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Chapter 1

Applicability

Contents

1.1 General................................................................................................................................. 2

1.2 Applicability Criteria ........................................................................................................... 6

1.3 Steam Generating Unit....................................................................................................... 15

1.4 Stationary Combustion Turbine......................................................................................... 15

1.4.1 Potential Electric Output.................................................................................................. 15

1.4.2 Large/Small Combustion Turbine Cut-point ................................................................... 24

1.4.3 Oil-fired Combustion Turbines........................................................................................ 24

1.5 Exemptions ........................................................................................................................ 25

1.6 CHP.................................................................................................................................... 26

1.7 Non-fossil-fired EGUs (e.g., Biomass).............................................................................. 27

1.8 Integrated and Co-located Non-emitting Energy Generation Equipment.......................... 31

1.9 Compliance Period............................................................................................................. 32

1.10 Periods of Startup, Shutdown, and Malfunction................................................................ 35

1.11 Other .................................................................................................................................. 39
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1.1 GENERAL

Comment 1.1-1: Commenters (0192, 0195, 0215, 0242) identified several inconsistencies 

between the applicability criteria for new units, modified and reconstructed units, and existing 

units, and the commenters strongly urged the EPA to correct these inconsistencies across the 

three proposed section 111 rules because they believe that section 111 requires the same 

applicability provisions for new, modified, reconstructed, and existing sources and the 

commenters believed the proposed inconsistent applicability criteria will cause significant 

confusion during implementation. Commenters (0195, 0242) noted that the proposal for 

modified and reconstructed sources did not include the one-third sales criterion, the 219,000 MW 

hour criterion, or the 10 percent fossil fuel criteria that was previously included in the proposal 

for new boilers and IGCC facilities. 

Commenter (0242) responded to the EPA's request for comments on "a multitude of additional 

changes" to the applicability criteria; the commenter stated that in combination with the proposed 

changes to applicability, the commenter found it difficult to determine exactly what the EPA is 

proposing. Commenter (0242) stated that it was difficult to determine if proposed applicability 

changes apply to modified and reconstructed sources, new sources, or existing sources. 

Commenter (0242) also stated that it was unclear if proposed revisions to applicability provisions 

were relevant to only GHG emissions or to all regulated pollutants regulated under Part 60. 

Commenter (0192) stated that the proposal for modified and reconstructed units further increases 

uncertainty about the set of sources that will be affected under section 111 proceedings for 

greenhouse gases. Commenter (0192) asserted that proposed differences in applicability for 

modified and reconstructed sources compared to the preceding applicability provisions for new 

sources are unlawful and cited two cases (Gustafson v. Alloyd Co., 513 U.S. 561, 570 (1995) and 

Department of Revenue of Oregon v. ACF Indus., Inc., 510 U.S. 332, 342 (1994)) where the 

courts recognized that the normal rule of statutory construction requires that identical words used 

in different parts of the same act are intended to have the same meaning.

Commenter (0150) stated that the EPA should retain the one-third sales criterion and the low 

fossil use criterion for modified and reconstructed sources because section 111 prohibits 

expansion of the scope of applicability for modified and reconstructed sources compared to the 

scope proposed for new units in January 2014. The commenter believed that the Agency cannot 

define a source category differently for new, modified, and reconstructed sources. The 

commenter also believed that the Agency cannot propose to alter the applicability criteria 

for new sources in the proposed rule for modified and reconstructed sources. Commenter (0150) 

opposed the proposal's basis for eliminating the one-third sales criterion and the low fossil use 

criterion (to broaden the scope of subsequent 111(d) guidelines) because the commenter believed

that section 111 requires the Administrator to determine whether to list a source category based 

only on the merits of regulating new sources in that category and without regard for whether 

existing sources will eventually be subject to section 111(d) regulations.

Commenter 0215 stated that EPA has not provided a rationale for eliminating the low fossil use 

criterion, and its removal is therefore unsupported by the record.
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Commenters 0142, 0149, 0229 opposed inclusion of numerous applicability options for 

combustion turbines in the proposal; commenter (0149) believed each option implies a different 

set of affected sources and a different set of emissions standards. Commenter (0142) stated that 

the proposal was not the appropriate forum for soliciting comments on various applicability 

criteria being considered by the EPA because providing the public an opportunity to comment on 

the merits of listed options does not satisfy the federal administrative procedure's requirement to 

provide the public with an opportunity to comment on specific EPA proposals. Commenter 

(0142) stated that in the absence of a specific EPA proposal, specific EPA analyses, and specific 

EPA documentation, the commenter could not effectively comment on the proposed revisions to 

40 CFR Part 60. Commenters (0149, 0229) acknowledged that some of the options may seem 

reasonable in theory but opposed inclusion of numerous applicability options because the 

commenter believed proposed regulations with numerous options are inconsistent with the EPA's 

statutory obligation to demonstrate that the associated standards are achievable for all the 

different sets of units implicit in each applicability option; commenter (0149) cited the following 

case to support these concerns: Essex Chem. Corp. v. Ruckelshaus, 486 F.2d 427, 433-34 (D.C. 

Cir. 1973); and commenters (0142, 0149, 0229) asserted that the EPA cannot finalize any 

standards that the Agency cannot demonstrate are reasonable or standards for which EPA has not 

provided stakeholders sufficient opportunity for notice and meaningful comment.

Commenter 0193 supported the EPA's inclusion of multiple applicability options in the proposal 

and provided comments on each option considered by the EPA.

Response 1.1-1: The applicability in this final rule is consistent for all affected units. The 

rationale for the final applicability is included in the preamble to this final rule.

Comment 1.1-2: Commenter 0267 asserted that this proposed revision is illegal because it could 

impose regulations on non-emitting power generators and because it could significantly expand 

activities considered to be stationary sources under the CAA without providing well-defined 

limits, and the commenter stated that the proposal failed to adequately explain the need, basis, 

and impacts of this proposed revision.

Response 1.1-2: The applicability in this final rule includes integrated equipment, which may 

or may not be non-emitting, but does not include co-located non-emitting equipment.

Comment 1.1-3: Commenter 0215 noted that in the preamble to the Proposed Standards, EPA 

solicits comment on "the delineation between a reconstructed source, which would be subject to 

standards proposed in today's action, and a newly constructed source, which would be subject to 

standards proposed in the January 2014 proposal, for those situations where significant 

equipment is being replaced (enough to exceed the reconstruction threshold) but the entire unit is 

not being rebuilt." 79 Fed. Reg. at 34,971. 

The commenter stated that in any event, the Agency has not provided any reasonable basis for 

altering its 40-year-old standard for identifying and regulating reconstructed sources. The 

commenter EPA claims that its regulations provide no "guidance on when an existing source 

replaces components to such a degree that it goes beyond a reconstruction and becomes 

essentially a newly constructed source." 79 Fed. Reg. at 34,971. The commenter stated this 

argument is nonsensical: the reconstruction analysis itself is that "guidance." The commenter 
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stated the entire purpose of the reconstruction analysis is to determine when an existing unit has 

become "essentially a newly constructed source."

Commenter (0131) believed that the final rule should more clearly specify the 50 percent cost 

threshold that triggers applicability of the standard for reconstructed sources. Commenter (0131) 

stated that the EPA should expand the definition of relative cost to include the definition of a 

"comparable facility." Commenter (0131) asked if the 50 percent cost threshold refers to 50 

percent of the cost of a new plant using the same technology or 50 percent of the cost of new 

plant with comparable power generation. Commenter (0131) was unsure if an existing coal plant 

being evaluated against the 50 percent threshold should use the cost of a new coal plant or the 

cost of a new combined cycle natural gas plant as the basis for the threshold calculation.

Commenters (0260, 0267) responded to the EPA's request for comments on the feasibility 

of setting an upper capital cost threshold for triggering the standards for reconstructed sources; 

the commenters stated that the EPA should not set such a threshold because reconstructed units 

should not be subjected to standards of performance that are set based on BSER for newly 

constructed units. Commenter (0260) stated that the EPA has provided no analysis supporting

application of standards for new sources to reconstructed sources, and the commenter

believed that the proposed standards for new units cannot constitute BSER for reconstructed 

units because EPA has undertaken no analysis to determine whether such technology has been 

"adequately demonstrated" for reconstructed sources.

In response to requests for comments on revising the capital cost threshold, commenter (0131) 

stated that such a revision is unnecessary because conditions in power markets drive the 

decisions of plant owners.

Commenter (0131) opposed applying both the 111(d) standard and the standard for reconstructed 

sources to projects at reconstructed facilities because the commenter believed that applying both 

standards would discourage plant owners from engaging in projects to improve efficiency. 

Accordingly, commenter (0131) recommended that only the section 111(d) standard should 

apply to reconstructed facilities. 

Commenter (0195) recommended that the EPA finalize the higher end of the 75 to 100 percent

range given the significant increase in the cost of components since the 50% threshold was

established in 1975. Commenter (0195) also stated that the higher end of the percentage range is 

appropriate to account for the spatial constraints existing EGUs are likely to encounter if 

reconstructed.

Commenter (253) supported adjusting the upper capital cost threshold for identifying projects 

considered "reconstruction" from the original 50 percent threshold to a 75 to 100 percent

threshold because the higher threshold recognizes that the cost of components has increased 

significantly since 1975, and because the higher threshold provides a more realistic benchmark 

for identifying what projects actually involve "reconstruction" of an existing plant, rather than 

triggering reconstruction on projects that install NSPS controls on existing boilers.

Response 1.1-3: This final rule does not amend the reconstruction provision included in the 

general provisions.
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Comment 1.1-4: Commenter 0244 stated that EPA must eliminate the source-specific feasibility 

carve-out for reconstructed units. The commenter referenced the "safety valve" that ensures that 

no project will trigger a reconstructed source performance standard if that standard is not 

technologically or economically feasible at that source in question. The commenter stated that 

this provision creates a highly problematic loophole, since it incentivizes any source operator 

wishing to reconstruct a unit to argue that it is not feasible for that particular source to meet the 

standard, regardless of whether or not that is actually the case.

Commenter 0267 believed that the possible exemption for reconstructed units is too vague and 

would likely provide little relief to those who reconstruct. The commenter believed that this rule 

will encourage plants to remain inefficient in order to avoid the costly regulations of 111(d).

Response 1.1-4: This final rule does not amend the reconstruction provision included in the 

general provisions.

Comment 1.1-5: Commenter (0208) stated that simple cycle units that are re-built as combined 

cycle units should not trigger NSPS because there will be no increase in the hourly emission rate 

or CO2.

Response 1.1-5: Applicability determinations are made on a case-by-case basis. The EPA agrees 

that adding heat recovery steam generator without duct burners would not increase the hourly 

emission rate so would not be a modification for NSPS purposes. Depending on the overall costs 

of the project, it may trigger the reconstruction provisions. The EPA notes that modifications for 

New Source Review purposes are determined separately from NSPS modifications.

Comment 1.1-6: Commenter 0195 stated that EPA should establish separate standards of 

performance for EGUs based on whether the unit is modified or reconstructed, the type of 

facility involved, and the heat input of the unit. The commenter stated that subcategorization 

based on relevant factors is authorized by the CAA and is appropriate in this case due to the 

differences in CO2 emissions achievable by utility boilers and IGCC units versus gas-fired 

stationary combustion turbines. Additionally, the commenter urged EPA to further refine the 

subcategories for modified and reconstructed EGUs to differentiate between supercritical and 

subcritical steam cycles as well as types of coal used.

The commenter stated that it is technically impossible within economic limitations to modify a 

subcritical unit to meet these new unit standards short of tearing down the bulk of the plant and 

rebuilding a supercritical boiler. The commenter strongly urged that the alternative standard of a 

plant's best performance in recent history less 2% CO2 be the applicable standard. The 

commenter suggested that performance would be based on the five most recent years of 

operational history.

Response 1.1-6: The commenter is mistaken that the subcritical boiler must use supercritical 

steam conditions. The BSER is used to identify an appropriate emission rate. Units are free to 

use whatever technology they choose to comply with the emission standard. The EPA notes that 

the standard for modified units contains an “or” and the reconstruction standard serves as the 

floor. Units with historical emission rates greater than this are not required to comply with the 

standard for reconstructed units.
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Comment 1.1-7: Commenter 0289 stated that Lignite-fired power plants are technologically 

and operationally distinct from traditional coal-fired power plants, and even more distinct from 

IGCC units, and include different design elements that warrant and require a separate 

subcategory within the overarching coal category. The commenter stated that the physical and 

chemical composition of lignite also typically requires larger, more energy intensive control 

technologies than other coal-fired units. The commenter also stated that these plants are almost 

exclusively located near or at coal mines and are used to supply electricity to these mines. The 

commenter stated because of this, EPA has traditionally created a subcategory for lignite coal. 

The commenter cited the MATS ruling, in which the EPA had a separate subcategory for Lignite 

coal.

Response 1.1-7: The EPA has concluded that the emission standards in this final rule are 

achievable for lignite-fired units and that subcategorization is unnecessary. 

Comment 1.1-8: Commenter 0289, 0179 stated that the rule must create a separate subcategory 

for IGCC EGUs for both modified and reconstructed EGUs. The commenter stated that 

traditional coal-fired power plants are in a completely different class and are of an entirely 

different type than IGCC units. The commenter stated differences in generation technologies also 

result in fundamentally different emissions profiles, including differences in the rate of CO2

emissions. The commenter cited the MATS rules and stated that IGCCs should have their own 

subcategory for the same reasoning as in that rule.

Response 1.1-8: The EPA has concluded that subcategorization of IGCC units is not appropriate 

in this final rule. 

1.2 APPLICABILITY CRITERIA

Comment 1.2-1: In response to the EPA's request for comments on the two versions of the 

proposed applicability criteria, commenters (0215, 0247, 0275) expressed a preference for the 

"Proposed Applicability" version, rather than the "Broad Applicability" version because the 

"Proposed Applicability" version includes several practical exclusions that are not included in 

the "Broad Applicability" version, and the "Broad Applicability" version substantially broadens 

the source category. Commenter (0247) stated that there is no justification for broadening the 

applicability of subparts Da and KKKK because this aspect of the proposal ignores 35 years of 

EPA determinations about the appropriate scope of regulation of EGUs, and it is contrary to 

many other statements by EPA that the GHG NSPS would not expand the coverage of the 

existing NSPS. Commenter (0247) stated that the proposal for modified and reconstructed 

sources did not explain or justify the broad applicability alternative in the preamble, and the 

commenter stated that the proposal's generalized indication that portions of the applicability 

provisions in the preceding proposal for new sources may not apply to modified and 

reconstructed facilities did not constitute the statement of basis and purpose required by the 

Clean Air Act. Commenter (0247) stated that it was inappropriate for the Agency to consider 

altering the section 111(b) applicability provisions so that more sources would be subject to 

standards under section 111(d) because Congress imposed section 111(d) requirements so that 

the information on control technologies developed under 111(b) could be used by states to assure 

reasonable controls are applied to existing sources, and the commenter stated that the broad 

applicability approach turns the 111(b)-to-111(d) process on its head. Commenter 0215 stated 
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that instead of defining the source categories to exclude these units that EPA previously 

proposed to find were not appropriate for regulation, under the Broad Applicability Text, the 

Agency would consider many of these previously excluded sources to technically be "subject to" 

a standard of performance that simply specifies "no emission standard." See, e.g., Broad 

Applicability Text, Subpart TTTT, Table 1. Although these units would not be required to 

comply with a numerical emission limit, they would be subject to monitoring, reporting, and 

recordkeeping requirements under the applicable NSPS. 79 Fed. Reg. at 1461 (discussing broad 

applicability approach in context of January 2014 proposal).

Commenter 0215 stated that at the outset, it is unclear why EPA has included the Broad 

Applicability Text in the docket and how it relates to the proposed NSPS for modified and 

reconstructed EGUs. The commenter stated that EPA does not address the Broad Applicability 

Text or its radically different approach to defining the regulated source category anywhere in the 

preamble to the Proposed Standards. The commenter noted this approach is discussed in the 

preamble to the January 2014 proposal, but that proposal explicitly did not address modified or 

reconstructed sources. See, e.g., 79 Fed. Reg. at 1446. The commenter stated that there is no 

indication in the record that EPA intends to adopt the Broad Applicability Text approach, or that 

it is even considering this approach, other than the mere presence of that document in the docket. 

Accordingly, the commenter assumed that EPA is not proposing to adopt the Broad Applicability 

Text in this rulemaking. The commenter supported this decision. The commenter believed that if 

EPA wishes to pursue this approach to defining the source category, it must publish a 

supplemental proposal explicitly stating its intent to do so and clearly explaining its legal and 

technical justification for that approach. The commenter stated the Agency has not done so here.

Commenter 0215 also stated that the approach set forth in the Broad Applicability Text is 

unlawful because a rule that states that a source is subject to "no emission standard" is not 

a "standard of performance." The commenter noted that Section 111(b) directs EPA to establish 

"[f]ederal standards of performance for new sources within" a listed source category. See CAA 

section 111(b)(1)(B). Under the Act, a "standard of performance" is defined as a "requirement of 

continuous emission reduction." Id. section 302(1).

The commenter stated that even if EPA could list new, modified, or reconstructed sources in a 

source category and subject them to "no emission standard" solely as a predicate for regulating 

existing sources in the category, it would not be appropriate to do so for the sources at issue here. 

Under both the Proposed Applicability Text and the Broad Applicability Text, the commenter 

stated that EPA has clearly determined that it would be inappropriate to limit CO2 emissions 

from new, modified, and reconstructed sources that do not meet the proposal's various 

applicability criteria. The commenter stated existing EGUs that do not meet these criteria should 

be excluded from regulation under section 111(d) for the same reasons that EPA believes the 

corresponding new, modified, and reconstructed sources should not be subject to emission limits 

under section 111(b).

Commenters (0176, 0192) opposed the applicability option referred to as "broad applicability" in 

the June 2014 memorandum in the docket with the subject "Amended Regulatory Text (Broad 

Applicability)."
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Commenter 0280 stated that the Broad Applicability Memo is problematic because it would 

change the provisions for all affected or designated units by eliminating the electricity sales and 

fossil fuel use criteria. The commenter felt that the changes in the memorandum are both 

unnecessary and have the potential to complicate the development of future standards under 

CAA section 111.

Response 1.2-1: See section IV.A.1 of the NSPS preamble for discussion of the broad 

applicability criteria for new, modified and reconstructed sources (steam generating units). See 

sections VIII.D and IX.A.3 of the NSPS preamble for discussion of the broad applicability 

criteria for new, modified and reconstructed sources (combustion turbines).

Comment 1.2-2: Commenter (0168) supported the proposed applicability threshold for modified 

and reconstructed sources that limits applicability to boilers and IGCC systems capable of 

combusting more than 250 MMBtu/h heat input of fossil fuel because this is identical 

to applicability threshold in the current NSPS standards.

Commenter 0242, a state air permitting authority, expressed concerns about including 25 MW 

units in the proposed rules under 111(b) because of associated problems under the subsequent 

111(d) rule when setting state goals. Commenter (0242) disagreed with the Agency's stipulation 

that 25 MW net sales and 219,000 MW-h sales are functionally equivalent because this 

stipulation implies that the small unit will run continuously at full capacity year-round; the 

commenter believed that this basis for equivalence is not technically sound.

Response 1.2-2: The 250 MMBtu/h base load rating threshold has been maintained in the final 

rule. As stated in the preamble to the proposed rule, the 25 MW applicability criteria has been 

interpreted by the EPA as equivalent to 219,000 MWh. The EPA notes that the 219,000 MWh

applicability criteria has been eliminated for non-CHP combustion turbines.

Comment 1.2-3: Commenters 0143, 0149, 0150, 0151, 0152, 0153, 0157, 0161, 0171, 0176, 

0178, 0187, 0191, 0192, 0193, 0195, 0199, 0201, 0203, 0208, 0211, 0214, 0224, 0229, 0235, 

0238, 0239, 0243, 0245, 0250, 0252, 0253, 0254, 0255, 0257, 0260, 0267, 0268, 0275, 0276, 

0278, 0284 stated that simple cycle turbines should be exempt from the proposed standards 

because it is not technologically feasible for simple cycle units to achieve efficiencies equivalent 

to combined cycle units and that the proposed BSER for new, modified, and reconstructed gas 

turbines is based on the operation of NGCC not simple cycle technology. These commenters

stated that NGCC units cannot provide the unique, quick-response capabilities of simple cycle 

units that system operators rely on to manage hourly changes in demand during highly volatile, 

intra-day or minute-to-minute operating scenarios routinely encountered at energy control 

centers. Commenter (0149) stated that the energy supply protocols that ensure grid stability 

require that units held in the ready-mode as "spinning and non-spinning reserves" must be 

available within 10 minutes of dispatch and stated that NGCC units cannot satisfy this

requirement. Commenters (0149, 0257) stated that combined cycle units can take from one to 

twelve hours from startup to full load (depending on the temperature of the HRSG at the 

beginning of the startup sequence); commenter (0245) stated that simple cycle units can startup 

and achieve full load in 12 minutes. These commenters described a broad range of system 

operating scenarios that currently rely on the unique capabilities of simple cycle units that 

included quick-response capabilities for managing forecasting errors, integration of renewables, 
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unanticipated loss of generation, unanticipated loss of load, localized emergency conditions, 

and transmission line constraints. Commenter (0257) discussed scenarios requiring longer-term 

use of simple cycle turbines at high capacity factors in the context of system-wide planning; 

commenter (0257) stated that meeting increasing demand usually requires a combination of new 

generation and new transmission; simple cycle turbines can be utilized during these lengthy, 

interim, permitting, and construction periods to serve intermediate and base loads until long-term 

generating capacity or transmission lines are completed. Commenter (0267) stated that the 

market for electricity generating capacity reflects the different capabilities of simple cycle units 

and combined cycle units because NGCC units typically bid for generation needed the following 

day, while simple cycle units can bid for generation on the same day, and simple cycle units also 

have greater flexibility for rapid starts, stops, and grid fluctuations on a smaller scale than NGCC 

units can provide. Commenters (0161, 0187), EGU operators in regions with rapidly expanding 

renewable generating capacity, stated that the changing landscape of electricity generation 

(brought about in large part by stricter environmental regulations) requires that operators 

increase utilization of simple-cycle units to ensure reliability especially during peak seasonal 

demand periods. These commenters stated that as more renewables are added to the grid, simplecycle units must be available to system operators to enable flexible operations and that simplecycle units must be permitted with sufficient annual capacity factors to respond to the 

unpredictable, intermittent nature of renewable generation which requires numerous starts and 

the capacity to operate for many hours in low-load conditions. Commenter (0161) stated that as 

simple cycle turbines add to their historic role serving periods of peak demand and are 

increasingly dispatched to balance variable renewable assets, the concept of a limited "peaking 

season" may not be meaningful and the proposed 33 percent threshold will not be adequate to 

distinguish base-load generating facilities from simple cycle combustion turbines. These 

commenters believed that these differences in operating capabilities and associated functions for 

reliable operation of the grid provide the EPA with a sound basis for using 111(b)(2) authority to 

subcategorize simple cycle turbines and to exclude simple cycle units from its proposed 

standards for new and modified and reconstructed units.

Commenter 0242 noted the critical nature of simple cycle units for reliably integrating renewable 

assets, and the commenter expressed concerns about the numerous proposed changes in 

applicability criteria for low capacity factor combustion turbines and expressed concerns 

about the predictive accuracy of the IPM model for assessing associated reliability and power 

cost impacts of the numerous proposed changes.

Commenter 0193, 0153, 0176 stated that EPA's historical analysis fails to consider the rapid 

growth of renewable energy and the corresponding impact on simple cycle demand. The 

commenters stated that recent and future projected renewable capacity increases have and 

will create a higher demand for simple cycle turbines. The commenter stated that including these 

turbines under the proposed standard will incentivize the industry to use small, less efficient 

reciprocating engines, which will lead to higher emissions. Commenter 0176 stated that NGSC 

are generally used to meet peak demand, and that they use these units to support their growing 

wind-powered capacity.

Commenter 0176 stated that wind power is very unreliable as an energy source. The commenter 

has experienced grid reliability issues after adding significant wind capacity to their energy mix. 

The commenter recommended that alternative sources of reliable energy be pursued to prevent 
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these issues in the future. However, the commenter stated that NGCC units do not fit this 

purpose well, because they cannot startup and shutdown quickly. The commenter recommended 

the use of simple cycle turbines for this purpose.

Commenters 0192, 0211 stated that providing simple cycle units with a complete exemption 

from NSPS is consistent with longstanding energy delivery standards requiring the most 

economical usage of generating assets.

Commenter 0149 stated that EPA should provide a blanket exemption for simple cycle 

combustion turbines (CT) from this rule as well as the new unit NSPS because these CT units 

serve important reliability functions that may cause them to temporarily exceed the proposed 

rules' standards. The commenter stated that these units lack the higher efficiency of NGCC units, 

and the environmental controls that would allow them to meet the proposed standards.

Commenter 0260 stated that simple cycle units should be exempted from the rule. If not, the 

commenter stated that EPA should adopt the highest standards within the ranges under 

consideration.

Commenter 0215 stated that EPA should explicitly exclude simple cycle combustion turbines 

because simple cycle turbines cannot achieved the proposed standards.

Commenters 0149, 0245, 0257 stated that simple cycle units should be exempt because 

the diverse roles of simple cycle units cause the range of emissions rates from these units to vary 

greatly, and the commenters believe it would be difficult for EPA to determine a standard 

achievable across all simple cycle units.

Commenter 0171 urged the EPA to explicitly exclude simple cycle turbines and peaking units 

from the performance standards because of the low capacity factors associated with these units 

that are almost exclusively used to meet limited-duration peak demand or to serve other shortterm emergency and "black-start" dispatch requirements.

Commenter 0193, a combustion turbine technology vender, appreciated the EPA's consideration 

of multiple options for simple cycle combustion turbines and provided comments on each of the 

applicability options relevant to simple cycle turbines; the commenter's first preference 

was complete exclusion of simple cycle units because the commenter believed this option has the 

strongest statutory support and is consistent with the current trend of expanding use of simple 

cycle units for supporting renewables and grid reliability. Commenter (0193) stated that the 

BSER determination for combustion turbines is based on combined cycle technology, not simple 

cycle technology, and the commenter explained that combined cycle technologies 

cannot perform all the same duty cycles currently required of simple cycle units. 

Commenter (0149) speculated that the most important assumption in a prospective analysis of 

the impacts of RPS on simple cycle operations may relate to the potential impacts of EPA's final 

GHG standards for new and existing natural gas-based units because these standards will be 

significant factors influencing which flexible gas-based units are used to support renewables 

generation. Commenter 0149 explained that if states choose to increase utilization of existing 

NGCC units to comply with the state-specific emission rate goals proposed in the 111(d) 
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guidelines, it is likely that simple-cycle CTs (both new and existing) would be needed to 

facilitate renewables integration; conversely, if EPA's final standards for new units under section 

111(b) place significant operating limits on simple-cycle CTs, then existing CTs and existing 

NGCCs could play a larger role in renewables integration. Commenter (0149) stated that 

renewables are an intermittent resource and that the only resources that can be reliably 

dispatched quickly enough to compensate for significant swings are simple-cycle CTs and hydro. 

Commenter (0149) concluded that if EPA's goal is to foster the development of renewable 

energy, imposing strict limits on the main backup generating source may be counterproductive.

Commenter 0149 stated that simple cycle CTs should not be subject to section 111(b) standards 

that do not recognize the range of reliability and renewables integration services these units 

provide to the grid.

Commenter (0149) stated that it is unlikely that any stakeholder would have credible, reliable 

data on the extent to which simple-cycle CTs will be used to support renewable generation in the 

future because any such analysis would be dependent on numerous state-specific assumptions

about RPS standards and the future demand for electricity, future wholesale electric prices and 

the costs of new simple-cycle CTs, among others.

Commenter 0181 stated that regulating simple cycle turbines under 111(b) will be imported for 

implementation of section 111(d) guidelines for existing EGUs. The commenter stated that 

including all simple cycle turbines in federal regulatory programs may reduce administrative and 

regulatory burdens in implementing federal rules through existing state programs.

Commenter (0181) stated that retired coal-fired generation will be replaced by natural gasfired generators and diesel-fired reciprocating internal combustion engines. Commenter (0181) 

believed that these new types of sources and all other EGUs should be subject to CO2 emission 

limits to help ensure that units participate on a level playing field in energy and capacity markets. 

Commenter (0282) pointed out that the applicability provisions in the proposal are inadequate 

because the proposed provisions include loopholes and exemptions that will leave many

significant GHG sources in the power sector entirely uncontrolled, and the commenter requested 

that the final rule eliminate the proposed exemptions. Commenter (0282) stated that changes to 

applicability are necessary because only a few decades remain to achieve sharp greenhouse 

reductions to avoid climate catastrophe. 

Commenter 0213 stated that the EPA should not exclude modified or reconstructed peaking CTs 

or CCGTs from regulation simply because these units operate less efficiently than base load or 

load-following EGUs. The commenter believed that the final rule should include a three-tiered 

set of performance standards that cover peaking, load-following, and base load units. 

Commenter (0181) stated that excluding some simple cycle turbines may discourage investment 

in cleaner, more efficient capacity such as new natural gas combined cycle combustion turbines 

with cycling capability or more efficient peaking units. Commenter (0181) stated that even if 

some simple cycle combustion turbines cannot comply with the combined-cycle-based standard, 

these simple cycle units should not be excluded; instead, the commenter believed section 111 

requires the agency to establish appropriate subcategories and standards that recognize simple 
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cycle often operate under conditions that do not permit maximum efficiency. Commenter (0181) 

referenced PSD permit limitations for CO2 emissions from simple cycle turbines to support the 

position that simple cycle units are capable of meeting a numerical CO2 emission standard based 

on modern, efficient, simple-cycle, combustion turbine technology: at the Pio Pico Energy 

Center in California, a natural gas-fired simple cycle peaker power plant, has a PSD permit with 

a GHG limit of 1,328 lb CO2/MWh; the Perryman 6 unit in Maryland has a GHG limit of 1,394 

lb CO2e/MWh (gross) while firing natural gas; the commenter also stated that the State of New 

Your established a limit of 1,450 lb CO2/MWh for new simple cycle turbines. Commenter (0181) 

stated that how often a unit does or does not operate should not drive whether a source is subject 

to a standard, but should be considered when determining the specific numerical limitation that is 

achievable. Commenter (0181) stated that if the Agency is not inclined to set numerical

standards for simple cycle peaking units, the Agency should include these units in the rule by 

imposing work practice standards that require operating a facility and equipment consistent with 

safety and good air pollution control practice including requirements for appropriate monitoring 

and reporting of GHG emissions.

Commenter 0150, 0152, 0176, 0176, 0187, 0192, 0199, 0208, 0245, 0250, 0250, 0253, 0254, 

0278 stated that rebuilding simple cycle turbines as NGCC units would not be "technologically 

and economically feasible" as required by 40 CFR 60.15(b)(2) and stated that a requirement to 

re-build simple cycle units as NGCC units to achieve higher efficiencies would also violate the 

statutory prohibition on requiring "any new or modified source to install and operate any

particular technological system of continuous emission reduction to comply with any new source 

standard of performance."

Commenter 0260 stated that in addition to exempting simple cycle units, the final rule should 

also exempt any other type of unit during periods when the unit is providing peaking power.

Commenter 0253, the board of a municipal public utility, provided comments in response to the 

proposal's request for comments "on a full range of alternatives for low capacity factor stationary 

combustion turbines and/or simple cycle combustion turbines" and "on whether a separate 

standard should be established for load-following (i.e., intermediate capacity factor) NGCC 

EGUs." Commenter (0253) stated that low capacity factor and load-following sources should be 

exempted from applicability when they are not dispatched as base load capacity because

regulations governing the current economic dispatch of electricity generators in existing energy 

markets require that system operators first dispatch the units having higher efficiencies, lower 

marginal costs, and lower CO2 emission rates, than either low capacity or load-following units 

normally provide. Commenter (0253) stated that due to their lower efficiencies, low capacity 

(simple cycle) units generally are dispatched during hours of peak electricity demand (after 

dispatchers have already deployed all available, more-efficient, base load units). Commenter 

(0253) stated that NGCC units operating as load-following EGUs are inherently less efficient 

than NGCC units operating at base load and are likely to be dispatched only as needed to assure

grid reliability. Commenter (0253) stated that since existing economic protocols require system 

operators to dispatch the most efficient units first, exempting the less efficient peaking units and 

load-following units will not likely increase CO2 emissions, and commenter (0253) stated that 

the EPA can assure that CO2 emissions do not increase by providing no exemption to peaking 

units and load-following units during years when either type operates above a base load
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threshold. Commenter (0253) stated that exempting peaking and load-following units during 

periods when they are utilized for their design purpose serves the public interest by avoiding 

increases in electricity costs associated with additional controls or retirement of affected units 

and replacements with new units; either option would involve substantial costs that would 

ultimately be borne by consumers, and regardless of whether these economic impacts will, on 

average, be felt at the national level, adopting either option would adversely affect individual

utility's consumers through possible reliability issues related to retirements, or through higher 

utility rates if controls must be added.

Commenter 0282 stated that the final rule must not include any arbitrary and irrational 

exemptions that keep GHG emissions unregulated at many power plants. The commenter 

opposed exemption of any projects under development because the commenter believed such 

exemptions are inconsistent with the intent of the Clean Air Act. The commenter also opposed 

the proposed exemptions for simple cycle turbines and low capacity factor units because the 

commenter understood that utilization of these units is projected to increase, and the commenter 

incorporated related comments previously submitted for the new source proposal.

Commenter 0282 opposed retrospective applicability criteria (such as the proposal to base 

applicability on actual power sales to the grid over a three-year period) because the commenter 

believed these applicability provisions are likely to leave operators, regulators and citizens 

unable to determine whether the GHG standards apply until well after the three-year period has 

expired. 

Commenter 0282 believed that the proposed exemptions under section 111(b) will allow many 

smaller units to remain unregulated under section 111(d) because the applicability criteria 

established for section 111(b) standards must also be used as the applicability criteria under

section 111(d) proceedings, and the commenter urged the EPA to eliminate or minimize

proposed exemptions for new, modified, and reconstructed sources under section 111(b) 

proceedings.

Commenter 0181 opposed the proposed exclusions for combustion turbines related to their 

purpose of construction, their actual net generation, and their usage of natural gas because the 

commenter believed this applicability criteria excludes virtually all simple cycle combustion 

turbines; the commenter believed the proposed rule should apply to all fossil fuel-fired EGUs 

that supply electricity to the grid regardless of whether they are simple or combined cycle units, 

and regardless of the fossil fuel they burn. Commenter (0181) supported the applicability 

provisions in the proposed rule that subject low capacity factor boilers and IGCC units to GHG 

emissions standards; the commenter interpreted these applicability provisions as applying 

to small EGUs. 

Commenter 0181 stated that the EPA provided little explanation for exempting simple cycle 

turbines and small combined cycle combustion turbines from the CO2 emission standards and the 

commenter believed that the EPA failed to set forth a technical justification for why "peakers" 

should not be subject to an appropriate CO2 emissions limitation; the commenter supported 

requiring simple cycle combustion turbines to meet a standard based on combined cycle

technology and cited an EPA analysis from 2006 that indicated simple cycle turbines can achieve 

an emission rate of 825 lb CO2/MWh.
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Response 1.2-3: Based on practical implementation concerns (e.g., not having units come in and 

out of applicability based on actual operating parameters) and interactions with the 111(d) 

applicability criteria, which include all NGCC units, the final applicability criteria in this final 

rule include combustion turbines regardless of percentage electric sales (e.g., simple cycle units) 

and natural gas use (e.g., multi-fuel-fired units). In regards to combustion turbines that burn 100 

percent oil because they are not connected to a natural gas pipeline, we expect few new turbines 

of this type to be built. Any new oil-fired combustion turbines that are built will likely be located 

in a non-continental area that does not have access to natural gas supplies. As a result, we are 

finalizing an exclusion for these units and deferring applicability at this time because (1) few 

new units are expected, (2) we do not have continuous emissions data to establish a meaningful

output-based standard, and (3) the exclusion of units not connected to a natural gas pipeline will 

have a minor impact on 111(d) goals. For non-base load units, which include simple cycle 

turbines, we are finalizing the sliding-scale subcategorization approach and an input-based 

standard that will provide adequate flexibility to support the growth of new intermittent 

renewable generation. See Sections IX.A and IX.B of the preamble for a discussion of the broad 

applicability approach and final subcategories for combustion turbines.

Comment 1.2-4: Commenter 0197 stated that the electric sales applicability test should be based 

on a three-year rolling average for all sources.

Response 1.2-4: The final applicability criteria are based on operating permit conditions and not 

on actual operating parameters. This approach will prevent units from moving in and out of 

applicability. Instead, actual operating parameters (i.e., percentage electric sales and fuel use) 

will be used to distinguish between three combustion turbine subcategories. See Sections IX.A 

and B of the preamble for a more detailed discussion, including related issues, such as averaging 

periods.

Comment 1.2-5: Commenter 0213 stated that the agency should ensure that fast-start CCGT are 

covered under the proposed rule by replacing references to a facility's "potential electric output" 

with "intended electric output."

Response 1.2-5: The final applicability criteria in this final rule do not distinguish between the 

design characteristics of stationary combustion turbines. Instead, the non-base load and base load 

subcategories are determined strictly on the percentage of electric sales. Fast-start NGCC units 

are covered by the final rule, and will be subject to an input-based standard if they are below the 

percentage electric sales threshold or an output-based standard if they are above the threshold. 

Fast-start NGCC units can meet either standard depending on how they are operated. The final 

rule also excludes electricity generated as a result of a system emergency from counting toward 

the percentage electric sales threshold. The EPA has concluded that this exclusion will provide 

adequate assurance that the final requirements will not result in reliability concerns.

Comment 1.2-6: Commenters 0157, 0197, 0267 opposed the proposed revisions to applicability 

criteria that would include electricity supplied by small sources and other sources that would not 

otherwise be subject to the standard when those otherwise exempt sources supply electricity to 

offset the auxiliary loads of affected EGUs. Commenter (0157) stated that the proposed

treatment of these otherwise-exempt, auxiliary-load generators at power plants was inconsistent 

with exemption of similar generating units at non-power plants that produce electricity for use 
1-15

on-site and not for sale, and commenter (0157) stated that, in all cases, if a unit is not generating 

electricity for sale, then it should not be covered. Commenter (0197) expressed concerns that the 

proposed treatment of these otherwise-exempt, auxiliary-load generators at power plants would 

have significant impacts on the construction of new sources, and the commenter stated that the 

test should be consistent for all regulated sources (both sources located at power plants and 

sources located at industrial sites.)

Response 1.2-6: The 25 MW-n electric sales capability is included in the general applicability 

criteria. An auxiliary unit specifically for providing auxiliary load that is incapable of selling 

power to the grid would not be covered by this final rule.

1.3 STEAM GENERATING UNIT

Comment 1.3-1: Commenter (0145, 0267) stated that applicability for utility boilers and IGCC 

units under the proposed rule should be based on actual operating and utilization data.

Commenter (0145, 0267) opposed elimination of the actual usage criteria for modified and 

reconstructed boilers and IGCC units, because the commenter believed that these applicability 

criteria for modified and reconstructed units are inconsistent with the proposed requirements for 

new boilers and new and modified natural gas turbines. Commenters (0145, 0267) stated that the 

EPA had not provided supporting documentation that demonstrates that facilities operating at 

very low capacity factors can meet the proposed emission rates; nor has EPA provided a rational 

basis for using different, and more stringent, applicability criteria to modified and reconstructed 

utility boilers and IGCC units than the criteria for both gas turbines and new boilers and IGCC 

units. Commenter (0145) recommended that applicability criteria in the final rule should include

both intended and actual usage.

Response 1.3-1: The applicability criteria in this final rule are consistent, with respect to the 

intent of the unit, with the applicability criteria in the coal-fired EGU criteria pollutant NSPS, 

subpart Da. Coal-fired EGUs have the option of co-firing natural gas during periods of low loads 

to comply with the required emission standard.

Comment 1.3-2: Commenter 0206, 0287 stated that EPA's proposal sets emission limits that 

depend on when in time the modification occurs and unit-specific emissions. The commenter 

stated that both of these types of limits are contrary to 111(b) requirements, and should not be 

brought into the final ruling.

Response 1.3-2: The EPA disagrees that this approach is contrary to the 111(b) requirements. 

See the preamble of this final rule for further response.

1.4 STATIONARY COMBUSTION TURBINE

1.4.1 Potential Electric Output

Comment 1.4-1: Commenters (0176, 0192) opposed removal of the actual net sales criterion for 

determining applicability of the standard to modified and reconstructed units because modified 

and reconstructed EGUs that are designed to operate at higher capacity factors but which actually 

operate at lower capacity factors would remain subject to the same emission limits even though 
1-16

the lower capacity factor would likely accompany a lower efficiency. Commenter (0176)

disagreed with the EPA's justification (that units designed as base load or intermediate units but 

that operate at relatively low capacity factors can meet the relatively less stringent standard for 

modified and reconstructed units) because the emission standard for modified and reconstructed 

combustion turbines is not less stringent than the emissions standard for new combustion

turbines. Accordingly, commenter (0176) requested that the final rule for modified and

reconstructed units include the "actual operating" applicability requirement. 

Commenter (0192) also opposed the proposal to eliminate the actual sales criteria for modified 

and reconstructed sources and stated that it is inappropriate for EPA to expand the applicability 

of the rules for reconstructed and modified sources (and potentially the rule for existing sources) 

to include sources to which a standard of performance under section 111 would not apply if the 

reconstructed, modified, or existing source were a new source.

Commenter 0211 opposed removal of the sales criterion (219,000 MWh) for stationary

combustion turbines because this criterion helps ensure that NSPS will focus on the largest and 

most utilized stationary combustion turbines, and it provides a reasonable level of sales to 

support the imposition of regulatory requirements. Commenter (0211) also stated that this 

criterion should be retained because it ensures that industrial combined heat and power (CHP) 

are not subject to the standards, and the commenter believed that these highly efficient

operations should not be encumbered by the regulatory burdens of the proposed standard.

Commenter (193) opposed the proposed elimination of the NSPS applicability criteria (to 

actually sell one-third of potential electric output and 219,000 MWh on an annual basis) for 

modified and reconstructed units because these sales criteria were intended to exempt low 

capacity factor facilities that would have difficulties meeting the NSPS standards proposed in 

January 2014, and the commenter did not believe that the proposal for modified and

reconstructed units included sufficient support for the Agency's assertion that these units are 

capable of achieving the less stringent standards proposed for modified and reconstructed units 

(as compared to the proposed standards for new sources).

Commenter (0213) opposed inclusion of a sales criterion for applicability because many base 

load and load-following EGUs operate at capacity factors below the proposed threshold; the 

commenter also opposed the sales criterion because some plants will fall in and out of

applicability from year to year, and the commenter believed these year-by-year changes will 

create significant enforcement and permitting problems. Commenter (0213) stated that the 

agency should apply performance standards to any EGU that supplies or was constructed for the 

purpose of supplying any amount of electricity for sale to the grid.

Response 1.4-1: The applicability criteria in this final rule are consistent, with respect to the 

intent of the unit, with the applicability criteria in the coal-fired EGU criteria pollutant NSPS, 

subpart Da. Coal-fired EGUs have the option of co-firing natural gas during periods of low loads 

to comply with the required emission standard.

Comment 1.4-2: Commenters 0178, 0260 stated EPA should not include the "design net 

efficiency" approach because it is difficult to determine the "original design" of existing units. 

The commenter stated the on-paper engineered value may vary greatly from the actual "installed 

design" due to numerous factors, such as construction materials and ambient conditions.
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Commenter 0151 stated that a change in reporting under Part 75 to include net generation would 

result in significant incremental costs for monitoring. The commenter also stated that adopting 

net generation for reporting under Part 75 could result in compliance costs in the millions of 

dollars to replace or upgrade their existing DAHS.

Commenter 0197 stated that the final rule should not include separate thresholds for net electric 

sales, because a net electric sales threshold may make it easier for some sources to avoid

applicability. 

Commenter 0193 acknowledged that the proposed changes to one of the core applicability 

definitions (the definition of net-electric sales) may be warranted based on the EPA's concerns 

that small EGUs co-located with larger EGUs may claim non-applicability in the absence of the 

proposed amendment to the definition; however, the commenter opposed this proposed revision 

because the commenter believed that the EPA failed to provide the public with sufficient 

information to determine the specific sources that will be impacted by this proposed amendment.

Commenter 0213 agreed with EPA that an amendment to include net electric output into the 

definition of Potential Electric Output will help close a problematic loophole, and urged the 

agency to include it in both the final new source rule and the final modified/reconstructed rule.

Commenter (0242) supported inclusion of the net sales criterion in the proposal for modified and 

reconstructed sources because the commenter believed it will avoid uncertainties related to 

smaller units.

Response 1.4-2: The final applicability and subcategorization in this final rule is based on net 

electric sale because it is a better indication of intent than gross output. The intent is to focus 

coverage on EGUs and not industrial units. The final emission standard do not require the use of 

net output.

Comment 1.4-3: Commenters 0171, 0187, 0238 provided comments in response to the Agency's 

request related to alternatives for low capacity factor combustion turbines. Commenters (0187, 

0171) recommended exempting all low-capacity factor units from applicability under the 

proposed rule and stated that if the final rule does not exempt these units then the commenter 

supported a separate subcategory for low capacity factor units with an associated higher emission 

limit because low-capacity factor units typically have significantly lower efficiencies.

Commenter (0238) provided a view acknowledging that simple cycle units can be less efficient 

than other technologies encompassed by the rule because of frequent ramping, but that simple 

cycle units play a critical role in making the over-all system more efficient and reliable.

Commenter (0238) stated that the final rule should exempt low capacity factor stationary

combustion turbines and explicitly exclude all simple cycle turbines and peaking units because

of their unique roles in the portfolio of energy generating assets and because the commenter 

believed it is inappropriate and unreasonable to include simple cycle units and other peaking 

technologies in the same source category as base load and intermediate load units.

Commenter 0257 stated that subjecting these units to regulation under section 111(d) is not 

appropriate. The commenter noted that EPA has consistently recognized that these units operate 

only in critical situations and are vital to ensure reliability. For this reason, EPA created a 
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limited-use subcategory in the final MATS rule. The commenter stated that the MATS 

exemption for these units recognizes that these units do not run frequently and that these units 

will be retired instead of retrofit with expensive control technologies because they cannot 

recover these costs through increased operations. For these reasons, it was reasonable and 

appropriate not to subject these units to MATS requirements. The commenter stated that 

similarly, it is reasonable and appropriate to exempt these units from regulation under 111(d).

Commenter 0214 opposed the proposed revisions to the subpart Da applicability criteria for 

modified and reconstructed boilers and IGCCs because these changes potentially expand the 

population of affected sources to include low capacity factor units that serve reliability needs and 

that would not be affected sources if those units were new. The commenter believed that the final 

rule should reinstate the one-third sales and 219,000 MWh sales criteria for modified and 

reconstructed subpart Da sources because it is well established that low capacity factor units 

cannot achieve high efficiencies.

Commenter 0215 stated that EPA should retain the 1/3 sales criterion. The commenter stated that 

given the significant degree to which a unit's heat rate (and thus, its CO2 emission rate) depends 

on the unit's capacity factor, the one-third sales criterion is likely even more necessary in this 

rulemaking than the January 2014 proposal.

Commenter 0149 stated that EPA does not provide any evidence regarding the achievability of 

the proposed standards by low capacity units. Therefore, the commenter believed that the EPA 

must keep the 1/3 sales criteria because otherwise, low capacity oil-fired units will be subject to 

the 111(d) ruling.

Commenter 0193, a manufacturer of combustion turbines, agreed with the Agency's conclusion 

that the capacity factor and sales criteria (as originally proposed in January 2014) would actually 

increase emissions by promoting the use of smaller, less efficient units, and the commenter also 

stated that the proposed applicability criteria also unfairly promote use of reciprocating diesel 

engines, which can have higher CO2 emission rates than natural gas fired affected sources under 

the proposed applicability criteria; the commenter reported sales of 34,000 diesel-engine

powered generators with 32 GW of capacity world-wide. Commenter (0193) stated that

eliminating the 219,000 MWh sales criterion alone would not resolve problems that will arise if 

the final rule applies an emission standard based on combined cycle technology to simple cycle 

units, and the commenter believed that the final rule should not only eliminate the 219,000 MWh 

sales criterion but should also exempt high-efficiency simple cycle turbines because these

revisions are necessary for ongoing use of simple cycle turbines to support renewables and grid 

reliability.

Commenters (0149, 0214, 0225, 0245, 0250) responded to the proposal's request for comments 

on whether the proposed net sales criteria is sufficient to account for the projected increase in 

simple cycle capacity factors attributable to state and local mandates for increased reliance on 

renewable generation.

Commenter (0225), an air quality permitting authority in a state with a 20 percent renewable 

portfolio standard, indicated that the 33 percent capacity factor would not be sufficient for the 

category of generators (i.e., flexible generators) used in California to support renewable 
1-19

generation. Commenter (0225) divided generating assets used in California into three categories 

based on annual capacity factors: baseload (60 to 100 percent capacity factors); flexible (33 to 60 

percent capacity factors); and peaker (below 33 percent capacity factors). Commenter (0225) 

stated that the flexible category encompassed simple cycle operations (either during bypass of 

the HRSG on combined cycle units or on combustion turbines that can only operate in the simple 

cycle mode). Commenter (0225) described flexible generators as an emergent type of generating 

capacity integral to the increasing development of renewable resources in California. Commenter 

(0225) stated that flexible EGUs share three primary characteristics: dispatchability/loadfollowing, fast-starting, and fast-ramping. Commenter (0225) stated that to integrate renewable 

resources, the electricity system must have sufficient dispatchable EGUs that are available to 

respond to varying system needs when called upon. Commenter (0225) stated that since

renewable resources can come on the system or drop from the system very quickly, the

electricity system needs large amounts (proportional to the RPS) of dispatchable EGUs that have 

fast start capability, that can ramp (up or down) very quickly, and that can turn down to lower 

output to maintain grid stability for dynamic demand and supply conditions. Commenter (0225)

stated that EGUs that can come on-line in 10 minutes or less are increasingly needed and

acknowledged that EGUs that operate in this ready-state manner are less thermally efficient, but 

that in combination with the renewable resources that they support, provide system-wide

emissions reductions.

Commenter 0214 supported complete exemption of simple-cycle units with a secondary

recommendation for a sales threshold of at least 40 percent. 

Commenter (0229) supported a minimum sales requirement of 40 percent and an associated 

exemption because the proposed standards for combustion turbines can only be achieved by new 

natural gas combined cycle (NGCC) units, and the exemption for simple-cycle CTs recognizes 

that these units are designed for lower efficiencies to enable quick response to sudden changes in 

load. Commenter (0229) opposed establishing a regulatory linkage between a simple cycle unit's 

efficiency and the exemption threshold and suggested that the final rule increase the threshold to 

40 percent for all simple cycle units.

Commenter (0245), a utility operator that uses simple cycle turbines to follow wind generation, 

supported complete exemption for simple cycle turbines with a secondary recommendation for a 

sales threshold of at least 50 percent. Commenter (0250), a utility operator with significant wind 

generating capacity and expanding solar generating capacity, stated that currently their systemwide emission rate (including renewables) is 668 lb CO2e/MWh, and the commenter stated that 

fast-start simple cycle generators were essential to their ability to achieve this emission rate. 

Commenter (0250) described a recent BACT analysis associated with a simple cycle installation 

necessary to support expanding use of renewables; the commenter stated that the simple cycle 

units were permitted to operate 5000 hours per year.

Commenter (0176) supported complete exemption for simple cycle turbines but also responded 

to the request for comment on the need for a higher capacity threshold; commenter (0176)

recommended increasing the proposed 33 percent threshold to a 50 percent threshold to enable 

simple cycle units to support renewable generation. 
1-20

Commenter (0245), an operator of a regional utility, believed that the proposed sales criteria will 

force certain simple cycle turbine that undergo modifications or reconstruction, to no longer 

operate in simple cycle mode but instead be converted to combined cycle turbines. Commenter 

(0245) also believed that the 33% and 219,000 MWh applicability threshold for simple cycle 

turbines rewards low efficiency, smaller simple cycle units at the expense of larger and higher 

efficiency units. The commenter described a recently installed set of General Electric's newest 

and most efficient gas turbines (two LMS 100 units) with efficiencies that are 10 percent higher 

than other GE simple cycle machines and capable of achieving full load in 10 to 12 minutes,

dramatically reducing startup emissions. The commenter stated that the LMS 100 has an

emission rate of 1007 lb CO2/MWh and that the proposed sales criteria would limit these units to 

approximately 2900 hours per year. The commenter compared the GE LMS 100 to four 25 MW 

turbines with conventional efficiencies and emitting a total of 1266 pounds of CO2 per megawatt 

hour. The commenter believed that the proposed rule would allow the less efficient 25 MW units 

to operate 8760 hours per year, and the commenter believed the proposed rule will restrict the

utility's ability to use the most efficient simple cycle gas turbine to support expansion of

renewable generation in their service territory. Commenter (0245) believed that exemption of 

high efficiency simple cycle turbines will ensure grid reliability and accommodate the increased 

use of renewable generation, and the commenter believed that the proposed standards fail to 

recognize that using simple cycles to follow renewables results in system-wide GHG reductions, 

and the commenter recommended that the EPA consider increasing the sales threshold to at least 

50 percent.

Commenter (0245) stated that the EPA did not address situations where a modified or

reconstructed simple cycle turbine has reached (but not exceeded) the proposed sales criteria, and 

the commenter believed continued operation of the asset would either require the unit to be

converted to combined cycle and no longer fulfill the need for which it was constructed or

require the unit to sit idle for several months to reduce the three year average capacity factor and 

to reduce utilization of the unit in the future and requiring customers to pay for an additional unit 

to meet system demands for fast-start generating capacity.

Commenter (0193) also provided a subordinate, second preference: complete exclusion for

simple cycle units that operate with a three-year average capacity factor of 60 percent or less; the 

commenter stated that this was the second best approach because simple cycle units operating 

above this threshold are operating as base-load generating units, and the commenter believed that 

the Agency has greater statutory support for applying the BSER determination for NGCC units 

to base-load simple cycle turbines.

Commenter (0193) also provided a tertiary subordinate option: a sliding efficiency-based

capacity factor exclusion based on the unit's measured efficiency multiplied by 1.5 so that a unit 

that is 30% efficient (HHV) would be restricted to a 45% capacity factor, while a 40% efficient 

(HHV) unit would be allowed a 60% capacity factor. The commenter believed that this approach 

would encourage high efficiency power generation and low CO2 emissions.

Commenter 0192, 0211 supported exemption of simple cycle turbines but also provided

comments relevant to other options considered by the EPA in the proposal including the EPA's 

solicitation of comments on use of a "multiplication factor" to the design net efficiency of simple 

cycle combustion turbines; the commenter stated that use of a multiplication factor of 1.1 or
1-21

greater would be directionally helpful for ensuring that the final rule does not compromise grid 

stability by constraining simple cycle capacity factors below the capacity factors that may be 

needed by system operators during future years with increasing reliance on variable renewable 

generating assets. 

Commenter 0197 supported removal of the 219,000 MWh criteria because sources with sales 

below this threshold would have avoided regulation.

Commenter 0225 stated that EPA has sufficient evidence to support a lower emission factor for 

base load EGUs, operating at or above a 60 percent capacity factor, while retaining its proposed 

emission factor for flexible EGUs. The commenter believed that these two subcategories should 

be separate, and that a third subcategory for peaker EGUs that operate below 33 percent capacity 

factor should also be established. The commenter felt that peaker units should not be exempted 

in order to comply with the Clean Air Act.

Commenter (0282) also opposed applicability provisions based on whether an EGU is designed

to supply, or actually supplies more than one-third of its potential output to the grid; the 

commenter believed that all units that actually supply electricity should be subject to the 

proposed standards, and the commenter believed that the EPA must explain why it concludes 

that no BSER exists for EGUs that are exempted from applicability. 

Response 1.4-3: The applicability in this final rule is a modification of the broad applicability 

approach we solicited comment on and does not exempt non-CHP combustion turbines based on 

percentage of electric sales relative to the potential electric output. The EPA completed

significant analysis for this final rule and concluded that the appropriate distinction between nonbase load and base load units is the use of the sliding-scale subcategorization approach. This 

approach provides adequate flexibility for the continued use of simple cycle units while 

simultaneously promoting the installation of more efficient technologies. While the EPA found 

that the one-third electric sales threshold would provide adequate flexibility for simple cycle 

units based on their historical usage, the EPA wanted to be responsive to commenter concerns 

that simple cycle units may be used more in the future to back up intermittent renewables. Under 

the sliding scale, conventional simple cycle turbines will be able to sell between 33 and 40 

percent (depending on the unit) of their potential electric sales before being subject to the base 

load standard, the best high-efficiency simple cycle turbines will be able to sell up to 43 percent 

of their potential electric output, and fast-start NGCC units will be able to sell up to 49 percent of 

their potential electric output. Requests for 50 and even 60 percent electric sales thresholds for 

all units are simply not reasonable. Units selling this much electricity to the grid are serving base 

load demand and should be installing NGCC technology, which is both more cost-effective and 

more efficient at these sales levels.

Comment 1.4-4: Commenters (0192, 0211) also provided an alternative recommendation 

relevant to any future decision by the EPA to include simple cycle turbines in the final rule; the 

commenter proposed that any final rule with applicability criteria for simple cycle turbines

should provide specific exclusions within the applicability criteria for periods of simple cycle 

operations during grid emergencies and during periods when simple cycle units are operated as

"spinning reserves" or for any other ancillary services that do not result in electricity delivered to 

the grid.
1-22

Response 1.4-4: The final rule includes an exemption for electric sales that occur as the result of 

a system emergency from counting towards the percentage electric sales threshold. See Section 

IX.B of the preamble for a discussion of emergency electricity generation.

Comment 1.4-5: Commenter 0197 recommended deletion of the applicability requirements for 

turbines to burn at least 90 percent natural gas because some operators will be able to burn 

eleven percent of another permitted fuel (e.g., No. 2 fuel oil) and avoid applicability.

Commenter 0213 stated that EPA should eliminate 90 percent natural gas minimum threshold for 

stationary combustion turbines and 50 percent syngas threshold for IGCC units. The commenter 

stated that these thresholds do not serve a beneficial purpose and allow units to escape regulation 

by making small adjustments to their fuel input.

Commenter 0213 opposed use of the 10 percent fossil fuel use criteria for stationary combustion 

turbines because the commenter believed the purpose of this criteria is to restrict applicability to 

base load and load-following units, and the commenter opposed this policy. The commenter

believed that applicability should cover all fossil fuel-fired EGUs, including peakers that sell 

any electricity to the grid.

Response 1.4-5: The applicability in this final rule is a modification of the broad applicability 

approach we solicited comment on and does not exempt non-CHP combustion turbines based on 

percentage of electric sales relative to the potential electric output or the amount of natural gas 

burned. IGCC units burning less than 50 percent syngas would comply with the emission 

standard for multi-fuel station combustion turbines.

Comment 1.4-6: Commenter 0213 stated that the proposed applicability provisions should be 

revised to ensure that the individual combustion turbines, heat recovery steam generators, and 

associated steam turbines on combined cycle power blocks are not treated separately for the 

purposes of determining applicability or calculating emissions. Commenter (0213) recommended 

inclusion of all combined cycle components within a single subcategory, and the commenter 

believed that simple cycle turbines should also be included in this subcategory. Commenter 

(0213) stated that applicability and compliance provisions should not distinguish between heat 

input to the combustion turbine versus heat input to the steam generator; similarly the commenter 

recommended that there should be no distinction between electricity generated by the

combustion turbine generator and the steam turbine generator for the purposes of applicability 

and compliance.

Response 1.4-6: Combustion turbine engines and associated HRSG are treated as a single 

affected unit. The base load rating has been amended to include the heat input from duct burners.

Comment 1.4-7: Commenter 0215 stated that the final rule should not apply to an NGCC unit 

when it fires oil or when it bypasses the steam cycle to operate in simple cycle mode.

Commenters 0150, 0151, 0238, 0254, 0260, 0275 stated that many NGCC units have the ability 

to operate in simple-cycle mode (when the system dispatcher requires ramp rates that would heat 

the HRSG more rapidly than specified by the HRSG manufacturer or when steam-cycle

components are undergoing maintenance) and these units cannot comply with a standard based 
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only on combined cycle operations. These commenters stated that it is often necessary for 

combined cycle units to operate in simple cycle mode to quickly respond to energy fluctuations 

from renewable resources or to comply with permit limits for other criteria pollutants. The 

commenters (0150, 0151, 0238, 0254, 0260, 0275) stated that the final applicability criteria 

should indicate that the standard does not apply during periods of simple cycle operations on 

combined cycle units that can also operate in simple cycle mode. Commenters (0150, 0254)

stated that, at a minimum, simple-cycle operations below a 33 percent capacity factor on NGCC 

units should be exempted.

Commenter 0215 stated that NGCC units that would be subject to the modified or reconstructed 

source NSPS have designs that allow the operators to bypass the steam cycle and operate in 

simple cycle mode when necessary. The commenter noted this capability serves an important 

purpose in support of system reliability, as it allows the simple cycle portion of an NGCC unit to 

remain available for backup generation during periods when portions of the steam cycle, such as 

the steam turbine or HRSG, are undergoing maintenance. The commenter urged EPA to exclude 

from applicability simple cycle mode operations.

Commenter (0239) stated that the final rule should exempt simple cycle operations that fall 

below 33 percent capacity factor for any combined cycle units that are capable of operating in 

simple cycle mode.

Response 1.4-7: The EPA disagrees with the commenter that simple cycle operation for a 

NGCC unit should not be counted towards compliance demonstration calculations. The final rule 

does not set separate standards for simple cycle versus combined cycle units. The emission limit 

required for a unit is based on the amount of electricity sold to the grid, derived from a unit’s 

nameplate design efficiency calculated as a percentage of potential electric output. The final base 

load subcategory standard includes sufficient compliance margin to allow flexibility of NGCC 

operation, including running in simple cycle mode. If an NGCC unit operated for significant 

periods in simple cycle mode, it would likely be subject to the natural gas-fired non-base load 

emission standard. The non-base load standard requires the use of clean fuels, and efficiency 

does not factor into compliance with the emission standard.

Comment 1.4-8: Commenter 0149, 0257 stated that a variable standard may make sense in 

theory as a way to address both arguments that NGCC units can achieve emission rates lower 

than the proposed 1,000 lb CO2/MWh standards and concerns that these lower emission rates are 

predicated on these units operating at high capacity factors when in reality they cycle and 

respond to changing load and changing renewable electricity production. However, the 

commenter also stated that EPA has not proposed any actual numerical standards that would 

apply either during the "high annual capacity factor" period or during the "intermediate load" 

period. The commenter stated it is difficult to assess a variable standard without reference to the 

actual standard.

Response 1.4-8: The final non-base load standard is based on the use of clean fuels. This 

standard results in limited compliance burden.
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1.4.2 Large/Small Combustion Turbine Cut-point

Comment 1.4-9: Commenter 0212 stated that EPA should establish a single performance 

standard for all stationary gas turbines, regardless of turbine size or rated heat input. The 

commenter felt that separate standards for small and large turbines undermine the incentive for 

technology innovation and discourage investment in more efficient technologies. The commenter 

stated that by providing greater compliance flexibility to small turbines, the less stringent 

standard would enable the use of smaller, less efficient facilities or multiple lower efficiency 

turbines.

Commenter 0187 stated that they support increasing the size distinction between large and small 

combustion turbines to at least 1,000 MMBtu/h. The commenter also stated that the final rule 

needs to be clear regarding whether the heat input standard is based on the LHV or the HHV of 

the fuel.

Commenter 0192, 0193 stated that EPA should raise the proposed cut-point between "large" and 

"small" gas turbines from 850 MMBtu/h to 1,500 MMBtu/h based on a high heating value. 

Commenter 0250 stated that the EPA made errors in its calculation of the 850 MMBtu/h

standard, mainly that it assumed an efficiency of 44%, which is higher than even the most 

efficient simple cycle turbines. The commenter recommended raising the cut off to 950

MMBtu/h to better reflect the current simple cycle industry. 

Commenter 0250 stated that the only reason EPA gives for using a 850 MMBtu/h cut-off is that 

it was the standard used in subpart KKKK. However, the commenter stated, the proposed rule 

preamble provided no other justification for this distinction. The commenter also stated that 

subpart KKKK does not explain the distinction either, and therefore the EPA should stick with 

the 110 MW cut-off, which at least had some substantial backing.

Response 1.4-9: Based on considering public comments and further evaluation, the EPA has 

determined that size based subcategorization is not appropriate for combustion turbines. See the 

preamble for this final rule for additional rationale.

1.4.3 Oil-fired Combustion Turbines

Comment 1.4-10: Commenter 0150, 0162, 0214, 0215 stated EPA's rules for modified and 

reconstructed NGCC units should expressly exclude modes of operation that are not normal for 

NGCC combustion turbines. The commenter stated that many combustion turbines are permitted 

to fire oil as a back-up fuel for up to 30 days per year, particularly during curtailments when 

natural gas supplies are short. The commenter stated that the EPA has provided no emissions 

data to justify any NSPS for combined cycle combustion turbines when they are firing oil.

Commenter 0149 stated that it is reasonable and appropriate to exempt these units from

regulation under section 111. The commenter stated that from an emission control perspective, 

there is no control technology retrofit that would address CO2 emissions from these units. The 

commenter also stated that efforts to improve these units' heat rates would prove ineffective 

given the limited operations of these units and may result in the closure of these units if the costs 
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of the heat rate improvement projects cannot be recouped through increased operation, which 

generally would be expected to be the case.

Commenter 0152, 0254 stated that EPA has provided no data to justify a limit for NGCC when 

firing oil, and thus these limited periods of operation should be excluded from the rule. The 

commenter also stated that many NGCC units have the ability to operate in simple-cycle mode. 

The commenter stated that at a minimum, simple-cycle operation should be excluded if it falls 

below 33 percent capacity factor. 

Response 1.4-10: Affected combustion turbines burning 10 percent or more non-natural gas 

will be subject to the emission standard in the multi-fuel unit subcategory. This emission 

standard is based on the use of clean fuels, and is readily achievable for combustion turbines 

burning distillate oil.

Comment 1.4-11: Commenter 0244 stated that in its final mod/recon rule, EPA must directly 

address O&G steam EGUs and make clear that the rule is applicable to those units.

Response 1.4-11: The EPA has concluded that the applicability is sufficiently clear that oil and 

gas-fired steam generating units are covered units.

1.5 EXEMPTIONS

Comment 1.5-1: Commenter 0182, 0197 states that a performance standard is not feasible for 

coal refuse CFBs since there is no economically feasible way to capture CO2 through a

conveyance designed and constructed to capture that pollutant. The commenter also stated that 

NESHAPs and work practice standards that have recently been passed do enough to limit 

emissions from coal refuse plants. The commenter recommended that the EPA establish BSER 

for GHGs at modified coal refuse CFBs as a boiler tune-up that must be performed at least every 

24 months. 

Commenter 0182 also recommended that EPA provide relief for Coal Refuse CFB's by

exempting CO2 emissions from the calcination of limestone at these plants, as it is a part of their 

SOx emission controls.

Commenter 0182 stated that the EPA should exempt coal refuse CFB units relative to their CO2

emissions to the extent that these units offset the uncontrolled ground level emissions from 

burning legacy coal refuse stockpiles. 

Commenter 0197 notes that the mining of coal waste not only produces less emissions in the

long term, but also helps to reclaim land that is currently used to store coal waste. 

Response 1.5-1: See section III.E of the NSPS preamble for discussion of use of coal refuse as 

fuel.

Comment 1.5-2: Commenter 0156 requested that the rule be revised to include a limited

exclusion for modified units in transmission constrained areas that are required to operate due to 

electric system reliability constraints but have been designated for retirement. The commenter 
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stated that they are currently unable to shutdown two units due to rulings by the MISO, however 

the units are scheduled for retirement, and therefore it would be pointless for the commenter to 

add new emissions reduction equipment to the plant.

Response 1.5-2: These units would only be subject to the requirements of this final rule if they 

modify or reconstruct. Therefore, the units will continue to be available as existing units.

Comment 1.5-3: Commenter 0164 requested exemptions for their units because of their

geographic location (Central Alaska). The commenter feared that the units cannot be modified in 

a way that would allow them to meet the proposed 111(b) standards for Mod/Recon units. The 

commenter noted that the location of the plant makes natural gas unfeasible and eliminates other 

emission reduction measures available to other plants.

Response 1.5-3: Combustion turbines without access to natural gas would not be subject to the 

requirements in this final rule.

1.6 CHP

Comment 1.6-1: Commenters 0180, 0192, 0196, 0212, 0267 stated that they support the

exemption of combined heat and power units in order to encourage the implementation of this 

technology. Commenters (0180, 0196) stated that such exemptions make sense because CHP 

units are typically customized to suit the process and power needs of each host facility, and as 

EPA has noted, the use of third party-owned CHPs for adjacent industrial facilities only creates 

further complications. Commenter 0192 stated that CHP units are fundamentally different from 

the fossil fuel-fired EGUs that are the subject of this rulemaking because their primary purpose is 

not to provide electricity to the grid. 

Commenter 0196 expressed concerns that inclusion of CHP facilities within the proposed 

applicability provisions will reverse the EPA's longstanding effort to encourage CHP projects 

due to their environmental benefits and associated reductions in CO2 emissions. Accordingly, 

commenter (0196) encouraged the EPA to exclude CHP plants from applicability under the 

proposed rule.

Commenters 0211, 0242 stated that if the final rule eliminates the sales criterion for combustion 

turbines, then the commenters would support a specific exemption for industrial CHP facilities. 

Commenter 0193 stated that EPA should exclude all CHP units that achieve 65 percent

efficiency from EPA's proposed standards for new and modified and reconstructed units. The 

commenter stated that a clear exclusion for CHP units that achieve a 65 percent efficiency would 

significantly accelerate the development and sale of CHP units in the construction of new units 

and in the modification of existing units. The commenter stated this in turn would result in 

significant energy savings and reduced GHG emissions.

Commenter 0267 stated that an exemption for highly efficient CHPs that achieve an overall 

efficiency level of 60 percent or more would be directionally helpful in both the new and 

modified/reconstruct rules.
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Commenter 0267 stated that the EPA should establish applicability criteria to exclude stationary 

combustion turbines whose primary purpose is to provide thermal (100% consideration) and 

electric energy to an industrial source. The commenter believed that the definition of stationary 

combustion turbine could be modified to reflect the primary purpose and read as follows: 

"A stationary combustion turbine that has a base load rating greater than 73 MW thermal (250 

MMBtu/h), was constructed for the purpose of supplying, and supplies, more than 50% of total 

energy output, including MW electricity and MW thermal, to a utility distribution system on a 3-

year rolling average basis, combusts fossil fuel for more than 10.0 percent of the heat input 

during a 3-year rolling average basis, and combusts over 90% natural gas on a heat input basis on 

a 3-year rolling average basis."

Commenter 0193 stated that for CHP units, the percent sales threshold should be set on the basis 

of net system efficiency (including useful thermal output) rather than the rated efficiency of just 

the combustion turbine. The commenter noted that EPA requested comment on changing the 

one-third potential electric output sales criteria to the "design net efficiency times the potential 

electric output" for simple cycle combustion turbines. The commenter stated that as EPA notes, 

this would have the effect of allowing the most efficient larger simple cycle combustion turbines 

to sell a higher percentage of their electric output before an emission standard would apply. The 

commenter endorsed this approach and recommended that EPA apply this same principle to CHP 

units. 

Commenter 0214 stated that they support EPA's intent to subtract purchased power of adjacent 

facilities in calculating the 219,000 MWh applicability criteria threshold for CHP facilities.

Commenter 0267 stated that as part of any alternative exemption approach, EPA should include 

100% of the thermal energy produced (in addition to the electric power produced).

Response 1.6-1: As described Section III.D.2 of this final rule the industrial CHP exemption 

has been significantly expanded and is based permit restrictions limiting the amount of electricity 

that can be sold. The final exemption is based on considering both the primary purpose and the 

environmental benefit of the unit. Therefore, the allowable sales is based on the design efficiency 

of the CHP unit. Specifically, the industrial CHP exemption is based on permit limiting annual 

electric sales to the unit’s design efficiency multiplied by its potential electric output or 219,000 

MWh, whichever is greater. This limits applicability to CHP units that sell a significant 

percentages of the potential electric output. See section III.F.2 of this final rule for a discussion 

of thermal output credit. The EPA has concluded there is no need to specifically identify waste 

heat to power projects. To the extent these units meet the applicability criteria, they would be 

subject to the requirements in this final rule.

1.7 NON-FOSSIL-FIRED EGUS (E.G., BIOMASS)

Comment 1.7-1: Commenter 0247 stated that it would be arbitrary and capricious for EPA to 

regulate and treat these biogenic CO2 emissions in the same manner as fossil fuel emissions 

before EPA has determined whether biogenic CO2 emissions should be regulated as a pollutant 

under the Clean Air Act. The commenter mentioned Motor Vehicle Manufacturers Ass'n v. State 
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Farm Mutual Automobile Insurance Co., 463 U.S. 29 (1983), in which the Supreme Court held 

that an agency must satisfy two basic requirements to avoid violating the arbitrary and capricious 

standard. First, the agency must engage in "reasoned decision-making." Id. at 52. Second, ''the 

agency must . . . articulate a satisfactory explanation for its action.'' Id. The commenter stated 

that EPA fails to provide adequate justification for treating biogenic CO2 emissions the same as 

fossil fuel emissions in the Proposal despite EPA's recognition that the use of biomass for energy 

can result in climate benefits.

Commenter 0214 stated that EPA should have further encouraged the use of biogenic fuels by 

excluding all biogenic CO2 emissions from an affected facility's compliance calculation.

Commenter 0247 stated that the proposed standard should only apply to units that burn fossil 

fuels because the commenter believed that this applicability criteria is consistent with current 

applicability criteria under subpart Da and consistent with the January 2014 proposal for new 

units. Commenter (0247) opposed the portions of the proposal that suggested eliminating from 

applicability criteria fossil-fuel-firing capability. Commenter (0247) interpreted these portions of 

the proposal (see 79 FR 34979) to require biomass units to comply with the standard even if they 

do not burn any fossil fuel at all. Commenter (0247) acknowledged that the implications for 

biomass boilers was not fully developed in the proposal, and noted preamble discussions

indicating the proposed rule will still target only fossil-fuel-fired units, but the commenter was 

unable to understand the implications of the proposal for biomass-fired boilers. Commenter 

(0247) stated that applying the standards to biomass-fired EGUs would be unjustified and would 

contradict EPA's stated intention not to expand the applicability of current subpart Da regulations 

because biomass units are subject to operating constraints that can make it difficult for many 

units to meet the efficiency standard in the cogeneration unit definition unless the units co-fire 

significant amounts of fossil fuel. Commenter (0247) stated that the EPA had offered no 

justification for including biomass units, and the commenter opposed the EPA's suggestion to 

create a new subcategory for biomass units with no associated emission standard. The

commenter believed that the EPA would need to develop data sufficient to support a CO2

emission standard for non-fossil-fuel- fired EGUs and then propose new regulations for public 

comment. In summary, commenter (0247) stated that EPA should maintain the applicability 

requirement, consistent with the proposed NSPS for new units that more than 10 percent of the 

heat input come from fossil fuels.

Commenter 0203 stated that EPA should encourage the use of Biomass power via the following 

applicability criteria: (1) that a facility actually sells more than 1/3 of its potential electric output 

and more than 219,000 MWh to the grid annually; and (2) that the GHG standards are not 

applicable to facilities that combust 10% or less fossil fuel on a 3-year average basis. The 

commenter stated that EPA should retain the sales exemption so as to not impair grid reliability. 

The commenter also stated that Biomass sources should get credit for offsite factors related to 

the carbon cycle (sequestered CO2) for the biomass fuel being combusted at the unit.

Commenter 0193 stated that the proposed emission standards for new, modified and

reconstructed units in subpart Da should apply only if the unit burns more than 10 percent fossil 

fuels because as proposed, even if a boiler unit is modified to burn 99 percent biomass and one 

percent natural gas, the unit would be subject to the proposed standards and the proposed 

applicability criteria ignore the fact that small amounts of fossil fuels are often needed even in 
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units that burn primarily biomass; commenter (0193) opposed these applicability provisions 

because the commenter believed these provisions create significant disincentives for adopting 

CHP technologies when modifying or reconstructing subpart Da units.

Commenter 0192 opposed the proposed elimination of the 10 percent fossil fuel exemption for 

modified and reconstructed EGUs because this threshold was designed to exempt facilities that 

are capable of combusting fossil fuel, but burn primarily non fossil fuels, and the commenter

stated that the proposal offered no basis for regulating sources that combust insignificant 

amounts of fossil fuel. The commenter also described statements in the proposal that

characterized wood-fired EGUs as "inherently less efficient than fossil fuel-fired EGUs" as 

premature because the carbon efficiencies of wood-fired boilers is not relevant to GHG 

regulations in light of the Agency's current efforts developing an Accounting Framework for 

biogenic CO2 emissions from stationary sources. The commenter urged the EPA to refrain from 

removing the 10 percent fossil fuel exemption while the study on biogenic accounting is

ongoing, and the commenter urged the EPA to apply the 10 percent fossil fuel threshold to 

modified and reconstructed sources in the same manner proposed for newly constructed sources.

Commenter 0262 stated that EPA must avoid uncertainty and confusion by maintaining the 10% 

fossil fuel threshold in the rule's applicability criteria to ensure that modified and reconstructed 

biomass energy facilities are not included in the rule. The commenter also stated that biomass 

energy facilities are fundamentally different than fossil fuel-fired EGUs and should be excluded 

entirely from this source category.

Commenter 0197 stated that applicability requirements for co-firing with non-fossil fuel in fossil 

fuel-fired EGUs should be consistent with the Mercury and Air Toxics Standards rule for fossil 

fuel-fired EGUs, where the heat input threshold is no more than ten percent fossil fuel over a 

three-year rolling average, or no more than 15 percent fossil fuel on an annual basis.

Commenter 0195 stated that EPA's recent MATS Rule defines "fossil fuel-fired" as meaning 

"any EGU that fired fossil fuels for more than 10.0 percent of the average annual heat input 

during any 3 consecutive calendar years or for more than 15.0 percent of the annual heat input 

during any one calendar year after the applicable compliance date." The commenter felt that EPA 

should at least use the same exemption for the NSPS for consistency purposes as well as to foster 

the use of these renewable energy sources.

Commenter 0172 stated that they respectfully request as to the instant rulemaking that EPA (1) 

categorically exclude from the methods for determining compliance with the final NSPSs those 

CO2 emissions resulting from the combustion of biomass derived from annual herbaceous crops 

such as grains and cotton, and (2) expressly confirm that such exclusion keeps the NSPS from 

making such CO2, a pollutant subject to regulation, for purposes of the PSD and Title V 

permitting programs under the CAA.

Commenter 0172 stated that CO2 emissions resulting directly from the combustion of biomass 

derived from annual herbaceous crops are harmless to the global warming process. The 

commenter then cited two studies on this subject, and then stated the biomass associated with 

annual and perennial herbaceous vegetation is relatively ephemeral, and reductions in these 
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biomass stocks from harvesting, the burning of crop residues, or the integration of crop residues 

into soils, are balanced by stock increases from plant re-growth over a period of only one to a 

few years. The commenter stated consequently, companies should also not report any

sequestration in herbaceous biomass stocks. 

Commenter 0603 stated until EPA completes its scientific and regulatory review and issues a 

final policy on biogenic CO2 emissions, they urged EPA to exclude biogenic CO2 emissions 

from stationary sources from regulation under the CAA including under the Proposed Rule. 

Commenter 0159 stated that EPA cannot set what is clearly an arbitrary threshold until the 

Agency completes a rulemaking on the GHG accounting of biogenic emissions. The commenter 

stated to do so would ignore the very rulemaking on biogenic emissions that is now pending.

Commenter 0149 stated that without guidance from the EPA as to how biomass emissions will 

be addressed, it is premature to comment on the applicability requirements or standards for these 

units. The commenter also stated that EPA should provide clarity about biomass before taking 

further regulatory action addressing these units under section 111.

Commenter 0262 stated that EPA must defer regulation of Biogenic CO2 emissions until it 

develops a final policy to address biogenic CO2 emissions from stationary sources.

Commenter 0247 stated that there are substantial greenhouse gas reduction benefits in using 

biomass manufacturing residuals for energy in the forest products industry. The commenter 

stated that accounting for fossil fuel displacement and avoided emissions associated with 

disposal, the use of biomass residuals each year avoids the emission of approximately 181 

million metric tons of CO2e. (This is equivalent to removing about 35 million cars from the 

road.) The commenter noted some studies on the use of biomass fuels, and stated that based on 

the weight of this scientific evidence and data, EPA can clearly conclude that the use of forest 

products manufacturing residuals for energy results in a climate benefit and should therefore be 

categorically exempt from regulation. 

Commenter 0247 went on to say that because growth of biomass in the United States is

exceeding the amount harvested, biogenic CO2 emissions from all types of biomass-derived fuels 

do not contribute to atmospheric carbon levels unlike fossil fuel emissions.

Commenter 0262 stated that biogenic CO2 emission does not increase atmospheric CO2

concentrations. The commenter noted the scientific principles of the forest carbon cycle are well 

understood and uncontroversial. The commenter stated wood products, including biomass 

combusted for energy, are intertwined with the natural forest carbon cycle and their production 

and use are compatible with CO2 reduction strategies. 

Commenter 0149 stated that the EPA should not subject limited-use-oil-based units or Biomass

units to regulation under CAA section 111(d).

Commenter 0282 stated that the two applicability TSDs both have flaws regarding their

treatment of Biomass fuels. The commenter first stated that the "Broad Applicability" approach 
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would be arbitrary and capricious because it imposes no emissions standard on units burning 

primarily biomass. The commenter then stated that the "Proposed applicability" TSD would 

make the emissions standards for modified and reconstructed boilers and IGCC units applicable 

to modified and reconstructed biomass-burning units. As addressed in the commenter's Section 

111(b) Comments, the Clean Air Act requires numeric performance standards for biomassburning power plants, which tend to be extremely carbon-intensive. The commenter stated 

however, that section 111 does not permit EPA to establish different standards for new power 

plants on one hand, and reconstructed and modified plants on the other. The amount of fossil 

fuels consumed by these plants aside, EPA has offered no justification grounded in the text of 

section 111 for creating a standard that applies only to modified and reconstructed plants.

Commenters 0149, 0257 stated that Biomass units should be regulated under a different 

subcategory with appropriate standards. The commenter stated, however, that they are unable to 

comment as to what appropriate standards would be because EPA has not proposed any 

numerical standard for these units and there is no data to support such a standard.

Response 1.7-1: Dedicated non-fossil units subject to a permit restricting the use of fossil fuel to 

10 percent or less of the annual capacity factor are subject to the requirements of this final rule. 

See section III.D.1 of the NSPS preamble for discussion of dedicated non-fossil fuel units.

Comment 1.7-2: Commenter 0280 stated that existing EGUs that burn biomass must remain 

subject to CAA section 111(d) regardless of whether they undergo modifications or

reconstructions that affect the amount of fossil fuel utilized. The commenter disagreed, however, 

that new applicability methodologies are necessary to ensure continuous application of CAA 

section 111(d) to biomass-fueled EGUs that modify or reconstruct.

Response 1.7-2: Units that reconstruct or modify and become subject to a 111(b) emission 

standard will no longer be considered existing units for 111(d) purposes.

1.8 INTEGRATED AND CO-LOCATED NON-EMITTING ENERGY 

GENERATION EQUIPMENT

Comment 1.8-1: Commenter 0152, 0157, 0165, 0171, 0197, 0239, 0254 stated that EPA should 

continue its historic practice of interpreting an affected facility to include only the steam 

generating unit boiler island. In other words, the commenters stated physical or operational 

changes outside of the utility boiler island, such as changes to a turbine, generator, coal handling 

system, ash handling system, or water treatment system would not be subject to review under 

Section 111 performance standards. Commenter 0157 stated that non-emitting support systems, 

such as electric-powered water-intake structures and associated pumping or general facility 

HVAC systems, are not included in Section 111 source definitions. The commenter stated 

therefore, the emissions standards under EPA's proposed rule should be based only on what is 

achievable at the affected source, which would be defined as emissions based on either fuel 

consumed by the actual emissions source or the gross output (MWh-gross) from the emissions 

source.

Commenters 0267, 0195 stated that the definition of a stationary source under Section 302(z) of 

the CAA does not encompass "co-located non-emitting energy generation." The commenter 
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stated that the EPA has also provided no boundaries or limitations on what could be included 

under such a general description, especially since the non-emitting generation does not have to 

be “integrated into the operation” of the affected facility. Lastly, commenter 0267 noted that 

EPA's inclusion of non-emitting generation would likely discourage the use of non-emitting 

generation sources and is thus at odds with the overarching purpose of the Agency's Carbon 

Pollution Standards and federal and state efforts to expand renewable energy generation.

Commenter 0213 stated that EPA should not redefine "affected facility" so as to permit EGUs to 

include in their emissions calculations electricity generated by co-located technology that is not 

integrated into the regulated unit as an engineering matter. The commenter stated that a provision 

of this nature will permit operators to simply tack on emitting units at pre-existing wind farms or 

solar arrays and avoid addressing their carbon emissions. 

Commenter 0242 stated that the discussion to included non-emitting energy generation

equipment is not appropriate and overly complicated. The commenter stated that there is the 

potential that this rule would include units that function as startup boilers but are not used for 

generating electricity; units that may not be designed for efficiency but for relatively quick 

startup since they are used infrequently. These are the types of circumstances where, the 

commenter believed, issues will arise simply due to the complexity of these proposed changes.

Commenter 0197 urged the EPA to limit their definition of BSER to actions that can be taken at 

the affected existing fossil fuel-fired EGUs, without redefining the source. 

Response 1.8-1: This final rule includes integrated, but not co-located non-emitting generating 

units, in the definition of affected facility. This approach is necessary to avoid circumvention of 

the rule and provides additional compliance flexibilities.

1.9 COMPLIANCE PERIOD

Comment 1.9-1: Commenters 0150, 0192, 0214, 0215 stated that EPA should adopt a single 

compliance period each year on a calendar year or longer basis. The commenter stated that this 

approach would increase operational flexibility without any environmental impacts. The 

commenter stated EPA should take the same approach in any final rules for new units.

Commenter 0157 stated that they support the use of the annual calendar year. The commenter

also stated that EPA is relying on a calendar year for purposes of establishing the best efficiency 

baseline, and it seems appropriate to use a compliance period equivalent to the period used to set 

the standard.

Commenters 0260, 0197 stated that the 12-operating-month rolling average standard already 

adequately ensures compliance.

Commenter 0157 stated that EPA's proposal to subject units to both 111(b) and 111(d) also 

means that a unit could be facing two different rolling 12-month compliance requirements for the 

same pollutant. The commenter also stated that if EPA proceeds with its proposal, using a 12-
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month calendar year compliance period for 111(b) would make the rule much less complicated to 

implement.

Commenter 0182 suggested that EPA consider providing a multi-year compliance option for 

modified and reconstructed EGUs, but should not penalize EGUs by adopting a more stringent 

standard for multi-year compliance.

Commenter 0224 stated that a three-year averaging methodology should be used. The

commenter stated the two main factors affecting unit operations, weather and maintenance, can 

vary greatly from year to year, and therefore the commenter felt that a 3 year period better 

reflects EGU operations.

Commenter 0253 urged the EPA that a 3-year averaging methodology as better reflecting the 

normal ebb and flow in EGU operations. The commenter stated that the two main factors 

affecting unit operations, weather and maintenance, can vary greatly from year to year, and can 

also last for extended periods, e.g., an abnormally hot summer or cold winter. The commenter 

stated unscheduled outages requiring repair or replacement also may last over an extended time 

period due to such things as equipment shortage, shipment delays, procurement process, and 

coordination of installation with scheduled maintenance or other planned outages.

The commenter stated that as a result, rolling 12-month or calendar year average may be severely 

skewed in a given year because of unforeseen or unpredicted events. Using a 3-year averaging 

methodology would tend to level out such deviations, and provide a better overall view of 

normal operations. The commenter felt that it would also provide more flexibility for EGUs to 

adjust their output so that if emissions were abnormally high over time due to these types of 

circumstances, the plant could scale back operations to bring emissions into the regulated level 

within the averaging period.

Commenter 0176 was concerned that while the proposed three-year averaging approach allows 

for seasonal and some annual flexibility in determining which units constitute an EGU, it may 

prove too short when dealing with cyclical climate shifts that oscillate on longer temporal scales. 

The commenter stated that should these patterns lead to a period of decreased available wind 

generation, more power from alternative energy sources will have to be used, and it is possible 

that NGSC turbines will have to bear this burden (a condition that is economically undesirable) 

until the extended situation either comes to an end or the SC units can be retrofitted with NGCC 

capabilities. The commenter recommended that EPA use a five-year rolling average to help 

assure that NGSC units can be used to support wind generation. The commenter stated this 

would provide greater flexibility in adapting to longer-term variations in power demand caused 

by climate factors such as decadal (and multi-decadal) oscillations.

Commenter 0192 also stated that EPA should incorporate an alternative 84-month compliance 

period, as it did in the January 2014 proposal. The commenter noted that the 84-month

compliance option will allow facilities to better compensate for unexpected, short-term emissions 

excursions. The commenter stated, however, that this alternative should not be coupled with 

more stringent regulations. 
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Commenter 0156 stated that the performance standard should reflect that, even for the most 

efficient units, heat rate efficiency degrades over time, and routine maintenance is required to 

maintain efficiencies. The commenter stated the timing of turbine maintenance varies between 

facilities, but usually occurs on a five to seven year basis. The commenter stated the compliance 

period for this performance standard should reflect reasonable maintenance schedules.

Response 1.9-1: The emission standards in this final rule are based on 12-operating month 

averages. See section IV.C of the NSPS preamble for discussion of the compliance period for 

new, modified, and reconstructed steam generating units. See section IX.D of the NSPS

preamble for discussion of compliance periods for the three subcategories of new, modified, and 

reconstructed combustion turbines.

Comment 1.9-2: Commenter 0213 stated that EPA should dispense with its capacity factor 

threshold entirely for applicability determinations, but if it retains that policy, the current rule 

could be interpreted to grant sources up to a year of unregulated emissions after triggering 

applicability. The commenter stated that instead, EPA should make clear that the compliance 

period should begin at the end of the calendar month during which a source crosses the 

applicability threshold, not up to a full year later.

Response 1.9-2: The final applicability in this final rule is a modification of the broad 

applicability approach we solicited comment on. Retrospective criteria will not be used to 

determine applicability. They are however used as subcategorization criteria.

Comment 1.9-3: Commenter 0215 stated that with respect to reporting under this NSPS, EPA 

suggests in the preamble that EGUs would begin "reporting" data on the same schedule as Part 

75 (i.e., when the monitoring system certification is complete or when the 180-day period in 

section 75.4 expires, whichever is sooner). The commenter noted however, that EPA proposes 

rule language that would not require submission of the first quarterly report until the EGU has 

accumulated the number of operating months needed to calculate compliance. Proposed 

Applicability Text, Subpart TTTT section 60.5555(a)(1), Subpart Da section 60.46Da(h)(3)(i), 

Subpart KKKK section 60.4376(b)(1). The commenter supported the proposed rule language 

under which quarterly reporting would not be required under this NSPS until there are both a 

compliance value, and a percent of valid mass emissions rates over the compliance period, that 

are ready to report (i.e., until the EGU has accumulated the necessary number of operating 

months of data). The commenter felt that because all of the data needed to calculate compliance 

already are recorded and reported under Part 75, there is no reason to separately require any 

reporting under this NSPS until the calendar quarter that contains the end of the month that 

corresponds to the end of the first compliance period.

Commenter 0215 stated that with respect to the first performance test or compliance period, 

EPA's reference to the Part 75 reporting provision in section 75.64(a) is unnecessarily confusing. 

79 Fed. Reg. at 34,978. The commenter stated moreover, if compliance is based on a 12-month 

rolling average, the period should begin with the first operating month following the month in 

which monitoring system certification is complete, or the month when the 180-day period in 

section 75.4 expires, whichever is earlier.
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Commenter 0215 stated that EPA proposes that the requirement to perform an initial stack test 

under section 60.8 would not apply. The commenter stated that proposal is implemented in 

Proposed Applicability Text, Subpart TTTT, Table 3, which identifies section 60.8 as 

inapplicable. The commenter agreed that an initial 3-run performance test is not necessary, and 

would be inappropriate given that EPA has not established its achievability.

Commenters 0260, 0197 did not support a short-term performance test.

Response 1.9-3: See sections X.C and D of the NSPS preamble for discussion of the

performance testing requirements. See section X.E of the NSPS preamble for discussion of the 

reporting requirements.

Comment 1.9-4: Commenter 0263 stated that recent energy assessments, those completed 

within three years of a modification, should be considered to meet the requirements of this rule 

provided that companies can make an equivalency demonstration. The commenter stated that 

relying on an energy management plan program that is compatible with ISO 50001 should not be 

prohibited by this rule inasmuch as the program can demonstrate equivalency with the general 

requirements of the energy assessment. The commenter recommended that, for consistency, EPA 

should not require certification of energy assessors who conducted recent energy assessments or 

who perform audits under a company energy management plan.

Response 1.9-4: Energy assessments are not included in this final rule

1.10 PERIODS OF STARTUP, SHUTDOWN, AND MALFUNCTION

Comment 1.10-1: Commenter 0131 stated that they agreed with the proposed exclusion of 

malfunctions from the compliance calculations. However, the commenter strongly disagreed that 

startups and shutdowns are "predictable and routine" and stated that the unpredictable

components of energy pricing make periods of startup and shutdown uncertain. The commenter 

recommended exclusion of periods of startup and shutdown in the proposed rule. The commenter 

also noted that events outside of the control of the plant, like the polar vortex, may make the 

burning of fuels besides natural gas a necessity, and therefore the commenter believed that the 

EPA should not place standards on units that use fuel oil because natural gas may not be 

available to them.

Commenter 0183 stated that EPA's Treatment of Startups and Shutdowns is arbitrary and 

capricious and inconsistent with existing regulations. The commenter stated that EPA's 

assumptions that startups and shutdowns are predictable, and thus CO2 emissions could be 

avoided or reduced during those periods, is erroneous and unsupported. The commenter noted 

that no control technology exists that can be applied during these transitional periods, and EPA 

identifies none. The commenter felt that if standards were to apply during startups and

shutdowns in the same way they apply to full load operation, they would not be achievable or 

adequately demonstrated. The commenter continued by stating that if a standard must be set for 

these periods, an annual calendar year limit would be a more appropriate averaging period than a 

12-month rolling limit. Lastly, the commenter stated that the proposed SSM standards are not 

demonstrated in practice, and therefore, are unachievable.
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Commenter 0241 stated that Startup and Shutdown emissions are not steady-state emissions, and 

therefore they should be granted greater flexibility under the rule. The commenter noted that the 

EPA expects the SSM provisions will have a minimal effect on total emissions, and thus the 

commenter recommended excluding these periods from the ruling.

Commenter 0151, 0142 urged EPA to not include periods of startup and shutdown as periods of 

partial load in the compliance with the standard. The commenter stated that although these 

periods may be small for baseload units, they are not small for load-following units that support 

renewable energy sources. The commenter also stated that requiring compliance with the 

proposed standards at all times would result in units being dispatched without regard to system 

needs. 

Commenter 0222, 0260 requested that the EPA not include periods of startup, shutdown, and 

malfunction in calculating compliance with the standards in favor of work practice or operational 

standards. In regards to malfunctions, commenter 0260 cited the opinion of U.S. Court of 

Appeals for the District of Columbia Circuit in Natural Resources Defense Council v. EPA, No. 

10-1371 (D.C. Cir. Apr. 18, 2014). The commenter stated that even properly maintained 

equipment may experience unexpected failures that result in periods of higher CO2 emissions.

Commenter 0192, 0270 stated that the EPA has abandoned the affirmative defense language in 

the ruling in favor of using a case-by-case enforcement discretion to provide flexibility.

However, the commenter noted, the courts have already held that promising enforcement

discretion is not a substitute for setting achievable standards in the first place. The commenter 

requested that the EPA withdraw the Proposed Rule until EPA has properly assessed whether the 

proposed emission standards can be met with the identified control technology, even during SSM 

periods.

Commenter 0169, 0196 stated that EPA should work with Congress to develop an affirmative 

defense provision for startups, shutdowns, and malfunctions under the CAA.

Commenter 0192, 0196, 0214 stated that the EPA should not abandon the affirmative defense 

language, and that the court's decision in NRDC vs. EPA 749 F.3d 1055 does not require EPA to 

abandon this language. Specifically, the commenter stated that "EPA is incorrect to the extent 

that it suggests that the D.C. Circuit's decision in NRDC, 749 F.3d 1055, bars it from providing 

an affirmative defense for malfunctions under Section 111. That decision involved an EPA 

regulation under Section 112 and, thus, is not directly applicable here. Further, as the D.C. 

Circuit recognized, Id. at 1063, n.2, in Luminant Generation Co. v. EPA, 714 F.3d 841 (5th Cir. 

2013), the Fifth Circuit affirmed the inclusion of an affirmative defense in a State

Implementation Plan. Thus, in the absence of controlling precedent under Section 111, EPA is 

not prohibited by the Clean Air Act from including an affirmative defense for malfunctions in a 

final rule and EPA should include such a defense as it originally proposed to do in the January 

2014 proposal."

Commenter 0203 stated that since EPA did not consider SSM events when determining the 

standard, it is unfair and poor engineering practice to impose these standards during these events. 
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The commenter also stated, however, that if EPA insists that such emissions are part of the actual 

performance standard, then they must properly account for SSM emissions. 

Commenter 0169 stated that EPA concedes that starting up unit and operating a unit in a 

transient state (rather than steady state) erodes unit efficiency. The commenter stated yet, EPA 

essentially proposes this as BSER in the Section 111 (d) rule and promotes the use of coal-fired 

units in this fashion by setting state goals that states cannot meet without requiring EGUs to 

derate or startup and shutdown frequently. The commenter therefore recommended that startup 

and shutdown emissions should not be included in the CO2 emission standard, and the judicial 

requirement applying emission rates to startups and shutdowns should be revisited or, in the 

alternative, the emission rate should be set higher to accommodate necessary startups and 

shutdowns

Commenter 0188 stated that Malfunctions are by definition unpredictable, and therefore plants 

should not be held to a standard that is beyond their control. The commenter also stated that any 

malfunction standard cannot be adequately demonstrated, because of the varied nature of 

malfunctions themselves. 

Commenter 0215 stated that EPA cannot lawfully punish unavoidable malfunctions as violations. 

The commenter stated neither the exercise of discretion in bringing an enforcement action, nor 

the exercise of discretion in imposing penalties in an enforcement action, is an adequate

substitute for an achievable standard. The commenter noted that EPA presents two arguments for 

not considering malfunctions in its standard setting. First, according to EPA, section 111 does 

not require EPA to account for malfunctions in setting standards because those standards are 

only required to reflect the degree of emission limitation achievable through BSER, and EPA 

says BSER "is more appropriately understood to include units operating in such a way as to 

avoid malfunctions." Second, EPA argues that it should not be required to account for

malfunctions in the standard setting process because it would be "difficult, if not impossible" to 

do so in light of the fact that "the performance of units that are malfunctioning is not 'reasonably' 

foreseeable." The commenter anticipated that EPA may respond by asserting that it cannot 

establish work practice standards under section 111(h), because doing so also would be too 

difficult. The commented noted EPA already specified the equivalent of a work practice standard 

in its vacated affirmative defense provisions. The commenter stated those provisions first require 

the EGU to establish that the event was in fact a malfunction and then to establish that the 

facility not only corrected the problem "as expeditiously as possible," but also took all

reasonable operational steps to minimize the duration and severity of the event. 

Commenters 0222, 0247, 0270 stated that the EPA's decision to eliminate SSM provisions has 

not been justified, and that it goes against past EPA action. The commenter referenced the Sierra 

Club v. EPA, 551 F.3d 1019, 1027 (D.C. Cir. 2008), cert. denied, 130 S. Ct. 1735 (2010) case 

and stated that this ruling has no determination on the provisions of 111(b), and therefore the 

EPA should not remove the SSM provisions. 

Commenter 0282 stated that they agree with the EPA's determination to incorporate periods of 

Startup and Shutdown into the standard. The commenter also agreed that the EPA is not required 

to factor malfunctions into its emission standard.
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Commenter 0201, 0158 stated that EPA must account for malfunctions in establishing emission 

standards. The commenter stated if the standard is to be achieved at all times, the standard must 

contemplate periods of malfunction, as well as periods of startup and shutdown.

Commenter 0157, 0169, 0222 stated that the proposed 111(b) and 111(d) standards are

synergistic, and that Building Block 2 of the ESPS will create more startups and shutdowns at 

most plants. Commenter (0157) stated that the EPA believes that periods of Startup and 

Shutdown will be small relative to operating time, however they base this assumption on past 

data. In the future, circumstances will be different because of the ESPS standard, and therefore 

that assumption is no longer valid.

Commenter 0283 agreed that the assumptions the EPA has made regarding the duration and 

frequency of Startups and Shutdowns after the promulgation of this ruling are invalid. The 

commenter urged the EPA to recognize the need for different standards during startup and 

shutdown as it has done elsewhere in implementing the Clean Air Act. 

Commenter 0222 stated that as more renewable energy units are brought online, particularly 

sources like wind with variable capacity factors, more base load unit operations may have to be 

reduced, leading to an increase in startup and shutdown. 

Response 1.10-1: The emissions data reviewed as part of this final rule included all periods of 

operation. Therefore there is no basis for excluding those periods. See section V.J of the NSPS 

preamble for discussion of SSM periods. This final rule does not include affirmative defense.

Comment 1.10-2: Commenters 0257, 0152, 0254, 0178 recommended that the EPA establish a 

work practice standard for periods of malfunction that would allow the source to establish that an 

even was in fact a malfunction and allow the source to demonstrate that it corrected the problem 

as expeditiously as possible and took all the reasonable steps to minimize the duration and 

severity of the event. The commenter noted that EPA proposes to include data collected during 

malfunctions in the compliance calculations, and that the EPA proposes to resolve any 

inappropriate ramifications via the exercise of its enforcement discretion. The commenter stated 

that the exercise of discretion in bringing in enforcement action nor the exercise of discretion in 

imposing penalties is an adequate substitute for promulgating an achievable standard.

Commenter 0178 stated that it is impossible to trace any particular environmental impact 

resulting from climate change to any particular CO2 emission source, especially since the 

emissions that could occur during a period of malfunction are miniscule in comparison to global 

CO2 emissions. The commenter stated as a result, it is impossible to "minimize" any such 

unknown impacts that may result during a period of malfunction that causes excess CO2

emissions. Because this factor does not make sense in the context of CO2 emissions, commenter

urged EPA to exclude it from any work practice standards that EPA may finalize.

Commenter 0222 stated that if the EPA still feels compelled to propose standards during periods 

of startup and shutdown that they should choose to establish work practice standards for these 

periods. The commenter referenced the Boiler NESHAP for Major Sources as an example of 

EPA creating work practice standards during startup and shutdown periods.
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Commenter 0214 stated that EPA did not account for SSM efficiency levels in developing its 

standards, the standards should not apply during those periods. Instead, the commenter 

recommended, EPA should recognize that the very reasons that it has provided for ignoring SSM 

periods in developing the proposed standards are the same reasons that a work practice standard 

should apply during those periods rather than a numeric emissions limit "because emissions 

during SSM periods are difficult if not impossible to measure and because higher emissions rates 

during those periods are unavoidable."

Commenter 0178 urged EPA to promulgate work practice or operational standards for periods of 

startup and shutdown under the NSPS. The commenter stated EPA proposes to include periods 

of startup and shutdown in the compliance calculation as periods of partial load. Commenter

urged EPA not to include periods of startup and shutdown as periods of partial load in the 

calculation of compliance with the standard.

Response 1.10-2: Work practice standards are not included as part of this final rule.

1.11 OTHER

Comment 1.11-1: Regarding the proposal's request for comment on the usage of energy storage 

and demand-side strategies for managing integration of intermittent renewable resources, 

commenter (0149) stated that it is not clear what EPA can do, in the context of setting achievable 

standards for simple-cycle CTs, without information about energy storage systems and demand 

response; the commenter acknowledged that energy storage systems and demand response can 

potentially reduce reliance on natural gas combustion in the future, but the commenter believed

that these emerging technologies are not relevant to the current rulemaking under section 111(b) 

which requires that the EPA develop achievable standards based on what is achievable at the 

time they are proposed.

Response 1.11-1: Energy storage technologies are not included as part of this final rule.

Comment 1.11-2: Commenter 0197, 0213 stated that EPA should provide specific calculation 

procedures for emissions from regulated cogenerating facilities and for dual-firing facilities.

Response 1.11-2: CHP units subject the requirements of this final rule will determine

compliance by adding the electric output and the useful thermal output. Useful thermal output is 

credited at 100 percent. Equations have been included in this final rule to assist the regulated 

community. The EPA notes that certain CHP units will divide their electric output by 0.95 to 

recognize the environmental benefit of reduced line losses. Combustion turbines burning 10 

percent or more non-natural gas will be subject to the emission standard for multi-fuel units. An 

equation is included to aid in calculating the applicable emission standard.

Comment 1.11-3: LATE COMMENT Commenter 0297 engaged a consulting firm to create a 

database of all coal-fired units, to help determine which units may potentially modify or

reconstruct. The commenter stated the data was compiled from the EPA Clean Air Markets 

Division (CAMD) CEMS program. The commenter stated that the consulting firm "created a 

new CO2 emissions database that contained annual average emissions data for all coal-fired units 

for the period 2003-2012". The commenter noted that all hours for which data were missing were 
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excluded from the database, as the algorithms used to replace missing data err on the high side, 

creating an inflated record of emission. The commenter indicated the firm recorded the following 

data about each plant:

• Average CO2 emission rate (lb/MWh(g)) based on hourly values

• Average CO2 emission rate (lb/MWh(g)) based on annual total CO2 mass emissions and

gross generation

• Average CO2 emission rate (lb/MWh(g)) based on annual total CO2 mass emissions and

• net generation

• Total CO2 mass emissions (tons/yr)

• Total gross generation (MWh(g))

• Total net generation (MWh(g))

• Total operating hours (hrs/yr)

The commenter noted that the firm estimated net generation based on a constant station service 

factor of 7.5 percent rather than using the net generation data from the Energy Information Agency 

(EIA), which was found to contain reporting errors that resulted in anomalous CO2 emissions rates in 

the EPA database. The commenter indicated the criteria used to determine candidates for

modification and reconstruction were units with 300 MW generating capacity or greater and had 

been in commercial service for less than 35 years. The commenter noted the firm utilized various 

statistical methods to remove outliers, with the purpose of eliminating reporting bias due to 

apportionment. 

(ALSO LATE) Commenter 0297 submitted a separate document analyzing the above

information in combination with a second database. The commenter indicated this report updates 

the achievability analysis for modified units by calculating estimated emission limits under the 

Proposed Rule using two alternative sets of CO2 emissions data and power output data that are both 

consistent with the Proposed Rule's methodology.

Response 1.11-3: No response since this is a late comment.