5-1

Chapter 5

Applicability to New EGUs, IGCC, and CTs

Contents

5.1 New EGUs, IGCC, and CTs................................................................................................ 2

5.2 Prospective Applicability Criterion - Intended Purpose .................................................... 23

5.3 Retrospective Applicability Criteria - General .................................................................. 24

5.4 One-third Sales Criterion ................................................................................................... 27

5.5 Integrated Equipment......................................................................................................... 44

5.6 Biomass Fuels and the Ten Percent or Less Fossil Fuel Threshold................................... 49

5.7 Codified Rule Under Subpart TTTT and KKKK, and Applicability for Subpart KKKK 

Units ............................................................................................................................................ 55
5-2

5.1 NEW EGUS, IGCC, AND CTS

Comment 5.1-1: Commenters (8995, 10869) supported the overall applicability approach 

proposed by the EPA, and commenter 10869 found that the proposal included commonsense 

exclusions that are fair and do not undermine the overall integrity of the standards.

Commenter (10103) stated that they generally support the proposed requirements for

subcategories of new sources of fossil fuel-fired EGUs. The commenter agreed that electric 

power companies will most likely choose to build new EGUs that conform to the regulatory

requirements of this proposal because of existing and expected market conditions. 

Commenter (10098) opposed the competing alternative applicability provisions presented in the 

proposed rule text and preamble. This commenter stated that the EPA had proposed this Section 

111 standard prematurely, and the commenter believed the standard is counterproductive in the 

context of an NSPS rulemaking because the applicability date of NSPS standards is established 

as the date of proposal. However, this commenter believed, given all of the competing provisions 

in the proposal, it is impossible to know whether certain EGU projects will meet the various 

applicability criteria considered in the proposal package, such as whether applicability will be 

based on gross or net output or whether the applicability threshold will be a 33 or 40 percent 

sales criterion. Commenter 10098 believed that such competing alternatives should be publicly

vetted through an advanced notice of proposed rulemaking rather than in an action that sets the 

applicability date.

Commenter (8937) stated that the applicability date for the proposed rule was not clearly

indicated in the federal register and requested that the EPA clarify the applicability date as soon 

as possible.

Commenter 9499 stated that EGUs that commence construction within 12 months of the

effective date of the proposed rule or units for which permit applications have already been filed 

should be exempt from the EPA's proposed rule because the commenter believed that it is not 

equitable to adopt new regulations that become effective in a time frame that does not allow 

generation owners time to adapt long range plans to emergent requirements. 

Response 5.1-1: The EPA appreciates the support of those who favored the proposed

applicability approach, but the EPA has decided to finalize a variation of the broad applicability

approach on which we sought comment instead. In regards to the applicability date, the Clean 

Air Act requires compliance as of the date that the proposal is published in the Federal Register. 

This approach limits the ability of developers to commence construction between the proposal 

and the final rule simple to avoid complying with the proposed requirements. The applicability

date for newly constructed affect sources is January 8, 2014, while the applicability date for 

modified and reconstructed affected sources is June 18, 2014.

Comment 5.1-2: Commenter 9591 pointed out the close relationship of the standard for new 

sources to the subsequent guidelines for existing sources. Commenter 9591 pointed out the CAA 

section 111(d)(1)(A)(ii) requirement that applicability criteria for new source performance 
5-3

standards (NSPS) must be congruent to applicability criteria for existing source performance 

guidelines (ESPG). This commenter emphasized that section 111(d)(1)(A)(ii) requires the 

Administrator to prescribe ESPG with applicability provisions that mirror the applicability

provisions of the precedent NSPS. The commenter paraphrased the associated criteria as follows 

(emphasis added): Section 111(d) provides that the Administrator "shall prescribe regulations 

which establish a procedure ... under which each State shall submit to the Administrator a plan 

which (A) establishes standards of performance for any existing source for any pollutant ... to 

which a standard of performance under this section would apply if such existing sources were a 

new source." Commenter 9591 believed that the underlined portion of section 111(d) requires 

that the EPA consider the subsequent rulemaking for ESPG when finalizing the proposed NSPS 

applicability scope because the applicability criteria for the ESPG must mirror the applicability

criteria promulgated for the NSPS.

Commenter (9514) expressed concerns that the proposed applicability exemptions may be 

problematic in the context of the agency's pending 111(d) rule for existing power plants; since 

the NSPS are a predicate for regulating existing sources under section 111, the commenter 

believed that broader coverage under the NSPS will clarify which units will be included under 

the section 111(d) standards.

Response 5.1-2: The 111(b) applicability in this final rule was set considering practical 

implementations issues for both 111(b) and 111(d). Specifically, we are not finalizing 

applicability criteria based on actual operating conditions so that units cannot switch in and out 

of applicability. We also not that the applicability provisions of 111(b) and 111(d) do not need to 

be identical so long as all affected existing sources under 111(d) would be affected sources under 

111(b) if they were new sources.

Comment 5.1-3: Commenter 9514 recommended (with a few exceptions) that whether or 

not new source standards will apply to a particular unit should be determined based upon the 

same applicability provisions now in place for criteria pollutants [it was not clear which of the 

commenter's exceptions were associated with this recommendation].

Commenter (9514) generally opposed the proposed series of applicability provisions for steam 

generating units and stated that the agency must retain the current definitions used for

applicability under subparts Da, Db and Dc. Additionally, the commenter stated, the EPA should 

close off loopholes that exist in both the current regulations and proposed rules and apply the 

standards to all EGUs that supply or were constructed for the purpose of supplying any 

electricity for sale to the grid. The commenter is opposed to the proposed series of applicability

criteria joined by "ands" because, as proposed, the commenter believed these applicability

provisions compose significant loopholes.

Two commenters (9666 and 10023) supported the exemption of small combustion turbines 

below 73 MW (250 MMBtu/h).

Commenters (5605, 9406, 9513, 9514, 9771, 9591) generally supported inclusion of the 

technologies listed in the initial applicability statement of the proposed rule, but recommended 

that applicability should be more generalized to include "all fossil fuel-fired power plants" 

because the commenters believed that doing so may simplify development of future frameworks 
5-4

for cost-effective carbon reductions from existing units, such as frameworks based on systemwide approaches. 

Commenter (9406) stated that numerical limitations should apply to all EGUs that supply

electricity to the grid, including small EGUs, oil-fired combustion turbines, and simple cycle 

combustion turbines because excluding some EGUs undercuts efforts to reduce GHG emissions 

and creates an unbalanced playing field in the market, and because NSPS are technically feasible 

for the EGUs that EPA proposes to exclude and inclusion will not threaten reliability. 

Commenter 9406 also stated that regulating simple cycle turbines under the section 111(b) rule 

may help with implementation of forthcoming section 111(d) guidelines for existing EGUs, and 

the commenter indicated that states participating in the Regional Greenhouse Gas Initiative 

already regulate CO2 emissions from simple cycle turbines in that market-based allowance 

program, and the commenter suggested that including all simple cycle turbines in federal 

regulatory programs may reduce administrative and regulatory burdens implementing federal 

rules through existing section 110 state programs. Commenter 9406 also recommended that 

rather than exempting peaking units, at a minimum, simple cycle peaking units, should be 

subject to work practice standards such as operating safely and with good air pollution control 

practices, including GHG monitoring and reporting requirements.

Commenter (10025) stated that the rule must apply to all carbon emitting power plants and must 

be strengthened. The commenter stated that the rule must apply to both future, modified, and 

existing power plants, placing limits on carbon emissions in line with the trajectory needed to 

bring atmospheric carbon concentration back to 350 ppm by 2100. 

Response 5.1-3: The final applicability criteria cover some of the source suggested by the 

commenters, including oil-fired units and simple cycle combustion turbines, but do not include 

others, such as industrial units and very small (i.e., less than 25 MW) EGUs. For the EPA’s 

complete rationale for covering certain sources by excluding others from the final applicability 

criteria, see the preamble to the final rule.

Comment 5.1-4: In conjunction with the recommendation for a more generalized initial 

applicability statement, commenters (9513, 9514, 9771) recommended that the EPA use CAA 

section 111(b)(2) authority to develop appropriate subcategories of EGUs.

Commenters 10095 stated that the EPA should use section 111(b)(2) authority to subcategorize 

steam boilers (by fuel type) and IGCC units. The commenter cited the EPA's response to 

comments for amendments to Subparts D and Da in 2011 where the EPA held that standards of 

performance should not be set at levels that preclude the construction of certain affected sources 

within a category or subcategory. Commenter 10095 goes on to assert that the EPA's failure to 

subcategorize in the proposal is inconsistent with previous rulemakings, and the commenter 

believed this failure to subcategorize is arbitrary.

Commenter (4814) stated that new power plant regulations should be set separately for coal 

power plants and natural gas generating units. The commenter stated that these emission level 

standards should be based on best system of emission reductions adequately demonstrated for 

power plants that are operating commercially in the U.S.
5-5

Commenter (9661) stated that a separate and achievable standard for coal-fired electric 

generating units is necessary. The commenter stated that EPA's proposed NSPS for new coal 

based units should not require carbon capture and sequestration. The commenter stated that EPA 

must establish separate standards even if market trends and modeling forecasts suggest that there 

will be no new coal units built in the foreseeable future. 

Commenter (8024) stated that they agree with EPA's decision to provide separate emission 

standards for coal and natural gas combined-cycle units. The commenter stated that the agency's 

previous proposal to combine these two sources into one category (77 RF 22392) failed to 

recognize the fundamental technical, economic, and engineering differences between these two 

very different methods of electrical generation. 

Commenter (9649) stated that setting a single standard at the level achieved by NGCC units 

would have, for all practical purposes, eliminated new coal-fired units as a viable generation 

option due to the high costs and infeasibility of CCS needed to meet that standard, and would 

have almost certainly limited any new coal-fired units to geographic areas where 

CSS could feasibly be used. 

Response 5.1-4: This final rule subcategorizes steam generating units and IGCC units separately

from combustion turbines. The EPA has concluded that subcategorization by coal type is not 

necessary for this final rule. See Sections III.C and IV.A of the preamble for a discussion of the 

applicability criteria for steam generating units and Section IX.A of the preamble for a 

discussion of the applicability criteria for combustion turbines.

Comment 5.1-5: Commenters (7994, 8918, 8937, 8952, 9001, 9034, 9194, 9407, 9425, 9426, 

9428, 9499, 9564, 9592, 9595, 9596, 9597, 9601, 9602, 9665, 9666, 9667, 9678, 9723, 9771, 

9767, 9769, 9772, 9780, 10024, 10030, 10048, 10052, 10095,10097, 10098, 10100, 10102, 

10238, 10358, 10390, 10393, 10395, 10466, 10500, 10520, 10618, 10788, 10870, 10950, 10952) 

opposed in part the EPA's proposed selection of technologies to be covered by the standard and 

provided recommendations for amendments to the proposal. These commenters opposed the 

general reference to stationary combustion turbines and recommended that the final rule 

completely exempt simple cycle units from the standard, because future capacity factors for these 

units may increase above historic levels to support the rapid growth of renewable generating 

assets and more fundamentally, because simple cycle units serve a different purpose than NGCC 

units, a purpose that precludes current simple cycle technologies from achieving efficiencies 

equivalent to NGCC technologies. Commenter 10095 cited extensively from the rational for 

exempting simple cycle turbines in the preamble to EPA's 2012 proposal, and stated that simple 

cycle turbines must be treated differently than NGCCs under section 111(b) proceedings. 

Commenter 9499 stated that SC turbines should not be included in this rule.

Commenters (8952, 8973, 9425, 9426, 9499, 9665, 9666, 9678, 9723, 9780, 10052, 10095, 

10098, 10100) also opposed inclusion of simple cycle turbines because these assets typically 

have the shortest construction schedules and are viable options for filling capacity gaps while 

lengthy base load transmission and generating projects are permitted and constructed. These 

commenters believed that the EPA has a reasonable basis (and section 111(b)(2) authority) to 

explicitly exempt simple cycle (SC) turbines in order to provide system operators with full use of 

the unique capabilities of SC units to resolve reliability emergencies within minutes while also 
5-6

preserving the capabilities of SC units to replace capacity lost when base load units are 

recovering from lengthy forced outages. 

Commenters (9426, and 10052) disagreed with the EPA's suggestion that the proposed 

applicability criteria are necessary to avoid a circumstance where utilities increase use of simple 

cycle units to avoid the NSPS because the economics of simple-cycle combustion turbines 

requires their use only on an as-needed basis and it is unlikely that they will be widely-deployed 

in lieu of combined cycle combustion turbines. These commenters believed a categorical 

exemption for simple cycle units is necessary to maintain grid reliability. 

Commenters (6870, 7994, 8944, 8952, 9001, 9407, 9428, 9591, 9595, 9596, 9601, 9602, 9654, 

9665, 9666, 9667, 9723, 9767, 9769, 9772, 9773, 8911, 9194, 9381, 9426, 9780, 10024, 10030, 

10034, 10048, 10086, 10095, 10238, 10239, 10358, 10387, 10390, 10393 10395,10466, 10520, 

10606, 10660, 10788, 10870, 10950 and 10052) supported a categorical exemption for simple 

cycle turbines. 

Commenter (10395) stated that the proposed NSPS can only be met by units having thermal 

efficiencies associated with natural gas combined cycle (NGCC) EGU CTs. Commenter 10395 

stated SC CTs cannot meet the proposed standards. The commenter also stated that since their 

dispatch to maintain grid reliability may require operation exceeding the 219,000 MWh annual 

cut-off, SC CTs should be exempt from this rulemaking. Additionally, the commenter stated that 

the proposed limitation on SC CT annual operating hours presents a bias in favor of industrial 

sources that do not face similar simple-cycle CT operating restrictions. In summary, the 

commenter stated that EPA should exclude SC CTs from Subpart KKKK at this time, and wait 

until the rules are implemented and EPA is able to gather operational data over several years 

regarding how the new and evolving generation mixes on the grid will work before hamstringing 

SC CT options. The commenter stated that it makes no sense to include SC CTs under 40 C.F.R. 

Subpart KKKK, and limit them to only one-third of their capacity. 

Commenter (10052) stated that due to the manner in which utilities utilize simple cycle units, it 

is unlikely that a categorical exclusion will materially change utility reliance on simple cycle 

units. The commenter believed that a categorical exclusion is also preferable because it will 

simply avoid the issue of potentially compromising reliability or decreasing utilities' ability to 

integrate renewable resources. The commenter stated that if EPA will not exempt simple cycle 

turbines, they should consider a different standard that is operationally specific to simple cycle 

turbines.

Commenter (9426) stated that based on EPA's position that meeting the proposed 1,000 lb 

CO2/MWh standard will not impose any additional costs on new NGCC units, there would be no 

adverse economic impacts on new NGCC units and therefore no economic incentive to either 

build simple-cycle turbines instead of NGCC units or to operate new simple-cycle turbines more 

than would otherwise make economic sense if the EPA were to provide an exclusion. The 

commenter believed that any claims or concerns that an exclusion for simple-cycle turbines 

would create an opportunity to evade the standard and could thereby increase GHG emissions are 

groundless. 
5-7

Commenter (9780) believed that excluding new stationary simple-cycle CTs is appropriate 

because these units provide important grid services that facilitate renewables integration and 

support reliability. The commenter stated that an exemption will allow maximum operating 

flexibility for these units to perform these functions. The commenter also stated that the 

proposed exemption would only apply to GHG performance standards and not to any other 

emissions limits that may be included in a unit's title V operating permit.

Commenter (9667) stated that exemption for simple cycle units is critical because limiting the 

exclusion from the Rule to units that supply less than 2919 hours to the grid is insufficient to 

cover many potential operating scenarios for simple cycle units. 

Commenters (7994, 8952, 9426, 9428, 9665, 9666, 9678, 10052, 10086, 10395, 10466) also 

opposed inclusion of simple cycle turbines in the initial applicability criteria because many

simple cycle turbines cannot achieve the standard, and commenters (8952, 9665) indicated that 

including simple cycle turbines will benefit other EGU technologies that are not subject to the 

standard (such as diesel engines) that have higher emissions than simple cycle turbines. 

Commenter 8952 stated that, theoretically, no commercially available simple cycle gas turbine is 

able to achieve 1,100 lb/MWh when operating under the real world highly flexible operation 

demanded of simple cycle turbines.

Commenter 9678 stated that a specific exemption from these standards would not induce 

operators to install simple cycle units where NGCC is otherwise economically or practically

preferable. Commenter 9678 stated simple cycle turbines and NGCC serve different roles within 

an electricity market. Commenters 10392, 10876 stated that EPA would be 

requiring burdensome recordkeeping requirements with no appreciable emission reduction 

benefits. 

Commenter 9665 stated that simple cycle units should be excluded because their inclusion could 

adversely affect sales of larger, more efficient simple cycle units. The commenter also stated that 

if EPA does not exclude simple cycle units, it should revise the rule's applicability requirements 

and establish simple-cycle specific standards. The commenter also stated that the proposed rule 

should include language clarifying that the final standards for NGCC do not apply to PSD 

permits for simple cycle units. 

Commenter 9407 stated that any limitations on SCCT use should be based on need and purpose 

as represented in operating permits, and not on an NSPS with hard numerical limitations on 

utilization. 

Commenter 10660 stated that if EPA proceeds to include simple cycle turbines under the NSPS, 

a separate emission limit would need to be established to satisfy section 111's requirements for a 

standard that has been demonstrated to be achievable in practice. The commenter stated that

EPA's limits do not meet those statutory criteria under anything but the most optimum load and 

ISO conditions, and, as noted above, simple cycle turbines often function as peaking units and as 

back-up power units.

Commenter 9666, 10095 noted that EPA has stated that the fuel efficiency of simple cycle 

turbines is about 29 percent while NGCC units operate at about 48 percent efficiency. 70 Fed. 
5-8

Reg. at 8319. Thus, commenters stated it should be no surprise that simple cycle turbines cannot 

meet either 1,000 or 1,100 lb CO2/MWh on a 12-operating-month rolling average basis because 

simple cycle combustion technology is very different than combined cycle technology. 

Commenter 9666 stated that if simple cycle turbines were to be subject to the proposed NSPS, 

they could not meet the limit, would be unable to operate, and system reliability would be 

jeopardized. If EPA wants to subject high capacity factor simple cycle turbines to a GHG NSPS, 

the commenter stated the EPA should create a separate subcategory, determine an appropriate 

BSER, analyze emissions from these machines, consider all section 111(b) factors, and propose a 

limit that is achievable.

Commenter 8952 stated that in the absence of a full exemption for simple cycle gas turbines, the 

commenter believed the EPA should provide incentives for simple cycle machines to drive to 

higher efficiencies and reduced levels of CO2 at peak power conditions.

Commenters (8952, 9425, 9426, 9665) believed that the EPA's analysis of historic capacity

factors for simple cycle units is inappropriate for determining if simple cycle units will be 

subject to the standard in the future because these commenters believe that future growth of 

renewable generation capacity will require proportionate growth in simple cycle capacity 

because simple cycle technology is the most efficient and reliable technology that can be 

dispatched in minutes to complement use if intermittent renewable resources. Commenters 

(9665, 9666) disagreed with the EPA's premise that the proposal will affect an inconsequential 

number of simple cycle combustion turbines, and commenter 9665 cited an analysis of recent air 

permits issued in states with progressive renewable portfolio standards (RPS) to support the 

claim that "far more than one percent of new simple cycle turbines will be affected by the 

proposed rule." Commenters (8952, 9665) also believed that future turbine packages ordered by 

system operators may not be dispatched in a manner that allows operation at peak efficiency, but 

rather that they may be dispatched to maximize how quickly they can follow load and changes in 

energy supply.

Commenter 9425 stated that in some circumstances, simple cycle turbines are used to support the 

integration of renewable resources into the grid and may operate more frequently. The

commenter noted that simple cycle units that accommodate the increased use of renewable 

generation should not be penalized by emissions standards that fail to recognize that system 

emissions are decreasing, even though unit emissions might increase. Commenter (9425, 9780)

also stated that if EPA retains the one-third sales test approach as opposed to explicitly

exempting simple cycle CTs, it must address a range of compliance issues that weren't addressed 

in the proposal. Commenter 9425 stated that first, EPA must clarify that the exemption criteria 

for CTs applies on a per unit basis and not at the facility level. Second, Commenter 9425 stated, 

as EPA notes, there are implementation issues that arise when a unit that was not built to achieve 

a standard becomes subject to that standard at some point in the future. 

Commenter 10952 provided a case study provided by Golden Spread Electric Cooperative Inc. 

that illustrates how and why SCCTs operating as required and unconstrained by operational 

limits like those proposed can play a vital role in supporting renewable generation and

minimizing CO2 emissions. The commenter also provided two detailed scenarios in which 

SCCTs could be used to support renewables and minimize CO2 emissions. 
5-9

Commenter (8957), a preconstruction permitting authority, concurred with the EPA's analysis 

that the majority of simple-cycle turbines will be excluded based on proposed applicability

requirements, and stated that if they are not excluded under the proposed applicability

provisions, it is reasonable to apply the proposed standard. 

Commenters (9665, 9771, 10660) opposed the proposed applicability provisions for combustion 

turbines in conjunction with the proposed emission standards derived from NGCC performance 

because this combination of applicability and compliance provisions is incompatible with 

reliability plans in California and other states with progressive Renewable Portfolio Standards 

(RPS). These commenters presented the generating load profile for a typical day in California

with the projected ramp rate needed to accommodate variable contributions from wind and 

solar assets; the load profile indicated that during the daytime wind and solar power can replace 

fossil fuels but in the late afternoon and evening the ISO must quickly dispatch fossil fuels to 

make up for falling solar generation, with a required ramp up of approximately 13,000 MW in 

just a three or four hour period. Commenter 9665 also provided a quote from a California ISO 

publication from 2013 that stated, "To ensure reliability under changing grid conditions, the ISO 

needs resources with ramping flexibility and the ability to start and stop multiple times per day. 

To ensure supply and demand match at all times, controllable resources will need the flexibility

to change output levels and start and stop as dictated by real-time grid conditions." Based on this 

quote from the California ISO publication, Commenter 9665 asserted that larger, efficient, 

simple cycle units are the most appropriate way to deal with the significant and rapid power 

increases required to support use of renewable resources as proven by recent California

purchases of aero derivative simple cycle turbines that can achieve full capacity within 10 

minutes. These commenters described typical operations (of the simple cycle units that support 

renewables) as prolonged periods of running at low inefficient loads ready to respond to 

fluctuating wind or solar conditions followed by several hours at increasing loads as wind and 

solar decline followed by sustained periods at full load (during periods of calm winds and 

darkness) to assume the load previously carried by wind and solar assets. These commenters 

stated that simple cycle units performing this routine duty cycle may be required to operate 

above applicability thresholds, but that such duty cycles preclude compliance with the proposed 

standard by simple cycle units.

Commenter 9771 stated that the size-based standards do not fully acknowledge the changes now 

occurring in the power sector, which may lead to shifts in how natural gas-fired EGUs are 

operated. The commenter stated that accordingly, EPA should carefully consider how its

standards will interact with a changing power grid to ensure that the standards support this 

renewable integration, while continuing to set rigorous standards for EGUs that continue to 

operate in more traditional applications. The commenter strongly urged EPA to consider further 

subcategorization based on an EGU's operational profile (including, for instance, baseload, 

conventional load-following, fast-starting/ramping, and peaking) in order to ensure the 

developed standards support further renewable integration.

Commenter (9771), a permitting authority in a state with rapidly increasing use of renewable 

resources, stated that emerging demand for flexible resources reflects the increasing importance 

of generating assets with significantly different emission characteristics compared to historically 

deployed resources. Commenter 9771 stated that the EPA should recognize these changes and 

provide regulation in a deliberate and targeted manner for EGUs of all the operating types 
5-10

necessary to support expanded use of renewable resources within a broader strategy for 

significant reductions from the electricity sector.

Commenter (8911) stated that the modern role of simple cycle generation can now be safely 

limited to non-spinning reserve capacity. And even that role applies only rarely when a grid has 

such a glut of low cost energy that it is not economical for the non-spinning reserve capacity to 

be supplied by new combined cycle plants. The commenter cited data from California in this 

portion of their comment. 

Commenter (10390) stated that their experience with the Montana Power Stations demonstrates 

that SC turbines can be needed and should be allowed to operate without capacity limitations. 

Commenter (9769) stated that the proposed applicability criterion approach for simple cycle 

combustion turbines does not appear to consider regulating plants using simple cycle technology. 

The commenter stated that increasing the applicability criterion or the CO2 standard of

performance for units with a heat input less than or equal to 850 MMbtu/h would not provide the 

necessary flexibility and regulatory certainty for new regulatory plants. 

Commenter (10030) stated that EPA recognizes that economics dictate not using SCCTs where 

CCCTs are otherwise appropriate. The commenter stated that rather than regulating SSCTs based 

upon unsupported concerns, EPA should defer regulating such units for GHG emissions at this 

time.

Commenter (8952) was concerned that the NSPS levels may be misinterpreted and assumed to 

be BACT for all gas turbines, including large simple cycle projects. The commenter stated such a 

misinterpretation would effectively ban simple cycle gas turbines. The commenter requested that 

EPA include specific language to prevent an unintended adverse impact on simple cycle gas 

turbines. 

Commenter (9514) stated that setting a carbon pollution standard is not only essential for

ensuring high efficiency and low emissions from new simple cycle CTs, but could also help 

ensure that EPA's forthcoming emission guidelines for existing EGUs comprehensively address 

carbon pollution from the power sector. The commenter stated that the exclusion of peaking

units from the NSPS for CO2 pollution from new EGUs could leave uncertainty as to whether 

such units would be subject to section 111(d) standards. The commenter recommended that 

instead, EPA should promulgate a three-tiered set of performance standards under which peaking 

units (i.e., those operating fewer than 1,200 hours annually) - whether CT or CCGT - would be 

limited to 1,100 lbs CO2/MWh.

Commenter 10119 stated that EPA's proposal to exclude lower capacity and simple cycle gas

turbines from the standard is unsupported. The commenter stated that the proposed rule does not 

adequately explain this exemption. The commenter stated that EPA cannot rely on National Lime 

Association in support of a decision not to set a standard for simple cycle plants. See Nat’l Lime 

Ass’n, 627 F.2d at 426 n.28. The commenter felt that EPA has no evidence that all new natural 

gas plants will be NGCC plants; indeed, the evidence in EPA's possession shows not only that 

simple-cycle plants will continue to be needed, but also that this part of the power sector is 

anticipated to grow dramatically. Ultimately, therefore, EPA has failed to provide a rational basis 
5-11

or adequate explanation for its decision not to establish a standard for simple cycle plants. The 

commenter stated that to the extent EPA intended its applicability standard to exempt simple 

cycle facilities, its decision comes with significant collateral damage. The applicability standard 

could also exclude a large number of NGCC plants. 

Commenter 10681 stated that the proposed rule language under part 60, subpart KKKK does not 

clearly indicate how peaking units would be affected by the proposed rule and requested that the 

EPA clearly address peaking units in the final rule; the commenter recommended that the EPA 

establish a definition for peaking unit based on a maximum number of operating hours per year.

Commenter (9515) opposed provisions effectively exempting oil-fired and peaking units, and 

stated that the EPA did not provide sufficient justification for these exemptions; commenter 9515 

recognized the EPA's discretion to create exemptions under section 111, but stated that this 

discretion is limited by a standard of reasonableness and subject to judicial review. The 

commenter concluded that the EPA should more fully explain its rationale for exempting oilfired and peaking units in order to preclude legal actions alleging that these exemptions are 

arbitrary and capricious.

Commenter 9515 stated that EPA should more fully explain its exemption for oil-fired units and 

discuss the costs and benefits of that exemption. EPA should also examine the costs and benefits 

of regulatory alternatives to exemption, such as establishing a separate, less stringent 

performance standard for new oil-fired units.

Commenters (9425, 9770, 10024) supported EPA's proposed exemption for combustion turbine 

units that run exclusively on oil. The commenter stated that the lack of a robust database for new 

oil-fired units with which to evaluate CO2 emissions does not support the development of an 

NSPS for oil-fired units. Commenters (9425, 9770, 10024, 10100, 10393) supported 

exemption of combustion turbine units that run exclusively on oil. Commenter 9425 did not 

believe there is a robust database for new oil-fired units to support development of an NSPS for 

oil-fired combustion turbines.

Commenter (9515) stated that EPA should articulate robust justifications for exempting oil-fired 

and peak-demand units. The commenter stated that EPA's proposed performance standards do 

not apply to oil-fired generating units or to units that sell less than one-third of their potential 

electric output to the grid (i.e., peak-demand units). The commenter believed that EPA has 

discretion to create exemptions when promulgating performance standards under Section 111 of 

the Clean Air Act, they felt that this discretion is limited by a standard of reasonableness and 

subject to judicial review. Accordingly, the commenter stated that EPA should more fully 

explain its rationale for exempting oil-fired and peak-demand units.

Commenter (9515) stated that the EPA should more fully explain why oil-fired units are exempt. 

The commenter believed that unavailability of natural gas at certain sites does not preclude the 

EPA from establishing a standard of performance specific to oil-fired units; the commenter 

believed that the final rule should more fully explain the rationale for oil-fired units with a costs 

and benefits analysis.
5-12

Response 5.1-5: Based on practical implementation concerns (e.g., not having units come in and 

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

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

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

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

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

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

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

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

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

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

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

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

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

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

applicability approach and final subcategories for combustion turbines.

Comment 5.1-6: Commenter (9661, 9780, 10520, 10100) stated that EPA should exempt simple 

cycle mode operations from combined cycle plants in consideration of compliance with the 

model. The commenter noted that as proposed, the entire combined cycle unit would be subject 

to the rule and emissions in both simple cycle and combined cycle mode would be included in 

compliance determinations. Commenter 10100 stated that combined cycle units often operate in 

simple cycle mode to provide peaking power and to ensure compliance with permit limits 

applicable to other criteria pollutants. 

Commenters (9426, 9471, 9592, 9596, 10100, 10500, 10520) recommended that the EPA should 

also exclude from applicability determinations operating periods when combined cycle units run 

in simple cycle mode such as during steam turbine maintenance activities. Commenter 9592 

stated that there are many operating situations that force combined cycle units to operate in 

simple cycle mode, and the commenter described a combined cycle unit at his facility with Title 

V operating permit limits that require the combined cycle unit to switch to simple cycle mode at 

intermediate loads in order to comply with applicable NOx standards. Commenter 9592 operates 

a small public power system that serves 80,000 customers, this commenter stated that there are 

times when combined cycle units must run in simple cycle mode due to malfunctions of steam 

cycle components, and the commenter indicated that this vulnerability is especially critical for 

smaller public power systems that do not have a large fleet of units to choose from; in these 

situations, the commenter asserted, operation in simple cycle mode may be required to meet 

reliability constraints. Commenter 8023, operator of the largest municipal utility in the U.S., 

provided similar comments regarding the growing challenges of providing reliable service on 

smaller transmission and distribution systems when generating units or transmission resources 

fall off-line unexpectedly. Commenter 8023 also indicated that the primary strategy for 

mitigating risks of outages on smaller systems is to increase the availability and utilization of 

fast-ramping, simple cycle gas-fired generators and to operate these flexible assets for sustained 

periods at partial loads with emission rates significantly higher than the proposed standard. 

Commenter 9425 stated that the final rule should include provisions for excluding from 

applicability atypical years of operations when a simple cycle unit is forced to run with a higher 

than normal capacity factor to ensure grid reliability. Commenter 9471 stated that the Clean Air 
5-13

Act does not require that all EGUs must operate for only base load purposes, and the commenter 

suggested changes to avoid the implication in the rule that all units must operate at base load 

conditions where they are most efficient: (1) the EPA should revise the final rule to allow NGCC 

units the use an 84-month averaging period without the associated requirement for CCS; this 

change would help mitigate the unavoidable higher emissions during startups and shutdowns; the 

commenter also recommended increasing the proposed standards.

Response 5.1-6: The EPA disagrees with the commenter that simple cycle operation for a 

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

does not set separate standards for simple cycle and NGCC units. Instead, the final rule sets 

separate standards for base load and non-base load units and distinguishes these subcategories 

based on the amount of electricity sold to the grid, derived from a unit’s nameplate design 

efficiency calculated as a percentage of potential electric output. The final base load unit

emission standard includes sufficient compliance margin to allow flexibility of NGCC operation,

including running in simple cycle mode. If a NGCC unit operates for significant periods in 

simple cycle mode, it will likely be subject to the non-base load unit emission standard. The nonbase load standard requires the use of clean fuels, and efficiency does not factor into compliance 

with the emission standard.

Comment 5.1-7: Commenter (9426, 9591, 9769) requested that EPA consider exempting 

ancillary services or regulation service from the final rule. The commenter stated that such an 

exemption would provide regulatory certainty for new units similar to DGGS, designed to 

support system reliability and further facilitate the integration of renewable resources.

Response 5.1-7: The final rule does not exempt ancillary services. Such an exemption is 

unnecessary because the sliding-scale approach and system emergency exemption provide 

adequate flexibility for non-base load units to support the integration of renewables. 

Comment 5.1-8: Commenter 9514 stated that the EPA should ensure that fast-start combined 

cycle units are subject to the standard. 

Commenter (9514) stated that EPA should also ensure that fast-start CCGTs are covered under 

the proposed NSPS. Commenter 9769 added that a particular class of fast-start generators 

referred to as "ancillary services" or "regulation services" should be expressly exempted because 

these units are required by reliability regulations and are integral to system reliability when 

integrating renewable resources. The commenter provided a definition for these types of units 

from a FERC Open Access Transmission Tariff.

Response 5.1-8: The final applicability criteria in this final rule do not distinguish between the 

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

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

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

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

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

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

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

adequate assurance that the final requirements will not result in reliability concerns.
5-14

Comment 5.1-9: Commenter 9780 stated that EPA must affirm that the reactivation of 

mothballed units would not subject such units to the CAA section 111(b) standards for new units. 

The commenter stated that depending on circumstances regarding reliability needs and market 

economics, there is a possibility that companies may reactivate units that have been essentially

"mothballed" or placed into cold storage. The commenter stated that reactivation of a dormant 

facility is not considered to be construction of a new source for section 111(b) purposes. The 

commenter stated that the EPA needs to clarify that if an EGU is not modified or reconstructed 

before restarting, the project does not trigger section 111(b), as long as the federal and state 

operating permits remain effective. 

Response 5.1-9: Applicability determinations are made on a case-by-case basis, so whether a 

reactivated mothballed unit could be considered subject to this NSPS will depend on a variety of 

factors, including how long the unit has been mothballed and whether the unit is engaging in 

upgrades that could be considered a modification or reconstruction.

Comment 5.1-10: Commenter 9406 stated that one exception to the preceding recommendation 

to establish numerical CO2 emission standards for simple cycle turbines is necessary: simple 

cycle units that trigger NSPS applicability when transferred from one facility to another facility; 

in those cases, the older unit may not be as efficient as a new unit, and the EPA should establish 

work practice standards rather than numerical emissions standards for such relocated units. 

Response 5.1-10: While applicability determinations are made on a case-by-case basis, moving 

an existing combustion turbine to a new location would generally not trigger the 111(b) 

requirements.

Comment 5.1-11: Commenters (10022, 10504) requested that the EPA exempt electric utilities 

operating in Alaska from applicability under the proposed rule. Commenter 10022 explained that 

the proposed rule would further increase the cost of electricity in Alaska where costs are already

one of the highest in the nation (18.33 cents/kWh in 2013). The commenter stated that natural 

gas is not readily available in Alaska and is not cost effective for all parts of Alaska. The 

commenter believed that unavailability of natural gas to interior Alaska and remote communities 

rebuts the EPA's justification for the proposed standard "based on the fact that inexpensive 

natural gas is readily available in the U.S. for power generation." The commenter stated that this 

generalization is not true for Alaska. The commenter described Alaska's reliance on coal-fired 

steam units as well as oil-fired combined cycle and oil-fired simple cycle turbines and stated that 

the cost of oil-fired generation continues to increase, placing financial stress on interior Alaska 

communities. The commenter also stated that owners of the refinery that provides the majority of 

the oil used for generation have announced closure of the refinery, leaving coal as the only viable 

fuel available for meeting the demand for electricity in interior Alaska. The commenter went on 

to describe how many of the generalizations used by the EPA to justify the proposed standard are 

not true for interior Alaska and the commenter added that requiring new coal-fired EGUs in 

Alaska to install and operate partial carbon capture and sequestration (CCS) has eliminated 

interior Alaska's most affordable power source. The commenter stated that the sale of captured 

CO2 for Enhanced Oil Recovery (EOR) is not viable for interior Alaska's coal-fired plants due to 

the lack of nearby oil or gas production activities. The commenter also provided a discussion of 

how providing an exemption from the proposed rule for Alaska could improve interior Alaska's 

air quality which is adversely impacted by winter inversions and wood-burning for home 
5-15

heating. The commenter also described how unique considerations are necessary for Alaska's 

electric system compared to the contiguous 48 states: Alaska is extremely remote, challenged 

with severe winter weather conditions, and constrained by limited infrastructure and support 

services. The commenter asserted that basic community services taken for granted elsewhere in 

the US are simply not available in most areas of Alaska. Utility operators have unparalleled 

challenges with transportation, logistics, staffing, equipment availability, and short construction 

seasons. The commenter also stated that Alaska's isolated electric grid systems are not in the 

same category as interconnected contiguous US electric systems, and access to fuel resources is 

limited and varies from location to location. The commenter believed that the GHG NSPS 

discriminates against communities that do not have access to natural gas because in those 

communities, businesses will not be able to afford to operate, families will be displaced, and 

community's financial health will deteriorate. Finally, the commenter asserted that impacting the 

reliability of Alaska's electric utility sector puts the safety of all Alaskans at risk because the 

most important job of Alaska electric utilities is to provide reliable electric service to our 

communities through the extreme cold, lengthy and dark winter months when reliable electric 

service is critical for life and safety. The commenter stated that unlike interconnected utilities in 

the contiguous US, Alaska's utilities do not have the option of relying on an integrated grid 

system for backup support.

Commenter (10672), an electric utility operator in a non-continental, island territory, requested

that the exemption for non-continental electric utility units be reintroduced into the final rule 

because the commenter believed that only a clear exemption for these islands will be sufficient to 

allow construction of new power plants since the only fuel available on such islands is oil and 

there are no opportunities for carbon sequestration.

Commenter 9194 commented that the Florida Keys should be included in the proposed rule’s 

definition of “non-Continental areas” of the U.S. and thereby excluded from the proposed new 

source standard, since pipeline-quality natural gas is not available in the Florida Keys and there 

are no plans to build a natural gas pipeline in this environmentally sensitive area.

Response 5.1-11: Combustion turbines without access to natural gas will not be subject to the 

requirements in this final rule. The achievability of the final requirements for coal-fired EGUs is 

discussed elsewhere in this RTC. 

Comment 5.1-12: Commenter (10100) also supported applying the standard to only CO2

emission from affected sources. 

Response 5.1-12: See Section III.G of the preamble for a discussion of which GHGs are 

covered in the final rule.

Comment 5.1-13: Commenter (10100) urged the EPA to also exclude coal refuse-fired units 

because, the commenter asserted, EGUs that burn over 75 percent coal refuse on an annual basis 

have no net GHG emissions in the long term since unused coal refuse piles are constantly 

burning due to their size and exposure to atmospheric oxygen.
5-16

Commenter (10100) urged EPA to exempt coal refuse-fired EGUs from the NSPS. The 

commenter stated that in the alternative, the commenter supported EPA's proposal to establish a 

subcategory for coal refuse-fired EGUs. The commenter cited 79 Fed. Reg. at 1496.

Response 5.1-13: The EPA is not finalizing an exemption for coal refuse-fired EGUs. The EPA 

notes that the industrial CHP exemption has been expanded, however, and new coal refuse-fired 

units are generally small enough that they could be designed as an industrial CHP unit. See 

Section III.E of the preamble for a discussion of the coal refuse issue.

Comment 5.1-14: Commenter (9514) opposed the "50 percent solid-derived fuel" applicability 

threshold for IGCC units because, the commenter believed, this proposed definition would allow 

an IGCC to obtain up to 50 percent of its heat input from coal without having to meet the 

emission limit reflecting the use of partial CCS, while a pulverized coal plant that combusts 10 

percent or more coal, would be covered by the partial CCS standard. Commenter 9514 also 

opposed the "50 percent solid-derived fuel" applicability threshold for IGCC units in conjunction 

with the 90 percent threshold for natural gas usage in combustion turbines because, the 

commenter believed, a CCGT that burned less than 50 percent syngas and 90 percent or less 

natural gas would escape regulation altogether, since it would qualify as neither an IGCC nor as 

a natural gas-fired CCGT. The commenter asserted that these exemptions would encompass 

plants whose fuel mix consisted of 45 percent syngas and 55 percent natural gas, or 85 percent 

natural gas and 15 percent oil. Commenter 9514 also expressed concerns that the proposed 90 

percent applicability threshold for use of natural gas in combustion turbines would not cover any 

CT that burned 90 percent or less natural gas regardless of its heat input from syngas. The 

commenter believed that IGCCs should be required to operate on an even footing with other 

steam EGUs that combust coal, and be subject to the same 10 percent test as other coal-fired 

plants; the commenter subsequently provided draft applicability provisions (for the 

EPA's consideration) to close these perceived applicability gaps.

Commenter 10030 stated that EPA should withdraw the Proposal relative to solid fuel fired units. 

Commenter 10030 stated regulation of GHG emissions from EGU's firing coal, petroleum coke, 

or biomass should be predicated upon their efficiency, as has been proposed for and addressed in 

BACT determinations for other sources.

Response 5.1-14: The applicability criteria in the final rule will continue to cover IGCC units 

that burn less than 50 percent syngas. The IGCC unit will switch to either the multi-fuel-fired

combustion turbine subcategory (if burning 90 percent natural gas or less) or the base load 

natural gas-fired combustion turbine subcategory (if burning more than 90 percent natural gas)

during these periods.

Comment 5.1-15: Commenter (8973) believed that all units 25 MW and below, regardless of 

level of electricity supplied to the grid or fuel type, should be exempted to provide greater 

flexibility for entities needing to install new units for peaking purposes as well as those units 

generally needed in response to emergency conditions.

Commenter (9773) believed that the proposed standard should not apply to the following source 

categories: (1) types of generation that were not evaluated in setting the NSPS standard, 
5-17

including solid fossil fuel units smaller than 550 MW and developing technologies; (2) simple 

cycle combustion turbines; and (3) efficient combined heat and power (CHP) plants. 

Response 5.1-15: The applicability of this final rule does not cover units that are only capable 

of selling 25 MW or less or industrial CHP units. However, the EPA has concluded that it is 

appropriate to cover units greater than 25 MW and simple cycle combustion turbines. 

Comment 5.1-16: Commenter (9198) stated that EPA should clarify that all units subject to 

CAA section 129 solid waste combustion standards are exempt from the proposed GHG 

NSPS. The commenter noted that the Agency specifically cites in proposed Section 60.5509 that 

facilities that are municipal waste combustors (MWCs) subject to subpart Eb (large MWCs) are 

not subject to the proposed GHG NSPS, but it does not clarify that other MWCs subject to 

Section 129 are also exempt. The commenter stated that this exemption should include the small 

MWCs subject to Subpart AAAA. As EPA finalizes the rule, the commenter urged the Agency

to retain this important Section 129 solid waste combustion exemption for MWCs both large and 

small. 

Response 5.1-16: See Section III.D.3 of the preamble for a discussion of municipal waste 

combustors.

Comment 5.1-17: Commenter (9665) stated that the EPA should exempt the combustion of 

waste fuels, such as blast furnace gas and refinery fuel gas, to ensure that the rule does 

not reduce incentives for the use of these byproducts.

Response 5.1-17: While these fuels are covered under the final rule as part of the multi-fuelfired subcategory for combustion turbines, the requirements are minimal and will not discourage 

the use of these fuels.

Comment 5.1-18: Commenters (9736, 8969, 8964, 8970, 9318, 9671, 9672, 10392) cited the 

AMP/OMEA list of recommended exclusions for this rule, which included: All units 25 MW 

and below - regardless of level of electricity supplied to the grid or fuel type; All units supplying 

less than one-third (or 40% capacity factor, if EPA chooses to raise the threshold) of their 

potential electric output to the grid regardless of size or fuel type; Reciprocating internal 

combustion engines (RICE units) (EPA recommended excluding these sources); Non-natural gas 

stationary combustion turbines (CTs) (EPA recommended excluding these sources); Existing 

sources undertaking modifications or reconstructions (EPA recommended excluding these 

sources, which will be subject of a separate rulemaking); Certain projects currently under 

development (EPA recommended excluding these sources).

Commenter (9773) stated that simple cycle, solid waste fossil fuel generation smaller than 550 

MW, biomass, and CHP plants should be exempt from this ruling. 

Response 5.1-18: This final rule does not cover units that are not capable of selling over 25 

MW-n to the grid, stationary combustion turbines not capable of firing natural gas, reciprocating 

engines, modified combustion turbines, and certain modified steam generating units and IGCC 

units. The industrial CHP exemption has also been expanded since proposal. However, we are 

finalizing a modified version of the broad applicability approach we solicited comment on. Non-
5-18

base load and multi-fuel combustion turbines will be required to comply with an emission 

standard based on the use of clean fuels. The rationale for adopting the broad applicability

approach and the corresponding clean fuels standards is discussed in the preamble to this final 

rule.

Comment 5.1-19: Commenter (9591) stated that there has been a large increase in demand for 

diesel-fired reciprocating internal combustion engines, and decrease in coal-fired generation as a 

result of the decreased price of natural gas. The commenter recommended that as the share of 

smaller sources of generation increases in the electric market, these sources should be regulated 

under the proposed rule in order to preserve a level playing field.

Commenter 9665 stated that reciprocating internal combustion engines (RICE) can use a wide 

variety of fuels to generate power, can range in size from 120kW to 20 MW, and can be grouped 

to deliver a wide range of outputs to the grid. Commenter 9665 stated that in 2013, a utility in 

Oregon announced development of a 220 MW power plant composed of twelve 18 MW or larger 

RICE. Commenter 9665 opposed including simple cycle units in the GHG standard because 

modular RICE plants used for power generation are not included in the standard, and since 

modular RICE plants (like simple cycle turbines) have the capability of supporting the use of 

renewable resources for power generation, they compete directly in markets with expanding 

renewables. Commenter 9665 believed that applying the GHG standard to simple cycle turbines 

will act as an incentive for utility companies to select RICE technologies because RICE will not 

be subject to the CO2 limits or capacity factor constraints proposed for combustion turbines. 

Commenter 9665 also believed that including simple cycle turbines while omitting RICE could 

lead to overall emissions increases due to the higher carbon fuels typically used in RICE.

Commenter 9665 stated that including simple cycle gas turbines without imposing limitations on 

reciprocating engines would create incentives to install the excluded units and potentially lead to 

higher CO2 emissions when such units burn other fuels.

Response 5.1-19: The sliding-scale approach and final emission standard for non-base load units 

ensure that new simple cycle units will not be subject to burdensome requirements that restrict 

their historical use or potential future use backing up intermittent renewables. Therefore, the 

final rule will not provide a regulatory incentive to for owners and operators to move away from 

simple cycle combustion turbines toward other technologies not subject to the final rule.

Comment 5.1-20: Commenter (5605, 6564, 8952) responded to the EPA's request for input on 

the use of the new source review program is the appropriate mechanism for establishing site 

specific greenhouse gas requirements and whether the EPA should exempt stationary combustion 

turbines at compressed air energy storage (CAES) facilities; the commenter concluded that use 

of the NSR program could be appropriate, and expects construction of only a limited number of 

new CAES facilities; the commenter added that at these plants, all combustion turbines should be 

considered for NSR permit limits with no exemptions so that the entire energy generating system 

should be subject to an aggregate limitation on carbon dioxide emissions.

Commenter (10554) supported exemption of CAES facilities for three reasons: the proposed onethird electric sales of potential electric applicability requirement may not exempt all CAES 

facilities; the emissions from a CAES plant will be about one-third of those from a similarly 
5-19

sized combustion turbine (CT) plant on a per MWH basis and any emissions resulting from the 

electricity used to compress the air would already be accounted for by the facilities that 

generated that electricity, and it would be redundant to account for those emissions again in the 

output of the CAES plant; and finally, a CAES plant is expected to provide enhancements to the 

grid and allow successful integration of significant amounts of renewable resources while 

providing grid stability during intermittent operations.

Commenter (4711) a developer of CAES technologies supported exemption of stationary

turbines at CAES facilities for two reasons: the CO2 emissions associated with CAES turbine 

operation are well below the proposed standard and the number of CAES facilities likely to be 

built represents a small fraction of the generation expected to be brought into service due to the 

cost and scarcity of suitable underground storage media. The commenter added that at this point 

in the evolution of CAES technology, the commenter believed a strong argument can be made 

for exemption, but if the EPA decides to apply the proposed standard to CAES facilities, the 

commenter strongly urges the EPA to refrain from any effort to quantify the CO2 implications of 

compression energy.

Response 5.1-20: The final rule does not include a specific exemption for CAES units. These 

units will be subject to the non-base load unit requirements included in this final rule, which 

present minimal additional burden.

Comment 5.1-21: Regarding the proposed applicability provisions that limit applicability of the 

GHG emissions standards to newly constructed EGU technologies meeting the proposed 

definitions of steam generating units, IGCC, and stationary combustion turbines, Commenters 

(9592, 9597, 9678, 10100, 10952) supported the preamble language excluding from the proposal 

existing sources undertaking modification or reconstruction because the commenters believe the 

preamble language is consistent with the definition of "new source" in CAA section 111, and the 

commenters expressed agreement with the EPA's conclusion that if an existing source undertakes 

a modification or a reconstruction, it would not be treated as a "new source" subject to the 

proposed standard; some commenters (10100, 10952) requested that the EPA include an explicit 

exclusion for modified and reconstructed existing sources in the final rule. Another commenter 

(10243) requested that the EPA provide guidance that the proposed standard does not apply to 

modified or reconstructed units; this commenter also requested that the guidance delineate the 

portions of the affected facility that are subject to the standard and that the guidance reaffirm the 

pollution control project exemption in the general provisions of Part 60 and other guidance not 

directly related to the proposed rule language.

Commenter (9780) stated that EPA must clarify that the "affected facility" for purposes of an 

EGU CAA 111 modification is limited to the "steam generating unit" boiler island. The 

commenter stated that EPA's regulations and past guidance contain detailed rules as to when a 

physical or operational change at an existing source is a modification that triggers section 111(b). 

The commenter noted that in the case of section 111(b) standards applicable to fossil fuel-based 

EGUs, EPA has historically interpreted the "affected facility" to include only the "steam 

generating unit" boiler island, and not the components of the generating facility. The commenter 

stated that this means that installation of pollution control equipment falling outside the 

boundaries of the boiler island would not be a change to the "affected facility" and therefore 

cannot trigger regulation of that unit as a modified source under CAA section 111(b). 
5-20

Accordingly, stated the commenter, EPA should issue guidance that confirms that the installation 

of SO2 scrubbers, fabric filters and other add-on emissions control equipment does not entail 

either a physical or operational change to the boiler island.

Commenter (9665) stated that the EPA should include rule language that clearly shows subpart 

Da sources are not subject to NSPS modification requirements. The commenter pointed out that 

the proposed rule language makes it clear that modification and reconstruction requirements are 

not applicable for the proposed CO2 emissions standards in subparts KKKK and TTTT. 

However, commenters (9665, 10952) stated, the proposed regulatory text for revised Subpart Da 

does not include similar language, and the commenter recommended adding consistent 

exclusionary language to subpart Da.

Commenter 9780 stated that EPA should provide regulatory certainty by expressly excluding 

modified EGUs from applicability in the Regulatory Language. The commenter included specific 

changes they would make to the regulatory language:

1. Proposed Amendments to the Proposed Regulatory Language for Subpart Da 

'Standards of Performance for Electric Utility Steam Generating Units.'

60.46Da Standards for carbon dioxide (CO2).

(b) The following EGUs are not subject to this section:

***

(4) Existing EGUs, including existing EGUs that are modified or reconstructed.

2. Proposed Amendments to the Proposed Regulatory Language of Subpart 

KKKK 'Standards of Performance for Stationary Combustion Turbines.'

60.4305 Does this subpart apply to my stationary combustion turbine?

(c) For purposes of regulation of greenhouse gases, the applicable provisions of this subpart:

(1) affect your stationary combustion turbine if it meets the applicability conditions in 

subparagraphs (c)(5)(v) of this subsection.

(1)(I) Commenced construction after [DATE OF PUBLICATION IN THE FEDERAL 

REGISTER];

(2)(ii) Has a design heat input to the turbine engine greeter than 73 MW (250 MMBtu/h);

(3)(iii) Combusts fossil fuel for more than 10.0 percent of the heat input during any consecutive 

years.
5-21

(4)(iv) Combusts over 90% natural gas on a heat input basis on a 3 year rolling average basis; 

and

(5)(v) Was constructed for the purpose of supplying, and supplies, one third or more of its 

potential electric output and more than 219,000 MWh net electrical output to a utility distribution 

system on a 3 year rolling average basis.

(2) do not affect your stationary combustion turbine if it is an existing stationary combustion 

turbine, including if it is existing, modified or reconstructed.

3. Proposed Amendments to the Proposed Regulatory Language for Subpart 

TTTT 'Standards of Performance for Greenhouse Gas Emissions for Electric Utility 

Generating Units.'

60.5509 Am I subject to this subpart?"

(b) You are not subject to the requirements of this subpart if your affected facility meets any one 

of the conditions specified in paragraphs (b)(1) through (b)(56) of this section.

***

(6) Your affected facility is an existing EGU, including an existing EGU that has been modified 

or reconstructed.

Response 5.1-21: In June 2014, the EPA proposed standards for modified and reconstructed 

units. The EPA is finalizing standards for reconstructed steam generating units and combustion 

turbines. The EPA is also finalizing standards for modified steam generating units that increase 

hourly CO2 emissions by more than 10 percent. The EPA is withdrawing its proposed standards 

for modified steam generating units that increase hourly CO2 emissions by 10 percent or less, as 

well as the standards for modified combustion turbines. The EPA explains all of these decisions 

in the preamble to the final rule. The EPA notes that the pollution control project (PCP) 

exemption, which was not reopened as part of this final rule, exempts additions of pollution 

control equipment from being considered a modification.

Comment 5.1-22: Commenter (10098) stated that the EPA must clarify that the proposed 

standard applies to individual EGUs and not to facilities because the commenter believed that 

making the rule applicable at a facility level would affect existing facilities adding new capacity.

While recommending an explicit exemption for simple cycle units, commenter 9425 requested 

that the EPA clarify that applicability criteria for combustion turbines applies on a per unit basis 

and not on a facility-wide basis.

Response 5.1-22: NSPS applicability is determined based on the definition of affected facility

in each subpart. While the term affected facility is used for NSPS purposes, it generally refers to 

individual emission units. In this case, an affected facility refers to an individual EGU, not the 

entire facility.
5-22

Comment 5.1-23: Commenter 8743 stated that the EPA must exclude the Mesaba Energy 

Project from applicability under the proposed rule. The commenter described this project as a 

1200 megawatt integrated gasification combined-cycle ("IGCC") power plant to be located in 

Northeastern Minnesota. The commenter stated that the Project was selected by the U.S. 

Department of Energy ("DOE") in its competitive Clean Coal Power Initiative ("CCPI") Round 

II solicitation to receive federal funding. The commenter said that the EPA must exempt the 

project because of the significant work that the commenter has undertaken to preserve the 

validity of required permits for both NGCC and IGCC plans. Commenter 8743 stated that the 

EPA had drawn an errant conclusion in the technical support document related to the EPA's 

assertion that the developer of the Mesaba Energy Project had relinquished the right to have its 

comments taken seriously because the developer thereafter sought to permit the project's power 

block apart from its gasification equipment. The commenter believed that it is not in the interest 

of Minnesota or federal taxpayers to waste the significant efforts and funding expended to date 

on the project. The commenter respectfully requested that EPA make certain changes to the rule 

to ensure the Mesaba Energy Project can comply with the proposed standard or be exempted; 

alternatively the commenter suggested that the EPA should provide a mechanism in the Rule or 

institute some other relief to reimburse stakeholders for their investments and support the 

completion of permitting of the power block portion of the project to be fired by natural gas so 

that the project can comply with the proposed rule.

Commenters 10953, 11503, and 11221 provided comments on the proposed rule's treatment of 

Plant Washington, a proposed 850 megawatt (MW) coal-fired power plant that would be located 

in Washington County, Georgia. The commenter stated that Plant Washington has not 

commenced construction and does not qualify as an existing source exempt from the proposed 

new standards. The commenter also stated that Plant Washington is not on the verge of 

commencing construction because the project developer is currently seeking an extension of the

construction deadline under the project's Prevention of Significant Deterioration (PSD) 

preconstruction permit. The commenter went on to state that this project is "stalled" with no 

significant financing, no customers to buy the expensive power it would generate, and no real 

prospect of moving forward in the near future. The commenter provided additional legal 

arguments for why this particular project should not be treated as having "commenced 

construction" under the general provisions of Part 60.

Commenter 10953, 11053 urged the EPA to fully regulate Georgia's Plant Washington under the 

new NSPS for GHGs. The commenter stated that the draft rule suggested that Plant Washington 

may be designed to offer fuel diversity to a group of customers that are willing to pay a premium 

in electricity prices. The commenter lives in Georgia and stated that they have no desire to pay a 

premium and add more coal-fired power to their coal-heavy energy mix.

Commenter 10030 stated that they understand that EPA's proposal would not apply to the 

Wolverine Clean Energy Venture (WCEV), but that the WCEV's status relative to a final GHG 

NSPS for new EGU's could change if the commenter does not actually commence construction 

of the project prior to the finalization of an applicable NSPS emission standard for CO2. The 

commenter stated that all the Proposal does is "propose" that the WCEV not be subject to the 

Proposal's standards if construction commences before a final rule. Uncertainty remains as to 

whether the WCEV will be subject to a standard under Section 111(a) or Section 111(d) and 

what that standard may be.
5-23

Response 5.1-23: See Section III.J of the preamble for a discussion of certain projects under 

development. The EPA is not making final applicability determinations for these sources in the 

final rule.

5.2 PROSPECTIVE APPLICABILITY CRITERION - INTENDED 

PURPOSE

Comment 5.2-1: Commenter 9514 supported retaining the current heat input capacity under 40 

CFR Part 60 Subpart Da as applicability criteria for the new GHG standard for steam generating 

units so all parties can determine prior to construction whether the NSPS applies. 

Commenters (9514, 10100) noted that the proposed revisions to Subpart Da were inconsistent 

with the alternative revisions under Subpart KKKK and Subpart TTTT because the proposed 

revisions under Subpart Da omitted the criteria specific to the prospective design purpose of a 

new EGU. 

Commenter 9514 opposed use of prospective criteria related to the intended purpose of a new 

EGU because the commenter is concerned that unexpected business conditions in the future may

make it more profitable for the operator of an industrial unit to sell electricity to the grid rather 

than support the intended industrial activity; commenter 9514 also provided anecdotal evidence 

of industrial sources selling significant quantities of power to the grid during periods of low 

prices for their industrial product. 

Commenter 9514 also expressed concerns that operators might misrepresent the future-intendedpurpose of a new unit to avoid applicability. Commenter 8957 opposed the prospective 

applicability criteria and believed applicability should be based on a source's actual operations 

rather than the source's purpose at the time of construction.

Commenter 9514 also opposed the use of prospective applicability criteria because an interested 

member of the public must demonstrate an ongoing violation in order to bring a citizen suit, and 

a prospective obligation cannot be determined with certainty; therefore, the commenter believed, 

the prospective criteria included in the EPA's proposed regulations undermine citizen 

enforcement, a critical component of the Clean Air Act.

Commenter 10098 supported use of the prospective purpose criteria because the commenter 

believed this criterion avoids uncertainty at the time of construction. 

Commenter 9771 supported the general idea of a prospective applicability determination and 

recommended that EPA require applicants to determine which operational category they will be 

subject to, including corresponding emissions limits, at the initial application stage of permitting, 

followed by ongoing verification, because this approach is consistent with many federally 

approved SIPs.

Commenter 9427 asked, who determines, and when do they determine whether or not the 

"purpose" of the turbine is to supply more than one-third of its potential electric output to the 

utility distribution system? This commenter also asked what criteria should be used for this 
5-24

prospective determination. Commenter 9427 recommended that the "purpose" criteria in 

proposed section 60.4305(c)(5) should be removed as subjective and unenforceable as a practical 

matter.

Response 5.2-1: The EPA agrees that prospective applicability criteria and determining “intent” 

of a project is not an ideal approach. Therefore, the applicability in this final rule replaces the 

prospective intent applicability criteria with federally enforceable permit restrictions. This 

approach eliminates the subjective nature of determining “intent” and makes applicability criteria 

clear for the regulated community, permitting authorities, and the public.

5.3 RETROSPECTIVE APPLICABILITY CRITERIA - GENERAL

Comment 5.3-1: Commenters (8957, 9427) generally supported the use of retrospective 

applicability determinations but opposed using a different applicability period for combustion 

turbines compared to boilers, and the commenter believed the applicability test should be three 

years for both boilers and turbines. Commenter 8957 recommended including requirements that 

require operators to use their business projections to evaluate whether or not they will be subject 

to the standard at the end of the three year period; sources projecting operations above 

applicability thresholds should be required to maintain all records and submit all reports required 

by the rule on an annual basis; source projecting non-applicability should be required to maintain 

records verifying applicability status. Commenter 8957 stated that a compliance report should 

not be required for non-affected sources, but verification records should be maintained for five 

years and available to EPA or the permitting authority upon request. 

Commenter 9426, a regional electric utility, stated that they do not foresee any implementation

issues for either steam generating units or combustion turbines associated with proposed 

applicability requirements based on operations after construction; however this commenter 

simultaneously reiterated previous recommendations for an explicit exclusion for simple cycle 

turbines.

Commenter 9733 supported the proposed retrospective applicability criteria adding "and 

supplies" to "constructed for the purpose of supplying" because these changes make the 

exemption for CHP units comparable to the exemption for cogeneration units in the Acid Rain 

program.

Commenter 9733 supported the proposed revisions to Subpart Da applicability related to adding 

the phrase "and supplies" to "constructed for the purpose of supplying" because this provision 

makes determination of NSPS applicability an ongoing process rather than one based solely on 

predictions prior to construction. This commenter also supported the proposed annualization of 

the 25 MW capacity requirement to 219,000 MWh per year because the commenter believed

these revisions will make the proposed exemption for CHP units comparable to the exemption 

for cogeneration units in the Acid Rain program. Commenter 9733 also supported the additional 

flexibility provided by the proposed one-third sales criterion. 

Commenter 9427 supported the use of retrospective operating data as applicability criteria but 

was confused by the averaging period. 
5-25

Commenters (5537, 8952, 9513, 9514, 9771,10095, 10098) opposed the proposed retrospective 

applicability criteria related to actual output supplied during a preceding compliance period 

because, chronologically, such criteria do not allow the permitting authority and the public to 

know in advance whether or not the GHG standard applies to a proposed new unit. In the 

proposed applicability criteria language, "was constructed for the purpose of supplying, and 

supplies", commenter (9514) recommended that the conjunction preceding the retrospective 

criteria be revised from "and" to "or" because the commenter believed this logic is consistent 

with current rules implementing the Acid Rain program and is consistent with the EPA's "once 

in, always in" doctrine.

Commenters (2984, 7994, 8918, 8952, 9382, 9407, 9425, 9426, 9499, 9665, 9667, 9678, 9774, 

9780, 10048 10098, 10100, 10240, 10392, 10518, 10660, 10876, 10952) stated that EPA should 

exclude simple cycle turbines from the one-third sales criteria. Commenter 10098 stated that 

EPA's inclusion of simple cycle turbines is arbitrary, capricious, and unlawful. Commenter 

10098 also stated that the very notion that owner and operators would be subject to an operationbased applicability test is absurd under the NSPS, which was designed to provide clear and 

predictable standards of performance for new sources that would apply when they begin 

operations.

Commenter 9514 opposed the use of these retrospective applicability criteria because an 

interested member of the public must demonstrate an ongoing violation in order to bring a citizen 

suit; midway through the proposed 3-year applicability period, the source's obligations under 

the standard cannot be determined with certainty; therefore, the commenter believed, the 

retrospective, 3-year criteria proposed undermines citizen enforcement under the Act.

Commenter 9513 opposed the proposed use of retrospective applicability criteria 

because applicability could change from month to month and the commenter believed these 

changes in applicability determinations would create implementation problems for compliance 

and enforcement. Additionally, commenter 9513 expressed concerns that permitting authorities 

would not know for 3 years whether a source met the NSPs applicability criteria, and authorities 

would not have a proper basis for considering NSPS sources when establishing BACT floors.

Commenters (5537, 9771), pre-construction permitting authorities, opposed any retrospective 

applicability approach to be completed for a new source after issuance of the construction permit 

because the commenters believed this approach would result in compliance issues and in 

difficulties in determining proper pre-construction and operating permit conditions. 

Commenters (9514, 9666) opposed the aspect of the criteria that differentiates EGUs that sale 

output to the grid versus EGUs owned by industrial sources for onsite consumption of electricity. 

Commenter 9514 opposed this aspect because the commenter believed that such criteria would 

allow a consortium of companies to form for the purpose of purchasing electricity directly from 

new coal-fired plants (i.e., bypassing the grid); the commenter believed that such an arrangement 

would allow the associated new the coal-fired plants supporting the industrial consortium to 

avoid applicability based on the proposed language. 

Commenter 10098 believed that if retrospective applicability criteria are finalized, simple cycle 

operators could face an untenable position: if unanticipated peaking power is required in a 
5-26

certain area, operators would face the choice of shutting down the plants, potentially resulting in 

brown outs, violations of contractual power supply agreements, and violations of North 

American Electric Reliability Corporation and ISO guidelines, or continue operating and be 

subject to three years of NSPS violations. 

Commenter 10098 believed that an applicability test that concludes after construction and 

operation have commenced is inconsistent with the general purpose of an applicability test: 

which is intended to provide clear and predictable standards of performance for new sources that 

would apply when they begin operations. 

Commenter 8952 opposed the retrospective 219,000 MWh criteria because this commenter 

believed it will allow smaller units to operate for additional hours, above the one-third sales 

capacity threshold while restricting operation of more efficient larger turbines

Commenter 9771 recommended that EPA require applicants to determine which operational 

category they will be subject to, including corresponding emissions limits, at the initial 

application stage of permitting, followed by ongoing verification, because this approach is 

consistent with many federally approved SIPs. 

Commenter 5537 stated that in addition to the typical NSPS applicability criteria (i.e., a source 

must be greater than 250 million Btu per hour (mmBtu/hr) heat input), EPA is also proposing to 

include applicability provisions akin to the Title IV Acid Rain applicability provisions. 

Commenter 5537 stated these additional applicability criteria would apply for new fossil fuelfired electric utility steam generating units, integrated gasification/combined cycle (IGCC) 

sources, and natural gas-fired stationary combustion turbines for the purpose of regulating 

CO2 emissions from these sources. 

Commenter 9514 stated that EPA should abandon its proposal to re-define EGUs so as to 

exclude any unit from regulation unless it is designed to supply, and actually supplies, more than 

one-third of its potential electric output capacity and 219,000 MWh annually to the grid. The 

commenter stated that instead, it should continue to provide specific calculation procedures for 

emissions from regulated cogenerating facilities, and should apply the standards to all EGUs that 

supply or were constructed for the purpose of supplying any electricity for sale to the grid.

Commenter 9514 stated that under EPA's proposal, a source would no longer be subject to the 

NSPS if it fell below the threshold for any of the applicability metrics that are calculated on a 

.......(or, in some cases, annual) basis. The commenter felt that this would create a situation in 

which no one would know whether a particular plant will be subject to the standards at all until 

years after the emissions had already occurred. Furthermore, because a number of the proposed 

applicability provisions apply on a rolling basis, the commenter stated plants operating near the 

threshold could move in and out of the regulatory system from one month to the next. the 

commenter stated not only would this create significant practical problems for compliance and 

enforcement purposes, it would add unnecessary complication to Title V and PSD permitting as 

well, since authorities would not know whether certain sources would or would not be subject to 

the NSPS until well after those plants had been operating for several years, and would not have a 

proper basis to establish a BACT floor for those units. The commenter noted that EPA has 

suggested that sources need flexibility in their operations. The commenter agreed that there may
5-27

be areas, such as those addressed in EPA's tailoring rule, where CO2 emissions are treated 

differently than SO2 or NOx, but EPA has not attempted to demonstrate a reason for such a 

difference in these provisions.

Commenter 9514 stated that the definition of co-generating sources would pose a much larger 

problem by (1) creating a situation in which source operators, permitting and enforcement 

authorities, and the public will not know whether a source is in compliance until the end of the 

averaging period.

Response 5.3-1: The EPA agrees that retrospective applicability criteria based on actual 

operating conditions are not ideal. The final applicability criteria do not use this approach. 

Instead, many of the final applicability criteria are based on permit restrictions, while others are 

being finalized as subcategorization criteria based on operating conditions. See Sections IV.A.1

and IX.A of the preamble for a discussion of the retrospective applicability criteria.

5.4 ONE-THIRD SALES CRITERION

Comment 5.4-1: Commenter 9666 supported the general intent of the Agency's proposed onethird sales criterion with respect to NGCC units, however commenters (8909, 8918, 8952, 9425, 

9665, 9666, 9678, 10095, 10098, 10135, 10398) expressed concerns that this criterion may not, 

as a practical matter, exempt all simple cycle turbines for future operations.

Commenter 10240, a preconstruction permitting authority, supported the proposed one-third 

sales criterion and believed this provision is sufficient to support the increased harnessing of 

renewable energy sources while allowing simple cycle turbines to perform their critical role 

providing stability to the grid.

Commenter 9426 stated that if EPA chooses not to provide an explicit exclusion in any final rule 

for simple-cycle turbines, the commenter recommended the agency adopt the one-third of 

potential electric output sales applicability criterion on a three-year rolling average basis.

Commenters (3862, 6505, 8973, 9001, 9201, 9407, 9428, 9595, 9601, 9678, 9767, 9779, 10038, 

10086, 10097, 10100, 10238, 10240, 10358, 10520, 10554) supported the EPA's proposed onethird sales criterion. Commenter 9678 asserted this exclusion provides operational flexibility that 

ensures grid reliability.

Commenter 10952 supported limiting applicability of the proposed NSPS for natural gas EGU CTs 

to units supplying more than one-third of potential electric output and more than 219,000 MWh net 

annual electric output to the grid because inefficiencies inherent with lessor operation would present 

compliance problems with the proposed standard 

Commenters (9201, 9733) supported the one-third sales criterion because it is consistent with 

longstanding Acid Rain provisions. Commenter 9733 also supported the proposed additional 

flexibility included in the applicability determination for the one-third sales criterion that allows 

use of the actual "design electrical output efficiency."
5-28

Commenter 10395 stated that based on their understanding, if SC CTs installed by the 

commenter in the future are constructed for the purpose of supplying, and actually supply, 

219,000 MWh or less of electricity to the grid on a 3-year-rolling average basis, they should be 

exempt from the proposed rule and the stringent CO2 emission standards. The commenter stated 

that EPA should confirm in its final rule that EPA concurs with this analysis, if EPA decides not 

to completely exclude SC CTs from KKKK regulation. The commenter believed that this would 

provide greater flexibility to use simple cycle CTs to meet the essential purposes noted above.

Commenter 9499 stated that if the EPA does not exempt SC units from the new standards, the 

Agency should at a minimum consider regional differences in assessing the reasonableness of the 

33% capacity factor limitation, allowing for a higher capacity factor in wind rich arid regions of 

the country, and propose a CO2 emission limit that can be met by SC units.

Commenter 10395 requested that the EPA further clarify the meaning of supplying more than 

one-third of potential electric output and more that 219,000 MWh net annual electric output to 

the grid. This commenter stated his understanding of the one-third sales criterion and requested 

that the EPA confirm in the final rule concurrence with the commenter's interpretation that if a 

unit provides less than 219,000 MWh net output to the grid on a three-year rolling average basis, 

the unit is not subject to the proposed standard. 

Commenters (8952, 9407, 9425, 9665, 10095, 10098, 10929) believed that EPA should not 

arbitrarily restrict the operation of simple cycle turbines to less than the one-third sales threshold 

because such a restriction could adversely affect grid reliability as dispatchers who need simple 

cycle turbines to support significant renewable generating capacities cannot use those permitted 

simple cycle assets above the threshold because the simple cycle turbines cannot comply with the 

proposed standard. Commenters (8952, 9407, 9425, 10095, 10098) asserted that the EPA has not 

included in the record analyses of effects (on GHG emissions, grid reliability, and compliance 

with renewable portfolio standards (RPS)) of the one-third sales criterion related to anticipated 

demand growth for renewables and the effective limit on use of simple cycle assets to reliably 

incorporate renewable assets into energy markets implementing RPS. 

Commenters (8918, 8937, 8952, 9425, 9592, 9665, 9666, 9678, 9780, 10095, 10098, 10100, 

10102, 10395, 10929, 11184) recommended complete exemption of simple cycle units, but 

stated that if a sales criterion is retained in the final rule, the one-third sales criterion should be 

revised to further ensure grid reliability. Commenter 9425 stated that the proposed standard was 

based on the efficiencies achieved by combined cycle units and requested that the EPA clarify

the compliance status of a less-efficient simple cycle unit that exceeds the one-third sales 

criterion and that has an average emission rate above the proposed standard. 

Commenters (8952,9665) believed that in the absence of a full exemption for simple cycle 

combustion turbines, the sales criterion should be structured as a sliding scale function so that the 

particular applicability threshold for a given simple cycle unit is proportionate to the unit's 

efficiency; units with higher efficiencies would have correspondingly higher sales criteria. The 

commenters provided examples based on highly efficient simple cycle machines operating at 

1,100 pounds of CO2 per gross MW hour produced: the commenters suggested that such units 

should be allowed higher capacity factors than the one-third factor proposed. The commenters 
5-29

subsequently compared the highly efficient simple cycle turbine to less efficient units with 

emission rate of 1,450 pounds of CO2 per gross MW hour: the commenters suggested that the 

applicability threshold for such less efficient simple cycle turbines (along a sliding scale) would 

be 33 percent as proposed. 

Commenters (8952, 9407, 9425, 9665, 10095, 10098, 10929) opposed the one-third sales 

criterion because it is based on historic generating data with fewer renewable generating assets 

than are expected in the future. These commenters stated that the EPA's historic analysis does 

not account for federal and state regulatory policies promoting renewable generation, and the 

commenters believe future energy markets (that may be significantly different than historic 

markets) should dictate appropriate simple cycle turbine capacity factors. 

Commenter 8937 stated that the 33% and 219,000 MWh applicability thresholds for simple cycle 

turbines reward low efficiency, smaller simple cycle units at the expense of larger high 

efficiency units, and the commenter opposed these applicability provisions because, the 

commenter asserted, these provisions restrict the ability of utilities to use the most efficient 

simple cycle gas turbines and are counterproductive to the EPA's objective of reducing 

emissions. 

Commenter 8909 opposed the one-third sales criterion because the commenter is concerned the 

criterion will create incentives for utilities to use less efficient, simple cycle generation and the 

commenter recommended establishing separate emissions standards for simple cycle units. 

Commenter 10052 opposed the one-third sales criterion specifically for simple cycle turbines 

because the commenter believed that because it will encumber the ability of utility companies to 

ensure system reliability and encumber their ability "to serve customers as much electricity as 

they want, when they want it." Commenter 10052 also stated that the sales criterion as proposed 

does not consider the length of time needed to incorporate new resources (such as combined 

cycle power blocks to displace simple cycle units being dispatched at high capacity factors) into 

a utility portfolio which can take in excess of five years during which time simple cycle units 

may need to operate above the proposed sales criterion to maintain system reliability. 

Commenters (8023, 8957, 9513, 9514, 9771) opposed the one-third sales criterion. Commenter 

8957 opposed the one-third sales criterion and believed the exemption will allow owners to build 

generating units with significantly larger capacities than can be justified based on the current 

demand for electricity, thereby avoiding applicability of the standard by running the oversized 

units at less than one-third of their oversized, rated capacities; this commenter believed that such 

an "oversizing" strategy will be more economical than CCS. 

Commenter 8957 opposed inconsistent treatment of boilers and combustion turbines when 

applying the one-third sales criterion and believed the criterion should be based on a three-year 

rolling average for both boilers and combustion turbines. Commenter 8957 also opposed 

establishing a separate capacity factor of 20 to 40 percent for combustion turbines because it may

allow turbines to avoid applicability. 
5-30

Commenter 9513 opposed the proposed one-third sales criterion because the criterion would 

exempt peaking units and many load following units including the new fast start combined cycle 

units designed to support renewables. 

Commenter 9514 opposed the one-third sales criterion in favor of specific emissions calculation 

procedures that accommodate cogenerating facilities and that apply to all EGUs that supply or 

were constructed to supply any electricity to the grid. Commenters (9514) also opposed the onethird sales criterion because this criterion will exempt peaking units that are not industrial units 

and have no cogeneration purpose or capacity and because this criterion will complicate 

regulation of existing coal- or gas-fired units that operate at capacity factors of less than onethird, since the existence of applicable section 111(b) standards are a predicate for regulation by 

states under section 111(d). 

Commenter (9514) recommended revising the "one-third" sales criterion to "any" sales to 

include fast-start CCGTs that complement the variable loads produced by renewable resources. 

Commenter 9514 also stated that if the EPA retains an applicability threshold based on grid 

sales, the agency should close a potential loophole for CCGTs (that may be constructed for the 

purposes of supplying low capacity factors complementary to renewable generating capacity) by 

referring not to a plant's "potential electric output," but to its "intended electric output." 

Commenter (8023, 9514, 9771) opposed the premise proffered by the EPA in the preamble that 

the one-third sales criterion "does not explicitly exclude simple cycle combustion turbines, but as 

a practical matter, it would exclude most of them because the vast majority of simple cycle 

turbines sell less than one-third of their potential electric output." Commenters (8023, 9514, 

9771) opposed this premise because these commenters believe that GHG standards should apply 

to peaking units and that the EPA should develop GHG standards specifically for peaking units 

(as a subcategory of EGUs) as well as other targeted types of EGUs necessary to support 

emerging plans to optimize use of variable renewable resources. Commenters (8023, 9771) 

emphasized the need for flexible, dispatchable, generating assets in service territories with 

progressive RPS. Commenter 8023 pointed out that use of variable output renewable resources 

requires a thermal generation fleet that is both flexible enough to sit idle or at a very low output 

to allow absorption of the solar energy generated at midday, and equally capable of quickly 

contributing up to 13,000 MW of firm, dispatchable resources between 4:00 and 8:00 PM, as the 

sun sets and peak evening demand occurs. Commenters (8023, 9771) believe that the proposed 

applicability criteria are incompatible with developing the suite of emissions standards necessary

to complement optimum use of renewables. 

Commenters (8023, 9771) stated that flexible EGUs with the ability to cycle and ramp to 

accommodate fluctuating renewables will have different emissions profiles compared to EGUs 

that are operated as either baseload or peaker units because frequent cycling and ramping will 

decrease thermal efficiency and increase GHG emissions per MWh compared to units providing 

stable baseload energy. Commenter 9771 stated that even when the flexible GHG emission 

sources are operated at a full steady state (e.g., during periods of no wind or solar activity), the 

very engineering design that enables the flexible operation may also reduce thermal efficiency. 

Commenter 9771 stated that newer EGU projects include multiple modules that allow 

incremental dispatch of the modules, each able to start and shut down quickly (often more than 
5-31

once per day) and rapidly ramp up and down. Commenter 9771 stated that existing units are 

being similarly dispatched, demonstrating the increasing need for flexibility while maintaining 

grid reliability as California de-carbonizes the electricity sector with greater amounts of variable 

renewable resources. Commenter 9771 stated that the EPA should move to regulate low capacity

factor combustion units using subcategories as quickly as possible, rather than exempting any 

units.

Commenter 3175 stated that under the proposed new source standards, the supply of the highest 

efficiency gas turbines will likely exceed the thresholds established for emissions of CO2 as the 

expected capacity factors would likely be greater than 40%. Commenter 3175 stated the net 

result might be the installation of a greater number of smaller turbines to remain below the 

thresholds, or the use of existing far less efficient turbines currently installed on the system. 

Commenter 3175 believed this would be an unfortunate and unintended result of the new 

regulation whereby the intent of the new source standards would be negated.

Commenter 9514 stated that EPA should abandon its proposal to re-define EGUs so as to 

exclude any unit from regulation unless it is designed to supply, and actually supplies, more than 

one-third of its potential electric output capacity and 219,000 MWh annually to the grid. Instead, 

it should continue to provide specific calculation procedures for emissions from regulated 

cogenerating facilities, and should apply the standards to all EGUs that supply or were 

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

Commenter 9514 stated that approximately one-sixth of existing coal-fired EGUs would be 

exempt from this ruling, which is unacceptable.

Commenter 9514 believed the one-third sales criterion will act as an incentive for plant operators 

to serve the demand for renewable load-following generation with less efficient simple cycle 

technology; this commenter believed that fast-start combined cycle power blocks are an available 

and technically feasible option for meeting variable load-following demand. Commenter 9514 

believed that the agency should abandon the one-third sales criterion and apply the rule to all 

sources, simple-cycle and combined-cycle alike, but within this context to apply different 

emissions limits depending on the numbers of hours a unit operates per year. Commenter 9514 

provided figures based on emissions data from the EPA's Clean Air Markets Division; these 

figures indicated that since 2007 nearly 900 combustion turbines have been placed into service 

with emission rates ranging from 900 to 2000 pounds of CO2 per gross MWh; commenter 9514 

opposed the one-third criterion because the commenter believed the criterion would exempt 

similar, new high-emitting units from applicability under GHG standards. Commenter 9514 

asserted that the EPA did not provide a rationale for excluding peaking units with the one-third 

sales criterion and also asserted that the rationale for exclusion cannot be based on excess costs 

because, the commenter further asserted, there is no demonstrable correlation between the 

efficiency of a CT (within a given size class) and capital cost. Commenter 9514 also opposed the 

one-third sales criterion based on the commenters' analyses of CAMD data that indicated onesixth of coal-fired EGUs fell below the one-third sales criterion during 2012; the commenter also 

asserted that many combined cycle units will fall below the one-third sales criterion and 

generally asserted that the one-third sales criterion is too broad and could allow a large portion of 

the power sector to avoid applicability.
5-32

Commenter 9514 noted, "if EPA applied the rule to all CTs and CCGTs, regardless of 

capacity factor, a proper determination of BSER would ensure that more efficient CCGT 

technology is required for intermediate and load-following units." Commenter 9514 further 

stated, "By limiting regulated sources to cover only those that supply more than one-third of their 

potential electric output capacity to the grid, EPA would exclude units that operate at a 

significant capacity for a significant portion of the year (e.g., 60 percent capacity for half the 

year). Such units are intermediate-load rather than peaking units, and should be subject to the 

standard." Therefore, commenter 9514 asked that "all EGUs that provide energy capacity to the 

grid [be] subject to the rule."

Commenters (8952,9665) opposed the provision to allow 219,000 MWh net electrical output per 

year because this criterion allows inefficient, small units to operate above the one-third sales 

criterion and deliver power to the grid while more efficient, large units would be restricted from 

providing more economical (and lower emitting) energy to the grid. 

Commenter 8937, 8952, 9499 stated that at the very least, EPA should consider increasing the 

sales threshold to 50% to accommodate the real world issues noted in the commenter's comment. 

Commenter (10950) stated that they strongly support excluding simple cycle turbines from 

the proposed rule, or alternatively, EPA could exempt SC units operating at or below a capacity 

factor of 50 percent to help promote the use of high efficiency SC turbines. The commenter 

stated that an exemption for SC units is critical because limiting the exclusion from the rule to 

units that supply less than 2919 hours to the grid is insufficient to cover many potential operating 

scenarios for SC units. 

Commenters (8952, 9678, 9425, 10095, 10098) believed the one-third sale criterion applied to 

simple cycle units over a three-year period will adversely affect grid reliability because of 

operators' uncertainty about future compliance dates and related decisions to curtail operations to 

increase capacity factor compliance margins (i.e., applicability margins); these commenters were 

also concerned that such compliance decisions by operators will drive up the cost of electricity as 

the most efficient new units are taken out of service to preserve compliance margins and older, 

less efficient units with no capacity limitations are ramped up instead. Commenter 10095 

believed that if simple-cycle CTs are not excluded altogether, an exemption of 40 percent for 

these units is not only warranted but also necessary for grid security and reliability; commenter 

10095 also said the EPA should presume that some simple cycle turbines will operate above the 

40 percent threshold. 

Commenters 9381, 9780 stated that if the EPA does not explicitly exempt simple-cycle CTs, the 

Agency must increase the sales limitation to 40 percent of potential electric output to provide 

maximum operating flexibility. This commenter also stated that the EPA must address whether 

simple-cycle units that exceed the sales criterion limit would be subject to an emissions limit 

only for those periods in which sales exceeded the limit or would the EPA invoke "once-inalways-in." This commenter asserted that the EPA cannot legally subject simple cycle units to an 

emissions standard that they cannot ever achieve if they exceed the sales criterion.
5-33

Commenter 7994, 8023, 9591, 9661, 9770, 9780, 10043, 10095 stated that if EPA does not 

explicitly exempt simple-cycle CTs, the Agency must increase the sales limitation to 40 percent 

of potential electric output to provide maximum operating flexibility.

Commenter 8973 believed that all units supplying less than 40% of potential electric output -

regardless of size or fuel type-should be exempted to provide greater flexibility for entities 

needing to install new units for peaking purposes as well as those units generally needed in 

response to emergency conditions.

Commenter 9667 stated that with respect to the option of changing the applicability

requirements, such as increasing the 33 percent capacity factor up to 40 percent of potential 

electric output sales on a three-year basis, this is still insufficient to fully address the problems 

created by including simple cycle turbines.

Commenter 9661 believed a 40% capacity factor sales criterion is appropriate because of 

looming, large-scale coal plant closures throughout the United States and our country's historic 

trend of over-reliance on coal could require additional operation of peaking capacity to ensure 

grid stability after closure of the coal plants; because of increasing amounts of renewable energy; 

and because the 40% threshold encourages expanded use of combined cycle technologies. 

Commenter 9770 also supported a capacity factor exemption of forty percent on a three year 

basis because such an exemption is consistent with the operating permits for simple cycle 

generating units, it allows further support of the intermittent renewable resources required by 

Minnesota statutes, and it averages out market fluctuations caused by weather events and 

infrastructure constraints.

Commenter 10618 primarily supported exemption of simple cycle turbines, but supported a 40% 

sales criterion if one will be required in the final rule. This commenter also stated that in cases 

where simple cycle turbines are constructed with the intent to operate prior to the future 

construction of a heat recovery steam generator (HRSG), such turbines should be exempted from 

the proposed rule until such time that construction of the HRSG and related equipment is 

completed and the unit commences operation in a combined cycle mode.

Commenter (9772) was concerned that EPA's proposed 33 percent capacity factor to exclude 

peaking units from the NSPS may not be sufficient to also exclude regulating units. The 

commenter stated that even the 40 percent capacity factor considered in the NSPS may not 

provide the flexibility for a regulating unit to fulfill its legally defined mission. The commenter 

requested EPA consider excluding regulating units altogether from the proposed rule. 

Commenter 9780 believed that using a 40% sales criterion could have the effect of exempting 

NGCC units that run at lower capacity factors. The commenter acknowledged that the flexibility

afforded by the sales criterion will allow simple-cycle CTs to provide grid support services, but 

the commenter stated there is no reason to apply those criteria to NGCCs if it would result in 

exempting certain new combined cycle units from the proposed standards. The commenter stated 

that if the final rule does not provide a clear exemption for simple-cycle CTs, the sales 

criterion should be revised to exempt only simple-cycle CTs without exempting NGCCs, and the 

commenter stated that one way to address this concern would be to increase the potential sales 
5-34

applicability limit to 40 percent and divide combustion turbine technologies into 

two subcategories, simple-cycle and combined-cycle.

Commenter 7540 recommended a sales threshold of 40 percent, on the proposed three-year 

rolling average, to determine applicability of this standard. In addition to the flexibility this 

threshold would provide to units that are designed to operate at capacity factors below the sales 

threshold, Commenter 7540 stated it would provide owners and operators with additional 

flexibility to optimize a unit during initial operation before being subject to the standard. 

Commenter 7540 stated that based on their analysis of the data EPA posted to the docket in 

support of the combustion turbine standard, none of the NGCC units exceed the proposed 

standard once they exceeded the sales threshold on a three-year rolling average basis.

Commenter 9406 opposed the one-third sales criterion, but stated that if the final rule retains 

criteria for excluding peaking units, the criteria should be one-fifth of the peaking unit's potential 

electric output rather than one-third.

Commenter 8911 provided an analysis concluding that a 10 percent sales criterion on a 3 year 

rolling average is sufficient to ensure grid reliability except in instance of "dire emergencies." 

The commenter believed that regulators have the authority to relax regulations during such 

emergency periods.

Commenter 7976 recommended that plants operating at levels lower than 10% CF could be 

unregulated to allow more owner flexibility in technology selection because their contribution to 

CO2 emissions will be minor. The commenter stated plants operating at levels above 65% CF 

could be unregulated to encourage construction of plants that can achieve less than 840 lb. CO2 / 

MWh - a level that is very challenging to achieve. The commenter stated that their suggested 

NSPS formula acknowledges the legitimacy of permitting the construction and operation of 

higher heat rate and emission rate plants when appropriate, but still reduces overall emissions by

limiting operation of higher emission rate plants.

Commenter 9646 stated that EPA's proposal to exempt EGUs that supply one-third or less of 

their electric output to the grid is not at all appropriate. The commenter stated that one-third is a 

significant amount of time - 8-hours a day; the same as a full time job. The 

commenter recommended that EPA establish a 5 percent threshold. 

Citing a review of air permits for 35 simple cycle turbines that commenced operation between

June 2006 and May 2013, commenter 9665 asserted that system operators and federally

approved air quality permitting authorities recognize that new simple cycle combustion turbines 

will require capacity factors greater than one-third to reliably complement increasing usage of 

renewable resources. 

Commenter 9665 provided some alternative approaches if EPA chooses not to exempt simple 

cycle turbines. The commenter stated that EPA could exempt simple cycle units operating at or 

below 50 percent capacity, providing that total annual emissions are capped at or below the 

emission levels that excluded units could emit, could establish different capacity factors based on 
5-35

the efficiency of the simple cycle unit, or could establish an absolute tonnage per MW cap based 

on the nameplate or peak unit output.

Commenter 8952 recommended a capacity-factor exclusion of "50% as a minimum." 

Commenter 9666 stated that in general the exclusion of turbines below 73 MW (250 MMBtu/h) 

and those that satisfy the one-third sales criterion should eliminate some turbines that might 

violate the NSPS. However, the ambiguities associated with the one-third sales criterion make it 

difficult, if not impossible, to accurately analyze its impact on the CO2 emissions limit. This 

ambiguity must be clarified before it can be accurately be determined what the appropriate CO2

NSPS level should be.

Commenter 7976 stated that the most reasonable method of regulating long term compliance 

would be to reduce the capacity factor limit for as long as a deficiency in plant maintenance is 

causing an increase in the emission rate. 

Commenter (9425) stated that EPA should consider limiting the applicability of its rule to 

EGUs with high capacity factors during a particular calendar year.

Commenter (9666) generally supported the proposed applicability exemptions for low capacity 

factor EGUs and small combustion turbines. 

Commenter 9771 believed that EPA should not provide an exemption for units with a capacity 

factor of less than 33 percent, based on a retrospective three year rolling average of operating 

hours. 

Commenter 7976 stated that the proposed 33% CF exclusion stands regulatory incentive on its 

head. It avoids regulation of the undesired high emission rate plants but imposes regulation on 

the desired low emission rate plants.

Response 5.4-1: 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 slidingscale subcategorization approach. This approach provides adequate flexibility for the continued 

use of simple cycle units while simultaneously promoting the installation of more efficient 

technologies. While the EPA found that the one-third electric sales threshold would provide 

adequate flexibility for simple cycle units based on their historical usage, the EPA wanted to be 

responsive to commenter concerns that simple cycle units may be used more in the future to back 

up intermittent renewables. Under the sliding scale, conventional simple cycle turbines will be 

able to sell between 33 and 40 percent (depending on the unit) of their potential electric sales 

before being subject to the base load standard, the best high-efficiency simple cycle turbines will 

be able to sell up to 43 percent of their potential electric output, and fast-start NGCC units will 

be able to sell up to 49 percent of their potential electric output. Requests for 50 and even 60 

percent electric sales thresholds for all units are simply not reasonable. Units selling this much 

electricity to the grid are serving base load demand and should be installing NGCC technology, 

which is both more cost-effective and more efficient at these sales levels.
5-36

Comment 5.4-2: Commenter 6158 stated that EPA should focus on unit output in establishing 

the applicability provisions regardless of whether the unit serves on-site load or delivers 

electricity to the grid. Commenter 8957 stated similar concerns, but added that under the 

proposed regulation, the owners or operators of a power plant that provides 876,000 MWh 

annually only needs to oversize their plants by three times to avoid applicability. Because the 

proposed rule requires a coal-fired plant to oversize by approximately 28 percent and install 

expensive auxiliary equipment in order to provide on-site sequestration at the proposed 40 

percent level, the commenter stated it is more economical for plant owners and operators to 

oversize their potential capacity than to meet the proposed standard.

Commenter 9666 opposed the sales criterion because the commenter is concerned that using a 

sales criterion instead of capacity factor might allow industrial facilities to avoid compliance 

with this rule despite the fact that they operate at capacity factors as high or higher than EGUs 

selling to the grid; the commenter does not understand the rationale of a policy that would allow 

the owners or operators of large industrial NGCC units to circumvent the purposes of this rule. 

Commenter 9666 was also concerned that using a sales criterion instead of capacity factor might 

allow industrial facilities to avoid compliance with this rule despite the fact that they operate at 

capacity factors as high or higher than EGUs. The commenter stated that as proposed, a large 

NGCC unit located at a facility might operate at a very high capacity factor (e.g., 90 percent or 

more) and not have to comply with the GHG NSPS because most of its generation is used onsite 

and it does not trigger the one-third sales criterion. The commenter stated that they don't 

understand a policy that would allow the owners or operators of large industrial NGCC units to 

gain compliance with this rule. 

Commenter 10520 stated that they support the one-third sales criteria, however, they are 

concerned that using a sales criterion instead of a capacity factor limit might allow industrial 

facilities to avoid compliance with this rule. The commenter stated that, as proposed, a large 

NGCC unit located at an industrial facility might operate at a very high capacity factor and not 

have to comply with the GHG NSPS because most of its generation is used on site and it does 

not trigger the one-third sales criterion. 

Response 5.4-2: The intent of the applicability criteria in this final rule is to cover EGUs whose 

primary purpose is to sell electricity to the grid, not industrial CHP units. The applicability

criteria in this final rule accomplish that goal.

Comment 5.4-3: Commenter 9514 stated that EPA refers to "capacity factor" as an EGU's 

threshold energy output (MWh) to the grid. See 79 Fed. Reg. at 1459. The commenter felt 

that this is an odd use of the term capacity factor, which typically refers to the actual operation of 

a unit compared to its potential over a given stretch of time. For instance, if a unit operates at 80 

percent load for 8,760 hours in a year, it would have an 80 percent capacity factor. Similarly, if a 

unit operated at full load for 7,008 hours, it would also have an 80 percent capacity factor.

Commenter 9514 found the EPA's use of the term "capacity factor" at 79 FR 1459 inconsistent 

with previous definitions of this term under 40 CFR Part 60.
5-37

Response 5.4-3: The EPA agrees that our use of capacity factor in the proposed rule was not 

ideal. Our use of capacity factor refers to the amount of potential electric output supplied to a 

utility power distribution as the capacity factor. This is a shorthand for the percentage electric 

sales threshold. However, capacity factor can also be calculated based on hours of operation or 

the amount of heat input. Both of these approaches approximate, but not match the actual 

relevant threshold which is based on the percentage of electric sales relative to the potential 

electric output. In fact, in the proposed rule the EPA approximated the number of existing simple 

cycle units potentially impacted by the one-third percentage sales criterion, which overestimated 

the number of potentially impacted units. In this final rule, we have tried to consistent use 

percentage electric sales and not capacity factor.

Comment 5.4-4: Commenters (7994, 8952, 8973, 9426, 9666, 9678, 9777, 9779, 9780, 10023, 

10048, 10100, 10392, 10554, 10876) supported exclusion of electricity generated as a result of a 

grid emergencies from counting as net sales when determining applicability, and commenter 

10100 also supported the definition of "system emergency" as "any abnormal system condition 

that the Regional Transmission Organizations (RTO), Independent System Operators (ISO) or 

control area Administrator determines requires immediate automatic or manual action to prevent 

or limit loss of transmission facilities or generators that could adversely affect the reliability of 

the power system and therefore calls for maximum generation resources to operate in the 

affected area, or for the specific affected facility to operate to avert loss of load." Commenter 

10100 believed this definition is appropriate because the benefits of operating these units to 

generate electrical power during emergency conditions outweigh any adverse impacts from 

short-term increases in CO2 emissions by units lower in the dispatch order. 

Commenters (9513, 9514, 8911) opposed the exclusion of grid emergencies when calculating a 

source's net electricity sales for rule applicability purposes because section 111 emission 

standards must apply continuously even during grid emergencies, and that EPA does not have 

the necessary authority under the Clean Air Act to suspend applicability of the standard during 

these periods. Commenter 9513 believed the proposed exclusion of grid emergencies is also 

unnecessary, as EPA already possesses an effective mechanism to address this issue while 

avoiding conflicting outcomes and unintended consequences: the EPA Assistant Administrator 

for Enforcement is delegated the authority on behalf of the United States to advise a source that 

the government would not sue the source for taking certain actions during an emergency. The 

commenter stated that this authority has been used in a variety of circumstances and provided 

specific examples.

Commenter 10876 stated that electricity that is generated in response to a grid emergency 

declared by a regional transmission organization (RTO), independent system operator (ISO), or 

control area administrator should be exempted from the amount that is used to determine net 

sales for EGU applicability. The commenter stated that this proposal is consistent with 

approaches that EPA has recently applied to its rulemakings for the Mercury and Air Toxics 

Standards (MATS) rule and the National Emission Standards for Hazardous Air Pollutants 

(NESHAP) for Reciprocating Internal Combustion Engines (RICE units). Such an approach 

should also be applied to the new unit rules. 
5-38

In conjunction with the prospective purpose criteria, Commenter 10098 supported an 

"emergency conditions exemption" and requested that the EPA formulate a clear definition of 

what constitutes a "grid emergency."

Response 5.4-4: 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 5.4-5: Commenters (8937, 9320, 9425) stated that the EPA should expressly exclude 

periods of operation when combustion turbines fire permitted back-up fuels such as fuel oil, 

alternatively, EPA should further analyze CO2 emissions during oil-fired operations and propose 

an NSPS that adequately accounts for such periods or re-evaluate, develop and propose a 

separate standard for dual-fuel units that accommodates partial load operations, specific unit 

design, and operational site characteristics. Commenter 9425 stated that the use of oil as a 

backup fuel is relatively infrequent and that units also are typically subject to operating limits in 

air permits that restrict usage of oil while recognizing the importance of backup fuel operation. 

The commenter went on to say that some units may be forced to bum oil for an extended period 

of time, during extended shutdowns of natural gas production facilities in the Gulf of Mexico 

following a major hurricane. The commenter expressed concerns that this situation would result 

in significantly higher CO2 emission rates than allowed by the NSPS standard and preclude 

compliance. Therefore, the commenter suggested that the final rule provide an explicit 

exemption for periods when the use of a backup fuel is required to maintain grid reliability. 

Commenter 9320 a utility operator in Florida stated that the proposal failed to adequately 

consider the need for new combined-cycle CTs to operate on oil as a back-up fuel when natural 

gas is curtailed or supplies are disrupted during emergencies, such as hurricanes; this commenter 

stated that if use of backup fuels is not categorically excluded a specific standard for use of such 

fuels should be established. 

Commenter 9780, 10095 stated that EPA also needs to address the fact that there are units that 

combust natural gas normally, but could be required to combust oil during energy periods. The 

commenters stated EPA should exempt from any compliance averaging calculation emissions 

that result when an NGCC unit runs on backup fuel oil to address emergency conditions as long 

as those periods comprised 10 percent or less of the unit's heat input over a three-year period. 

Commenter 8937 requested that the final rule address use of backup fuels during periods of 

natural gas curtailment, and the commenter recommended that the final rule exempt periods 

when a unit must operate on backup fuels.

Commenter 6505 recommended eliminating the compliance requirement for the periods of time 

when a unit is combusting secondary fuels, such as fuel oil, but still consume >90% natural gas 

on a 3 year rolling average. The commenter stated that this creates the possibility for an 

otherwise extremely efficient combustion turbine being precluded from service during reliability 

critical events.

Commenter 9591 interpreted the proposed provisions under 40 CFR 60.4305(c)(4) related to the 

90% threshold for use of natural gas to mean that any oil fired in a turbine would be included in 

compliance calculations unless oil use exceeded the proposed 10 percent threshold on a rolling 
5-39

three-year basis. The commenter believed this language indicates a unit using more than 10 

percent oil would be considered oil-fired and not covered by the proposed rule. The commenter 

also agreed with the EPA's assumption that new, primarily oil-fired turbines are unlikely to be 

constructed. 

Response 5.4-5: Affected combustion turbines burning 10 percent or more non-natural gas are

subject to the emission standard for the multi-fuel-fired unit subcategory. This emission standard 

is based on the use of clean fuels, and is readily achievable by all combustion turbines burning 

distillate oil. 

Comment 5.4-6: Commenter 8952 asserted that the 2001 to 2012 simple cycle generating data 

that the EPA used to characterize typical capacity factors for simple cycle turbines is atypical 

because these data included a severe economic recession and an expansion of energy

conservation programs. Commenter 8952 stated that the 3 year averaging period has a limited 

benefit because capacity is forward-looking, and one year of high demand decreases the 

available margin over the next 2 years.

Commenter 9665 used the capacity factor limits from 35 recent simple cycle permits as the basis 

for objecting to the EPA's use of an historical analysis to estimate that "approximately one 

percent" of new simple cycle turbines will be affected by the proposed rule based on the onethird sales criterion. Commenter 10095 identified 19 simple cycle units with annual capacity 

factor permit limits ranging from approximately 40 percent to 55 percent. Commenters (9665, 

10095, 10098) do not believe that the EPA's historical analysis of simple cycle capacity factors 

provides the substantial evidence that is required to support the proposed standards. Commenter 

8952 also provided data showing the current unprecedented rate of retirements of steam plants. 

Commenters (8952, 10098) believed that this accelerated rate of retirement could drive system 

operators to select the faster construction schedules associated with simple cycle turbines to 

maintain grid reliability until more cost-effective combined cycle units can be constructed. 

Commenters (8952, 9665) pointed out that regional grid operators compensate generating 

facilities not only on the amount of energy that they actually deliver to the grid, but they also 

compensate generators based on the amount of capacity the generator has readily available to the 

dispatcher to respond to emergent conditions. These commenters indicated that the one-third 

sales criterion will decrease the reserve capacity that can be bought and sold in these capacity 

markets; they believed this criterion is burdensome and that it highlights the fact that there is no 

compliance technology available for the end-users of simple cycle technologies because the 

method of control is essentially achieved by limiting the operation of the facility. Commenter 

9665 believed that within capacity markets, the proposed capacity factor limit on simple cycle 

gas turbines will act as an incentive to install modularized sets of reciprocating engines (which 

are subject to no capacity factor limitations under the NSPS), resulting in significant financial 

impact to owners of simple cycle units participating in those capacity markets. 

Response 5.4-6: The EPA notes that the applicability criterion in question is based on the 

percentage of electric sales relative to potential electric output, not capacity factor. The EPA 

conducted extensive analysis on the historical percentage of electric sales for simple cycle 

turbines and has concluded that the sliding-scale approach provides sufficient flexibility for the 

continued use of simple cycle turbines. 
5-40

Comment 5.4-7: Commenter (9427) asked why applicability criteria were proposed on a net 

megawatt hour basis while the emissions standards were proposed on a gross megawatt hour 

basis. This commenter recommended that applicability should be based on potential electric 

output (megawatt hours) of the combustion turbine and the actual gross electrical output of the 

combustion turbine. The commenter also recommended that the EPA revise the definition 

of "potential electric output" in section 60.4221 to use the design electric output efficiency of the 

combustion turbine on a gross output (megawatt hour) basis.

Response 5.4-7: The applicability and subcategorization criteria are based on net output because 

that is the defining factor that determines whether a unit is an EGU. However, for the reasons 

discussed in Section III.F of this final rule, the primary standards in this final rule are on a grossoutput basis.

Comment 5.4-8: Commenter 10681 would insert an enforceable condition into an NSR permit 

to assure a unit remains exempt from the requirements of the NSPS.

Commenter 5537 stated to avoid NSPS, the EGU must be subject to an enforceable operational 

limit in its operating permit so that from its initial construction, it is not allowed to exceed any of 

the threshold criteria listed by the EPA at any point in its operating lifetime that would have 

made it subject to NSPS at the time of construction.

Commenters (5537, 9771) believed that in order for a source to avoid applicability of the NSPS, 

the source must be subject to a federally enforceable permit limit with associated monitoring, 

recordkeeping, and reporting conditions for assessing applicability on an ongoing basis as 

required by many federally approved SIPs.

Commenter 10681, a pre-construction permitting authority, responded to the EPA's request for 

input on implementation of the proposed 3 year average sales criterion and stated that the 3 year 

average criterion would become a continuing compliance obligation of the source because a onetime, preconstruction demonstration based on design considerations would not assure that 

operations would not change in the future. Commenter 10681 stated they would insert an 

enforceable condition into an NSR permit to assure potentially affected units remain exempt 

from applicable requirements.

Commenter 9427 was confused by use of a different averaging period for applicability (3 years) 

compared to the averaging period used for compliance (12 months). Commenter 9427 asked, 

does the EPA intend for the operator to wait until the end of first 3-year applicability period is 

satisfied, and then comply going forward; in Title V annual compliance certifications, how can 

an operator certify compliance prior to the end of the first 3-year period; how are applicability

and compliance determined for a combustion turbine that routinely operates above and below 

applicability thresholds over consecutive but overlapping 3-year.

Commenter 9666 stated that without factoring in the impact of the one third sales criterion in the 

compliance analysis, it is not possible to determine achievability of the proposed standards, and 

the commenter found that the methodology for implementing the one-third sales criterion is 

undefined in the proposal. Commenter 9666 found that the inconsistency between the three year 

averaging period proposed for the one-third sales criterion compared to the 12-month period 
5-41

proposed for the CO2 limit caused serious ambiguity in trying to evaluate how the one-third sales 

criterion might affect compliance rates (by exempting some units). Commenter 9666 posed 

several questions related to implementation of the one-third sales criterion and reconciliation of 

the 3-year average exemption criteria (20 to 40%) with the 12-month compliance average to 

evaluate achievability: (1) If a turbine operates less than the 3 year average sales criterion, how 

long does the exemption last? (2) If a turbine is exempt during a three-year period, does the 

exemption continue for an additional 3 years; does the exemption continue through the end of the 

next year; does the exemption continue until the end of the next rolling month compliance 

determination? (3) What compliance determination would the EPA make during the first three 

years if a 12-month violation of the CO2 limit occurs?

Commenter 9666 stated that uncertainty on the preceding implementation issues made it difficult 

to comment on both the associated range of sales criterion suggested by the EPA and 

achievability across the range of CO2 limits included in the proposal.

Commenter 10095 posed a series of questions asking for clarification of applicability criteria. 

Commenter 10095 recommended several changes to the proposal's applicability criteria for 

NGCCs and simple-cycle CTs. If EPA retains the current applicability criteria as proposed, 

clarification is needed to address a range of compliance uncertainties. The commenter reviewed 

EPA's proposed applicability criteria for CTs, and the commenter recommended EPA must 

clarify how these three applicability criteria interact with the proposed 12-operating month 

rolling average compliance requirement. For example, if a CT does not meet the 90 percent 

natural gas criteria, from which 12-operating month rolling average compliance determinations 

are the affected facility excluded?

Commenter 2470 stated that they support the addition of the three-year rolling average 

methodology for determining the applicability of the proposed rule for simple cycle combustion 

turbines.

Commenters (3862, 9425, 9666, 9770, 9777, 10023, 10619) supported the proposed revision of 

the averaging period for electric sales by combustion turbines from an annual basis to a threeyear rolling average basis, and stated that applicability based on the actual capacity factor during 

the preceding compliance period would provide some regulatory clarity for simple cycle units 

that may be periodically dispatched at high capacity factors. Commenters (9425, 9666, 10095) 

also requested that the EPA clarify how the three-year rolling average will be implemented, and 

stated that the final rule should include a full three-year period for the initial compliance 

determination. 

Commenter 10095, a regional electric utility, stated that the proposed one-third sales criteria are 

confusing and problematic for NGCCs because the applicability criteria are evaluated as a threeyear rolling average, but compliance is evaluated on a 12-month basis; the commenter 

recommended that the EPA should revise the applicability criteria for NGCCs to match the 

compliance period for NGCCs. This commenter also requested clarifications on how the EPA 

intends to implement the multiple applicability criteria proposed over differing rolling averaging 

periods.
5-42

Commenter 10095 stated that EPA's applicability criteria are confusing and problematic for 

NGCCs, specifically, the rolling three-year one-third sales criteria. Because the compliance 

period is proposed to be on a 12-month basis while the applicability criteria is a three-year basis, 

The commenter stated that EPA appears to have inadvertently created issues for NGCCs. As 

proposed, NGCCs with single-year sales below one-third of its potential output (or a 33 percent 

capacity factor) could be subject, in that year, to the proposed standard if the surrounding years' 

sales (or capacity factors) were high enough to create a three-year average over 33 percent. For 

example, assume an NGCC operates for three consecutive years with capacity factors at 50, 60, 

and 20 percent, respectively. Absent these alterations, the commenter felt that the proposed 

standard affecting NGCCs is too stringent and unnecessarily restricts operating flexibility.

Commenter 8952 stated that the 3 year averaging period is unfortunately of limited benefit. The 

commenter stated that capacity is forward looking. The commenter stated that an individual year 

of high energy demand, for unforeseen demand or supply issues, would decrease the available 

margin over the next 2 years.

Commenter 9425, 9780 also requested that the EPA clarify whether a simple cycle unit that 

exceeded the sales criterion for a series of compliance periods would be subject to the standard 

only during those discrete compliance periods or would the EPA invoke the "once in always in" 

doctrine for all subsequent 3 year averages. 

Commenter 9425 stated that EPA must address whether simple-cycle units that exceed the onethird sales test would be subject to an emissions limit only for those periods in which sales 

exceeded the limit or, once the test has been failed, would be required to comply for all operating 

periods going forward, regardless of whether sales later return to levels that would entitle the 

simple cycle CT to take advantage of the proposed changes to the applicability requirements.

Commenter 5537 stated that NSPS regulations are intended to be "once-in-always-in" provisions, 

which have always been EPA's policy and practice for other sources, and for other pollutants 

from similar sources. The commenter believed that NSPS applicability should not be "optional" 

in that it may disappear and return from year-to-year. 

Rather than delaying the applicability determination until after beginning operations, Commenter 

5537 stated that NSPS regulations are intended to be "once-in-always-in" provisions, and 

opposed proposed applicability provisions that could change applicability determinations from 

year-to-year.

Commenter 7540 encouraged EPA to ensure that the final rule allows new units this "ramp up" 

period before the rule applies as it is a more accurate representation of actual lifetime 

performance than the first few months. In addition, Commenter 7540 stated EPA should clarify

that the rule does not apply to units that fall below the three-year rolling average threshold, even 

if the unit had previously exceeded the threshold (e.g., the standard is not "once in, always in"). 

Commenter 7540 stated that if a unit's role in the electric system or dispatch profile changes, it 

should no longer be covered by the rule (unless it again exceeds the threshold) and vice versa. 

Commenter 7540 noted that as currently drafted, if a unit were to limit its utilization below the 

sales threshold after initially being subject to the standard, it may continue to be subject to the 
5-43

standard for at least three years as it demonstrates that its three-year sales are below the 

threshold. Commenter 7540 noted that in this situation, they recommend that EPA allow a unit to 

accept a permit limitation exempting it from the standard, rather than having to accumulate three 

years of operating data showing that it no longer meets the applicability provisions.

Commenter 9678 recommended adding a once-in-not-always-in clarification consistent with the 

treatment of emergency generators under 40 CFR Part 63 and consistent with the treatment of 

cement kilns in the recent CISWI rule. Commenter 9678 recommended that units initially above 

the one-third sales criterion should remain eligible for the exclusion during future compliance 

periods with capacity factors below the threshold. Commenter 10100 also recommended that the 

final rule should extend the exclusion to cover other types of units that provide peaking power 

because in addition to combustion turbines, the commenter stated that other types of new units 

can also provide peaking service.

Commenter 9666 stated that the methodology of implementing the less than one-third sales 

criterion is undefined in the proposal. The commenter stated that this causes serious ambiguity 

because the proposed rule is based on a rolling 12-operating month period and determines 

compliance with the CO2 limits after the first 12 operating months, while the one-third sales 

criterion is based on 3-calendar year average sales which would not be calculated until 3 

calendar years of operation had passed. Based on the information provided in the proposed rule, 

the commenter believed that it is not possible to accurately determine which of the turbines that 

EPA evaluated in Docket Item -0082 might have satisfied the one-third sales criterion and 

therefore be eliminated from the achievability analysis. The commenter stated that including this 

one-third criterion in the analysis likely affects the achievability level. The commenter stated the 

analysis performed by EPA did not filter out the turbines that might have met the one-third sales 

criterion, nevertheless, it was considered by EPA to be conservative without quantifying the 

level of conservatism. Without applying this filter to the dataset, the commenter stated it is 

impossible to determine how conservative EPA's analysis is. The commenter stated that the 

question is whether, by including this filter, EPA's conclusions on the level of the CO2 limit for 

compliance would have changed or if the proposed the range of sales criterion (20 to 40 percent) 

is appropriate. The commenter then posed a series of questions for the EPA:

1. If a turbine meets the sales criterion, how long does the exemption last?

a. Only during the 3-year period when the sales criterion was met?

b. If it is exempt for a given period, what is that period?

i. That 3-year period only?

ii. Up until the end of the subsequent 3-year period?

iii. Up until the next calendar year?

iv. Up until the next rolling month compliance determination?
5-44

2. What happens to the compliance determination during the first three years if a 12-

operating month violation of the CO2 limit occurs?

a. Is it subject to penalties and possibly be forced to cease operation at that point?

b. Is it only subject to penalties and possibly be forced to cease operation after the 

first 3-year period has occurred?

Response 5.4-8: The final applicability criteria are based on operating permit conditions and not 

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

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

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

and B for a more detailed discussion, including related issues, such as averaging periods.

5.5 INTEGRATED EQUIPMENT

Comment 5.5-1: Commenters (9514) supported the additional language defining steam 

generating unit to include any integrated equipment that provides useful thermal output to the 

affected facility. Commenters (9514) opposed the additional language defining steam generating 

unit to include any integrated equipment that provides electricity to the affected facility because 

the commenters were concerned that the proposed definition would allow electric power supplied 

by a separate generating source with lower emissions to be used to meet the auxiliary power 

needs of a coal-fired CCS plant to improve the plant's calculated emission rate; the commenters 

believed that such an arrangement would constitute circumvention, and the commenter was

concerned that the proposed revisions for integrated equipment may encourage some operators to 

circumvent the GHG performance standards. Accordingly, commenter (9514) recommended that 

EPA consider language that distinguishes between integral and integrated systems and also 

recommended that the preamble to the final rule include a discussion that provides guidance as to 

how it will apply the circumvention provisions under 40 C.F.R. section 60.12; the commenter 

also expressed concerns about circumvention by IGCC operators that may seek to avoid 

applicability of the rule by segregating the coal gasification process (i.e., seek to modify their 

operations to become segregated gasification combined cycle (SGCC) operators), and the 

commenter provided recommendations to prevent this potential method of circumvention by

IGCC operators. Commenter (9514) also recommended that the relevant appendices to the rule 

should require a source that wishes to construct a configuration not expressly discussed in the 

rule or preamble to seek an applicability determination or alternate compliance demonstration 

approval for such systems prior to commencing construction, and the commenter provided a 

series of potential scenarios to discuss in the preamble of the final rule. Commenters (9514) 

opposed the addition of language to include "co-located non-emitting energy generation included 

in the facility operating permit" because the commenter does not believe that this language is 

consistent with the Congressional intent of section 111 standards: to ensure that new sources are 

built using cutting-edge technology to minimize emissions.

Response 5.5-1: The definition of affected facility in the final rule includes integrated 

equipment. This approach does not circumvent the intent of the rule. The emission standard is 

based on the use of the BSER identified by the EPA. While integrated equipment is not part of 
5-45

the BSER, owners and operators are free to use integrated equipment as an approach to meet the 

emission standard and reduce site-specific costs. 

Comment 5.5-2: Commenters (9733, 10038, 10682) generally supported the proposals 

applicability provisions for CHP plants and establishment of output-based standards. 

Commenter 10682 expressed concerns that the definition of CHP in the rule may be too narrow, 

and unnecessarily limit applicability because some CHP projects produce hot oil, rather than 

steam. Commenter 10682 recommended the final rule should omit the phrase "steam-generating" 

from the definition of CHP. 

Commenters (8952, 10098) opposed the application of the NSPS standard to CHP projects and 

recommended that the final rule include a CHP exemption because such an exemption would 

encourage development of beneficial CHP projects. 

Commenter 10098 stated that application of the proposed standard to industrial, commercial and 

institutional combined heat and power units is arbitrary and capricious, and added that there are a 

number of ways in which EPA could exclude industrial, commercial, and institutional CHP units 

from the proposed rule. Commenter 10098 also stated that an exemption for CHP is necessary

because industrial, commercial, and institutional CHP units are typically customized to suit the 

host's needs and that development of standard compliance calculations is impractical for the 

disparate collection of CHP operations and joint ventures with mixed ownership. Commenter 

10098 also stated that the EPA provided no information in the proposal regarding how many

CHP units were actually capable of meeting the proposed rule's emission limitations. This 

commenter disagreed with the hypothetical CHP example provided by the EPA in response to 

comments from the Office of Management and Budget because the example assumed steady 

state operations. Commenter 10098 also stated that no real-world data on CHP operations or 

emissions was included in the proposed rule or in the RIA and requested that the EPA exclude 

industrial, commercial and institutional CHP units from the rule. Commenter 10098 concluded 

that it would be arbitrary and capricious for the EPA to apply the standard to industrial, 

commercial and institutional CHP with no supporting data in the record. Commenter 10098 

recommended incorporation of explicit exemptions for CHP units at facilities that are classified 

as industrial (e.g., gas-fired CHPs within SIC codes 2911, 13XX, and other industrial SIC codes 

as appropriate). 

Commenter 10098 also stated that EPA should include language excluding from applicability

new, modified or existing cogeneration units (defined as units that simultaneously produce 

power and heat and have an energy savings of 10% or more.) Commenter 10098 stated that the 

final rule should restrict the definition of affected facility to include only industrial-commercialinstitutional cogeneration units that supply, on a net basis, more than two-thirds of their potential 

combined thermal and electric energy output and more than 450,000 MWh net-electric output to 

a utility power distribution system on an annual basis for 5 consecutive calendar years and that 

CHP units which have total thermal energy production that approaches or exceeds the unit's total 

electricity production should be exempted. The commenter went on to describe a number of 

strategies for incorporating an exemption for CHP units including exempting CHP units by fuel 

type and exempting industrial CHP units based on the definition of potential electric output, 

suggesting use of a default efficiency of 50 percent.
5-46

While supporting an exemption for cogeneration facilities, commenter 10606 stated that if the 

EPA is unwilling to grant a blanket exemption for all CHP facilities, then the EPA should grant 

an exemption for all CHP facilities that will use natural gas as their primary fuel, because such 

an exemption will provide relief for the commenter and other similar companies that use clean 

fuel (natural gas), but that cannot readily comply with the proposed standard. The commenter 

added that restricting the exemption to natural gas will ensure the exemption cannot be used to 

construct new coal-fired plants. 

Commenter 9201 summarized the EPA's longstanding practice of differentiating industrial 

cogeneration from electricity generated by public utilities, and the commenter encouraged the 

EPA to continue to differentiate these two types of sources as it moves forward with regulating 

CO2 emissions by relying on the Acid Rain program's definitions as proposed; the commenter 

supported the exemptions for cogeneration and related definitions in the proposed rulemaking. 

Commenter 10038, a proponent of CHP systems, supported the proposed exclusions of facilities 

with design heat input of less than 250 MMBtu/hr, facilities that supply less than 219,000 MWh 

of net electric generation to the utility distribution system, and facilities that supply less than 

one-third of their potential electric output to the utility distribution system, but the commenter 

believed the final rule should further tailor the applicability provisions already in the proposed 

rule to more closely reflect the realities of industrial CHP units by using overall system 

efficiency when calculating potential electric output. The commenter stated EPA should use 

overall system efficiency when calculating potential electric output. The commenter noted that 

the EPA allows facilities to use actual electric efficiency in calculating potential electric output, 

but also noted that the definition of potential electric output only allows facilities to account for 

actual "design electric output efficiency." The commenter believed that as written, CHP facilities 

with very high overall system efficiencies would not meet this definition. The commenter 

recommended that CHP facilities that supply at least 20% of total output as useful thermal output 

should be allowed to make this calculation on the basis of overall system efficiency. 

Commenter 10038 stated that the EPA should adopt applicability criteria excluding all highefficiency CHP units so that all CHP systems with efficiencies above 65%-in addition to the 

other proposed exclusions because this additional criterion would encourage high efficiency

generation with only a very remote possibility that it would encourage a high-emitting new 

generator to add CHP as a means of avoiding applicability of the standard.

Commenter 10038 requested that the final rule clarify design-based vs. operations-based 

requirements in applicability criteria as related to CHP plants because the commenter believed

the proposal was unclear on the interaction between the intended purpose provisions and the 

operational look-back provisions. The commenter stated that the language of the preamble and 

the proposed regulation has resulted in some confusion and provided the following examples: if a 

CHP facility that is designed to supply less than 219,000 MWh net electric output to the grid 

later signs a contract obligating it to supply more than that amount, will the resulting change in 

operations cause the facility to be a covered facility? If a CHP facility that is designed to sell a 

large portion and amount of electricity to the grid is not needed and so actually sells less than 

219,000 MWh net electric output or less than one-third potential electric output, would that 

facility be a covered facility?
5-47

Given the environmental benefits of CHP units and the government's affirmative steps to 

promote increased industrial distributed generation, EPA should exempt industrial, commercial 

and institutional CHP units entirely from the proposed rule.

Commenter 10682 also expressed concerns that the rule does not clearly apply to waste heat to 

power projects, and the commenter encouraged EPA to add a separate definition of waste heat to 

power (WHP) to clarify that incentives that apply to CHP (e.g., the line-loss credit) also extend 

to WHP and the commenter provided a definition of WHP for consideration by the EPA.

Commenters 0829, 10682 supported the proposed applicability provisions excluding units that 

sell to third-party developers and believed these provisions will exempt the vast majority of CHP 

projects from the NSPS because the of the one-third sales criterion included by the EPA and the 

associated exclusion of power purchases from the definition of "net electric output." The 

commenter supported the proposed provisions clarifying that applicability will be based on gross 

electric sales to the utility minus purchased power of the thermal host facility because of the 

substantial upfront cost and ongoing maintenance responsibilities for a CHP or WHP system. 

Commenter 9733 supported the EPA's clarification that a thermal host may be owned by a 

different legal entity than the owner of the CHP, and that applicability of the standard to the 

thermal host will not necessarily make the CHP unit subject to the standard. 

Commenter 9733 supported the EPA's clarification that a thermal host may be owned by a 

different legal entity than the owner of the CHP and the associated clarifications on applicability

for CHP units.

Commenter 9733 believed that the proposal's applicability criteria appropriately exclude most 

forest products industry CHP units from coverage. This commenter believed that the final rule 

should not only continue to exempt those facilities, but should also exempt all CHP units where 

useful thermal output accounts for at least 20 percent of the total useful output as EPA had 

considered in its April 2012 proposed rule because this approach recognizes the environmental 

benefits of CHP and provides additional incentives for CHP construction. This commenter 

asserted that the inherent efficiency of CHP facilities enables them to operate at emission rates 

lower than the proposed standard. Commenter 9733 stated that if the EPA does not agree to 

explicitly exempt all CHP units where useful thermal output accounts for at least 20 percent of 

total useful output, the commenter recommended that the EPA categorically exempt industrial 

CHP units because these units are fundamentally different than electric utility units.

Commenter 9194 supported exclusion of combined heat and power (CHP) units that generate 

greater than 25 MWs with overall efficiencies greater than 70%.

Commenter 9734 stated that EPA should clarify that the addition of a HRSG to an existing CT to 

convert to more efficient NGCC operation will not be covered by the proposed rule. The 

commenter stated that if EPA preserves the ability of electricity generators to convert less 

efficient CTs into highly efficient NGCC units, the goals of the proposed NSPS and reliability

will both be served. The commenter felt that it is counterintuitive to restrict such conversions, as 
5-48

the GHG reductions and reduced fossil fuel consumption should be encouraged rather than 

hindered.

Commenter (9733) supported exemption of industrial CHP plants because they are significantly

different than EGUs. Commenters (9194, 9592) supported explicit exemption of combined heat 

and power (CHP) units that generate greater than 25 MWs with an overall efficiency greater than 

70% because, the commenter asserted, CHP units have been built by several utilities and have 

provided combined heat and power energy with equivalent CO2 emissions well below the 

proposed standard, and the commenter believed it would be counterproductive to apply the GHG 

standard to such CHP sources. Commenter 8952 also recommended specifically exempting 

simple cycle turbines that serve combined heat and power functions.

Commenter (8952) recommended exemption of district heating plants because of their net 

benefit within CHP installations.

Commenter (10098) opposed the EPA's inclusion of industrial, commercial and institutional 

combined heat and power units because combined heat and power units are energy efficient and 

offer significant GHG reduction benefits compared to conventional boilers and because the 

Administration is actively promoting combined heat and power in other contexts, and the 

commenter believed that it is arbitrary and capricious for EPA to impose regulations here that 

could discourage development of new CHP facilities. This commenter also offered methods for 

excluding industrial, commercial, and institutional CHP units from applicability via changes to 

certain definitions.

Commenter 9755 stated that the EPA's proposed regulations would thus incentivize industrial 

users to generate their own onsite power because of the higher costs of power delivered from the 

grid due to the new standards. Commenter 9755 stated when industrial users build on-site power, 

the utility sells less electricity over the same installed infrastructure. Commenter 9755 stated this 

effectively results in having the remaining commercial and residential customers paying a larger 

part of the infrastructure costs, which increases the overall; cost of electricity to commercial and 

residential ratepayers.

Response 5.5-2: As described Section III.D.2 of the preamble to the final rule, the industrial 

CHP exemption has been significantly expanded and is now based permit restrictions limiting 

the amount of electricity that can be sold. The final exemption takes into account 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 a permit restriction limiting annual electric sales to the unit’s design efficiency

multiplied by its potential electric output or 219,000 MWh, whichever is greater. This limits 

applicability to CHP units that sell a significant percentage of their potential electric output. See 

Section III.F.2 of the preamble to the final rule for a discussion of thermal output credit. The 

EPA has concluded that there is no need to specifically identify waste heat to power projects. To 

the extent that these units meet the applicability criteria, they will be subject to the requirements

of the final rule. 

Comment 5.5-3: Commenter (9514) stated that EPA should revise its proposed rule to ensure 

that the individual gas combustion turbines and the HRSG at CCGT plants are not treated 
5-49

separately from the purposes of determining applicability or calculating emissions. The 

commenter stated that to reflect the agency's determination that CCGT is BSER for gas and oilfired EGUs, EPA should set emission limits for gas- and oil- fired EGUs, including the 

combustion turbines and any HRSG that are associated with those turbines, based on the 

demonstrated performance of the best existing and anticipated new CCGTs, rather than setting 

separate applicability emission limits for the combustion turbines and HRSGs that make up 

CCGTs.

Response 5.5-3: The definition of a stationary combustion turbine includes both the turbine 

engine and the associated HRSG.

5.6 BIOMASS FUELS AND THE TEN PERCENT OR LESS FOSSIL

FUEL THRESHOLD

Comment 5.6-1: Commenters (3862, 8957, 9513, 9514, 9780, 10038) generally supported the 

EPA's proposed criteria for use of 10.0 percent fossil fuels on a 3 year rolling average basis 

because this criterion is consistent with the MATS rule and allows biomass-fired units to use 

some fossil fuels for flame stabilization without triggering applicability. Commenter 9514 

recommended also including a 15.0 percent fossil fuel threshold on an annual basis. Commenter 

9513 stated that EPA must resolve the ongoing question of which biomass fuels should qualify 

as renewable resources. Commenter 9780 stated that they supported this functional exemption

for units that would run only during emergencies. 

Commenters (9198, 9592, 9733, 10100) generally supported the exclusion of biomass-fired 

units. Commenter 9774 stated that biomass fuels should not be regulated if co-fired with fossil 

fuel and should be creditable towards meeting the fossil fuel NSPS. The commenter stated that 

biomass CO2 emissions should not be regulated under the NSPS coal CO2 emission limit 

regardless of what portion is fired with coal or other fossil fuels. The commenter felt that doing 

so will only penalize the use of biomass energy when there are many biomass fuels, including 

those harvested under sustainable forestry practices that are beneficial in reducing CO2 impacts 

fossil fuels. The commenter believed that EPA should provide credit from the use of biomass 

fuels towards meeting any fossil fuel CO2 emission limitation. At a minimum, EPA should not 

regulate biomass CO2 emissions under the same rule as the proposed NSPS for coal-fired 

generation or allow states to determine the CO2 neutrality of different biomass fuels.

Commenter (9425, 9780) supported the EPA's intention to exempt EGUs that primarily fire 

biomass, but this commenter believed that the final rule should include an explicit exemption for 

biomass units. Commenter 9596 stated that the EPA should adjust the applicability threshold for 

biomass co-firing.

Commenters (9592, 10100) generally supported exclusion of biomass fired boilers but urged the 

EPA to adopt the biomass exemption as proposed in the 2012 proposal, which would have 

exempted from the NSPS biomass-fired boilers that co-fire with less than 250 MMBtu/hr of any 

fossil fuel. Commenters (9592, 10100) asserted that the biomass exemption in the 2012 proposal 

provides owners with greater operational flexibility than the current proposal's ten percent 

threshold. If the EPA retains the ten percent threshold, commenter 10100 supported use of a 

three year rolling average. 
5-50

Commenter 9194 stated that EPA's proposed modification of this exclusion to cover electric 

generating units burning less than 10 percent fossil fuels does not provide the flexibility afforded 

by the originally proposed 250 MMBtu/hr fossil fuel exemption. Commenter 9194 encouraged 

EPA to retain the original biomass exclusion proposal.

Commenters (9198) opposed the proposed 10 percent threshold for fossil fuels because the 

commenter believed this threshold is too low and that it will significantly reduce the use of 

biogenic fuels. This commenter believed that the EPA should revise the proposed rule to 

properly account for the significant difference between fossil fuel and biogenic sources of CO2

and should increase the applicability threshold for fossil fuels to allow any EGU regulated under 

section 111 to make use of biogenic fuels to lower their CO2 emissions.

Commenter 10606 believed that the proposed threshold of 10 percent for fossil fuels is too low. 

An EGU could fire 20 or 30 percent fossil fuel, with the remainder biomass, and still "primarily" 

fire biomass. NHPC does not believe it was EPA's intent to prevent new, clean, renewable, 

primarily biomass-fired EGUs from being constructed, but that could be the result of the 

Proposed Rule unless it is revised. The CO2 emissions from a biomass-fired EGU are biogenic in 

nature and carbon-neutral, but the CO2 emissions from a biomass-fired EGU (approximately

2,600 lb CO2/MWh) will not comply with the NSPS limit in the Proposed Rule of 1,100 lb 

CO2/MWh, which is based on NGCC technology. Accordingly, EPA should exempt primarily

biomass fired units from the requirements in of the Proposed Rule or establish a higher threshold 

for fossil fuel firing.

Commenter 9596 stated that the EPA should adjust the applicability threshold for biomass cofiring.

Commenter 10195 requested that the EPA clarify the method an operator should use during the 

first three years of operations to determine if a particular unit will meet the 10 percent fossil fuel 

criterion prior to the end of the first three years of operations. Considering the three-year 

applicability criteria, commenter 10195 also asked whether or not an affected facility has a 

compliance obligation during the first three year period, and the commenter also asked if an 

affected facility does not meet the 10 percent fossil fuel criteria, from which 12-operating month 

rolling average compliance determinations is the affected facility excluded? 

Commenter 10136 noted that EPA asks if the 10 percent requirement for fossil fuel heat input 

should be recast to cover plants that were designed to burn fossil fuels. The commenter stated 

that making this change could mitigate the potential for companies to convert their coal-fired 

boilers to wood, as the commenter is doing. Commenter 10136 stated that assuming that as 

presently written, the rule would consider a coal-to-biomass conversion to be a new woodburning plant and thus no longer subject to the fossil fuel-fired EGU NSPS, then making the 

applicability of the rule contingent on what the plant was designed to burn would ensure that 

such plants continued to be covered.

Commenter 9198 stated that EPA's definition of affected facilities will significantly limit use of 

biogenic fuels under both of its proposed rules. The commenter stated that the proposal's low 

applicability threshold for fossil fuel use could severely restrict the future use of biogenic fuels, 

particularly when coupled with EPA's proposal to treat biogenic and fossil fuel CO2 emissions 
5-51

similarly for compliance purposes. The combination of the 10 percent threshold with the failure 

to differentiate between biogenic and fossil fuel emissions will prevent the utilities from 

substituting lower-carbon biomass or biogas fuels as replacements for fossil fuel in new plants or 

potentially in existing plants.

Commenter 8948, 8972, 9002, 9194, 9198, 9409, 9425, 9509, 9592, 9593, 9733, 9774, 10027, 

10035,10045, 10051, 10131, 10606 stated that the EPA should exclude biogenic CO2 emissions 

as carbon neutral for applicability purposes under the rule because it would be arbitrary and 

capricious for EPA to regulate and treat these biogenic CO2 emissions in the same manner as 

fossil fuel emissions before EPA has finalized its scientific review of biogenic CO2 emissions 

and determined even whether they should be regulated as a pollutant under the Clean Air Act.

Commenter 9409 stated that inclusion of biogenic CO2 emissions from co-fired EGUs in the 

final rule would be arbitrary and capricious because the EPA acknowledged in the proposed rule 

pending policy decisions related to accounting for biogenic CO2 emissions from stationary

sources, but, the commenter stated, the EPA inexplicably proposes to regulate biogenic CO2

emissions from co-fired EGUs in the same manner as fossil fuel CO2 emissions, with no 

justification. The commenter urged the EPA to defer regulation under the NSPS of biogenic CO2

emissions from co-fired EGUs at this time and to instead move forward after the broader policy

on biogenic emissions is settled.

Commenter 10031 noted that while the proposal would exempt biomass boilers that meet the 90 

percent threshold, it would not exempt boilers that co-fire with biomass but use more than 10 

percent fossil fuel. The commenter believed biomass sources, including sources that co-fire 

biomass but also use more than 10 percent fossil fuel, should get credit for offsite factors related 

to the carbon cycle (sequestered CO2) for the biomass fuel being combusted at the stationary

source (typically derived from forest-derived woody or agricultural biomass or waste 

materials). The commenter supported the Agency's development of an Accounting Framework to 

evaluate these issues. The commenter stated that EPA should not finalize this rule for Subpart Da 

units until it incorporates the findings of the Accounting Framework and devises an approach 

that would give the proper credit to sources that use biomass at any level of heat input.

Commenter 10100 opposed EPA's suggested approach of using its Accounting Framework for 

Biogenic CO2 Emissions from Stationary Sources to evaluate in the future whether a particular 

type of biomass is carbon neutral. See 79 Fed. Reg. at 1446. The commenter stated that 

the Accounting Framework presents a methodology for applying an "adjustment" to a source's 

CO2 emissions based on a site-specific analysis of how the biomass feedstock was grown and 

harvested. The commenter stated it would be problematic to use the Accounting Framework in 

practice for permitting, emission reporting, or calculating compliance obligations. The 

commenter stated every new biomass EGU would be required to perform a lengthy and 

expensive study applying the methodology, seek EPA approval of its conclusions and proposed 

adjustment factor, and presumably repeat this entire process any time there was a change in the 

plant's feedstock. The commenter believed that this introduces significant uncertainty for

investment in biomass power plants.

Commenter 10100 opposed use of the Accounting Framework for Biogenic CO2 Emissions from 

Stationary Sources to evaluate whether or not a particular type of biomass is carbon neutral 
5-52

because the framework would be problematic to apply in practice as every new biomass EGU 

would be required to perform a lengthy and expensive study applying the methodology, seek 

federal approval, and repeat this process for each change in feedstock; the commenter believed 

that such an evaluation would introduce significant uncertainty for investments in biomass power 

plants.

Commenter 9676 stated that EPA cannot set what is clearly an arbitrary threshold until the 

Agency completes a rulemaking on the GHG accounting of biogenic emissions. To do so would 

ignore the very rulemaking on biogenic emissions that is now pending.

Commenter 10045 noted that a commenter during the rulemaking that led to the 2009 

Endangerment and Contribution Findings asked EPA to exclude biogenic CO2 emissions from 

the Findings on the grounds that they do not contribute to endangerment of health and welfare. In 

its response-to-comments document, EPA rejected that request because: "[A]ll CO2 emissions, 

regardless of source, influence radiative forcing equally once it reaches the atmosphere and 

therefore there is no distinction between biogenic and non-biogenic CO2 regarding the CO2 and 

other well-mixed GHGs within the definition of air pollution that is reasonably anticipated to 

endanger public health and welfare." The commenter strenuously disagreed with that statement 

insofar as Crop-Derived CO2 is concerned, and believed it was a mistake. The commenter stated 

the author of the response failed to recognize that the definitional foundation of the 2009 

Findings, i.e., the 2009 GHG emissions inventory and the underlying IPCC guidelines used to 

develop that inventory, contained the science-based determination that Crop-Derived CO2 is 

inconsequential to the global warming process. The commenter stated that emissions of CropDerived CO2 are indeed different as a scientific matter because they merely return to the 

atmosphere carbon atoms that were present in the atmosphere only a short time beforehand. 

Moreover, EPA otherwise consistently and fundamentally recognized and adopted that principle 

in its 2009 Endangerment and Contribution Findings. Commenter 10045 also stated that even if 

crop-derived CO2 contributed to global warming, which the commenter insisted was not the case, 

then it would be a de minimis contribution and therefore irrelevant. The commenter stated that if 

EPA were to decline to exclude crop-derived CO2 categorically, then the EPA should complete 

its review of SAB's Critique of EPA's Biogenic Accounting Framework during the instant NSPS 

rulemaking and incorporate a default BAF of Zero for Crop-Derived CO2 into the NSPSs' 

compliance system. Commenter 10045 also asked EPA to confirm expressly that an exclusion 

keeps the NSPSs from triggering applicability of the PSD and Title V permitting programs to 

emissions of Crop-Derived CO2. 

Commenter 10045 stated that the indirect (off-site) emissions of biogenic CO2 associated with an 

EGU's combustion of annual herbaceous crop-derived fuel are harmless. Applying the 

conservative assumption that conservation tillage practices are employed in producing the corn 

and corn stover, a study cited in the comment found under all three methods ((i) life cycle 

biogenic carbon balance, (ii) mass balance, and (iii) EPA's Biogenic Accounting Framework), 

including notably EPA's Biogenic Accounting Framework, that the indirect biogenic carbon 

emissions were net negative, i.e., that the full biogenic carbon cycle yields a net sequestration of 

carbon, due primarily to the generation of biochar.

Commenter 10125 stated that the rule will actually increase emissions if it drives construction of 

biopower plants. The commenter stated that coal plants that co-fire wood produce more 
5-53

emissions than traditional coal plants. The commenter stated that it is therefore a good thing that 

the rule counts biogenic emissions toward facility totals, since treating wood as an emissions 

mitigation strategy is completely counterproductive. The commenter also stated that failure of 

EPA to act and recognize the impacts of bioenergy on greenhouse gas emissions could result in 

widespread forest degradation and significantly increased greenhouse gas emissions from the 

power sector.

Commenters 10025, 10106, 10119, 10136 stated that EPA must establish credible greenhouse 

gas performance standards for biomass power plants. As it did in the 2012 Proposed Rule, 

commenters stated EPA has once again failed to propose greenhouse gas performance standards 

applicable to EGUs that primarily fire biomass. These facilities can be very carbon-intensive, 

emitting far more CO2 than coal-fired facilities on a pounds-per-MWh basis; indeed, measured at 

the smokestack, replacing fossil fuels with biomass actually increases CO2 emissions. The 

commenter stated that in light of the high levels of CO2 emissions from biomass-fired facilities -

emissions that warm the climate and endanger health and welfare, regardless of their biogenic 

nature - EPA must either include biomass-fired EGUs within the scope of the present standard or 

determine a separate standard based on BSER for these facilities.

Commenter 9198 commented on the use of biomass as fuel for combustion turbines: "Energy

produced from forest, agricultural and MSW biomass should be one component of an overall 

bioenergy strategy to reduce emissions of CO2 from fossil fuels, and EPA's rules should advance 

rather than hinder that goal. We recognize that statutory and regulatory differences can result in 

significant dissimilarities in program structure and operation. With respect to the EPA's proposed 

approach to biogenic CO2 accounting under the 111(b) program; however, we are deeply 

concerned that EPA's underlying view of the benefits and value of developing biogas and 

biomass projects is not intellectually consistent. EPA's proposal to treat biogenic and fossil fuelbased emissions similarly in determining compliance with the proposed GHG NSPS contradicts 

the Agency's own lifecycle assessments for renewable transportation fuels and other renewable 

energy initiatives. [The commenter] is concerned that EPA's proposal to consider biogenic and 

fossil fuel GHG emissions as equivalent will preclude the Agency's' ability to develop costeffective and flexible compliance options for any power plant, new or existing. In short, this 

approach undermines the fundamental premise of the RFS2 program and the goals of 

Congressional and Administration programs to promote renewable energy and fuel production. 

For these reasons, we strongly urge EPA to reconsider the proposed approach and to provide a 

level playing field for biogas and MSW biomass and other renewable energy projects. Such an 

approach is reasonable, consistent, and harmonizes with EPA's efforts to reduce CO2 emissions 

from power plants."

Response 5.6-1: 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.

EPA developed the revised draft report, Framework for Assessing Biogenic CO2 Emissions from 

Stationary Sources, to continue advancing our understanding of the role the use of biomass can 

play in strategies to address greenhouse gas emissions. Specifically, the Framework was 

developed as a policy-neutral framework for assessing biogenic CO2 emissions from stationary

sources—it was not developed as technical guidance in conjunction with any specific policy or 
5-54

program. The revised Framework, and the EPA’s Science Advisory Board (SAB) peer review of 

the 2011 Draft Framework, finds that it is not scientifically valid to assume that all biogenic 

feedstocks are “carbon neutral” and that the net biogenic CO2 atmospheric contribution of 

different biogenic feedstocks generally depends on various factors related to feedstock 

characteristics, production, processing and combustion practices, and, in some cases, what would 

happen to that feedstock and the related biogenic emissions if not used for energy production.

For more information regarding the Framework, see: 

http://epa.gov/climatechange/ghgemissions/biogenic-emissions.html

Comment 5.6-2: Commenter 9198 commented on the use of landfill gas as fuel: "It is difficult 

to reconcile EPA's approach in the 111(b) proposal with the White House's commitment to 

reduce further methane emissions. If the climate impacts of LFG emissions are not properly 

accounted for, biogas and MSW energy projects will be unable to demonstrate CO2 reductions 

and would thus be, ineligible compliance options to assist power plants regulated under Section 

111. If EPA treats renewable biogas and MSW differently than other renewable energy sources, 

it will eliminate these proven, reliable and cost-effective compliance options under the new 

source performance standard or potentially in state plans developed under 111(d). EPA's Office 

of Transportation and Air Quality has evaluated MSW and landfill gas as feedstocks for the 

production of renewable transportation fuels, and concluded that it is appropriate to treat the 

biogenic portion of the MSW and LFG feedstocks as carbon-neutral. Landfill gas is now 

considered an advanced biofuel, moreover, in recognition of its reduction of lifecycle GHG 

emissions of at least 60 percent below the petroleum fuel it replaces, and because it is largely 

cellulosic in derivation, EPA has recently proposed that it be reclassified as a cellulosic biofuel. 

The biogenic portion of MSW that has undergone reasonably practicable separation of recyclable 

materials has likewise been determined to be a renewable feedstock for low carbon fuels, such as 

cellulosic ethanol. Without recognition of the different GHG impacts of these biogenic 

emissions, stationary and mobile sources of GHG will have no incentive to switch to renewable, 

lower carbon energy sources."

Commenter 10131 supported exemption of units that burn landfill gas because, the commenter 

asserted, combustion of landfill gas does not contribute to global climate change. The commenter 

opposed provisions that apply the same accounting method for biogenic CO2 emissions as for 

fossil CO2 emissions.

Commenter 10027 urged EPA to develop accounting procedures that assign the CO2 released 

from the decomposition of biogenic waste in landfills, compost facilities, or anaerobic digesters a 

biogenic accounting factor (BAF) of zero. Commenter 10027 stated this assignment is consistent 

with the recommendations of the Science Advisory Board (SAB) impaneled on this subject. 

Commenter 10027 stated the SAB also noted that management of municipal solid waste (MSW) 

and landfill gas (LFG) posed no land use changes or reductions in carbon stocks not already 

attributed to the manufacturer of the products subsequently discarded.

Response 5.6-2: The applicability criteria in the final rule includes combustion turbines that are

capable of selling greater than 25 MW-n to the grid, are connected to a natural gas pipeline, and 

that are not subject to a permit resting annual fossil fuel use to 10 percent or less of the annual 

capacity factor. A landfill gas-fired unit not that does not meet any one of these criteria would 

not be subject to the requirements of the final rule. In the unlikely event that a landfill gas (or
5-55

anaerobic digester gas)-fired unit meets the applicability criteria, the applicable emission 

standard will be the multi-fuel-fired unit standard. This standard is based on the use of clean 

fuels. These facilities would use the procedures in part 98 of this part to determine the average 

net CO2 emission rate for the fuels burned during the 12-operaitng-month period.

EPA developed the revised draft report, Framework for Assessing Biogenic CO2 Emissions from 

Stationary Sources, to continue advancing our understanding of the role the use of biomass can 

play in strategies to address greenhouse gas emissions. Specifically, the Framework was 

developed as a policy-neutral framework for assessing biogenic CO2 emissions from stationary

sources—it was not developed as technical guidance in conjunction with any specific policy or 

program. The revised Framework, and the EPA’s Science Advisory Board (SAB) peer review of 

the 2011 Draft Framework, finds that it is not scientifically valid to assume that all biogenic 

feedstocks are “carbon neutral” and that the net biogenic CO2 atmospheric contribution of 

different biogenic feedstocks generally depends on various factors related to feedstock 

characteristics, production, processing and combustion practices, and, in some cases, what would 

happen to that feedstock and the related biogenic emissions if not used for energy production. 

For more information regarding the Framework, see: 

http://epa.gov/climatechange/ghgemissions/biogenic-emissions.html

5.7 CODIFIED RULE UNDER SUBPART TTTT AND KKKK, AND

APPLICABILITY FOR SUBPART KKKK UNITS

Comment 5.7-1: Commenter (4867) pointed out the benefits of codifying applicability of the 

standard under a single NSPS source category (proposed new subpart TTTT) rather than under 

separate source categories (subparts Da and KKKK). Commenter 4867 believed that the decision 

to codify applicability of the efficiency standard to both coal and gas-fired EGUs under a single 

subpart (i.e., under a single section 111(b) category) has far-reaching implications for future 

existing source guidelines put forth under section 111(d), because the commenter believed, that 

grouping coal- and gas-fired EGUs into a single category is a pre-requisite for deployment of 

GHG trading programs within state implementation plans under section 111(d).

Commenter 7540 stated that the use of Existing Subparts EPA proposes separate standards based 

on EGU type; one for units regulated under Subpart Da and two for units regulated under 

Subpart KKKK. Commenter supported separate standards for sources currently regulated under 

Da and KKKK, provided EPA determines that this structure would not prevent states from 

proposing compliance programs that allow averaging and trading between sources in Subparts 

Da and KKKK under future section 111(d) regulation of existing sources. Commenter stated 

however, if EPA determines the use of separate Subparts would limit trading and other flexibility

options available to states for subsequent regulation of existing units under 111(d), the Clean 

Energy Group would support development of a new subpart (TTTT) that includes the proposed 

performance standards for new boilers and combustion turbines. In supporting the maintenance 

of this flexibility, the commenter was not recommending a specific structure for an existing 

source standard.

Response 5.7-1: See Section III.B of the preamble for a discussion of why the EPA is finalizing 

a new subpart TTTT for this NSPS rulemaking.
5-56

Comment 5.7-2: Commenter 9427 stated that under Subpart KKKK, the EPA should 

incorporate applicability provisions for configurations with two combustion turbine-generators 

and a common steam turbine-generator so that applicability and compliance can be determined 

on a combined basis if this option is selected by the operator. Under this option, the commenter 

suggested that the applicability criteria for such "2X1" configurations under proposed section 

60.4305 would likewise be determined on a combined basis, doubling the actual electric output 

applicability threshold to reflect two combustion turbines. 

Commenter 9427, a municipal electric power authority, stated that the final rule should not 

require a plan approved by the administrator when apportionment is used as proposed under 

section 60.4373(e) because a common design is where steam from several heat recovery steam 

generators (HRSGs) associated with stationary combustion turbines is directed to a single steam 

turbine that drives a steam turbine electric generator. The commenter stated that the regulatory

text should be clarified by revising it to read "serve a common electric generator or a common 

steam turbine with an electric generator..." The commenter went on to say that stationary

combustion turbines are already required by Part 75 to measure heat input, including heat input 

to duct burners at associated HRSGs. The commenter stated allocating gross output (MWh) of a 

common steam turbine electric generator by using heat input to combustion turbines and 

associated HRSGs would be a very straightforward process and should be allowed without the 

need for a plan approved by the Administrator, and the commenter recommended that the end of 

the first sentence in proposed 60.4373(d) be revised by adding the words "and any associated 

steam turbine electric generator."

Response 5.7-2: For this rulemaking, the affected facility is each stationary combustion turbine. 

See definition in section 60.5580. We understand the point raised by the commenter, as many 

NGCC units are being constructed in two-on-one and three-on-one configurations. In the future, 

we may allow emissions averaging for power blocks, but for now, we are requiring that 

generation (gross or net) be apportioned to the units according to the fraction of total steam load 

or the fraction of combined heat input. See section 60.5535 (e) of the rule for the compliance and 

monitoring procedures for two or more affected EGUs that share a single steam generator. 

Comment 5.7-3: Commenter 9591 urged the EPA to consider interactions between the proposed 

Subpart KKKK revisions for criteria pollutants and the proposed provisions for CO2 to avoid 

conflict with this rule's intended focus on entirely new units. The commenter stated that the 

definition of stationary combustion turbine proposed in August 2012 for the criteria pollutant 

amendments is inconsistent with the definition in the proposed standard for CO2. The commenter 

urged the EPA to ensure these revisions do not conflict, nor have unintended effects.

Response 5.7-3: The EPA notes that the proposed August 2012 amendments to the criteria 

pollutant NSPS for combustion turbines has not been finalized. Further, while the EPA often 

tries to harmonize different rulemakings, this is not always practical or appropriate. The EPA 

will consider the requirements in this final rule when amendments are finalized to the 

combustion turbine criteria pollutant NSPS. 

Comment 5.7-4: Commenter 10681, a permitting authority with numerous small and medium 

sized simple-cycle generators used for load following and intermediate loads, considered the 

proposed applicability criteria in conjunction with current permit limits on hours of operations; 
5-57

this commenter anticipates that the proposed rule will result in deployment of many more of the 

smaller combustion turbines and large reciprocating engines due to their simplicity to permit, 

install, and operate, in spite of their higher lb CO2/MWh emission rates. This commenter 

believed that that environmentally, the use of combustion turbines is superior to the use of 

internal combustion engines for generation of electricity. This commenter also suggested that the 

EPA continue to utilize the current definitions of simple and combined cycle turbines already

contained in subpart KKKK and used for applicability.

Response 5.7-4: The EPA disagrees that the requirements of this final rule will discourage the 

development of new simple cycle combustion turbines. The flexibility provided by the slidingscale approach and the non-base load emission standard will minimize the burden for new simple 

cycle combustion turbines.

Comment 5.7-5: Commenter 1637 urged the EPA to give greater weight to the notion of a "best 

SYSTEM of emission reduction" as required by Clean Air Act Section 111(a)(1). Commenter 

stated that EPA should take that to include the upstream supply system of the fuel. Commenter 

stated that it is unclear that "affected facility" under NSPS Subpart OOOO includes more than 

those involving hydraulic fracturing or that Subparts VV or VVa extend to all natural gas supply

sources, upstream to the wellhead. Commenter noted that in addition EPA should proceed to 

develop and issue for comment a proposal for regulation under Section 111(d) of greenhouse gas 

(GHG) emission leaks from the existing supply systems for natural gas. Commenter noted that in 

addition EPA should require that each affected facility under the proposed additions to Subpart 

KKKK should be required to obtain from their natural gas supplier a copy of their reports under 

the GHG reporting rule 40CFR98 Subpart W, in order to calculate the equivalent CO2 emissions 

from leaks in their supply system for the gas they receive and to report to EPA those equivalent 

emissions along with their reporting of their own emissions. Commenter noted that they 

are not advocating that EPA must include these equivalent emissions in their calculation of their 

allowed emissions, but the commenter believed that EPA must establish baselines in order to 

meet the mandate of Section 111(a)(1) to allow "any cleaning of fuel or reduction in the 

pollution characteristics of the fuel after extraction and prior to combustion may be credited, as 

determined by the Administrator, to a source that burns such fuel."

Response 5.7-5: The EPA disagrees with this comment. The “system” in BSER refers to a 

system that reduces emissions from the source, not a system of emissions that cumulatively

results from upstream and downstream activities. As such, the EPA is not regulating other 

sources of emissions besides affected EGUs in this rulemaking.