Redesignation Demonstration 

and 

Maintenance Plan for the Missouri Portion of the 

 St. Louis Nonattainment Area for the 

1997 8-Hour Ground-Level Ozone (O3) 

National Ambient Air Quality Standard 

Prepared for the 

Missouri Air Conservation Commission 

Adoption 

October 27, 2011 

Missouri Department of Natural Resources 

Division of Environmental Quality 

Air Pollution Control Program 

Jefferson City, Missouri 
ii 

TABLE OF CONTENTS 

EXECUTIVE SUMMARY ............................................................................................... 1

1. BACKGROUND/INTRODUCTION........................................................................... 2

1.1 NATIONAL AMBIENT AIR QUALITY STANDARD FOR OZONE............................................ 2 

1.2 OZONE AND ITS FORMATION............................................................................................ 3 

1.3 NEGATIVE EFFECTS OF OZONE ........................................................................................ 3 

1.4 GEOGRAPHICAL DESCRIPTION OF THE ST. LOUIS NONATTAINMENT AREA...................... 4 

1.5 ST. LOUIS OZONE HISTORY.............................................................................................. 6 

1.6 CURRENT STATUS / BACKGROUND SUMMARY................................................................. 9 

2. REDESIGNATION AND MAINTENANCE PLAN REQUIREMENTS ............ 10

2.1 ATTAINMENT OF THE STANDARD................................................................................... 10 

2.2 IMPLEMENTATION PLAN APPROVAL .............................................................................. 11 

2.3 PERMANENT AND ENFORCEABLE IMPROVEMENT........................................................... 12 

2.4 MAINTENANCE PLAN REQUIREMENTS ........................................................................... 12 

2.5 SECTION 110 AND PART D REQUIREMENTS ................................................................... 15 

3. OZONE MONITORING........................................................................................... 16

3.1 ST. LOUIS OZONE MONITORING NETWORK ................................................................... 16 

3.2 AMBIENT AIR MONITORING DATA................................................................................. 17 

3.3 ST. LOUIS OZONE MONITORING DATA ANALYSIS ......................................................... 22 

3.4 MISSING DATA UNDER THE 1997 8-HOUR OZONE STANDARD ...................................... 22 

3.5 QUALITY ASSURANCE PROGRAM................................................................................... 23 

3.6 CONTINUED MONITORING COMMITMENT ...................................................................... 23 

3.7 CLEAN DATA DETERMINATION...................................................................................... 23 

4. REDESIGNATION REQUEST: EMISSION INVENTORY AND CONTROLS 

FROM 2002 - 2008 ..................................................................................................... 24

4.1 BASE YEAR AND ATTAINMENT YEAR INVENTORIES ...................................................... 24 

4.2 CONTROLS USED TO ATTAIN THE STANDARD ................................................................ 26 

4.3 REASONABLY AVAILABLE CONTROL TECHNOLOGY (RACT)........................................ 29 

4.4 PERMANENT AND ENFORCEABLE CONTROLS ................................................................. 30 

5. MAINTENANCE PLAN DEMONSTRATION: EMISSION INVENTORY AND 

CONTROLS FROM 2008 - 2022.............................................................................. 32

5.1 BASE/ATTAINMENT YEAR INVENTORY AND FUTURE YEAR EMISSION PROJECTIONS .... 32 

5.2 INTERIM YEAR EMISSION INVENTORY: 2017 ................................................................. 35 

5.3 CONTROLS TO REMAIN IN EFFECT.................................................................................. 36 

5.4 FUTURE FEDERAL CONTROL MEASURES........................................................................ 36 

5.5 PROVISIONS FOR PERMITTING NEW OR MODIFIED EMISSIONS SOURCES........................ 37 

6. TRANSPORTATION CONFORMITY................................................................. 38

7. CONTINGENCY MEASURES............................................................................... 41

8. CONCLUSION........................................................................................................... 44
iii 

LIST OF TABLES

Table 3-1 2007-2010 St. Louis 8-Hour Design Values

Table 4-1 2002 VOC and NOX Emissions for the Missouri Side of the 1997 St. Louis 

8-Hour Ozone Nonattainment Area (tons per ozone season day) 

Table 4-2 2008 VOC and NOX Emissions for the Missouri Side of the 1997 St. Louis 

8-Hour Ozone Nonattainment Area (tons per ozone season day) 

Table 4-3 Comparison of 2002 and 2008 VOC and NOX Emissions for the Missouri Side of 

the 1997 St. Louis 8-Hour Ozone Nonattainment Area (tons per ozone season 

day) 

Table 5-1 2008 VOC and NOX Emissions for the Missouri Side of the 1997 St. Louis 

8-Hour Ozone Nonattainment Area (tons per ozone season day) 

Table 5-2 2022 VOC and NOX Emissions for the Missouri Side of the 1997 St. Louis 

8-Hour Ozone Nonattainment Area (tons per ozone season day) 

Table 5-3 Comparison of 2008 and 2022 VOC and NOX Emissions for the Missouri Side of 

the 1997 St. Louis 8-Hour Ozone Nonattainment Area (tons per ozone season 

day) 

Table 5-4 2017 VOC and NOX Emissions for the Missouri Side of the 1997 St. Louis 

8-Hour Ozone Nonattainment Area (tons per ozone season day) 

Table 6-1 Historical VMT in the Missouri Portion of the 1997 St. Louis 8-Hour Ozone 

Nonattainment Area (State Owned Roads Only) 

Table 6-2 2008 and 2022 Annual VMT by County 

Table 6-3 Motor Vehicle Emissions Budgets for the Missouri Portion of the 1997 St. Louis 

8-Hour Ozone Nonattainment Area 

Table 7-1 Contingency Plan for the Missouri Portion of the 1997 St. Louis 8-Hour Ozone 

Maintenance Area 

Table 7-2 Potential Contingency Measures for the Missouri Portion of the 1997 St. Louis 

8-Hour Ozone Maintenance Area 
iv 

List of Figures 

Figure 1-1 1997 8-Hour Ozone Nonattainment Area for St. Louis (MO-IL) region 

Figure 3-1 St. Louis Ozone Monitoring Network 

Figure 3-2 2001 – 2010 8-Hour Ozone Design Value Trends – MO 

Figure 3-3 2001 – 2010 8-Hour Ozone Design Value Trends – IL 

Figure 3-4 2001 – 2003 & 2008 – 2010 Design Value Comparison 
v 

List of Appendices 

Appendix A 2002 Emission Inventory Summary 

Appendix B 2008 Emission Inventory Summary 

Appendix C 2017 Emission Inventory 

Appendix D 2022 Emission Inventory 

Appendix E 2008 Base Year Emissions Inventory for the Missouri Portion of the 

St Louis Ozone Nonattainment Area 

 Appendix E-1 List of Statewide Point Source Emissions by Facility 

 Appendix E-2 List of Onroad Emissions by SCC for Franklin and Jefferson 

Counties 

 Appendix E-3 List of Onroad Emissions by SCC for St. Charles and St. Louis 

Counties and St. Louis City 

 Appendix E-4 Nonroad Inventory Documentation 

 Appendix E-5 Nonroad Emissions by SCC 

 Appendix E-6 Nonpoint ICI Combustion Methodology 

 Appendix E-7 Temporal Allocation 

 Appendix E-8 EIQ Forms 

Appendix F MEMC Agreement 

Appendix G Retired Unit Exemption Forms for Trigen and Anheuser Busch
1 

EXECUTIVE SUMMARY 

This document outlines the State of Missouri’s Maintenance Plan for Missouri’s portion of the 

St. Louis ozone nonattainment area. Per the federal Clean Air Act Amendments of 1990, 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 St. Louis nonattainment 

area to attainment of the 1997 8-hour ozone NAAQS. This maintenance plan will become part 

of the state’s redesignation request submittal to the U.S. Environmental Protection Agency 

(EPA). The Missouri Department of Natural Resources has prepared this plan in consultation 

with the Illinois Environmental Protection Agency and the U.S. EPA. The Illinois EPA has 

prepared a similar plan for the Metro-East 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 consecutive 

ozone seasons of complete, quality assured ambient air quality monitoring data for 2008-2010 

demonstrating attainment with the 0.080 parts per million (ppm) 8-hour ozone NAAQS 

promulgated in 1997. 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 St. Louis nonattainment area for a period of ten years after the EPA has formally 

redesignated the area to attainment. The plan also provides assurances that, in the event of a 

subsequent violation of the air quality standard, additional control options listed in this plan, 

called contingency measures, can quickly be implemented to prevent any future violations. In 

addition, this plan demonstrates the observed actual emission reductions that have been achieved 

through permanent and enforceable control measures that brought the area back into attainment 

of the NAAQS. This plan also includes an emissions inventory analysis of the ozone precursors 

- Nitrogen Oxides (NOx) and Volatile Organic Compounds (VOCs) – for both the redesignation 

demonstration period (2002- 2008) and the maintenance plan period (2008 – 2022). This 

analysis includes on-road motor vehicle emissions budgets for the 2008 and 2022 for use in 

transportation conformity determinations to assure that any increases in emissions from this 

sector do not jeopardize continued attainment of the 1997 8-hour ozone standard during the tenyear maintenance period in the St. Louis nonattainment area.
2 

1. BACKGROUND/INTRODUCTION 

1.1 National Ambient Air Quality Standard for Ozone

Congress first enacted the Clean Air Act (CAA) in 1970. It was last amended in 1990. The 

CAA requires the U.S. Environmental Protection Agency (EPA) to set National Ambient Air 

Quality Standards (NAAQS) for pollutants considered harmful to public health and the 

environment. There are two categories of NAAQS that are set by the EPA. The primary 

standards are health-based standards and are designed to establish limits to protect public health. 

The secondary standards are commonly referred to as “welfare-based standards” and are meant 

established to protect public welfare. These limits are intended to protect against decreased 

visibility, and damage to crops, animals, and buildings. Currently there are six pollutants with 

established primary level NAAQS. These pollutants are carbon monoxide, lead, total suspended 

particles, sulfur dioxide, nitrogen oxide, and ozone. These pollutants are referred to as “criteria” 

pollutants. The EPA establishes a standard for each criteria pollutant. If an area is found to 

exceed this value, it is classified as a nonattainment area for that specific pollutant. The states 

and/or tribes responsible for the affected area must then develop and carry out strategies and 

measures to attain the NAAQS. The goal is for any areas designated as “nonattainment” to be 

reclassified by the EPA to attainment for the pollutant. 

The CAA requires that the EPA carry out a periodic review of NAAQS for the criteria pollutants. 

This review must include the scientific basis for (1) changing or reaffirming the NAAQS and (2) 

implementing the NAAQS. As required by the CAA, the EPA reviewed the one-hour NAAQS 

for ozone in the 1990’s and determined that a new standard was needed. This new standard was 

finalized in July of 1997. The replacement of the ozone NAAQS was pursuant to subpart 1 of 

the CAA, Title I, Part D. 

The 1997 ozone standard is based on an eight-hour averaging period. This standard defines an 

area as in attainment of the 8-hour ozone standard when the three-year average of the annual 

fourth highest daily maximum 8-hour ozone concentration is less than or equal to 0.08 parts 

ppm) (or 80 parts per billion (ppb)). Due to rounding conventions in the 1997 standard, an 8-

hour average ozone concentration above 0.085 ppm is considered an exceedance of standard. 

When the three-year average value is 0.085 ppm or greater, a violation of the ozone NAAQS has 

occurred. A violation of the eight-hour standard is determined on a per monitor basis. Monitor 

readings (and exceedances) at one location do not have any affect on the readings at another. 

The EPA was challenged in court on the new 8-hour standard, and the one-hour standard was 

reinstated. The Supreme Court upheld the constitutionality of 8-hour standard, but ruled that the 

EPA could not implement the new standard under subpart 1 of the CAA without considering the 

CAA’s subpart 2 requirements. Subpart 2 specifies area classification for nonattainment areas 

with additional control strategy requirements for each classification. The rule was remanded to 

the EPA in order to develop a reasonable approach to implement the new standard while 

considering the roles of subparts 1 and 2 in the implementation. 

Phase I of the Final Rule to Implement the 8-Hour Ozone National Ambient Air Quality 

Standard was released on April 30, 2004 and became effective on June 15, 2004. Phase II of the 

rule was published on November 29, 2005 and became effective on January 30, 2006. These two 
3 

rules provided specific obligations for state ozone plan revisions. Under these rules, the St. 

Louis 8-hour Ozone Nonattainment Area was subject to a number of obligations. All these 

obligations have been met and all required submitted revisions of the State Implementation Plan 

(SIP) for the St. Louis nonattainment area have been submitted to the EPA. 

1.2 Ozone and Its Formation 

Ozone is a reactive chemical compound. It is made up of three oxygen atoms and is identified 

by the chemical symbol O3. Ozone is a gas that occurs both in the Earth’s upper atmosphere and 

at ground level. Depending on where ozone is found, it can be good or bad. When it occurs 

naturally in the upper atmosphere, ozone acts as a shield from the sun’s harmful ultraviolet rays. 

However, ground-level ozone is a concern during the summer months when the weather 

conditions are favorable for producing ozone. 

Unlike most other pollutants, ozone is not emitted directly into the air by specific sources, but is 

formed by a photochemical reaction. This reaction occurs between NOx and VOCs in the 

presence of sunlight and elevated ambient temperatures. There are numerous sources of NOx 

and VOC pollutants. These sources are divided into four types, including point, area, mobile and 

natural. Point sources include larger permitted industries and power plants. Area sources are 

small, stationary, non-transportation sources that collectively as a group can have a significant 

contribution to air pollution. Examples of area sources include gas stations, automotive shops 

and dry cleaners. Mobile sources are divided into two categories: on-road and off-road. 

Examples of on-road mobile sources include cars, trucks and buses. Off-road sources include 

trains, ships, boats, airplanes, lawn equipment, and construction equipment. Natural sources for 

VOCs are released from vegetation, such as trees. Natural NOx sources are rare, but include 

lightning, soil and some decomposition. Ozone is most commonly an urban air issue, but high 

ozone readings can also be found in rural areas. This is due to the fact that emissions of NOx 

and VOC from motor vehicles and stationary sources can be carried hundred of miles from their 

origins, and contribute to high ozone concentrations over very large, multi-state regions. 

1.3 Negative Effects of Ozone 

Ozone is a strong oxidizing agent, with the potential to damage or impair lung airways and cause 

inflammation. Sensitive populations such as children, the elderly, and people with respiratory 

problems are the most vulnerable to its effects, but even healthy people that are active outdoors 

can be affected when the quantity of ground level ozone is high. Even relatively low amounts of 

ozone can cause chest pain, shortness of breath, and coughing. Ozone can also worsen asthma, 

bronchitis, and emphysema. Repeated exposure to ozone pollution for several months may cause 

permanent lung damage. 

Children are at a higher risk from exposure to ozone because they breathe more air per pound of 

body weight that adults do, and because children’s respiratory systems are still developing. 

Children also often spend more time out of doors during periods of high concentration than 

adults. Adults most at risk from ozone exposure are outdoor workers, people who exercise out of 

doors, and individuals suffering with respiratory diseases. 

Ground level ozone can also have negative effects on plants and other vegetation by interfering 

with their ability to produce and store food. It can also reduce agricultural productivity and 
4 

forest yields. Ozone also affects manufactured products. It causes or accelerates the 

deterioration of building materials, surface coatings, rubber, plastic products and textiles. 

1.4 Geographical Description of the St. Louis Nonattainment Area 

The St. Louis Ozone Area is a bi-state nonattainment area that violated the 1997 8-Hour Ozone 

Standard (see Figure 1-1). The following is a list of the counties contained in the St. Louis 

Missouri-Illinois 8-hour ozone nonattainment area: 

• St. Louis County, MO 

• St. Louis City, MO 

• St Charles, MO 

• Jefferson County, MO 

• Franklin County, MO 

• Madison County, IL 

• St. Clair County, IL 

• Monroe County, IL 

• Jersey County, IL 

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

the St. Louis area was 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. 
5 

Figure 1-1 1997 8-Hour Ozone Nonattainment Area for St. Louis (MO-IL) Region 
6 

1.5 St. Louis Ozone History 

 1.5.1 One Hour Ozone Standard 

The Clean Air Act Amendments of 1990 required states with nonattainment areas like St. Louis 

to develop revisions to the SIP to bring those areas into compliance. St. Louis was classified as a 

moderate ozone nonattainment area for the 1-hour standard. The Clean Air Act Amendments 

included very specific requirements for areas under each classification. The most important 

requirement for moderate areas was that attainment was to be achieved by 1996. Under the 

Amendments, failure to attain by the assigned date would result in reclassification to the more 

demanding classification of “serious.” Serious areas were subject to an additional set of 

requirements. 

St. Louis was required to achieve a minimum of 15 percent reduction in emissions of VOCs, and 

submit this Rate of Progress (ROP) plan for achieving that reduction. On November 15, 1993 the 

Missouri Department of Natural Resources’ Air Pollution Control Program submitted an initial 

ROP plan. Subsequent amendments to the ROP plan were made in 1994, 1995, and 1996. These 

amendments were the result of refinements to inventory calculations and improvements in the 

documents. 

Although the ROP requirement was one of the key obligations of the Clean Air Act 

Amendments, the primary obligation was to develop a plan to achieve the national ozone 

standard in St. Louis. This plan is referred to as an attainment demonstration. An attainment 

demonstration was prepared and submitted to the EPA on October 25, 1995, which showed that 

the area would attain the air quality standard by 1996. The St. Louis area, however, failed to 

attain the 1-Hour ozone standard by 1996. The States of Missouri and Illinois proceeded with a 

request to extend the attainment deadline. 

To qualify for an attainment deadline extension, Missouri and Illinois had to demonstrate three 

requirements: that the area was significantly affected by ozone or ozone precursors transported 

from upwind sources; that all necessary local control measures have been implemented; and that 

the states had made the necessary administrative submittals. As part of this attainment date 

extension, additional photochemical grid modeling was conducted. This modeling included a 

number of regional control measures, in addition to the 15 percent ROP controls such as 

Reformulated Gasoline (RFG) and the enhanced Vehicle Inspection/Maintenance (I/M) 

programs. The attainment demonstration submitted as part of the 1-hour extension request 

focused on the evaluation of emission reductions that were expected from electric generating 

utilities resulting from EPA’s regional NOx SIP call. This SIP call resulted from EPA’s 

determination that ozone transport from one region to another interfered with some states’ ability 

to attain their ozone air quality goals. The NOx SIP call applied to twenty-two states in the 

eastern United States, and included emission reductions from sources located in the eastern onethird of Missouri. The study showed that both regional NOx controls and local VOC controls 

were necessary for attainment of the 1-hour standard, and that St. Louis was significantly 

affected by ozone transport and emissions from other states, and therefore, qualified for the 

attainment date extension. St. Louis was granted the extension, and subsequently attained the 1-

hour ozone standard. 
7 

1.5.2 8-Hour Ozone Standard 

 1.5.2.1 8-Hour Ozone Designation 

EPA promulgated the 8-hour ozone standard in June 1997. The new standard was set 0.08 parts 

per million (ppm) averaged over 8 hours and replaced the 1-hour ozone standard. An exceedance 

of the 8-hour ozone standard occurs when a monitor measures ozone above 0.084 ppm (per the 

rounding convention). A violation of the standard occurs when the average of the annual fourth 

highest daily maximum 8-hour ozone values over three consecutive years is greater than or equal 

to 0.085 ppm. This three-year average is called the design value for the monitor. The three-year 

period from 1997-1999 were used for the purposes of designation. The design value for the St. 

Louis Area was based on the monitor in the region with the highest design value. This monitor 

is located in West Alton, MO and had a three year design value of 0.95 ppm. Areas such as St. 

Louis which had design values that ranged from 0.92 to 0.107 ppm were classified as moderate 

ozone nonattainment areas. 

Boundary designation recommendations under the 1997 standard were developed using guidance 

published by EPA on March 28, 2000 and titled “Boundary Guidance on Air Quality 

Designations for the 8-Hour Ozone National Ambient Air Quality Standards.” The boundary 

recommendation for the 8-hour standard was identical to the old 1-hour boundary. It included 

the City of St. Louis and the counties of St. Louis, Franklin, Jefferson, and St. Charles. This 

recommendation was based on an in-depth technical evaluation based on EPA guidance. The 

Department sought stakeholder input. During the workgroup process, many complex issues were 

raised and discussed. 

In July 2000, on behalf of the Governor, the Department sent the original recommendation 

regarding the classification of counties under the revised ozone standard. These 

recommendations were based on EPA guidance released on June 25, 1999 and March 28, 2000. 

Based on 1997-1999 air quality data, the Department recommended the same boundary for the 8-

hour ozone nonattainment area as was used for the previous one-hour ozone nonattainment area. 

Based on the litigation surrounding the 1997 NAAQS (discussed in section 1.1) no formal action 

was taken on the initial boundary designation submittal. EPA requested updated, revised, or new 

designation recommendations and documentation from each state governor be submitted to the 

Regional Administrator by July 15, 2003. These recommendations were to be based on 2000-

2002 quality assured air quality monitoring data. 

Based on the input from stakeholders and the technical review, the Department’s Air Pollution 

Control Program presented a proposed boundary recommendation to the Missouri Air 

Conservation Commission on June 26, 2003, and it was adopted on July 24, 2003. The 

nonattainment area boundary recommended remained unchanged from the 2000 

recommendation and the 1-hour ozone designations. The Department submitted the 

recommendation to EPA on August 2, 2003. 

In letters received December 4 and 12, 2003, the EPA stated that they intend to modify the 

boundary recommendations for eight-hour ozone nonattainment areas. The EPA intended to 

modify the recommendation to include St. Genevieve County. In response to this EPA 

comment, the Department offered an alternative, involving addressing upwind NOX emissions 
8 

rather than including all of Ste. Genevieve County. On March 25, 2004, the MACC signed a 

resolution committing the Department to promulgate a rule controlling emissions from large 

NOx sources upwind and outside of the St. Louis nonattainment area. This rule, 10 CSR 10-

6.345 Control of NOx Emissions From Upwind Sources, was subsequently promulgated and 

became effective on December 30, 2006. 

On April 15, 2004, EPA classified the St. Louis area as a moderate nonattainment area for the 

new eight-hour ozone standard. The area’s boundaries were designated as recommended and 

excluded Ste. Genevieve County. The state then had three years to develop the St. Louis 

nonattainment area 8-Hour Ozone SIP Revision. 

1.5.2.2. 8-Hour Ozone Implementation Plan 

The EPA’s 8-hour ozone implementation rule required a number of elements for an approvable 

SIP revision. These elements included: an emissions inventory; attainment demonstration; 

Reasonably Available Control Technology (RACT) requirements; a ROP demonstration; a 

demonstration that New Source Review (NSR) permitting met all EPA requirements; motor 

vehicle emissions budgets to meet both the rate of progress and attainment; a discussion of 

specific individual area controls; and identification of contingency measures in case the area was 

not able to meet its attainment deadline. 

Extensive work, effort and resources were required to develop all elements of the 

implementation plan within the time frame established by EPA. The final result of the 

evaluations and the modeling of available data showed that the St. Louis Nonattainment Area 

would attain the 1997 standard by the 2010 deadline. 

Per the implementation rule, the RACT demonstration was required to be completed prior to 

other elements of the SIP revision. It was submitted to EPA following adoption by the MACC on 

December 6, 2006. All other required elements of the revision were submitted as part of, or 

concurrent with, the 2007 revision to the SIP. The I/M portion of the SIP was resubmitted as a 

separate revision at a later date due to subsequent changes that were made in the program as the 

result of new state laws. 

A public hearing of the 8-Hour ozone nonattainment plan SIP revision was held on April 26, 

2007, before the MACC. Comments were received from the EPA and the East-West Gateway 

Council of Governments. A number of document edits were made in response to these 

comments, but no substantive changes to control strategies were needed. These revisions were 

presented on May 31, 2007, and adopted by the Commission. 

The eight-hour ozone plan was submitted to the EPA on June 13, 2007, meeting the June 15, 

2007 federal deadline. The plan showed that the St. Louis non-attainment area will attain the 

1997 NAAQS for ozone by the 2010 deadline. 

 

Attainment of the 1997 NAAQS 8-Hour Ozone Standard was achieved following the 2009 ozone 

season, allowing for the development of a request for redesignation and maintenance plan. 
9 

1.6 Current Status / Background Summary 

On June 9, 2011, EPA published a final clean data determination in the Federal Register stating 

that the St. Louis ozone nonattainment area covering both Missouri and Illinois has attained the 

1997 8-hour ozone standard based on three consecutive ozone seasons of quality assured ambient 

air monitoring data (76 FR 33647, June 9, 2011). Information regarding the air monitoring 

network and air quality monitoring data are included in Section 3.0 of this document. 

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. Clean air quality data is one of those 

requirements. 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. The development of a maintenance plan is another. This document 

addresses the maintenance plan requirements, and includes additional information on the 

permanent and enforceable measures used to demonstrate attainment and continued compliance 

with the 1997 8-hour ozone NAAQS. 
10 

2. Redesignation and Maintenance Plan Requirements 

An area designated as nonattainment for a pollutant can be redesignated to attainment if specific 

conditions are met. Missouri has followed the EPA published Memorandum entitled, 

“Procedures for Requests to Redesignate Areas to Attainment”, from John Calgani, Director, Air 

Quality Management Division, dated September 4, 1992, in preparing the redesignation 

demonstration and the maintenance plan. The memorandum provides guidance regarding the 

processing of requests for redesignation of nonattainment areas to attainment for ozone, carbon 

monoxide, particulate matter, sulfur dioxide, nitrogen dioxide, and lead. 

 Furthermore, the CAA, lists five (5) obligations that the EPA must meet during the 

redesignation process. Section 107(d)(3)(E) states: 

The Administrator may not promulgate a redesignation of a nonattainment area (or portion thereof) to 

attainment unless – 

(i) the Administrator determines that the area has attained the national ambient air quality standard;

(ii) the Administrator has fully approved the applicable implementation plan for the area under section 

110(k); 

(iii) the Administrator determines that the improvement in air quality is due to permanent and enforceable 

reductions in emissions resulting from implementation of the applicable implementation plan and 

applicable Federal air pollutant control regulations and other permanent and enforceable reductions; 

(iv) the Administrator has fully approved a maintenance plan for the area as meeting the requirements of 

section 175A; and 

(v) the State containing such area has met all requirements applicable to the area under section 110 and part 

D. 

These five (5) obligations must be met before redesignation to attainment status; however, a state 

may submit both the redesignation request and the maintenance plan at the same time so that 

rulemaking on both may proceed on a parallel track. This document outlines Missouri’s 

redesignation request and demonstrates how the state supports EPA’s promulgation obligations 

towards the redesignation of the St. Louis nonattainment area to attainment under the 1997 ozone 

NAAQS. 

2.1 Attainment of the Standard 

Requirement (i) for redesignation states that EPA must determine that the area is attaining the 

applicable NAAQS. For the 1997 8-hour ozone NAAQS, this determination must be 

demonstrated using the design value based on the average of the last three (3) years’ 4th highest 

maximum daily 8-hour average concentrations. This design value must be lower than the level 

of the NAAQS, 0.08 ppm. The state submitted a Clean Data Request to the EPA on December 4, 

2009. On June 9, 2011, EPA published a final clean data determination in the Federal Register 

stating that the St. Louis ozone nonattainment area covering both Missouri and Illinois has 

attained the 1997 8-hour ozone standard based on three years of quality assured ambient air 

monitoring data (76 FR 33647, June 9, 2011). Section 3 presents information that demonstrates 

the St. Louis nonattainment area has attained the 1997 8-hour ozone NAAQS. This 

demonstration is based on three consecutive ozone seasons of quality assured monitoring data as 

specified in 40 CFR 58. 
11 

2.2 Implementation Plan Approval 

Requirement (ii) for redesignation states that the EPA administrator must have fully approved 

the applicable implementation plan for the area under section 110(k) of the CAA. The 2007 

Revision of the State Implementation Plan for the St. Louis 8-HOUR Ozone Nonattainment Area

was proposed for public hearing on April 26, 2007; was adopted by the Missouri Air 

Conservation Commission (MACC) on May 31, 2007 and was submitted to the EPA on June 13, 

2007. This ozone SIP was deemed to be complete on December 21, 2007. 

As stated earlier, EPA has published a final rule in the Federal Register stating that the St. Louis 

ozone nonattainment area covering both Missouri and Illinois has attained the 1997 8-hour ozone 

standard based on three years of quality assured ambient air quality data (76 FR 33647, June 9, 

2011). Once an area attains the standard for a criteria pollutant, certain SIP element 

requirements that are developed to demonstrate and achieve attainment become unnecessary 

because the area has already attained the standard. These SIP elements that are tied to 

demonstration of attainment are no longer required as long as the area does not violate the 

standard again. These particular SIP elements would never be required once the area is 

redesignated to a maintenance area for the pollutant. Guidance on this subject is found on page 6 

of the EPA’s Memorandum, Procedures for Requests to Redesignate Areas to Attainment, from 

John Calgani, Director, Air Quality Management Division, dated September 4, 1992 which states 

“requirements for reasonable further progress ... will not apply for redesignations because they 

only have meaning for areas not attaining the standard.” 

This guidance is reaffirmed in EPA’s May 10, 1995 Memorandum from John S. Seitz, Director, 

Office of Air Quality Planning and Standards, titled Reasonable Further Progress, Attainment 

Demonstration, and Related Requirements of Ozone Nonattainment Areas Meeting the Ozone 

National Ambient Air Quality Standard. Page 6 of the 1995 Seitz memo details that suspensions 

are only valid while the area is in compliance with the standard and how the suspended 

requirements are relieved: 

Thus, a determination that an area need not submit one of the SIP submittals amounts to 

no more than a suspension of the requirement for so long as the area continues to attain 

the standard. If EPA ultimately redesignates the area to attainment, then the area will be 

entirely relieved of these requirements to the extent the maintenance plan for the area 

does not rely on them.

As such, on June 21, 2011, the state withdrew the above mentioned 8-hour Ozone Attainment 

Demonstration and Reasonable Further Progress Demonstration, because the area has already 

attained the NAAQS. All controls and regulations that are included in Missouri’s approved SIP 

will continue to remain in place to ensure that the air quality improvements that have resulted 

from these controls remain permanent and enforceable. By withdrawing the attainment 

demonstration, the EPA administrator will no longer be required to approve or disapprove this 

plan. The attainment demonstration is no longer applicable because the area has attained the 

standard and therefore, only SIP elements that include permanent and enforceable control 

measures, such as regulations and consent agreements need to be approved in order to satisfy this 

requirement for redesignation. Missouri has adopted all other necessary provisions to ensure the 

protection of the standard including the Prevention of Significant Deterioration Program (PSD), 
12 

under State rule 10 CSR 10-6.060, Construction Permits Required. Additional information about 

the control measures used to attain the 1997 8-hour ozone standard can be found in Section 4 of 

this document. 

2.3 Permanent and Enforceable Improvement 

Requirement (iii) for redesignation states that EPA must determine that the improvement in air 

quality is due to permanent and enforceable reductions in emissions resulting from 

implementation of the applicable implementation plan and applicable Federal air pollutant 

control regulations and other permanent and enforceable reductions. Therefore, EPA must show 

that the improvement in air quality between the year violations occurred and the attainment year 

is attributed to permanent and enforceable emission reductions. Section 4 of this document 

presents the emission reductions that were achieved from federal and state measures in the St. 

Louis area. The emission reductions are not based on temporary shutdowns or adverse economic 

conditions, but due to permanent and enforceable control measures. This maintenance plan and 

redesignation request includes a state commitment to continue to enforce all applicable 

requirements of past revisions to the SIP after the St. Louis ozone nonattainment area is 

redesignated to attainment. 

2.4 Maintenance Plan Requirements 

Requirement (iv) for redesignation states that EPA must have fully approved a maintenance plan 

for the area as meeting the requirements of section 175A of the Clean Air Act. Under Section 

175A of the Clean Air Act, this 8-Hour Ozone Maintenance Plan is the state’s SIP revision to 

provide for continued attainment of the 1997 8-hour ozone NAAQS for the St. Louis 

nonattainment area for a period of at least ten years after EPA has formally redesignated the area 

to attainment. To be approvable, the state is required to have 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”; 

• 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 ten-year 

maintenance period; 
13 

• 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 and redesignation request has been prepared in accordance with the 

requirements specified in U.S. EPA’s guidance document and additional guidance received from 

EPA staff. The following subsections of this document describe how these requirements have 

been met. 

2.4.1 Public Participation 

In accordance with Section 110(a)(2) of the CAA, the Missouri is required to hold a public 

hearing prior to adoption of this maintenance plan and the subsequent submittal to the EPA. The 

Department will notify the public and other interested parties of an upcoming public hearing and 

comment period thirty (30) days prior to holding such hearing for this maintenance plan as 

follows: 

• Notice of availability of the redesignation request and maintenance plan was posted on 

the Department of Natural Resources’ Air Pollution Control Program website on August 

26, 2011: http://www.dnr.mo.gov/env/apcp/stateplanrevisions.htm

• The public hearing date to receive comments on the redesignation request and 

maintenance plan is to be held on September 29, 2011, beginning at 9:00 am at the 

Holiday Inn Southeast, Grand Ballroom A, B and C, 9103 East 39th Street, Kansas City, 

MO 64133. 

• A public comment period was open after the redesignation request and maintenance plan 

was posted on Department of Natural Resources’ Air Pollution Control Program website 

on August 26, 2011, and closes on October 6, 2011, seven (7) days after the public 

hearing. 

• Notice of availability of the 2008 St. Louis Ozone Nonattainment Area Base Year 

Inventory was posted on the Department of Natural Resources’ Air Pollution Control 

Program website by August 9, 2011: 

http://www.dnr.mo.gov/env/apcp/stateplanrevisions.htm

• A public comment period was open after the 2008 St. Louis Ozone Nonattainment Area 

Base Year Inventory was posted on the Department of Natural Resources’ Air Pollution 

Control Program website by August 8, 2011, and allowed for a public hearing to be held 

in regards to the document if requested. The public comment period for this inventory 

closes on September 7, 2011. 

• No public hearing was requested for the 2008 St. Louis Ozone Nonattainment Area Base 

Year Inventory 
14 

2.4.2 Comprehensive “Attainment Year” Emissions Inventory of Ozone Precursors 

The state has developed a comprehensive emission inventory for the St. Louis ozone 

nonattainment area which includes the emissions from the following four source categories: 

point sources, area sources, on-road mobile sources and off-road mobile sources. The attainment 

year emission inventory, as required in the maintenance plan, is detailed in Section 5 of this 

document. 

2.4.3 Projected Emission Inventory for 2022 

The state has compiled a list of growth and control factors and developed a county level emission 

inventory for the future year of 2022 for the Missouri portion of the St. Louis nonattainment 

area. These projected emissions show substantial decreases between 2008 and 2022 in 

cumulative emissions that contribute to ground-level ozone concentrations in the ambient air. 

This future year emission inventory is detailed in Section 5 of this document and the state asserts 

that these projected future emission levels are sufficient to maintain attainment of the 1997 8-

hour ozone NAAQS. 

2.4.4 Continued Monitoring Commitment 

The State of Missouri is committed to continue monitoring ground-level ozone concentrations in 

the St. Louis area and throughout the state in accordance with 40 CFR Part 58 and EPA approved 

Annual Monitoring Plans. Missouri will continue to quality assure the ambient air monitoring 

data in accordance with 40 CFR 58 and submit the data into the AQS in a timely fashion. 

Detailed information about the ground-level ozone monitoring network in the St. Louis 

nonattainment area, along with further discussion about the state’s continued monitoring 

commitment, can be found in Section 3 of this document. 

2.4.5 Legal Authority to Implement and Enforce 

The Missouri Air Conservation Commission has the legal authority to develop, implement, and 

enforce regulations regarding air pollution including the requirements of this SIP submittal under 

section 643.050 of the Revised Statues of Missouri, also known as the Missouri Air Conservation 

Law. 

2.4.6 Provisions for Future Updates to the Emission Inventory 

The State of Missouri is committed to provide future updates of the inventory to enable tracking 

of emissions levels during the 10-year maintenance period. State Regulation 10 CSR 10-6.110, 

Reporting Emissions Data, Emission Fees, and Process Information, requires that all 

installations located in the state that are required to obtain air quality construction or operating 

permits must report their annual emissions to the department. The methods for calculating and 

reporting their emissions are detailed in each installation’s applicable permit. The data collected 

on emissions inventory questionnaires from permitted sources form the basis of the point source 

emissions inventory that is compiled on an annual basis. In addition, in compliance with the 
15 

Federal Air Emission Reporting Rule (73 FR 76539), the Air program develops a comprehensive 

emissions inventory of point, area, and mobile sources every three years. 

2.4.7 Motor Vehicle Emission Budgets 

The State of Missouri is has developed motor vehicle emissions budgets that will be used in 

Transportation Conformity Determinations in the St. Louis area through 2022. Section 6 of this 

document details the Transportation Conformity Process in the St. Louis area and specifies the 

2022 motor vehicle emissions budgets for NOX and VOC emissions. 

2.4.8 Commitment to Revise Plan 

Under Section 175A of the Clean Air Act, an area designated as maintenance for a NAAQS is 

required to submit a second maintenance plan eight (8) years after redesignation of any area as 

an attainment area under Section 107(d). This second maintenance plan is intended to maintain 

the NAAQS for ten (10) years after the expiration of the initial ten year period. The 

Department’s Air Pollution Control Program recognizes the importance of an up-to-date, current 

maintenance plan, and commits to updating it as necessary. 

2.4.9 Contingency Measures 

The State of Missouri is committed to maintaining compliance with the 1997 8-hour ozone 

standard. If future violations of the standard take place, the state will enact contingency 

measures as expeditiously as possible, that will allow for the area to come back in compliance 

with the standard as quickly as feasible. Further information about this commitment to enact 

contingency measures, and a potential list of contingency measures that would be evaluated if 

the area falls out of compliance with this standard in the future are located in Section 7 of this 

document. 

2.5 Section 110 and Part D Requirements 

Requirement (v) for redesignation states that, all the requirements of the section 110 and part D 

of the CAA that were applicable prior to submittal of a complete redesignation request must be 

met. These requirements include an emissions inventory for a representative base year. 

However, certain requirements are suspended when a nonattainment area achieves the NAAQS 

because these requirements are correlated to the attainment of the air quality goal and thus the 

intention of these requirements has been fulfilled with achievement of the NAAQS without the 

necessity of further submittals as long as the area does not violate the standard again. The 

requirements for reasonable further progress that are needed for attainment are suspended for 

redesignation requests as long as an area is in attainment. Guidance on this subject is found on 

page 6 of the EPA’s Memorandum, Procedures for Requests to Redesignate Areas to Attainment, 

from John Calgani, Director, Air Quality Management Division, dated September 4, 1992 which 

states “requirements for reasonable further progress ... will not apply for redesignations because 

they only have meaning for areas not attaining the standard.” Applicable section 110 and Part D 

requirements that specifically apply to the maintenance plan are addressed in this document. 
16 

3. OZONE MONITORING 

This section presents monitoring information that demonstrates St. Louis has attained the 1997 8-

hour ozone standard of 0.08 ppm. This demonstration is based on three consecutive ozone 

seasons of quality assured data monitored at the St. Louis ozone monitoring network as specified 

in 40 CFR 58. The demonstration uses ambient air quality monitoring data to demonstrate that 

the area is attaining the applicable NAAQS consistent with methods cited in the EPA guidance 

document “Procedures for Processing Request to Redesignate Areas to Attainment”. The 

following are requirements regarding the use of ambient air monitoring data in demonstrating 

that the area is attaining the applicable NAAQS, as one of the conditions: 

• Monitoring data must show that the non-attainment area is attaining the NAAQS. 

• The data should be collected and quality assured in accordance with 40 CFR 58 and 

recorded in the U.S. EPA Air Quality System (AQS) database in order for it to be 

available to the public for review. 

3.1 St. Louis Ozone Monitoring Network 

There are currently 15 sites that monitor ozone in the St. Louis Region. 11 sites are located 

within the St. Louis nonattainment area; 6 in Missouri and 5 in Illinois. In addition, Missouri and 

Illinois operate at least a monitor upwind and downwind of the nonattainment area. The upwind 

monitors are located in Bonne Terre, Ste. Genevieve County, Missouri and in Hickory, Randolph 

County, Illinois. Downwind monitors outside of the nonattainment area are located in Foley, 

Lincoln County, Missouri and Nilwood, Macoupin County, Illinois. Figure 3-1 shows all 

monitors in the St. Louis Ozone Monitoring Network.
17 

Figure 3-1 St. Louis Ozone Monitoring Network 

3.2 Ambient Air Monitoring Data 

As previously mentioned, exceedances of the standard are determined on a per monitor basis. 

An exceedance of the standard occurs any time that an 8-hour average value is greater than 0.084 

ppm. A monitor can exceed the 8-hour standard and not violate the standard. A violation of the 

standard at a specific monitor is determined by taking the fourth-highest, eight-hour average 

reading at a monitor for each of three consecutive years and averaging them together. The eighthour ozone standard is 0.08 ppm and, due to rounding, a monitor must have a fourth highest 

eight-hour, three-year average reading of 0.085 ppm (85 parts per billion, or ppb) or higher for it 

to be considered a violation of the standard. 

Design values are calculated by averaging the annual fourth-highest daily maximum 8-hour 

ozone concentrations over the three consecutive years (40 CFR Part 50). The standard at a site is 

met when the site’s design value is less than or equal to 0.084 ppm (84 ppb). Design values are 

used as indicators of a region’s air quality. The higher a design value for a monitor, the poorer 

the air quality is in that area. Along the same lines, if an area shows an increasing design value 

over a number of years, monitoring data is indicating that the air quality is worsening. 
18 

Figures 3-2 and 3-3 show the design value trends for the monitors in the Missouri portion of the 

St. Louis nonattainment area and the Illinois portion of the St. Louis nonattainment area, 

respectively. As indicated by the trends in the figures, ozone concentrations have decreased at all 

monitors, indicating improved air quality throughout the St. Louis region. Within the Missouri 

portion of the St. Louis nonattainment area, there were a total of 11 sites that violated the 1997 

standard according to 2001-2003 air monitoring data (Figure 3-2). During the same time period 

of 2001-2003, two sites in the Illinois portion of the St. Louis nonattainment area also violated 

the 1997 standard (Figure 3-3). All sites in the area, are now in compliance of the standard, as 

shown by the design value data in Figures 3-2 and 3-3, as well as the comparison maps in Figure 

3-4. Sites that have been discontinued or relocated show design values below the standard at the 

time of discontinuance or relocation (Figures 3-2 and 3-3). 
19 

Figure 3-2 2001-2010 8-hour Ozone Design Value Trends - MO 

St. Louis Nonattainment Area, MO (1997 NAAQS = 84 ppb) 
20 

Figure 3-3 2001-2010 8-hour Ozone Design Value Trends - IL 

St. Louis Nonattainment Area, IL (1997 NAAQS = 84 ppb) 
21 

Figure 3-4 2001-2003 & 2008-2010 Design Values Comparison 

St. Louis Nonattainment Area 8-hour Ozone Design Values (1997 NAAQS = 84 ppb) 

2001-2003 Design Values 

2008-2010 Design Values 
22 

3.3 St. Louis Ozone Monitoring Data Analysis 

The St. Louis area’s compliance with the 1997 ozone NAAQS is determined by comparing the 

area’s calculated design values to the ozone standard. As described previously, design values are 

calculated at each monitor by averaging the annual fourth-highest daily maximum 8-hour ozone 

concentrations over the three consecutive years (40 CFR Part 50). The standard at a site is met 

when the site’s design value is less than or equal to 84 ppb. 

The design value for the entire St. Louis nonattainment area is determined by comparing all of 

the design values for the monitors in the nonattainment area. The area’s design value is 

determined by the single highest individual monitor’s design value for each three consecutive 

ozone season averaging period. The area’s status of attainment or nonattainment is determined 

by this design value. For the eight-hour ozone standard, the design value at all monitors for the 

three-year time periods from 2008 through 2010 do not exceed 0.084 ppm, and thus achieve 

attainment for the St. Louis nonattainment area. The calculated 2008-2010 8-hour design values 

for sites in the St. Louis nonattainment area are presented in Table 3-1. As shown in the table, all 

sites three year design values are less than the 1997 standard, demonstrating that the St. Louis 

area has attained the 8-hour air quality standard. The St. Louis nonattainment area’s design 

value monitor would be the West Alton monitor, due to its design value being the highest. The 

West Alton monitor is bold in Table 3-1. 

Table 3-1 2007-2009 St. Louis 8-Hour Design Values 

(1997 NAAQS = 84 ppb) 

County Monitoring Sites 

2008 

4

th

High 

2009 

4

th

High 

2010 

4

th

High 

2008-2010 

Design Value 

 Missouri 

St. Charles Orchard Farm 72 73 77 74 

St. Charles West Alton 76 71 84 77 

St. Louis City Blair Street 73 65 71 69 

St. Louis Maryland Heights 69 70 76 71 

St. Louis Pacific 64 64 69 65 

Jefferson Arnold West 70 70 77 72 

3.4 Missing Data Under the 1997 8-Hour Ozone Standard 

Eight-hour ozone attainment is determined by a three-year average of the annual fourth highest 

daily maximum. Missing days are of importance only in determining whether sufficient data 

was sampled to determine compliance. A monitoring day must include 18 valid eight-hour 

averages for a daily maximum to be determined. To calculate a design value, an average of 90% 

of the possible daily maximums over a three year period must be complete, with no single year 

having less than 75% completeness. The final result is that no more than 53 missed days in one 

year, or 64 missed days total for the three-year period are allowed. If these criteria are not met, 

then compliance with the 8-hour ozone standard cannot be established. To date, acceptable 
23 

monitoring has been maintained and exceeded in the Missouri portion of the St. Louis 

nonattainment area for the 8-hour ozone standard. 

3.5 Quality Assurance Program 

Ambient air monitoring data from the Missouri ozone network is quality assured in accordance 

with 40 CRF Part 58 and the Missouri Quality Assurance Project Plan (QAPP). The QAPP 

outlines standard operating procedures for operating the network and validating the data. In 

addition the network is reviewed annually through the Annual Monitoring Plans, according to 40 

CFR Part 58.10. A site can either be discontinued or relocated based on the annual review and 

with an approval from the EPA. The quality assured data collected at the sites is submitted in the 

Air Quality System (AQS) and is available for public review as outlined in 40 CFR Part 58. 

Illinois EPA follows a similar quality assurance system. 

3.6 Continued Monitoring Commitment 

The State of Missouri is committed to continue operating the appropriate ozone network in the 

St. Louis area, in accordance with 40 CFR 58 and approved Annual Monitoring Plans, to verify 

the attainment status of the area. Missouri will continue to quality assure the ambient air 

monitoring data in accordance with 40 CFR 58 and submit the data to AQS in timely fashion. 

The St. Louis Metropolitan Statistical Area (MSA) satisfies and exceeds the minimum 

monitoring requirement for ozone (40 CFR 58 Appendix D, Table 2), revisions to the Ambient 

Air Monitoring Regulations (71 Federal Register 61240, October 17, 2006) note “While the final 

rule of regulations requires fewer monitors than are now operating for ozone and PM2.5, as did 

the pre-existing monitoring rule, EPA does not intend to encourage net reductions in the number 

of ozone and PM2.5 monitoring sites in the U.S. as a whole. The surplus in the existing networks 

relative to minimum requirements gives States more flexibility to choose where to apply 

monitoring resources for ozone and PM2.5”. The State of Missouri commitment is to continue

working with the EPA to ensure that the ozone monitoring network is sufficiently meeting the 

monitoring requirement of 40 CFR 58 and its monitoring objectives. 

3.7 Clean Data Determination 

On June 9, 2011, EPA published a final clean data determination in the Federal Register stating 

that the St. Louis ozone nonattainment area covering both Missouri and Illinois has attained the 

1997 8-hour ozone standard based on three years of quality assured ambient air monitoring data 

(76 FR 33647, June 9, 2011). 
24 

4. Redesignation Request: Emission Inventory and Controls from 

2002 - 2008 

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, three 

consecutive ozone season monitoring periods are used to evaluate whether actual air quality 

attainment has been achieved. In this section, the “attainment year” refers to the first year (2008) 

of the three-year period (2008-2010) used to demonstrate attainment, and the base year refers to 

the mid-point year (2002) of the three year period used to determine the designation of the 

nonattainment area. The inventories detailed in this section for 2002 and 2008 include data 

categories for point, area, and mobile emissions for NOX and VOC. Additional details for the 

base and attainment year inventories for 2002 and 2008 are found in Appendices A and B, 

respectively. 

4.1 Base Year and Attainment Year Inventories 

Table 4.1 is a comprehensive emissions inventory for the Missouri side of the St. Louis 

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

precursors of ground-level ozone (NOX and VOC) for the base year, 2002. Table 4.2 is a 

comprehensive emissions inventory for the Missouri side of the St. Louis nonattainment area for 

NOX, and VOC for the attainment year, 2008. Both the 2002 and 2008 inventories are based on 

actual activity levels. 

The emissions inventories listed in this section are listed in tons/ozone season day. In order to 

calculate the emissions in tons/ozone season day for the Missouri portion of the ozone 

nonattainment area, the Air Program followed the methods listed in Appendix E of this 

document. Briefly, for point sources ozone season day emissions are calculated on the EIQ form 

2.0Z, Ozone Season Information. The facility reported maximum daily throughput during the 

ozone season is multiplied by the pollutant emission factor and reduced by control device to 

reach the ozone season daily emissions. For area sources, ozone season day emissions were 

calculated from (Emissions Modeling Clearinghouse) EMCH temporal allocation profiles that 

are SCC-specific. Ozone season day emissions are typical of a Tuesday in July. See Appendix E7 for the temporal allocation method and calculation tables. Appendix E-7 outlines this 

procedure for area sources, and gives an example. Off-Road ozone season day emissions were 

calculated by EPA Region 7, and additional information can be found in Appendix E-4. Finally, 

for on-road mobile sources, emissions were calculated using mobile emission models for the 

months of April-October, and then divided by 214 (the number of days in the ozone season) to 

get the average ozone season day emissions. 

The 2002 base year inventory includes emissions from point, area, on-road mobile and off-road 

mobile emissions. Table 4.2 states the 2002 emissions in tons/ozone season day, and 

summarizes the emissions by major source category and by pollutant for the St. Louis 

nonattainment area. On May 31, 2007, EPA approved Missouri’s 2002 Base Year Inventory for 

the Missouri Portion of the 1997 St. Louis Ozone Nonattainment area. Some minor corrections 

have been made to this inventory since EPA approved it in 2007. The revised 2002 base year 
25 

inventory was adopted by the Missouri Air Conservation Commission on May 31, 2007 and 

submitted to EPA on June 13, 2007. This revised inventory, which details all of the changes 

from the original 2002 base year inventory, is now being resubmitted to EPA along with this 

redesignation request and maintenance plan. Summary tables of the 2002 anthropogenic 

emissions inventory for the St. Louis ozone nonattainment area may be found in Appendix A. 

For the 2008 “attainment year” emissions inventory, the documentation of the development of 

the emissions inventories for point, area, and off-road mobile categories are described in detail in 

Appendix E, and also summarized in Appendix B. Point source emissions for the pollutants of 

concern were compiled from Missouri’s Air Emissions Database. 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. Offroad mobile source emissions were developed by EPA Region VII staff, who utilized the 

NONROAD 2008a model in order to estimate the off-road mobile source emissions for an ozone 

season day. Biogenic emissions were not included in these summaries. 

For Section 4 of this document, the 2008 mobile emissions were created using Mobile6.2 via the 

National Mobile Inventory Model (NMIM) with 2008 vehicle miles traveled (VMT) data 

provided by the East West Gateway Council of Governments in coordination with the 

Interagency Council of Governments. The 2008 VMT data was generated from East-West 

Gateway's Traffic Demand Model and then compared to Highway Performance Monitoring 

System (HPMS) data. Through this comparison, calibration factors were developed and then 

applied to the VMT data from the Traffic Demand Model in order to estimate the actual 2008 

VMT for the St. Louis nonattainment area. The NMIM National County Database (NCD) was 

updated with Missouri specific data. Please see Appendix B-2 for additional details regarding 

the 2008 on-road mobile emissions calculated using Mobile 6.2 via NMIM. 

The EPA’s Mobile6.2 emissions model was used to generate the mobile source emissions in this 

section in order to allow for a useful comparison between 2002 and 2008 mobile emissions. The 

mobile emissions generated for the 2002 emissions inventory used Mobile6.2, and it was 

necessary to use the same mobile emission model to compare the base and attainment year 

mobile source emissions. However, in Section 5 of this document, the 2008 and 2022 mobile 

source emissions were generated using EPA’s Motor Vehicle Emissions Simulator (MOVES) 

2010a. More information about the use of these two different emission models can be found in 

Section 5 and Appendix B of this document. 

Tables 4-1 and 4-2 summarize the 2002 and 2008 average daily ozone season NOX and VOC 

emissions from the Missouri side of the St. Louis ozone nonattainment area, respectively. Table 

4.3 shows the differences in inventories between these two years for each source category and 

pollutant of concern. As seen in Table 4-3, emissions of NOX emissions decreased by 138 tons 

per ozone season day, while VOC emissions remained relatively stable. The substantial 

reduction in NOX emissions between 2002 and 2008, along with other regional controls have 

resulted in the improved monitored ground-level ozone concentrations in the St. Louis 

nonattainment area. 
26 

Table 4-1. 2002 VOC and NOX Emissions for the Missouri Side of the 1997 St. Louis 

8-Hour Ozone Nonattainment Area (tons per ozone season day) 

Source Category NOX VOC 

Point Sources 127.2 32.7 

Area Sources 19.4 71.3 

On-Road Mobile Sources 159.0 68.1 

Off-Road Mobile Sources 60.7 47.0 

Total 366.3 219.1 

Table 4-2. 2008 VOC and NOX Emissions for the Missouri Side of the 1997 St. Louis 

8-Hour Ozone Nonattainment Area (tons per ozone season day) 

Source Category NOX VOC 

Point Sources 88.8 18.0 

Area Sources 6.5 98.7 

On-Road Mobile Sources 96.2 57.9 

Off-Road Mobile Sources 60.9 46.4 

Total 252.4 221.0 

Table 4-3. Comparing 2002 and 2008 VOC and NOX Emissions for the Missouri Side of the 

1997 St. Louis 8-Hour Ozone Nonattainment Area (tons per ozone season day) 

Source Category NOX VOC 

Point Sources* - 38.4 - 14.7 

Area Sources* - 12.9 + 27.4 

On-Road Mobile Sources* - 62.8 - 10.2 

Off-Road Mobile Sources* +0.2 - 0.6 

Total* - 113.9 + 1.9 

*Note: A negative value indicates a decrease in emissions from 2002 to 2008. 

A positive value indicates an increase in emissions from 2002 to 2008.

4.2 Controls Used to Attain the Standard 

The St. Louis area was designated as nonattainment of the 1997 8-hour ozone NAAQS in 2004. 

Since that time, the implementation of permanent and enforceable reductions of NOX and VOC 

emissions have contributed to improvements in ground level ozone concentrations and to the 

attainment of the 1997 8-hour ozone NAAQS. The primary control measures used to attain the 

1997 8-hour ozone standard include: 

• New Source Performance Standards (NSPS) 

• National Emissions Standards for Hazardous Air Pollutants (NESHAPS)/Maximum 

Achievable Control Technology (MACT) Standards 

• Federal gasoline detergent additive rule 

• NOX SIP Call 

• Clean Air Interstate Rule (CAIR) 

• Heavy-Duty Diesel Engine Standards 
27 

• Tier 2 Rule-Vehicle Standards 

• Tier 4 Rule-Off Road Mobile Engine Standards 

• Reformulated Gasoline (RFG) 

• Gateway Vehicle Inspection Program 

• National VOC Emission Standards for Consumer and Commercial Products (Part 59) 

o Automobile Refinishing Rule 

o Architectural and Industrial maintenance coating rule 

o Consumer Products solvent control rule 

• Missouri State Rules (see Subsection 4.2.3) 

4.2.1 Federal Emission Trading Programs 

The NOX SIP Call and CAIR are federal emission trading programs that were designed to reduce 

the transport of emissions that have significant impacts on downwind nonattainment and 

maintenance areas. The first year in which sources were required to comply with the NOX SIP 

Call was 2003. In Missouri, the NOX SIP Call only affected the eastern third of the state. The 

NOX SIP Call greatly reduced ozone season NOX emissions from large sources such as EGUs. 

According to data from CAMD’s Website, the total ozone season NOX emissions from EGUs 

located in the St. Louis nonattainment area have reduced by 4,942 tons (approx. 32.3 tons/ozone 

season day) from 2002 to 2008. These reductions are almost exclusively attributed to the NOX

SIP Call. Additionally, the NOX SIP Call limited NOX emissions from non-EGU boilers 

including those located at Anheuser Busch and Trigen Ashley Street Station. From 2002 to 

2008, the NOX emission reductions from all point sources in the nonattainment area totaled 38.4 

tons /ozone season day. 

CAIR replaced the NOX SIP Call and first became effective in 2009. CAIR limited the amount 

of annual and ozone season NOX emissions from EGUs in the entire state of Missouri. In 

regards to the EGUs located in the St. Louis nonattainment area, the requirements in CAIR were 

no more stringent than the requirements under the NOX SIP Call other than the fact that the 

annual NOX emissions had to be controlled in addition to ozone season NOX emissions. 

However, CAIR had a significant impact on the EGUs located in the western two-thirds of the 

state, who were now required to significantly reduce their annual and ozone season NOX

emissions. Some of the facilities in the western two-thirds of the state installed controls earlier 

than 2009 in anticipation of CAIR. While the NOX controls added in the western two-thirds of 

the state do not affect the NOX emissions inventory for the St. Louis nonattainment area, they did 

have a positive impact in reducing the regional contribution of NOX emissions to the ozone 

monitors located in the nonattainment area. 

4.2.2 Federal Mobile Source Emission Controls

Federal and state regulations for mobile sources have been phased in since 2002 have had a 

positive impact on the emissions inventory in all three pollutant categories for both on-road and 

off-road mobile sources. Mobile source regulations including Heavy-Duty Diesel Engine 

Standards and Low-Sulfur Diesel, Tier 2 Rule-Vehicle Standards, Tier 4 Rule-Off Road Mobile 

Engine Standards, Reformulated Gasoline (RFG), and the Gateway Vehicle Inspection Program 
28 

have reduced the NOX and VOC emissions from the mobile sector in the St. Louis nonattainment 

area. 

Overall, the retirement of older higher polluting vehicles and the phasing in of federal on-road 

mobile source standards from 2002 to 2008 have contributed to a decrease of 62.8 tons/ozone 

season day of direct NOX emissions, and 10.2 tons/ozone season day of VOC emissions. These 

on-road mobile source emission reductions have significantly contributed to attainment of the 

1997 8-hour ozone NAAQS in the St. Louis area. 

4.2.3 State Regulations 

Several new state regulations that have been adopted since 2002 have resulted in reductions in 

both NOX and VOC emissions. These include the restriction of heavy duty diesel engine idling, 

the Gateway Vehicle Inspection Program, and the control of NOX emissions from cement kilns 

and stationary internal combustion engines. The Federal NOX SIP Call Rule and the associated 

emission reductions are discussed in detail in Subsection 4.2.1. State Regulation 10 CSR 10-

6.360 was the rule written to address the NOX SIP Call requirements, which has had a significant

effect on ozone season NOX emissions from EGUs in the nonattainment area. State Regulation 

10 CSR 10-6.350 is the statewide NOX rule, which limited emissions of NOX both inside the St. 

Louis nonattainment area along with the rest of the state. State Regulation 10 CSR 10-6.364 was 

written to comply with the ozone season NOX portion of CAIR. Implementation of the seasonal 

NOX portion of CAIR began in 2009 and replaced both the NOX SIP call and the statewide NOX

rule. These six rules are listed below along with the dates they became effective. 

10 CSR 10-5.381 On-Board Diagnostics Motor Vehicle Emissions Inspection, 

Original Effective Date: 8/30/07, 

10 CSR 10-6.350 Emission Limitations and Emissions Trading of Oxides of Nitrogen, 

Original Effective Date: 9/30/00, Compliance Date: 5/1/04, 

10 CSR 10-6.360 Controlling NOX Emissions From Electric Generating Units and Non-Electric 

Generating Boilers, 

Original Effective Date: 10/30/05, 

10 CSR 10-6.364 Clean Air Interstate Rule Seasonal NOX Trading program, 

Original Effective Date: 5/30/07, 

10 CSR 10-6.380 Control of NOX Emissions From Portland Cement Kilns, 

Original Effective Date: 10/30/05, and 

10 CSR 10-6.390 Control of NOX Emissions From Large Stationary Internal Combustion 

Engines 

Original Effective Date: 10/30/05 
29 

4.3 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 nonattainment areas. The 

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 nonattainment areas is defined as 100 tons per year (tpy) of 

NOx or VOCs. 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. 

On April 20, 2011, the Air Program requested an exemption for sources of nitrogen oxides (NOx) 

in the Missouri portion of the St. Louis metropolitan 8-hour ozone nonattainment area from the 

Clean Air Act (CAA) for NOx Reasonably Available Control Technology (RACT) for purposes 

of attaining the 1997 8-hour ozone National Ambient Air Quality Standard (NAAQS). The 

waiver demonstrates that additional reductions of NOx emissions in the area would not contribute 

to attainment of the 1997 8-hour ozone (NAAQS). EPA published this exemption as a direct 

final rule and received no comments on this rule (76 FR 43598). The rule became effective 

September 19, 2011. This NOX waiver alleviates the requirements for a demonstration that NOX

RACT obligations have been met. Therefore, only VOC RACT demonstration requirements will 

be necessary for redesignation. 

 

Also 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) documents that are 

promulgated by the EPA. The EPA has issued CTGs defining presumptive RACT for those 

categories of sources that emit the greatest amounts of VOC emissions. In 2006-2008, the EPA 

issued 12 new CTG’s in three groups. 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. Per the CAA, CTG’s establish presumptive 

RACT for the VOC sources they cover. CTG RACT can apply to sources at a level much lower 

than the 100 tpy threshold employed for other RACT sources in moderate ozone nonattainment 

areas. In fact, some of these newly-issued CTGs apply to sources with emissions as low as 2.5 

tpy. Any state with moderate ozone nonattainment areas must implement equivalent RACT for 

all promulgated CTGs prior to redesignation of those areas. The Department developed 

amendments to four VOC rules to address these new CTGs for which there are existing 

applicable sources in the St. Louis nonattainment area. 

Three of the new rulemakings to address the new CTGs were proposed for public hearing March 

31, 2011, and were adopted by the MACC on April 28, 2011. The adoption of these CTGs was a 

necessary element to allow the St. Louis area to be redesignated to attainment for the 1997 ozone 

standard. The three rules that have been amended to account for these new CTGs include: 

• 10 CSR 10-5.330 Control of Emissions From Industrial Surface Coating Operations
30 

• 10 CSR 10-5.340 Control of Emissions From Rotogravure and Flexographic Printing

• 10 CSR 10-5.442 Control of Emissions from Lithographic Printing Operations

The three rules listed above were submitted to EPA for inclusion in the state implementation 

plan following their April 28, 2011 MACC adoption. One other rule is currently being amended 

to address CTG requirements in the St. Louis area. 10 CSR 10-5.455 Control of Emissions from 

Solvent Cleanup Operations, is currently in the process of being amended. This rule is expected 

to be adopted by the MACC in 2012 with an anticipated EPA SIP submittal in April of 2012. 

RACT is not a new requirement for the 1997 8-hour ozone NAAQS. Missouri has previously 

addressed RACT requirements in the St. Louis nonattainment area in developing attainment 

plans for the 1-hour ozone standard. For the 1997 8-hour standard, the Department developed a 

RACT demonstration as an element to the ozone SIP revision. Per the federal implementation 

rule for the 1997 ozone standard, the RACT demonstration was to be submitted as a separate 

element prior to the submittal of the attainment demo and other elements of the SIP revision. On 

September 28, 2006, the MACC held a public hearing for the proposed RACT demonstration. 

The RACT plan was adopted on December 7, 2006 and submitted to the EPA on January 5, 

2007. 

Since these new CTGs were not considered in the 2006 RACT demonstration, and in an effort to 

ensure that RACT determinations for the St. Louis nonattainment area are ongoing and 

continuous, the Department developed an update to the 2006 RACT demonstration to support 

this redesignation request. This updated RACT demonstration will show how RACT has been 

upgraded as appropriate since the last RACT submittal. This updated RACT document was 

adopted by the MACC on April 28, 2011 and submitted to EPA on May 25, 2011. 

For a more detailed discussion of RACT issues, please refer to the updated RACT demonstration 

adopted April 28, 2011, which can be found at http://dnr.mo.gov/env/apcp/sips.htm#ozone

4.4 Permanent and Enforceable Controls 

The Air Program provides assurance that all of the control measures adopted by state rules and 

listed in this document that have been used to attain the 1997 8-hour ozone standard are 

permanent and enforceable. Any revisions to the control measures included in this document 

will be submitted as a SIP revision to EPA for approval. 

The NOX SIP Call included rules for the control of NOX emissions from four different source 

groups including electric generating units, non-electric generating boilers, Portland cement kilns, 

and stationary internal combustion engines. The rule written to comply with the NOX SIP Call 

requirements for EGUs and was 10 CSR 10-6.360 Controlling NOX Emissions From Electric 

Generating Units and Non-Electric Generating Boilers, however this rule was replaced when 

implementation of the Clean Air Interstate Rule (CAIR) began in 2009 and CAIR will be 

replaced by the federal Cross-State Air Pollution Rule (CSAPR) in 2012 as discussed in the 

following paragraph. CSAPR does not include regulations for non-EGU boilers, specifically 

Trigen Units 5 and 6 and Anheuser Busch Unit 6. However these three units have all been 
31 

retired, and received retired unit exemptions that prohibit these units from operating. The signed 

EPA retired unit exemption forms for these three units are included in this document as 

Appendix G. The rules written to comply with the NOX SIP Call requirements for Portland 

cement kilns, and stationary internal combustion engines are 10 CSR 10-6.380 Control of NOX

Emissions From Portland Cement Kilns, 10 CSR 10-6.390 Control of NOX Emissions From 

Large Stationary Internal Combustion Engines, both of which currently remain permanent and 

enforceable in Missouri’s SIP. 

EPA issued the Clean Air Interstate Rule (CAIR) on May 12, 2005 and the CAIR federal 

implementation plans on April 26, 2006. In 2008, the US Court of Appeals for the DC Circuit 

remanded CAIR to EPA. EPA’s CSAPR will replace the 2005 CAIR in 2012 using new 

approaches consistent with the court’s opinion. A supplement to CSAPR was proposed on July 

6, 2011, which adds Missouri and five other states to the ozone season NOX trading program 

established through CSAPR. The supplemental proposal is expected to be finalized in November 

2011. Both CAIR and CSAPR establish ozone season NOX emissions caps for large electric 

utilities in Eastern states throughout the country. The CAIR requirements for ozone season NOX

pollution reductions currently remain in effect and the CAIR regional control programs will 

continue operating until January 2012, when implementation of CSAPR begins. When the 

supplemental proposal is final, CSAPR will ensure that ozone season NOX emission reductions 

established by CAIR are permanent and enforceable over the life of this maintenance plan. 

Federal regulations for the control of mobile sources are expected to be tightened in the future. 

The mobile source control measures have resulted in the significant reductions in both NOX and 

VOC emissions. The continued tightening of federal mobile source standards and phase out of 

older higher polluting vehicles will continue to contribute to maintenance of the 1997 8-hour 

ozone NAAQS 

Additionally, there are numerous other rules that provide permanent and enforceable controls for 

NOX and VOC emissions in the St. Louis nonattainment area. The rules in Title 10 Division 10 

Chapters 5 and 6 of the Missouri Code of State Regulations include permanent and enforceable 

control measures for ozone precursor emissions in the St. Louis nonattainment area. These 

controls include control technique guidelines for numerous VOC sources, open burning 

restrictions, and emission standards for incinerators. For additional information on state 

regulations to control VOC emissions in the St. Louis area, see the 2011 Reasonably Available 

Control Technology Demonstration Update for the 1997 8-Hour Ozone Standard in the St. Louis 

Area.
32 

5. Maintenance Plan Demonstration: Emission Inventory and 

Controls from 2008 - 2022 

This section provides a detailed emissions inventory for 2008 and a projected emission inventory 

for 2022. This section also includes a discussion of regulations that have become effective since 

2008, and a list of expected future regulations that will help to continue to control NOX and VOC 

emissions in the St. Louis area. The Air Program commits to keeping all previously adopted 

control measures in effect after redesignation. In addition, Prevention of Significant 

Deterioration (PSD) requirements will apply to construction of new major sources and to 

significant modifications of existing sources. Future transportation plans will also be required to 

conform to the conformity plan budgets. These existing and future control measures identified in 

the maintenance plan are relied upon to maintain the 1997 8-hour ozone NAAQS. 

5.1 Base/Attainment Year Inventory and Future Year Emission Projections 

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

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

Air Program has projected NOX and VOC emissions for the St. Louis nonattainment area for 

2022. Emissions for this projection year are compared to emissions levels in 2008 to determine 

if emissions levels are sufficient to maintain the NAAQS during this period. 

For the purposes of this section, a modified 2008 emission inventory was developed. The 2008 

inventory in this section will act as the base year compared to the 2022 inventory detailed in this 

section. The alternative 2008 inventory will include all point, area, on-road mobile, and off-road 

mobile source categories. The emissions from point, area, and off-road mobile source categories 

are identical to the attainment year inventory listed in the previous section. However, the onroad mobile source inventory is dramatically different. This is due to the fact that a different 

mobile emission model was used to develop the inventory in this section of the document. 

For this Section of this document, on-road motor vehicle emissions were estimated using U.S. 

EPA’s MOVES 2010A motor vehicle emissions model and VMT data from East-West Gateway 

Council of Government in coordination with the St. Louis Transportation Conformity 

Interagency Consultation Group. MOVES 2010A is a completely redesigned model, not just an 

updated version of the previous mobile model. The way MOVES calculates emissions has 

changed to reflect EPA’s more current understanding of the emissions produced by vehicles and 

the various factors that affect the emissions. NOX emissions were found to be higher because of 

the larger portion that extended idling of heavy duty vehicles contributes to the emissions total. 

VOC emissions calculated with MOVES are comparable to VOC emissions calculated with 

Mobile 6.2, however they are slightly higher. As a result of these changes to the model, MOVES 

produced higher emissions estimates for both 2008 and 2022 than were originally created with 

Mobile 6.2 via NMIM. Therefore, in addition to running a projected emissions budget for 2022 

for on-road emissions, 2008 base year emissions were also run using MOVES. This allows for a 

meaningful comparison in emissions from 2008 to 2022. By using MOVES to calculate the 

2008 and 2022 mobile emission inventories, a smooth transition can occur to new the mobile 

model that must be used in future SIPs and transportation conformity determinations. Additional 
33 

details about the development of the 2008 and 2022 on-road mobile emissions inventories are 

located in Appendices B and C of this document, respectively. 

The projected point and area source emissions in the St. Louis area for 2022 were estimated 

using the 2008 base year inventory and growth factors appropriate for each source category. The 

2008 and 2022 emissions from point, area, on-road mobile, and off-road mobile source 

categories are listed in Tables 5-1 and 5-2. Growth factors were created from the EGAS model 

(http://www.epa.gov/ttnecas1/egas5.htm) using economic growth projections from the Policy

Insight® Model for Regional Economic Model, Inc (REMI). An adjustment was made for a 

consent agreement between the Air Program and MEMC Electronics Materials Incorporated for 

the company to continue to operate their scrubbers for the control of NOX from their acid 

bath/etching process. This consent agreement has been submitted to EPA for inclusion in 

Missouri’s SIP. Finally, based on a review of the Federal CSAPR and consultation with Ameren 

UE, the owner of the four largest point source emitters of NOX in the nonattainment area, future 

projections of NOX emissions from these sources were determined by using the allowances listed 

in the proposed supplement to CSAPR along with a 21% variability factor, which was included 

in the final CSAPR for the ozone season trading program. CSAPR was finalized July 6, 2011, 

and the supplement to CSAPR, which adds Missouri into the ozone season NOX trading 

program, is expected to be finalized in November 2011. Using a 21% variability factor is very 

conservative and not expected to be reached in any year by these four facilities combined. 

Detailed information about the development of the point and area source inventories for the 

future year, 2022, can be found in Appendix D of this document. 

Off-road emissions projections for 2022 were developed using the growth factors contained in 

U.S. EPA’s NONROAD model. The NONROAD model also includes control factors for federal 

controls that have been promulgated. The on-road mobile source emissions listed in Tables 5-1 

and 5-2 were calculated using MOVES 2010A. The VMT data was provided by East-West 

Gateway Council of Government in coordination with the St. Louis Transportation Conformity 

Interagency Consultation Group. The figures assume the continued use of reformulated gasoline, 

the continued phase-in of the Tier 2 motor vehicle emissions standards, and the continuing 

operation of a basic vehicle inspection and maintenance program. Total VMT for 2022 were 

assumed to increase at a rate of 1.5 percent per year from 2008, as provided by East West 

Gateway Council of Governments in coordination with the St. Louis Transportation Conformity 

Interagency Consultation Group. Detailed information about the development of the on-road and 

off-road mobile source inventories for future year, 2022, can be found in Appendix C of this 

document. 

Table 5-1. 2008 VOC and NOX Emissions for the Missouri Side of the 1997 St. Louis 

8-Hour Ozone Nonattainment Area (tons per ozone season day) 

Source Category NOX VOC 

Point Sources 88.84 18.0 

Area Sources 6.52 98.74 

On-Road Mobile Sources 160.38 58.53 

Off-Road Mobile Sources 60.85 46.44 

Total 316.59 221.71 
34 

Table 5-2. 2022 VOC and NOX Emissions for the Missouri Side of the 1997 St. Louis 

8-Hour Ozone Nonattainment Area (tons per ozone season day) 

Source Category NOX VOC 

Point Sources 92.81 25.79 

Area Sources 6.77 121.19 

On-Road Mobile Sources 44.57 21.20 

Off-Road Mobile Sources 44.37 28.21 

Total 188.52 196.39 

Table 5-3 provides a comparison of emissions for the years 2008 and 2022, using the 2008 onroad mobile source emissions listed in Table 5-1 to reflect the MOVES values for consistent 

comparison purposes. The table shows the differences by source category along with the total 

changes in emissions for each pollutant listed. As shown in the table, both NOX and VOC 

emissions within the nonattainment area are expected to decrease significantly between 2008 and 

2022. Based on these emissions trends of NOX and VOC it is expected that air quality will 

continue to meet the 1997 8-hour ozone NAAQS throughout the maintenance period. 

Table 5-3. Comparison of 2008 and 2022 VOC and NOX Emissions for the Missouri Side of 

the 1997 St. Louis 8-Hour Ozone Nonattainment Area (tons per ozone season day) 

Source Category NOX VOC 

Point Sources* + 3.97 + 7.79 

Area Sources* + 0.25 + 22.45 

On-Road Mobile Sources* - 115.81 - 37.33 

Off-Road Mobile Sources* - 16.48 - 18.23 

Total* - 128.07 - 25.32 

*Note: A negative value indicates a projected decrease in emissions from 2008 to 2022. 

A positive value indicates a projected increase in emissions from 2008 to 2022.

It should be noted that the projected increase in VOC emissions for area sources are based on 

(EGAS) growth factors. Due to the use of these growth factors, emissions of VOC from area 

sources are projected to increase significantly by 2022. However, these projected increases are 

likely overstated and actual area source emissions of VOC are not expected to increase as much 

as the growth factors suggest. EPA’s Regulatory Impact Analysis (RIA) for the 2006 PM 

NAAQS rule, Appendix D (http://www.epa.gov/ttn/ecas/regdata/RIAs/Appendix%20D--

Inventory.pdf), notes on pages D-29 to D-36, that though REMI data was used in their emission 

forecasting method, the oversimplification of emissions growth based on economic factors likely 

overestimates projected emissions. EPA’s recognition of the downward trend in emissions 

during times of economic growth supports the conclusion that the VOC increases for area 

sources are likely an artifact of the growth methodology. From page D-36: 

-While it is not clear that all of the factors that have served to produce this historical 

decline will continue to operate in the future, it appears unreasonable to assume that we 

currently have arrived at an ‘inflection point’ past which the trend will stop or reverse 

itself. Indeed, because the available data show that a number of large sources in the 

sectors of interest have no or limited pollution controls, it is reasonable to expect 

emissions rates will be steady or decline. Continuing to ignore this factor in future-year 
35 

emission projections may increasingly skew the predicted emissions increase, and the 

farther into the future the forecast the more dramatic the impact. The preceding and 

other explanations suggested that we need to reevaluate our emission forecasting 

approaches for stationary non-EGU sources to incorporate factors not adequately 

considered in past methodologies.

The projected decreases in NOX and VOC emissions from 2008 to 2022 are primarily due to 

decreases in the mobile source category. Average ozone season daily NOX and VOC emissions 

in the St. Louis area from on-road and off-road mobile sources are projected to decrease 

approximately 132 tons/day and 56 tons/day, respectively. That amounts to an over 40% 

reduction of total NOX emissions and an over 25% reduction of total VOC emissions, while point 

and area source NOX emissions are expected to remain relatively stable, and point and area 

source VOC emissions are projected to increase slightly. 

Additional details about the 2008 and 2022 emission inventories can be found in Appendices B 

and D, respectively. It should also be noted that the emissions projections included here do not 

reflect the reductions expected from a range of measures being implemented to reduce diesel 

emissions in the St. Louis nonattainment area. These measures have been funded through 

sources such as the: 

• U.S. EPA’s Midwest Clean Diesel Initiative 

• Congestion Mitigation and Air Quality Improvement (CMAQ) Program 

• Diesel Emissions Reduction Act (DERA) 

• American Recovery and Reinvestment Act of 2009 

• Heavy Duty Diesel Idling Rule, 10 CSR 10-5.385

• Various supplemental environmental projects 

These projects include the installation of particulate filters, diesel oxidation catalysts, closedcrankcase ventilation systems, and direct-fired heaters on school and transit buses, and 

municipally-owned utility vehicles, upgrading diesel construction engines with engines meeting 

more stringent emissions standards, and installing auxiliary power units on over-the-road trucks 

to reduce idling. It is anticipated that DERA and CMAQ funding will continue to support 

additional diesel emissions reduction projects in the near future. 

5.2 Interim Year Emission Inventory: 2017 

The Air Program has developed an Interim Emission inventory for the Missouri side of the St. 

Louis nonattainment area. Interim year 2017 was decided to be used as it is the midway point 

between 2012, the year in which this plan is expected to be approved, and 2022, the last year in 

the ten year maintenance plan period. All assumptions and controls used in developing the 

project 2022 emission inventory in Section 5.1 of this document were also used to project the 

2017 inventory. Table 5.4 summarizes the emissions for point, area, on-road mobile, and offroad mobile sources that are projected for 2017 for the Missouri side of the St. Louis 

nonattainment area. The Air Program commits to analyzing actual 2017 emissions for the 

Missouri side of the St. Louis nonattainment area and comparing the actual 2017 emissions to the 
36 

projected 2017 emissions listed in Table 5.4 to ensure the area keeps pace with the reductions 

expected throughout the maintenance period. Additional details about the development of the 

2017 interim year emission inventory can be found in Appendix C of this document. 

Table 5-4. 2017 VOC and NOX Emissions for the Missouri Side of the 1997 St. Louis 8-

Hour Ozone Nonattainment Area (tons per ozone season day) 

Source Category NOX VOC 

Point Sources 91.20 22.79 

Area Sources 6.68 112.60 

On-Road Mobile Sources 61.91 26.97 

Off-Road Mobile Sources 46.89 29.46 

Total 206.68 191.82 

5.3 Controls to Remain in Effect 

The Air Program provides assurance that all of the control measures adopted by state rules and 

listed in this document that have been used to attain the 8-hour ozone standard are permanent and 

enforceable. Any revisions to the control measures included in this document will be submitted 

as a SIP revision to EPA for approval. Additional information with respect to the ongoing 

control of NOX and VOC sources in the St. Louis area can be found in subsection 4.4 of this 

document. 

5.4 Future Federal Control Measures 

There are currently several federal control measures that have recently been proposed or 

promulgated that are expected to greatly reduce the amount of NOX and VOC emissions in the 

St. Louis area. The control measures expected to have the greatest effect on NOX and VOC 

emissions in the St. Louis area include the federal CSAPR, the National Emissions Standards for 

Fossil-Fuel Fired Electric Utility Steam Generating Units (Utility MACT), National Emission 

Standards for Hazardous Air Pollutants for Major Sources: Industrial, Commercial, and 

Institutional Boilers and Process Heaters (Boiler MACT), improved motor vehicle fuel efficiency 

standards, and the phase in of tier 4 emission standards for nonroad engines. 

CSAPR and the improved federal mobile source regulations were both considered when 

developing the future emissions inventory in order to demonstrate continued maintenance with 

the 1997 8-hour ozone standard. EPA projects that under CSAPR, annual NOX emissions will be 

100,000 tons lower nationwide in 2012, compared to baseline 2012 projections. As stated 

earlier, federal motor vehicle and nonroad engine standards are only expected to be tightened in 

the future which will also contribute to NOX and VOC emission reductions. These recent and 

anticipated future federal control measures are expected to result in continued decreases in NOX

and VOC emissions both nationwide and in the St. Louis area. These measures will greatly 

assist current and ongoing efforts in the St. Louis area to maintain compliance with the 1997 8-

hour ozone NAAQS. 
37 

The Utility MACT and the Boiler MACT were both written to address hazardous air pollutants, 

and will therefore have the greatest reductions in pollutants such as PM2.5 and SO2. However, if 

owners of boilers and EGUs subject to these new rules decide to improve plant efficiency or 

switch to cleaner fuels for compliance strategies, then there is expected to be co-benefits for NOX

and VOC emissions from these sources. The Air program did not rely on the Utility MACT or 

the Boiler MACT when developing the future year emissions inventory or to determine that the 

St. Louis area would remain in attainment of the 1997 8-hour ozone NAAQS; however the 

anticipated reductions from these new rules may also contribute to the future attainment of the 

1997 8-hour ozone NAAQS in the St. Louis area. 

5.5 Provisions for Permitting New or Modified Emissions Sources 

In accordance with the Clean Air Act, Missouri has a long-standing and fully implemented New 

Source Review (NSR) permitting program for new major sources and significant modifications 

of existing sources. This NSR program in any attainment area is referred to as a Prevention of 

Significant Deterioration (PSD) permitting program. One of the major components of the PSD 

program is the implementation of Best Available Control Technology (BACT) on new major 

sources or significant modification of existing major sources. Missouri has been delegated full 

authority to implement the PSD program by the EPA. 

In this document, the Department is requesting redesignation to attainment under the 1997 8-

hour ozone standard. However, the St. Louis nonattainment area is expected to be designated as 

nonattainment under either the 2008 Ozone NAAQS or its reconsideration. If this is case, the 

State of Missouri is fully committed to continuing its NSR permitting program for nonattainment 

areas which makes new major sources and significant modifications of existing sources subject 

to the Lowest Achievable Emission Rate (LAER) as well as offsets and an alternate site analysis 

pursuant to the CAA. 
38 

6. Transportation Conformity 

Transportation conformity is required under CAA section 176(c) (42 U.S.C. 7506(c)) to ensure 

that transportation plans, transportation improvement programs and federally supported highway 

transit project activities are consistent with (“conform to”) the purpose of the SIP. Conform to 

the purpose of the SIP means that transportation activities will not cause new air quality 

violations, worsen existing violations, or delay timely attainment of the relevant NAAQS or any 

interim milestones. These requirements are found in Clean Air Act section 176(c)(B)(i), (ii), and 

(iii): “That such activities will not cause or contribute to any new violation of any standard in 

any area; increase the frequency or severity of any existing violation of any standard in any area; 

or delay timely attainment of any standard or any required interim emissions reductions or other 

milestones in any area.” Transportation conformity applies to areas that are designated 

nonattainment, and those areas redesignated to attainment after 1990 (“maintenance areas”) for 

transportation-related criteria pollutants: Carbon monoxide (CO), ozone, nitrogen dioxide (NO2) 

and particulate matter (PM2.5 and PM10). 

This section describes and establishes the St. Louis nonattainment area motor vehicle emissions 

budget associated with the ozone maintenance plan. Approval of the maintenance plan will 

establish new VOC and NOx motor vehicle emissions budget for the maintenance year, 2022. 

EPA requires motor vehicle emission budgets be established for the last year of the maintenance 

plan. 

The budgets reflect an emissions level determined using 2008 VMT provided by East West 

Gateway. The 2008 VMT data was generated from East-West Gateway's Traffic Demand Model 

and then compared to Highway Performance Monitoring System (HPMS) data. Through this 

comparison, calibration factors were developed and then applied to the VMT data from the 

Traffic Demand Model in order to estimate the actual 2008 VMT for the St. Louis nonattainment 

area. The budgets also reflect a VMT growth at an annual rate of 1.5 percent from year 2008 

levels to 2022. The 1.5 percent growth rate for use in projecting 2008 VMT to 2022 was 

developed through a coordinated effort with MoDOT, Illinois Environmental Protection Agency, 

the Federal Highway Administration, Illinois Department of Transportation, and East-West 

Gateway. Table 6-1 shows the actual historical annual VMT on state owned roads for the 

Missouri Portion of the St. Louis nonattainment area. In the past twenty-five years, VMT growth 

has varied considerably for the Missouri side of the St. Louis nonattainment area ranging as high 

as 6.7 percent in 1988 and as low as negative 1.8 percent in 1991. The average annual growth 

rate over the past twenty-five years is 1.9 percent. However, the traffic demand models used by 

East-west Gateway projects approximately 1 percent annual VMT growth for the next 10 years. 

The traffic demand model used by East-West Gateway uses current economic trends as a factor 

to calculate projected growth rates. With such extreme variations in a relatively short amount of 

time, it is not reasonable to project VMT to a future year solely considering current economic 

trends. In addition, emission plans for maintenance must be based on permanent and enforceable 

reductions, such as federal emission standards. Due to the worst economic downturn since the 

Great Depression, the economy has been struggling in the past few years, which has resulted in 

lower projected VMT growth rates from the traffic demand model. For the purposes of this 

maintenance plan, the 1.5 percent VMT growth rate was selected and agreed to by both states for 

consistency and to account for the expected economic rebound, which would result in higher 

VMT than projected by the traffic demand model. On February 22, 2011, the Air Program 
39 

discussed the use of the 1.5 percent growth rate to be used in this Maintenance Plan with the 

Interagency Council of Governments (IACG) group responsible for transportation conformity in 

the St. Louis nonattainment area. Illinois EPA stated that they too planned to use a 1.5 percent 

growth rate in their maintenance plans for the St. Louis area for both PM2.5 and Ozone, and the 

members of the IACG agreed that a 1.5 percent growth rate was reasonable to use for the 

purposes of this plan. Table 6-2 summarizes the estimated 2008 and projected 2022 annual 

VMT used for each county in the Missouri Portion of the St. Louis nonattainment area. 

Once the county level annual VMT numbers for 2022 were calculated MOVES 2010a was used 

and all months for 2022 were selected to create an annual emissions profile. The emissions for 

the months of April through October were totaled and divided by 214, the number of days in 

those months, to give average ozone season day emissions, which are reflected in the 

transportation conformity budget in Table 6.2. 

Table 6-1. Historical VMT in the Missouri Portion of the 1997 St. Louis 8-Hour Ozone 

Nonattainment Area (State Owned Roads Only) 

Year Annual VMT Annual Growth Rate 

1985 8,308,235,850 

1986 8,838,007,070 6.4% 

1987 9,168,965,710 3.7% 

1988 9,779,349,735 6.7% 

1989 10,279,500,110 5.1% 

1990 10,535,025,660 2.5% 

1991 10,342,044,685 -1.8% 

1992 10,745,357,640 3.9% 

1993 11,013,078,205 2.5% 

1994 11,670,927,195 6.0% 

1995 11,960,972,985 2.5% 

1996 12,112,134,815 1.3% 

1997 12,463,661,570 2.9% 

1998 12,593,954,160 1.0% 

1999 12,562,808,345 -0.2% 

2000 12,584,108,650 0.2% 

2001 12,816,788,850 1.8% 

2002 12,998,755,585 1.4% 

2003 13,057,922,815 0.5% 

2004 13,121,705,470 0.5% 

2005 13,102,295,865 -0.1% 

2006 13,114,079,525 0.1% 

2007 13,473,086,955 2.7% 

2008 13,334,059,915 -1.0% 

2009 13,349,210,335 0.1% 

2010 13,236,646,160 -0.8% 
40 

Table 6-2. 2008 and 2022 Annual VMT by County 

County 2008 Annual VMT 2022 Annual VMT 

Franklin 1,636,760,381 2,016,088,979

Jefferson 1,884,745,023 2,321,545,483

St. Charles 2,728,058,895 3,360,302,178

St. Louis 11,924,864,323 14,688,519,968

St. Louis City 3,450,450,085 4,250,111,666

Totals 21,624,878,706 26,636,568,272

In the Missouri portion of the St. Louis nonattainment area, transportation conformity for the 

ground-level ozone standard will be based on these submitted motor vehicle budgets after EPA 

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

This conformity budget replaces any and all previous budgets used for ground-level ozone 

conformity demonstrations in the Missouri portion of the St. Louis ozone nonattainment area. 

Table 6-3 identifies the 2022 motor vehicle emissions budgets for the 1997 St. Louis 8-hour 

ozone nonattainment area for use in transportation conformity analyses. The emissions budgets 

were created using MOVES 2010A. All inputs used to create these budgets can be found in 

Appendix D-3. 

Table 6-3. Motor Vehicle Emissions Budgets for the Missouri Portion of the 

St. Louis 8-Hour Ozone Nonattainment Area in Tons per Ozone Season Day

Pollutants 2022 Mobile Source Budgets 

(tons/ozone season day) 

NOX 44.57 

VOC 21.20 

 
41 

7. Contingency Measures 

Section 175(A) of the Clean Air Act specifies the requirements for maintenance plans. In 

addition to providing a plan for the maintenance of the NAAQS for at least ten (10) years after 

the redesignation, the plan shall also include a list of contingency measures to correct any 

violation of the fine particulate matter NAAQS after redesignation to attainment. 

Contingency measures are to be used to further reduce emissions in the event that future 

violations of the 1997 8-hour ozone NAAQS occur after redesignation to attainment. While 

these measures do not need to be fully adopted by the Missouri Air Conservation Commission 

prior to the occurrence of a NAAQS violation, the contingency measures are expected to be 

implemented as expeditiously as possible once a triggering event occurs. The maintenance plan 

must identify the triggers that determine when contingency measures will be adopted, and the 

measures that the Air Program will consider. 

The Air Program has developed a contingency plan for the Missouri portion of the St. Louis 

ozone maintenance area. The contingency plan which details the Level I and Level II triggers 

and corresponding actions to be taken is summarized in Table 7-1. The potential contingency 

measures, to be evaluated after a triggering event, are listed in Table 7-2. Consistent with this 

contingency plan, the Air Program agrees to adopt and implement, as expeditiously as is 

practicable, the necessary corrective actions in the event that violations of the 1997 8-hour ozone 

NAAQS occur anywhere within the St. Louis ozone maintenance area after redesignation to 

attainment. The implementation of contingency measures under Level I or Level II triggers will 

take place as expeditiously as practicable, but in no event later than twenty-four (24) months 

after the Air Program makes a determination, based on quality-assured ambient data, that a 

violation of the appropriate trigger has occurred. 

The contingency plan provides for different levels of corrective responses should the ambient 8-

hour ozone levels exceed the NAAQS in any year. A Level I response would occur in the event 

that the fourth highest 8-hour ozone concentration at any monitoring site in the St. Louis 

maintenance area (including sites in Missouri and Illinois) exceeds 84 ppb in any year. The Air 

Program will evaluate the air quality and determine if adverse emission trends are likely to 

continue. If so, the Air Program will determine what and where controls may be required, as 

well as the level of emissions reductions needed to avoid a violation of the NAAQS. If controls 

are required, the potential contingency measures listed in Table 7-2 will be evaluated in addition 

to other measures that may be identified through the evaluation or that become available through 

future advances in control technology and methods. It should be noted that the EPA does not 

require a state to implement contingency measures when occasional exceedances are recorded. 

The Department’s voluntary commitment to initiate a Level I response is intended to prevent 

future violations of the NAAQS from ever occurring. 

A Level II trigger occurs when a violation of the 1997 8-hour ozone NAAQS at any monitoring 

station in the St. Louis maintenance area is recorded after it has been redesignated to attainment. 

The Air Program will conduct a thorough analysis to determine appropriate measures to address 

the cause of the violation. Contingency measures will be selected from those listed in Table 7.2 
42 

or from any other measured identified and deemed appropriate and effective at the time the 

selection is made. Level II triggers are more serious than Level I triggers and cost effectiveness 

thresholds could be increased when determinations for additional controls are made. 

The contingency measures listed in Table 7.2 are expected to be evaluated in the event of a Level 

I or Level II trigger; however federal actions that require control measures may also be taken into 

account when the analysis to determine the cause of a future violation occurs. These additional 

federal actions, while not actual contingency measures, may be evaluated in the event of a trigger 

to determine their effect on the levels of expected emissions from sources in the area in order to 

determine whether or not additional local control measures are necessary. The measures that 

may be evaluated in the event of a future trigger include future federal on-road vehicle standards, 

future federal nonroad engine standards for marine and locomotive engines, any future federal 

emission trading programs designed to address future ozone or PM NAAQS promulgations, the 

Commercial-Industrial-Institutional Boiler Maximum Achievable Control Technology (MACT) 

requirements, and the Utility MACT requirements. Furthermore, the Air Program remains 

committed to addressing future ozone NAAQS revisions through state implementation plans. 

These plans could include other control techniques not included in Table 7.2. These and any 

other newly identified potential control measures may also be considered in the analysis 

following a future Level I or II triggering event. 

The Air Program commits to compiling NOX and VOC emissions inventories for the St. Louis 

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

emissions trends analysis included in the contingency plan under Levels I and II. Since St. Louis 

is a bi-state nonattainment area, the Air Program commits to work with Illinois EPA to evaluate 

emissions trends and the causes of Level I and Level II triggers to determine appropriate control 

measures needed to assure continued attainment of the 1997 8-hour ozone NAAQS. 

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

processes. The Air Program will solicit input from all interested and affected persons in the area 

prior to selecting appropriate control measures. No contingency measures 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 

Missouri law. 
43 

Table 7-1. Contingency Plan for the Missouri Portion of the 1997 St. Louis 8-Hour Ozone 

Maintenance Area

Contingency Measure 

Trigger Action to be Taken 

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 Air program will evaluate the air quality and determine if 

adverse emission trends are likely to continue. If so, the Air 

Program will determine what and where controls may be required, 

as well as the level of emissions reductions needed to avoid a 

violation of the NAAQS. The evaluation shall be completed as 

expeditiously as possible and, if necessary, control measures shall be 

adopted and implemented as expeditiously as practicable, taking into 

consideration the ease of implementation and the technical and 

economic feasibility of the selected measures. This action will be 

taken no later than 24 months after the Air Program has determined 

that a Level I trigger has occurred. 

Level II Trigger

A monitored violation of 

the NAAQS at any 

monitoring station in the 

St. Louis, MO-IL 

maintenance area. 

The Air Program 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 as expeditiously as practicable, taking into 

consideration the ease of implementation and the technical and 

economic feasibility of the selected measures. This action will be 

taken no later than 24 months after the Air Program has determined 

that a Level II trigger has occurred. 

Table 7-2. Potential Contingency Measures for the Missouri Portion of the 1997 St. Louis 

8-Hour Ozone Maintenance Area

Contingency Measure 

Method List of Potential Contingency Measures to be Considered 

Implement controls for 

local individual sources 

with significant effects on 

the monitored violation 

• Identify local sources with significant NOX and/or VOC emissions 

and develop controls through consent agreements 

Revise rules that control 

NOX and VOC emissions 

• Lower the applicability thresholds in existing rules that control 

NOX and VOC 

• Lower the limits in existing rules 

• Broaden the geographical area of existing rules 

• Include new source categories under the applicability of existing 

rules 

New rules that control 

NOX and VOC emissions 

• Enhanced Heavy-Duty Diesel Anti-Idling Program (i.e. mandated 

rest periods and locomotives) 

• New Alternative Control Techniques (ACTs) for NOX sources 

• New CTGs for VOC sources 

• Architectural/Industrial/Maintenance (AIM) Coatings similar 

to Ozone Transport Commission (OTC) model rule 
44 

8. CONCLUSION 

The St. Louis 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 

nonattainment areas. Missouri has supported, with appropriate submittals, all of EPA’s 

redesignation obligations under Section 107 of the CAA and has addressed all the applicable 

maintenance plan requirements. This plan submission serves as the official redesignation request 

for the Missouri portion of the 1997 St. Louis non-attainment area to be considered for approval 

concurrently with the maintenance plan and other certain necessary rule actions submitted to 

EPA relating to new Control Techniques Guidelines. 

The Missouri Department of Natural Resources’ Air Pollution Control Program has prepared this 

maintenance plan to meet 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 and also supplies 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 Department 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 2022. These emissions projections indicate that emissions levels in the St. Louis 

nonattainment area will continue to decrease from attainment year 2008 levels, thereby 

maintaining the ozone NAAQS in future years. The state 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 department has the legal authority to implement and 

enforce all control measures. 

 Finally, this maintenance plan includes year 2022 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 tenyear maintenance period. This maintenance plan has been prepared in accordance with the 

requirements of the CAA and in conjunction with the guidance provided by EPA documents and 

staff.