Maintenance Plan for the

Metro-East St. Louis Ozone Nonattainment Area

for the 1997 8-Hour Ozone 

National Ambient Air Quality Standard

(Revised)

AQPSTR 11-05

August 18, 2011

Illinois Environmental Protection Agency

1021 North Grand Avenue East

Springfield, Illinois 62794-9276
i

TABLE OF CONTENTS

 Page

LIST OF TABLES . . . . . . . . . iii

LIST OF FIGURES . . . . . . . . . iv

EXECUTIVE SUMMARY . . . . . . . . 5

1.0 INTRODUCTION . . . . . . . . 6

1.1 Regulatory Background . . . . . . 6

1.2 Status of Air Quality . . . . . . . 8

2.0 REDESIGNATION AND MAINTENANCE PLAN REQUIREMENTS 9

3.0 OZONE MONITORING . . . . . . . 11

3.1 Monitored Design Values . . . . . . 11

3.2 Quality Assurance . . . . . . . 13

3.3 Continued Monitoring . . . . . . 13

4.0 EMISSIONS INVENTORY. . . . . . . 14

4.1 Attainment Year Inventory – 2008 . . . . . 14

4.2 Air Quality Improvements and Emissions Controls . . . 15

4.3 Emissions Projections. . . . . . . 16

4.4 Demonstration of Maintenance . . . . . 16

4.5 Provisions for Future Updates . . . . . 18

5.0 CONTROL MEASURES AND REGULATIONS . . . 19

5.1 Attainment Demonstration Control Measures . . . 19

5.2 Reasonable Further Progress (RFP) . . . . 20

5.3 Reasonably Available Control Technology (RACT) . . . 20

5.4 Controls to Remain in Effect . . . . . . 21

5.5 Provisions for Permitting New or Modified Emissions Sources . 22

5.6 Transportation Conformity . . . . . . 22

6.0 CONTINGENCY MEASURES . . . . . . 24

6.1 Contingency Measures . . . . . . 24

6.2 Commitment to Revise Plan . . . . . . 26

6.3 Public Participation . . . . . . . 26

6.4 Legal Authority to Implement and Enforce . . . . 27

7.0 CONCLUSIONS . . . . . . . . 28
ii

TABLE OF CONTENTS (Continued)

APPENDIX A Summary of Ambient Air Monitoring Data (2007-2009) . . . 29

APPENDIX B Transportation Conformity . . . . . . . . 31
iii

LIST OF TABLES

Page

Table 4.1 2008 Metro-East Ozone Nonattainment Area

VOM and NOx Emissions . . . . . . 14

Table 4.2 2002 Metro-East Ozone Nonattainment Area

VOM and NOx Emissions . . . . . . 15

Table 4.3 2015 Metro-East Ozone Nonattainment Area

VOM and NOx Emissions . . . . . . 16

Table 4.4 2020 Metro-East Ozone Nonattainment Area

VOM and NOx Emissions . . . . . . 17

Table 4.5 2025 Metro-East Ozone Nonattainment Area

VOM and NOx Emissions . . . . . . 17

Table 4.6 Comparison of 2008, 2015, 2020. and 2025 Emissions Estimates

Metro-East Nonattainment Area . . . . . 17

Table 5.1 Proposed 2008 and 2025 Motor Vehicle Emissions Budgets

Metro-East 8-Hour Ozone Maintenance Plan . . . 23

Table 6.1 Contingency Plan for the Metro-East 8-Hour Ozone

Nonattainment Area . . . . . . . 25
iv

LIST OF FIGURES

Page

Figure 1.1 8-Hour Ozone Nonattainment Area St. Louis, MO-IL. . . 7

Figure 3.1 Ozone Monitors in the St. Louis Metropolitan Area . . . 11

Figure 3.2 Comparison of 8-Hour Ozone Design Values for the 

St. Louis Region Between 2001-2003 and 2007-2009 . . 12
5

EXECUTIVE SUMMARY

This document describes Illinois’ Maintenance Plan for the Illinois portion of the St. 

Louis ozone nonattainment area (NAA), hereafter referred to as the Metro-East NAA. A 

Maintenance Plan is required before an area can be redesignated from nonattainment to 

attainment of a National Ambient Air Quality Standard (NAAQS). This document 

provides technical information required to support a request to redesignate the MetroEast NAA to attainment of the 1997 8-hour ozone NAAQS. This revision incorporates 

motor vehicle emissions estimates developed using the U.S. EPA’s MOVES model. The 

Illinois Environmental Protection Agency (Illinois EPA) has prepared this plan in 

consultation with the Missouri Department of Natural Resources (MDNR) and the U.S. 

EPA. The MDNR is preparing a similar plan for the Missouri portion of the St. Louis

nonattainment area.

Ozone air quality has dramatically improved in the St. Louis region as a result of 

implementation of State and Federal control measures since the designation of the St. 

Louis area as nonattainment in 2004. The entire St. Louis nonattainment area has at least 

three years of complete, quality assured ambient air quality monitoring data for 2007-

2009 that demonstrates compliance with the 1997 8-hour ozone NAAQS. These air 

quality improvements are due to permanent and enforceable emissions control measures.

This Maintenance Plan provides for continued attainment of the 1997 8-hour ozone air 

quality standard for the Metro-East nonattainment area for a period of at least ten years 

after U.S. EPA has formally redesignated the area to attainment. The Plan also provides 

assurances that, even if there is a subsequent violation of the air quality standard, 

measures listed in the Plan will prevent any future occurrences through contingency 

measures that would be triggered upon such an occurrence. Finally, the Plan includes onroad motor vehicle emissions budgets for the years 2008 and 2025 for use in 

transportation conformity determinations to assure that any increases in emissions from 

this sector do not jeopardize continued attainment of the 8-hour ozone standard during 

the maintenance period.
6

1.0 INTRODUCTION

This document describes Illinois’ 8-hour ozone Maintenance Plan for the Metro-East 

NAA. This Maintenance Plan is required before the area can be redesignated from 

nonattainment to attainment of the National Ambient Air Quality Standard (NAAQS) for 

ozone promulgated by the U.S. Environmental Protection Agency (U.S. EPA) in 1997.

Illinois intends to submit such a request to the U.S. EPA in conjunction with this 

Maintenance Plan. The Illinois EPA has prepared this plan in consultation with the 

Missouri Department of Natural Resources (MDNR) and U.S. EPA. The MDNR is

preparing a similar plan for the Missouri portion of the St. Louis nonattainment area. The 

entire St. Louis nonattainment area has at least three years of complete, quality assured

ambient air quality monitoring data for 2007-2009, demonstrating attainment with the 

0.080 ppm 8-hour ozone NAAQS promulgated in 1997.

This document provides the technical information needed to support a request to 

redesignate the St. Louis area to attainment. Section 107 of the Clean Air Act (CAA) 

establishes specific requirements to be met in order for a nonattainment area to be 

considered for redesignation. Before an area can be reclassified to attainment, U.S. EPA 

must make a determination that the area has attained the NAAQS based on at least three 

complete years of ambient monitoring data. U.S. EPA must have approved a State 

Implementation Plan (SIP) for the area under Section 110 and Part D of the CAA. The 

state must demonstrate that the improvement in air quality is due to permanent and 

enforceable reductions in emissions resulting from implementation of the SIP and other 

federal requirements. Finally, the state must submit, and U.S. EPA must approve, a 

Maintenance Plan under Section 175(A) of the CAA, including provisions for 

contingency measures that will be implemented if future violations of the NAAQS are 

measured.

This Maintenance Plan provides for the continued attainment of the 8-hour ozone 

NAAQS for the Metro-East NAA for a minimum of ten years after U.S. EPA has 

formally redesignated the area to attainment. The Plan also provides assurances that even 

if a subsequent violation of the ozone NAAQS occurs, provisions in the Plan will prevent 

any future occurrences through contingency measures that would be triggered upon such 

occurrence.

This document addresses the Maintenance Plan requirements established by the CAA and 

U.S. EPA, and includes additional information to support continued compliance with the 

8-hour ozone NAAQS.

1.1 Regulatory Background

The CAA requires areas that fail to meet the NAAQS for ozone to develop SIPs to 

expeditiously attain and maintain the NAAQS. Historically, exceedances of the ozone 

NAAQS have been monitored in Madison and St. Clair counties in Illinois and in the 

Missouri portion of the NAA.

The Metro-East NAA, which includes Madison, Monroe, St. Clair, and Jersey counties in 

Illinois, was originally designated as nonattainment in 2004 pursuant to the 1997 
7

revisions to the ozone NAAQS. Several counties in Missouri were also designated as 

nonattainment of the 8-hour ozone NAAQS. Figure 1.1 depicts the current St. Louis 

Missouri-Illinois NAA.

Figure 1.1
8

The following is a list of the counties contained in the St. Louis Missouri-Illinois 8-hour

ozone nonattainment area:

Madison County, IL

St. Clair County, IL

Monroe County, IL

Jersey County, IL

St. Louis County, MO

St. Louis City, MO

St Charles, MO

Jefferson County, MO

Franklin County, MO

As a result of the nonattainment designation and the accompanying classification as 

moderate, these areas were subject to new requirements, including development of a plan 

demonstrating that the area would meet the federal 8-hour ozone NAAQS by June 15, 

2010.

Recognizing the need for a regional solution, the States of Illinois and Missouri have 

worked cooperatively to jointly develop and evaluate an effective regional attainment 

strategy to enable the St. Louis region to attain the 8-hour ozone NAAQS. The 

attainment strategy recognizes the importance of reducing both locally generated ozone 

precursor emissions, volatile organic material (VOM) and oxides of nitrogen (NOx), as 

well as incoming (transported) ozone and ozone precursor emissions. The emissions

reductions needed to attain the 8-hour ozone NAAQS include both State and Federal 

measures that have reduced ozone precursor emissions both locally and regionally. 

These measures have allowed the St. Louis Missouri-Illinois NAA to attain the 8-hour 

ozone standard by the attainment deadline established by the U.S. EPA.

1.2 Status of Air Quality

Ozone monitoring data for the most recent three-year period, 2007 through 2009, 

demonstrates that air quality has met the 1997 8-hour ozone NAAQS in the St. Louis 

Missouri-Illinois NAA. Information regarding the air monitoring network and air quality 

monitoring data in included in Section 3.0 and Appendix A.
9

2.0 REDESIGNATION AND MAINTENANCE PLAN REQUIREMENTS

Sections 107 and 110 of the CAA list a number of requirements that must be met by 

nonattainment areas prior to consideration for redesignation to attainment. One of those 

requirements is the development of a Maintenance Plan, which describes a state’s plan 

for maintaining the NAAQS for a minimum ten-year period after redesignation to 

attainment. U.S. EPA has published guidance for the preparation of Maintenance Plans 

and redesignation requests, contained in a document entitled ―Procedures for Processing 

Requests to Redesignate Areas to Attainment‖ (September 4, 1992).

Before a redesignation to attainment can be promulgated, U.S. EPA must:

Determine that the NAAQS for ozone, as published in 40 CFR 50.4, has been 

attained. Ozone monitoring data must show that violations of the NAAQS are no 

longer occurring. This showing must rely on three consecutive years of data. The 

ambient air monitoring data must be quality assured in accordance with 40 CFR 

58.10, recorded in U.S. EPA’s Air Quality System (AQS) data base, and made

available to the public.

Approve the state’s plan for demonstrating attainment. The attainment plan, 

which is based on air quality modeling, must contain enforceable control 

measures and must be submitted as a revision to the state’s SIP after a public 

hearing.

Determine that the improvement in air quality between the year violations 

occurred and the year that attainment was achieved is based on permanent and 

enforceable emissions reductions.

Approve the state’s Maintenance Plan. The requirements for the Maintenance 

Plan are discussed below.

Determine that all other requirements applicable to nonattainment areas have been 

met.

A Maintenance Plan provides for the continued attainment of the 8-hour ozone NAAQS 

for a nonattainment area for a period of at least ten years after U.S. EPA has formally 

redesignated the area to attainment. The plan also provides assurances that even if a 

subsequent violation of the NAAQS occurs, provisions in the plan will prevent any future 

occurrences through contingency measures that would be triggered upon such 

occurrence. To be approvable, the state is required to have a public comment period and 

provide the opportunity for a public hearing on the Maintenance Plan prior to adoption. 

The Maintenance Plan must contain the following elements:

A comprehensive emissions inventory of the precursors of ozone completed for 

the ―attainment year‖;
10

A projection of the emissions inventory forward to a year at least ten years after 

redesignation and a demonstration that the projected level of emissions is 

sufficient to maintain attainment of the ozone NAAQS;

A commitment that, once redesignated, the state will continue to operate an 

appropriate monitoring network to verify maintenance of the attainment status;

A demonstration of legal authority to implement and enforce all control measures 

contained in the SIP;

Provisions for future updates of the inventory to enable tracking of emissions

levels, including an annual emissions statement from major sources;

Motor vehicle emissions budgets for transportation conformity for the 

maintenance period;

A commitment to submit a revised Maintenance Plan eight years after 

redesignation;

A commitment to enact and implement additional contingency control measures 

expeditiously in the event that future violations of the NAAQS occur;

A list of potential contingency measures that would be implemented in such an 

event.

This 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 following sections of this document describe how U.S. EPA’s requirements have 

been met.
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3.0 OZONE MONITORING

U.S. EPA’s published guidance document, ―Procedures for Processing Requests to 

Redesignate Areas to Attainment‖ (September 4, 1992), details specific requirements 

regarding the collection and use of ambient air monitoring data needed to support a 

redesignation request. Before the Metro-East NAA can be redesignated, Illinois must 

demonstrate that the 8-hour ozone NAAQS has been attained. Ozone monitoring data 

must show that violations of the NAAQS are no longer occurring within the 

nonattainment area. This showing must rely on three complete, consecutive calendar 

years of quality assured data. Further, the air monitoring data must be quality assured in 

accordance with 40 CFR 58.10, recorded in U.S. EPA’s AQS data base, and made 

available to the public. Finally, Illinois must commit to continue to operate an 

appropriate monitoring network to verify the maintenance of the attainment status, once 

the area has been redesignated.

The following subsections describe how each of these requirements has been addressed.

3.1 Monitored Design Values

Currently there are 11 ozone monitors located in the nonattainment counties in the St. 

Louis region; 6 are located in Missouri and 5 are in Illinois. Missouri and Illinois also 

operate ozone monitors at locations upwind and downwind of the metropolitan area. 

Figure 3.1 shows the locations of these monitors. 

Figure 3.1 Ozone Monitors in the St. Louis Area
12

To determine whether the NAAQS is being exceeded, the 8-hour ozone design value 

must be calculated. The current U.S. EPA method for calculating the ozone design value 

is to average each monitor’s 4

th highest daily maximum 8-hour value for each year over 

the 3-year period and compare the calculated design values to the 0.080 ppm (or 85 ppb) 

level of the NAAQS. The calculated 8-hour ozone design values for the monitors in the 

St. Louis Missouri-Illinois NAA for 2007-2009 are included as Appendix A of this 

report. Figure 3.2 compares the design values for the 2001-2003 period for monitoring 

stations in the St. Louis region to the corresponding design values from 2007-2009. The 

data demonstrate that ozone air quality has improved dramatically throughout the St. 

Louis region and that the 1997 8-hour ozone NAAQS has been attained for the 2007-

2009 period at all locations.

Figure 3.2

Comparison of 8-Hour Ozone Design Values (ppb) for the St. Louis Region

Between 2001-2003 and 2007-2009

 2001-2003 2007-2009 
13

3.2 Quality Assurance

Illinois EPA has quality assured all monitoring data shown in Appendix A for all sites 

located in Illinois in accordance with 40 CFR 58.10 and the Illinois EPA ’s Quality 

Assurance Plan, which describes Illinois EPA’s standard operating procedures for 

operating the ambient monitoring network and validating the data. The Missouri DNR 

has a similar quality assurance plan. Illinois EPA has recorded the monitoring data in the 

U.S. EPA’s AQS database, which is available to the public.

3.3 Continued Monitoring

Illinois commits to continue monitoring ozone levels according to a U.S. EPA approved 

monitoring plan, as required to ensure maintenance of the ozone NAAQS. Should 

changes in the location of an ozone monitor become necessary, Illinois EPA will work 

with U.S. EPA to ensure the adequacy of the monitoring network. Illinois EPA will 

continue to quality assure the monitoring data to meet the requirements of 40 CFR 58. 

Illinois EPA will continue to enter all data into AQS on a timely basis in accordance with 

federal guidelines.
14

4.0 EMISSIONS INVENTORY

A redesignation request must contain a demonstration that the improvement in air quality 

between the year that violations occurred and the year that attainment was achieved is 

based on permanent and enforceable emissions reductions. As described previously in 

Section 3.0, a three-year monitoring period is used to evaluate whether attainment has 

been achieved. In this Section, the ―attainment year‖ refers to the mid-point year (2008) 

of the three-year period (2007-2009) used to demonstrate attainment. The request should 

also include a projection of the emissions inventory to a year at least 10 years following 

redesignation, a demonstration that the projected level of emissions is sufficient to 

maintain the ozone NAAQS, and a commitment to provide future updates of the 

inventory to enable tracking of emissions levels during the 10-year maintenance period.

4.1 Attainment Year Inventory - 2008

Illinois EPA has prepared a comprehensive emissions inventory for the Metro-East ozone 

nonattainment area, including point, area, and on-road and off-road mobile sources for 

precursors of ozone (VOM and NOx) for the attainment year, 2008. This inventory is 

based on actual or projected activity levels. Point source information was compiled from 

2008 annual emissions reports submitted to the Illinois EPA by emissions sources and the 

U.S. EPA’s Clean Air Markets Division database for electric utilities. Area source 

emissions were calculated using the most recently available methodologies and emissions

factors from U.S. EPA along with activity data (typically population, employment, fuel 

use, etc.) specific to 2008. On-road mobile source emissions were calculated using U.S. 

EPA’s MOVES emissions model with 2008 vehicle miles traveled (VMT) data provided 

by the Illinois Department of Transportation (IDOT). Off-road mobile source emissions 

were calculated for summer 2008 using U.S. EPA’s NONROAD emissions model.

Biogenic emissions are not included in these summaries. 

Table 4.1 summarizes the 2008 emissions estimates for the Metro-East ozone 

nonattainment area. This summary has been revised to incorporate emissions estimates 

for on-road mobile sources using U.S. EPA’s MOVES model.

Table 4.1

2008 Metro-East Ozone Nonattainment Area

VOM and NOx Emissions

(Emissions stated in tons per ozone season weekday)

Source Category VOM NOx

Point Sources 11.92 39.86

Area Sources 23.21 1.50

On-Road Mobile Sources 17.27 52.57

Off-Road Mobile Sources 12.66 39.25

Total 65.06 133.18
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4.2 Air Quality Improvements and Emissions Controls

The Metro-East area was designated as nonattainment of the 1997 8-hour ozone NAAQS

in 2004, based on ozone air quality monitoring data collected between 2001 and 2003. 

Since that time, permanent and enforceable reductions of ozone precursor emissions have 

contributed to improvements in ozone air quality and to the attainment of the 8-hour 

ozone NAAQS. Some of these emissions reductions were due to the application of 

tighter federal emissions standards on motor vehicles and fuels, and some due to the 

requirements of the federal NOx SIP Call. Section 5.0 of this report describes these 

reductions in more detail, along with an explanation of their regulatory status. In this 

subsection, the 2008 attainment year emissions levels are compared to the base year 2002 

emissions levels.

U.S. EPA’s 8-hour Ozone Implementation Rule required that states with ozone 

nonattainment areas prepare and submit a 2002 base year inventory of anthropogenic 

sources of ozone precursor emissions. This base year inventory included emissions from 

point, area, on-road mobile and off-road mobile emissions. Illinois EPA prepared and 

submitted this inventory in June 2006. Table 4.2 summarizes 2002 emissions by major 

source category and by pollutant for the Metro-East NAA. This summary has been 

revised to incorporate emissions estimates for on-road mobile sources using U.S. EPA’s 

MOVES model.

Table 4.2

2002 Metro-East Ozone Nonattainment Area

VOM and NOx Emissions

(Emissions stated in tons per ozone season weekday)

Source Category VOM NOx

Point Sources 17.41 53.24

Area Sources 29.86 1.40

On-Road Mobile Sources 25.90 76.82

Off-Road Mobile Sources 12.04 36.79

Total 85.21 168.25

Comparing the 2002 inventory to that for 2008 indicates that total VOM emissions in the 

Metro-East area decreased by 20.15 tons per day (tpd), due largely to reductions from 

point and on-road mobile sources. NOx emissions in the Metro-East area decreased 

significantly, 35.07 tpd, during the same time period. Again, these reductions were 

primarily from point and on-road mobile sources. These sizeable emissions reductions in 

ozone precursor emissions, and corresponding reductions in the Missouri portion of the 

NAA, plus reductions in upwind areas in Illinois and other nearby states, resulted in a 

substantial improvement in ozone air quality in the St. Louis area, ultimately resulting in 

attainment of the 1997 8-hour ozone NAAQS.
16

4.3 Emissions Projections

A Maintenance Plan must contain a demonstration that the level of emissions projected 

for the ten-year period following redesignation are sufficient to maintain the NAAQS. 

Accordingly, Illinois EPA has projected VOM and NOx emissions for the Metro-East

NAA for 2025. Illinois EPA has also projected emissions to 2015 and 2020, to represent 

two midpoint years during the maintenance period. Emissions for these three projection 

years are compared to emissions levels in 2008 to determine if emissions are sufficient to 

maintain the NAAQS during this period.

Metro-East area point and area source emissions for 2015, 2020, and 2025 were 

estimated using the 2008 base year inventory and growth factors appropriate for each 

source category. Off-road emissions projections were developed using the growth factors 

contained in U.S. EPA’s NONROAD model. On-road motor vehicle emissions were 

estimated using U.S. EPA’s MOVES motor vehicle emissions model. The figures 

assume the continued use of reformulated gasoline, the continued phase-in of the Tier 2 

motor vehicle emissions standards, and operation of an enhanced vehicle inspection and 

maintenance (I/M) program. Total vehicle miles of travel (VMT) for 2015, 2020, and

2025 were assumed to increase at a rate of 1.5 percent per year from 2008.

Tables 4.3, 4.4, and 4.5 include the VOM and NOx emissions estimates for the years 

2015, 2020, and 2025, respectively, for the Metro-East nonattainment area.

Table 4.3

2015 Metro-East Ozone Nonattainment Area

VOM and NOx Emissions

(Emissions stated in tons per ozone season weekday)

Source Category VOM NOx

Point Sources 13.70 31.86

Area Sources 23.76 1.55

On-Road Mobile Sources 9.11 27.85

Off-Road Mobile Sources 9.27 36.41

Total 55.84 97.67

4.4 Demonstration of Maintenance

Table 4.6 demonstrates that the level of emissions projected for the ten-year period 

following redesignation is sufficient to maintain the ozone NAAQS. As shown in the 

table, both VOM and NOx emissions within the nonattainment area are expected to 

decrease significantly between 2008 and 2025. Projected VOM and NOx emissions for 

the mid-point years, 2015 and 2020, are also less than the emissions levels in 2008. 
17

Based on these emissions trends it is expected that air quality will continue to meet the 

1997 8-hour ozone NAAQS throughout the maintenance period.

Table 4.4

2020 Metro-East Ozone Nonattainment Area

VOM and NOx Emissions

(Emissions stated in tons per ozone season weekday)

Source Category VOM NOx

Point Sources 14.73 30.71

Area Sources 25.04 1.56

On-Road Mobile Sources 4.99 16.32

Off-Road Mobile Sources 7.73 33.56

Total 52.49 82.15

Table 4.5

2025 Metro-East Ozone Nonattainment Area

VOM and NOx Emissions

(Emissions stated in tons per ozone season weekday)

Source Category VOM NOx

Point Sources 15.78 32.12

Area Sources 26.32 1.58

On-Road Mobile Sources 5.68 15.22

Off-Road Mobile Sources 7.31 32.33

Total 55.09 81.25

Table 4.6

Comparison of 2008, 2015, 2020, and 2025 Emissions Estimates 

Metro-East Nonattainment Area

(Emissions stated in tons per ozone season weekday)

2008 2015

Difference

(2008 – 2015) 2020

Difference

(2008 – 2020) 2025

Difference

(2008 – 2025)

VOM 65.06 55.84 9.22 52.49 12.57 55.09 9.97

NOx 133.18 97.67 35.51 82.15 51.03 81.25 51.93

In addition to the overall emissions reductions projected to occur within the 

nonattainment area, significant reductions of statewide NOx emissions resulting from 
18

implementation of Illinois’ multi-pollutant standards affecting electric utilities by 2012, 

will also help to ensure continued attainment of the 8-hour ozone NAAQS.

4.5 Provisions for Future Updates

As required by Section 175A(b) of the CAA, Illinois commits to submit to U.S. EPA, 

eight years after redesignation, a revised version of this Maintenance Plan. The revision 

will contain Illinois’ plan for maintaining the 8-hour ozone NAAQS for ten years beyond 

the first 10-year period after redesignation.
19

5.0 CONTROL MEASURES AND REGULATIONS

This section provides specific information on the control measures implemented in the 

Metro-East nonattainment area, including the measures that were part of Illinois’ 

Attainment Demonstration, Reasonable Further Progress (RFP) demonstration, CAA 

requirements, and other state and federal measures. The control measures required in 

past ozone SIP revisions have been fully implemented, and other, more recent control 

programs will continue to provide emissions reductions in future years. Illinois EPA 

commits to keep these measures in effect after redesignation, or to provide equivalent 

emissions levels using alternate measures. Illinois’ SIP contains acceptable provisions to 

provide for preconstruction review of new emissions sources. After redesignation to 

attainment, Prevention of Significant Deterioration (PSD) requirements will apply to the 

construction of new major sources and to significant modifications of existing sources. 

Illinois has accepted delegation from U.S. EPA of this program. Illinois further commits 

to continue to require that all future transportation plans in the St. Louis area conform 

with the SIP.

5.1 Attainment Demonstration Control Measures

Illinois’ attainment demonstration for the Metro-East nonattainment area identified

control measures that had been promulgated at either the state or federal level that are 

sufficient to allow the region to meet the 1997 8-hour ozone NAAQS by the required 

attainment date. The attainment demonstration, which was submitted to U.S. EPA after a 

public hearing and public comment period, is described in the Illinois EPA’s document: 

―8-Hour Ozone Attainment Demonstration for the Metro-East Nonattainment Area‖ 

(Report Number AQPSTR 07-02, June 15, 2007). The primary emissions reduction 

measures for demonstrating attainment of the ozone standard are as follows:

NOx SIP Call and Clean Air Interstate Rule (CAIR)

New Source Performance Standards (NSPS) and National Emissions Standards 

for Hazardous Air Pollutants (NESHAPS)/Maximum Achievable Control 

Technology (MACT) Standards 

VOM Solvent Categories: Aerosol Coatings, Architectural and Industrial 

Maintenance (AIM) Coatings, Consumer Solvents 

Vehicle I/M Program 

Reformulated Gasoline 

Tier 2 Motor Vehicle Emissions Standards and Gasoline Sulfur Control 

Requirements
20

On-Highway Heavy-Duty Engine and Vehicle Standards and Highway Diesel 

Fuel Sulfur Control Requirements

Federal Emissions Standards for Off-Road Equipment (e.g., Nonroad Diesel 

Engine Rule, Evaporative Large Spark Ignition and Recreational Vehicle 

Standards) incorporated into NONROAD Model

Tier 4 Nonroad Diesel Engine Standards and Diesel Fuel Sulfur Content 

Restrictions 

Marine Compression-Ignition Engine Standards and Locomotive Engine 

Standards 

Consent Decrees---Dynegy and ConocoPhillips

5.2 Reasonable Further Progress (RFP)

Since the Metro-East area is classified as a moderate nonattainment area for the 8-hour 

ozone standard, a 15 percent net reduction in ozone precursor emissions from 2002 levels 

was required by 2008 in order to meet the RFP requirement. In the Metro-East 

attainment demonstration, the Illinois EPA relied on NOx substitution to meet the 15 

percent RFP reduction requirement. 

The control measures identified in the RFP document, including those listed above, were 

projected to result in a 6.48 percent reduction in VOM emissions and a 10.01 percent 

reduction in NOx emissions from 2002 levels by the year 2008, a total reduction of 16.49 

percent. All of the identified emissions control measures were implemented by 2008. 

These emissions reductions achieve the 15 percent RFP target for the Metro-East NAA.

5.3 Reasonably Available Control Technology (RACT)

Pursuant to Sections 172, 182(b) and (f) of the CAA, RACT is required for all existing 

major sources of the applicable criteria pollutant and its precursors located in NAAs. 

U.S. EPA defines RACT as the lowest emissions limitation that a particular source is 

capable of meeting by the application of control technology that is reasonably available 

considering technological feasibility and economic reasonableness (70 FR 71612; 

November 29, 2005). The major source threshold for moderate NAAs is defined as 100 

tons per year (tpy). A source generally consists of several units that emit pollutants. The 

sum of emissions from all units at the source determines if a unit is major and thus 

subject to RACT requirements. 

RACT is not a new requirement under the CAA. Illinois previously addressed RACT 

requirements in the Metro-East area in developing attainment plans for the 1-hour ozone 

standard. Illinois has previously adopted RACT requirements for VOM emissions in the 

NAA. (See 35 Ill. Adm. Code Part 219) The Illinois EPA has evaluated the previously 
21

adopted regulations to determine if the RACT requirement is still being met for 8-hour 

ozone. The RACT requirement for NOx was waived for the 1997 8-hour ozone standard, 

based on U.S. EPA’s finding that additional NOx reductions were not needed for the area 

to attain the standard. 

Sections 172, 182(b)(2), and 182(f) of the CAA require implementation of RACT for 

sources that are subject to Control Techniques Guidelines (CTGs) that are promulgated 

by U.S. EPA. The U.S. EPA has issued CTGs defining RACT for those categories of 

sources that emit the greatest amounts of VOM emissions. Illinois EPA has proposed

regulations to implement the revised CTGs issued by the U.S. EPA in 2006, 2007, and 

2008. The 2006 CTG’s addressed industrial cleaning solvents, offset lithographic 

printing and letterpress printing, flexible package printing, and flat wood paneling 

coatings. The 2007 CTG’s address paper, film, and foil coatings, large appliance 

coatings, and metal furniture coatings. The 2008 CTG’s address miscellaneous metal and 

plastic parts coatings, fiberglass boat manufacturing materials, miscellaneous industrial 

adhesives, and automobile and light-duty truck assembly coatings. Other than the above 

mentioned CTGs, Illinois has adopted applicable rules addressing all CTGs published by 

U.S. EPA for which there are existing sources in the Metro-East NAA. 

Non-CTG sources are defined as major VOM sources which are not subject to CTGs, but 

for which RACT is required. All major sources of ozone precursors located in the ozone 

NAA that are not subject to individual RACT rules are subject to a generic RACT rule. 

These rules apply to non-CTG sources that have the potential to emit 100 tons or more 

per year of VOM. Thus, Illinois has met the obligation to implement RACT on non-CTG 

VOM sources in the NAA. 

It should be noted that other regulatory requirements also affect VOM emissions sources 

within the Metro-East ozone NAA. These include MACT, federal NSPS, and NESHAPs. 

These programs satisfy the RACT requirements for specific source categories because 

these rules are more stringent than RACT. It is concluded from this review that Illinois’ 

existing VOM RACT rules fulfill U.S. EPA’s RACT requirements for VOM sources in 

the Metro-East NAA.

As mentioned previously, the RACT requirement for NOx was waived under the 1997 8-

hour ozone NAAQS. Although the Illinois EPA has adopted NOx RACT rules, the 

attainment demonstration for the St. Louis NAA for the 1997 ozone NAAQS did not rely 

on emissions reductions from the Illinois EPA’s NOx RACT rules. The reductions 

resulting from this program, when implemented, will help the area to maintain the 

NAAQS in future years.

5.4 Controls to Remain in Effect

Illinois will maintain all of the control measures listed in this Section to ensure 

maintenance of the 8-hour ozone NAAQS. Any revisions to the control measures 

included as part of the Maintenance Plan will be submitted as a SIP revision to U.S. EPA 
22

for approval, and will be accompanied by a showing that such changes will not interfere 

with maintenance of the NAAQS.

Illinois EPA has the necessary resources to enforce any violations of its rules or permit 

provisions. After redesignation, it intends to continue enforcing all rules that relate to the 

emissions of ozone precursors in the Metro-East nonattainment area.

5.5 Provisions for Permitting New or Modified Emissions Sources

Illinois has longstanding and fully implemented programs for the review of new major 

sources and significant modifications of existing sources. The PSD program, which 

includes requirements for Best Available Control Technology (BACT) on major new 

sources or significant modifications of existing sources, will be applicable in the MetroEast area once the area has been redesignated to attainment. Illinois has been delegated 

full authority to implement the PSD program by U.S. EPA.

5.6 Transportation Conformity

The purpose of this section is to describe and establish the Metro-East nonattainment area 

motor vehicle emissions budgets associated with the 8-hour ozone Maintenance Plan SIP. 

Average summer weekday motor vehicle emissions budgets are being proposed for the 

attainment year 2008 and for the final year of the Maintenance Plan, 2025, for the 

precursor pollutants VOM and NOx. Although motor vehicle emissions were estimated 

for the milestone years of 2015 and 2020, only the 2008 and 2025 estimates are being 

proposed as budgets.

A motor vehicle emissions budget is that portion of the total allowable emissions 

allocated to highway and transit vehicle use that are defined in the SIP for a certain year. 

The rules governing transportation conformity require certain transportation activities to 

be consistent with motor vehicle emissions budgets contained in control strategy 

implementation plans (40 CFR § 93.118). Section 93.101 of the rule defines a ―control 

strategy [State] implementation plan revision‖ as a ―plan which contains specific 

strategies for controlling the emissions and reducing ambient levels of pollutants in order 

to satisfy CAA requirements of reasonable further progress and attainment.‖ In order to 

demonstrate conformity to the motor vehicle emissions budget, emissions from the 

implementation of a transportation plan or a transportation improvement program must 

be less than or equal to the budget level (40 CFR § 93.118(a)).

The motor vehicle emissions budgets established and described herein were developed 

consistent with the methodology and control strategy assumptions used in the 8-hour 

ozone attainment demonstration. The budgets reflect an emissions level determined 

using actual motor vehicle VMT for 2008 and VMT growth at an annual rate of 1.5% 

from year 2008 levels to 2025. The effects of motor vehicle control measures are 

incorporated into the emissions factors produced by the U.S. EPA’s MOVES model. 

These control measures include the implementation of national motor vehicle emissions 

standards, the operation of a vehicle I/M program, and the required use of reformulated 
23

gasoline and low sulfur gasoline and diesel fuel.

The motor vehicle emissions budgets, which reflect the VMT and control program 

assumptions and methodology described here, are listed in Table 5.1.

Table 5.1

Proposed 2008 and 2025 Motor Vehicle Emissions Budgets

Metro-East 8-Hour Ozone Maintenance Plan

(tons per ozone season weekday)

Year VOM NOx

2008 17.27 52.57

2025 5.68 15.22

Additional details on the derivation of the motor vehicle emissions budgets, including 

discussion of the MOVES model inputs and assumptions are included in Appendix B of 

this report.
24

6.0 CONTINGENCY MEASURES

6.1 Contingency Measures

Section 175(A) of the CAA specifies the requirements for Maintenance Plans, including 

provisions for contingency measures that will be implemented if violations of the 8-hour

ozone NAAQS are measured after redesignation to attainment. A list of potential 

contingency measures that would be implemented in such an event should also be 

included in the Maintenance Plan. Finally, the plan should provide a commitment to 

submit a revised Maintenance Plan eight years after redesignation to ensure continued 

maintenance for the next ten-year maintenance period.

Contingency measures are intended to provide further emissions reductions in the event 

that violations of the 8-hour ozone NAAQS occur after redesignation to attainment. 

While these measures do not need to be fully adopted by the Illinois Pollution Control 

Board (IPCB) prior to the occurrence of NAAQS violations, the contingency plan should 

ensure that the contingency measures are adopted expeditiously once they are triggered. 

The Maintenance Plan must identify the triggers that determine when contingency 

measures will be adopted, and the measures that the state will consider.

Illinois EPA’s contingency plan for the Metro-East NAA is described in Table 6.1. 

Consistent with this plan, Illinois agrees to adopt and implement, as expeditiously as 

practicable, the necessary corrective actions in the event that violations of the 8-hour

ozone NAAQS occur within the Metro-East maintenance area after redesignation to 

attainment. Further, Illinois commits to continue to implement the control measures 

identified in the attainment demonstration and RFP demonstration. As described in 

Section 5.0 of this report, Illinois has adopted and is continuing to implement a range of 

control measures that will greatly reduce precursor emissions, both locally and statewide. 

The contingency plan anticipates that these emissions reductions will be sufficient to 

mitigate exceedances or violations of the NAAQS that may occur in the coming years 

without further regulatory action. 

The contingency plan provides for different levels of corrective responses should ambient

8-hour ozone levels exceed the NAAQS in any year, if emissions in the NAA increase 

significantly above current attainment levels, or if the NAAQS is violated. A Level I 

response would occur in the event that: 1) the fourth highest 8-hour ozone concentration

at any monitoring site in the St. Louis NAA (including sites in Missouri and Illinois)

exceeds 84 ppb in any year, or 2) if VOM or NOx emissions increase more than 5% 

above the levels contained in the attainment year (2008) emissions inventory. It should 

be noted that U.S. EPA does not require a state to implement contingency measures when 

occasional exceedances are recorded. The Illinois EPA’s voluntary commitment to 

initiate a Level I response is intended to prevent future violations of the NAAQS from 

ever occurring.

Illinois commits to compiling VOM and NOx emissions inventories for the Metro-East 

area every three years for the duration of the Maintenance Plan to facilitate the 
25

Table 6.1

Contingency Plan for the Metro-East 8-Hour Ozone Nonattainment Area 

 

Contingency Measure 

Trigger Action to be Taken List of Potential Contingency Measures

Level I Trigger

Fourth highest 

monitored 8-hour 

average ozone 

concentration 

exceeding 84 ppb in 

any year at any 

monitoring station in 

the St. Louis MO-IL 

maintenance area.

The Metro-East 

maintenance area’s 

NOx or VOM 

emissions inventories 

increase more than 

5% above the levels 

included in the 2008 

emissions inventories.

IL will evaluate air quality, or 

determine if adverse emissions trends 

are likely to continue. If so, IL will 

determine what and where controls 

may be required, as well as level of 

emissions reductions needed, to avoid a 

violation of the NAAQS. The study 

shall be completed within 9 months. If 

necessary, control measures shall be 

adopted within 18 months of 

determination and implemented as 

expeditiously as practicable, taking into 

consideration the ease of 

implementation and the technical and 

economic feasibility of the selected 

measures. 

Point Source Measures

IL Multi-Pollutant Program for 

electric generating units

NOx RACT

Clean Air Transport Rule, after 

promulgation by USEPA

Best Available Retrofit 

Technology (BART)

Broader geographic applicability 

of existing measures

Mobile Source Measures

Tier 2 Vehicle Standards and Low 

Sulfur Fuel

Heavy Duty Diesel Standards and 

Low Sulfur Diesel Fuel

High-enhanced I/M (OBDII)

Federal railroad/locomotive 

standards

Federal commercial marine vessel 

engine standards

Portable fuel containers

Area Source Measures

Architectural/Industrial 

Maintenance (AIM) Coatings

Commercial and Consumer 

Products

Aerosol coatings

Level II Trigger

A violation of the 

NAAQS at any 

monitoring station in 

the St. Louis MO-IL 

maintenance area.

IL will conduct a thorough analysis to 

determine appropriate measures to 

address the cause of the violation. 

Analysis shall be completed within 6 

months. Selected measures shall be 

implemented within 18 months of a 

violation.

emissions trends analysis included in the contingency plan under Level I. The Illinois 

EPA will coordinate with the Missouri DNR to evaluate the causes of high ozone levels 

or the emissions trends and to determine appropriate control measures needed to assure 

continued attainment of 8-hour ozone NAAQS. Under Level I, measures that could be 

implemented in a short time would be selected so as to be in place quickly after the 

Illinois EPA is aware that corrective measures have been triggered. Control measures 

selected under Level I will be adopted in most cases within 18 months after a 

determination is made, and implemented, generally, within 24 months of adoption by the 

IPCB. 

A Level II response would be implemented in the event that a violation of the 8-hour 

ozone NAAQS were to be measured at a monitoring site within the St. Louis

maintenance area (including sites in Missouri and Illinois). In order to select appropriate 
26

corrective measures, the Illinois EPA will work with the Missouri DNR to conduct a 

comprehensive study to determine the causes of the violation and the control measures 

necessary to mitigate the problem. The analysis will examine the following factors:

the number, location, and severity of the ambient ozone exceedances;

the weather patterns contributing to the elevated ozone levels;

potential contributing emissions sources;

the geographic applicability of possible contingency measures;

emissions trends, including timeliness of implementation of scheduled control 

measures;

current and recently identified control technologies; and

air quality contributions from outside the maintenance area.

Contingency measures will be selected from those listed in Table 6.1 or from any other 

measure deemed appropriate and effective at the time the selection is made. It is 

expected that implementation of only a few of these measures would be necessary. The 

selection between measures will be based upon cost-effectiveness, emissions reduction 

potential, ease and timing of implementation, and other appropriate factors. 

Implementation of necessary controls in response to a Level II trigger will take place as 

expeditiously as possible, but in no event later than 18 months after the Illinois EPA 

makes a determination, based on quality-assured ambient data, that a violation of the 

NAAQS has occurred.

Adoption of additional control measures is subject to necessary administrative and legal

processes. The Illinois EPA will solicit input from all interested and affected persons in 

the area prior to selecting appropriate control measures. No contingency measure will be 

implemented without providing the opportunity for full public participation. This process 

will include publication of notices, an opportunity for public hearing, and other measures 

required by Illinois law.

6.2 Commitment to Revise Plan

As noted in Section 4.5 above, the Illinois EPA commits to review its Maintenance Plan 

eight years after redesignation, as required by Section 175(A) of the CAA. The 

Maintenance Plan revision is intended to ensure continued attainment of the 8-hour ozone 

NAAQS for an additional ten-year period.

6.3 Public Participation

In accordance with Section 110(a)(2) of the CAA, the Illinois EPA is required to have a 

public comment period and provide for the opportunity of a public hearing prior to 

adoption of this Maintenance Plan and submittal to U.S. EPA. Public participation in the 

SIP process was provided for as follows:

Notice of availability of the Metro-East 8-Hour Ozone Maintenance Plan 

document and the time and date of the public hearing was published in the Illinois 
27

Edition of the St. Louis Post Dispatch on July 8, 2011.

If requested, the public hearing to receive comments on the Metro-East 

Maintenance Plan was scheduled for August 18, 2011, at 1:00 p.m. in the 

Sangamo Room at the Illinois EPA’s Headquarters at 1021 N. Grand Ave. East, 

Springfield, Illinois.

A 30-day public comment period was also available after the public hearing to 

receive comments on the Maintenance Plan. A summary of the comments 

received and Illinois EPA’s responses thereto will be included as part of the

submittal to U.S. EPA.

6.4 Legal Authority to Implement and Enforce

The Maintenance Plan must contain a demonstration that the State of Illinois has the 

necessary legal authority to implement and enforce the measures relied upon to attain and 

maintain the NAAQS. Illinois has the legal authority to implement and enforce the 

requirements of this SIP submittal pursuant to the Illinois Environmental Protection Act.
28

7.0 CONCLUSIONS

The Metro-East nonattainment area has attained the 1997 0.080 ppm 8-hour ozone 

NAAQS and has complied with the applicable provisions of the CAA required of 

moderate ozone NAAs. Illinois has submitted an attainment demonstration that was 

based on air quality modeling and contains enforceable control measures. The attainment 

demonstration included an RFP Plan which demonstrated the required 15% reduction in 

ozone precursor emissions. Illinois has performed an analysis that demonstrates that the 

Metro-East NAA has attained the 1997 8-hour ozone NAAQS and believes the air quality 

improvements are due to permanent and enforceable control measures. Supporting 

documentation is contained herein.

The Illinois EPA has prepared a Maintenance Plan that meets the requirement of the 

Clean Air Act. This Maintenance Plan provides for the continued attainment of the 1997 

8-hour ozone NAAQS for a period of ten years after U.S. EPA has formally redesignated 

the area to attainment. This Maintenance Plan provides adequate contingency measures 

for potential, additional emissions reductions in the event that future violations of the 

1997 8-hour ozone NAAQS are observed in the area. 

The Illinois EPA has prepared a comprehensive emissions inventory of the precursors of 

ozone completed for the ―attainment‖ year 2008, and has prepared projections of the 

emissions inventory to 2015, 2020, and 2025. These emissions projections indicate that 

emissions levels in the Metro-East nonattainment area will continue to remain much 

lower than emissions from the attainment year 2008 levels, thereby maintaining the 

ozone NAAQS in future years. The Illinois EPA commits to continue to operate an 

appropriate air quality monitoring network to verify the maintenance of the attainment 

status once the area has been redesignated. The Illinois EPA has the legal authority to 

implement and enforce all control measures.

Finally, the Metro-East Maintenance Plan includes year 2008 and 2025 on-road motor 

vehicle emissions budgets for use in transportation conformity determinations to assure 

that any increases in emissions from this sector do not jeopardize continued attainment of 

the 8-hour ozone standard during the ten-year maintenance period. The Metro-East 

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.
29

APPENDIX A

Summary of Ambient Air Monitoring Data 

(2007-2009)
30

Table A.1

2007-2009 8-hour Ozone Design Values 

for Monitors in the St. Louis Region

State of Missouri

County AQS Code Site Name Design Value 4th High 2007 4th High 2008 4th High 2009

St. Charles 291831004 Orchard Farm 75 83 72 72

St. Charles 291831002 West Alton 78 89 76 71

St. Louis City 295100085 Blair St 75 87 73 65

St. Louis 291890014 Maryland Hts 76 94 69 67

 St. Louis 291890005 Pacific 71 85 64 64

 Jefferson 290990019 Arnold/Arnold W 75 87 70 70

State of Illinois

County AQS Code Site Name Design Value 4th High 2007 4th High 2008 4th High 2009

Jersey 170831001 Jerseyville 70 75 69 68

Madison 171190008 Alton 72 81 68 67

Madison 171193007 Wood River 73 86 67 66

Madison 171191009 Maryville 77 87 70 74

 St. Clair 171630010 E. St. Louis 70 77 64 69
31

APPENDIX B

Transportation Conformity
32

TRANSPORTATION CONFORMITY

This section describes the development of the Metro-East nonattainment area motor 

vehicle emissions budgets associated with the revised Maintenance Plan for the 1997 8-

hour NAAQS. Average summer weekday motor vehicle emissions budgets are being 

proposed for the attainment year 2008 and for the Maintenance Plan year 2025 for the 

ozone precursor pollutants volatile organic material (VOM) and oxides of nitrogen 

(NOx). These budgets were developed consistent with the motor vehicle activity 

assumptions and emissions control strategies incorporated into the Metro-East 8-hour 

ozone Attainment Demonstration analysis. The enclosed budgets were developed using 

emission factors generated by the United States Environmental Protection Agency’s

(U.S.EPA) MOVES model. These emission factors were then multiplied by summer 

weekday vehicle miles of travel (VMT) converted by the model from actual and 

projected annual VMT levels.

Background

Section 176(c)(4) of the Clean Air Act Amendments of 1990 requires that transportation 

plans, programs, and projects which are funded or approved under Title 23 of the United 

States Code (USC) must be determined to conform with State or Federal air 

implementation plans. A motor vehicle emissions budget is that portion of the total 

allowable emissions allocated to highway and transit vehicle use that are defined in the 

SIP for a certain year. Section 93.101 of the rule defines a ―control strategy [State] 

implementation plan revision‖ as a ―plan which contains specific strategies for 

controlling the emissions and reducing ambient levels of pollutants in order to satisfy 

Clean Air Act (CAA) requirements of reasonable further progress and attainment.‖ In 

order to demonstrate conformity to the motor vehicle emissions budget, emissions from 

the implementation of a transportation plan or a transportation improvement program 

(TIP) must be less than or equal to the budget level (40 CFR § 93.118(a)).

Transportation conformity will be determined based on these proposed on-road motor 

vehicle emissions budgets after the U.S. Environmental Protection Agency (U.S. EPA) 

determines that the budgets meet the adequacy criteria of the transportation conformity 

rule under §93.118(e). The motor vehicle emissions budgets in this submittal are 

adequate as each of the six criteria under §93.118(e) is satisfied. These six criteria 

include:

1. The submitted control strategy implementation plan revision or Maintenance Plan 

was endorsed by the Governor (or his or her designee) and was subject to a State 

public hearing.

2. Before the control strategy implementation plan or Maintenance Plan was submitted 

to U.S. EPA, consultation among federal, State, and local agencies occurred; full 

implementation plan documentation was provided to U.S. EPA; and U.S. EPA’s 

stated concerns, if any, were addressed;

3. The motor vehicle emissions budgets(s) is clearly identified and precisely quantified;
33

4. The motor vehicle emissions budget(s), when considered together with all other 

emissions sources, is consistent with all applicable requirements for reasonable 

further progress, attainment, or maintenance (whichever is relevant to the given 

implementation plan submission);

5. The motor vehicle emissions budget(s) is consistent with and clearly related to the 

emissions inventory and the control measures in the submitted control strategy 

implementation plan revision or Maintenance Plan, and

6. Revisions to previously submitted control strategy implementation plans explain and 

document any changes to previously submitted budgets and control measures, 

impacts on point and area source emissions; any changes to established safety 

margins; and reasons for the changes (including the basis for any changes related to 

emissions factors or estimates of vehicle miles traveled).

Regarding adequacy criterion #1, this State Implementation Plan and the associated 

motor vehicle emissions budgets have been developed by the Illinois Environmental 

Protection Agency (Illinois EPA), the designated air quality agency for the State of 

Illinois. The public hearing to accept public comment on the original proposed 

Maintenance Plan and budgets was held on April 8, 2010 in Collinsville, Illinois. 

Notification of this hearing was published in the Belleville News Democrat, East St. 

Louis Monitor, and Alton Telegraph on March 5, 2010 and in the Granite City Press 

Record Journal on March 7, 2010. Comments on the proposed Maintenance Plan and 

associated motor vehicle emissions budgets were accepted for 30 days after the public 

hearing. A ―Responsiveness Summary‖ which addressed the written comments received 

was prepared and included in the submission to the U.S.EPA. 

Regarding this revision to the Metro-East St. Louis 8-Hour Ozone Maintenance Plan and 

MOVES-based motor vehicle emissions budgets, notice of a comment 30-day comment 

period was posted on the Illinois EPA’s website and printed in the Illinois edition of the 

St. Louis Post Dispatch on July 8, 2011. A public hearing to discuss the revised 

Maintenance Plan and associated motor vehicle emissions budgets was to be held on 

August 18, 2011, if it was requested. Comments were required to be postmarked by 

August 8, 2011, unless a public hearing was requested. No request for a public hearing 

was received. All comments were addressed in the attached Responsiveness Summary. 

None of the comments affected the proposed motor vehicle emissions budgets.

In compliance with criterion #2 above, an Inter-Agency Conformity Consultation Team 

meeting was held at the offices of the East-West Gateway Council of Governments on 

January 26, 2010. The Consultation Team includes representatives from the Federal 

Highway Administration, the U.S. EPA, the East-West Gateway Council of Governments

(EWGCOG), the Missouri Department of Transportation, the Missouri Department of 

Natural Resources, the Illinois Department of Transportation (IDOT), and the Illinois 

EPA. At this meeting the development of the proposed Maintenance Plan motor vehicle 

emissions budgets was discussed. The draft Maintenance Plan was also forwarded to the 

U.S. EPA Region V representative for his review and comment. A follow-up meeting of 
34

the Inter-Agency Consultation Team to discuss the revised MOVES-based motor vehicle 

emissions budgets was held on June 14, 2011.

The motor vehicle emissions budgets proposed and described herein were, in compliance 

with adequacy criterion #5, developed consistent with the methodology and control 

strategy assumptions used in the Metro-East 1997 8-Hour Ozone Attainment 

Demonstration as well as the associated Reasonable Further Progress (RFP) plan. The 

effects of these controls are incorporated into the emissions factors produced by the U.S. 

EPA’s MOVES model. In response to adequacy criteria 4 and 6, the narrative of the 

Metro-East 8-Hour Ozone Maintenance Plan discusses the emissions estimates from 

other sectors and any changes in regulations. Following, in response to adequacy criteria 

#3, is a discussion of the inputs and assumptions incorporated into the development of the 

proposed Maintenance Plan motor vehicle emissions budgets.

Vehicle Miles Traveled: The proposed Metro-East 8-Hour Ozone Maintenance Plan 

attainment year 2008 motor vehicle emissions budgets were developed using actual 

annual 2008 county-level vehicle miles travelled (VMT) data from the IDOT. The 2008 

annual VMT for the 4-county (Madison, Monroe, St. Clair and Jersey) Metro-East St. 

Louis 8-hour ozone nonattainment area was 5.878 billion miles. This figure was 

projected to the Maintenance Plan end year, 2025, using an annual growth rate of 1.5 

percent, yielding an annual VMT of 7.57 billion. These annual VMT figures are model 

inputs and converted to summer weekday levels. 

Following is a summary of the information and MOVES model assumptions used in the 

development of the draft motor vehicle emissions budgets.

Meteorological Data: U.S. EPA guidance for the use of the MOVES model requires 

the use of local temperature and absolute humidity data. Average 2008 maximum and 

minimum monthly temperatures for the region were obtained from the National Weather 

Service observations for St. Louis Lambert Airport. Corresponding absolute humidity 

levels were determined for the observed temperatures. These 2008 temperatures and 

absolute humidity values were used in the year 2025 emissions modeling.

Motor Vehicle Emissions Controls: Beyond the U.S. EPA’s federal motor vehicle 

control program emissions standards, the primary local motor vehicle emissions control 

programs that were in place in the Metro-East NAA in 2008 and are projected to still be 

required are a vehicle I/M program and the required use of Reformulated Gasoline.

Inspection and Maintenance (I/M): The Illinois I/M program in effect since 

2007 requires biennial On-Board Diagnostics II (OBD) testing on all model year (MY) 

1996 and newer (MY96+) light-duty gasoline vehicles, and biennial exhaust idle and gas 

cap testing on MY96+ heavy duty gasoline vehicles including gasoline-powered buses, 

registered in the I/M testable area. Motorcycles and diesel vehicles are not subject to 

I/M. The program includes a 4-year grace period for new vehicles. This post-2007 I/M 

program was established when the Illinois legislature amended the Illinois Vehicle 

Inspection law in 2005 to (a) end dynamometer testing of vehicles, (b) require an OBDbased program beginning in February 2007, and (c) remove the requirement for testing 
35

compliant pre-MY96 vehicles. 

The Metro-East vehicle testing domain includes the urbanized areas in Madison, Monroe 

and St. Clair Counties. There are no urbanized areas in Jersey County. An ―I/M 

Coverage‖ percentage was developed based on the amount of VMT from vehicles subject 

to the inspection program compared to total area VMT. The I/M Coverage percentage 

for the Metro-East 8-hour ozone nonattainment area is 84%. 

Fuels: The use of federal Reformulated Gasoline (RFG) has been required in the 

Metro-East St. Louis NAA since 2007 and the St. Louis, Missouri area since 2001. Since 

the Metro-East NAA is a part of the St. Louis NAA, classified a ―southern‖ area for 

purposes of motor fuel control programs, southern grade RFG is required and assumed to 

be used in the Metro-East area. The 8-hour ozone Attainment Demonstration assumed 

the use of southern grade RFG in 2008 and beyond. RFG was assumed to contain 10% 

ethanol. The MOVES model can account for other fuels, such as E85, natural gas, 

methanol, etc, but for all practical purposes the gallons of such alternative fuels and 

hence the number of vehicles using them is very small compared to the number of 

gasoline and diesel vehicles, therefore, the use of such fuels was not considered.

Gasoline Sulfur: The federal Tier 2 regulations require gasoline sulfur levels to 

average no greater than 30 parts per million (ppm) with a maximum of 80 ppm 

beginning in 2007. There are no Illinois gasoline sulfur requirements. Therefore, 

the MOVES gasoline sulfur levels were used in the emissions modeling.

Diesel Sulfur: The federal Tier 2 regulations limit the level of sulfur in diesel 

fuel requiring on- highway diesel fuel to 15 ppm beginning in 2006. There are no 

Illinois diesel sulfur requirements. Therefore, the MOVES diesel sulfur levels 

were used in the emissions modeling.

Fuel Volatility: The volatility of summer RFG, measured as Reid vapor pressure 

(RVP), is not specifically regulated. However, a fuels’ RVP is one of the primary 

characteristics controlled in order to meet the RFG performance standards. 

Therefore, the MOVES RVP levels were used in the emissions modeling.

Registration Distribution: The Registration Distribution (RD) is the fraction of vehicles 

of a given vehicle type and age in the fleet of vehicles of that type as a whole. Different 

vehicle types have different RDs A Metro-East area-specific vehicle registration 

distribution profile based upon 2008 information data was developed by Illinois EPA’s 

Division of Mobile Source Programs from data provided by the Illinois Secretary of 

State’s Department of Motor Vehicles. This profile is assumed to remain valid for 2025.

Source Type Population represents the number of vehicles of each MOVES vehicle type 

in the fleet as a whole within the area under consideration. Accurate local source-type 

populations were not available; therefore the MOVES default fractions modified by 

VMTs by vehicle type were used.
36

VMT Temporal Fractions are the VMT fractions of annual VMT by month of the year, 

of weekly VMT by day of the week, and daily VMT by hour of the day. The Illinois 

EPA uses temporal fractions derived from data collected from continuous count stations 

and presented by IDOT. Temporal fractions vary by road type.

Speed distributions are the fractions of VMT on a given road type by given vehicle 

types in various speed ranges (bins). Thus, on a typical Urban Arterial, a small fraction 

of the vehicles are traveling at less than 10 mph (plus or minus 5 mph), more at 20 mph, 

more at 30mph, most at 40 mph, less at 50 mph, and so on. These fractions differ by 

hour of the day—in more congested conditions during rush hours, the maximum fraction 

might be in the 30 mph range rather than the 40 mph range. The Illinois EPA relied on 

the MOVES model default speed distributions when aggregating emissions (or emission 

rates) for vehicles at different speeds. 

Ramp fraction is the fraction of total VMT on limited-access highways such as 

Interstates that is from on- and off-ramps to or from those highways. Driving on limitedaccess highways is more or less at uniform speed, but driving on ramps involves 

considerable acceleration and deceleration; and these speed changes affect emissions. 

The default MOVES Ramp Fractions are 15% on Rural Interstates, 10% on Urban 

Interstates, and 2% on Other Freeways and Expressways. Illinois does not have actual or 

observed Ramp Fraction data; therefore the MOVES default values were used.

Road Type Distribution is the (fraction of) VMT on different road categories within an 

area under consideration. The Illinois EPA uses VMT data by HPMS functional class 

(FC) published by IDOT as the basis of its emission calculations. The Road Type 

Distribution for Rural Interstates in a county is the county’s Rural Interstate VMT 

divided by the county’s total all-road-type VMT. Similar calculations can be made for 

MOVES road types and vehicle types.

Motor Vehicle Emissions Budgets

Using the emissions factors and summer weekday VMT generated by the MOVES

model, following are the Attainment Year 2008 and Maintenance Plan Year 2025 MetroEast S. Louis 8-hour ozone motor vehicle emissions budgets for use in determining 

transportation conformity. 

Proposed Metro-East 

8-hour Ozone Maintenance Plan

2008 and 2025

Motor Vehicle Emissions Budgets

(tons per ozone season weekday)

Year VOM NOx

2008 17.27 52.57

2025 5.68 15.22
37
ILLINOIS ENVIRONMENTAL PROTECTION AGENCY 

Notice of Public Comment Period for State Implementation Plan (SIP) Submittals for

the Chicago and Metro-East Ozone Nonattainment Areas 

and the Chicago PM2.5 Nonattainment Area

The Illinois Environmental Protection Agency (Illinois EPA) Bureau of Air is accepting public 

comments on proposed revisions of the Maintenance Plans related to the 1997 8-hour ozone and 

PM2.5 National Ambient Air Quality Standards (NAAQS) and the associated draft motor vehicle 

emissions budgets. The Maintenance Plans contain the State’s plans for maintaining the 8-hour 

ozone and PM2.5 NAAQS for at least 10 years after the U.S. EPA redesignates the areas to 

attainment. 

The Illinois EPA will accept written comments on the revisions to the Maintenance Plans. The 

written comments must be postmarked by August 8, 2011, unless a Public Hearing is requested. 

Comments and requests for hearing should be mailed to: 

Dean Studer, Hearing Officer 

Illinois EPA 

1021 North Grand Avenue, East 

P.O. Box 19276 

Springfield, Illinois 62794-9276 

telephone number: 217/558-8280 or TDD: 217/782-9143. 

If a timely request for a Public Hearing is received by August 11, 2011, a hearing will be held on 

August 18, 2011, at 1:00 p.m. in the Sangamo Room at the Illinois EPA’s Headquarters at 1021 

N. Grand Ave. East, Springfield, Illinois, and the written public comment period will be 

extended to September 16, 2011. 

The Public Hearing will be cancelled unless a written request for a Public Hearing is 

received by the Illinois EPA by U.S. Mail, carrier mail, or hand delivered by August 11, 

2011. Verification or cancellation of the Public Hearing will be posted on August 12, 2011 on 

Illinois EPA’s website at: http://www.epa.state.il.us/public-notices/. 

Copies of these draft SIP submittals may be viewed by the public during regular business hours 

(Monday through Friday 8:30 a.m. until 4:30 p.m, except for State holidays) at the Illinois EPA’s 

Headquarters at 1021 North Grand Avenue East, Springfield, Illinois, as well as on Illinois 

EPA’s website at http://www.epa.state.il.us. No walk-in requests for copies of this material will 

be accommodated, unless advance notice is provided. Requests and public inquiries, including 

verification or cancellation of the Public Hearing, should be directed to Dean Studer, the Illinois 

EPA’s Hearing Officer, at the address and phone number listed above. 

If a hearing request is received, the hearing will be held in accordance with the provisions of the 

Illinois EPA’s “Procedures for Informational and Quasi-Legislative Public Hearings,” set forth at 

35 Ill. Adm. Code 164. Any questions about the hearing procedures, requests for copies of the 
hearing rules, or requests for special need interpreters should be directed to the Hearing Officer 

at the address above. Requests for special needs interpreters must be made by August 11, 2011. 

Illinois EPA is proposing to revise the Maintenance Plans to extend the maintenance period until 

2025, and to establish new motor vehicle emissions budgets for the years 2008 and 2025 for the 

nonattainment areas. When final, the Illinois EPA will submit the revised Maintenance Plans 

and the motor vehicle emissions budgets to the U.S. EPA as SIP revisions to meet the 

requirements of the federal Clean Air Act (CAA). The hearing will satisfy the requirements of 

Section 110(l) of the CAA (42. U.S.C. 7401(l) (public notice for SIP submittals)). 

On May 26, 2010, the Illinois EPA submitted a Maintenance Plan for the Metro-East 

nonattainment area to the United States Environmental Protection Agency (U.S. EPA) and 

requested that U.S. EPA redesignate the Metro-East nonattainment area to attainment of the 1997 

8-hour ozone NAAQS. Similarly, on July 23, 2009, the Illinois EPA submitted a Maintenance 

Plan for the Chicago nonattainment area to the U.S. EPA and requested that U.S. EPA 

redesignate the Chicago nonattainment area to attainment of the 1997 8-hour ozone NAAQS. 

Finally, on October 15, 2010, the Illinois EPA submitted a Maintenance Plan for the Chicago 

nonattainment area to the U.S. EPA and requested that U.S. EPA redesignate the Chicago 

nonattainment area to attainment of the 1997 PM2.5 NAAQS. U.S. EPA is expected to act on the 

redesignation requests concurrently with its final actions on the revised Maintenance Plans. 
Notice of Cancellation of Public Hearing 

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 Nonattainment Areas and the Chicago PM2.5

Nonattainment Area 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 in this matter on August 

18, 2011 conditioned on the receipt of a timely request for Public Hearing. 

Pursuant to the published notice, Illinois EP A is required to post either a Verification of the Public 

Hearing or a Cancellation of the Public Hearing on our website on August 12, 201l. Since no requests 

for public hearing have been received, the public hearing originally scheduled for August 18, 2011 has 

been cancelled. The public comment period has ended but the Illinois EP A will accept any public 

comments in this matter that have been postmarked on or before August 8, 2011. 

Dated: August 12, 2011 

Dean Studer 

Hearing Officer 
















1

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
2
3

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
4

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 
5

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 
6

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, 
7

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’ 
8

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. 
9

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 
10

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. 
11

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.