments Received Following November 30, 2012, Proposal

Comment 145 : Commenter s 20281 and 20400 observe that for IGCC EGU s, the EPA ’ s definition of startup and shutdown is based on the transition from firing clean fuels to syngas in the CT powe r block.

Commenter notes that because the EPA ’ s definition of the affected IGCC source excludes the gasification system, the startup and shutdown definitions will reasonably accommodate IGCC operation.

Commenter recommends that the EPA make no changes to e ither the definition of the affected source, or the startup and shutdown definitions for an IGCC.

Comment 1 46 : Commenter 2 024 3 supports the proposed revision of Table 3 to 40 CFR Part 63, s ubpart

UUUUU

, as it relates to the startup and shutdown provisions when using syngas. Commenter notes that the support is premised on the option of either flaring or routing to duct burners remains the option of the permittee and not the permit writer or regulator. Com menter states that it is important that flaring remain an option for routine startups and shutdowns and as a viable option for non

- routine events such

as EGU “ trips ” when the CT cannot combust syngas.

Response to Comment s 145 and 146 : After considering the comments on the need for flaring at IGCC EGUs, the EPA is providing both options, use of flaring or duct burners, for handling of syngas not

combusted in the turbine during periods of startup and shutdown. The EPA believes that this w ill provide flexibility to owner/operators of IGCC EGUs to choose one or both of the options subject to operational constraints and economics at their IGCC EGU s.

Comment 1 47 : Commenters 2 0281 and 2028 2 state that the work practice requirements proposed by the

EPA are outside the scope of the MATS rule ’ s reach and therefore should be stricken. Commenter s note that the definition of IGCC in the MATS rule does not include the gasification system. Commenter s state that the EPA cannot therefore impose work practice requirements on the gasifier, which is not subject to the rule in the first place.

Response to Comment 147 : The EPA disagrees with the commenter that EPA is imposing a work practice on the IGCC gas ifier, so we need no t address whether EPA agrees with the conclusion that such units could not be regulated under this rule. Instead, the work practice standard requires the use of clean fuels during startup. If the IGCC operator wants to use its syngas as a startup fuel, it must ensure that such gas is compliant with the clean fuels definition or startup on a clean fuel as defined in the final rule.

Comment 1 48 : Commenter 2 028 2 states that if the gasification system were subject to the startup and shutdown provisions, the regulatory language should retain both alternatives for meeting the work practice requirements : the owner/operator could either (1) flare syngas, or (2) route the syn gas to the155

duct burners, and then to the heat recovery system generator. Commenter notes that the flaring option is especially critical as the re

- routing option can only be used by IGCC EGUs under limited circumstances.

Response to Comment 1 47 : The EPA is finalizing both alternatives. See the response above.

Comment 1 48 : Commenter 2 028 1 states that the proposed new requirements for IGCC EGUs for handling syngas that is not fired in the CT are not necessary.

Response to Comment 1 48 : From the comments, the EPA understands that generally IGCC designs incorporate provisions for flaring of syngas not fired in the turbine. Because syngas may contain HAP compounds, to minimize HAP emissions during periods of startup and shutdown, the EPA i s codifying requirements for handling syngas not combusted in the turbine during these periods.

Summary of Comments Received Following June 25, 2013, Reopening of Public Comment Period

4 .1 Option 1 Flares

Summary of Comments Received Following November 30, 2012, Proposal

Comment 1 49 : Commenter 2 028 2 states that the ability to flare syngas is an engineering design aspect of the IGCC gasification system, and is a permitted form of emissions under current Title V permits.

Commenter provides discussion about safety reasons for the use of flares.

Response to Comment 1 49 : The EPA is finalizing this option.

Comment 15 0 : Commenters 2 0281 and 2028 2 responded to the EPA ’ s request for comments on the need to flare unfired syngas and if unfired syngas could be routed into the system for all IGCC EGUs.

Commenter states that the language could be read to suggest that syngas could be routed to the gasifier

and combusted there. Commenter states that the syngas lacks sufficient pressure for re

- injection and the gasifier is a once

- through system, which does not support re

- routing of the syngas.

Response to Comment 15 0 : The EPA is now aware that there are technical reasons why it may not be possible to route unfired syngas back to the system (gasifier) at IGCC EGUs . These reasons include the

fact that because the gasifier operates at high pressures, the oxygen, coal solution

, and startup natural gas must be pressurized before they can be injected into the gasifier. Once the syngas leaves the gasifier

and enters the clean

- up system, it decreases in pressure and would have to be re

- pressurized before it could be routed back into the gasifier. IGCC units have no provision for doing thi s. In addition , a gasifier is designed as a “once through” system. Gasifiers need to have a constant flow of material into and out of the system. Routing all the syngas back into the gasifier would be analogous to taking the tail pipe of an automobile and routing it back into the air intake. Before long the CO 2 will accumulate to levels high enough so that the automobile’s engine would stall. In the case of an IGCC, the gasification process will be extinguished

. See

, e.g. , EPA

- HQ

- OAR

- 2009

- 0234

- 20400. As such, the EPA is not requiring routing of unfired syngas back to the gasifier in the final rule.

Comment 15 1 : Commenter 2 028 1 states that if the EPA were to impose any additional requirements for syngas, these requirements must allow sources to flare for a number of reasons with safety being the156

most important. Commenter provides discussion that the flaring step of a n IGCC startup is relatively

short and ordinarily last less than 2 hours, and only clean gas is flared, thus, emissions are low.

Commenter states that i t is technically infeasible to require syngas not used in the CT to only be used in

duct burners

.

Commenters 2 0281 and 2028 2 note that fla ring is a required practice for safety reasons, and is permitted

under facilities ’ Title V operating permits.

Commenter 2 029 9 states that IGCC plants have and will continue to require flare stacks for the safe and orderly disposition of syngas such as during infrequent but potential process malfunctions, rapid disposition of unused sweet syngas that is necessary upon gas turbine trips, or for excess syngas trim during rapid load reductions.

Response to Comment 15 1 : The EPA notes that it is providing both options, use of flaring or duct burners, for handling of syngas not combusted in turbine during periods of startup and shutdown. The EPA believes that this will provide flexibility to owner/operators of IGCC EGUs to choose one or both of the options subject to operational constraints and economics at their IGCC EGU s. Given the inherently low HAP content of properly cleaned syngas, we be lieve the alternative options are equivalent.

Summary of Comments Received Following June 25, 2013, Reopening of Public Comment Period

Comment 15 2 : Commenter 20400 believes that the EPA ’ s proposed IGCC syngas requirements fall

outside of the source definition of an IGCC EGU. Commenter states that as it has defined an IGCC in the final MATS rule and in the response to comment documents, the EPA has excluded the gasification system from reg ulation under MATS. Commenter states that as a result the portion of the gasification system that flares the syngas is excluded from the definition of an affected IGCC EGU source. Flares can accept syngas from different parts of the gasification system. Co mmenter states that in the reconsideration rulemaking, the EPA did not propose any expansion of the definition for an IGCC EGU, nor has it proposed any in the current rule making. Commenter states that as a result the EPA has no legal basis in this rule ma king for imposing any requirements on the use of syngas.

Response to Comment 152 : See the preamble to the final rule and responses to other comments above for responses to these comments.

Comment 15 3 : Commenter 20400 states that any requirements for the treatment of IGCC syngas during startup and shutdown periods must include the ability to flare syngas. Commenter states that in the reconsideration proposal, the EPA stated that it understands that at an IGCC EGU, syngas is generated in the gasifier and c ombusted in the turbine. Commenter states that the EPA recognizes that during the startup and shutdown periods, some or all of the syngas produced by the gasifier may not be combusted

in the turbine. Commenter states that the EPA solicited comments on the need to flare the unfired syngas, if it is more appropriate to require routing of the unfired syngas back into the system for all IGCC EGUs, and on the costs of adding duct burners, should they be required. Commenter states that in this action, the EPA sta ted that that various commenter s support flaring as an option. Commenter is one of the few utilities that have actual operating experience with IGCC EGUs. Commenter states that it

constructed the IGCC EGU s at the Wabash River Repowering Project which began commercial157

operation in 1995, and the Edwardsport Station which began commercial operation in June 2013.

Commenter states that if the EPA does impose additional requirements for syngas during startup and shutdown periods, those requirements must allow sou rces to flare for a number of reasons with safety of equipment and personnel being the most important.

Commenter 20428 states that the definition must allow gasifiers to IGCC EGU s to have the option of flaring syngas or rerouting to duct burners.

Comment 1 54 : Commenter 20400 states that the EPA’s proposed requirements are unwarranted because flaring is already a required practice for safety reasons. As commenter ’s experience has shown, it is a frequent and foreseeable occurrence in an IGCC EGU, the CT wil l trip, halting the flow of air to the duct burners and all combustion of syngas in the turbine and the duct burners. Commenter states that the gasifier and other components can also cause an EGU shutdown. Commenter states that when this occurs, the syngas will become bottled up and accumulate in the system causing pressure to increase. Commenter states that to protect the equipment and prevent uncontrolled releases of syngas, pressure safety valves are installed in different parts of the system. Commenter states that the valves open to relieve pressure and the discharge is routed to the flare system. Commenter states that engineering codes require the use of pressure relief systems which is why the equipment vendors include these components in the facility design.

Commenter 20400 states that because syngas contains CO and hydrogen, a release of syngas that is not flared will create a fire and explosion hazard, as well as an inhalation hazard. Commenter states that flaring converts the CO and hydrogen to carbon dioxide (CO 2 ) and water vapor. Commenter states that the operation of these flares is permitted under the stations’ Title V operating permits. Commenter states that normally flaring is limited to purified syngas during startup or shutdown events. Co mmenter states that however during upset conditions small amounts of raw syngas could also be flared.

Commenter 20400 states that in the proposal, the EPA solicited comments on “the need to flare the unfired syngas, if it is more appropriate to require ro uting of the unfired syngas back into the system for all IGCC EGUs...” Commenter is concerned that the EPA could be operating under the belief that the syngas could also be routed back into the gasifier and combusted, which is not possible for two reasons.

C ommenter states that first, because the gasifier operates at high pressures, the O 2 , coal solution and startup natural gas must be pressurized before they can be injected into the gasifier. Commenter states that once the syngas leaves the gasifier and ente rs the cleanup system, it decreases in pressure and would

have to be re

- pressurized before it could be routed back into the gasifier. Commenter states that IGCC EGUs have no provision for doing this. Commenter states that second, a gasifier is designed as a “once through” system. Commenter states that gasifiers need to have a constant flow of material into and out of the system. Commenter states that routing all the syngas back into the gasifier would be analogous to taking the tail pipe of an automobile an d routing it back into the air intake. Commenter states that before long the CO 2 will accumulate to levels high enough so that the automobile’s engine would stall. Commenter states that in the case of an IGCC, the gasification process will be extinguished.

Response to Comments 153 and 154 : The EPA notes that it is providing both options, use of flaring or duct burners, for handling of syngas not combusted in the turbine during periods of startup and shutdown. The EPA believes that this will provide flexibility to owner/operators of IGCC EGUs to choose one or both of the options subject to operational constraints at their IGCC EGUs.158

Comment 15 5 : Commenter 20400 states that during a routine startup the flaring of treated IGCC syngas occurs for only a short period of time. Using commenter ’ s Edwardsport IGCC as a model, syngas is produced in the gasifier and then goes through a clean

- up system to remove pollutants including HAP prior to it being fired in the CT . Commenter states that during a startup, th e CT is fired first using natural gas to produce electricity and to generate steam that is used for startup of the gasification system.

Commenter states that later, the gasifier is fired with natural gas to warm the equipment and establish flow through the gas cleanup system. Commenter states that once the gasifier reaches the proper conditions, a coal slurry solution is introduced to begin the gasification process. Commenter states that the raw syngas then flows into the gas cleanup system before being fla red. Commenter states that the CT fuel cannot be converted from natural gas to syngas until the gasifier reaches stable operating conditions

which occur at about 50

- 60 percent of the gasifier capacity. Commenter states that once the gasifier

reaches thos e conditions, the clean syngas valve is phased into the turbine while the natural gas is phased out. Commenter states that this fuel transition phase normally takes less than a half hour.

Commenter states that once all syngas is channeled into the turbine, flaring of syngas ceases.

Commenter 20400 states that there are two important facts that show that gasifier emissions are minimized during startup flaring. Commenter states that the first is that the actual flaring step of a startup is relatively short a nd ordinarily last less than 2 hours. Commenter states that the second is that only clean syngas is flared during a routine startup. Commenter states that the gasification process converts much of the HAP into a solid material in the gasifier. Commenter st ates that the gas cleanup system, which at Edwardsport includes an activated carbon bed, then removes sulfur compounds, acid gases, Hg, other remaining HAP, and other materials. Commenter states that with the gas cleanup system in full operation, the HAP e missions from flaring syngas are essentially the same as using syngas

in the CT or duct burners. Commenter states that therefore the EPA need not be concerned about flaring syngas from an emissions perspective, even though the gasifier emissions are outside of the scope of the MATS regulation

.

Response to Comment 155 : Th is comment requires no response

.

4 .2 Option 2 Duct Burners

Summary of Comments Received Following November 30, 2012, Proposal

Comment 1 56 : Commenters 2 0281 and 2028 2 state that it is not always feasible to combust gas in duct burners, because if the turbine is not operational, air from the CT does not feed into the heat recovery steam generator ( HRSG ) and combustion in the HRSG of any fuel, including syngas, cannot occur.

Commenter s provide discussion about these points.

Commenter 2 024 5 states that the EPA has proposed two options for syngas not fired in the CT

. Commenter states that for process safety reasons, IGCC EGUs are designed to, and must be allowed to flare syngas during startup and shutdown periods. Commenter states that d uring startups and shutdo wns, the syngas produced by the gasifiers may not meet the specifications required for use in the CT and/or duct burners and its use could cause damage to the equipment and/or void the equipment manufacturers ’

warranties. Commenter notes that o f greater co ncern, is that during startups and shutdowns, the IGCC

EGU ’ s power block may not be in operation and, therefore, not capable of accepting syngas. Commenter159

states that o perating HRSG duct burners without the exhaust flow from an operating CT is a safety

ha zard. Based on the foregoing, Commenter requests that IGCC EGUs , including those equipped with duct burners in the HRSG, be allowed to flare syngas during startup and shutdown periods. According to

commenter , regulatory requirement to operate the EGUs in a manner which may compromise safety and vendor guarantees would act as barriers to the implementation of this technology.

Commenter 2 029 9 states that duct burners should neither be recommended nor required as an alternative

to flare stacks. Commenter provides discussion about how duct burners are not capable of handling upsets in the same manner or capacity as a flare. Commenter notes that the primary goal of design and proper operational procedures (work practices) is to minimize flaring which will co ntinue to reduce the benefit of using duct burners for other than normal operation. Commenter concluded that the potentially beneficial but infrequent utilization of unfired syngas is far outweighed by the additional cost, impracticality and operational co mplexity of employing duct burners for startup and shutdown transients or malfunctions and that they neither be required by rule nor offered as an alternative to flaring.

Response to Comment 1 56 : The EPA notes that it is providing both options, use of fla ring or duct burners, for handling of syngas not combusted in turbine during periods of startup and shutdown. The EPA believes that this will provide flexibility to owner/operators of IGCC EGUs to choose one or both of the options subject to operational co nstraints at their IGCC EGU s.

Summary of Comments Received Following June 25, 2013, Reopening of Public Comment Period

Comment 1 57 : Commenter 20400 states that it is technically unfeasible to require syngas not used in

the CT to be used only in duct burners. Commenter states that the EPA has proposed requiring sources to combust syngas in the HRSG duct burners when it is not used in the CT . Commenter states that this approach would only be feasible in some limited instances, b ut it cannot be mandated for all cases for

two reasons. Commenter states that the first is that O 2 will not always be available to the duct burners

for combustion. Commenter states that the first section of a CT operates as a large air compressor.

Commente r states that the motive force that drives the compressor is the combustion of either natural gas or syngas. Commenter states that the hot gases produced drive the turbine section of the CT which is directly coupled to the compressor. Commenter states that not all of the O 2 in the inlet air is utilized for

combustion in the CT. Commenter states that as the hot exhaust gas flows out of the CT, it enters the HRSG where the duct burners use a portion of the remaining O 2 to combust additional fuel supplied to

t he duct burners. Commenter states that the EPA ’ s basic premise is that when syngas is not combusted in the CT, the syngas can be combusted by the duct burners. Commenter states that the first flaw is that

there will be times when the CT shuts down and cann ot operate when there is syngas in the system.

Commenter states that when the CT shuts down, it stops providing the combustion air into the HRSG that is necessary for combustion. Commenter states that as a result combustion of any fuel, including syngas, is simply not possible.

Commenter 20400 states that the second reason that duct burners cannot be used to combust all syngas generated during a startup is because they are too small. Commenter st ates that duct burners are generally designed to have a heat input that is about 25

- 30 percent of the CT . Commenter states that thus, the amount of syngas generated during a startup will exceed the capacity of the duct burners.

Commenter states that also , duct burners are not always operating. Commenter states that if an IGCC

EGU trips suddenly, then there will not be enough time to start the duct burners before the syngas160

system pressure increases to the point that must be sent to a flare. Commenter stat es that, in summary, duct burners alone cannot be used as an alternative, so flaring must be allowed.

Response to Comment 157 : The EPA notes that it is providing both options, use of flaring or duct burners, for handling of syngas not combusted in turbine during periods of startup and shutdown. The EPA believes that this will provide flexibility to owner/operators of IGCC EGUs to choose one or both of the options subject to operational constraints at their IGCC EGUs.

5.0 OTHER

Summary of Comments Receive d Following November 30, 2012, Proposal

Comment 1 58 : Commenter 2 028 0 ask s the EPA to reinstate the use of the diluent cap and minimum electrical production rate specified in the proposed Rule at all times when the EGU is operating in low load conditions (including, but not limited to, startup and shutdown), and provide sources with the ability to comply with a unit

- specific startup definition. Commenter states that low load conditions that occur during the startup process and at other times during EGU operation can result in calculated emissions rates that are unrealistically hi gh. Commenter notes that equations for calculating compliance with input

- based limits, however, are not designed to be used in these situations because they assume complete combustion and normal operating conditions. Commenter states that as a result, thes e equations overestimate emission rates when CO 2 concentrations are very low or O 2 concentrations are very high, including during startup.

Commenters 2 0272 and 2028 1 state that some CEMS measurements are not accurate during startup, or are otherwise not appropriate for use in compliance calculations. Commenter expresses particular concern about: (1) the use of diluent (O 2 or CO 2 ) values from CEMS in the equations for c alculating compliance with input

- based limits (e.g., limits expressed in lb/MMBtu or pounds per trillion British thermal units ( lb/TBtu ) ); ( 2 ) the use of uncorrelated data from PM CEMS; and (3) the effect of low generation levels on output based emissions rates. Commenter s discuss each of these issues.

Commenter s state that an expanded startup period would solve each of these problems.

Commenter 2 030 6 recommends that work practice standards should identify periods when CEMS do not provide accurate indicati ons of emissions during startup or shutdown. Commenter discusse s when this occurs, and notes that these occurrences are marked in Commenter ’ s quarterly excess emission reports.

Commenter notes that the accuracy of CEMS is not verified during startup and shutdown conditions

because the EPA Reference Tests must be performed at steady state conditions that are not available during startup or shutdown.

Commenter 2 030 6 states that CEMS data collect ed and reported during startup and shutdown conditions should be clearly marked and not used as part of 30

- day or other rolling averages to determine compliance with the MATS rule. Commenter suggests that the management and reporting of CEMS data during st artup and shutdown periods should be defined in the SS Plan that is submitted for approval to the state or local permitting agency.

Commenter 2 027 2 states that equations for calculating compliance with input

- based limits, overestimate

emission rates when CO 2 concentrations are very low or O 2 concentrations are very high, including161

during startup. Commenter states that t o ensure that EGUs that opt to use CEMS are not penalized by this phenomenon , the EPA must either define startup and shutdown as ending (an d beginning) after (and at) the point when diluent concentrations reflect normal operation, or provide for a diluent “ cap ” similar to the one provided in final Appendix A for Hg. (40 CFR Part 63, subpart UUUUU, app endix A

, section 6.2.1.2, 77 FR 9606)

Co mmenter 2 027 2 states that PM CEMS ’ ability to monitor PM is dependent on correlation of the PM CEMS output to a reference method stack test. Commenter states that b ecause the EPA reference methods cannot reasonably be performed under startup and shutdown conditions, PM CEMS are not (and cannot reasonably be) correlated during these periods. Commenter states that t he uncorrelated data from PM CEMS may be inaccurate for many reasons , including differences in stack flow (which can result in temporary stratification of pollutant concentrations in the stack) and particle characteristics (e.g., from combustion of different fuels) during startup and shutdown. Commenter states that n either the February 16, 2012

, final rule nor the proposed reconsideration rule acc ount for these accuracy issues.

Commenter 2 028 2 states that the very stringent limits in the MATS rule impose near zero emissions requirements that do not provide a practical opportunity for over control to make up for the higher emissions that can occur when the control equipment is not fully functioning dur ing startup.

Commenter 2 032 1 discussed the controls, the controls ’ costs, and low emission rates for its EGUs.

Commenter states that even with its advanced control systems, it will be difficult to meet the emission requirements during periods of startup a nd shutdown.

Response to Comment 1 58 : In the February 2012 final MATS rule , the EPA established work practice standards rather than numeric emissions standards for periods of startup and shutdown. In the

reconsidered final rule , the EPA is finalizing definitions and work practice standards for startup and shutdown periods, which it believes are broadly applicable. Pollutant emission rates measured during startup and shutdown hours are not used to determine compliance with the emission st andards , but EPA wants the data to evaluate as part of the CAA section 112(d)(6) and (f) reviews

.

In response to comments regarding use of the diluent cap, the reconsidered final rule allows the appropriate diluent cap value to be used to calculate heat i nput

- based emission rates for all monitored pollutants (i.e., for Hg, SO 2 , HCl, PM, and/or hydrogen fluoride (HF)) during startup or shutdown periods, whenever the quality

- assured hourly average CO 2 concentration measured by the CEMS is below the cap value or when the quality

- assured hourly average O 2 concentration measured by the CEMS is above the cap value. This is consistent with section 3.3.4.1 of 40 CFR Part 75, Appendix F, which applies to the calculation of heat input

- based NO
x emission rates.

Comme nt 1 59 : Commenter 2 028 2 disagreed with the EPA ’ s statement in the preamble in the final

MATS rule that “ periods of startup, normal operations, and shutdown are all predictable and routine aspects of a source ’ s operations, ” 77 FR 9382. Commenter suggests that if the natural gas market share increases and wind generation increases, it is possible that coal EGUs in deregulated states will have more frequent shutdowns and startups that are the result of state grid operator demands and not within

the control of an individual utility.162

Response to Comment 1 59 : The EPA disagree s with the commenter ’ s assertion. Operation within a deregulated state includes a calculus of items to be considered; among them are the possibility of more frequent startups and shutdowns as a routine matter. In any case, we believe compliance with the work practice standards during startup and shutdown periods will lead to HAP emissions that are on average at or below the numerical standards because of the requirement to combust only clean fuels for the beginning periods and to maximize the use of clean fuels throughout the 4

- hour period after electricity production begins and coal , residual oil, or solid oil

- derived fuel is added to the EGU and the PM controls are brought on line.

Co mment 16 0 : Commenter 2 030 8 recommends that a n EGU should not have to sample for Hg with sorbent traps until startup has ended. Commenter states that if a site is using continuous monitoring, startup and shutdown data may be available. Commenter notes that because data from sorbent traps and

other test results will be submitted to the EPA via the Emissions Reporting Tool ( ERT ) , and continuous data will be submitted using the Emissions Collection and Monitoring Plan System ( ECMPS ) , this appears to be a clear and easily discernible breakpoint.

Commenter 2 030 8 notes that for shutdown periods, when monitoring for Hg with sorbent traps, the shutdown periods should be very short and measurements will not be able to be separated out but will

use data from the last traps analyzed; and, have the potential of skewing any presented data.

Response t o Comment 16 0 : 40 CFR 63.10020 requires all monitoring systems to operate and collect data at all times, except for monitoring system malfunctions, out

- of

- control periods, or when certain quality assurance (QA) activities are performed. Therefore, all monitoring systems (including sorbent trap systems) must record and report data during startup and shutdown periods, provided that the

systems are not out

- of

- control or undergoing required QA testing.

The reconsidered rule allows EGU owners or operators who choose to use H g sorbent traps for compliance purposes either to include Hg emissions during startup or shutdown periods with those from periods other than startup or shutdown or to use one Hg sorbent trap monitoring system for startup or shutdown periods and another Hg sorbent trap monitoring system for other periods. A separate Hg sorbent trap monitoring system used only for periods of startup or shutdown would keep the startup and shutdown emissions separated from emissions during normal operation, so as not to include the startup

and shutdown emissions in the 30

- (or 90

- ) boiler operating day rolling average emission calculations. As mentioned earlier, Hg emissions during startup or shutdown periods are not expected to be problematic, given that the duration of those p eriods is supposed to be minimized, that clean fuels are to be burned during those periods, that control devices are to be operated as long as possible, and that the averaging period associated with the emissions limit is long (30

- or 90

- boiler operating days). This expectation is consistent with that of commenter 20428, who identifies “...the short duration of startup relative to the normal operating period for a sorbent trap, and the use of clean startup fuels...” as providing such low emissions data as to b e below detection levels.

Although the EPA disagrees with not collecting emissions data during periods of startup or shutdown, the EPA agrees with commenters that emissions should be low. This expected emissions behavior is shown in a figure submitted by one commenter ; 23 assuming that the EGU operated at the hourly values

23 See F igure 9 from Attachment I from C ommenter 20428163

shown for startup or shutdown periods, that the EGU operated at normal load for all other periods, and that the EGU owner or operator chose to meet the 30

- boiler operating day Hg emission s limit, then by having average hourly Hg emissions during periods other than startup or shutdown no larger than 1.14 pounds Hg per TBtu (about 95 percent of the emissions limit), the EGU would demonstrate compliance. In another example, Hg emissions from a common stack are shown in a figure submitted by one

commenter. 24 Given the same assumptions as for the previous example, then by having average hourly Hg emissions during periods other than startup or shutdown no larger than 1.18 pounds Hg per TBtu (about 99 percent of the emissions limit), the EGU would demonstrate compliance. We note that these data were collected prior to application of the work practice to these units and the commenters do not assert that they were complying with the work practice at t he time the testing was conducted or indicate

that the EGU s at issue are among the best performers under any metric used in this final rule to determine the work practice requirements

. For th ese reason s , we believe the HAP emissions will likely

decrease si gnificantly more when sources are complying with the final rule.

The EPA notes that Commenter 20308 is incorrect in stating that Hg sorbent trap data will be submitted through the ERT. While sorbent trap data are to be collected via the ERT when the modul e is ready, sorbent trap data are to be submitted using ECMPS.

Comment 16 1 : Commenter 2 030 5 states that the EPA did not provide a rationale for re

- opening the startup and shutdown work practice standards.

Response to Comment 16 1 : The EPA provided its rationale for granting reconsideration of the SS provisions of MATS in the reconsideration proposal notice (77 FR 71330).

Comment 16 2 : Commenter 2 029 7 states that its EGUs cannot initially startup while routing emissions through the FGD to the main stack where the primary CEMS are located. Commenter cites Section 3,

Table 3: “ You must operate all CMS during startup. ” Commenter states that it operate s CEMS for Opacity a nd SO 2 on emissions routed to the bypass stack for startup purposes, but does not believe it should be necessary to operate redundant Hg monitors in this location as well. Commenter states that the Hg emissions standard is a 30

- day average and alternative data collection methods such as fuel sampling

can be utilized to determine worst case Hg emissions during the times when startup occurs.

Response to Comment 162 : First, the EPA notes that continuous opacity monitoring systems are COMS, not CEMS. Although the EPA agrees with the commenter that Hg emissions during periods of startup or shutdown are expected not to have much impact on the 30

- boiler operating day rolling average, the commenter will need to monitor its EGUs’ Hg emissions during those periods, c onsistent

with the final rule . The Hg monitors for the bypass stacks need not be redundant Hg CEMS (as the commenter appears to suggest); sorbent trap monitoring systems could be used.

Comment 16 3 : Commenter 2 028 2 states that comments that were in commenter ’ s MATS Reconsideration Petition that were not addressed in the proposed rule are: emission monitoring, compliance calculation, and reporting during startup and shutdown; how startup and shutdown definitions and work practice provisions apply to E GUs that share a common stack; and that the EPA ’ s definitions of startup and shutdown are insufficient to exempt all periods of non

- normal operation,

24 See Figure from Attachment V from C ommenter 20428.164

which would penalize EGUs during periods of abnormally low CO 2 values and abnormally high O 2 values.

Com menter 2 028 2 discussed the difficulty of obtaining accurate measurements and under low load conditions, the difficulty of calculating output based emission values when there is low or no output, and how compliance calculations assume complete combustion a n d normal operating conditions.

Commenter 2 028 1 states the proposed reconsideration rule also does not resolve how the startup and shutdown definitions and work practice provisions apply to EGUs that share a common stack.

Response to Comment 16 3 : In the February 2012 final MATS rule the EPA established work place standards rather than numeric emissions standards for periods of startup and shutdown. In the

reconsidered final rule , the EPA is finalizing definitions and work practice standards for startup an d shutdown periods, which it believes are broadly applicable. The work practice is not an exemption.

As mentioned elsewhere, regarding use of the diluent cap, the reconsidered final rule allows the appropriate diluent cap value to be used to calculate hea t input

- based emission rates for all monitored pollutants during periods of startup or shutdown (i.e., for Hg, SO 2 , HCl, PM, and/or HF), whenever the quality

- assured hourly average CO 2 concentration measured by the CEMS is below the cap or when the quality

- assured hourly average O 2 concentration measured by the CEMS is above the cap for EGUs in startup and shutdown mode , whether for EGUs with single stacks or for EGUs that share a common

stack . This is consistent with section 3.3.4.1 of 40 CFR Part 75, Appe ndix F, which applies to the calculation of heat input

- based NO
x emission rates. Moreover, the reconsidered final rule allows the use of a default electrical load of 5 percent when no electricity is being generated during periods of startup

or shutdown (on ce electricity is generated during startup, sources are required to use actual electrical output instead of the 5 percent default value, even if the electricity level is below 5 percent) . Application of a diluent cap and a default electrical load should al leviate commenters’ concerns over emissions calculations for compliance during periods of startup or shutdown when units share a common stack

.

As mentioned earlier and in the reconsidered final rule preamble , EGUs with common stacks may either monitor each EGU venting to the stack separately, or monitor at the common stack (provided that the EGUs are subject to the same emission limits). If monitoring is done at the common stack, then the startup or shutdown provisions are applied whenever any EGU served by the stack is in the startup or shutdown mode, as defined in the final rule. All monitoring systems are required to operate during the startup and shutdown periods. Except when EGU owners or operators choose to include Hg emissions measured with sorbent trap monitoring systems during periods of startup or shutdown, data recorded during startup and shutdown are excluded from the compliance calculations.

Summary of Comments Received Following June 25, 2013, Re opening of Public Comment Period

5.1 U se of d iluent c ap

Comment 16 4 : Commenters 20388 and 20405 suggest that the EPA adopt measures recommended by the utility industry on the issues discussed in the June 25, 2013

, notice, and indicate industry ’ s recommendations are reasonable and follow good engineering practice.165

Commenters 20384, 20387, 20389, 20390, 20397, 20401, 20410, and 20428 support reinstatement of

diluent caps for non

- mercury HAP during periods of startup and shutdown . Commenter 20422 indicates

that use of the diluent caps should be caveated.

Commenter s 20401 and 20411 support the use of diluent cap values during periods of startup in order to prevent emission reported during startup from being grossly overstated when complying with h eat input

based emission standards. Commenter 20411 believes that allowing the use of the 40 CFR Part 75 diluent cap procedures for non

- mercury pollutants, as is allowed for Hg in 40 CFR Part 63

, subpart

UUUUU

, Appendix A, would allow utilities to report m ore representative emissions that occur during startup. Commenter 20411 would also like to state its support for allowing use of a diluent cap for calculating emissions for EGU s subject to 40 CFR Part 60, subpart D standards.

Commenters 5834, 5840, 20417

, 20418, and 20419 support the proposal to reinstate the use of the diluent cap, and/or provide for the use of diluent caps for non

- mercury pollutants, as is allowed for Hg in Appendix A of subpart UUUUU. Commenters support the approach of allowing for the use of a diluent cap at a minimum of 5 percent CO 2 and a maximum of 14 percent O 2 when calculating emission rates for all pollutants, for any operating hour. Further, commenter s support the use of default diluent gas cap values during periods of startup an d shutdown. Commenters state without the use of diluent caps, non

representative emission rates will be reported. Commenter 5840 suggests that the EPA allow use of a diluent cap regardless of how startup and shutdown are defined, to avoid reporting of mean ingless data.

Commenter 20421 supports the use of diluent caps which are appropriate and would be used in only limited situations such as startups, shutdowns, EGU trips or upsets and allow for a truer measure of the calculated emission rate during period s when CO 2 and O 2 are close to ambient conditions

.

Commenter 20425 supports Commenter 20428 ’ s recommendation to utilize the Part 75 diluent cap for

non

- normal operating periods. Commenter 20418 recommends that the EPA provide for use of the diluent cap du ring periods of startup and shutdown under the MATS Rule and encourages the EPA to adopt provisions consistent with 40 CFR Part 75 and allow use of the diluent cap during “any operating hour” when measured diluent gas values meet Part 75 criteria.

Commenter 20429 states that the fuel factors used to calculate emissions assume good combustion and normal operating conditions that are not applicable to SS conditions. Commenter believes that a diluent cap should be allowed for all pollutants reported on a heat input basis to ensure significant over

reporting of emissions during SS does not occur.

Commenter s 20408 and 20428 state that at low load, EGUs do not achieve complete combustion and

actual measured CO 2 concentrations are lower and O 2 concentrations are higher than normal operating conditions, resulting in significant overstatement of emissions during startup, shutdown, and other low

load conditions. Commenter 20428 notes that diluent gas analyzer sensitivity and stack gas stratificati on make it difficult to obtain accurate diluent measurements under low load conditions and, even more important, the equations used to calculate lb/MMBtu or lb/TBtu values rely on fuel factors that assume complete combustion and normal operating conditions

. Commenter 20428 states that when an EGU is operating at low load, it does not achieve complete combustion and actual measured CO 2 concentrations

are lower and O 2 concentrations are higher than during normal operation; these differences between assumed op erating conditions and actual operating conditions result in significant overstatement of166

emissions during startup and shutdown and other low load conditions. Commenter indicates that, in short, the equations needed to calculate emission values for input

- b ased standards simply were not designed for use under such conditions.

Commenters 20428 and 20404 state that the EPA should adopt a diluent cap for SO 2 , PM, HCl, and HF. Commenter 20428 states the EPA should extend use of diluent cap to all pollutants whe re emissions are calculated on an input basis to ensure applicable standards are achievable and to prevent significant

over

- reporting of emission rates during exempt periods. Commenter 20404 states that, alternatively, the EPA could exempt reporting of all pollutants during SSM periods; if reporting during SSM periods is required, commenter proposes a lower limit of 5 percent CO 2 diluent cap in F Factor calculations used to generate lb/MMBtu emissions rates.

Commenter s 20428 and 20387 state that the EPA re cognized these issues under the Acid Rain Program

in P art 75 and included conservative diluent caps ( i.e., are designed to result in calculation of emission rates that are higher than what would be calculated under normal operating conditions) of 5 percent for

CO 2 and 14 percent for O 2 , and has since extended the diluent cap concept to other programs that rely on

P art 75 data (e.g., CAIR) and NSPS (subparts GG, KKKK, and Eb). Commenter 20390 note s tha t the NOx Budget and Acid Rain P rograms allo w diluent cap s of 15 percent for O 2 and 5 percent for CO 2 , with no restriction on duration and that some states allow the use of the same diluent cap in reporting NOx and CO for compliance with NSPS and permit limits . Commenter 20428 states that the EPA

in itially proposed to include diluent caps under this rule and finalized P art 75 diluent cap use for Hg only; the EPA failed to finalize diluent caps for other pollutants (SO 2 , PM, HCl, and HF) where they are

needed. Commenter 20408 states that the EPA needs to specify that the procedures outlined in 40 CFR, Part 75, Appendix F, section 3.3.4.1, are appropriate and should be used for emissions monitoring required by MATS. Commenter 20428 states that the current proposed 3/6 definition may not provide

sufficie nt time for diluent values to stabilize, and without diluent caps, EGUS will be forced to calculate, record, and report hourly values that are vastly overstated.

Commenter 20428 states that the EPA recognized the issue in 2011 when it initially proposed to include a diluent cap in the compliance calculations for periods of startup and shutdown under 40 CFR Part 63, subpart UUUUU. Commenter indicates that, perhaps in recognition of the different nature of the program, the EPA proposed a lower cap

– 10.0 pe rcent O 2 or the corresponding fuel

- specific CO 2 concentration

– than that used under Part 75. However, commenter notes that when the EPA in the final rule exempted periods of startup and shutdown from compliance calculations, the EPA failed to finalize

the proposed diluent cap provision and instead allowed use of the Part 75 diluent cap, but only for Hg. Commenter alleges that in limiting the cap to Hg, the EPA apparently failed to consider the fact that recording and reporting of lb/MMBtu and lb/TBu values also is required for other pollutants (e.g., SO 2 , PM, HCl, and HF) and to analyze whether the promulgated definition of startup was sufficient to cover all abnormal diluent values for those other pollutants.

Commenter 20428 states that under the current rule, startup is defined as ending at the point of generation of electricity, and only the period up to that point is exempted from emission standards; However, it may take hours after the first generation of electricity for diluent gas values to arrive at normal operating levels. Commenter alleges that because the EPA ’ s definitions of startup and shutdown as currently proposed are insufficient to exempt all periods with non

- normal operation and corresponding non

- normal diluent gas values, EGUs will be pena lized in their compliance calculation of167

non

- mercury input

- based emission values by having to incorporate abnormally low CO 2 values and abnormally high O 2 . Commenter maintains that, at a minimum, the EPA should correct this apparent oversight and adopt a d iluent cap for SO 2 , PM, HCl, and HF reported in lb/MMBtu or lb/TBtu as well.

Commenter 20428 states that, even if the EPA adopts a definition of startup that is sufficient to exempt

the non

- normal diluent values from the compliance calculation, EGUs still would be forced to calculate, record, and for SO 2 , HCl, and HF report to the EPA, hourly values during the startup and shutdown period that are vastly overstated. Commenter s 20428 and 20404 maintain that reporting values to the EPA that are obviously over stated can have many negative impacts for other CAA programs even if the values are not used in 40 CFR Part 63, subpart UUUUU, compliance calculations. Commenter 20428 alleges that the data could skew the results of emissions modeling if those values are u sed as inputs, and otherwise overstate emissions for standard setting or other compliance calculations. Commenter 20428 notes that although EGUs will record and, where required, report actual monitored diluent values, their responsible officials should not be required to certify as accurate resulting lb/MMBtu or lb/TBtu values they believe to be significantly overstated. Commenter 20428 maintains that allowing use of a diluent cap for all pollutants at least would minimize the overstatement and allow respon sible officials to certify that they are reporting values that are calculated based on a diluent cap that provides a reasonable, if conservative, estimation of actual emissions, rather than forcing officials to certify the accuracy of vastly

overstated val ues; alternatively, the EPA could exempt those startup periods from reporting.

Commenter 20428 states that as long as the EPA adopts a reasonable startup definition, it would not object to u se of the conservative P art 75 diluent cap to calculate and report data during non

- normal operating periods. Commenter states that although it believes that the cap the EPA proposed in 2011 would more accurately represent actual startup emissions by allowing use of CO 2 caps that are based on actual startup fuel (e.g., oil or gas rather than coal), commenter also understands that using different diluent caps for Hg and the other pollutants for which data are reported under Part 75 could make data

calculations inconsistent and more complicated.

Commenter 20390 notes that the proposed MATS startup and shutdown exemption language only

allows the use of a diluent cap during the startup and shutdown period, which is a very limited time while the boiler is starting up on auxiliary fuel(s ) and that the proposal would in essence allow for two

different diluent caps, one for NOx rate Acid Rain reporting and another for MATS reporting of SO 2 , HCl, Hg, and HF. Commenter also notes that PM is not addressed in the MATS reporting instructions,

an d question s whether the diluent cap and electrical production rate cap would also apply to PM.

Referring to proposed April 2013 Draft Monitoring Plant Reporting Instructions for MATS, Commenter

20390 note s the proposed diluent cap of 14 percent O 2 (19 per cent for IGCC) applies only for Equations

19

- 5 and 19

- 2, and question s whether the diluent cap method would apply to all formulas, and whether the reporting instructions would be changed to reflect 10 percent O 2 or equivalent CO 2 percent (based on equation, CO 2 percent = 20.9

– O 2 percent)/FO, where FO = 0.209 * (Fd/Fc)).

Commenters 20384 and 20428 state that diluent gas cap values will prevent reporting of meaningless emission values caused by diluent values approaching ambient levels. Commenter s 20408 and 20428 state that responsible officials should not be required to certify as accurate the resulting values they believe are significantly overstated. Commenter 20428 indicates that use of diluent caps would at le ast
minimize the overstatement.168

Commenter 20390 states that there are several components that make up the calculation for determining EGU emissions on an emission rate basis including a measurement of the flue gas volume, the pollutant emission, and a diluent correction factor; each of these components has inaccuracies or bias in their individual measurements and they are compounded when multiplied together. Commenter notes that the EPA, in establishment of emission limits, normally only tests at a full load steady state condition.

Commenter states that during startup, flue gas volume will go from 0 to 100 percent of the CEMS flow

measurement and O 2 will go from 20.9 to 3 percent. Commenter states one concern is the ability of CEMS to accurately measure flow and emissions during startup; there are no data comparing measured

values to CEMS at low flow and or to assess to what degree does the error at low flow conditions impact

a 30

- day average . Commenter states that RATA testing on CEMS in 40 CFR P art 75 includes 3

concentra tions of gaseous pollutants at low, medium, and high to give a range of precision, however for flue gas volume, RATA is only certified at full load, there are no data on the accuracy over the full range of gas flow from initial startup to full load. Commen ter states existing CEMS will not be capable of measuring values if monitoring is required during startup and shutdown. Commenter indicates that changes would need to be implemented to provide dual range analyzer systems that would include new analyzers, a dditional calibration gas and supply systems, and doubling the time/cost for quarterly and

year

- end test audits, and doubl ing the operating cost.

Commenter 20390 states that not correcting to a diluent of 10 percent O 2 during startup and shutdown

can caus e orders of magnitude of bias and error to emission rate calculations. Commenter supports a default diluent of 10 percent for O 2 or the fuel

- specific CO 2 concentration.

Commenter 20387 supports use of a diluent cap for heat input

- based standards. Commenter 20389

supports diluent gas cap values where CEMS are required to show compliance with heat input

- based standards during startup.

Commenter 20422 states industry raises legitimate concerns over the accuracy of calculating emission values during periods of startup and shutdown and present theoretically legitimate concerns regarding artificially high emissions that might result from measuring startup emissions using CEMS, and the use of diluent values to report emissions makes sense so long as the EPA predicates emission reported using these default values on the understanding these emission values are only intended to provide an estimate of startup emissions and a re lative sense of startup emissions between EGU s, and may not be used to

draw co nclusion about these emissions.

Commenter 20420 states that the default diluent caps in 40 CFR Part 75 should be incorporated into MATS for the calculation of heat input based e mission rates for all pollutants. C ommenter suggests that default diluent caps should apply whenever the measured diluent is below the CO 2 cap or above the O 2

cap. C ommenter states that if diluent caps are not incorporated into MATS, because of the format of the emission rate calculation formula, lb/MMBtu (or lb/TBtu) emission rates that are calculated during periods of low CO 2 or high O 2 will be extremely high, approaching infinity.

Commenter 20420 states that because MATS requires data to be recorded dur ing all periods of source operation, the lack of default diluent caps may lead to measurement mistakes for actual emission rates during these time periods. C ommenter states that without diluent cap values at low CO 2 or high O 2 concentrations, EGU s will significantly over

- report or under

- report emissions depending on the169

direction of the daily calibration error of the diluent gas monitor. Commenter states that the diluent cap represents a practical and accepted solution to the limitations of the F

- factor based emission rate equation, and should be incorporated in the MATS rule to remedy these issues.

Commenter 20391 states that the EPA should provide for the use of a diluent O 2 or CO 2 cap for calculating compliance with input

- based limits. Commente r states that during startup, or other periods when an EGU is at low load and does not achieve complete combustion, CO 2 concentrations are lower than during normal operation and O 2 concentrations are higher than during normal operation.

Commenter states th at equations for calculating emission values for input

- based standards, however, are not designed to be used in these situations because they assume complete combustion and normal operating conditions. Commenter states that as a result, these equations ove restimate emission rates

when CO 2 concentrations are very low or O 2 concentrations are very high, including during startup.

Commenter states that to ensure that EGU s that opt to use CEMS are not penalized by this phenomenon, the EPA must either define sta rtup and shutdown as ending (and beginning) after (and at) the point when diluent concentrations reflect normal operation, or provide for a diluent “ cap ” for calculating, reporting and recording of all pollutants (SO 2 , HCl, PM

, and HF) similar to the one p rovided in 40 CFR Part 63 subpart UUUUU, Appendix A for Hg. Commenter states that current EPA regulations in 40 CFR Part 75, Appendix A.3.3.4.1

, allow diluent caps 5 percent CO 2 and 14 percent O 2 ) for NOx.

Commenter states that such an approach would be co nsistent for the MATS rule.

Commenter 20399 states that the EPA should follow 40 CFR Part 75 guidance on use of diluent caps.

Commenter states that the EPA ’ s adoption of the proposed startup definition will likely address most of the operating conditions where diluent caps would be utilized, but in cases where EGU s opt to not exclude startup and shutdown data, low load operation or load swings, and depending how the EPA elects to handle startups for EGU s sharing a common stack, CO 2 or O 2 concentrations could impact input

- based emission rates. Commenter states that it is counterproductive to require EGU s using continuous emission monitors to include overestimations in their emissions averaging periods.

Commenter states that MATS

- affected E GU s currently operate CEMS according to 40 CFR Part 75.

Commenter 20399 states that by adopting diluent caps defined under Part 75 for MATS the EPA would allow for consistency between monitoring programs and prevent over reporting in instances where

dilue nt values bias MATS emission rates. Commenter states that EGU s running at decreased load or firing clean fuels are emitting at a decreased rates and the MATS rule should enable EGU s to accurately represent that in their emissions averaging and reporting.

Commenter 20400 states that the current definition of startup causes emissions monitoring issues and

, thus

, commenter supports the use of diluent capping. Commenter 20413 agrees with Commenter 20400 comments concerning CEMS and the use of a diluent cap def ault value during startup. Commenter

20400 states that f

or each EGU MACT limit, the EPA has provided an option for use of CEMS.

Commenter 20400 states that some CEMS measurements are not accurate during startup, or are otherwise not appropriate for use in compliance calculations. Commenter 20400 strongly supports the use of diluent capping for Hg, HCl, and PM CEMS. Commenter 20400 is particularly concerned with: (1) the use of diluent (O 2 or CO 2 ) from CEMS in the equations for calculating compliance with in put

based limits (e.g., limits expressed in lb/MMBtu or lb/TBtu); (2) the use of uncorrelated data from PM CEMS; and (3) the effect of low generation levels on output based emissions rates.170

Commenter 20400 states that during startup, or other periods when an EGU is at low load, CO 2 concentrations are significantly lower and O 2 concentrations are higher than during normal operation.

Commenter states that boiler manufacturers direct operators to use large amounts of extra combustion air for safety reasons un til the EGU achieves normal operating conditions at higher loads. Commenter

states that equations for calculating compliance with input

- based limits, such as the “ F factor ” equation however, are not designed to be used in these situations because they assume complete combustion and normal operating conditions. Commenter states that as a result, these equations overstate emission rates

when CO 2 concentrations are very low or O 2 concentrations are very high, including during startup periods. Commenter notes that b y comparison

, measurement of mass emissions such as tons of SO 2 or NOx use pollutant concentration and volumetric stack flow

. ) Commenters state to ensure that EGUs tha t utilize CEMS for compliance are not penalized by this phenomenon, the EPA must either define startup (and shutdown) as ending (beginning) when diluent concentrations reflect normal operation, or provide

for a diluent “ cap ” similar to the one provided in final Appendix A for Hg. ( 77 FR 9606

, Appendix A

, section 6.2.1.2 .) Commenter states that the expanded startup period proposed by Commenter 20400 resolves this issue because a startup would conclude when CO 2 concentrations are high enough, or O 2

concentrat ions are low enough to accurately measure emissions.

Commenter 20400 states that the EPA could still elect to define startup in such a way that some EGU s continue to have CO 2 concentrations that are significantly lower and O 2 concentrations that are higher than during normal operation. Commenter states that in addition the EPA will likely still require the reporting of all CEMS data including startup and shutdown periods. Therefore

, commenter recommends that the diluent cap de finition be defined independently from the startup exclusion. Commenter states that diluent capping is well understood under the Part 75 rules, and applies to the CO 2 (or O 2 ) data in the

calculation of NO X lb/MMBtu already. Commenter suggests that using th e same definition would simplify application of this rule to a common dataset being used for both programs, and decouple the use of diluent capping from the definition of startup exclusion under MATS.

Commenter s 20400 and 20413 state that data from PM CEM S also may be inaccurate during startup and

shutdown. Commenter s state that for example, PM CEMS ’ ability to monitor PM is dependent on correlation of the PM CEMS output to a reference method stack test (e.g., Method 5). Commenter s state
that because the E PA reference methods cannot reasonably be performed under startup and shutdown conditions, PM CEMS are not and cannot reasonably be correlated during these periods. Commenter s

state that the uncorrelated data from PM CEMS may be inaccurate for many reasons , including differences in stack flow (which can cause temporary stratification in the stack) and particle characteristics (e.g., from combustion of different fuels during startup). Commenter 20400 state s that neither the February 16, 2012

, final MATS rule nor the proposed reconsideration rule account for these accuracy issues. Commenter s note

, however

, their proposed definition for a longer period startup would solve this problem because startup would end at a point when startup fuels such as natural gas o r oil are either not used or constitute a low fraction of the total heat input.

Commenter 20400 states that in accordance with the final MATS rule, once a startup ends, an affected

EGU using CEMS to demonstrate compliance must begin calculating hourly emi ssions rates based on heat input (lb/TBtu) or electrical output (lb/GWh). Commenter states that these hourly values are then used to generate 30

- day rolling averages. Commenter states that when a n EGU begins generating electricity during a startup, it does so at a very low percent of its total capacity. Commenter states that however at this time the amount of heat energy required to generate each EGU of electricity is much171

higher than during normal ope ration. Commenter states that this is occurring at the same time that certain emissions control equipment is not operating at it full effectiveness. Commenter states that the combination of a higher numerator value (emissions) divided by a lower denominato r value (generation) means that on an output basis, emissions rates during a startup are even higher than a heat input basis as compared to normal operation. Commenter states that

, for example, during the first hour after the generator begins to produce el ectricity the reported electrical output may be 1 to 2 percent of the maximum electrical output yet the fuel firing rate may be greater than 10 percent of the maximum rated heat input. Commenter states that with output based values even higher during start up due to lower efficiency than heat input based values, the startup emissions are even more difficult for operators to average down in a 30

- day rolling average. Commenter notes that e xtending the averaging period does not solve the problem because it incr eases the possibility of multiple startups in an averaging period

. Commenter states that an expanded startup period would solve this problem because a startup would typically end only when a n EGU has begun to generate a significant amount of electricity an d has reached its normal, more energy efficient operating condition.

Commenter 20407 states that a minimum diluent cap should be included in the standard. Commenter

states that in establishing the EGU limits the EPA has provided an option for the use of C EMS to monitor and report emissions values. Commenter states that for EGU s with CEMS, monitoring and calculation of emission values during periods of startup and shutdown, and other low

- load conditions, present special issues. Commenter states that with re spect to diluent gas measurements, when an EGU is at low load, CO 2 concentrations are lower and O 2 concentrations are higher than during normal operation. Commenter states that equations for calculating continuous compliance with input

- based

standards were not designed to be used in these situations because they assume complete combustion and normal operating conditions. Commenter states that the EPA recognized these issues when establishing monitoring requirements for the Acid Rain Program and promulgated provisions allowing reporting of a diluent “ cap ” in place of measured O 2 or CO 2 values. Commenter states that although the use of the cap was initially limited to periods defined as startup and shutdown, the EPA later expanded the concept to include any period during which measured O 2 or CO 2 fell below the specified cap.

Commenter states that the use of the diluent cap is also allowed for Hg in 40 CFR Part 63, subpart UUUUU, Appendix A. Commenter believes that the diluent cap should also be allowed for SO 2 , HCl

, and HF . Commenter states that the Part 75 diluent cap should be allowed during periods of startup,

shutdown and other low

- load conditions where the O 2 or CO 2 concentrations fall below the specified

cap.

Commenter 20403 supports the use of diluent caps which are appropriate and would be used in limited

situations such as EGU trips or upsets. C ommenter states that diluent caps allow for a truer measure of the calculated emissions during periods when CO 2 and O 2 are close to ambient conditions. C ommenter

states that formulas that utilize CO 2 and/or O 2 significantly overestimate emission when CO 2 and O 2 approach ambient conditions. Commenter states that the use of diluent caps would mostly be applied

when the EGU s are already in startup and shutdowns but there are limited situations where a diluent cap would need to be applied and are appropriate such as a n EGU trip or upset.

Response to Comment 164 : Apart from allowing use of a diluent cap when calculating Hg emissions during periods of startup or shutdown, the final rule contained no diluent cap allowances

.

The EPA considered each comment, agreed with the commenters who suggested a need for diluent caps172

for EGUs using a common stack , and decided to allow use of default CO 2 or O 2 values as identified in Section 3.3.4.1 of Appendix F of 40 CFR Part 75 only for periods of startup or shutdown when CO 2 values are below or O 2 values are above default values. For non IGCC EGUs, the default CO 2 value is 5 percent and the default O 2 value is 14 percent. This means that when CEMS CO 2 measurements are below 5 percent, EGU owners or operators are allowed to us e 5 percent CO 2 in their calculations. When

CEMS CO 2 measurements become 5 percent or larger, EGU owners or operators will be required to use

the CEMS CO 2 measurements in their calculations. Since the startup analysis showed that CEMS CO 2

measurements exce eded default values within 2 hours of generation, the EPA does not expect to find default values being used when startup periods end. Likewise, when CEMS O 2 measurements are larger than 14 percent, EGU owners or operators will be able to use 14 percent O 2 in their calculations. When

CEMS O 2 measurements become 14 percent or smaller, EGU owners or operators will be required to

use the CEMS O 2 measurements in their calculations. Note that IGCC EGUs will be allowed to use 1 percent as a default CO 2 value of 1 percent or 19 percent as a default O 2 value. As mentioned earlier, default diluent gas values will be allowed for use in calculations only for periods of startup or shutdown

when CO 2 CEMS values are below or O 2 CEMS values are above default values. The rul e requires EGU owners or operators to use CO 2 or O 2 CEMS values for all other operating periods. While the EPA has no specific data or information concerning emissions during transient events outside startup or shutdown periods , the EPA expects the short d uration of these transient events that could cause CO 2 or O 2 CEMS to be below (or above) default values to have little, if any, impact on the 30 boiler operating day rolling

averages.

The rule retains the requirement for EGU owners or operators to report instrumental CEMS, PM CPMS, or sorbent trap information, as well as flow rate information during periods of startup or shutdown. Such information may prove useful in assessing potential emissions or operational limits in future rulemaking

activities.

As shown in figures submitted by commenter 20428, emissions as measured by CEMS during startup or shutdown periods do not appear to be “...grossly...,” “...vastly...,” or “...significantly...” overstated

. The largest hourly values are no more than 7 times the emissions limit value

– nowhere near the “...exceedingly high, approaching infinity...” values that one commenter suggested

- and the majority of hourly values (704/829) are near the emissions limit value. 25 The values depicted in the figures do not contain diluent caps, which, if used, would further reduce the values. There is also no information that the units were complying with the work practice standard when these data were collected.

Even though the values recorded without using diluent caps do not appear overstate d or problematic, the rule allows use of diluent caps during periods of startup or shutdown. The EPA agrees with commenter 20428 who states that calculations based on use of a diluent cap provide reasonable estimated values of

actual emissions for EGUs on a common stack

.

One commenter (20428) states that PM emissions recorded during those periods for both EGUs with common and individual stacks are about 2 to 3 times normal emissions and provides PM emissions

25 See Figures 1, 2, 3, 6, 8, and 9 from Attachment I, as well as the Figure in Attachment V, submitted by C ommenter 20428. Figure 8 is assumed to contain values measured in dry standard cubic meters and

tho se values are converted to lb/MMBtu values. Note that figures which applied a diluent cap are not used, as it is unclear when diluent cap values were used.173

values in Figures 2 and 3 of Attachment I. It i s important to remember that these data were collected from periods other than when the MATS rule was applicable, so we do not know whether emissions control devices and operational techniques required by the rule were in place during the data collection periods. Furthermore, the values shown are denominated in terms other than what the rule requires (i.e., hourly averages are shown but compl iance with the rule is based on 30

- boiler operating day rolling averages). Isokinetic conditions were maintained during that testing, and average mass acid gas emission rates obtained from CEMS without diluent gas correction during periods of startup and s hutdown were found to be no more than 3 times baseline mass acid gas emission rates. In any case, we continue to question the accuracy of HAP emissions measurements obtained during the defined startup and shutdown periods.

Finally, the rule requires EGU owners or operators to identify each hour of startup or shutdown in which a diluent cap value is used, so that emissions data from those hours can be excluded, as appropriate, from compliance calculations.

Comment 1 65 : Commenter 5830 suggests using the di luent cap values in the draft version of the Data Validation Clarification Document for Pennsylvania ’ s Continuous Source Monitoring Manual Revision No. 8 and 40 CFR Part 75, Appendix F: a minimum concentration of 5.0 percent CO 2 or a maximum

concentration of 14.0 percent O 2 may be substituted for the measured diluent gas concentration value for any operating hour in which the hourly average CO 2 concentration is < 5.0 percent CO 2 or the hourly average O 2 concentration is > 14.0 percent O 2 for boilers.

Respo nse to Comment 165 : See previous response.

5.2 U se of default MW v alue

Comment 1 66 : Commenters 20397 and 20428 state the EPA must provide a nominal default output rate in MW once electricity is generated. Commenter 20428 states that during the first hours of operation no MWs are generated and output

- based emissions values cannot be calculated (denominator is zero); once electricity is generated MW output is low for several hours and will create unusually high output

- based

emissi on values. Commenter 20428 states responsible officials should not be required to certify reports containing such values.

Commenter s 20391 and 20428 state the EPA initially proposed a default load value of 5 percent of rated capacity for startup and shutd own ; however it failed to finalize the provision. Commenter 20428 states the current proposed startup definition is insufficient to exclude low load operation and EGUs will report meaningless, grossly inflated emissions. Commenter s believe 5 percent of rated capacity is the

absolute minimum the EPA should consider and requests the EPA review data from its SO 2 data set in lb/MWh to determine whether a higher load value, e.g., 10 percent of rated capacity, may be more appropriate to e liminate hourly values above the applicable numerical limits ( C ommenter 20428 notes
that it was unable to determine from the EPA ’ s Startup TSD whether 5 percent is an appropriate nominal

value because SO 2 data are only presented in lb/MMBtu and mass).

Commenter 20391 states that the EPA should establish a default load value for output

- based emission calculations and reporting. Commenter states that during the first several hours of operation, EGUs do not generate any megawatts (zero output) and MW outpu t will remain low for several hours even once174

electricity is first generated as the EGU continues to ramp up. Commenter states that under these conditions, output

- based emissions either cannot be calculated (if MW output is zero) or will be artificially hi gh (due to low load). Commenter states that therefore, to ensure that standards that are based on testing at normal load can be achieved at low load, the EPA should provide a nominal default MW value for use in output

- based compliance calculations once ele ctricity is generated. Commenter states that in addition, because it is not possible to calculate an output

- based emissions value when there is no output (i.e., no MW), the EPA should exempt periods with no electricity generation from calculation and repor ting of output

- based (lb/GWh or lb/MWh) values.

Commenter 20400 supports the use of a minimum electrical output value for purposes of calculating compliance with the output based standard. Commenter states that because heat input and emissions

concentrati ons increase prior to the production of electricity, output

- based emissions values calculated at the beginning of electrical output when the load is very low are extremely large due to a very small load value in the denominator of the output

- based emission equations. Commenter states that based on a review of historical data, commenter believes 5 percent maximum load would be an adequate minimum value to prevent anomalously high data. Commenter provides two graphs from one of its EGUs to

illustrate this sit uation. Commenter states that the first features a typical spike in output

- based SO 2 emissions at very low loads despite SO 2 concentration increasing at a similar rate to load. Commenter states that the second graph shows the same startup with a 5 percent maximum load minimum used to

calculate the SO 2 pounds per megawatt

- hour parameter.

Commenter 20428 states that, because it is not possible to calculate an output

- based emissions value when there is no output ( i.e. , no MW), the EPA must exempt periods with no electricity generation from calculation and reporting of lb/GWh or lb/MWh values. Commenter notes that, in contrast to the requirement to report in lb/MMBtu or lb/TBtu as soon as fuel is combusted even if the available Btus are low, there are no MWs to put into the output

- based calculation until electricity is generated. Commenter maintains that although it would be possible to calculate values for such periods using a default value, those values would be completely artificial and would serve no purpose ; responsible officials should not be required to certify reports containing such values.

Commenter 20398 states that a default rate of 5 percent of the rate capacity is very low, and would likely cause compliance issues for most of the industry. Commente r suggests a default electrical production rate of 50 percent of the capacity be used for startup and shutdown. Commenter states a rate of 50 percent is reasonable default value for most sources because they are typically base loaded and operate

at over 80 percent capacity.

Commenter 20387 supports default electrical output rate for electric generation

- based standards.

Commenter 20389 supports a default electrical production rate where CEMS are required to show compliance with power output

- based standards during startup. Commenter 20387 states diluent caps and/or default electrical output rates are necessary and appropriate, as these inaccurately impact compliance averages.

Commenter 20403 supports the use of a calculated electrical production rate to calc ulate the output

based emission limits during startup and shutdown hours when electrical load is zero. C ommenter states that the most reasonable method is to utilize a formula to convert the steam being produced to electrical

output.175

Commenter 20399 state s that calculating output

- based emission rates during periods of zero electrical load will be addressed with the adoption of the EPA ’ s proposed startup definition, but the EPA should adopt a default electrical load for EGU s that opt to include startup and shutdown data in their 30

- day rolling averages. Commenter states that the EPA should utilize the 40 CFR Part 75, Appendix A.6.5.2.1(a)(1)

, defined “ minimum safe, stable load. ”

Commenter 20399 states that all MATS

- affected EGU s are also Part 75 affected EGU s requiring a monitoring plan with a defined lower boundary of range of operation. Commenter states that EGU s should be approved to use the minimum safe, stable load value for all operations below this defined output. Commenter states that operations be low minimum safe, stable load are generally considered startup, so using this value as a default electrical load allows output

- based emission rates to be more comparable to full load operations to better represent EGU performance against the MATS standards

.

Commenter 20400 states that when a startup occurs, emissions data are excluded from the time the EGU

is first fired until the EPA

- defined startup exemption period is over. Commenter notes that inevitably the exemption will end midway through a clock hou r. Commenter proposes that the exemption apply to whole clock hours in which any portion is affected by the startup exclusion which avoids the problem of hourly data being reported in ECMPS for Hg and HCl, but using only parts of these reported data points

as the 30

- day rolling average is built. Commenter maintains that applying the startup exclusion to whole hours will avoid discrepancy between the compliance values calculated by the data acquisition system ( DAS ) , and those replicated by the EPA (and other s) from hourly data. Commenter also notes that, for

an output

- based standard, there should be no calculated emissions rate during the first partial hour of electrical generation unless the EPA allows for use of a default minimum value.

Commenter 20400 sug gests this minimum value be used whenever the load is below that value, in a similar manner to the application of the Part 75 diluent cap. Commenter states that in addition, it does not appear that there is any useful purpose in calculating an output

- based emissions rate during any hour when there was no generation. Commenter states that that information is irrelevant to performance if startup emissions under the EPA ’ s current definition of startup or a possible expanded definition of startup will exclude p eriods prior to electrical generation from the compliance value. Commenter states that this would only be necessary if sorbent trap systems are used and the EPA requires that the traps

collect emissions at all times. Commenter states that in that case, it would not be possible to distinguish startup and shutdown emissions from normal operations, and it would be necessary to apply a default generation value at zero or low load to assure the EGU is not penalized in calculating an output

- based compliance value

.

Commenter 20407 states that that use of a default electrical production rate should be allowed. Commenter said that the EPA has established an option of using electrical production rates for compliance with the MATS limits. Commenter states that when no megawatts are recorded during an operating hour, no emission value can be calculated because division by zero is not possible. Commenter believes a default of 5 percent electrical production, rated by capacity in megawatts, should be allowed during period s of startup and shutdown as was proposed in 2011.

Commenter 20408 states that the EPA needs to define a floor generation level for emission limitations based on lb/MWh and recommends that the EPA adopt the proposed 5 percent of rated capacity value.176

Com menter 20425 states that based on Commenter 20428 ’ s analysis of the EPA data, the nominal default MW value should be 10 percent of rated output.

Commenter 20419 states that the EPA should recognize that, if it defines the end of startup as occurring

befor e a n EGU begins to generate electricity, which commenter does not support, the EPA must permit

EGU s to use a default production rate value to calculate output

- based emissions while the electrical load

is zero. Commenter states that if the EPA does not adopt such a default, EGU s will be unable to calculate emissions in pounds per megawatt

- hour because the denominator in the equation (megawatt

hour) will be zero.

Commenter 20429 states that that if a n EGU is in operation beyond the period of the startup exemption at very low loads, it is still in a non

- steady state startup like condition much different than normal operations. Commenter states that that output based emissions under these conditions calculat ed based on very low loads result in division by a very small MW value and very high calculated lb/GWh emission rates that do not represent actual performance of pollution control equipment. Commenter

believes that the EPA should set a minimum default MW v alue for use in output

- based compliance

calculations to correct this issue.

Commenter 5830 states that a calculated value has to be used in the case of a zero electrical load because of the undefined result of dividing by zero when calculating output

- base d emission limits during startup and shutdown hours where the electrical load is zero. C ommenter suggests converting useful thermal energy generated at startup and shutdown into an electrical load value of MWh, until the end of startup and shutdown.

Comme nters 5834 and 20418 support 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. Commenter 20418 states that to maintain consistency between th e heat rate

- based limit and the limit based on gross electric output, an appropriate default load rate should be equivalent to the load level that the average EGU reaches when producing the Part 75 diluent cap value (e.g., 5 percent CO 2 ).

Commenter 20418 discusse s default electrical production rates, based on data from its plants.

C ommenter notes that at one plant with subcritical EGU s, the default electrical production rate should be at least 5 percent of rated capacity to be comparable to a 5 percent CO 2 diluent cap, but at another plant with supercritical EGU s, it should be 20 percent. Commenter notes that the primary difference between these plants is the type of EGU employed at each plant

- one has subcritical EGU s whereas the other has supercritical E GUs. Commenter supports establishment of a default electrical production rate so it has greater flexibility in choosing a compliance option under the MATS Rule. C ommenter states that the default electrical production rate of 5 percent of rated capacity may not appropriately account for the variability in EGU operation based on boiler type or other factors. Commenter encourages the EPA to conduct further analysis on this issue to help ensure broad availability of a default value to affected

EGUs. At a minimu m, commenter recommends that the EPA employ a default electrical production rate of at least 5 percent.

Commenter 5840 states that the use of a default value when load is zero is inappropriate and that the data collected during that time should not be inc luded in calculations for lb/GWh emission rates.177

C ommenter observ e s that there appears to be a break point between 5 and 10 percent of nameplate generation capacity load where the lb/GWh emission rates tend to level out from the influence of SS

, and sugges ts setting a “‘ percent of nameplate generating capacity ”‘ as the point at which output

- based emissions should begin to be collected.

Commenter 20390 supports a default nominal electrical production rate of 25 percent of rated capacity

to be used when calc ulating emissions rates during periods of startup and shutdown or until the EGU achieves an steady state operating level of 10 percent O 2 , whichever comes first

.

Commenter 20401 supports use of a default electrical output rate for non

- mercury pollutants during startup and shutdown periods.

Response to Comment 166 : The final rule had no requirements regarding default electrical output for EGUs sharing a common stack . Upon consideration of the comments, the EPA agrees with commenters who suggest a default electrical load is needed when reporting emissions on an output basis during startup or shutdown periods for EGU s using a common stack . The reconsidered rule provides a default electrical load value that EGU owners or operators will be allowed to use durin g periods of startup or shutdown to calculate emissions rates. Once the electrical load exceeds zero, use of a default value is no longer allowed. Moreover, use of a default electrical load is not allowed during periods other than startup or shutdown. As s uggested by many commenters, the default electrical load will be equivalent to 5 percent of the maximum sustainable electrical output in megawatts of an EGU, as defined in section 6.5.2.1(a)(1) of appendix A to Part 75 and included in an EGU’s Part 75 elec tronic monitoring plan. As shown in a figure submitted by commenter 40200, this default rate is consistent with the commenter’s historical data and it removes anomalous high data without having to use higher default values (e.g., 10 percent, 25 percent, 50 percent, or other elaborate calculated values) as suggested by a few commenters. This maximum sustainable load is either the nameplate capacity of the EGU or the highest electrical load observed in at least four representative quarters of EGU operation.

When used in a common stack application, the default electrical load during periods of startup or shutdown is 5 percent of the combined maximum sustainable electrical load of the EGUs that are in startup or shutdown mode during an hour in which the electr ical load is zero. The default electrical load is allowed to be used in electrical output

- based emission rate calculations (either lb/MWh or lb/GWh) for any hour in which the actual electrical load for a n EGU venting to a common stack is zero. The EPA

cons idered, but decided against, requiring measurement of thermal heat output and conversion back into equivalent electrical output, preferring to use a simpler approach based on already

- existing requirements

of the A cid R ain P rogram.

Finally, as with the dil uent cap, the rule requires EGU owners or operators to identify each hour of startup or shutdown in which a default electrical load value is used, so that emissions data from those hours can be excluded, as appropriate, from compliance calculations

.

5.3 S orbent trap monitoring s ystems

Comment 1 6 7 : Commenters 20387, 20397, 20400, 20404, 20417, 20419, 20420, and 20428 state the

EPA should reconsider or eliminate the requirement for using sorbent trap monitoring for Hg during startup and shutdown. Commenter 20387 states that although Hg may be retroactively apportioned178

hourly based on stack flow, the actual Hg emission rate for any given hour of the trap sampling period cannot be known and notes that if the sampling period were mandated to include periods of startup, the low diluent and/or zero generation would certainly skew the rate based compliance value upwards.

Commenter 20428 states that startup monitoring would require: dedicated sets of traps for startup and shutdown, a technician standing by to chan ge the traps at the end of startup and beginning of shutdown,

post

- test leak check, and pre

- test leak check. Commenter alleges that in the case of startups, such an exercise could result in loss of up to 45 minutes of post

- startup data that otherwise would be used in the calculation of compliance. Commenter states that given the short duration of startup and the use of clean fuels during startup, such traps are unlikely to collect any meaningful data. Commenter states the same

issues for shutdown ; however

, not all shutdowns are scheduled, and the precise moment electricity generation ceases is difficult to predict. Commenter states that the pump that pulls sample through the sorbent traps can be turned off, a technician must conduct a required leak check and pull the probe and insert new traps and but would require having a technician on call 24 hours per day.

Commenter 20390 questioned how Hg collected on the traps for the time during startup would be excluded from the total Hg captured. Commenter s 20390 and 20419 state elevated Hg levels are possible during cold startup and before the scrubber or ACI/DSI systems are in operation, and will cause the entire trap collection mass to be higher than normal. Commenter 20390 further notes the diluent cap or electrical production load cap will not address this issue ; the only way to exclude the data would be to stop pulling samples during the startup or shutdown periods

.

Commenter 20429 states that that the EPA requires Hg monitoring in the final MATS rule during SS

, but provides a SS compliance exemption for Hg during these periods. Commenter states that that for

EGU s using sorbent traps for compliance, this would require swap out of Hg probes and traps promptly

when each SS period begins and ends. Co mmenter states that this requirement would be impractical and discourages the use of sorbent traps for Hg monitoring, which for some EGU s may be a much more cost effective approach than electronic Hg analyzers. Commenter believes that the EPA should exempt EGU s using sorbent traps for Hg compliance from Hg monitoring requirements during SS . Commenter adds that there should be ample SS Hg data from EGU s using electronic Hg analyzers to provide the EPA with the Hg emission data during SS for future needs.

Co mmenter 20400 states that the EPA indicated that at least one commenter suggested that traps should not be operated during SS periods. Commenter strongly encourages the EPA not to require the operation of sorbent traps during startup periods. Commenter states that sorbent trap monitoring systems are traditionally installed at stack elevations physically very close to the sample port. Commenter states that this requires travel up and down stacks which could also pose a safety risk when trap replacements a re unplanned, especially during inclement weather. Commenter states that for the safety of its employees, companies will prohibit climbing a stack during periods of high winds, rain, sleet, limited light and other

conditions. Commenter states that changing out a trap cannot necessarily be quickly accomplished. Commenter states that time is needed to safely travel up and down the stack. Commenter states that not all facilities have stack elevators and changing a trap requires manually climbing a stack. Comme nter states that many facilities, particularly ones with single EGUs, do not have the personnel on site 24 hours a day, 7 days a week with the necessary technical and safety training to for sorbent

- trap removal and replacement preceding and following an un scheduled or emergency shutdown. Based on

commenter ’s experience, it could take 2 to 6 hours to remove the existing trap, leak test, warm up the179

entire sampling system, probe and new sorbent trap, prep the sorbent trap system for restart. Commenter

states that an EGU outage could be delayed and/or extended while resources are secured to perform sorbent trap replacement. Commenter states that outage extensions would impact a company’s ability to provide reliable generation to the public.

Commenter 20400 sta tes that unlike a CEMS, a sorbent trap system collects an integrated sample over an extended time period. Commenter states that it cannot provide real

- time data because the traps have to be removed and analyzed remotely. Commenter states that it would ther efore be impossible in a trap to separate the Hg data collected during startup and shutdown periods from the Hg compliance data obtained during routine operation. Commenter states that although startup and shutdown events are relatively short, if emissions data from startup and shutdown periods are included in the compliance calculations, this could potentially skew the compliance results. Commenter states that additionally, any failed startups that occur would necessitate an unplanned trap replacement.

Co mmenter 20400 further recommends that the EPA not require separate sorbent trap monitoring for SS periods. Commenter states that that would require one system dedicated to SS measurement and a second for compliance measurement. Commenter states that two so rbent traps systems would double the number of port penetrations, maintenance, quarterly calibrations, RATAs, maintenance costs, and safety

risks involved. Commenter states that use of sorbent trap system dedicated for SS would be further complicated when there are multiple EGU s using a common stack as to timing of when to start/stop the systems. Commenter states that additionally shutdown measurement could prove uniquely difficult when the shutdown period is unplanned and of an undetermined length. Comment er states that in fact, in many cases, the duration of operation during “ shutdown ” conditions will only be a matter of seconds, from the

time a n EGU ceases generating power to when fuel is removed from the boiler. Commenter states that it

would make no sen se to operate a sorbent trap for that small period of time. Commenter states that these types of shutdowns are sudden and unpredictable events, so there would be no way to start a trap system to capture shutdown emissions. Commenter states that also, if it is necessary to separate startup emissions from shutdown emissions, it would be necessary to change traps between a shutdown and the subsequent startup. Commenter states that that could create unnecessary delays in returning a n EGU to
service after a brie f outage, for example, if a n EGU were to trip from service due to some fault and quickly restart or if a n EGU needed to come offline overnight due to low electrical demand but must be prepared to come back online to meet the next day ’ s load demand.

Commenter 20400 states that work practice standards during startup and shutdown assure Hg is controlled to the extent possible during these periods. Commenter states that collecting data during startup and shutdown will serve no purpose relative to complia nce with MATS. Commenter states that if the EPA needs to collect startup and shutdown data to better understand performance for a future rulemaking, that need can be addressed through the ICR process where the EPA demonstrates the need and identifies a sys tematic plan to gather the data. Commenter states that

, in fact, that should not be necessary because there should be sufficient data reported under MATS for startup and shutdown

emissions from EGU s that will be operating Hg CEMS. Commenter states that if the EPA believes it is necessary under MATS to define some value for startup and shutdown emissions for each EGU

, commenter recommends use of a onetime startup sampling event for the EGU to estimate emissions for all future startup periods. Commenter state s that where a facility is comprised of multiple generators

with like

- kind boilers and AQCS systems, commenter recommends that a common emissions factor be

utilized across those sources. Commenter states that another alternative would be to assign default180

emission values based on the fuel being burned each hour during the startup or shutdown and the controls being employed during each hour. Commenter states that those values could be established by the EPA or the EPA could require the utility to develop the default emissions factors similar to the procedures under Part 75 for data substitution.

Commenter 20408 notes that in order to measure Hg as required by the MATS rule, different monitoring technologies are available and acceptable for compliance with th is rule. Commenter also notes that the EPA is requiring that Hg monitoring systems be operational during startup but that these data are not used when determining compliance with the 30

- or 90

- day rolling average emission limit. Commenter

indicates that fo r sorbent traps, monitoring during a startup or shutdown is somewhat problematic because the sorbent trap monitoring methodology produces an integrated Hg sample typically spanning 3 to 7 days. In order to delineate startup Hg emissions from normal operati on, separate traps for SS and normal operation would need to be utilized due to the leak check and other Q/A requirements. Commenter alleges that with the sorbent trap methodology, it will be all but impossible to measure shutdown emissions especially in t he event of a forced, unscheduled shutdown caused by a boiler system failure. Therefore, commenter suggests that the EPA modify how SS Hg emissions are handled for sorbent trap monitoring systems. Commenter recommends that the EPA not require monitoring during startup or shutdown, similar to what is done if quarterly stack testing is being used as with PM or HCl

, and that the EPA utilize data from the integrated sample adjusted by the percentage of coal consumed ( because most Hg is in the coal fuel) during startup with that typical for that sampling period.

Commenter 20420 suggests that EGUs should be required to begin collecting data with sorbent trap monitoring systems after startup ends, throughout normal operations, and until s hutdown begins.

C ommenter states that this will allow EGUs to collect all of the emission data required to comply with the Hg emission limit and eliminate the problem of including startup and shutdown emissions data in Hg

30

- boiler operating day rolling av erage emission rates.

Response to Comment 167 : After consideration of comments received on Hg monitoring during startup or shutdown periods using sorbent trap monitoring systems, the EPA decided that the final reconsidered rule will expand the Hg monitoring flexibility available to EGU owners or operators. The reconsidered rule contains three approaches for measuring Hg emissions during periods of startup or shutdown. In the first approach, EGU owners or operators will remain able to use Hg CEMS f or measuring Hg emissions and to exclude for compliance purposes Hg emissions recorded during periods of startup or shutdown.

The second approach relies on at least two separate sorbent monitoring systems. Although the final rule had no prohibition again st an EGU owner or operator using one sorbent trap monitoring system for compliance purposes during periods other than startup or shutdown and one (or more) sorbent trap monitoring systems for periods of startup or shutdown through the use of a non

- redunda nt backup system (per section 2.2. 2 of Appendix A to subpart UUUUU), the reconsidered rule clarifies that two separate sorbent monitoring systems are allowed. Note that the sorbent trap monitoring system used for periods of startup or shutdown could use th e smaller sorbent tubes required by Method 30B; use of the smaller volume sorbent tubes should increase detection levels, thus addressing some commenters’ concerns about potential non

- detection. As an aside, consi stent non

- detection measurement is not

nece ssarily a problematic outcome, because collection is to find out what the Hg emissions are during periods of startup or shutdown. Reliance on this second approach would address one c ommenter’s concern that Hg compliance data could not be separated from Hg data collected during startup and/or181

shutdown periods. When an EGU with at least two such systems (one for periods of startup or shutdown and the other for all other periods) entered into a startup or shutdown period, the EGU owner or operator

could switch monitoring systems either manually or automatically.

The third approach, relying on just one sorbent trap monitoring system for all periods of operation (startup, shutdown, and normal), will be identified in the reconsidered rule as a viable option for Hg monitoring, and, for EGU owners or operators who choose this option, the rule will allow data collected during startup or shutdown periods to be used for compliance purposes. EGU owners or operators may find that this third approach would work well for those instances in which sudden and unpredictable shutdown events occur, for there would be no need to swap sorbent trap monitoring systems to capture shutdown emissions. In addition, use of just one sorbent trap monitoring system would obviate one

comment er’s concern over setting the proportionality rate based on flows during startup or shutdown periods. Consistent with the view of some commenters, the EPA expects little impact on Hg emissions during startup or shutdown periods, for, as explained above, cl ean fuels are to be used during those periods; default diluent and electrical output values, which tend to constrain emissions, will be available for use; and emissions occurring during those periods will be included in a 30

- (or 90

- ) boiler operating day rolling average. As explained earlier, figures depicting Hg emissions during startup periods for an EGUs with individual and common stacks suggest that startup Hg emissions account for less than 5

percent of the allowable emissions limit even without compl ying with the final work practice . EGUs would need to operate such that average hourly Hg emissions for the remaining time during the quarter were up to 95 percent of the 30

- boiler operating day emission limit. 26

Along with flexibility in choosing a Hg mo nitoring technique comes the responsibility for carefully considering which approach works best for an EGU owner or operator. As part of an EGU owner or operator’s rubric for choosing which Hg measurement approach to use, the EGU owner or operator

should t ake into account all factors, including but not limited to factors identified by commenters such as safety, reliability, and ease of use, as well as other factors not mentioned by commenters such as consequences of failure to provide necessary data and tot al (not just initial) system costs. As an example, EGU owners or operators should remember that any process operating hour for which quality assured Hg concentration data are not obtained is counted as an hour of monitoring system downtime, per

section 1.4 of Appendix A to subpart UUUUU. Therefore, if an EGU owner or operator believes change

- out of sorbent monitoring traps may take too long, other approaches may be more suitable. An EGU owner or operator should carefully consider all costs

- not only of sor bent tubes, analyses, and

associated labor costs, but also the potential costs of non

- compliance due to data gaps.

Finally, the EPA disagrees with c ommenters who claim that collecting data during startup and shutdown will serve no purpose relative to comp liance with MATS and indicated that if the EPA needs to collect startup and shutdown data to better understand performance for a future rulemaking, that can be addressed through the ICR process where the EPA demonstrates the need and identifies a systemati c plan to gather the data. As explained in the final rule preamble, 27 collection of startup and shutdown information will provide the EPA with information to more fully analyze the ability and appropriateness of establishing numeric emissions and operating limits during periods of startup or shutdown so the issue can be addressed as part of the ongoing 8

- year review of this rule. Collection of these data as part

26 See figure 9 in Attachment I and figure in Attachment V from Commenter 20428.

27 See 77 FR 9382 (February 16, 2012).182

of the rule will also serve to reduce, if not eliminate, future ICR requests on this topic. The E PA also disagrees with commenters who wish to place all startup and shutdown information on those EGU owners or operators who choose to use Hg CEMS, for EPA remains interested in how well sorbent tube monitoring systems operate during periods of startup or shutdown. Not collecting that information from those systems would leave a gap in the EPA’s knowledge base.

5.4 Other c oncerns

Comment 1 68 : Commenter 20403 states concerns with the ongoing regulatory efforts related to air by

the EPA (i.e., CASPR (on appeal), MATS, 1

- hr SO 2 NAAQS, 1

- hr Ozone NOx Standards, other air emission rule makings and the most recent announcements to control CO 2 emissions) will result in more stringent CO 2 , CO, NOx, SOx, PM

, and other standards that will need t o be complied with at the defined end of startup. Commenter states that the rush to tie startup to emissions rather than to flame or bed stabilization is problematic and will create greater problems over time.

Response to Comment 168 : The EPA is establish ing a work practice standard specific to the control of HAP emissions regulated under CAA section 112. The work practice itself acknowledges that other requirement s applicable to the source may require control at different

times. Sources are not required to comply with those other standards based on the MATS definitions and work practice standard s , even though we believe that compliance with the work practice will likely lead sources to more quickly comply with other non

- HAP standards because

the controls for HAP co

- control other non

- HAP air pollution and the fact that clean fuels will be maximized throughout the defined startup period

.

Comment 1 69 : Commenter 20403 supports the use of main stack requirement if by

- pass is allowed in emergencies.

Response t o Comment 169 : This comment is outside the scope of the reconsidered rule, so no response is required.

Comment 17 0 : Commenter 5848 states that the EPA should make the definitions for startup and shutdown in the Utility NSPS, Utility MATS

, and Industrial B oiler MACT rule (40 CFR 63, subpart DDDDD) the same or at least very similar.

Response to Comment 17 0 : T he EPA generally believes that startup and shutdown definitions for the subject rulemakings should reflect data and practices from the subject subcategories , particularly in the

case of EGUs because of the considerable data and information available to the EPA ; however, when categories are similar, as with boilers and EGUs, the A gency may consider the practices employed in the different categorie s when developing work practices standards

.

Comment 17 1 : Commenters 20409, 20423, and 5831 state that, to avoid any confusion here or in subsequent efforts by states or the EPA to develop permit or other compliance requirements directed at other CAA provisions, the final MATS SSM regulation should conclude and definitively make clear that

the MATS SSM definition of startup should only apply to MATS SSM compliance and not for other

emission compliance determination purposes. Commenter 20409 states that, because some of its members are presently installing emission controls for HAP purposes, it cannot co nclude that all its183

members can achieve successful startup under the option proposed and meet their HAP emission compliance obligations under this proposal. Commenter 20409 states that

, however

, it is reasonably certain that at least some cooperatively own ed EGUs will not be able to achieve other CAA compliance requirements if other emissions obligations were to commence when the proposed HAP startup period

ends. Commenter 20409 states that the EPA ’ s Startup TSD supports this conclusion. Commenter s 5831

and 20423 believe that an unintended consequence of this rulemaking could be that the incorporation of

time

- based work practice compliance obligation that does not relate in a real way to any permit condition or to any actual criteria pollutant NAAQS or N ESHAP emission limitation may lead to a perceived compliance issue

.

Commenter 20436 states that the EPA should make explicit that any decision to allow coal combustion prior to full operation of APCD is limited to the MATS rule and does not apply to air q uality or health

based standards incorporated in SIPs.

Response to Comment 171 : The EPA believes that the definitions incorporated within this rule ( 40 CFR subpart UUUUU) are only applicable to this rule unless incorporated intentionally into another rule and, thus, commenter s’ concerns are unfounded

.

Comment 17 2 : Commenter 20419 requests that the EPA clarify how EGU s, when calculating the 30

- boiler operating day rolling average, should use CEMS data from hourly periods that include both minutes of normal operation and minutes of startup or shutdown. Commenter states that the MATS requires that EGU s choosing to comply with the emissions limits using CEMS calculate the 30

- boiler operating day rolling average (or the alternate 90

- boiler operating day rolling average for Hg) using the hourly average CEMS data. Commenter notes that some hourly averages may include data fro m both minutes of normal operation and minutes of startup or shutdown. Commenter states that because the MATS prohibits EGU s from using data recorded during startup or shutdown to demonstrate continuous compliance, commenter assumes that EGU s are to exclud e hourly averages that include minutes of startup or shutdown from the calculation of the 30

- boiler operating day rolling average. Commenter requests that the EPA confirm that this is the proper procedure for calculating the 30

- boiler operating day rolling average to demonstrate continuous compliance at EGU s employing CEMS.

Commenter 20413 agrees that the startup and shutdown operations at an EGU are not suitable to be included in emissions calculations for determining compliance with emission limits becau se it is impossible to successfully and safely operate the pollution control equipment at all points during the full startup and shutdown periods of operation.

Response to Comment 172 : The reconsidered rule requires owners or operators to identify each hour of startup or shutdown. As identified in the rule, any fraction of an hour in which startup or shutdown occurs constitutes a full hour of startup or shutdown. Except for EGU owners or operators who choose to demonstrate compliance with Hg emissions by including startup or shutdown emissions in their sorbent trap monitoring systems in compliance calculations, EGU owners or operators are to exclude emissions from any hour of startup or s hutdown from their compliance calculations, regardless of pollution control device operation.

Comment 17 3 : Commenter 5833 states that the SSM proposal will impact electric reliability and an overall increase in emissions could occur because of damage to a ir pollution control equipment.184

Response to Comment 17 3 : The EPA does not agree that the final work practice will lead to reliability concerns and the commenter has not provided compelling information to the contrary. The EPA also

believes that the final d efinitions and work practices applicable during periods of startup and shutdown

ha ve been demonstrated at the best performing sources

. EGU s that are unable to comply will have to make physical and/or operational changes as necessary to comply with the final rule

.

5.5 Support for other commenters/comments

Comment 1 74 : Commenters 20391, 20392, 20395, and 20397 support the comments made by

Commenter 20428. Commenter 2 0418 supports the comments submitted by Commenter 20428 with some exceptions.

Commenter 20414 has actively commented in this rulemaking docket, including in the initial comment period for the EPA ’ s reconsideration of certain new source and SS issues, published in the Federal Register on November 30, 2012. Commenter incorporates those commen ts, except to the extent

modified in its current comments , and the comments filed throughout this regulatory docket, by

reference.

Commenter 20416 supports and incorporates by reference the comments made by Commenter 20396.

Commenter 20426 fully endorses and incorporates by reference those comments submitted by Commenters 20396, 20397, and 20428 on this proposal.

Commenter 20430 is a member of the National Rural Electric Cooperative Association (NRECA) and the Gulf Coast Lignite Coalition (GCLC) and supp orts comments filed those organizations.

Response to Comment 1 74 : These comments require no response as the individual comments have

been addressed elsewhere in this document

.

Comment 1 75 : Commenter 20419 believes that its proposed changes as described i n its prior comments

would address site

- specific operating constraints at many EGUs without lessening the environmental benefits the EPA anticipates will be achieved by the final rule.

Response to Comment 1 75 : T he EPA believes that commenter ’ s issues have been addressed elsewhere

in this document

.

5.6 Out of Scope

Comment 1 76 : Commenter 20411 states that

, although the EPA did not ask for comments on quarterly stack testing in this reconsideration

, it would like to restate the comments made in a previous

reconsideration. Commenter states that the EPA incorrectly concludes that many existing affected coal

fueled EGUs will be using CEMS to monitor their PM emissions and therefore will have no interest in demonstrating compliance through quarterly PM stack tests. Commenter states that the approach to compliance with PM requirements is often not the same as the approach for Hg because there are many

EGU s with very low PM levels for which there is no great n eed for the “ frequent feedback ” of PM185

CEMS. Commenter states that in such cases, it is still appropriate to utilize quarterly stack testing rather than CEMS as the method for demonstrating compliance with the filterable PM limit.

Commenter 20411 believes it is important that the EPA retain the quarterly stack testing compliance option. Commenter states that it is appropriate for low

- PM emitting EGU s to utilize quarterly stack testing. Commenter states that additionally, the lack of reliable HCl CEMS will necessitate that EGU s without SO 2 controls perform quarterly stack testing to show compliance with the HCl limit. Commenter

states that

, therefore, it is its intent to utilize quarterly stack testing for showing compliance with the PM

and HCl limits at its existing EGU s and it is planning to continue to do so into the future for MATS compliance. Therefore, commenter requests that the EPA retain this option for PM compliance monitoring.

Response to Comment 1 76 : Quarterly stack testing for new coal

- and oil

- fired EGUs was not at issue in this reconsideration (it was addressed in the final reconsideration of the new

- source emission limits;

see 78 FR 24073, April 24, 2013) and, thus, no response is required.186 Table 3. List of Commenters on November 30, 2012

, Proposal 28

Commenter Name Commenter Organization EPA Docket ID

Terry M. Hogan Wabash Valley Power Association,

Inc. EPA

- HQ

- OAR

- 2009

- 0234

- 20243

Eric Redman Summit Power EPA

- HQ

- OAR

- 2009

- 0234

- 20245

Bart Sponseller Wisconsin Department of Natural Resources (WDNR) EPA

- HQ

- OAR

- 2009

- 0234

- 20246

Claire M. Olson Basin Electric Power Cooperative EPA

- HQ

- OAR

- 2009

- 0234

- 20247

Walter Stone NRG Energy, Inc. EPA

- HQ

- OAR

- 2009

- 0234

- 20248

Bob Holmes Omaha Public Power District (OPPD) EPA

- HQ

- OAR

- 2009

- 0234

- 20251

Lisa Jaeger Edgecombe Genco LLC and Spruance

Genco LLC EPA

- HQ

- OAR

- 2009

- 0234

- 20252

Joe L. Citta, Jr. Nebraska Public Power District (NPPD) EPA

- HQ

- OAR

- 2009

- 0234

- 20254

Patrick O ’ Loughlin Buckeye Power, Inc. EPA

- HQ

- OAR

- 2009

- 0234

- 20255

Raymond L. Evans FirstEnergy Corp. EPA

- HQ

- OAR

- 2009

- 0234

- 20256

Kenneth J. Anderson Ameren Corporation EPA

- HQ

- OAR

- 2009

- 0234

- 20257

Mark Thoma Otter Tail Power Company EPA

- HQ

- OAR

- 2009

- 0234

- 20262

PJ Becker City of Springfield, Cit y Water Light

and Power EPA

- HQ

- OAR

- 2009

- 0234

- 20267

Debra J. Jezouit Baker Botts L.L.P. et al. on behalf of

The Class of ‘ 85 Regulatory Response Group EPA

- HQ

- OAR

- 2009

- 0234

- 20269

Chris M. Hobson Southern Company EPA

- HQ

- OAR

- 2009

- 0234

- 20270

Cathy S. Woollums MidAmerican Energy Holdings Company EPA

- HQ

- OAR

- 2009

- 0234

- 20271

Jay Hudson Santee Cooper EPA

- HQ

- OAR

- 2009

- 0234

- 20272

John A. Riley Bracewell & Giuliani LLP, on behalf of Las Brisas Energy Center, LLC EPA

- HQ

- OAR

- 2009

- 0234

- 20273

Michael J. Nasi Jackson Walker, LLP, on behalf of Gulf Coast Lignite Coalition (GCLC) EPA

- HQ

- OAR

- 2009

- 0234

- 20275

28 Only those commenters providing comment on the startup/shutdown reconsideration issues are listed.187

Jon Madison Montana

- Dakota Utilities Company EPA

- HQ

- OAR

- 2009

- 0234

- 20276

Greg F. Myers Consumers Energy EPA

- HQ

- OAR

- 2009

- 0234

- 20277

Myra Glover Entergy Services, Inc. EPA

- HQ

- OAR

- 2009

- 0234

- 20279

Kelly J. Barr Salt River Project (SRP) EPA

- HQ

- OAR

- 2009

- 0234

- 20280

J. Michael Geers Duke Energy EPA

- HQ

- OAR

- 2009

- 0234

- 20281

Lee B. Zeugin, et al. Utility Air Regulatory Group (UARG) EPA

- HQ

- OAR

- 2009

- 0234

- 20282

Stephen Fotis Generators for Clean Air (GCA) EPA

- HQ

- OAR

- 2009

- 0234

- 20283,

- 20288

Jeffrey A. McNelly ARIPPA EPA

- HQ

- OAR

- 2009

- 0234

- 20285

Zak Covar Texas Commission on Environmental Quality (TCEQ) EPA

- HQ

- OAR

- 2009

- 0234

- 20286

Chet Thompson Crowell & Moring LLP, on behalf of Homer City Generation, L.P. EPA

- HQ

- OAR

- 2009

- 0234

- 20287

Henry E. Eby Lower Colorado River Authority (LCRA) EPA

- HQ

- OAR

- 2009

- 0234

- 20289

Paul M. Ling Kansas City Power & Light Company (KCP&L) EPA

- HQ

- OAR

- 2009

- 0234

- 20291

J. Michael Brown Ohio Valley Electric Corporation EPA

- HQ

- OAR

- 2009

- 0234

- 20294

Quinlan J. Shea Edison Electric Institute (EEI) EPA

- HQ

- OAR

- 2009

- 0234

- 20295

Brian Brazil TransAlta Centralia Generation, LLC EPA

- HQ

- OAR

- 2009

- 0234

- 20297

Norman Schilling General Electric Company (GE) EPA

- HQ

- OAR

- 2009

- 0234

- 20299

Michael L. Krancer Pennsylvania Department of Environmental Protection (PDEP) EPA

- HQ

- OAR

- 2009

- 0234

- 20302

Joseph G. Eutizi San Miguel Electric Cooperative EPA

- HQ

- OAR

- 2009

- 0234

- 20303

Melvin E. Keener Coalition for Responsible Waste Incineration (CRWI) EPA

- HQ

- OAR

- 2009

- 0234

- 20304

David Woodsmall Sierra Club, et al. EPA

- HQ

- OAR

- 2009

- 0234

- 20305

Gregory Ryan DTE Energy EPA

- HQ

- OAR

- 2009

- 0234

- 20306188

John M. McManus American Electric Power (AEP) EPA

- HQ

- OAR

- 2009

- 0234

- 20308

Berdell Knowles JEA EPA

- HQ

- OAR

- 2009

- 0234

- 20321

Joaquin C. Flores Guam Power Authority EPA

- HQ

- OAR

- 2011

- 0044

- 5785

Megan Murphy PPL Services Corporation EPA

- HQ

- OAR

- 2011

- 0044

- 5803189

Table 4. List of Commenters on June 25, 2013, Comment Period Reopening

Commenter Name Commenter Organization EPA Docket ID

John T. Graves Minnkota Power Cooperative, Inc. EPA

- HQ

- OAR

- 2009

- 0234

- 20384

P. J. Becker City of Springfield, City Water Light & Power (CWLP) EPA

- HQ

- OAR

- 2009

- 0234

- 20387

John A. Paul Regional Air Pollution Control Agency of Dayton, Ohio (RAPCA) EPA

- HQ

- OAR

- 2009

- 0234

- 20388

Mark J. Sedlacek Los Angeles Department of Water and Power (LADWP) EPA

- HQ

- OAR

- 2009

- 0234

- 20389

Betsy Natz Institute of Clean Air Companies (ICAC) EPA

- HQ

- OAR

- 2009

- 0234

- 20390

Pamela F. Faggert Dominion Resources Services, Inc. EPA

- HQ

- OAR

- 2009

- 0234

- 20391

Barbara A. Walz Tri

- State Generation & Transmission Association, Inc. EPA

- HQ

- OAR

- 2009

- 0234

- 20392 , 20394

Jay Hudson Santee Cooper EPA

- HQ

- OAR

- 2009

- 0234

- 20393

Chris M. Hobson Southern Company EPA

- HQ

- OAR

- 2009

- 0234

- 20395,

- 20412

Quinlan J. Shea, III Edison Electric Institute (EEI) EPA

- HQ

- OAR

- 2009

- 0234

- 20396

John M. McManus American Electric Power (AEP) EPA

- HQ

- OAR

- 2009

- 0234

- 20397

Grant Rodway Bison Engineering, Inc. EPA

- HQ

- OAR

- 2009

- 0234

- 20398

Brian W. Green NRG Energy, Inc. EPA

- HQ

- OAR

- 2009

- 0234

- 20399

J. Michael Geers Duke Energy EPA

- HQ

- OAR

- 2009

- 0234

- 20400

Brittany Barrientos Kansas City Board of Public Utilities EPA

- HQ

- OAR

- 2009

- 0234

- 20401

Lorraine Krupa Gershman A merican Chemistry Council EPA

- HQ

- OAR

- 2009

- 0234

- 20402

Jeffrey A. McNelly ARIPPA EPA

- HQ

- OAR

- 2009

- 0234

- 20403

Paul M. Ling. Kansas City Power and Light EPA

- HQ

- OAR

- 2009

- 0924

- 20404

Scott J. Nally Ohio EPA EPA

- HQ

- OAR

- 2009

- 0234

- 20405

Brian Brazil TransAlta EPA

- HQ

- OAR

- 2009

- 0234

- 20406190

Cathy S. Woollums MidAmerican Energy Holdings Company EPA

- HQ

- OAR

- 2009

- 0234

- 20407

Ken Anderson Ameren Corporation EPA

- HQ

- OAR

- 2009

- 0234

- 20408

Rae E. Cronmiller National Rural Electric Cooperative Association (NRECA) EPA

- HQ

- OAR

- 2009

- 0234

- 20409

Bob Holmes Omaha Public Power District (OPPD) EPA

- HQ

- OAR

- 2009

- 0234

- 20410

Joe L. Citta, Jr. Nebraska Public Power District (NPPD) EPA

- HQ

- OAR

- 2009

- 0234

- 20411

Jeff Burkett The Empire District Electric Company EPA

- HQ

- OAR

- 2009

- 0234

- 20413

Michael J. Nasi Gulf Coast Lignite Coalition (GCLC) EPA

- HQ

- OAR

- 2009

- 0234

- 20414

Lisa M. Jaeger Council of Industrial Boiler Owners (CIBO) EPA

- HQ

- OAR

- 2009

- 0234

- 20415

Jon Madison Montana Dakota Utilities Co. EPA

- HQ

- OAR

- 2009

- 0234

- 20416

Megan Murphy PPL Services Corporation EPA

- HQ

- OAR

- 2009

- 0234

- 20417

Kara M. Montalvo Salt River Project Agricultural Improvement and Power District (SRP) EPA

- HQ

- OAR

- 2009

- 0234

- 20418

Debra J. Jezouit and

Allison Watkins Class of ‘ 85 Regulatory Response Group EPA

- HQ

- OAR

- 2009

- 0234

- 20419

Jerry Purvis East Kentucky Power Cooperative EPA

- HQ

- OAR

- 2009

- 0234

- 20420

Lisa M. Jaeger Bracewell & Giuliani LLP, on behalf of Edgecombe Genco LLC, and Spruance Genco LLC EPA

- HQ

- OAR

- 2009

- 0234

- 20421

Whitney Ferrell Environmental Integrity Project EPA

- HQ

- OAR

- 2009

- 0234

- 20422

Claire M. Olson Basin Electric Power Cooperative EPA

- HQ

- OAR

- 2009

- 0234

- 20423

Bill Mathews Cleco Power LLC EPA

- HQ

- OAR

- 2009

- 0234

- 20424

Raymond L. Evans FirstEnergy EPA

- HQ

- OAR

- 2009

- 0234

- 20425

J. Mi chael Brown Ohio Valley Electric Corporation (OVEC)/ Indiana

- Kentucky Electric Corporation (IKEC) EPA

- HQ

- OAR

- 2009

- 0234

- 20426

Sanjay Narayan Sierra Club et al. EPA

- HQ

- OAR

- 2009

- 0234

- 20427 , 20438

Lee B. Zeugin et al. Utility Air Regulatory Group (UARG) EPA

- HQ

- OAR

- 2009

- 0234

- 20428,

- 20433

, - 20437191

John W. Myers Tennessee Valley Authority (TVA) EPA

- HQ

- OAR

- 2009

- 0234

- 20429

Joseph G. Eutizi San Miguel Electric Cooperative, Inc. EPA

- HQ

- OAR

- 2009

- 0234

- 20430

John M. Ross Northern Indiana Public Service Company (NIPSCO) EPA

- HQ

- OAR

- 2009

- 0234

- 20431

Eric Schaeffer Environmental Integrity Project EPA

- HQ

- OAR

- 2009

- 0234

- 20436

Vincent Brisini Pennsylvania Department of

Environmental Protection EPA

- HQ

- OAR

- 2011

- 0044

- 5830

Wayne E. Penrod Sunflower Electric Power Corporation EPA

- HQ

- OAR

- 2011

- 0044

- 5831

Thomas N. Effinger SCANA EPA

- HQ

- OAR

- 2011

- 0044

- 5833

Henry Eby Lower Colorado River Authority (LCRA) EPA

- HQ

- OAR

- 2011

- 0044

- 5834

Kimberly D. Mireles Luminant EPA

- HQ

- OAR

- 2011

- 0044

- 5840

David A. Buff Golder Associates on behalf of New Hope Power Company EPA

- HQ

- OAR

- 2011

- 0044

- 5848