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ILLINOIS ENVIRONMENTAL PROTECTION AGENCY

BUREAU OF AIR

Responsiveness Summary for

Public Questions and Comments on the 

State Implementation Plan Submittals for the

Chicago 8-Hour Ozone Nonattainment Area,

the Chicago PM2.5 Nonattainment Area, and the 

Metro-East 8-Hour Ozone Nonattainment Area

September 16, 2011
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INTRODUCTION

The Illinois Environmental Protection Agency (Illinois EPA) has prepared Maintenance Plans 

for the Chicago and Metro-East ozone nonattainment areas (NAA). The Maintenance Plans are 

required before the areas can be redesignated from nonattainment to attainment of the 8-hour 

ozone National Ambient Air Quality Standard (NAAQS) promulgated by the U.S. 

Environmental Protection Agency (U.S. EPA) in 1997. Similarly, the Illinois EPA has prepared 

a Maintenance Plan for the Chicago NAA, as required before the areas can be redesignated from 

nonattainment to attainment of the annual NAAQS for fine particulates (PM2.5) promulgated by 

the U.S. EPA in 1997. The Illinois EPA intends to submit requests to the U.S. EPA to 

redesignate the Chicago NAA to attainment for both ozone and PM2.5, and to redesignate the 

Metro-East NAA to attainment for ozone in conjunction with the submittal of these Maintenance 

Plans.

The Maintenance Plans provide for the continued attainment of the 1997 ozone NAAQS for the 

Chicago and Metro-East NAAs, and for the continued attainment of the annual PM2.5 NAAQS 

for the Chicago NAA for a period of at least ten years after U.S. EPA has formally redesignated 

the areas to attainment. The Plans also provide assurances that even if a subsequent violation of 

the NAAQS occurs, provisions in the Plan will prevent any future occurrences through the 

enactment of contingency measures that would be triggered upon such occurrence.

PUBLIC HEARING AND COMMENT PERIOD

On July 8, 2011, the Illinois EPA had the Notice of Public Comment Period for State 

Implementation Plan Submittals for the Chicago and Metro-East ozone NAAs and the Chicago 

PM2.5 NAA published in the Chicago Sun Times and in the Illinois edition of the St. Louis Post 

Dispatch. Provision was also given in the notice for a public hearing to be held on August 18, 

2011, conditioned on the receipt of a timely request for Public Hearing. Since there were no 

requests for a public hearing, the public hearing originally scheduled for August 18, 2011 was 

cancelled. The Illinois EP A posted a notice of Cancellation of the Public Hearing on its website 

on August 12, 2011. As indicated in the Notice of Public Comment, the public comment period 

began on July 8, 2011 and closed on August 8, 2011. 

COMMENTS AND RESPONSES BY THE ILLINOIS EPA

A commenter suggested that the Chicago ozone maintenance plan may not be adequate to 

maintain the NAAQS, noting that U.S. EPA’s Air Quality System (AQS) contains the following 

footnote for the 2008-2010 period for the Chicago NAA: “One or more sites in this area has 

violated the NAAQS prior to 2008-2010 and does not have a valid 2008-2010 design value.” 

The footnote in the cited AQS report occurs when one or more monitors in the NAA do not 

meet the completeness criteria established by U.S. EPA. For the 2008-2010 period, design 

values are not shown in AQS for two monitoring stations in the Chicago area, prompting 

the footnote cited by the commenter. The two sites are located at Wacker and Adams
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Streets in downtown Chicago (site ID: 17-031-0042) and 750 Dundee Road in Northbrook 

(site ID: 17-031-4201). The monitor at Wacker and Adams is located on the 90th floor of 

the Willis Tower (Sears Tower) and is operated as a special purpose monitor during the 

summer months (typically June, July, and August). As a special purpose monitor, the 

measurements are not used for the purpose of determining the areas attainment status. At 

Northbrook, the Illinois EPA has historically operated two instruments to measure ozone 

at the same location. The data from the two instruments are distinguished in AQS by POC 

(Parameter Occurrence Code) Codes 1 and 2. One of the instruments located at 

Northbrook (POC 2) was an experimental open path analyzer that was difficult and 

expensive to maintain, and routinely reported lower ozone values than the co-located 

instrument. The experimental analyzer was discontinued in 2009. The other instrument 

operated at this location is the Federal Reference Method (FRM) ozone monitor (POC 1). 

It has operated normally during 2008-2010, meeting U.S. EPA’s completeness criteria, and 

for which a valid design value for 2008-2010 has been calculated. U.S. EPA confirmed the 

validity and completeness of ozone measurements, and that all monitoring sites in the 

Chicago nonattainment area have three years of data showing attainment of the 1997 ozone 

NAAQS by publishing the Clean Data Determination on April 12, 2011.

A commenter pointed out that: “Clean Air Act (CAA) Section 110(l) prohibits the U.S. EPA 

from approving any SIP revision that may interfere with another NAAQS. 42 U.S.C. § 7410(I). 

However, Illinois EPA has presented no analysis at all to establish that re-designating Chicago 

from nonattainment to attainment and that implementing the maintenance plan will not interfere 

with the 2008 ozone NAAQS of 75 ppb or the 2010 1-hour nitrogen dioxide NAAQS.” 

The Illinois EPA does not agree that a further analysis of the effects of redesignation on 

another NAAQS is required or that U.S. EPA cannot approve the SIP revision without 

such analysis. The Illinois EPA has prepared the Chicago ozone Maintenance Plan 

consistent with U.S. EPA’s published guidance. The document adequately demonstrates

that the 1997 NAAQS for ozone has been attained in the Chicago NAA based on three 

consecutive years of ambient air monitoring data. The plan contains emission estimates of 

the precursors of ozone for the “attainment year” and multiple “projection years” that 

demonstrate that the projected level of emissions is sufficient to maintain the NAAQS. In 

fact, the emissions projections indicate that ozone precursor emissions will decrease 

substantially in future years, ensuring continued attainment and maintenance of the 

NAAQS. The Maintenance Plan provides commitments to maintain and enforce the 

control measures that are already in place, to continue monitoring air quality in the NAAs, 

to prepare periodic updates of the emissions inventories, and to implement contingency 

measures, if needed, to correct future exceedances of the NAAQS. Based on these 

commitments, there is no basis to conclude that approval of the Maintenance Plan will 

cause backsliding of the air pollution control programs that have allowed the NAAs to 

reach attainment with the ozone NAAQS. As Illinois’ Maintenance Plan has been prepared 

in accordance with the requirements specified in U.S. EPA’s guidance document and 

additional guidance received from U.S. EPA staff, the plan is approvable as a SIP revision. 

Further, U.S. EPA has not implemented the 2008 ozone NAAQS, and has decided not to 

tighten the standard before 2013. Should U.S. EPA decide to implement the 2008 ozone 
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standard, or to revise it in the future, Illinois is obligated to address the new ozone NAAQS, 

independent of efforts to redesignate existing NAAs to attainment with the old standard. 

With regard to the 2010 NO2 NAAQS, all ambient monitors in Illinois, including the

Chicago area, are meeting the standard and the Illinois EPA has recommended that all 

counties in Illinois be designated as attainment. U.S. EPA has not yet acted on Illinois’ 

recommendation. As shown in the Maintenance Plan, NOx emissions (a combination of 

compounds that includes NO2) are expected to decrease significantly in future years, so 

there is no basis to conclude that re-designating the Chicago NAA from nonattainment to 

attainment for the ozone NAAQS, and implementing the ozone maintenance plan will 

interfere with attainment or maintenance of the 2010 1-hour NO2 NAAQS. 

A commenter questioned whether air quality improvements were the result of permanent and 

enforceable emission reductions since the NOx SIP Call and CAIR are cap and trade programs, 

and because the NOx SIP Call is no longer in place and CAIR has been vacated by the U.S.

Court of Appeals. 

Illinois EPA agrees that regional emission reductions provided by the NOx SIP Call and 

CAIR yielded significant air quality improvements, and that these programs combined 

with other emission reduction measures helped the Chicago area to meet the 8-hour ozone 

NAAQS. The Illinois EPA does not agree, however, that these measures are not permanent 

and enforceable. Illinois submitted, and U.S. EPA approved, SIP revisions addressing the 

requirements of the NOx SIP Call, and, subsequently, the CAIR program. Beginning in 

2009, the CAIR program maintained the same emissions budgets as the NOx SIP Call 

program it replaced. In its decision to vacate the CAIR, the U.S Court of Appeals 

determined that the CAIR emissions budgets should remain in place, until U.S. EPA 

remedied the identified deficiencies. U.S. EPA recently promulgated the Cross-State Air

Pollution Rule (CSAPR) to address the Court’s concerns. Significantly, the CSAPR

requires that states meet emissions budgets that are more stringent than CAIR, and 

provides new requirements that ensure that emission reductions are achieved within each 

affected state.

A commenter noted that Illinois EPA’s future emission projections did not consider U.S. EPA’s 

recent announcement that it is repealing the vapor capture requirements for gas stations. 

Regarding the Stage II program, on July 15, 2011 the U.S. EPA issued a proposed rule 

determining that June 30, 2013 will be the date when the “widespread use” of onboard 

refueling vapor recovery (ORVR)-equipped vehicles will occur. At this point the U.S. EPA

expects “ORVR alone to achieve emissions reductions equal to Stage II alone” so no 

additional emissions would result from the cessation of the Stage II program. The 

widespread use determination would not obligate states to remove any existing Stage II 

vapor recovery requirements and the Chicago 8-hour ozone Maintenance Plan does not 

propose to end the Stage II program. If at a later date, the Illinois EPA should wish to end 

the Stage II program in Chicago, a revision to the State Implementation Plan (SIP) would 
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have to be adopted and approved by the U.S.EPA demonstrating that no additional 

refueling emissions would result. As Stage II is not required in the Metro-East St. Louis 

area, U.S. EPA’s widespread use determination would have no impact on either regional 

air quality or the Metro-East St. Louis 8-hour ozone Maintenance Plan.

A commenter stated that Illinois EPA’s projection of future emissions decreases from on-road 

motor vehicles is unsupported, and that its emissions calculations from on-road mobile sources 

fail to consider U.S. EPA’s recent decision to allow 15% ethanol in all gas. 

Illinois EPA used the U.S. EPA’s new MOVES2010 model to estimate motor vehicle 

emissions in both the Chicago and Metro-East St. Louis areas. This model incorporates 

emissions factors for all vehicle category types. The model also incorporates local motor 

vehicle registration data and national fleet turnover rate statistics. The reduction in 

estimated NOx emissions results from the introduction of new vehicles complying with the 

Tier 2 motor vehicle emissions standards and the retirement of older vehicles. The Tier 2 

program, phased in beginning in 2004, established more stringent NOx emissions standards

on cars, trucks, and sport utility vehicles. Given the implementation of these significantly 

more stringent emission standards, the estimated reduction in motor vehicle NOx emissions 

is reasonable. 

Regarding the comment regarding the U.S.EPA’s recent decision to allow the blending of 

up to 15% ethanol into conventional gasoline, the use of such fuel is limited to flexiblefueled vehicles and model year (MY) 2001 light-duty cars and trucks, and medium-duty 

passenger vehicles. In its “Notice of Decision Granting a Partial Waiver” (76 FR 4662), the 

U.S.EPA stated that Department of Energy (DOE) testing of MY 2001-2006 light duty 

motor vehicles “strongly supports a determination that E15 will not cause or contribute to 

MY2001-2006 light-duty motor vehicles exceeding their applicable exhaust emission 

standards.” The U.S.EPA further states that “MY 2001-2006 light duty motor vehicles 

should generally be able to meet evaporative emission standards when operated on E15 so 

long as the fuel does not exceed a RVP of 9.0 psi (pounds per square inch)in the 

summertime volatility control season.” The U.S.EPA goes on to state: “...in fact, such 

vehicles should have somewhat lower evaporative emissions when operated on 9.0 psi E15 

than when operated on currently available in-use fuel.”

Regarding MY 2007 and newer vehicles, in its November 4, 2010 “Notice of Partial Waiver 

Decision” (75 FR 68094) the U.S. EPA states that DOE Catalyst Study and other 

information before EPA adequately demonstrates that the impact of E15 on overall 

emissions, including both immediate and durability related emissions, will not cause or 

contribute to violations of the emissions standards for these motor vehicle. Likewise, the 

data and information adequately show that E15 will not lead to violations of the 

evaporative emissions standards, so long as the fuel does not exceed a Reid Vapor Pressure 

(RVP) of 9.0 psi in the summertime control season.” 

The use of reformulated gasoline (RFG) is required in both the Chicago and Metro-East St. 

Louis areas. The summertime volatility of these fuels are in the range of 7.0 psi, well below 

the 9.0 psi level referenced by the U.S.EPA. Based on these statements from the U.S.EPA, 
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the Illinois EPA believes that the use of E15 gasoline blends will not result in any increase 

in emissions in the ozone control season.

A commenter questioned whether ambient monitoring data is available to the public, since U.S. 

EPA and the Illinois EPA apparently do not have timely data available no their respective web 

pages. 

The Illinois EPA submits all ambient monitoring data it collects to U.S. EPA’s Technology 

Transfer System (TTN) Air Quality System (AQS). The AQS Data Mart is a database 

containing all of the information from the AQS system and is available free of charge to the 

public. The AQS Data Mart is available on the internet at:

http://www.epa.gov/ttn/airs/aqsdatamart

U.S. EPA also maintains the following web sites to disseminate air quality data to the 

public:

AirData @ http://www.epa.gov/air/data/index.html

AirExplorer @ http://www.epa.gov/airexplorer/

AirNow @ http://www.airnow.gov/

A commenter pointed out that Chicago Ozone Maintenance Plan failed to consider climate 

change, noting that climate change might cause existing pollution-control measures to become 

inadequate in the future.

The Illinois EPA understands that there is a clear relationship between meteorological 

conditions and ground level ozone levels, and that climate change may affect the frequency 

and severity of ozone-conducive meteorological conditions in future years. Although 

climate change is not directly addressed in the Maintenance Plan, nor is it required to be

addressed, the Maintenance Plan provides contingency measures that will be triggered in 

the event of future NAAQS violations. The Illinois EPA has committed to maintain an 

adequate monitoring network in the Chicago area and to take corrective actions in the 

event of future NAAQS violations, whether caused by normal year-to-year meteorological 

variability, climate induced adverse conditions, or emissions changes that were not 

anticipated in the development of the Maintenance Plan. The Illinois EPA has also 

committed to revise the plan within the next ten years to ensure maintenance of the 

NAAQS.

A commenter stated that the Clean Air Act does not allow for alternative measures in the event 

that current control measures now in effect must be replaced with equivalent emission reduction 

measures.

Illinois EPA does not agree with the commenter’s statement. Section 110(l) of the CAA 

provides for revisions of the SIP as long as the plan does not interfere with attainment or 

reasonable further progress, or other applicable requirements. To be clear, Illinois’ 
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Maintenance Plan does not rely on alternate measures. In fact, the plan clearly states 

Illinois’ commitment to keep existing control measures in place after the Chicago NAA has 

been redesignated to attainment. In the event that future revisions of Illinois’ SIP become 

necessary, the Maintenance Plan commits the state to provide equivalent emissions levels 

using alternate control measures. Such revisions are subject to review and approval by 

U.S. EPA. 

A commenter noted that the summary of Illinois’ Reasonable Further Progress demonstration 

contained in the Chicago 8-hour ozone Maintenance Plan states: “The control measures 

identified in the RFP document ... will result in a 15.7 percent reduction in VOM emissions 

from 2002 emissions levels by the year 2008.” The commenter requested that Illinois EPA must 

prove that these reductions were actually achieved. 

The Illinois EPA does not agree that such a demonstration is required for the Maintenance 

Plan, since there is no such requirement in any guidance published to date by U.S. EPA. 

Further, U.S. EPA has published a Clean Data Determination for the 1997 8-hour ozone 

NAAQS for the Chicago NAA (April 12, 2011), which waives CAA planning requirements, 

including RFP, as long as the nonattainment area continues to meet the NAAQS. However, 

based on this comment, the Illinois EPA has revised the 2002 VOM emission estimates 

contained in the Maintenance Plan (Table 4.2 on page 15). The VOM emission estimates in 

the draft Maintenance Plan for 2002 did not properly account for changes in U.S. EPA’s 

emissions estimation guidance that occurred subsequent to preparation of the 2002 

inventory. U.S. EPA’s guidance for computing emissions from certain area source 

categories, most significantly for graphic arts, consumer solvents, architectural coatings, 

and industrial coatings, changed between 2002 and 2008. Illinois EPA’s 2008 emissions 

estimates were performed using the revised methodology, but the 2002 estimates contained 

in the draft document were based on the earlier methodology. The final document has 

been revised to apply a consistent methodology for all years. Comparing VOM emissions 

in the Chicago NAA from 2002 to 2008 indicates that VOM emissions decreased 

significantly during that period, about 210 tons per day. This amount equates to a 

reduction of about 21%, which exceeds the amount needed to demonstrate RFP. 

Metro-East St. Louis Ozone Maintenance Plan

A commenter suggested that the Metro-East ozone maintenance plan may not be adequate to 

maintain the NAAQS, noting that U.S. EPA’s Air Quality System (AQS) contains the following 

footnote for the 2008-2010 period for the St. Louis NAA: “One or more sites in this area has 

violated the NAAQS prior to 2008-2010 and does not have a valid 2008-2010 design value.” 

The footnote in the cited AQS report occurs when one or more monitors in the NAA do not 

meet the completeness criteria established by U.S. EPA. For the 2008-2010 period, design 

values are not shown in AQS for two monitoring stations (three samplers at two locations) 

in the St. Louis area, prompting the footnote cited by the commenter. The two sites are 

located at 4520 Margaretta in St. Louis, MO (site ID: 29-510-0086) and 4580 South 

Lindbergh in Sunset Hills, MO (site ID: 29-189-004). The Missouri Department of Natural 

Resources (MDNR) discontinued these monitoring stations prior to the 2009 ozone season. 
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These monitors were determined by MDNR and U.S. EPA – Region 7 to be redundant with 

other monitors in the metropolitan area, and did not measure the highest levels of ozone in 

the NAA during the years that they operated at those locations. U.S. EPA requires that 

changes in a state’s monitoring network be identified and approved in advance, and 

contained in the state’s monitoring network plan. MDNR’s 2009 network plan properly 

and timely identified and justified the need to discontinue these sites. By approving the 

changes to MDNR’s monitoring network plan, U.S. EPA determined that the revised 

network was still adequate to characterize ozone air quality in the St. Louis NAA.

A commenter pointed out that: “Clean Air Act (CAA) Section 110(l) prohibits the U.S. EPA 

from approving any SIP revision that may interfere with another NAAQS. 42 U.S.C. § 7410(I). 

However, Illinois EPA has presented no analysis at all to establish that re-designating Metro-East 

from nonattainment to attainment and that implementing the maintenance plan will not interfere 

with the 2008 ozone NAAQS of 75 ppb or the 2010 1-hour nitrogen dioxide NAAQS.” 

The Illinois EPA does not agree that a further analysis of the effects of redesignation on 

another NAAQS is required or that U.S. EPA cannot approve the SIP revision without 

such analysis. The Illinois EPA has prepared the Metro-East ozone Maintenance Plan 

consistent with U.S. EPA’s published guidance. The document adequately demonstrates

that the 1997 NAAQS for ozone has been attained in the St. Louis NAA based on three 

consecutive years of ambient air monitoring data. The plan contains emission estimates of 

the precursors of ozone for the “attainment year” and multiple “projection years” that 

demonstrate that the projected level of emissions is sufficient to maintain the NAAQS. In 

fact, the emissions projections indicate that ozone precursor emissions will decrease 

substantially in future years, ensuring continued attainment and maintenance of the 

NAAQS. The Maintenance Plan provides commitments to maintain and enforce the 

control measures that are already in place, to continue monitoring air quality in the NAAs, 

to prepare periodic updates of the emissions inventories, and to implement contingency 

measures, if needed, to correct future exceedances of the NAAQS. Based on these 

commitments, there is no basis to conclude that approval of the Maintenance Plan will 

cause backsliding of the air pollution control programs that have allowed the NAAs to 

reach attainment with the ozone NAAQS. As Illinois’ Maintenance Plan has been prepared 

in accordance with the requirements specified in U.S. EPA’s guidance document and 

additional guidance received from U.S. EPA staff, the plan is approvable as a SIP revision. 

Further, U.S. EPA has not implemented the 2008 ozone NAAQS, and has decided not to 

tighten the standard before 2013. Should U.S. EPA decide to implement the 2008 ozone 

standard, or to revise it in the future, Illinois is obligated to address the new ozone NAAQS, 

independent of efforts to redesignate existing NAAs to attainment with the old standard. 

With regard to the 2010 NO2 NAAQS, all ambient monitors in Illinois, including the 

Metro-East area, are meeting the standard and the Illinois EPA has recommended that all 

counties in Illinois be designated as attainment. U.S. EPA has not yet acted on Illinois’ 

recommendation. As shown in the Maintenance Plan, NOx emissions (a combination of 

compounds that includes NO2) are expected to decrease significantly in future years, so 

there is no basis to conclude that re-designating the Metro-East NAA from nonattainment 
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to attainment of the ozone NAAQS, and implementing the maintenance plan will interfere 

with the 2010 1-hour nitrogen dioxide NAAQS. 

A commenter questioned whether air quality improvements in the Metro-East area were the 

result of permanent and enforceable emission reductions since the NOx SIP Call and CAIR are 

cap and trade programs, and because the NOx SIP Call is no longer in place and CAIR has been 

vacated by the U.S. Court of Appeals. 

The Illinois EPA believes that these comments have been addressed in its previous 

responses for the Chicago ozone nonattainment area.

A commenter pointed out that Illinois EPA’s emission projections do not account for emissions 

from the Prairie State Generating Station which should be in operation, and thus polluting, prior 

to 2015.

The Prairie State Generating Station is located in Washington County, Illinois and is 

expected to be in operation by 2012. As required, Illinois EPA’s emissions projections 

include only those emissions occurring or projected to occur within the boundaries of the 

nonattainment area, which includes Madison, Monroe, St. Clair, and Jersey counties in 

Illinois. The Illinois EPA acknowledges that the Prairie State Generating Station is located 

in close proximity to the Metro-East ozone nonattainment area and emissions from it will 

cause air quality impacts within the NAA. Before issuing a PSD permit to Prairie State, the 

Illinois EPA required the company to address its potential impact on the St. Louis ozone 

nonattainment area. Prairie State adequately demonstrated that future emissions from the 

facility will not interfere with the area’s ability to attain and maintain the NAAQS. 

A commenter identified the same “defects” in the Metro-East Ozone Maintenance Plan identified 

previously in comments on the Chicago Ozone Maintenance Plan, including: (1) failing to 

consider increased emissions from U.S. EPA’s repealing the vapor capture requirements for gas 

stations and allowing up to 15% ethanol in gasoline; (2) assuming that vehicle turn over will 

reduce mass on-road emissions even though purchasing larger new vehicles can offset this; (3) 

failing to make ambient monitoring data available to the public; (4) failing to consider climate 

change impacts on future ambient ozone levels; (5) relying on unidentified alternate measures 

with no legal authority to do so. 

The Illinois EPA believes that these comments have been addressed in its previous 

responses for the Chicago ozone nonattainment area.

A commenter questioned whether PM2.5 air quality improvements in Chicago were the result of 

permanent and enforceable emission reductions since the NOx SIP Call and CAIR are cap and 

trade programs, and because the NOx SIP Call is no longer in place and CAIR has been vacated 

by the U.S. Court of Appeals. 
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The Illinois EPA believes that this comment has been addressed in its previous responses 

for the Chicago ozone nonattainment area.

A commenter identified the same “defects” in the Chicago PM2.5 Maintenance Plan identified 

previously in comments on the Chicago Ozone Maintenance Plan, including: (1) failing to 

consider increased emission from U.S. EPA’s repealing the vapor capture requirements for gas 

stations and allowing up to 15% ethanol in gasoline; (2) assuming that vehicle turn over will 

reduce mass on-road emissions even though purchasing larger new vehicles offset this; and (3) 

failing to make ambient monitoring data available to the public. 

The Illinois EPA believes that these comments have been addressed in its previous 

responses for the Chicago ozone nonattainment area.