4

- 1

CHAPTER 4 : CONTROL STRATEGIES A ND EMISSIONS REDUCTI ONS

Overview
In order to estimate the costs and benefits of alternative ozone standards, the EPA has analyzed hypothetical control strategies that areas across the country might employ to attain alternative revised primary ozone standards of 70, 65, and 60 ppb. This ch apter documents the
emission control measures EPA applied to simulate attainment with the se alternative ozone standards and the projected emission reductions associated with the measures

. This chapter is organized into four sections. Section 4.1 provides a summary of the steps used to conduct the control strategy analysis. Section 4.2 describes the emission reductions by sector in analyzing the baseline controls to meet the current (75 ppb) ozone standard. Section 4.3
discusses control measures and emissio n reductions applied as part of the alternative standard analyses. Section 4.4 lists the key limitations and uncertainties associated with the control strategy analysis. And finally, Section 4.5 lists the references for the chapter.

For the purposes of th is discussion, it will be helpful to define some terminology. These definitions are specific to this analysis:

 Base Case

- Emissions projected to the year 2025 reflecting current state and federal programs 1 . This does not include control programs specifica lly for the purpose of attaining the current ozone standard (75 ppb).

 Baseline

- For all areas of the U.S. except California, the base case plus additional emissions reductions needed to reach attainment of the current ozone standard (75 ppb) as well as em issions resulting from the Clean Power Plan (U.S. EPA, 2014b). Several areas in California are not required to meet the existing standard by 2025 and may not be required to meet a revised standard until 2038, thus we conducted analyses of attainment in Cal ifornia for post

- 2025. We explain the baseline treatment for California in more detail later in this chapter.

 Alternative Standard Analysis

- Emissions reductions and associated hypothetical controls needed to reach attainment of the alternative standards. These reductions and controls are incremental to the baseline.

 Design Value

- A metric that is compared to the level of the National Ambient Air Quality Standard (NAAQS) to determine compliance

. Design values are typically

1 A complete list of programs included in the 2025 base case emissions is included in the Technical Support Document: Preparation of Emissions Inventories for the Version 6.1, 2011 Emissions Modeling Platform (U.S. EPA, 2014d).4

- 2 used to classify nonattainment areas, assess progress towards meeting the NAAQS, and develop control strategies

. The design value for the 8

- hour ozone standard is calculated as the 3

- year average of the 4th highest 8

- hour daily maximum concentration recorded at each monitoring site

. The EPA analyzed the impact that additional emissions control measures, across numerous sectors, would have on predicted ambient ozone concentrations incremental to the
baseline. These control measures are based on information available at the time of this a nalysis, and include primarily end of pipe controls. Additional emission abatement strategies such as fuel switching, energy efficiency, and process changes may also be employed to reach emission reduction targets. The potential impact of some of these t ypes of strategies is discussed in Chapter 7. Note that we did not conduct this analysis incremental to controls applied as part of previous NAAQS analyses (e.g., NO x or PM 2.5 because the data and modeling on which these previous analyses were based are n ow considered outdated and are not compatible with the current ozone NAAQS analysis. In addition, there were no incremental NOx controls applied in the PM2.5 NAAQS and therefore there would be little to no impact on the controls selected to
meet the altern ative ozone standards analyzed

. 2 Thus, the analysis for the alternative standards focuses specifically on incremental improvements beyond the current standard and other existing and proposed rules. The selection of control strategies is based on a least cost approach selecting from those controls for which we have adequate information on costs, effectiveness, and applicability. The hypothetical control strategies presented in this RIA represent illustrative options for emissions reductions that achieve n ational attainment of the alternative standards. The hypothetical control strategies are not recommendations or requirements for how a revised ozone standard should be implemented, and states will make all final decisions regarding implementation strategie s for a revised ozone NAAQS.

2 There were no additional NOx controls applied in the PM 2.5 NAAQS RIA and therefore there would be little to no impact on the controls selected as part of this analysis. In addition, the only geographic areas that exceed the alternative oz one standard levels analyzed in this RIA and in the 2012 PM 2.5 NAAQS RIA are in California. The attainment dates for a new PM 2.5 NAAQS would likely precede attainment dates for a revised o zone NAAQS. While the 2012 PM 2.5 NAAQS RIA concluded that controls on directly emitted PM 2.5 were t he most cost

- effective on a$/ug basis, states may choose to adopt different control options. These options could include NOx controls. It is difficult to determine the impact on costs and benefits for this RIA, it is highly dependent upon the control measu res that would be chosen and the costs of these measures

.4

- 3

The NO x co ntrol measures dataset for non

- electric generating u nit (EGU) point sources applied in these control strategies reflects a number of revisions that EPA made since the completion of the previous ozone NAAQS RIA. These changes include:

 Removal of incorrect links between control measures and SCCs,

 Updates to cost equations where more recent data was available to improve their

accuracy,

 Inclusion of information that has recently become available concerning known and

emerg ing technologies for reducing NO x emissions, and

 Revising costs and control efficiencies from control measures in the dataset based on recently obtained information from industry and multi

- jurisdictional organizations (e.g., Ozone Transport Commissions and L ake Michigan Air Directors Consortium )

.

These revisions made the NO x control measures dataset for non

- EGUs more accurate,
defen sible, and up to date . These improvements in this dataset will improve our control strategy and cost analyses not only for thi s RIA , but also for other potential rulemakings where control of
NO x from non

- EGUs is an important concern.

4.1 Control Strategy Analysis Steps
The primary year of analysis for analyzing the incremental costs and benefits of meeting a revised ozone standard is 2025. The analysis year was chosen because most areas of the U.S. will be required to meet a revised ozone standard by 2025. In estimating the incremental costs and benefits of potential alternative standards, we recognize that there are several areas that are not required to meet the existing ozone standard by 2025. The Clean Air Act allows areas with more significant air quality problems t o take additional time to reach the existing standard. Several areas in California are not required to meet the existing standard by 2025 and may not be required to meet a revised standard until 2038. Depending on how areas in California are eventually des ignated, some areas may have attainment dates earlier than 2038, but for simplicity we are not distinguishing unique attainment years for different locations within California. To reflect these differences in required attainment dates, we conducted analyse s of attainment in California for the period post

- 2025.4

- 4

While our goal for the California analysis was to reflect 2038, we were not able to project emissions and air quality beyond 2025 for California. However, we were able to adjust baseline air quality to reflect mobile source emissions reductions for California that would occur between 2025 and 2030; these emissions reductions were the result of state and federal mobile source regulations expected to be fully implemented by 2030. For ease of discussion throughout the analyses we refer to the time periods for potential attainment in California and in other areas of the U.S. as post

- 2025 and 2025, respectively. Because we estimate incremental emissions reductions, costs, and benefits for these two distinct time periods, it is not appropriate to add the estimates together or to directly compare the estimates.

T o conduct the control strategy analyses, we require information on (i) control costs, (ii)
control effectiveness in terms of NOx or VOC emissions redu ced, (iii) the sensitivity of ozone design values to the NOx and VOC emissions reductions , and (iv) design value targets for each

area. For the air quality modeling, t he EPA prepared one control s cenario for an alternative standard level of 70 ppb (Step 2 below) because we did not e xpect to have sufficient known
controls for all locations to reach attainment for all of the alternative standards analyzed

. The
control scenario is not really designed to model how areas reach an alternative standard level of 70 ppb , instead it sets up a process for developing , and applying, a list of potentially available
kno wn controls ordered by cost. T o develop the a sufficient amount of controls for the 65 and 60 ppb alternative standard levels, we also work ed t o identify known controls in areas or regions expected to contribute to nonattainment for th e se alternative standards.

The following steps were taken by the EPA to analyze the impacts and costs of the control scenario incremental to the base case air qual ity modeling:

1. Identify geographic areas in the U.S. projected to exceed the alternative standard of 70 ppb in the year 2025 in the base case air quality modeling.
2. Develop a hypothetical control scenario for these areas and generate a control case 2025 emis sions inventory for all areas except California; for California develop a control case post

- 2025 emissions inventory.
3. Perform air quality modeling to assess the air quality impacts of the hypothetical control scenario. Additionally, perform a series of emi ssions sensitivity simulations to develop average ozone response to across

- the

- board NOx and VOC emissions reductions in different areas (see Chapter 3).4

- 5

4. Calculate the portion of the hypothetical control scenario emission reductions that are attributed to meeting the baseline. Estimate any additional emissions reductions beyond the known controls that are needed to meet the current standard based on average ozone response factors. These are the baseline emission reductions.
5. Estimate the additional emissions reductions incremental to the baseline that are needed to meet the alternative standards of 70, 65, and 60 ppb. Costs of controls incremental to (i.e., over and above) the baseline reductions are attributed to the costs of meeting the alternative standard s. These emissions reductions can come from specific known controls or emission reductions needed beyond known controls, also referred to as unknown controls. Potential controls may be categorized as u nknown because the se needed emissions reductions come from sector s for which we have not sufficiently explored emissions abatement opportunities or sectors that might require

non

- traditional abatement through measures like energy efficiency or process changes

.

The following sections will discuss in more de tail the analysis steps presented above.

4. 2 Baseline Control Strategy
Establishing the baseline allows us to estimate the incremental costs and benefits of attaining the alternative standards. Three steps were used to develop the baseline. First, we
estim ated 2025 base case emissions and air quality, reflecting “on the books” regulations (see
Section 3.1.3 Emissions Inventories for a discussion of the rules included in the Base Case for this analysis). 3 Second, we accounted for changes in ozone predicted t o occur due to one potential approach for implementing the Clean Power Plan. Third, we identified additional controls that could be applied to demonstrate attainment of the current ozone standard of 75 ppb.

Additional control measures were used in three s ectors to meet the current ozone standard in establishing the baseline: 4 Non

- Electric Generating Unit Point Sources (Non

- EGUs), Non

Point (Area) Sources, and No nroad Mobile Sources . See Table 4

- 1 for a summary of controls applied in the baseline analysis. There were several areas in California that did not reach

3 Among others factors, t he baseline for this analysis is also affected by the choice of the future year

-- a year farther into the future allows for more time for federal measures to work and to attain

. This baseline is also affected by the air quality starting point, potentially reduc ing the amount of emissions reductions required for attainment

– this analysis started from a standard of 75 ppb, where the analysis in 2008 started from a standard of 84 ppb

. In addition
, we have identified additional “known” controls to apply in this analysis
, controls which are less expensive per ton than unknown controls.
4 In establishing the baseline, the U.S. E PA selected a set of cost

- effective contr ols to simulate att ainment of the current ozone standard. These control sets are hypothetical as states will ultimately determine controls as part of the SIP process.4

- 6

attainment of the current standard with known controls. For these geographic areas, we estimated the additional emissions reductions needed beyond those achieved by identified known controls
for NO x and VOC to attain the current standard.4

- 7

Table 4

- 1. Controls Applied for the Alternative Standard Analyses Control Strategy
Sector NO x VOC

Non

- EGU Point LEC (Low Emission Combustion) Solvent Recovery System

SCR (Selective Catalytic Reduction) Work Practices, and Material Reformulation/Substitution SNCR (Selective Non

- Catalytic Reduction) Low

- VOC materials Coatings and Add

On Controls NSCR (Non

- Selective Catalytic Reduction) Low VOC Adhesives and Improved Application Methods LNB (Low NO x Burner Technology) Permanent Total Enclosure (PTE)

LNB + SCR Solvent Substitution, Non

- Atomized Resin Application Methods

LNB + SNCR Petroleum Wastewater Treatment Controls

OXY

- Firing Incineration (Thermal, Catalytic, etc) to Reduce VOC Emissions Biosolid Injection Technology

LNB + Flue Gas Recirculation
LNB + Over Fire Air Ignition Retard
Natural Gas Reburn

Ultra LNB

NonPoint NSCR (Non

- Selective Catalytic Reduction) Process Modification to Reduce Fugitive VOC Emissions LEC (Low Emission Combustion) Reformulation to Reduce VOC Content LNB (Low NO x Burner Technology) Incineration (Thermal, Catalytic, etc) to Reduce VOC Emissions

LNB Water Heaters Low Pressure/Vacuum (LPV) Relief Valves in Gasoline Storage Tanks

Reduced Solvent Utilization Gas Recovery in Landfills

Nonroad Diesel Retrofits & Engine Rebuilds

A map of the country is presented in Figure 41, which shows the counties projected to exceed the current ozone standard of 75 ppb in the 2025 base case scenario. This includes 8 projected exceeding counties in California and 3 exceeding counties in Texas. NOx control4

- 8

measures were applied in these 11 counties in the baseline analysis to meet the current ozone standard. In addition, NOx control measures were applied to 40 California counties and 52 Texas counties adjacent to exceeding counties in order to ad dress transport coming from these adjacent counties. A map of the areas where control measures were applied to demonstrate attainment of the current standard and establish the baseline is presented in Figure 4

- 2.

To construct the post

- 2025 baseline, we inc luded mobile source NO x and VOC emissions changes that are projected to occur in California from 2025

- 2030 as a result of California’s current mobile source control programs and projected changes in vehicle miles traveled and nonroad activity levels. The se changes were included because they would result in emission
reductions that would contribute toward attainment of the current ozone standard. No emission projections were available for other sectors for this time period, and no mobile source emissions

p rojections were available beyond 2030. Additionally, VOC controls were applied in California counties highlighted in Figure 4

- 2. Even with the above mentioned controls, some areas in California did not reach attainment with known controls. For these areas, we estimated the
additional NO x emission reductions needed beyond identified known controls to attain the
standard.4

- 9

Figure 4

- 1

. Counties Projected to Exceed the Baseline Level of the Current Ozone

Standard (75 pp b ) in 2025 Base Case4

- 10

Figure 4

- 2. Cou nties Where Emissions Reductions Were Applied to Demonstrate

Attainment of the Current Standard for the Baseline Analysis

Tables 4

- 2 and 4

- 3 summarize the NO x and VOC emission reductions needed to demonstrate attainment of the current ozone standard (75 ppb).4

- 11

Table 4

- 2. Summary of Emission Reductions by Sector for Known Controls Applied to

Demonstrate Attainment of the Current Standard for the 2025 Baseline

- U.S., except California (1,000 tons/year) a Geographic Area b Emissions Sector NO x VOC

East EGU

- - Non

- EGU Point 18

- Nonpoint 26

- Nonroad 0.83

- Onroad

- - Total 45

- West EGU

- - Non

- EGU Point

- - Nonpoint

- - Nonroad

- - Onroad

- - Total

- -

a Estimates are rounded to two significant figures.

b For the control strategy and cost analysis, “East” includes the Northeast, Midwest, and Central regions, and “West” includes the Southwest region. See Chapter 3 for a description of these regions.

Table 4

- 3

. Summary of Emission Reductions (Known and Unkn own Controls) Applied to

Demonstrate Attainment in California for the post

- 2025 Baseline (1,000 tons/year) a Emissions Sector NO x VOC

Known Controls EGU

- - Non

- EGU Point 14 0.61 Nonpoint 14 47 Nonroad 4.2

- Onroad

- - Total 31 48

Unknown Controls All 160

- Total 190 48

a E mission reduction e stimates are rounded to two significant figures

. The 2025 baseline for this analysis presents one scenario of future year air quality based upon specific control measures, additional emission reductions beyond known controls, promulgated federal rules such as Tier 3
, and specific years of initial values for air quality monitoring and emissions data

. This analysis presents one illustrative strategy relying on the
identified f

ederal measures and other strategies that states may employ

. States may ultimately4

- 12

employ other strategies and/or other federal rules may be adopted that would also help in achieving attainment with the current standard

.

4. 3 Alternative Standard Analyses
After identifying the controls in the baseline scenario, additional controls needed to meet the alternative standards were identified in four sectors: Electric Generating Units (EGUs), Non

Electric Generating Unit Point Sources (Non

- EGUs), Non

- Point (Area) Sources, and Nonroad
Mobile Sources. Onroad mobile source controls were not applied because they are largely addressed in existing rules such as the recent Tier 3 rule. Controls applied for the alternative standard analyses were the same as were applied f or the baseline analysis (see Table 4

- 1 for a summary of controls applied in the baseline) with the addition of Selective Catalytic Reduction applied to EGUs. Other than the addition of EGU controls, the primary difference between the controls applied for the alternative standards versus the baseline was the geographic areas to which they were applied.

The EPA p erformed a national scale air quality modeling analysis to estimate ozone
concentrations for the future base case year of 2025. To accomplish this, we modeled multiple emissions cases for 2025, including the 2025 base case and twelve 2025 emissions sensitivity
simulations. The twelve emissions sensitivity simulations were used to develop ozone sensitivity factors (ppb/ton) from the modeled response of ozone to changes in NOx and VOC emissions from various sources and locations. These ozone sensitivity factors were then used to determine the amount of emissions reductions needed to reach the 2025 baseline and evaluate potential
alternative standard le vels of 70, 65, and 6 0 ppb incremental to the baseline . As mentioned previously, only a subset of known controls were included in the modeled control scenarios. Therefore, any additional emissions reductions may include both known and unknown controls.
In areas of the country outside of California, Texas, and the northeast, total emissions reductions needed beyond the baseline were based entirely on response factors, i.e., not based on the hypothetical control scenario used in the air quality modeling.

Fi gure 4

- 3 shows the counties projected to exceed the alternative standards analyzed for the 2025 baseline for areas other than California. For the 70 ppb scenario, emissions reductions were required for monitors in the Central and Northeast regions (see Cha pter 3, Figure 3

- 3 for a4

- 13

depiction of the regions). For the 65 and 60 ppb scenarios, emissions reductions were applied in all regions with projected baseline DVs above these levels. For the 60 ppb scenario, additional VOC tons were identified in Chicago be cause some sites in that area experienced NO x disbenefits meaning that the regional NO x reductions resulted in ozone DV increases from below 60 ppb to above 60 ppb. Therefore it was not possible to identify a scenario in which regional
NO x reductions and maximum known VOC controls alone resulted in all Midwest monitors meeting a 60 ppb standard. An iterative approach was used determine a combination of NO x and
VOC emissions reductions that would not lead to over

- control at either the NO x - limited monitor

w ith the highest design value or the VOC

- limited monitor with the highest design value.
B ecause of the regional approach we used for locations other than T exas , we were not able to geographically fine tune the control strategies, and thus there is some uncertainty in the actual

amoun ts of emissions reductions estimated for a ttain ing the alternative standards.

Figure 4

- 3. Projected Ozone Design Values in the 2025 Baseline Scenario4

- 14

Figure 4

- 4 shows the counties projected to exceed the alternative standar ds analyzed for the post

- 2025 baseline analysis for California. For the California post

- 2025 alternative standard analyses, all known controls were applied in the baseline so incremental reductions are from
unknown controls.

Figure 4

- 4. Projected Ozone Design Values in the post

- 2025 Baseline Scenario

4.3.1 Identifying Known Controls Needed to Meet the Alternative Standards

For the 2025 alternative control strategy analys e s of 70, 65 and 60 ppb , known NO x controls for four sectors were used: EGUs, non

- EGU point , nonpoint, and nonroad mobile

source s . In a smaller number of geographic areas, VOC controls were applied to non

- EGU point and nonpoint sources.4

- 15

For Texas, reductions were first applied to NO x sources in the areas surrounding Dallas
and Houston. Ad ditional reductions then were applied to VOC sources in the area surrounding Houston, to NO x sources in other parts of Texas, and to sources in the surrounding states. For the Northeast, Midwest, and Southwest areas of the country, reductions were applied to NO x sources within the regions. For regions where additional reductions were needed, controls were applied
to VOC sources in urban areas with the highest ozone design value s in the region

. 5

For California, all known controls were applied in the baseli ne analysis so there were no known controls available to apply toward the incremental emissions reductions needed for the alternative analysis levels for post

- 2025. Maps of the areas where control measures were applied
to demonstrate attainment of the alte rnative analysis levels are presented in Figures 4

- 5 and 4

- 6.
Note that w e do not account for between region transport of ozone, and therefore, especially for
the 65 and 60 ppb alternative standard levels, we may be overstating the amount of emissions
reductions needed for attainment

.

5 Texas, California, and the northeast were included in the hypothetical control scenario for an alternative standard of 70 ppb. Other regions were modeled as part of the 2025 emissions sensitivity simulations.4

- 16

Figure 4

- 5. Counties Where Emissions Reductions Were Applied to Demonstrate

Attainment with a 70 ppb Ozone Standard in the 2025 Analysis4

- 17

Figur e 4

- 6. Counties Where Emissions Reductions Were Applied to Demonstrate

Attainment with 65 and 60 ppb Ozone Standards in the 2025 Analyses

Table 4

- 4 shows the number of exceeding counties and the number of adjacent counties to which controls were applied fo r the alternative standards

. For a complete list of geographic areas for the alternative standards see Appendix 4.A

.4

- 18

Table 4

- 4

. Number of Counties with Exceedances and Number of Additional Counties

Where Reductions Were Applied for the 2025 Alternative St andards Analyses

- U.S., except California

Alternative Standard Number of Counties with Exceedances Number of Additional Counties Where Reductions Were Applied
70 ppb 15 479

65 ppb 115 1,925

60 ppb 289 1,791 a

a Number of additional counties where reductions are applied declined for 60 ppb analysis because the number of overall counties in the analysis remained the same while the number of exceeding counties increased.

Table s 4

- 5 through 4

- 7 show the emission s reductions from known controls for th e alternative standards analyzed. No exceedances were projected for the West region, outside of California, for the 70 ppb alternative standard. For the lower alternative standards of 65 and 60 ppb, similar controls were applied as were used in the 70 ppb an alysis, but the geographic area in which they were applied increased. The largest emission reductions were in the non

- EGU point source and nonpoint sectors. For details regarding emission reductions by control measure see Appendix 4.A

Table 4

- 5. Summary o f Emission Reductions by Sector for Known Controls Applied to

Demonstrate Nationwide Attainment with a 70 ppb Ozone Standard in 2025, except California (1,000 tons/year) a Geographic Area Emissions

Sector Baseline Emissions Emission Reductions

NO x VOC NO x VOC East EGU 884 25

-

Non

- EGU Point 1,485 210 0.98 Nonpoint 1,487 260 54 Nonroad 1,235 5

- Onroad 1,135

- - Total 6,226 490 55 West EGU 159

- -

Non

- EGU Point 226

- - Nonpoint 193

- - Nonroad 219

- - Onroad 197

- - Total 1,025

- -

a E mission reduction e stimates are rounded to two significant figures.4

- 19

Table 4

- 6

. Summary of Emission Reductions by Sector for Known Controls Applied to

Demonstrate Nationwide Attainment with a 65 ppb Ozone Standard in 2025

- except California (1,000 tons/year) a Geographic Area Emissions Sector NO x VOC East EGU 170

- Non

- EGU Point 410 3.6 Nonpoint 420 95 Nonroad 12

- Total 1,000 99 West EGU 36

- Non

- EGU Point 38 0.47 Nonpoint 37 6.6 Nonroad 1.3

- Total 110 7

a E mission reduction e stimates are rounded to two significant figures

. Table 4

- 7

. Summary of Emission Reductions by Sector for Known Controls Applied to

Demonstrate Nationwide Attainment with a 60 ppb Ozone Standard in 2025

- except California (1,000 tons/yea r) a Geographic Area Emissions Sector NO x VOC East EGU 170

- Non

- EGU Point 410 4.2 Nonpoint 420 99 Nonroad 12

- Total 1,000 100 West EGU 62

- Non

- EGU Point 48 0.47 Nonpoint 39 6.6 Nonroad 1.3

- Total 150 7

a E mission reduction e stimates are rounded to two significant figures

.

4.3.2 Known Control Measures Analyzed
Known control measures were applied to electric generating units (EGU), n on

- EGU point, nonpoint (area), and n onroad mobile sources for demonstration of attainment with the

cur rent and alternative standards

. The applied control measures were identified using the EPA’s Control Strategy Tool (CoST) (U.S. EPA, 2014c), Integrated Planning Model (IPM), and
NONROAD Model

. CoST model s emission s reductions and engineering costs associa ted with control strategies applied to point, area, and mobile sources of air pollutant emissions by matching control measures to emission s sources using algorithms such as "maximum emissions4

- 20

reduction", "least cost", and "apply measures in series". For t his analysis, we applied the maximum emissions reduction algorithm. These controls are described further in Appendix 4.A

. Specific controls were applied in the air quality modeling only for a portion of the analysis (for California, Texas, and the northea st, areas projected to exceed an alternative standard level of 70 ppb). A majority of the emission reductions needed were identified using the ozone sensitivity factors developed from the twelve emissions sensitivity simulations (see Chapter 3, Section 3.1 for a discussion of the development of the ozone sensitivity factors).

Nonpoint and n onroad mobile source emissions data are generated at the county level, and therefore controls for these emissions sectors were applied at the county level . EGU and

n on

- EGU point source controls are applied to individual point sources . Control measures were applied to point and n onpoint sources of NO x , including: industrial boilers, commercial and institutional boilers, reciprocating internal combustion engines in the oil and gas industry and other industries, glass manufacturing furnaces, and cement kilns. The analysis for non road
mobile sources applied NO x controls to diesel engines.

In a portion of the geographic areas where NO x controls were applied, the EPA also

ap plied control measures to sources of VOC including surface coating, solvents, and fuel storage
tanks. VOC reductions were analyzed in the urban areas with the highest ozone design value s in each region: n orthern and s outhern California; Denver in the S outh west; Houston and Dallas in
the C entral r egion; Chicago, Detroit, and Louisville in the Midwest ; New York, Baltimore, and Pittsburgh in the N ortheast . Even among these areas, in some cases NO x reductions necessary to bring the very highest urban areas into attainment made the VOC reductions unnecessary in other high ozone urban areas within the region

.
To more accurately depict available controls, the EPA employed a decision rule in which controls were not applied to any non

- EGU or nonpoint sources with le ss than 25 tons/year of
emissions per pollutant. This decision rule is more inclusive of sources than the rule we employed in the previous O 3 and PM 2.5 NAAQS RIA s where we applied a minimum of 50 tons/year for each pollutant. We modified the decision rule for this NAAQS analysis to recognize the potential for emissions reductions in the large number of sources emitting in the
25

- 50 tons/year range in order to devise control strategies for full, or closer to full, attainment.4

- 21

Historically, t he reason for not applying controls to sources emitting less than 25 tons/year has
been that m any point sources with emissions below this level already have controls in place. For the analysis, we applied best engineering judgement to apply controls to select sources.

4.3 .3 Emissions Reductions beyond Known Controls Needed to Meet the Alternative Standards
There were several areas where known controls did not achieve enough emission s reductions to attain the alternative standards of 70, 65, and 60 ppb. To complete the analysis, the
EPA then estimated the additional emission s reductions beyond known controls needed to reach
attainment , also referred to as unknown controls. For information on the methodology used to develop the emission reductions estimates, see Chapter 3

. Table 4

- 8 show s the emission s reductions needed from unknown controls in 2025 for the U.S., except California, for the alternative standards analyzed . Table 4

- 9 shows the reductions needed from unknown controls for California for the post

- 2025 analysis.

Table 4

- 8. Summary of Emissions Reductions by Alternative Standard for Unknown

Controls for 2025

- except California (1,000 tons/year) a Alternative Standard Region NO x VOC 70 ppb b East West 150

- -

- 65 ppb c East West 750

- -

- 60 ppb d East West 1,900 350 41

-

a Estimates are rounded to two significant figures.

b Unknown controls for the 70 ppb alternative standard are needed in the Northeast and Central regions (see Chapter 3 for a description of these regions)

.

c Unknown controls for the 65 ppb alternative standard are needed in the Northeast, Central, and Midwest regions (see Chapter 3 for a description of these regions)

.

d Unknown controls for the 60 ppb alternative standard are needed in the Northeast, Central , Midwest, and Southwest regions (see Chapter 3 for a description of these regions)

.

Table 4

- 9. Summary of Emissions Reductions by Alternative Level for Unknown Controls

for post

- 2025

- California (1,000 tons/year) a Alternative Standard Region NO x VOC 70 ppb CA 53

- 65 ppb CA 110

-4

- 22 60 ppb CA 140

-

a Estimates are rounded to two significant figures.

4.3.4 Summary of Emissions R eductions Needed to Meet the Alternative Standards

Table 4

- 10 summarizes the known and unknown emissions reductions needed to meet the alternative standard levels in 2025 for the East and West, except California. In the East for 2025, the unknown NOx reductions needed as percentage of the total rises from 23 percent to 66 percent as the alternative standard level decreases from 70 ppb to 60 ppb. Meanwhile, no unknown VOC reductions are needed in the East for the 70 ppb and 65 ppb levels. In the West (except California) for 2025, unknown NOx reductions are not needed until the 60 ppb level,
when the unknown tons constitute abou t 70 percent of the total reductions needed. No unknown VOC reductions are needed in the West (except California) for 2025 for any of the alternative
standard levels.

Table 4

- 10. Summary of Known and Unknown Emissions Reductions by Alternative

Standard Levels in 2025, Except California (1,000 tons/year) a
Alternative Standard Geographic Area Emissions Reductions 70 ppb 65 ppb 60 ppb
East NOx Known 490 1,000 1,000

NOx Unknown 150 750 1,900 % NOx Unknown 23% 43% 66% VOC Known 55 99 100 VOC Unknown 0 0 41 % VOC Unknown 0% 0% 29% West NOx Known 0 110 150 NOx Unknown 0 0 350 % NOx Unknown N/A 0% 70% VOC Known 0 7 7 VOC Unknown 0 0 0 % VOC Unknown N/A 0% 0%

a Estimates are rounded to two significant figures.

Table 4

- 11 shows again that there were no known NOx emissions reductions identified for meeting the alternative standard levels for post

- 2025 California and that 100 percent of the NOx tons needed were unknown. Meanwhile, no unknown VOC reductions are needed for the

any o f the alternative standard levels for post

- 025 California.4

- 23

Table 4

- 11. Summary of Known and Unknown Emissions Reductions by Alternative

Standard Levels for post

- 2025

- California (1,000 tons/year) a
Alternative Standard Geographic Area Emissions Reductions 70 ppb 65 ppb 60 ppb California NOx Known 0 0 0

NOx Unknown 53 110 140 % NOx Unknown 100% 100% 100% VOC Known 0 0 0 VOC Unknown 0 0 0 % VOC Unknown N/A N/A N/A

a Estimates are rounded to two significant figures.

4.4 Limitations and Uncertainties EPA’s analysis is based on its best judgment for various input assumptions that are
uncertain

. As a general matter, the Agency selects the best available information from engineering studies of air pollution controls and has set up what it b elieves is the most reasonable modeling framework for analyzing the cost, emissions changes, and other impacts of regulatory
controls

. However, the estimates of emissions reductions associated with our control strategies above are subject to important limi tations and uncertainties . In the following, we discuss the limitations and uncertainties that are most significant.

 Illustrative control strategy: A control strategy is the set of actions that States may take to meet a standard, such as which industries s hould be required to install
end

- of

- pipe controls or certain types of equipment and technology. The illustrative control strategy analysis in this RIA presents only one potential pathway to attainment. The control strategies are not recommendations for how a revised ozone standard should be implemented, and States will make all final decisions regarding implementation strategies for the revised NAAQS. We do not presume that the control strategies presented in this RIA are an exhaustive list of possibilities for
emissions reductions.

 Emissions Inventories and Air Quality Modeling: These serve as a foundation for the projected ozone values, control strategies and costs in this analysis and thus limitations and uncertainties for these inputs impact the results, especially for4

- 24 issues such as future year emissions projections and information on controls currently in place at sources. Limitations and uncertainties for these inputs are discussed in previous chapters devoted to these subject areas. In addition, there are factors that affect emissions, such as economic growth and the makeup of the economy (e.g., growth in the oil and natural gas sector), that introduce additional uncertainty.

 Projecting level and geographic scope of exceedances: Estimates of the geographic areas that would exceed revised alternative levels of the standard in a future year, and the level to which those areas would exceed, are approximations
based on a number of factors. The actual nonattainment determinations tha t would result from a revised standard will likely depend on the consideration of local issues, changes in source operations between the time of this analysis and implementation of a new standard, and changes in control technology over time.

 Assumptions ab out the baseline: There is significant uncertainty about the illustration of the impact of rules, especially the Clean Power Plan because it is a proposal and because it contains significant flexibility for states to determine how
to choose measures to com ply with the standard.

 Applicability of control measures: The applicability of a control measure to a specific source varies depending on a number of process equipment factors such as age, design, capacity, fuel, and operating parameters. These can vary considerably from source to source and over time. This analysis makes assumptions across broad categories of sources nationwide.

 Control measure advances over time: The control measures applied do not reflect potential effects of technological change that may be available in future years and the effects of “learning by doing” or “learning by researching” are not accounted for in the emissions reduction estimates. Thus, all estimates of impacts associated with control measures applied reflect our current kno wledge, and not projections, of the measures’ effectiveness. In our analysis, we do not have the necessary data for cumulative output, fuel sales, or emissions reductions for all sectors included in order to properly generate control costs that reflect lea rning

- curve impacts or the4

- 25 impacts of technological change. We believe the effect of including these impacts would be to lower our estimates of costs for our projected year control strategies.

 Pollutants to be targeted: Local knowledge of atmospheric chem istry in each geographic area may result in a different prioritization of pollutants (VOC and
NO x ) for control . For the baseline in this analysis, we included only promulgated or proposed rules, but that there may be additional regulations promulgated in the future that reduce NOx or VOC emissions. These regulations could reduce the
current baseline levels of emissions.

4. 5 References
U.S. Environmental Protection Agency (U.S. EPA). 2014a. Control of Air Pollution from Motor Vehicles: Tier 3 Motor Vehicle Emission and Fuel Standards. Office of Transportation and Air Quality. Available at http://www.epa.gov/otaq/tier3.htm

. U.S. Environme ntal Protection Agency (U.S. EPA). 2014b. Proposed Carbon Pollution Guidelines for Existing Power Plants and Emission Standards for Modified and Reconstructed Power Plants. Available at http://www2.epa.gov/sites/production/files/2014

- 06/documents/20140602r ia

- clean

- power

- plan.pdf U.S. Environmental Protection Agency (U.S. EPA). 2014c. Control Strategy Tool (CoST) Documentation Report. Office of Air Quality Planning and Standards, Research Triangle Park, NC. Available at http://www.epa.gov/ttnecas1/cost.htm

. U.S. Enviro nmental Protection Agency (2014d ) Preparation of Emissions Inventories for the Version 6.1, 2011 Emissions Modeling Platform (ht tp://www.epa.gov/ttn/chief/emc