Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

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Environmental Protection Agency (EPA): Proposed Rule

Cross-State Air Pollution Rule for the 2008 Ozone 

National Ambient Air Quality Standards

RIN 2060-AS05

General Comments

1. Reviewer recommends updating the discussion for the final Ozone NAAQS that have 

been completed.

EPA Response:

Per the commenter’s suggestion, EPA updated the 2015 ozone NAAQS sections. Among 

other points, the updates reflect:

o Timing of designations.

o Steps taken under this rule to reduce interstate ozone transport will help states 

attain and maintain the 2015 ozone NAAQS. 

o Transport SIPs to address the 2015 ozone NAAQS would be due 3 years after 

promulgation. Specifically, these SIPs will be due Oct. 1, 2018. 

2. Recognizing that the modeling was done prior to the budgets being invalidated by the 

D.C. District Court, reviewer recommends that a minimum providing a more complete 

discussion of how the baseline without the phase 2 ozone season emission budgets would 

influence the benefits and costs of the rule.

EPA Response:

This proposal is a single regulatory action that achieves two purposes simultaneously – it 

addresses transport obligations under the 2008 ozone NAAQS while also addressing the 

remanded ozone-season NOX budgets. The costs and benefits quantified for this single 

regulatory action compare the world without this action (base case), and with this action 

(policy case); therefore, the estimated costs and benefits already reflect the impacts of 

addressing the remanded ozone-season NOx budgets.

3. Reviewer recommends requesting comment on higher cost thresholds greater than 

$3,400/ton that would require some installation of new SCRs/SNCRs, including 

requesting comment on the appropriate timetable/phase-in needed to accommodate new 

installations.

EPA Response:

EPA will request comment on higher cost thresholds per the commenter’s suggestion.

EPA examined higher cost thresholds and found few additional significant abatement 

technologies available beyond those identified at $3,400. However, EPA will clarify that 
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

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it is taking comment on the representativeness of the $3,400/ton cost threshold for the 

described technology. EPA believes 2017 is the most appropriate timeframe by which to 

require compliance with the proposed budgets as it aligns with the attainment date for the 

2008 ozone NAAQS, consistent with instruction from the court in North Carolina v. EPA 

and Clean Air Act section 110(a)(2)(D)(i)(I) as described on page 16 of the preamble.

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EPA is taking comment on the 2017 compliance timeframe and the control feasibility for 

that timeframe on page 122. EPA requests comment on the $3,400/ton value on page 126.

4. Reviewer recommends requesting comment on the potential to cover non-EGU sources 

as part of this rulemaking. To the extent that there are non-EGU lower-cost methods of 

compliance, this would imply that the rule is not cost-effective. This appears to be a 

significant omission and inconsistent with the analysis within the latest ozone NAAQS, 

which includes other control strategies.

EPA Response:

Per the commenter suggestion, EPA will request comment on the potential to cover nonEGU sources as part of this rulemaking. EPA notes that the rule assesses what controls 

are cost-effective at $1,300/ton by 2017 in order to provide reductions in a timeframe 

aligned with the attainment date for the 2008 ozone NAAQS, consistent with the D.C. 

Circuit’s instruction in North Carolina. EPA’s initial assessment is that controls at nonEGU sources are not feasible within this timeframe even though they may ultimately 

prove to be less than $1,300/ton over a longer timeframe. EPA expects to consider these 

abatement measures at a later time as this proposed rule would not fully address interstate 

transport with respect to nonattainment and maintenance issues in downwind states. 

Consistent with the comment, the preamble requests comment on the non-EGU 

assessment on page 130. The non-EGU TSD has detailed information on control costs 

and feasibility of control installation in the proposed 2017 compliance timeframe. The 

TSD is consistent with the analysis done within the 2015 ozone NAAQS.

5. Reviewer recommends removing the “state of the art combustion controls” measure. 

Specifically, the reviewer believes that EPA’s assumption that “state of the art 

combustion controls” (i.e., low NOx burners and overfire air) can be installed and 

operational within 6 months is much too optimistic. While this equipment is proven and 

readily available, it is complex and must be tailored to each particular boiler type, size, 

and fuel properties and integrated into the unit’s digital electronic control system. Time 

must be allowed for engineering analysis and design, procurement, bid evaluation and 

selection, manufacturing, installation, and tuning. An outage window of several weeks is 

also required for installation. Reviewer recommends providing for 18 – 24 months or 

more to install new low NOX burners and overfire air on a utility boiler. Since the 

majority of utility units in the CSAPR states have already installed low NOx burners and 

 

1 Note – page numbers referenced in responses pertain to initial preamble and RIA versions submitted.
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

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in many cases overfire air, the reviewer does not believe that removing this provision will 

have a significant effect on the final state emission budgets.

EPA Response:

EPA does not agree that removing the “state-of-the-art” combustion controls measure is 

necessary. However, it will modify the language to replace “within 6 months” to 

“consistent with the timeframe of this rulemaking and its compliance dates” as sources 

are expected to have more than six months between signature and the beginning of the 

compliance period. EPA will also add additional citations and supporting language on 

page 127 regarding the feasibility of installation of these controls on the proposed 2017 

compliance timeframe. Moreover, this rule does not impose any technology requirement 

by 2017. Sources have the flexibility to comply through a variety of methods such as 

running existing installed controls or buying allowances. 

Even though not required, if sources choose to install/upgrade combustion controls by the 

2017 ozone-season, EPA believes there is historical precedent indicating that sources can 

make such modifications within that timeframe. These controls are fully proven, widely 

used, and with a reasonable effort can be procured, designed, installed, tested and be in 

operation on any coal-steam EGU in less than one year. Since Low NOx burner and/or 

overfire air is a mature technology requiring a short time to complete installation, the 

Agency concludes that sufficient time exists for EGU owners to select this option for 

compliance. Construction time requirements for installing combustion controls were 

examined by the EPA during development of previous CSAPR rulemaking and are 

reported in the TSD for that rulemaking entitled; “Installation Timing for Low NOx 

Burners (LNB)”, Docket ID No. EPA-HQ-OAR-2009-0491. EPA will take comment on 

the timing feasibility of these controls.

6. Reviewer recommends providing additional clarification on how the allowance bank has 

reached the size that it has and has not been more fully used. 

EPA Response:

Per the commenter's suggestion, EPA will add some more description to its explanation 

already present on page 179. The allowance bank discussed in the preamble is an 

estimate, as the size of the actual allowance bank will not be known until post 2016. The 

estimate was developed using recent historical emissions data relative to the budgets to 

calculate the total unused allowances anticipated after the 2015 and 2016 ozone season. 

As described on page 179, the allowance bank is anticipated to occur due to quantities of 

excess allowances resulting from both market forces (e.g., observed gas prices lower than 

originally forecasted natural gas prices) and the tolling of the CSAPR implementation 

(2012 budgets were not applied until 2015). During this three year delay, turnover in 

fleet put downward pressure on NOx emissions and helped push fleet-wide emissions 

below their budgets initially designed for 2012. 
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

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7. Reviewer recommends requesting comment and evaluating the full spectrum of the 

allowance bank, including ratios of 3-to-1 and 4-to-1.

EPA Response:

Consistent with the comment, EPA is requesting comment on page 186 of more or less 

restrictive approaches (e.g., different surrender ratios) to address the allowance bank.

EPA does not plan on any additional evaluation at this time other than what is outlined on 

page 180 of the preamble that resulted in the proposed 4:1 surrender ratio.

8. Reviewer recommends providing additional discussion around the uncertainty 

engendered from allowances banked from 2015 and 2016. Similarly, it would be useful 

to know why the 4-to-1 ratio based on the ratio of the anticipated allowance bank in 2017 

to the ozone season variability limit is the right approach to use. Are there modeled 

results that support this choice? 

EPA Response:

The proposed trading ratio for banked allowances is the product of analysis of recent 

historical emissions data relative to the budgets to estimate the total unused allowances 

anticipated after the 2015 and 2016 ozone seasons. EPA is taking broad comment on the 

treatment of banked allowances and the analysis leading to the proposed 4:1 ratio. The 

concerns about the banked allowances lies in their ability to reduce the effectiveness of 

the 2017 emission budgets. If EPA permits use of the banked allowances at a 1:1 ratio, 

regional emissions would be expected to significantly exceed the collective 2017 

emissions budget and the ozone-season trading program would not achieve necessary 

emissions reductions to address downwind air quality.

EPA believes that a carryover of banked allowances equal to the variability limit was 

appropriate. The variability limit expects the upper bound variation in emissions EPA 

would expect in any given year. Thus, carryover of one year’s worth of allowances 

provides the affected fleet with the ability to accommodate yearly variation from the 

mean in its load and emission patterns, while balancing the need to ensure that emissions 

are reduced, on average, to the level of the budgets and within the assurance levels in 

subsequent years.

9. When considering EGU NOx mitigation strategies, EPA includes generation shifting to 

lower NOx-emitting EGUs as a mitigation strategy. EPA limits shifting generation to 

units with lower NOx emission rates within the same state due to the near-term 2017 

implementation timing for this proposed rule and takes comment on this limitation. 

Given the regional nature of the power sector, is there a reason to include such a 

limitation?

EPA Response:
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

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Consistent with EPA's approach to anchor budgets in state-level historical generation 

values, EPA does not feel it is appropriate to codify the near-term interstate generation 

shifting projections of a model directly into an emissions budget for this rulemaking. The 

model is a least-cost linear dispatch model that reflects perfect foresight over a 40 year 

time frame. There may be some non-economic and out-of-merit order dispatch variables 

at the state level not recognized by the model, but particularly relevant to the near-term 

time horizon relevant for this rule's compliance period. Consistent with the comment, 

EPA request stakeholder comment on imposing this limitation on page 129.

10. Reviewer recommends requesting comment on other approaches to allocations besides 

based on historical heat input and historical emissions (with set-asides) for 2017 in 

addition to later compliance years. The current proposed approach would favor the 

historically highest-emitting plants, by providing a windfall.

EPA Response:

Per the suggestion, EPA will take general comment on the allocation approach proposed. 

However, EPA believes there is a misunderstanding in the above comment. The 

proposed approach relies on historical emissions as a mechanism for capping allocations 

to sources, not as an apportioning mechanism. Limiting allocations to levels below the 

historical maximum emissions prevents surplus allowances rather than providing for it as 

suggested by the comment. For example two sources with identical heat inputs in a state 

(one coal-fired EGU and one gas-fired EGU) would have the same allocation under 

EPA’s proposed approach (assuming that allocation is less than their historical maximum 

emissions). 

Specific Comments

1. Page 17 – Reviewer recommends clarifying whether EPA is taking comment on options 

to evaluate interstate transport as it relates to western states.

EPA Response:

EPA will clarify in the preamble.

2. Page 24 – Reviewer recommends clarifying the timeframe for the updated analysis.

EPA Response:

The existing preamble language says that the updated analysis will be performed for the 

final rule based on comments on the proposal. EPA will modify the preamble to clarify 

this.

3. Page 30 – Reviewer recommends providing citations for the “authoritative assessments” 

references. 
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

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EPA Response:

EPA will modify the preamble to address this comment.

4. Page 33 – Reviewer recommends replacing the following sentence:

a. “Ozone causes a variety of negative effects on human health, vegetation, and 

ecosystems.” 

b. With the following: “Exposure to ambient ozone causes a variety of negative 

effects on human health, vegetation and ecosystems.”

EPA Response:

EPA will modify the language per commenter suggestion

5. Page 180 – Reviewer recommends clarifying where the information is derived from and 

calculated for the 210,000 tons by the start of 2017 ozone-season compliance period, 

including citations, where appropriate.

EPA Response:

EPA will clarify, see response to comment #6 and #8 above.

Regulatory Impact Analysis

1. Reviewer recommends providing a justification for why $1,300/ton was chosen for the 

primary analysis. EPA states that $1,300/ton is not an artifact of IPM modeling, rather it 

is an exogenous assumption that was imposed on IPM. Reviewer also recommends 

providing explanations why $1,300/ton, $3,400/ton, and $500/ton were chosen and no 

numbers in between. 

EPA Response:

This is explained on pages 120-121 of the preamble. These cost thresholds were chosen 

as they reflect technology break points where new abatement measures were considered 

(exogenously to the model) to become cost effective. These breakpoints reflect an 

engineering assessment of when the technologies become cost effective. EPA did not 

identify any other technologies for NOx mitigation purposes that would be cost-effective

and available by 2017.

2. Reviewer recommends providing a discussion of SCR idling including how likely it is. 

Specifically, it does not appear that idling SCR and SNCR is straight forward depending 

on whether the affected entities built in bypass structures. Are there implementation 

concerns about whether idling is possible without a bypass? If so, how would this affect 

EPA’s analysis?

EPA Response:
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

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Idling of either SCR or SNCR is straightforward. In either case it involves simply 

stopping injection of the reagent, typically by closing a valve and turning off a pump; no 

flue gas bypass capabilities are needed. It is true that a few SCR installations have 

included provisions for bypassing flue gas around the SCR, so that maintenance or 

catalyst replacement can be performed while the boiler continues operating, but this is not 

common. On the other hand, many SCR installations do include provisions for partial 

bypass of flue gas around the boiler economizer, or partial bypass of feedwater around 

the economizer, in order to raise the temperature of flue gas entering the SCR catalyst at 

low loads. These flue gas temperature control bypasses are used during the startup and 

shutdown of the boiler and SCR, not for idling the SCR. EPA will add footnote to RIA 

referencing these points.

3. Reviewer recommends providing additional clarification as to why 2017 was chosen as 

the analytical year, especially since EPA had to “adjust” 2018 IPM modeling results to 

produce 2017 results presented in the analysis. Given the lag in the implementation of 

ozone NAAQS as well as the number of rules in the baseline, especially the Clean Power 

Plan, EPA should look at years further out such as 2030.

EPA Response:

EPA will modify the preamble to address this comment Response: Pages 1-5 and 1-6 of 

the RIA clarify how the choice of a 2017 compliance timeframe was prompted by a 

revision to the attainment date for the 2008 ozone NAAQS and the instruction in North 

Carolina that EPA’s compliance timeframe to address interstate transport be aligned with 

the relevant attainment date. In addition we have added to, and clarified, language on p. 

1-6 which explains the choice to report emissions information for 2017 as well as certain 

impacts in 2020.

4. Table ES-1 – Reviewer recommends clarifying why the less stringent option results in a 

greater reduction in CO2 than the proposed or more stringent option.

EPA Response:

The CO2 emissions reductions are better understood by segmenting into both the covered 

region and non-covered region impacts. Within the covered region, the more stringent 

policy results in greater emission reductions for CO2 as would be anticipated. However, 

the more stringent policy results in slightly fewer emission reductions at the national 

level due to emission increases in the non-covered region.

5. Reviewer recommends discussing at least qualitatively how adding the Phase 2 emission 

budgets would affect the baseline.

EPA Response: 
Summary of Interagency Working Comments on Draft Language under 

EO12866/13563 Interagency Review. Subject to Further Policy Review.

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The CSAPR NOx ozone season Phase 2 emission budgets are in the baseline. See p. 3-5 

of the RIA. EPA will clarify in the RIA text that these budgets are included in the base 

case analysis.

6. Table 5-7 – Reviewer recommends clarifying why there is a larger percentage decrease in 

coal capacity in the less stringent alternative and how does that reconcile with a lower 

MW coal capacity decrease a few rows below in the same table.

EPA Response: 

The correct number for the national coal capacity for the two rows referenced are below. 

EPA will make the correction in the RIA.

 $500 $1,300 $3,400

Coal Capacity % Change: -0.14% -0.14% -0.16%

Coal Capacity Change (MW) -266 -282 -318 

7. Table 5-8, asterisk – Should the analysis be in cents/kWh?

EPA Response:

Table 5-8 currently presents the change in electricity prices in % terms. The changes are 

quite small (e.g., 2018 in-region is -0.01%). EPA did not believe reporting the change in 

cents/kwh is practical. For example, the 2018 in-region average price decrease is -

$0.000096/kwh (a very small change from the in-region base case average price of 9.7 

cents/kwh. Per the commenter suggestion, we will revise the table to present the 2018 

projected retail prices in cents/kWh, and also the % change as shown.

8. Page 6-2 – Reviewer recommends clarifying the sentence “The estimated benefits 

associated with these emissions reductions are beyond those achieved in previous EPA 

rulemakings, including the finalized CPP.”

EPA Response:

Per the commenter suggestion, EPA will revise the sentence to read: “The estimated 

benefits associated with these emissions reductions are additional to those achieved by 

previous EPA rulemakings, including the finalized CPP.”

9. Table 8-2 – Reviewer recommends providing CO2 emissions in metric tons as Table 

ES-1 is in metric tons and should be reported consistently throughout the document.

EPA Response:
Summary of Interagency Working Comments on Draft Language under 

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All CO2 tons in the RIA will be changed to be consistently reported in short tons. This is 

consistent with what EPA did in the CPP RIA and consistent with reporting requirements.