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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

................................ ................................ ................................ ................................ .. 391

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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 p rovisions for new, modified, reconstructed, and existing sources and the commenters believe d the proposed inconsistent applicability criteria will cause significant confusion during implementation. Commenters (0195, 0242) noted that the proposal for modifi ed 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 t hat will be affected under s ection 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 unla wful 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 identica l 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 believe d that the Agency cannot define a source category differently for new, modified, and reconstructed sources. The commenter also believe d that the Agency cannot propose to alter the applicability criteria for new sources in the proposed rule for modified and reconstructed sources. Commenter (0150)
oppose d the proposal's basis for elimin ating the one

- third sales criterion and the low fossil use criterion (to broaden the scope of subsequent 111(d) guidelines) because the commenter believe d 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.1

- 3 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 oppo rtunity 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 o pposed 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 differ ent 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 c annot 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 appli cability 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 ru le.

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 nonsen sical: the reconstruction analysis itself is that "guidance." The commenter1

- 4 stated the entire purpose of the reconstruction analysis is to determine when an existing unit has become "essentially a newly constructed source."

Commenter (0131) believe d 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 g eneration. 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 EP A'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 subj ected 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 believe d 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 standa rd for reconstructed sources to projects a t reconstructed facilities because the commenter believe d that applying both standards would discourage plant owners from engaging in projects to improve efficiency. Accordingly, commenter (0131) recommended that o nly 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 capit al 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 b ecause 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 f inal rule does not amend the reconstruction provision included in the general provisions.1

- 5 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 ensu res 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 do es 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 CO 2

. 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 sta ndards 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 appr opriate in this case due to the differences in CO 2 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 reconstruc ted 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 sho rt 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% CO 2 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

us e 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.1

- 6 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 techn ologies 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 s ubcategory 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 subcategori zation 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 a nd 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 CO 2 emissions. The commenter cited the MATS ru les 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 CRITER IA

Comment 1.2

- 1: In response to the EPA's request f or 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" versio n 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 co verage 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 indicatio n 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 th at 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 021 5 stated1

- 7 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 w ould 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 s ources. 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 docu ment 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 st ated 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 CO 2 emissions from new, modified, and reconstructed sources tha t 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 Regul atory Text (Broad Applicability)."1

- 8 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 com menter 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 section s 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 applicabil ity 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

commen ter 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 MW h 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, 01 95, 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 com menters 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 an d 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 sequenc e); 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 q uick

- response capabilities for managing forecasting errors, integration of renewables,1

- 9 unanticipated loss of generation, unanticipated loss of load, localized emergency conditions, and transmission line constraints. Commenter (0257) discussed scenarios req uiring 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 turb ines 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 g enerating 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 cycl e 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 cha nging 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 com menters stated that as more renewables are added to the grid, simple

cycle units must be available to system operators to enable flexible operations and that simple

cycle units must be permitted with sufficient annual capacity factors to respond to the
unp redictable, 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 pe ak 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 s imple 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 expresse d 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 nu merous 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 ren ewable 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 sour ce. 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 prevent1

- 10 these issues in the future. However, the comme nter 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 c omplete 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) fro m 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,

a nd 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 u nder 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 oth er short

term 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 appli cability 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 exp anding 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 tha t 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 r elate 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 014 9 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)1

- 11 guidelines, it is likely that simple

- cycle CTs (both new and existing) would be needed to facilita te 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 (0 149) 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 fos ter 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 o f 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.

C ommenter 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 red uce 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 gas

fired generators and diesel

- fired reciprocating internal com bustion engines. Commenter (0181) believed that these new types of sources and all other EGUs should be subject to CO 2 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 be cause 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 le ss 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 so me 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 cycl e 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 simple1

- 12 cycle often operate under conditions that do not permit maximum efficiency. Commenter (0181) referenced PSD permit limitations for CO 2 emissions from simple cycle turbines to support the position that simple cycle units are capable of meeting a num erical CO 2 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 CO 2 /MWh; t he Perryman 6 unit in Maryland has a GHG limit of 1,394 lb CO 2 e/MWh (gross) while firing natural gas; the commenter also stated that the State of New Your established a limit of 1,450 lb CO 2 /MWh for new simple cycle turbines. Commenter (0181) stated that h ow 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 "technolo gically 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 so urce 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 exem pt 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 capac ity 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 facto r 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 opera tors first dispatch the units having higher efficiencies, lower marginal costs, and lower CO 2 emission rates, than either low capacity or load

- following units normally provide. Commenter (0253) stated that due to their lower efficiencies, low capacity (sim ple 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 inheren tly 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 unit s first, exempting the less efficient peaking units and load

- following units will not likely increase CO 2 emissions, and commenter (0253) stated that the EPA can assure that CO 2 emissions do not increase by providing no exemption to peaking units and load

- following units during years when either type operates above a base load1

- 13 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 avoidin g 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 p rojected 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 gri d 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.

Commen ter 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 combus tion 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 t he 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 provisi ons 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 CO 2 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 appropriat e CO 2 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 82 5 lb CO 2 /MWh.1

- 14 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 applica bility 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 a re 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 r esult, 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 meaning ful 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 app roach 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: Th e final applicability criteria are based on operating permit conditions and not on actual operati ng 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 Sec tions 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 t he 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

s ubcategories 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 stand ard 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 includ e 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
t reatment 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 use1

- 15 on

- site and not for sale, and commenter (0157) stated that, in al l 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 o n 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 th e general applicability criteria. A n 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 UNI T

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 com menter 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 s upporting 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 rec onstructed 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 lo ads 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 COMBUSTIO N 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 though1

- 16 the lower capacity factor would likely accompany a lower efficiency. Commenter (0176) disagreed with the EPA's jus tification (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 reco nstructed 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 requi rement.

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 (a nd 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 criterio n (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 modif ied 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 modifi ed 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 sup plies 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 EG U 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" appro ach 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 con ditions.1

- 17 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 l arger 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 u rged 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 t urbines. Commenter s (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 u nits then the commenter supported a separate subcategory for low capacity factor units with an a ssociated 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 explic itly exclude all simple cycle turbines and peaking units because of their unique roles in the portfolio of energy generating assets an d because the commenter believed it is inappropriate and unreasonable to include simple cycle units and other peaking tech nologies 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 uni ts operate only in critical situations and are vital to ensure reliability. For this reason, EPA created a1

- 18 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 f requently 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 reconstruct ed 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 t he 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 CO 2 emission rate) depends on the unit's capacity factor, the one

- third sales criterion is likely even more necessa ry 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 efficien t units, and the commenter also stated that the proposed applicability criteria also unfairly promote use of reciprocating diesel engines, which can have higher CO 2 emission rates than natural gas fired affected sources under the proposed applicability cri teria; 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 ap plies 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 becau se 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 r enewable 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 renewable1

- 19 generation. Commenter (0225) divided generating assets use d 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 c ategory 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 generatin g capacity integral to the increasing development of renewable resources in California. Commenter (0225) stated that flexible EGUs share three primary characteristics: dispatchability/load

following, 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 s tability 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 th at 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.

Co mmenter (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 CT s 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 sugges ted 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 system

wide emission rate (including renewable s) is 668 lb CO 2 e/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 t o 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 n ewest 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 CO 2 /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 emi tting a total of 1266 pounds of CO 2 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 increas ing 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 capaci ty 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 exclusi on 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 generat ing 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

- b ased 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 c ommenter believed that this approach would encourage high efficiency power generation and low CO 2 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 or1

- 21 greater would be directionally h elpful 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
ge nerating 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 operat e 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 expla in 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 non

base 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 thresh old 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 slidin g 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 rea sonable. 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 ap plicability 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: Com menter 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 all ow units to escape regulation by making small adjustments to their fuel input.

Commenter 0213 opposed us e of the 10 percent fossil fuel use criteria for stationary combustion turbines because the commenter believe d the purpose of this criteria is to restri ct applicability to base load and load

- following units, and the commenter oppose d this policy. The commenter believe d 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 burn ed . 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 combusti on 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 combi ned cycle components within a single subcategory, a nd the commenter believe d that simple cycle turbines should also be included in this subcategory. Commenter (0213) stated that applicability and compliance provisions should not distinguish between heat in put to the combustion turbine versus heat input to the steam generator; similarly the commenter recommend ed that there should be no distinction between electricity generated by the combustion turbine generator and the steam turbine generator for the purpos es 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 n ot 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 disp atcher 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 based1

- 23 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, 0 151, 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 op erators 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 f or 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 n ot 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, derive d 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 mo de. 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 int o 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 CO 2 /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 i t is difficult to assess a variable standard without reference to the
actua l 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.1

- 24 

### 1 .4. 2 Large/Small Combustion Turbine Cut

- point

Comment 1.4

- 9: Commenter 0212 stated that EPA should establish a single performance standar d 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 technol og ies. The commenter stated that b y 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 su pport increasing the size distinction between large and small combustion turbines to at least 1,000 MM Btu/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 fue l.

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 MM Btu/h standard, mainly that it assumed an efficiency of 44%, which is higher than even the most efficient simple cycle turbines. The commenter recommend ed raising the cut off to 950 MM Btu/h to better reflect the current simple cycle industry.

Comme nter 0250 stated that the only rea son 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 prov id ed no other justification for this distinction. The commenter also stated that subpart KKKK do es not explain the distinction ei ther, 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 Turb ines

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 permitte d 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 wh en 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 CO 2 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 costs1

- 25 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 cap acity factor.

Response 1.4

- 10: Affected combustion turbines burning 10 percen t 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 c ombustion 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 sufficien tly clear that oil and
gas

- fired s team 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 CO 2 through a
conveyan ce designed and constructed to capture that pollutant. The commenter also state d that NESHAP s and work practice standards that have recently been passed do enough to limit emissions from coal refuse plants. The commenter recommend ed 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 a lso recommend ed that EPA provide relief for Coal Refuse CFB's by exempting CO 2 emissions from the calcination of limestone at t hese plants, as it is a part of their SOx emission controls.

Commenter 0182 state d that the EPA should exempt coal refuse CFB units relative to their CO 2 emissions to the extent that these units offset the uncontrolled ground level emissions from burning l egacy 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 disc ussion 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 commenter1

- 26 stated that they are currently unable to shutdown two units due to rulin gs 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

mo dify or reconstruct. Therefore, the units will continue to be available as existing units.

Comment 1.5

- 3: Commenter 0164 request ed exemptions for their units because of their geographic location (Central Alaska). The commenter fear ed 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 note d 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 tu rbines without access to natural gas would not be subject to the requirements in this final rule.



### 1.6 CHP

Comment 1.6

- 1: Commente r s 0180, 0192, 0196, 0212, 0267 stated that they support the exemption of combined heat and power units in order to encourage the implementation o f this technology. Commenter s (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 ind ustrial 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 t he 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 CO 2 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 t hat achieve 65 percent efficiency from EPA's proposed standards for new and modified and reconstructed uni ts. 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 t his in turn would result in significant energy savings and reduced GHG emissions.

Commenter 0267 stated that an exemption for highly efficie nt CHPs that achieve an overall efficiency level of 60 percent or more would be directionally helpful in both the new and modified/reconstruct rules.1

- 27 Commenter 0267 stated that the EPA should establish applicability criteria to exclude stationary combusti on 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 averag e basis."

C ommenter 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 ef fect 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 principl e 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 alternati ve 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 re strictions 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 sel l 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 the se units meet the applicability criteria

, they would be subject to the requirements in this final rule.



### 1.7 NON

- FOSSIL

- FIRED EGUS (E.G., BI OMASS)

Comment 1.7

- 1: Commenter 0247 stated that it would be arbitrary and capricious for EPA to regulate and treat these biogenic CO 2 e missions in the same manner as fossil fuel emissions before EPA has determined whether biogenic CO 2 emissions should be regulated as a pollutant under the Clean Air Act. The commenter mentioned Motor Vehicle Manufacturers Ass'n v. State1

- 28 Farm Mutual Automob ile 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. Seco nd, ''the agency must . . . articulate a satisfactory explanation for its action.'' Id. The commenter stated that EPA fails to provide adequate justification for treating biogenic CO 2 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 CO 2 emissions from an affected facility's compliance calculat ion.

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 t he 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 indicati ng 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 u njustified 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 sub category for biomass units with no associated emission standard. The
commenter believed that the EPA would need to develop data sufficient to support a CO 2 emission standard for non

- fossil

- fuel

- fired EGUs and then propose new regulations for public

commen t. 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 encoura ge 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 fa cilities 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 fact ors related to the carbon cycle (sequestered CO 2 ) 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 sma ll amounts of fossil fuels are often needed even in1

- 29 units that burn primarily biomass; commenter (0193) opposed these applicability provisions because the commenter believed these provisions create significant disincentives for adopting CHP technologies wh en 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 combus ting 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 CO 2 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 perc ent 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 applic ability 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 enti rely 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 M ercury and Air Toxics Standards rule for fossil fuel

- fired EGUs, where the hea t 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 f ired 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 f elt 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 CO 2 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 CO 2 , a pollutant subject to regulation, for purposes of the PSD and Title V permitting programs under the CAA

.

Commenter 0172 s tated that CO 2 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

an nual and perennial herbaceous vegetation is relatively ephemeral, and reductions in these1

- 30 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 ove r 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 p olicy on biogenic CO 2 emissions, they urged EPA to exclude biogenic CO 2 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 unt il 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 b iomass 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 CO 2 emissions until it develops a final policy to address biogenic CO 2 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 CO 2 e. (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 scien tific 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 grow th of biomass in the United States is exceeding the amount harvested, biogenic CO 2 emissions from all types of biomass

- derived fuels do not contribute to atmospheric carbon levels unlike fossil fuel emissions.

Commenter 0262 stated that biogenic CO 2 emission do es not increase atmospheric CO 2 concentrations. The commenter noted t he scientific principles of the forest carbon cycle are well understood and uncontroversial. The commenter stated w ood products, including biomass combusted for energy, are in tertwined with the natural forest carbon cycle and their production and use are compatible with CO 2 reduction strategies.

Commenter 0149 stated that the EPA should not subject limited

- use

- oil

- based units or Biomass units to regulation under CAA section 1 11(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" approach1

- 31 would be arbitrary and capricious because it imposes no emissions st andard 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 uni ts. As addressed in the commenter's Section 111(b) Comments, the Clean Air Act requires numeric performance standards for biomass

burning power plants, which tend to be extremely carbon

- intensive. The commenter stated however, that section 111 does not per mit 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 f or 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 disagree d , however, that new applicability methodologies are necessary to ensure continu ous 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 consider ed existing units for 111(d) purposes.



### 1.8 INTEGRATED AND CO

- LO CATED NON

- EMITTING ENERGY GENERATION EQUIPMENT

Comment 1.8

- 1: Commenter 0152, 0157, 0165, 0171 , 019 7, 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 w ords, 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 n on

- 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 sta ted
t herefore, 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

- gr oss ) 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 commenter1

- 32 stated that the EPA has also provided no b oundaries 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 inclusio n 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; u nits 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 believe d , 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

un its, 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: Commenter s 0150, 0192, 0214, 0215 stated that EPA should adopt a single complianc e 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 e quivalent to the pe riod 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

-1

- 33 month calendar year compliance period for 111(b) would make t he 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 complianc e.

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 yea r 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 sever ely 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 0 176 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 c an 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 excursion s. The commenter stated, however, that this alternative should not be coupled with more stringent regulations.1

- 34 Commenter 0156 stated that the performance standard should reflect that, even for the most efficient units, heat rate efficiency degrades over t ime, 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 perfo rmance standard should reflect reasonable maintenance schedules.

Response 1.9

- 1: The emission standards in this final rule are based on 12

- operat i ng month
averages. See section IV.C of the NSPS preamble for discussion of the compliance period for

new , modified, and recons tructed 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 i nstead, 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
app licability 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 pro poses 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 sec tion 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 emissio ns 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 re ported 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 t o 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 averag e, 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.1

- 35 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 preamb le 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 ru le 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 MALFUN CTION

Comment 1.10

- 1: Commenter 0131 s tated that they agreed with the proposed exclusion of malfunctions from the compliance calculations. However, the commenter strongly disagree d that startups and shutdowns are "predictable and routine" and state d that the unpredictable components of energy pricing make periods of startup and shutdown uncertain. The commenter

recomm ended 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 comme nter believed that the EPA should n o t 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 existi ng regulations. The commenter stated that EPA's assumptions that startups and shutdowns are predictable, and thus CO 2 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 stan dards 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 cal endar 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.1

- 36 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
commente r 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 sma ll 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 02 60 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 fa ilures that result in periods of higher CO 2 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 commen ter note d , the courts have already held that promising enforcement discretion is not a substitute for setting achievable standards in the first place. The commenter request ed that the EPA withdraw the Proposed R ule until EPA has properly assessed whether t he 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 Implementatio n 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 d o in the January 2014 proposal. "

Commenter 0203 stated that since EPA did n o t consider SSM events when determining the standard, it is unfair and poor engineering practice to impose these standards during these events.1

- 37 The commenter also stated, however, th at 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 stea dy 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 CO 2 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 v iolations. The commenter stated n either 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 t hat 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 deg ree 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 asse rting 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. T he commenter stated t hose 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 agree d that the EPA is not required to factor malfunctions into its emission standard.1

- 38 Commenter 0201, 0158 stated that EPA must account for malfunctions in establishing emission standards. The commenter stated i f the standard is to be achieved at all times, the standard must contemplate periods of malfunction, as well as periods of startup and shutdown.

Commen ter 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 a nd 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 h as 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, leadi ng 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 perio ds. 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 malfuncti on 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

m alfunctions 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 brin g ing in enforcement action nor the exercise of discretion in imposing penalties is an adequate substitute for promulgating an achievable standard.

Commenter 0178 stated that i t is impossible to trace any particular environmental impact resulting from climate change to any particular CO 2 em ission source, especially since the emissions that could occur during a period of malfunction are miniscule in comparison to global CO 2 emissions. The commenter stated a s a result, it is impossible to "minimize" any such unknown impacts that may result dur ing a period of malfunction that causes excess CO 2 emissions. Because this factor does not make sense in the context of CO 2 emissions, commenter urge d 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 reference d the Boiler NESHAP for Major Sources as an example of EPA crea ting work practice standards during startup and shutdown periods.1

- 39 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 f or 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 includ e periods of startup and shutdown in the compliance calculation as periods of partial load. Commenter
urge d EPA not to include periods of startup and shutdown as periods of partial load in the calculation of compliance wi th the standard.

Response 1.10

- 2: Work practice sta ndards 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 i s 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 potential ly reduce reliance on natural gas combustion in the future, but the commenter believe d 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 i s 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 an d 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 thi s 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 wil l 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 determin e which units may potentially modify or
reconstruct. The commenter stated t he data was compiled from the EPA Clean Air Markets Division (CAMD) CEMS program. The commenter stated that the consulting firm "created a

new CO 2 emissions database that contained annual average emissions data for all coal

- fired units for the period 2003

- 2012". The commenter noted that a ll hours for which data were missing were1

- 40 excluded from the database, as the algorithms used to replace missing d ata err on the high side, creating an inflated record of emission. The commenter indicated the firm recorded the following data about each plant:

• Average CO 2 emission rate (lb/MWh(g)) based on hourly values

• Average CO 2 emission rate (lb/MWh(g)) based on an nual total CO 2 mass emissions and gross generation

• Average CO 2 emission rate (lb/MWh(g)) based on annual total CO 2 mass emissions and

• net generation

• Total CO 2 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 r eporting errors that resulted in anomalous CO 2 emissions rates in the EPA database. The commenter indicated t he 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 report ing bias due to apportionment.

(ALSO LATE) Commenter 0297 submitted a separate do cument analyzing the above information in combination with a second database. The commenter indicated t his report updates the achievability analysis for modified units by ca lculating estimated emission limits under the Proposed Rule using two alternative sets of CO 2 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.