Attainment Demonstration 

The Wisconsin Counties 

of 

Kenosha, Racine, Milwaukee, Waukesha, 

Ozaukee, Washington, Sheboygan, Manitowoc and Door 

From Nonattainment to Attainment 

Of the 1997 Eight-Hour Ozone NAAQS 

-------------------------- 

Revision to Wisconsin’s 

Ozone Air Quality Management 

State Implementation Plan 

-------------------------- 

Wisconsin Department of Natural Resources 

Bureau of Air Management 

P.O. Box 7921 

Madison, WI 53707 

Publ AM-395 2009 

September 2009 
Natural Resources Board

Christine L. Thomas, Chair, Stevens Point 

Jonathan P. Ela, Vice Chair, Madison 

John W. Welter, Secretary, Eau Claire 

Dave Clausen, Amery 

Preston D. Cole, Milwaukee 

Gary E. Rohde, River Falls 

Jane Wiley, Wausau 

Wisconsin Department of Natural Resources

Matthew J. Frank, Secretary 

Pat Henderson, Deputy Secretary 

Mary Ellen Vollbrecht, Executive Assistant 

WDNR Division of Air & Waste 

Al Shea, Administrator 

Suzanne Bangert, Deputy Administrator 

WDNR Bureau of Air Management

John H. Melby, Jr., Director 

Larry H. Bruss, Chief, Regional Pollutants and Mobile Source Section 

Principal Author

Bill Adamski 

Acknowledgments

A note of appreciation to the people who helped make this study possible: The WDNR Air Monitoring 

staff for effectively operating the state’s ozone and ozone precursor monitoring network. The WDNR 

emissions inventory specialists for compiling the detailed emissions inventories used in this study. The 

Lake Michigan Air Director’s Consortium (LADCo) for conducting the ozone modeling, whose results 

were used in performing the modeled attainment test. Donna Kenski (LADCo) for doing her CART 

analyses, which were used in this analysis. The WDNR Air Management staff whose review and 

comments of draft versions helped improve this study. 
i

Attainment Demonstration 

The Wisconsin Counties 

of 

Kenosha, Racine, Milwaukee, Waukesha, 

Ozaukee, Washington, Sheboygan, Manitowoc and Door 

From Nonattainment to Attainment 

Of the 1997 Eight-Hour Ozone NAAQS 

-------------------------- 

Revision to Wisconsin’s 

Ozone Air Quality Management 

State Implementation Plan 

-------------------------- 

Wisconsin Department of Natural Resources 

Bureau of Air Management 

P.O. Box 7921 

Madison, WI 53707 

Publ AM-395 2009 

September 2009 
ii

Table of Contents

 Page 

Table of Contents ii 

List of Figures iv 

List of Tables v 

List of Appendices v 

Chapter Description Page 

1 Introduction 1 

1.1 Attainment Demonstration: Purpose and Regulatory Background 1

1.2 Historical Overview: Wisconsin 8-hour ozone nonattainment areas 1 

1.3. Report Outline 3 

2 Conceptual Description: Ozone Dynamics in L. Mich. and E. Wis areas 4 

2.1 Introduction 4 

2.2 Synoptic-Scale Meteorological Influences to High Ozone in the L. Mich. area 4 

2.3 Mesoscale Meteorological Influences to High Ozone in Eastern Wisconsin 8 

3 Trends in Ozone Air Quality Measurements 13 

3.1 Introduction: Pollutant Trends Study as Supplemental Analyses 13 

3.2 Ozone Trends at Nonattainment Sites 13 

3.3 Ozone Exceedance Days & Hot Temperature Days 20 

4 Trends in Ozone Precursor Air Quality Data 22 

4.1 Introduction 22 

4.2 Diurnal Profiles of Hourly NOx 23 

4.3 Diurnal Profiles of Hourly VOCs 25 

4.4 Morning (6-9A CST) VOC and NOx Measurements 27 

4.5 Morning (6-9A CST) VOC / NOx Ratios in Milwaukee 29 

5 Emission Inventories and Implemented Control Measures 31 

5.1 Introduction 31 
iii

Chapter Description Page 

5.2 Wisconsin Control Strategies for Ozone Precursor Emissions 31 

5.2.1 VOC Reasonably Available Control Technology 32 

5.2.2 NOx RACT 33 

 5.2.3 Non-Motor Vehicle Ozone Control Measures in Addition to CAA 34 

 5.2.4 Traffic Reduction Measures 35 

 5.2.5 Controls to Remain in Effect 36 

5.3 RFP Emissions Inventories (EIs): Base 2002 and Projected 2008 36 

 5.3.1 2002 Base Year Emissions Inventory for RFP 37 

 5.3.2 Adjusted Base Year 2002 Emissions Inventory (EI) for RFP 40 

 5.3.3 2008 Projected Emissions Inventory (EI) for RFP 40 

5.4 Base and Future Year Inventories for the Modeled Attainment Test 42 

 

6 Ozone Attainment Demonstration Modeling 43 

6.1 Introduction 43 

6.2 Modeled Years and Emission Scenarios 43 

6.3 Modeling System 43 

6.4 Modeling Performance Evaluation 44 

6.5 Modeling Future Years and Modeled Attainment Test Results 44 

7 Additional Data Analyses: 48 

7.1 CART Ozone analyses 48 

7.2 NOx and VOC Concentrations vs. Wind Direction 51 

8 Summary and Conclusions. 53 

References 55 
iv

List of Figures 

# Description Page 

1 Wisconsin Counties Designated Nonattainment of the 1997 8-Hr O3 NAAQS 2 

2 Counties in Lake Michigan Basin – Current or Previously Designated Non 

 Attainment of the 1997 8-Hr O3 NAAQS 5 

3a Surface Synoptic Weather Map: 6AM CST 22 June 02 7 

3b Site Peak-Daily 1-Hr Ozone: S. Lake Mich Basin 22 June 02 7 

4 Time-Space Series 3-Min Averaged Ozone (Aloft vs Surface) Coastal 

 Southern Wis 2:21-2:36 PM CDT 17 June 87 10 

5 Time Series Hrly Surface Air Temperature Racine, WI and S. L. Mich 11 

6 Lake Breeze Diagram 12 

7 Annual Sum Totals Site-Day Exceedances of the 1997 8-hr NAAQS 

 Six Sites Near L. Michigan 1994-2008 15 

8 8-Hr Ozone Design Values, Annual Number of 8-hr O3 Exceedance Days - 

 Chiwaukee, WI 1988-2008 17 

9 8-Hr Ozone Design Values, Annual Number of 8-hr O3 Exceedance Days - 

 Milwaukee-Bayside, WI 1988-2008 17 

10 8-Hr Ozone Design Values, Annual Number of 8-hr O3 Exceedance Days - 

 Harrington Beach, WI 1994-2008 18 

11 8-Hr Ozone Design Values, Annual Number of 8-hr O3 Exceedance Days - 

 Sheboygan, WI 1997-2008 18 

12 8-Hr Ozone Design Values, Annual Number of 8-hr O3 Exceedance Days - 

 Manitowoc, WI 1994-2008 19 

13 8-Hr Ozone Design Values, Annual Number of 8-hr O3 Exceedance Days - 

 Newport, WI 1989-2008 19 

14 Peak Daily 8-Hr O3 > 84 ppb at any Eastern Wis O3 Site, Milwaukee 

 Airport NWS Daily Max Temps > 90F 1988-2008 21 

15 Numerator: Peak Daily 8-Hr O3 > 84 ppb at any Eastern Wis O3 Site, 

 Denominator: Milw Airport NWS Daily Max Temps > 90F 1988-2008 21 

16 Annual Diurnal Profiles: Median Hourly NOx Milw-UWMN 15 May - 

 15 Sept 1994-2000 24 

17 Annual Diurnal Profiles: Median Hourly NOx Milw-SER 15 May - 

 15 Sept 1999-2008 24 

18 Annual Diurnal Profiles: Median Hourly TNMOCs Milw-SER June- 

 July-Aug 1999 - 2007 26 

19 Median Site-Monthly NOx, TNMOCs Daily 6-9AM CST Averages 

Milw-UWMN June-Aug 1994-1999, Milw-DNR SERHQ June-Aug 1999-07 28 
v

List of Figures (continued) 

# Description Page 

20 Median Site-Monthly Median Values Daily TNMOC / NOx, Ratios 

6-9 AM: UWMN June-Aug 1994-1999, DNR SERHQ June-Aug 1999-07 30 

21 Concentration Trends in CART Nodes – 5 Wisconsin Shoreline Sites 49 

22 Concentration Trends in CART Nodes – 3 Milwaukee Monitors 50 

23 June-Aug Hrly NOx vs Hrly Wind Dir, Milwaukee 1999, 2007 52 

24 June-Aug Hrly VOCx vs Hrly Wind Dir, Milwaukee 1999, 2007 52 

List of Tables 

# Description Page 

1 Ozone Monitoring Sites, 2006-08 8-Hr Ozone Design Values 

 Wis Ozone Nonattainment Counties 14 

2 Emissions of Reactive Organic Gases in 9-County Area 1985 & 2005 33 

3 Summary: NOx and VOC Emissions Inventories 38 

4 Base (2002 Actual) and Future (2008) NOx Emission Inventories 39 

5 Base (2002 Actual) and Future (2008) VOC Emission Inventories 39 

6 Summary NOx and VOC Emission Calcs For RFP 41 

7 Predicted Future Year 8-Hr Ozone Design Values (Modeled 

 Attainment Test Results) 7 Wis Ozone Nonattainment Sites 47 

List of Appendices

A LADCo, 2008: Regional Air Quality Analyses for Ozone, PM2.5, and Regional Haze: 

 Final Technical Support Document. 126 pp + appendices, April 25. 

B LADCo, 2006: Base K [2002] Strategy Modeling: Emissions. 15 pp, May 16. 

C LADCo, 2008: Base M [2005] Strategy Modeling: Emissions (Revised). 24 pp, 

D LADCo, 2008: Regional Air Quality Analyses for Ozone, PM2.5, and Regional Haze: 

 Final Technical Support Document (Supplement), 56 pp, September 12 

E Overview: VOC / NOx Ratios and Ozone Production 

F Listing: Promulgated WDNR Ozone Control Rules 

G Overview: CART Analysis Model 
vi

<Blank Page>
1

1 Introduction 

1.1 Attainment Demonstration: Purpose and Regulatory Background 

 

This document details an assessment of measured and modeled air quality data to demonstrate 

how full implementation of Wisconsin’s ozone air quality State Implementation Plan (SIP) and 

other factors have combined to help attain the 1997 eight-hour ozone national ambient air quality 

standard (NAAQS, 0.08 parts per million [ppm]) as of the end of 2008 for all areas of Wisconsin 

currently classified as nonattainment for this NAAQS (Figure 1). 

This attainment demonstration (AD) also documents how permanent and enforceable control 

measures of ozone precursors in Wisconsin’s ozone nonattainment area have resulted in 

substantial emission reductions for these counties to date. Furthermore, these control measures 

are projected to yield emission reductions that meet reasonable further progress (RFP) 

requirements. Chemical transport modeling for future years shows attainment and maintenance 

of the 1997 8-hour ozone NAAQS in Wisconsin through at least 2018. Supplemental analyses of 

measurement data are included to corroborate that ambient levels of ozone and ozone precursors 

has substantially diminished in eastern Wisconsin over the past 10-15 years. 

This AD satisfies one of the regulatory requirements established in Section 110 and Part D of the 

Clean Air Act for states requesting that nonattainment areas be considered for redesignation to 

attainment. 

1.2 Historical Overview: Wisconsin 8-Hour Ozone Nonattainment Areas 

Portions of eastern Wisconsin have had a long history of excessively high ozone levels. In 1979 

the US EPA designated counties in southeastern Wisconsin as nonattainment for the 1-hour 

ozone NAAQS (0.12 ppm). 

On July 18, 1997, the US EPA published a final rule (US EPA, 1997) that established a new 

ambient ozone NAAQS – a rolling 8-hour average not to exceed 0.08 ppm (equivalent to 84 

parts per billion [ppb]). On April 30, 2004, the US EPA published a final rule (US EPA, 2004b) 

that set forth designations and classifications for the 8-hour ozone NAAQS. These designations 

became effective on June 15, 2004. 

The US EPA’s April 30, 2004 action designated ten (10) Wisconsin counties (Figure 1) as 

nonattainment of the 8-hour ozone NAAQS. The counties of Manitowoc, Kewaunee and Door 

were designated as nonattainment - Subpart 1. The 6-county Racine-Milwaukee area (counties of 

Kenosha, Racine, Milwaukee, Waukesha, Ozaukee and Washington) and Sheboygan County 

were all designated nonattainment - moderate/Subpart 2. 

On March 27, 2008 the US EPA published a final rule (US EPA, 2008a) that established a 
2
3

new 8-hr ozone NAAQS of 0.075 ppm (75 ppb). The original 8-hour ozone NAAQS is now 

referred to by the year it was promulgated (1997). This Attainment Demonstration addresses 

only the 1997 8-hour ozone NAAQS. 

On May 21, 2008 the US EPA published a final rule (US EPA, 2008b) that redesignated 

Kewaunee County to attainment of the 1997 8-hour ozone NAAQS. The other 9 Wisconsin 

counties previously identified remain nonattainment for this NAAQS. 

1.3 Report Outline 

The structure to this AD follows the recommended guidance contained in the US EPA (2007) 

document entitled “Guidance on the Use of Models and Other Analyses for Demonstrating 

Attainment of Air Quality Goals for Ozone, PM2.5, and Regional Haze” (EPA-454/B-07-002). 

Specifically, the report answers questions raised in Part I of this guidance (“How Do I Use 

Results Of Models And Other Analyses To Help Demonstrate Attainment?“). 

Subsequently, the remaining chapters of this AD are outlined as follows: 

Chapter 2: A conceptual description that characterizes ozone dynamics in the larger Lake 

Michigan basin, then in the focused eastern Wisconsin area. 

Chapter 3: Ozone trends in Wisconsin ozone nonattainment areas during the past 20 years. 

Chapter 4: Trends in ozone precursor air quality measurements (VOCs and NOx) data in 

Wisconsin’s ozone nonattainment areas during the past 15 years. 

Chapter 5: An overview of the development of each of the emissions inventories used in this 

demonstration, as well as a brief discussion of the implemented reasonably available control 

measures to reduce precursor emissions in order to lower ozone levels. 

Chapter 6: An overview of the ozone modeling program and results designed to predict both 

base and future year ambient 8-hour ozone levels in Wisconsin’s ozone nonattainment areas. 

This discussion includes applying the US EPA’s modeling attainment test to the predicted results 

to assess whether attainment of the 1997 8-hour ozone NAAQS is achieved by the regulatory 

deadline date. 

Chapter 7: Supplemental analyses of ambient data are presented to help provide additional 

assessments on whether the 1997 ozone standard has been attained. 

Chapter 8: Summary and conclusions. 

Several appendices are included to supplement the information provided in this report. Some 

these appendices are included by internet links. 
4

2. Conceptual Description: Ozone Dynamics in Lake Michigan and Eastern Wisconsin 

2.1 Introduction 

This attainment demonstration assessment pertains to Wisconsin’s nine ozone nonattainment 

counties (Figure 1). However, excessively high ozone is prevalent throughout most of the 

shoreline areas in the Lake Michigan basin. Almost every county along the Lake Michigan’s 

shoreline, as well as some second and third tier inland counties, have measured violations of the 

1997 8-hour standard at one time or another and 10 of these counties were officially designated 

as nonattainment in 2004 (US EPA 2004b) (Figure 2). 

In order to mitigate excessive ozone in the Lake Michigan area - many control measures have 

been promulgated over the years to substantially reduce those emissions that contribute to ozone 

formation. While these actions have yielded much progress over the last three decades, groundlevel ozone remains a regional problem in this airshed, with exceedances of the 1997 8-hour 

ozone NAAQS still occasionally occurring and much of the region still in nonattainment of this 

air quality standard. 

A conceptual overview of the ozone problem is presented from the perspective of both the larger 

Lake Michigan region (Section 2.2) and the focused eastern Wisconsin nonattainment area 

(Section 2.3). 

2.2 Synoptic-Scale Meteorological Influences to High Ozone in the Lake Michigan Area 

The entire coastal tri-state urban area that extends from northern Indiana clockwise through 

Chicago and Milwaukee to Sheboygan, Wis (Figure 2) has more than 10 million inhabitants and 

is heavily industrialized. Consequently, regardless of the meteorology of the region, this massive 

complex of contiguous metropolitan areas generates a substantial amount of ozone precursor 

emissions with which to produce excessive ozone levels locally. 

Ozone has been a persistent air quality health problem throughout the Lake Michigan basin 

since the 1970s. In addition to the ozone nonattainment areas in Wisconsin (Figure 1), the eightcounty Chicago IL-Gary IN region and shoreline counties in Michigan have also been out of 

attainment with respect to either the 1-hour or 8-hour ozone NAAQS (or both) for much of the 

past 30 years (Figure 2). Southeastern Wisconsin was originally designated as being 

nonattainment of the ozone NAAQS (1-hour averaging time) in 1979. 

The four states (Wisconsin, Illinois, Indiana and Michigan) that border Lake Michigan along 

with the US EPA recognized in the late 1980s that a coordinated interstate approach was needed 

to bring the region into attainment of the ozone NAAQS. In 1989, the Lake Michigan states and 

the US EPA signed a Memorandum of Agreement (MOA) that created the Lake Michigan Air 

Directors Consortium (LADCO) for purposes of coordinating efforts among the states towards 

attaining the ozone NAAQS throughout the basin. 
5

Figure 2
6

This MOA also established that LADCo shall coordinate a comprehensive assessment of ozone 

dynamics in the Lake Michigan airshed in order to develop a more refined, targeted approach 

towards reducing the area’s ozone. This project, called the Lake Michigan Ozone Study 

(LMOS), included a massive field study during the summer of 1991. 

However, even before LMOS, other researchers (e.g,. Lyons, 1975, Lyons and Cole,1976) 

presented research that highlighted the unique ozone-conducive meteorology of the region at the 

synoptic weather scale (i.e., weather features of 24-48 hours duration) and mesoscale 

meteorology (i.e., weather features less than 24 hours duration). 

On the synoptic scale, the researchers demonstrated that high pressure systems can generate 

meteorological conditions that are very favorable to excessive ozone as the weather migrates 

through the region from west to east during late May - early September. These systems are 

typified by hazy, sunny skies with generally weak, clockwise-rotating winds and relatively 

shallow mixing (poor dilution). These weather conditions greatly assist in the buildup and 

photo-reactivity of considerable amounts of ozone precursors. 

The position of the surface high pressure system’s center is important with respect to ozone 

transport into the region. Haney, et al., (1989) estimated that 50% of Wisconsin's ozone 

exceedance days during 1980-1988 [1-hr ozone NAAQS] occurred when the center of a high 

pressure system was situated to the area's southeast (i.e., Ohio and east thereof) (Figures 3a and 

3b). Samson and Ragland (1977) showed through trajectory and synoptic-scale analysis of a 

1975 Lake Michigan ozone episode that "..adverse [air quality] conditions occurred when 

stagnant air originating in the Ohio River valley was transported northward on the western half 

of a high pressure system...into northern Illinois and southeastern Wisconsin". 

The WDNR (1988a, 1988b) conducted studies of Lake Michigan’s ozone meteorology along its 

western shoreline with Wisconsin. WDNR (1988a) included ozone measurements collected aloft 

via airplane. Both studies noted that the ozone transformation and transport processes in the 

vicinity of the Lake were extremely complex and warranted further analysis. However, both 

studies did identify interrelated ozone and weather features that supported the Lake Michigan 

ozone meteorology research of Lyons, 1975, Lyons and Cole,1976 

The LMOS contributed to a better understanding of synoptic-scale weather influences on ozone 

in the Lake Michigan area. Reports by Roberts, et. al. (1994), Hanna and Chang (1995), Dye, et 

al. (1994) and Korc, et al., (1993) Hanna and Chang (1995) generally conclude that ozone 

episodes are associated with high pressure systems over the eastern United States and transported 

pollutants and precursors from the south and east result in increased the region-wide ozone 

concentrations. 
7 ozone 
8

Ozone measurements collected aloft via aircraft present a reasonably good "snap shot" of the 

magnitude of ozone that can be transported into an area at any given time. Aircraft flights above 

Lake Michigan (Westberg et al. 1981, WDNR 1988, Hillery 1993, Korc et al. 1993, WDNR, 

2003) have monitored ozone that often exceeded both the ozone NAAQS and concentrations 

monitored at the surface in the Lake Michigan airshed (Figure 4). Since only a portion of the 

ozone formed near the surface is mixed vertically aloft, much of the additional ozone that is 

measured aloft must be coming from non-local sources. 

Both Korc, et al. (1993) and WDNR (2003) noted that aircraft-measured ozone concentrations 

aloft in the Lake Michigan area can often be quite substantial (Korc: 70 - 100 ppb) on high ozone 

days, even up to 100 - 150 km south of Lake Michigan. This is much higher than the generallyaccepted local rural background level of 30-40 ppb (Trainer, et al., 1993) and can occasionally 

exceed the ozone NAAQS. Korc, et al. (1993) estimated that upwind boundary ozone 

contributes 40-60% to the maximum ozone concentrations in the Lake Michigan airshed. The 

geographical domain of excessive ozone appears to be notably greater aloft than at the surface on 

episode days (WDNR 2003, Korc et al. 1993). 

In summary, all of these studies demonstrate that on warm, sunny, humid days in the Lake 

Michigan area with weak southerly flow emanating on the trailing edge of an atmospheric high 

pressure situated in the eastern U.S. – there can be a widespread incidence of high ozone where 

long-range transport is prevalent into the Lake Michigan area. 

Hanna and Chang (1995) further point out that “..the local pollutant sources in the GaryChicago-Milwaukee then add their [considerable emissions] contribution to the incoming 

pollutant mass” embedded in the southerly flow on warm sunny, hazy days (e.g., Figure 4). 

2.3 Mesoscale Meteorological (Lake Breeze) Influences to High Ozone in Eastern Wisconsin 

Wisconsin’s ozone nonattainment region is positioned along approximately 220 miles of 

Wisconsin eastern coastline with Lake Michigan (Figure 1). Lake Michigan with a surface area 

of approximately 22,400 square miles constitutes a huge heat sink during the warm months. 

Figure 5 highlights the considerable difference between the land air temperature (Racine, Wis) 

and the buoy-derived air temperature above the southern Lake Michigan surface during a 5 day 

ozone episode in June 2002. 

As described in section 2.2, synoptic weather conditions in the Lake Michigan basin that are 

favorable to the formation of high ozone levels include being on the western edge of a high 

pressure system during warm weather (Figure 3a). This synoptic scenario, in combination with 

the unique Lake-induced meteorological features produces a mesoscale environment in which 

the capability to produce ozone is greatly intensified. 

At the mesoscale meteorological scale, there is a strong temperature contrast between the warm 

land and cold lake (Figure 5). This scenario can lead to the formation of a daytime thermallydriven circulation cell called the lake breeze, which runs approximately perpendicular to the 

Lake Michigan shoreline (Figure 6). In a classical lake breeze circulation cell, the following 

series of inter-related processes take place: 
9

• A shallow but intensely stable conduction inversion exists just above the relatively 

cold Lake (Figure 6). During the early daylight hours the prevailing (synopticscale) surface winds transport ozone and fresh (morning rush hour) ozone precursor 

emissions towards the Lake (i.e., offshore flow). This emissions transport is 

confined to the shallow, stable conduction inversion (Roberts, et. al, 1994). 

• The newly-injected precursors’ in a stagnant, cloudless conduction inversion are 

subject to considerable sunlight and heat along with sufficient amounts of water 

vapor. This translates into the over-lake environment becoming an incredibly 

efficient ozone reaction chamber (Roberts, et. al, 1994). 

• By mid-morning a sharp horizontal temperature is formed along the shoreline 

between cold lake and increasingly warmer land (Figure 5). This gradient 

effectively “cuts off” additional flow, including pollutants into the conduction layer 

(Roberts, et. al, 1994). The lakeward winds are subsequently forced to flow up and 

over the conduction inversion (Figure 6). 

• Over the Lake - the aloft, land-originated flow is now subject to subsidence in the 

cooler Lake’s mesohigh and begins to sink. When the cooling air approaches the 

Lake’s surface – it spreads out, moving in all directions, including towards 

shoreline (Figure 6). 

• When this shallow, cool air flow (now filled with high amounts of ozone formed in 

the conduction inversion) reaches the shoreline, the onset of the onshore lake 

breeze is realized. 

• The lake breeze flow gradually dissipates within the first 2-15 miles onshore – 

largely restricting its major ozone impact to this narrow region. This translates into 

the ozone nonattainment counties being mostly confined to shoreline counties 

(Figures 1, 2). 
10
11

Figure 5: Time Series 

Hourly Surface Air Temperature

Racine, WI and S. Lake Mich. Buoy 

20 - 25 June 02

0

5

10

15

20

25

30

35

159

131721

159

131721

159

131721

159

131721

159

131721

159

131721

Hour of Day (CST)

Hrly Ambient Temp. (

C

Racine Ambient Temp. (C) L. Mich. Buoy Air Temp. (C)

Source: WDNR 2003 
12

Figure 6: An idealized depiction of a typical lake breeze circulation cell. 

Dashed line represents outer boundary of the inflow layer 

Conduction 

inversion 

 layer 

0 - 200 m

Source: WDNR 2003 
13

3 Trends in Ozone Air Quality Measurements 

3.1 Introduction: Pollutant Trends Study as Supplemental Analyses 

The US EPA (2007) states that an attainment demonstration uses “..modeling [and inventory] 

analyses to assess whether various emission reduction measures will bring an individual area into 

attainment for the NAAQS...” However, the US EPA also recommends that supplemental 

analyses should accompany all model attainment demonstrations. 

For this attainment demonstration of areas in eastern Wisconsin the following study of trends in 

ozone levels, as well a review of trends in ozone precursors (Chapter 4) constitutes one 

supplemental analysis for this project. 

3.2 Ozone Trends at Nonattainment Sites 

Table 1 identifies all ozone monitoring sites that the Wisconsin DNR operated during 2006-2008 

in the counties currently designated as nonattainment of the 1997 eight-hour ozone NAAQS. For 

the current 2006-08 data period all of these sites have 8-hour ozone design values (DVs) that are 

below the 8-hour ozone NAAQS (0.08 ppm [84 ppb]). This is the first time that every 

operational ozone monitoring site in Wisconsin’s ozone nonattainment areas attained the 8-hour 

ozone standard since they were officially designated as nonattainment (US EPA 2004b). 

The top part of Table 1 identifies six ozone monitoring sites (Chiwaukee, Milwaukee-Bayside, 

Harrington Beach, Sheboygan, Manitowoc and Newport) that are targeted for principal ozone 

analysis in this attainment demonstration technical support document (TSD). These sites were 

chosen for extra analysis for the following reasons: 

• They had the highest 8-hour ozone DVs in Wisconsin during both the 2005-07 and 2006-

08 periods (Chiwaukee, Sheboygan, Manitowoc and Newport all exceeded the 1997 8-

hour NAAQS during 2005-07). Because these sites have recently had the highest 8-hr O3 

DVs - the attainment demonstration analysis of these sites would show the biggest 

improvements in ozone air quality levels. 

• Geographically, the sites represent a good spread along Wisconsin’s eastern coastline: 

One site in each of the coastal nonattainment counties (save for Racine) (Figure 1). 

Ozone data from other ozone sites listed in Table 1 are also subject to assessment in this 

document. 
14

Table 1 

Ozone Monitoring Sites (a)

2006 – 2008 8-Hr Ozone Design Values 

Wis Ozone Nonattainment Counties 

Site Name Site Location County 

2006-08 8-hr 

O3 DV 

(ppb)(b) 

Primary Sites for 

Attain. Demo.

Analysis 

Chiwaukee Pleasant Prairie / 

Chiwaukee 

Kenosha 78 

Milw-Bayside Milw-Bayside Milwaukee 75 

Harrington Beach Harrington Beach State 

Park 

Ozaukee 74 

Sheboygan Sheboygan-Kohler Andre 

Park 

Sheboygan 82 

Manitowoc Manitowoc-Woodland 

Dunes 

Manitowoc 75 

Newport Newport State Park Door 80 

Additional Analysis 

Sites 

Milw-16th St. Health 

Ctr 

Milw-16th St. Health Ctr Milwaukee 75 

Milw-SER HQ Milw-SER HQ Milwaukee 68 

Milw-UWMN Milw-UWMN Milwaukee 72 

Grafton Grafton Ozaukee 72 

Racine Racine Racine 71 

Slinger Slinger Washington 65 

Waukesha Waukesha-Cleveland St. Waukesha 66 

(a) See Figure 1 for site locations 

(b) 8-hour ozone NAAQS: 0.08 ppm (84 ppb) 

Figure 7 displays the trend in the collective annual number of site-day exceedances of the 1997 

8-hour ozone NAAQS for these six primary ozone sites in the 15 years (1994-2008) that they 

were all operational. This graphs shows that there has been a wide range in the number of 

exceedance days over this period. However, the sites have witnessed considerably fewer 

exceedances during 2006-08 (37) than during any other 3 year period since 1994. Equally 

important is that all the sites – for the first time - recorded no ozone exceedances in 2008. 
15
16

For each of the six primary analysis sites - the history of 8-hour ozone DVs and annual number 

of exceedance days for varying durations are graphed in Figures 8-13. Each site has its own 

unique profile. Nevertheless, there are general commonalities in the graphs as follows: 

• For those sites whose ozone monitoring extends back to the late 1980s – there has been a 

substantial improvement in the ozone air quality from extremely high peaks (8-hr ozone 

DVs above 100 ppb) in the late 1980s to DVs in the range of high 80s to mid-90s by 

1994. 

• There was a general plateau in the 8-hour ozone DVs (range: 90 to 100 ppb) during the 

mid-to-late 1990s. However, there was still considerable variation in the year-to-year 

totals of site-day exceedances for each monitor. 

• Since approximately year 2000 all sites have witnessed a broad, albeit occasionally 

uneven, shift towards lower DVs (range: 80 to 90 ppb) and decreasing occurrences of 

exceedance days per year. The DV trend culminated with all six analyzed sites achieving 

attainment for the 2006-08 period. Four of these sites (Chiwaukee [Figure 8], Sheboygan 

[Figure 11], Manitowoc [Figure 12] and Newport [Figure 13]) were nonattainment during 

2005-07). The substantial decline in ozone exceedance days among all six sites is 

collectively borne out in Figure 7. 
17
18
19
20

3.3 Ozone Exceedance Days and Hot Temperature Days 

A major ingredient in the recipe for high ozone is the presence of relatively warm temperatures 

(i.e., above 80 F). Many of the photochemical reactions that produce ozone are expedited by 

ambient temperatures above 80 F (NRC, 1991). Holding emissions and air quality levels for 

ozone precursors approximately constant over a given time period, the incidence of high ozone 

days might reasonably be correlated with the occurrence of excessively warm days. LADCo’s 

(2008) definition of a “hot” warm day in the upper Midwest (i.e., days with maximum 

temperatures 90 F or greater) for ozone assessments was employed in this study. 

Milwaukee’s Mitchell Field Airport is located 3 miles west of Lake Michigan’s shoreline and is 

witness to much of the same weather that the six primary shoreline ozone sites experience. 

Additionally, its temperature record is more complete and better validated than any of the 

temperature archives from the WDNR sites. Consequently, the hourly temperature data from the 

National Weather Service (NWS) station at Mitchell Field (“MKE”) were used for this analysis. 

Figure 14 compares the annual number of calendar days with at least one ozone monitoring site 

exceeding the 1997 8-hour ozone NAAQS in eastern Wisconsin to the number of 90 F days at 

MKE during the period 1988 – 2008. The graph shows that the number of hot days at MKE has 

generally been most frequent during the current decade (save for the relatively cool years 2004 

and 2008 and the excessively hot year,1998. 

Nevertheless, the increasing number of MKE 90 F days has not resulted in more ozone 8-hr 

exceedance days since 2002. In fact, many more ozone exceedance days occurred during the 

1988 – 1999 period when there were fewer hot days (the anomalously warm 1988 excepted). 

The annual ratio of high ozone days to hot days in eastern Wisconsin (Figure 15) clearly displays 

the relatively poor correlation between the former and latter parameters. The ozone exceedance 

day / hot day ratio has greatly diminished from the high levels in earlier years (peak: 11.0 in 

1992) to ratios below 2 since 2002. Essentially a 90 F day at MKE is becoming an increasingly 

less reliable indicator that high ozone will occur somewhere in eastern Wisconsin on that day. 

In conclusion, this sizable improvement in the ozone air quality of eastern Wisconsin is even 

more remarkable considering that some of the region’s meteorological features (stagnating high 

pressure systems, lake breeze) greatly enhance the formation and transport of ozone in the Lake 

Michigan 

airshed.
21
22

4 Trends in Ozone Precursor Measurement Data 

4.1 Introduction 

Ambient ozone levels have a non-linear relationship to the presence of its precursors (NOx and 

VOCs). This Chapter assesses the trends in the area’s ambient VOC and NOx air quality 

measurements. 

As noted in Section 3.2, certain meteorological conditions are favorable to transport of sizable 

amounts of ozone into the Lake Michigan area. This meteorology is also conducive to advecting 

VOCs and NOx into the region. Consequently, the VOC and NOx measurements in Wisconsin 

can potentially include significant precursors that are emitted from outside of the State. 

Monitoring VOCs and NOx is relatively complicated and labor-intensive. Consequently, 

measuring these pollutants in Wisconsin’s nonattainment areas has been very limited, both in 

space (a few sites) and calendar (i.e., the ozone season). The only WDNR monitoring sites for 

ozone precursors that have data histories sufficiently long to adequately assess their trends over 

the years are located in Milwaukee (Figure 1): 

• University of Wisconsin-Milwaukee north campus (UWMN [AIRS # 550790041], 2116 

E. Kenwood Blvd). 

• DNR Southeast Regional Headquarters (DNR SERHQ, [AIRS # 550790026], 2300 N. 

Dr. Martin Luther King Dr.) 

During the 1990s the Milw-UWMN site was WDNR’s principle location for monitoring NOx 

and VOCs. The NOx measurements were hourly-averaged from a continuous sampler. The 

VOC concentrations were derived from the lab analysis of integrated ambient air samples 

collected in canisters - mostly for 3 hour averaging times during 6-9 AM CST. 

During 1999-2000 VOC and NOx monitoring shifted from Milw-UWMN to Milw-SER, which 

is located approximately 2 air miles southwest of UWMN. The NOx monitoring instrumentation 

at SER has been similar to what it was at UWMN. 

The VOC data collected at the SER site derived from analyzing a continuous flow of ambient air 

through an automated gas chromatograph (“autoGC”). The autoGC is operated only during the 

heart of Wisconsin’s ozone season (June-July-August). 

4.2 Diurnal Profiles of Hourly NOx 

Figure 16 displays the diurnal profile of median hourly NOx at Milw-UWMN during the most 

active portion of Wisconsin’s ozone season (15 May – 15 Sept) for each year between 1994 and 

2000, which was the final year of NOx sampling at UWMN. 
23

All of Milwaukee-UWMN’s daily urban NOx cycles shown in Figure 16 have much in common. 

The sharp increase in concentrations during the early daylight hours is principally due to the 

injection of fresh NOx emissions from Milwaukee’s morning rush hour traffic. Around 8AM 

there is a steep reduction in NOx. This is due to a combination of increasing atmospheric mixing 

/ pollution dilution at the surface (Lyons, 1975) and the hydroxyl radical (-OH, mostly formed 

via photolysis from oxygenated compounds) beginning to efficiently remove most of the NOx 

(Seinfeld and Pandis, 1998). 

For purposes of studying overall trends in Milw-UWMN’s seven annual NOx profiles in Figure 

16, the first year’s data (1994) and the last year’s data (2000) are highlighted. The 1994 NOx 

levels were predominantly the highest of all the profiled years. Correspondingly, the 2000 

median NOx profile was the lowest for many hours during the diurnal period. 

Figure 17 is similar to Figure 16, but pertains to the hourly NOx measurements collected at 

Milw-DNR SERHQ during 15 May – 15 Sept for each year 1999 – 2008. Similar to UWMN, 

SER’s most recent ozone season (2008) had the lowest NOx measurement series in the graph. 

In summary, Figures 16 and 17 appear to indicate that both Milw-UWMN (1994-2000) and 

Milw-SER (1999-2008) witnessed substantial declines in the average diurnal median hourly 

NOx concentrations between initial and concluding ozone seasons in the sites’ NOx archives. 

Of note is that the SER site measures fairly higher NOx concentrations (peak median value: 

approximately 28 ppb [Figure 17]) than at UWMN (Figure 16, peak median hourly NOx: 23 

ppb). That is probably due, at least partially to the difference in site exposures. The UWMN 

monitor is located on a moderately-traveled arterial street and is adjacent to a residential 

neighborhood. On the other hand, the SER site is exposed to much more motor vehicle traffic 

(and subsequently much more NOx) due to its close proximity to major street arterials and 

interstate highway. 
24
25

4.3 Diurnal Profiles of Hourly VOCs (TNMOCs) 

Figure 18 shows the diurnal profile of median hourly TNMOCs at Milw-SER during the JuneAugust period for each year between 1999 and 2007. [As of this writing (mid-June 2009), the 

TNMOC data for 2008 are still being validated and are currently not available for analysis.] 

Each of the median diurnal hourly TNMOC profiles shows basic features that are similar to those 

for NOx (Figures 16, 17): Maxima occurring approximately during 7-9 AM and 9-11 PM. 

However, the TMNOC fluctuations have less magnitude than for NOx, as well as being less 

coherent among the individual summers. 

Nevertheless, the TNMOC graph exhibits another behavior that is quite similar to those for both 

NOx displays. Namely, the annual median diurnal profile for TNMOCs during the initial year of 

operations (1999) is the highest of all nine years’ data displayed – by far. Correspondingly, the 

most recent year of TNMOC data (2007) is approximately average among the remaining summer 

profiles. The TNMOC curve for 2006 appears to be lowest among all these profiles. 
26
27

4.4 Morning (6-9A CST) VOC and NOx Concentrations 

The diurnal profiles of median hourly NOx (Figures 16 and 17) and TNMOCs (Figure 18) all 

reveal one attribute that is crucial to the formation of ozone. Namely, during the 6-9 AM period 

the precursor levels witness a steep rise to daily peak values, followed by a rapid descent. 

The 6 to 9 AM time span is a critical period for assessing precursor levels which often leads to of 

peak ozone production later in the day (NESCAUM, 1995). Due to morning rush traffic, 

emissions from motor vehicles are high, while photochemical activity is still minimal during 6-

9AM (NESCAUM, 1995). 

Figure 19 presents a time series of monthly median values of daily 6-9 AM CST average 

concentrations of both NOx and hydrocarbons (UWMN: VOCs, SER: TNMOCs) during June, 

July and August at Milw-UWMN (1994-99) and Milw-DNR SERHQ (1999-2007). 

Each site’s separate trends in median 6-9 AM precursor levels have similar characteristics to 

those visible in the median diurnal (24-hour) profiles (Figures 16-18). Namely, both sites 

witnessed substantial, albeit irregular pollution decreases between initial and concluding ozone 

seasons in Figure 19, as follows: 

• UWMN NOx 1994: 28.9 ppb 1999: 12.8 ppb (55.7% decrease from 1994) 

• UWMN VOC 1994: 151.7 ppbC 1999: 68.5 ppbC (54.8% decrease from 1994) 

• SER NOx 1999: 24.8 ppb 2007: 15.3 ppb (38.3% decrease from 1999) 

• SER TNMOC 1999: 105 ppbC 2007: 80.2 ppbC (23.6% decrease from 1999) 
28
29

4.5 Morning (6-9A CST) VOC / NOx Ratios in Milwaukee 

The relation between ozone, NOx and VOC is driven by complex nonlinear photochemistry. As 

noted in Section 4.1 of the Attainment Demonstration - the availability of VOCs and NOx in the 

morning along with their differing rates of reaction with the -OH radical can greatly influence 

how much ozone is formed for a given site-day (Seinfeld and Pandis, 1998). 

The reader is referred to Appendix E (“Overview: VOC / NOx Ratios and Ozone Production“) to 

get some background on the basics of the ozone science of VOC / NOx ratios that is part of the 

discussion in this section. 

The morning (6-9 AM CST) VOC and NOx levels for Milw-UWMN (1994-99) and Milw-SER 

(1999-2007) that were used to construct Figure 19 have also been employed to derive the median 

monthly ratios of these 2 metrics (Figure 20). As expected for both of these very urbanized 

monitoring sites, the VOC / NOx ratios are almost consistently quite low (i.e., less than 6.4, save 

for the 1998 UWMN exception [7.7]). 

This indicates that both sites are exposed to relatively sizable NOx levels and subsequently are 

within air masses defined as VOC-sensitive (Appendix E). Consequently, the areas around both 

sites would be expected to achieve lower ozone levels more efficiently through VOC emission 

controls (Appendix E). 

As is demonstrated in Chapter 5 regarding ozone reduction strategies – the WDNR has 

emphasized VOC controls in the urban areas of the ozone nonattainment counties. Conversely, 

in Wisconsin’s more rural ozone nonattainment counties (e.g., Sheboygan, Manitowoc) that have 

relatively higher amounts of VOCs, lower NOx and higher VOC / NOx ratios – these “NOxsensitive” counties are being targeted for more NOx controls to effectively reduce ozone 

concentrations (Appendix E). 
30
31

5 Emission Inventories and Implemented Control Measures 

5.1 Introduction 

Chapter 3 details the trends that show there have been substantial reductions in ambient ozone 

levels throughout eastern Wisconsin’s ozone nonattainment areas over the past 15-20 years. This 

achievement culminated in 2008 with all of Wisconsin’s ozone sites having 8-hour ozone design 

values for the 2006-08 period that are below the 1997 8-hour ozone NAAQS. Year 2008 is the 

first year for which there are no Wisconsin ozone monitoring sites with design values exceeding 

an ozone NAAQS since the 1970s. Chapter 4 shows the considerable decrease in ambient ozone 

precursor concentrations (VOCs, NOx) during the past 10-15 years in Milwaukee. 

A major element of this ozone attainment demonstration is to substantiate that the abovedescribed improvements in ozone air quality are due to sizable reductions in VOC and NOx 

emissions that result from implementing permanent and enforceable emission control measures 

(WDNR, 2009). In order to meet this objective the WDNR needs to detail these emission 

changes during critical time periods. The US EPA (2005c) states that it is necessary to develop 

several inventories in order to demonstrate compliance with the 8-hour ozone NAAQS, These 

inventories are for the base year, and measuring reasonable further progress in emission 

reductions and for modeling ozone levels. 

The remaining sections in this chapter provide an overview of 1) control strategies implemented 

in Wisconsin to reduce ozone precursor emissions, and 2) how the various emissions inventories 

of ozone precursors used in this attainment demonstration were developed for the 9 Wisconsin 

ozone nonattainment counties. 

5.2 Wisconsin Control Strategies for Ozone Precursor Emissions 

As stated in the Redesignation Guidance, in order for a state to have an approvable ozone SIP, it 

must meet all requirements established in Section 110 and Part D of the federal Clean Air Act 

that were applicable prior to submittal of a complete redesignation request. Wisconsin has met 

these requirements, excluding the following: 

1. 1997 8-Hour Ozone NAAQS Attainment Demonstration 

2. 1997 8-Hour Ozone NAAQS Reasonably Further Progress (RFP) Demonstration 

3. A U.S. EPA approved NOx RACT Rule 

4. All outstanding CTGs, as part of VOC RACT requirements, prior to 2008. 

On March 17, 2008, U.S. EPA issued findings that the Milwaukee-Racine 6-County Area and 

Sheboygan County missed CAA deadlines for submitting these elements of the state’s 1997 

Ozone NAAQS SIP (73 FR 15416). WDNR plans to submit the required documents for the four 

SIP elements listed above prior to, or concurrently with, submittal of this redesignation request. 
32

Excluding these 1997 Ozone NAAQS SIP elements, Wisconsin’s Ozone Control SIP is fully 

approved and contains all federally required emission control programs related to ozone. 

The following subsections form a bulleted version of the emissions regulatory analysis portion of 

the WDNR (2009) document that requests redesignating Wisconsin’s nine counties from 

nonattainment to attainment for the 1997 ozone NAAQS. A chronological listing of the 

administrative rules adopted by the WDNR that are designed to help lower ozone levels is 

contained in Appendix F. 

5.2.1 VOC Reasonably Available Control Technology (RACT) 

Section 182(b)(2) of the 1990 CAA requires states with moderate nonattainment areas to 

implement RACT under section 172(c)(1) with respect to each of the following: 

• Each category of VOC sources in the ozone nonattainment area covered by a US EPA 

control technique guideline (CTG) document issued between the date of the enactment of 

the 1990 CAA and the date of attainment. 

• All VOC sources in the area covered by any CTG issued before the enactment date of the 

1990 Clean Air Act 

• All other major stationary VOC sources that are located in ozone nonattainment areas. 

• As a part of its SIP The WDNR has adopted and implemented administrative rules 

requiring all existing major stationary sources of VOCs at the 25 ton-per-year level in the 

Milwaukee-Racine 6-County ozone nonattainment area and Sheboygan County to meet 

VOC RACT. Excluded here are those VOC RACT rules for which there are no identified 

sources in Wisconsin ozone nonattainment areas. 

• Maximum Achievable Control Technology (MACT). Wisconsin has adopted MACT 

rules further controlling air toxics, which include many VOCs, from major sources 

throughout the state. 

All of the above-listed Wisconsin administrative rules and federal regulations collectively 

comprise a comprehensive VOC emissions control program covering all high-emitting stationary 

sources of VOC in the ozone nonattainment areas. Consequently, the WDNR has determined that 

all of these VOC RACT requirements combine to meet the VOC RACT mandate of Subpart 2 of 

the federal Clean Air Act. 

VOC RACT rules have been very successful in reducing emissions over the past decades as 

indicated in Table 2. Note that VOCs and reactive organic gases (ROGs) are nearly identical in 

definition and photochemical function. ROG excludes chlorofluorocarbons (CFCs) and 

hydrochlorofluorocarbons (HCFCs). 
33

Table 2: Emissions of Reactive Organic Gases 

in 9-County Area 1985 & 2005 

County 1985 ROG 

(tons) 

2005 ROG 

(tons) 

1985-2005 

Percent 

Decrease 

(%) 

Door 214.23 105.65 50.7 

Kenosha 840.19 534.97 36.3 

Manitowoc 470.24 559.20 -18.9 

Milwaukee 10,728.51 2,143.25 80.0 

Ozaukee 283.69 156.24 44.9 

Racine 1,235.84 448.89 63.7 

Sheboygan 1,244.94 908.28 27.0 

Washington 619.00 222.00 64.1 

Waukesha 1,647.31 1,147.63 30.3 

Totals 17,283.95 6,226.11 64.0 

Source: http://dnr.wi.gov/air/emission/historical_emissions/historical_emissions_rog.htm 

Table 2 shows that ROG emissions in the Milwaukee-Racine 6-County Area and the counties of 

Door, Manitowoc, and Sheboygan have declined by 64% in total between 1985 and 2005. 

5.2.2 NOx RACT 

Beginning in 2001the WDNR established specific NOx controls (Wis. Admin. Code chapter NR 

428) as part of the progress plans setting formal maximum NOx budgets within Wisconsin's SIP. 

In 2006, the WDNR started rule making proceedings to implement NOx RACT requirements on 

major sources in the Milwaukee-Racine 6-County ozone nonattainment area. The emission 

requirements apply to individual stationary combustion units at major sources with a compliance 

date of May 1, 2009. The proposed RACT rule is estimated to achieve reductions of over 29,000 

tons per year of NOx emissions from 2002 emission levels. 

The WDNR is currently updating chapter NR 428 to comply with NOx RACT requirements. It 

is anticipated that the rule will be adopted by spring 2009 and submitted to the U.S. EPA for 

approval in the summer of 2009. 

Of important note is that Wisconsin was removed from US EPA’s original list of 22 states which 

are required to comply with the Agency’s NOx SIP Call. This NOx SIP call requires statewide 

reductions in NOx emissions from electric utility boilers, cement kilns, large industrial boilers, 

and stationary internal combustion. 
34

5.2.3 Non-Motor Vehicle Ozone Control Measures in Addition to Clean Air Act Requirements 

In anticipation of the need for additional reductions beyond the Clean Air Act requirements, The 

WDNR has worked with many groups, both governmental and non-governmental, to identify and 

implement additional control measures that can help reduce emissions of ozone precursors. 

These additional non-voluntary control measures include: 

• NOx SIP Call: To address the ozone transport problem, U.S. EPA finalized rulemaking in 

September 1998 requiring 22 states to reduce NOx emissions within each state to a level 

consistent with a NOx emissions budget identified in the final rule (63 FR 57356). 

• Tier 2 Emission Standards for Vehicles and Gasoline Sulfur Standards: A U.S. EPA 

regulation to significantly reduce emissions from cars, light trucks, including sport utility 

vehicles (SUVs) nationally. 

• Ultra-low Sulfur Diesel Requirements for Highway Vehicles: Oil refiners must produce 

diesel fuel for use in highway vehicles with a sulfur content of no more than 15 ppm. 

• Clean Air Non-road Diesel Rule: This US EPA nationwide regulation requires stringent 

pollution controls on diesel engines used in industries such as construction, agriculture, 

and mining that will result in a reduction in NOx emissions. In addition, beginning in 

2007, sulfur levels in non-road diesel fuels were reduced by 99 percent from current 

levels (from approximately 3,000 ppm now to 15 ppm in 2010. 

• Mobile Sources Air Toxics Rule: This U.S. EPA regulation reduces hazardous air 

pollutants from mobile sources. These new standards will have a co-benefit of reducing 

VOC emissions. 

• Maximum Achievable Control Technology (MACT) Standards: Using a technology 

based approach, the U.S. EPA has developed standards for controlling emissions of air 

toxics, which includes VOCs, from each major type of facility within an industry group. 

• Stationary Source NOx Control Program (Wis. Adm. Code NR 428): NR 428 addresses 

stationary source NOx emissions and is structured to meet Rate of progress (ROP) NOx 

emission reduction requirements for larger existing sources and establishes emissions 

standards for new sources through 2007. The program encompasses the seven southeast 

counties of Kenosha, Milwaukee, Ozaukee, Racine, Sheboygan, Washington, and 

Waukesha. 

• The Stationary Source NOx control program consists of two basic elements: 1) ozone 

season emission limits for electric utility systems comprised of boilers equal to or greater 

than 500 mmbtu/hr; and 2) Unit-specific requirements of either emission rate limits or 

combustion optimization for other large emission sources. 

• Clean Air Interstate Rule (CAIR) (Wis. Adm. Code NR 432): NR 432 applies to all major 

electric generating units in Wisconsin and in upwind states. Nationwide, CAIR results in 
35

a reduction of NOx emissions by 53% by 2009 and 63% by 2015. On December 23, 

2008, the D.C. Circuit Court decided to remand, rather than vacate, the CAIR rule, thus 

leaving CAIR in place while EPA revises the rule. Due to the ongoing litigation 

involving CAIR, all potential emission reductions resulting from CAIR have been left out 

of the emission projections. 

• Wisconsin’s mercury control regulation with the multi-pollutant compliance option is 

expected to significantly reduce NOx emissions in Wisconsin from electric generating 

units. 

• Side Benefits of Control of Hazardous Pollutants (Wis. Adm. Code NR 445): NR 445 

applies to all stationary air contaminant sources, which may emit hazardous 

contaminants, which also includes VOCs. 

• Clean Diesel Grant Programs: There have been various programs in Wisconsin to fund 

diesel emission reduction programs. Funding has been provided by CMAQ, DERA, 

ARRA, various other EPA grants, the Wisconsin Legislature and individual donations. 

Substantial emission reductions have been achieved in the diesel fleet as a result of these 

efforts. 

5.2.4 Traffic Reduction Measures 

The WDNR has partnered with other governmental units and private organizations on programs 

to help reduce motor vehicle traffic, particularly in the heavily populated southeastern portion of 

the State. These voluntary local controls will reduce idling times of motor vehicles and thus 

reduce NOx emissions. The state does not commit to continuing these voluntary programs. 

These programs, which will include the benefit of helping to lower VOC and NOx emissions are 

as follows: 

• Local Controls of Traffic Congestion: The Milwaukee-Racine 6-County Area has 

implemented local controls to decrease the traffic congestion in the city. 

• Commuter Value Pass (CVP) & UPASS programs: The CVP transit agency program 

offers discounted transit passes through large employers, providing a shared cost program 

between employer and employee. 

• Rideshare: A Wisconsin Department of Transportation interactive web-based ride 

matching service. 

• Advanced Traveler Information Systems: Real-time data from traffic condition cameras 

is used to provide traveler information to the media and motorists. 

• Ramp Metering and High-Occupancy Vehicle Priority: Located on freeway entrance 

ramps to control the rate of entry and encourage ridesharing and transit use. 
36

• Park & Rides: A system of park and ride facilities throughout the area designed for 

meeting transit and carpools. 

• Van Pool (State and MCTS): The State Vanpool provides alternative transportation for 

commuting to Madison from the Milwaukee area. 

• Education/Marketing Promotion: Wisconsin Partners for Clean Air voluntary coalition 

promoting emission reductions along with an Air Quality Watch & Advisory Program 

alerting the public to air quality conditions and promoting transportation alternatives. 

5.2.5 Controls to Remain in Effect 

Wisconsin intends to maintain the non-voluntary control measures listed in 5.22 and 5.2.3. 

Wisconsin also expects that voluntary programs such as those listed above will continue to 

provide emission reductions into the future, but there is no commitment to continue those 

specific programs. 

5.3 RFP Emissions Inventories (EIs): Base 2002 and Projected 2008 

Section 182 of the federal Clean Air Act requires states with ozone nonattainment areas 

classified as moderate or higher must submit plans that show reasonable further progress (RFP) 

towards attaining the NAAQS. The Phase 2 Ozone Implementation Rule (US EPA 2005b) 

defines RFP towards attaining the 1997 8-hr ozone NAAQS for moderate nonattainment areas 

(e.g, the 9 ozone nonattainment counties in Wisconsin) as demonstrating that there has been at 

least a 15% emission reduction between the base year (2002) and the attainment year (2008). The 

15% reduction requirement can be satisfied with any combination of VOC and NO reductions. 

Additional reductions are also required to achieve attainment beyond 2008. 
37

5.3.1 2002 Base Year Emissions Inventory for RFP 

The base year (2002) portion of the RFP requirement is a compilation of all anthropogenic 

sources of VOC and NOx for an average summer weekday in 2002, including all control 

programs in place at that time. The US EPA (2005b, 2005c) has ruled that the 2002 baseline RFP 

EI is identical to the 2002 base year EI. 

The WDNR followed EPA’s requirements and guidance and prepared a comprehensive 

statewide EI of VOC and NOx emissions for year 2002 (WDNR 2009). The 2002 area source 

emissions were back-calculated from the 2005 emissions that were estimated with current 

methodologies. The 2002 inventory includes point, mobile, and area sources. A succinct 

description of the methods and data bases used to develop this EI appears below: 

• Point Source EI - The method used to develop the comprehensive 2002 non-Electric 

Generating Unit (non-EGU) point source EI is contained in Appendix 4 of WDNR’s 

(2009) Request for Redesignation to Ozone Attainment. The method used to develop the 

2002 EGU point source EI that incorporates US EPA’s Clean Air Markets Division data 

is described in Appendix 5 of WDNR’s (2009) Request for Redesignation to Ozone 

Attainment. 

• Area Source EI - The 2002 area source EI was derived from the Wisconsin 2005 Base 

Year EI submitted to U.S. EPA in June 2007. The back calculation was performed to 

maintain consistency between the 8-Hr Ozone Redesigination Request and Maintenance 

Plan EIs and the RFP EIs. The Redesignation EIs used a base year of 2005. These 

emission estimates were made based on various activity data compiled by, but not limited 

to, the U.S. Census Bureau, the U.S. Energy Information Administration, U.S. Bureau of 

Economic Analysis and several Wisconsin State agencies. A description of the methods 

followed to develop the 2002 area source EI is included in Appendix 4 of the WDNR 

(2009) Request for Redesignation to Ozone Attainment. Appendix 7 in the redesignation 

request contains area source emissions by county and SCC. 

• Non-road EI – The non-road emission estimates were prepared by using the U.S. EPA 

(2005) National Mobile Inventory (NMIM) model. The contractor Pechan, provided 

marine and rail emission estimates via LADCo for Wisconsin in 2002. Aircraft 

emissions were calculated using the Federal Aviation Administration’s Emissions and 

Dispersion Modeling System (EDMS). 

• On-road EI - 2002 mobile source emissions were calculated using the mobile sources 

emissions model called MOBILE 6.2. All emission estimates were made in accordance 

with MOBILE 6.2’s user’s guide (US EPA 2003) and technical guidance (US EPA 

2004). 

• Biogenic emissions were not included. 

Following these methods, the WDNR constructed a statewide base year 2002 EI for NOx and 

VOCs. From this EI, the emissions for Wisconsin’s nine ozone nonattainment counties were 
38

identified and separated for inclusion here. Tables 3 includes a summary for each of the 9 

counties – its base year “actual” 2002 county-wide emissions (units: average summer day) for 

both for NOx and VOCs. Tables 4 (NOx) and 5 (VOCs) provide more detail by separating the 

emissions totals into five EI source sectors: on-road, non-road, commercial 

marine/aircraft/railroad (MAR), point and area/nonpoint. 

As the year 2002 NOx portion of Table 4 indicates, the largest base year NOx emission source 

categories are point and on-road. As expected, Milwaukee County had the highest NOx 

emissions totals in 2002. 

Area and non-road sources account for the largest totals of the base year VOC emissions (Table 

5). Emissions of VOCs are highest in Milwaukee County followed by Waukesha County. 
39
40

5.3.2 Adjusted Base Year 2002 Emissions Inventory (EI) for RFP 

In order to demonstrate RFP, a nonattainment area must show that its projected attainment year 

(2008) EIs of NOx and VOCs will be less than or equal to the required or targeted emission 

levels set for the end of the RFP period, (i.e., for moderate ozone nonattainment areas - the 

attainment year 2008). The US EPA (2005b) requires that for moderate ozone nonattainment 

areas – the target is a 15% reduction in combined VOC and NOx emissions between the base 

year 2002 and the projected attainment year (2008). 

The US EPA also requires that – prior to determining if RFP is achieved – the base year 2002 

emissions (Section 5.3.1) must be adjusted to exclude emission reductions from two noncreditable programs: 1) the Federal Motor Vehicle Control Program (FMVCP) tailpipe and 

evaporative standards applicable as of January 1, 1990; and 2) Federal regulations limiting the 

Reid Vapor Pressure (RVP) of gasoline in ozone nonattainment areas applicable June 15, 1990. 

Following US EPA supplemental guidance, the Department can assume the gasoline to have an 

RVP of 9.0 pounds per square inch (psi). The post-1990 RACT "fix-up" requirements are met 

previously and surpassed with the implementation of RACT statewide as required by CAA 

Section 184(b)(1)(B). Therefore, the adjustment for this in 2002 was zero. 

These modifications to the base year 2002 inventory are reflected in the VOC and NOx data 

columns of Table 3 labeled “2002 RFP Adjusted” for each of Wisconsin’s ozone nonattainment 

counties(units: average summer day). 

5.3.3 2008 Projected Emissions Inventory (EI) for RFP 

The next step in evaluating RFP is to compile a projected 2008 RFP inventory from the 2002 

base year inventory (Section 5.3.1) by applying appropriate growth factors and the impact of 

post-2002 control strategies (Section 5.2) to each source category. Of note is that the 2008 EGU 

point emissions are actual rather than projected emissions. A summary of what calculations 

went into deriving the 2008 RFP emissions inventory is contained in Table 6. 

The US EPA’s RFP method specifies that the required 15% RFP reduction can come from any 

combination of VOC and NOx reductions occurring between 2002 and 2008. Reductions of 

35.0% in NOx emissions and 14.7% in VOC accrued between 2002 and 2008 collectively for the 

9 ozone nonattainment counties (Table 3). This indicates that the promulgation, implementation 

and enforcement of the control strategies discussed in Section 5.2 have been successful. 
41

 
42

5.4 Base and Future Year Inventories for the Modeled Attainment Test 

The US EPA (2007) requires the use of a modeled attainment test (MAT) to help determine if a 

region has attained the 1997 8-hour NAAQS. The MAT, which is discussed in more detail in 

Chapter 6, is a method to estimate future (attainment) year 2008 eight-hour ozone design values 

(DVs) by applying proportionality ratios based on modeled ozone predictions (i.e., future year / 

base year values) to averages of the measured 8-hour ozone DVs centered on the base year (US 

EPA 2007). If the MAT-derived future estimates of ozone concentrations are less than 85 ppb, 

then this element of the attainment test is satisfied. 

LADCO (2008, [Appendix A]) conducted the photochemical grid modeling that formed the basis 

for the MAT for ozone nonattainment areas in the upper Midwest including Wisconsin and 

Illinois (IEPA 2009). LADCO employed the base year emissions inventories for both 2002 and 

2005 in the ozone modeling (Appendix A). The US EPA (2007) modeling guidance 

recommends using 2002 as the baseline inventory year, but also allows for use of an alternative 

baseline inventory year, especially a more recent year. 

The regional ozone concentrations in both 2002 and 2005 were above normal (LADCO 2008, 

[Appendix A]) with 2002 having higher values compared to 2005. Examination of multiple base 

years provides for a more complete technical assessment. Both sets of model runs are discussed 

in Appendix A. 

Since the base-year 2005 represented more recent air quality data, there were several inventory 

improvements to the 2005 base-year and 2005 was after implementation of the NOx SIP call, 

the WDNR decided to use Base Case M 2005 (LADCO TSD [Appendix A] as the base year for 

ozone predictions). 

Tabular data and graphical information of base year emissions are provided in Section 3.6 

(“Model Inputs: Emissions”) of Appendix A. Additional detail on the inventories can be found in 

the Appendix B (“Base K/Round 4 [2002] Strategy Modeling Emissions” [LADCO, May 16, 

2006]), and Appendix C (“Base M [2005] Strategy Modeling: Emissions (Revised)” [LADCO, 

February 27, 2008]). 

The methods used to build the emissions inventory for base year 2005 were similar to those 

employed in constructing the base year 2002 inventory for RFP (Section 5.3.1). The inventories 

were compiled for point, area, on-road mobile, and non-road, emission categories for NOx, and 

VOCs. Inventories were prepared directly from the statewide database or generated from 

approved emissions models (i.e. EGUs, on-road, non-road, etc..). 

The methods used to project the emissions inventory for future year 2008 for ozone modeling 

from the base year 2005 EI were similar to those employed in constructing the future year 2008 

inventory for RFP (Section 5.3.3) 

Throughout the inventory development process, LADCO and member states implemented 

quality assurance procedures and quality control checks to assure inventories of the highest 

quality. Procedures outlined in U.S. EPA guidance pertaining to inventory quality assurance 

were followed, yielding complete, accurate inventories. 
43

6 Ozone Attainment Demonstration Modeling 

6.1 Introduction 

States seeking to demonstrate attainment with the ozone NAAQS need to assess whether the 

emission control measures are truly sufficient to confirm attainment of the ozone NAAQS, as 

well as maintain this attainment. The US EPA (2007) requires that this assessment be completed 

by conducting a modeled attainment demonstration of the nonattainment area(s) in question. The 

US EPA further states that a modeled attainment demonstration can consist of analyses 

[including computer simulations] which estimate whether selected emissions reductions will 

result in ambient concentrations that meet the NAAQS. 

As noted in Chapter 5 LADCo (Appendix A) conducted a comprehensive ozone modeling 

program for the upper Midwest, including Wisconsin. This modeling exercise serves to provide 

predicted ozone concentrations (base year and future year) to evaluate whether the emissions 

reductions have resulted in attainment by the required attainment year of 2008. 

Chapter 6 provides a succinct overview of the various components to this ozone modeling 

project along with its predicted ozone results that pertinent to Wisconsin. The information in the 

following sections is derived largely from that portion of the LADCo (2008) modeling 

documentation that focuses exclusively on photochemical modeling. The modeling project was 

run in accordance with guidelines established by the US EPA (2007). 

6.2 Modeled Years and Emission Scenarios 

LADCo conducted photochemical grid modeling for several base and future year emissions 

scenarios. As noted in Chapter 5, the WDNR is using the predicted results in its modeling 

demonstration which are derived, in part from photochemical modeling scenarios (i.e., 

emissions, ambient air quality, meteorology) for base year 2005 (referred to a Base M in 

Appendices A and C). 

Modeling for attainment year 2008 included an inventory that was appropriately adjusted to 2008 

from the base year 2005. The details on how both the base and projected attainment year 

inventories were compiled are contained in Appendices A and C. LADCo (Appendix A) also 

constructed EIs for several projected attainment and maintenance years (2012, 2018). 

6.3 Modeling System 

LADCO (2008 [Appendix A]) indicates that “the air quality analyses were conducted with the 

CAMx model, with emissions and meteorology generated using EMS (and CONCEPT) and 

MM5, respectively. The selection of CAMx as the primary model was based on several factors: 

Performance, operator considerations (e.g., ease of application and resource requirements), 

technical support and documentation, model extensions (e.g., 2-way nested grids, process 

analysis, source apportionment, and plume-in-grid, and model science).” 
44

The Wis DNR and the air quality agencies from the states of Indiana, Michigan, Ohio, and 

Illinois worked cooperatively with LADCO to refine the CAMx photochemical model to 

simulate the formation and transport of ozone in the Midwest. The modeling system was used to 

evaluate emissions reduction strategies for inclusion in the states’ attainment plans. A complete 

description of the modeling methodologies and results are contained in the LADCo documents 

included as Appendices A and D. 

The modeling study included emissions, meteorological, and ozone simulations using a nested 

36/12/4 km grid covering the central U.S. and centered on the Lake Michigan region. The air 

quality analyses were conducted using the CAMx model, with emissions and meteorology 

generated using EMS (and CONCEPT) and MM5, respectively. 

6.4 Modeling Performance Evaluation 

As described in Section 3.7 of the LADCO Technical Support Document (Appendix A), model 

performance was assessed by comparing modeled and monitored concentrations with statistical 

measures recommended by U.S. EPA to assess the reasonableness of the results. The model 

performance evaluation focused on the magnitude, spatial pattern, and temporal variations of 

modeled and measured concentrations. 

The 2002 and 2005 baseline CAMx and CMAQ modeling databases were evaluated against 

monitored ozone data from the lower Lake Michigan and Detroit-Cleveland area in order to 

evaluate the fitness of the databases for use in the modeled attainment test. In summary, model 

performance for ozone is generally acceptable and can be characterized as follows: 

• Good agreement between modeled and monitored concentrations for higher concentration 

levels (> 60 ppb) – i.e., bias within 30%; 

• Regional modeled concentrations appear to be underestimated in the 2002 base year, but 

show better agreement (with monitored data) in the 2005 base year due to model and 

inventory improvements; 

• Day-to-day and hour-to-hour variation in and spatial patterns of modeled concentrations 

were consistent with monitored data; 

• The model accurately simulated the change in monitored ozone concentrations due to 

reductions in precursor emissions. 

6.5 Modeled Attainment Test Results 

 

After detailed performance testing of the 2002 and 2005 base case simulations, the CAMx 

modeling system was exercised with “On-the-Books” (OTB) emissions control scenarios for 

both 2008 and 2009 (Appendix A). These scenarios aimed at assessing the effects of future year 

emission control strategies on ozone in the Midwest. 
45

As described in Section 4.0 of Appendix A, air quality modeling and other supplemental 

analyses performed to estimate future year ozone concentrations indicated that: 

• Existing (OTB) controls are expected to continue producing significant improvement in 

ozone air quality. 

• Attainment by the applicable attainment date is dependent on actual future year 

meteorology (e.g., if weather conditions are similar to [or less severe than] 2005, then 

attainment is likely). 

The US EPA (2007) requires the use of a modeled attainment test (MAT) which is described as a 

procedure in which an air quality model (e.g., CAMx) is used to simulate current and future 

ozone air quality. If future ozone predictions, as derived from the MAT, are below the 1997 8-hr 

ozone NAAQS (84 ppb) then this element of the attainment test is satisfied. 

In a MAT, model estimates are used in a “relative” rather than “absolute” sense. These ratios are 

called “relative reduction factors” (RRF). Future 8-hr ozone design value concentrations are 

estimated at existing monitoring sites by multiplying modeled RRF at locations “near” each 

monitor by the observation-based monitor-specific baseline (2005) ozone design value: 

RRF = ratio: modeling cell specific future / baseline (i.e.,“Base M”, 2005) modeling results. 

According to LADCo (2008, Appendix A) the predicted ozone results were provided for those 

grid cells with ozone monitors. The RRF calculation considers all nearby grid cells (i.e., 3x3 for 

12 km modeling) and a threshold of 85 ppb. If there were less than 10 days above this value, 

then the threshold was lowered until either there were 10 days or the threshold reached 70 ppb. 

RRF represents predicted percent change in a site’s ozone between the base year (2005) and 

future year (attainment year 2008, maintenance years 2009, 2012, 2018). 

The next step is to calculate the site-specific base year design values (DVBaseline, units: ppb). 

For ozone DVBaselines were derived by averaging the site’s three 3-year periods centered on the 

emissions base year (i.e: for 2005 base year: 2003-2005, 2004-2006 and 2005-2007). 

Next - calculate future year design values: For each grid cell (with a monitor), the RRFs are 

multiplied by the base year design values to project the future year values. 

DVFuture (ppb) = DVBaseline X RRF 

Finally, in order to assess whether or not the site is predicted to achieve attainment, the 

DVFuture values are compared to the 8-hour O3 NAAQS (84 ppb). 

Table 7 displays the baseline (2002-centered) 8-hr ozone design values and the subsequentlyderived RRFs and modeled attainment test (MAT) results for 7 ozone monitoring sites that are 

located in Wisconsin’s ozone nonattainment areas (Figure 1). For the year 2008 attainment 

scenario, the modeled attainment test shows attainment of the 1997 eight-hour ozone NAAQS 

for all seven sites. 
46

Of note is that the MAT-predicted 2008 DVs for Newport (84.8 ppb) and Sheboygan (84.4 ppb) 

are quite close to being nonattainment (85 ppb). However, Table 7 also shows that successive 

MAT results for future maintenance years (2009, 2012, 2018) indicate progressively lower future 

years’ 8-hr ozone DVs for these sites. Furthermore, the MAT predict that ozone NAAQS 

attainment will be achieved in 2008 and 2009 with no additional emission control regulations. 

Namely that the current “On the Books” control strategies only were included in constructing 

the 2008 and 2009 emissions data bases for modeling (LADCo, 2008 [appendix A to this 

Attainment Demonstration]). 
47
48

7 Additional Data Analyses 

As noted in section 3.1 the US EPA (2007) recommends that supplemental analyses should 

accompany all model attainment demonstrations. Included in this assessment are two 

supplementary analyses that help evaluate progress on improving ozone air quality in 

southeastern Wisconsin during the past 10-15 years. 

7.1 CART analyses 

The first study was LADCo applying a binary recursive partitioning method called the 

Classification And Regression Tree (CART) analysis to ozone and meteorology data for selected 

ozone monitors in the upper Midwest (Kenski, 2009). These sites have 8-hour ozone design 

values which have historically been close to or exceeded the NAAQS. The reader is referred to 

Appendix G for a brief technical overview of the CART model. 

The purpose of this CART analysis was to assess ozone trends, using the CART bins as 

meteorologically adjusted results (Kenski, 2009). 

The focus of the CART analyses presented here are on the collective ozone monitors (total: 5) 

along the Wisconsin’s coastline with Lake Michigan and Milwaukee’s 3 ozone monitors. Only 

monitors with continuous records for the 1995-2007 period were included in this analysis. For 

each individual monitor, regression trees were developed that classify each summer day (MaySeptember) by its meteorological conditions (Kenski, 2009). Similar days are assigned to nodes, 

which are equivalent to branches of the regression tree. 

The results of these CART analyses are displayed in Figures 21 (5 “Wisconsin Shoreline 

Monitors”) and 22 (3 “Milwaukee” ozone sites). Both displays clearly show that CART’s 

objective analysis of the pertinent factors to ozone formation for the years 1995 to 2007 yield 

trend lines that show a steady decline in ozone concentrations through this period – and 

extrapolated into 2009. 

The results from this alternative analysis method (CART) helps corroborate that the trends in 

measured ozone (Chapter 3) have been moving noticeably downward over the past 10-20 years, 

culminating in all Wisconsin sites having 8-hour ozone design values below the 1997 ozone 

NAAQS for the current 2006-08 period. 
49

Figure 21 
50

Figure 22 
51

7.2 NOx and VOC Concentrations vs Wind Direction 

The second supplemental analysis involves data pairs of hourly-averaged 1) NOx and VOC 

concentrations collected at the Milwaukee SER site and 2) wind direction data collected at the 

Milwaukee Mitchell Field Airport NWS (MKE) site during June-Aug of the year when ozone 

precursor monitoring commenced at Milw-SER (1999) and the most recent year for which both 

VOC and NOx data are available (2007). This analysis would offer an understanding how 

summertime wind-dependent NOx and VOC levels varied between 1999 and 2007. 

The hourly NOx and VOC data were averaged across 36 separate bins of wind direction - 10 

compass degrees - for 1999 and 2007. The NOx vs wind and VOC vs. wind direction are 

displayed in Figures 23 and 24 respectively. 

These graphs both show a similar profile. Namely that the highest concentrations are strongly 

associated with winds that have a sizable south-southeasterly to southwesterly orientation (i.e., 

160 – 270 degrees, compass direction). This is consistent with the general wind-high ozone 

characteristics discussed in Chapter 2. 

The graphs also show that for both NOx (Figure 23) and VOCs (Figure 24) - there has been a 

sizable decline in pollutant levels across much of wind direction spectrum between 1999 and 

2007 at Milw-SER. More significantly, the largest decreases have been across those wind 

sectors described above as being associated with the highest pollutant levels. Figures 23 and 24 

help corroborate the findings identified in the NOx and VOC median diurnal profiles (Figures 

17, 18) that there has been a sizable reduction in the ambient levels of both pollutants between 

1999 and 2007 at Milwaukee-SER. 
52
53

8 Summary and Conclusions. 

The nine counties in eastern Wisconsin that are currently classified as nonattainment of the 1997 

eight-hour ozone NAAQS (Figure 1) have had a long history of being witness to excessively 

high ozone. Southeastern Wisconsin was first classified nonattainment for the 1-hour ozone 

NAAQS in 1979. 

As noted in Chapter 2 these counties are part of the Lake Michigan basin, which is a heavily 

industrialized and populated region. The region’s considerable amount of ozone precursor 

emissions have often combined with the unique ozone-conducive meteorology of the region 

(Chapter 2) to yield widespread high ozone throughout the basin with most of the coastal 

counties having been nonattainment for ozone NAAQS at one time or another for many years 

(Figure 2). 

Nevertheless, Wisconsin has had an aggressive plan to enact permanent, enforceable rules and 

regulations during the past three decades in order to help significantly reduce the emissions of 

VOC and NOx that contribute to the production of ozone in these nonattainment counties 

(Chapter 5). These efforts have resulted in a substantial decline in ambient levels of both ozone 

(Chapter 3) and ozone precursors (Chapter 4, Section 7.2) over the past 10-20 years. 

The decrease in Wisconsin’s ozone levels achieved a milestone in 2008, when all of the State’s 

ozone sites derived 8-hour design values that are below the 1997 8-hr ozone NAAQS. Indeed, 

there were no exceedances of the 1997 eight-hour ozone NAAQS anywhere in Wisconsin during 

2008 (Figure 7). This achievement has not been realized in Wisconsin in at least 30 years. 

As part of this attainment demonstration analysis The WDNR submitted to two US EPArequired tests to help evaluate whether the regulatory actions implemented and enforced have 

yielded attainment of the 1997 8-hour ozone NAAQS in the nine Wisconsin nonattainment 

counties. 

The first test is to determine if the implementation and enforcement of the control strategy rules 

in the 9 counties has yielded a reduction in overall VOC and NOx emissions between base year 

(2002) and attainment year (2008) that constitutes reasonable further progress (“RFP”: at least a 

15% reduction combined for both pollutants between the 2 years) (US EPA 2007). 

Section 5.2 details this emissions accounting which demonstrates that Wisconsin’s emission 

control strategies are estimated to reduce NOx and VOC emissions between 2002 and 2008 in 

the 9 nonattainment counties by 35% and 14.7%, respectively (Table 3). These estimates easily 

exceed the required 15% RFP requirement. 

The second attainment demonstration measure is employing the modeling attainment test (MAT) 

(US EPA 2007). The MAT pertains to using predicted ozone concentrations to derive a 

proportional change (i.e., relative reduction factor [RRF]) in future (i.e., 2008) eight-hour ozone 

design values, relative to the measured 8-hour ozone design values (centered on 2002). 
54

Chapter 6 details the WDNR use of the MAT with predicted ozone concentrations calculated for 

the base year (2005) and attainment year (2008) modeling scenarios. The MAT results, which 

are summarized in Table 7, indicate that the seven ozone sites with the highest ozone design 

values in Wisconsin’s ozone nonattainment counties are predicted to attain the ozone standard by 

the attainment year (2008). Furthermore, applying the MAT to predicted ozone concentrations 

from modeling runs for modeling scenarios 2009, 2012 and 2018 show that these sites are 

predicted to maintain attainment for these future years (Table 7). 

LADCo’s application of the Classification And Regression Tree (CART) objective analysis 

model to ozone and meteorology data for selected ozone monitors in Wisconsin during 1995-

2007 clearly yield trend lines that show a steady decline in ozone concentrations at these through 

this period – and extrapolated into 2009 (Figures 21, 22). 

Graphical displays of both NOx and VOCs air quality measurements vs. wind direction at 

Milwaukee-SER for 1999 and 2007 (Figures 23 and 24 respectively) show that that there has 

been a sizable decline in both pollutants levels between these 2 years when winds transport the 

highest levels of precursors to this site (i.e., south-southeasterly to southwesterly flow). These 

displays help corroborate the findings identified in the NOx and VOC median diurnal profiles 

(Figures 17, 18) – that there has been a sizable reduction in ambient levels of ozone precursors 

between 1999 and 2007 at Milwaukee-SER. 

All in all, this attainment demonstration study presents a considerable body of persuasive 

evidence that shows that the development, enactment, promulgation and enforcement of the 

elements in Wisconsin ozone air quality management state implementation plan (SIP) has 

successfully achieved the goal of attaining the 8-hour ozone NAAQS throughout the state, 

including the nine counties currently classified as nonattainment of this NAAQS. 
55

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58

DOUGLAS

BAYFIELD

ASHLAND

IRON

BURNETT

VILAS

WASHBURN SAWYER

PRICE

ONEIDA

FOREST

FLORENCE

BARRON

POLK

RUSK

TAYLOR

CHIPPEWA

ST. CROIX DUNN

PIERCE

PEPIN

EAU CLAIRE

CLARK

LINCOLN

MARATHON

LANGLADE

MARINETTE

OCONTO

MENOMINEE

SHAWANO

DOOR

KEWAUNEE

BROWN

OUTAGAMIE

WOOD PORTAGE WAUPACA

WINNEBAGO MANITOWOC CALUMET

WAUSHARA

JACKSON

JUNEAU ADAMS

MARQUETTE GREEN

LAKE

FOND DU LAC

SHEBOYGAN

MONROE

SAUK COLUMBIA DODGE

WASHINGTON

OZAUKEE MILWAUKEE

JEFFERSON WAUKESHA

DANE

KENOSHA

GREEN ROCK WALWORTH RACINE

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IOWA

GRANT

RICHLAND

CRAWFORD

VERNON

LA CROSSE

BUFFALO

TREMPEALEAU

WEST CENTRAL NORTHEAST

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