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Draft Technical Support Document

Illinois

Area Designations For the 

2010 SO2 Primary National Ambient Air Quality Standard

Summary

Pursuant to section 107(d) of the Clean Air Act, EPA must initially designate areas as either 

“unclassifiable”, “attainment”, or “nonattainment” for the 2010 one-hour sulfur dioxide (SO2) 

primary national ambient air quality standard (NAAQS). The Clean Air Act defines a 

nonattainment area as one that does not meet the NAAQS or that contributes to a violation in a 

nearby area. 

Illinois submitted recommendations on June 2, 2011. Table 1 below lists Illinois’s 

recommendations and identifies the counties or portions of counties in Illinois that EPA intends 

to designate “nonattainment” based on monitored violations. 

Table 1. Nonattainment Area Designations for Illinois

Area Illinois Recommended 

Designation of Areas/

Counties

EPA's Intended 

Designation of Areas/

Counties

Pekin, IL

 Tazewell County (partial)

 - Cincinnati Township, 

 - Pekin Township

 Peoria County (partial)

 - Hollis Township

Nonattainment

Unclassifiable

Nonattainment

Nonattainment

Lemont, IL

 Cook County (partial)

 - Lemont Township

 Will County (partial)

 - Dupage Township

 - Lockport Township

Nonattainment

Nonattainment

Nonattainment

Nonattainment
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Background

On June 3, 2010, EPA revised the primary SO2 NAAQS (75 FR 35520, published on June 22, 

2010). EPA revised the primary SO2 standard by establishing a new one-hour standard at a level 

of 75 parts per billion (ppb) which is attained when the three-year average of the 99th percentile 

of one-hour daily maximum concentrations does not exceed 75 ppb. EPA has determined that 

this is the level necessary to provide protection of public health with an adequate margin of 

safety, especially for children, the elderly and those with asthma. These groups are particularly 

susceptible to the health effects associated with breathing SO2. EPA is revoking the two prior

primary standards of 140 ppb evaluated over 24 hours, and 30 ppb evaluated over an entire year 

because they will not add additional public health protection given a one-hour standard at 75 

ppb. Accordingly, EPA is not designating areas in this process on the basis of either of these two 

primary standards. Similarly, the secondary standard for SO2 has not been revised, so EPA is 

not designating areas in this process on the basis of the secondary standard. 

EPA’s SO2 Designation Approach

Section 107(d) of the Clean Air Act requires that not later than one year after promulgation of a 

new or revised NAAQS, state Governors must submit their recommendations for designations 

and boundaries to EPA by June 2011. Section 107(d) also requires EPA to provide notification 

to states no less than 120-days prior to promulgating an initial area designation that is a 

modification of a state’s recommendation. EPA was to promulgate initial area designations 

within two years of promulgation of the revised primary standard, although EPA has extended 

this deadline for one additional year due to having insufficient information to promulgate the 

designations. If a state did not submit designation recommendations, EPA will promulgate the 

designations that it deems appropriate. If a state or tribe disagrees with EPA’s intended 

designations, they have an opportunity to demonstrate why any proposed modification is 

inappropriate.

Designations guidance was issued by EPA through a March 24, 2011, memorandum from 

Stephen D. Page, Director, U.S. EPA, Office of Air Quality Planning and Standards, to Air 

Division Directors, U.S. EPA Regions I-X. This memorandum identifies factors EPA intends to 

evaluate in determining boundaries for areas designated nonattainment. These five factors

include: 1) air quality data; 2) emissions and emissions-related data (location of sources and 

potential contribution to ambient SO2 concentrations); 3) meteorology (weather/transport patterns); 

4) geography/topography (mountain ranges or other air basin boundaries); and 5) jurisdictional 

boundaries (e.g., counties, air districts, pre-existing nonattainment areas, reservations, metropolitan 

planning organization), among any other criteria deemed to be relevant to establishing appropriate 

area designations and boundaries for the one-hour SO2 NAAQS.

The March 24, 2011, memo recommended that area boundaries default to the county boundary unless

information provided by the state or tribe justifies a larger or smaller boundary than that of the 

county. EPA believes it is appropriate to evaluate each potential area on a case-by-case basis, and to 

recognize that area-specific analyses conducted by states, tribes and/or EPA may support a differing 

boundary than a county boundary.
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In this technical support document, EPA discusses its review and technical analysis of the 

recommendations regarding areas with monitored violations submitted by Illinois for designations for

the one-hour SO2 standard and any modifications from these recommendations.

Definition of important terms used in this document:

1) Designated nonattainment area – an area which EPA has determined, based on a state 

recommendation and/or on the technical analysis included in this document, has violated the 

2010 SO2 NAAQS, based on the most recent three years of air quality monitoring data, or 

contributes to a violation in a nearby area. 

2) Recommended nonattainment area – an area a state or tribe has recommended that EPA 

designate as nonattainment.

3) Violating monitor – an ambient air monitor meeting all methods, quality assurance and siting 

criteria and requirements whose valid design value exceeds 75 ppb, as described in Appendix T 

of 40 CFR part 50.

4) 2010 SO2 NAAQS – The NAAQS for SO2 promulgated in 2010. This NAAQS is 75 ppb, 

based on the three year average of the 99th percentile of the annual distribution of daily 

maximum one-hour average concentrations. See 40 CFR Part 50.17.

5) Design Value - a statistic computed according to the data handling procedures of the NAAQS 

(in 40 CFR 50 Appendix T) that, by comparison to the level of the NAAQS, indicates whether 

the area is violating the NAAQS.

Technical analysis for the Lemont, IL Area

Introduction 

This technical analysis for the Lemont, IL area identifies Cook County with a monitor, in 

Lemont, that violates the 2010 SO2 NAAQS, and evaluates nearby counties for contributions to 

SO2 concentrations in the area. EPA has evaluated this county and nearby counties based on the 

evidence for the factors recommended in the March 24, 2011 EPA guidance. 

Figure 1 is a map of the area showing the locations and design values of air quality monitors in 

the area, and the counties surrounding any violating air quality monitors. Notably, a monitor in 

Lemont Township in Cook County recorded a 2009 to 2011 design value of 98 ppb. Multiple 

other monitors in Cook County and a monitor in Will County showed design values below the 

standard, with values ranging from 18 to 30 ppb. 
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Figure 1. Map of sources and monitors in the Chicago area and the intended Lemont, IL

nonattainment area

Illinois analyzed the sources that might be contributing to the monitored violation in Lemont. 

Based on this assessment, Illinois recommends that an area consisting of DuPage and Lockport 

Townships in Will County and Lemont Township in Cook County be designated as 

nonattainment. This recommendation reflects Illinois’ view that no significant sources are 

located in Cook County near Lemont but that three significant sources are located nearby in Will 

County.

Based on EPA's technical analysis described below, EPA is intending to designate a Lemont 

nonattainment area consisting of Lemont Township in Cook County and DuPage and Lockport 

Townships in Will County as nonattainment for the 2010 SO2 NAAQS.

Detailed Assessment

Air Quality Data 

This factor considers the SO2 air quality monitoring data, including the design values (in ppb) 

calculated for all air quality monitors in the Chicago metropolitan area based on data for the 

2009-2011 period.

The 2010 SO2 NAAQS design values for the Chicago area within Illinois are shown in Table 2.
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Table 2. Air Quality Data in the Chicago Area

County State Recommended

Nonattainment?

Monitor Air Quality 

System ID

Monitor Location SO2 Design Value, 

2009-2011 (ppb)

Cook No 17-031-0050 41.7076, 87.5686 20

No 17-031-0063 41.877, 87.6343 18

No 17-031-0076 41.7514, 87.7135 24

Yes 17-031-1601 41.6681, 87.9906 98

No 17-031-4002 41.8552, 87.7525 30

No 17-031-4201 42.1400, 87.7992 18*

Will No 17-197-0013 41.46, 88.182 28

*Data are incomplete. Value is determined from available data for instrument identified as POC 2.

Monitors in Bold have the highest 2009-2011 design value in the respective county.

The Lemont monitor in Cook County shows a violation of the 2010 SO2 NAAQS. 

Emissions and Emissions-Related Data

Evidence of SO2 emissions sources in the vicinity of a violating monitor is an important factor 

for determining whether a nearby area is contributing to a monitored violation. For this factor, 

EPA evaluated county level emission data for SO2 and any growth in SO2 emitting activities

since the date represented by those emissions data.

Emissions

The most recent year for which national emissions information was compiled was 2008. Illinois 

did not provide more recent emissions information. Therefore, EPA relied on the 2008 National 

Emissions Inventory (NEI) emissions data (NEI08V2). 

Table 3 shows total emissions of SO2 (given in tons per year) for Cook County and for adjoining 

Will County. Table 3 also shows pertinent information for sources in these counties emitting

greater than 100 tons per year of SO2 according to the 2008 NEI. 
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Table 3. SO2 Emissions in the Chicago Area (NEI08V2)

County Facility in 

State 

Recommen

ded N.A. 

Area?

Facility Emissions 

NEI08V15 

(tons per 

year)

Facility Location Distance 

to 

Lemont 

Monitor 

(km)

Total County 

SO2 Emissions 

(tons per year)

Cook No Crawford Station 6,627 tpy 41.8278, 87.7236 28 20,562

No Fisk Station 4,486 tpy 41.8408, 87.6533 34

No Corn Products 2,203 tpy 41.7751, 87.8224 18

No Koppers 823 tpy 41.8206, 87.7487 26

No O’Hare Airport 511 tpy 41.9772, 87.9044 35

No Saint-Gobain 

Containers 

345 tpy 41.6439, 87.6003 32

No Carmeuse Lime 321 tpy 41.7056, 87.5438 37

No Midway Airport 114 tpy 41.785, 87.7519 24

Will No MWG Joliet Station 18,281 tpy 41.4947, 88.125 22 64,126

Yes MWG Will County 

Station 

16,497 tpy 41.6344, 88.0592 7

No Exxon Mobil 16,404 tpy 41.4138, 88.1835 33

Yes Oxbow Midwest 

Calcining 

6,205 tpy 41.6622, 88.0379 4

Yes CITGO Petroleum 6,137 tpy 41.6444, 88.0559 6

The sources in Cook County are at considerable distances from the violating monitor. For 

example, the closest source is Corn Products Corporation, at about 18 kilometers from the 

monitor, with emissions of about 2,300 tons per year, and the highest emitting source in Cook 

County, Midwest Generation’s Crawford Station, is about 28 kilometers away, emitting about 

6,600 tons per year. These sources are at sufficient distance from the monitor, with sufficiently 

low emissions, for EPA to judge, as recommended by Illinois, that these sources do not 

contribute significantly to the monitored violation at the Lemont monitor. 

Three of the sources in Will County are relatively close to the Lemont monitor and have 

sufficient emissions that Illinois recommended including the townships containing these sources 

in the Lemont nonattainment area. Midwest Generation’s Joliet Station and the Exxon-Mobil 

refinery are sufficient distance and do not have sufficiently high emissions to warrant being 

included in this nonattainment area based on the monitored violation.

Emissions Controls

The emissions data used by EPA in this technical analysis and provided in Table 3 represent 

emissions levels taking into account any control strategies implemented on stationary sources in 

this area up to and including 2008. EPA has not received any additional information on 

emissions reductions resulting from controls put into place after 2008.
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Meteorology (weather/transport patterns)

When considering a one-hour standard, violations can occur at anytime, even when weather 

patterns are varied from the normal trends of the area. For this area, winds can be from any 

direction. Therefore, for a one-hour standard, it is useful to consider all directions to have 

potential contribution. Nevertheless, according to wind information provided with Illinois’ 

recommendations, winds in this area come from the west and southwest more frequently than 

from other quadrants, particularly when concentrations are high at the Lemont monitor, so 

sources to the west and southwest of the Lemont monitor are most likely to contribute to 

violations at this monitor.

Geography/topography (mountain ranges or other air basin boundaries)

The Chicago area does not have any geographical or topographical barriers significantly limiting 

air pollution transport within its airshed. Therefore, this factor did not play a significant role in 

determining the nonattainment boundary.

Jurisdictional boundaries 

Illinois does not have any current SO2 nonattainment areas. Townships in Illinois have well 

established boundaries and are a suitable basis for defining nonattainment areas.

Other Relevant Information

EPA did not receive additional information relevant to establishing a nonattainment area 

boundary for this area.

Conclusion

Illinois has adequately justified a nonattainment area, based on the violating monitor in Cook 

County, that includes the township that contains the monitoring site and two townships in Will 

County, DuPage and Lockport Townships, that are judged to contribute to the monitored 

violation. In judging the area to be included in the Lemont nonattainment area based on the 

violation recorded at the Lemont monitor, EPA judged that sources in Cook County outside 

Lemont Township, as well as the Midwest Generation Joliet plant and the Exxon-Mobil refinery 

in Will County, are sufficiently distant from the violating monitor to warrant being excluded 

from this nonattainment area. 
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Technical analysis for the Pekin, IL Area

Introduction 

This technical analysis for the Pekin, IL area identifies a Tazewell County monitor that violates

the 2010 SO2 NAAQS. EPA has evaluated this county and nearby counties based on the 

evidence for the factors recommended in the March 24, 2011 EPA guidance.

Figure 2 is a map of the area showing the location and the design value of the air quality monitor

in the area, and the counties surrounding this air quality monitor. The monitor in Pekin

(Tazewell County) recorded a 2009 to 2011 design value of 211 ppb. A monitor in Peoria 

County recorded a 2009 to 2011 design value of 36 ppb, based on incomplete data. No other

SO2 monitor is located in these or any neighboring counties.

Figure 2. Map of sources, monitors, and intended nonattainment area boundaries in the Pekin, IL

area 

Illinois analyzed the sources that might be contributing to the monitored violation in Pekin. 

Based on this assessment, Illinois recommended that an area consisting of Cincinnati and Pekin 

Townships in Tazewell County be designated as nonattainment. 

EPA believes that Hollis Township in Peoria County also contributes to the violation monitored 

in Tazewell County. E.D. Edwards Station, a power plant operated by Ameren, is located in this 
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township. This source emits approximately 11,000 tons of SO2 per year, in a location that is 

about 4.5 kilometers in a direction that is periodically upwind of the Pekin monitor. 

Based on EPA's technical analysis described below, and based on a monitored violation, EPA is 

intending initially to designate a Pekin nonattainment area consisting of Cincinnati and Pekin

Townships in Tazewell County and Hollis Township in Peoria.

Detailed Assessment

Air Quality Data 

This factor considers the SO2 air quality monitoring data, including the design value (in ppb) 

calculated for the air quality monitor in Tazewell County based on data for the 2009-2011

period. The only other monitor in this part of Illinois is located in Peoria County. The 2010 SO2

NAAQS design values for the Tazewell and Peoria County monitors are shown in Table 4.

Table 4. Air Quality Data in the Pekin Area

County State Recommended

Nonattainment?

Monitor Air Quality 

System ID

Monitor Location SO2 Design Value, 

2009-2011 (ppb)

Peoria No 17-143-0024 40.6874, 89.6069 36

Tazewell Yes 17-179-0004 40.5565, 89.654 211

The Tazewell County monitor shows a violation of the 2010 SO2 NAAQS. Therefore, some area 

in this county and possibly additional areas in surrounding counties must be designated 

nonattainment. The absence of a violating monitor alone is not a sufficient reason to eliminate 

nearby counties as candidates for nonattainment status. 

Emissions and Emissions-Related Data

Evidence of SO2 emissions sources in the vicinity of a violating monitor is an important factor 

for determining whether a nearby area is contributing to a monitored violation. For this factor, 

EPA evaluated county level emission data for SO2 and any growth in SO2 emitting activities 

since the date represented by those emissions data.

Emissions 

The most recent year for which national emissions information was compiled was 2008. Illinois 

reported data indicating that emissions from pertinent sources in 2007 and 2009 were similar to 

emissions in 2008. Therefore, EPA relied on the 2008 National Emissions Inventory (NEI)

emissions data (NEI08V2). 

Table 5 shows total emissions of SO2 (given in tons per year) for Tazewell County and for 

adjoining Peoria County. Table 5 also shows pertinent information for sources in these counties 

emitting greater than 100 tons per year of SO2 according to the 2008 NEI. 
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Table 5. SO2 Emissions in the Pekin Area (NEI08V2)

County Facility Located 

in State 

Recommended 

Nonattainment

Area?

Facility – Total SO2 Air

Emissions NEI08V2

(tons per year)

Facility Location Distance 

to Pekin 

Monitor 

(km)

Total County 

SO2 Emissions 

(tons per year)

Peoria No*

Ameren – E.D. Edwards 

Stn – 11,224 tpy

40.5958, 89.6631 4 14,677

No ADM – 3049 tpy 40.6756, 89.6073 14

No Keystone Steel & Wire –

138 tpy

40.6420, 89.6467 10

Tazewell Yes MWG – Powerton Stn. –

22,355 tpy

40.5408, 89.6786 3 34,415

Yes Aventine Renewable 

Energy – 11,830 tpy

40.5553, 89.6629 1

*This source is included in the nonattainment area that EPA intends to promulgate

The two significant sources in Tazewell County are located in Cincinnati and Pekin Townships, 

respectively, which Illinois has recommended including in the Pekin nonattainment area. Illinois 

does not recommend including any of Peoria County in this nonattainment area. However, EPA 

finds that Ameren’s E.D. Edwards power plant is only 4 kilometers from the monitor and has 

significant emissions with potential to have significant impact on concentrations at the monitor. 

This source is located in Hollis Township, and so this township warrants being considered an 

area that contributes to the violation measured in Pekin.

Emissions Controls

The emissions data used by EPA in this technical analysis and provided in Table 5 represent 

emissions levels taking into account any control strategies implemented on stationary sources in 

this area up to and including 2008. EPA has not received any additional information on 

emissions reductions resulting from controls put into place after 2008.

Meteorology (weather/transport patterns)

When considering a one-hour standard, violations can occur at anytime, even when weather 

patterns are varied from the normal trends of the area. For this area, wind patterns can be from 

any direction. Therefore, for a one-hour standard, it is useful to consider all directions to have 

potential contribution. The wind rose provided by Illinois suggests that winds come most 

frequently from the south, and somewhat frequently from the northwest, but winds come from all 

directions with sufficient frequency to suggest that meteorology is not a significant factor in 

defining this nonattainment area.
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Geography/topography (mountain ranges or other air basin boundaries)

The Pekin area does not have any geographical or topographical barriers significantly limiting air 

pollution transport within its airshed. Therefore, this factor did not play a significant role in 

determining the nonattainment boundary.

Jurisdictional boundaries 

Illinois does not have any current SO2 nonattainment areas. Townships in Illinois have well 

established boundaries and are a suitable basis for defining nonattainment areas.

Other Relevant Information

EPA did not receive additional information relevant to establishing a nonattainment area 

boundary for this area.

Conclusion

Illinois’ recommendation to define the Pekin, IL nonattainment area to include Cincinnati and 

Pekin Townships of Tazewell County appropriately includes the portions of Tazewell County 

that are contributing to the measured violation and the area known to be violating the standard. 

However, EPA believes that the initial nonattainment area based on monitored violations should 

also include Hollis Township in Peoria County, which includes Ameren’s E.D. Edwards Station. 

This source has substantial emissions relatively close to the monitor measuring a violation. 

Therefore, EPA believes that Hollis Township of Peoria County warrants inclusion in the Pekin 

nonattainment area. Thus, after considering the factors described above, EPA intends initially to 

designate an area that includes Cincinnati and Pekin Townships in Tazewell County and Hollis 

Township in Peoria County as the Pekin, IL nonattainment area for the 2010 SO2 NAAQS.