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Wisconsin

Area Designations for the 

2008 Ozone National Ambient Air Quality Standards

The table below identifies the areas and associated counties or parts of counties in Wisconsin that EPA 

intends to designate as nonattainment for the 2008 ozone national ambient air quality standards (2008

NAAQS). In accordance with section 107(d) of the Clean Air Act, EPA must designate an area (county 

or part of a county) “nonattainment” if it is violating the 2008 ozone NAAQS or if it is contributing to a 

violation of the 2008 ozone NAAQS in a nearby area. The technical analyses supporting the boundaries 

for this nonattainment area are provided below.

Table 1: Intended Nonattainment Areas in Wisconsin

Area 

Wisconsin’s Recommended 

Nonattainment Counties

EPA’s Intended Nonattainment 

Counties

Sheboygan, WI None Sheboygan County

EPA intends to designate the remaining counties in Wisconsin that are not listed in the table above as 

“unclassifiable/attainment” for the 2008 ozone NAAQS. 

The analysis below provides the basis for the intended nonattainment area boundaries. It relies on our 

analysis of whether and which monitors are violating the 2008 ozone NAAQS, based on certified air 

quality monitoring data from 2008-2010 and an evaluation of whether nearby areas are contributing to 

such violations. EPA has evaluated contributions from the surrounding counties based on a weight of 

evidence analysis considering the factors identified below. EPA issued guidance on December 4, 2008,

that identified these factors as ones EPA would consider in determining nonattainment area boundaries 

and recommended that states consider these factors in making their designations recommendations to 

EPA.1

 

1. Air quality data (including the design value calculated for each Federal Reference Method 

(FRM) or Federal Equivalent Method (FEM) monitor in the area);

2. Emissions and emissions-related data (including location of sources and population, amount of 

emissions and emissions controls, and urban growth patterns);

3. Meteorology (weather/transport patterns);

4. Geography and topography (mountain ranges or other basin boundaries);

5. Jurisdictional boundaries (e.g., counties, air districts, existing nonattainment areas, Indian 

country, metropolitan planning organizations (MPOs))

Ground-level ozone is generally not emitted directly into the air, but is created by chemical reactions 

between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight. 

Because NOx and VOC emissions from a broad range of sources over a wide area typically contribute to 

violations of the ozone standards, EPA believes it is important to consider whether there are contributing 

emissions from a broad geographic area. Accordingly,in general, EPA chose to examine the 5 factors 

with respect to the larger of the Combined Statistical Area (CSA) or Core Based Statistical Area 

 1 The December 4, 2008 guidance memorandum “Area Designations for the 2008 Revised Ozone National Ambient Air 

Quality Standards” refers to 9 factors. In this technical support document we have grouped the emissions-related factors 

together under the heading of “Emissions and Emissions-Related Data,” which results in 5 categories of factors.
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(CBSA) associated with the violating monitor(s).

2 However, since the Sheboygan, WI Metropolitan 

Statistical Area (MSA) consists of a single county, EPA also chose to evaluate the counties immediately 

adjacent to Sheboygan County. All data and information used by EPA in this evaluation are the latest 

available to EPA and/or provided to EPA by states or tribes.

In EPA’s designations guidance for the 2008 ozone NAAQS3 EPA recommended examining 

CSA/CBSAs because certain factors used to establish CSAs and CBSAs are similar to the factors EPA is 

using in this technical analysis to determine if a nearby area is contributing to a violation of the 2008 

ozone NAAQS. Congress required a similar approach in 1990 for areas classified as serious or above 

for the 1-hour ozone standard and EPA used the same basic approach in the designation process for the 

1997 ozone NAAQS. Where a violating monitor is not located in a CSA or CBSA, EPA’s guidance 

recommended using the boundary of the county containing the violating monitor as the starting point for 

considering the nonattainment area’s boundary. 

Technical Analysis for Sheboygan, WI

The largest statistical area associated with Sheboygan County, WI is the Sheboygan, WI MSA. The 

Sheboygan, WI MSA consists of the single county of Sheboygan. Figure 1 is a map of the Sheboygan, 

WI intended nonattainment area. The map provides other relevant information including the locations 

and design values of air quality monitors, county and other jurisdictional boundaries, Sheboygan MSA 

boundary, existing nonattainment boundary for the 1997 ozone NAAQS, and major transportation 

arteries. 

 2 Lists of CBSAs and CSAs and their geographic components are provided at 

www.census.gov/population/www/metroareas/metrodef.html . The lists are periodically updated by the Office of 

Management and Budget. EPA used the most recent update, based on 2008 population estimates, issued on December 1, 

2009 (OMB Bulletin No. 10-02). 3 See Appendix [x] for a copy of the guidance memorandum.
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Figure 1.

For purposes of the 1997 8-hour ozone NAAQS, this area was designated nonattainment. The boundary 

for the nonattainment area for the 1997 ozone NAAQS included the entire county of Sheboygan.

In March 2009, Wisconsin recommended that all counties in the state be designated as “attainment” for 

the 2008 ozone NAAQS based on air quality data from 2006-2008.

4 It should be noted that 2006-2008 

monitoring data showed a violation of the 2008 ozone NAAQS in Sheboygan County. These data are 

from a monitor sited and operated in accordance with 40 CFR Part 58. 

After considering these recommendations and based on EPA's technical analysis described below, for 

the Sheboygan, WI nonattainment area, EPA intends to designate Sheboygan County (see Table 2

below) as “nonattainment” for the 2008 ozone NAAQS. 

 4 Wisconsin supplied its designation recommendations in a March 12, 2009 letter from Governor Jim Doyle. The state also 

provided a Technical Support Document dated February 27, 2009, which included a nine factor analysis to support the 

Governor’s recommendation decisions. 
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Table 2. State's Recommended and EPA’s Intended Designated Nonattainment Counties for 

Sheboygan, WI Area.

Sheboygan, WI State-Recommended 

Nonattainment Counties

EPA Intended

Nonattainment County

Wisconsin None Sheboygan County

Factor Assessment

Factor 1: Air Quality Data 

For this factor, we considered 8-hour ozone design values (in ppm) for air quality monitors in the 

Sheboygan, WI area and immediately adjacent counties based on data for the 2008-2010 period, which 

are the most recent years with fully-certified air quality data. A monitor’s design value is the metric or 

statistic that indicates whether that monitor attains a specified air quality standard. The 2008 ozone 

NAAQS are met at a monitor when the annual fourth-highest daily maximum 8-hour average 

concentration, averaged over 3 years is 0.075 ppm or less. A design value is only valid if minimum data 

completeness criteria are met. See 40 CFR part 50 Appendix P. Where several monitors are located in a 

county (or a designated nonattainment area or maintenance area), the design value for the county or area 

is determined by the monitor with the highest individual design value.

Note: Monitors that are eligible for providing design value data generally include State and Local Air 

Monitoring Stations (SLAMS) that are sited in accordance with 40 CFR Part 58, Appendix D (Section 

4.1) and operating with a federal reference method (FRM) or federal equivalent method (FEM) monitor 

that meets the requirements of 40 CFR part 58, appendix A. All data from a special purpose monitor 

(SPM) using an FRM or FEM which has operated for more than 24 months is eligible for comparison to 

the NAAQS unless the monitoring agency demonstrates that the data came from a particular period 

during which the requirements of appendix A (quality assurance requirements) or appendix E (probe and 

monitoring path siting criteria) were not met.

The 2010 design value for the Sheboygan, WI MSA is shown in Table 3. 

Table 3. Air Quality Data.

County State Recommended 

Nonattainment?

2008-2010 Design Value 

(ppb)

Sheboygan County No 78

Calumet County No

Fond du Lac County No 63

Manitowoc County No 73

Ozaukee County No 71

Washington County No

Sheboygan County shows a violation of the 2008 ozone NAAQS, therefore this county is included in the 

nonattainment area. Although none of the counties adjacent to Sheboygan County are monitoring a 
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violation of the 2008 8-hour ozone NAAQS, each of these counties has been evaluated, as discussed 

below, based on the five factors to determine whether it contributes to the violation.

Factor 2: Emissions and Emissions-Related Data

EPA evaluated emissions of ozone precursors (NOx and VOC) and other emissions-related data that 

provide information on areas contributing to violating monitors.

Emissions Data

EPA evaluated county-level emission data for NOx and VOC derived from the 2008 National Emissions 

Inventory (NEI), version 1.5. This is the most recently available NEI. (See

http://www.epa.gov/ttn/chief/net/2008inventory.html.) Significant emissions levels in a nearby area 

indicate the potential for the area to contribute to the observed ozone standard violation. Table 4 shows 

2008 emissions of NOx and VOC (in tons per year) for the Sheboygan, WI MSA (Sheboygan County) 

and all adjacent counties. This table also indicates which of the counties were recommended to be 

nonattainment for the 2008 ozone NAAQS by Wisconsin.

Table 4 shows 2008 emissions of NOx and VOC (in tons per year) for the Sheboygan, WI MSA and the 

adjacent counties. 

Table 4. Total 2008 NOx and VOC Emissions.

County State Recommended

Nonattainment? NOx (tpy) VOC (tpy)

Sheboygan County No 7,885 6,291

Calumet County No 1,287 2,323

Fond du Lac County No 3,810 5,066

Manitowoc County No 3,668 4,626

Ozaukee County No 3,690 3,375

Washington County No 3,977 6,675

Sheboygan County must be included in the nonattainment area because of the monitored violation of 

the NAAQS within the county. Sheboygan County has the highest level of emissions of the counties; 

however, Sheboygan and the adjacent counties all have relatively low emissions. The low emission 

levels in the area indicate that longer range transport is the significant contributor to violations of the 

standard in the Sheboygan, WI area. This conclusion is supported by modeling performed for the CrossState Air Pollution Rule which shows the states of Illinois, Indiana, Wisconsin and Michigan 

contributing 28.209 ppb, 11.244 ppb, 8.437 ppb, and 3.117 ppb, respectively, to ozone concentrations at 

the Sheboygan County monitoring site.
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Population Density and Degree of Urbanization

EPA evaluated the population, vehicle use characteristics, and trends of the area as indicators of the 

probable location and magnitude of non-point source emissions. These include ozone-creating 

emissions from on-road and off-road vehicles and engines, consumer products, residential fuel 

combustion, and consumer services. Areas of dense population or commercial development are an 

indicator of area source and mobile source NOx and VOC emissions. Rapid population or Vehicle 

Miles Traveled (VMT) growth (see below) in a county on the urban perimeter signifies increasing 

integration with the core urban area, and indicates that it may be appropriate to include the area 

associated with area source and mobile source emissions as part of the nonattainment area. Table 5

shows the population, population density, and population growth information for Sheboygan County and 

the adjacent counties.

Table 5. Population and Growth.

County

State 

Recommended 

Nonattainment?

2010 

Population

2010 Population

 Density

(1000 pop/sq mi)

 Absolute

 Change

in Population

(2000-2010)

Population 

% Change

(2000-2010)

Sheboygan County No 115,507 0.22 2,762 +2%

Calumet County No 48,971 0.12 8,243 +20%

Fond du Lac County No 101,633 0.13 4,250 +4%

Manitowoc County No 81,442 0.14 -1483 -2%

Ozaukee County No 86,395 0.37 3,867 +5%

Washington County No 131,887 0.30 13,928 +12%

Sources: U.S. Census Bureau population estimates for 2010 as of August 4, 2011

Population data show that the adjacent counties, as well as Sheboygan County, have relatively low 

populations and population densities. This implies that the population-related NOx and VOC emissions 

in these counties are relatively low. 

Traffic Data

EPA evaluated the total 2008 VMT and percent growth in VMT from 2002 to 2008 for Sheboygan 

County and the adjacent counties. Table 6 shows this data. 
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Table 6. Traffic Data

County

State 

Recommended 

Nonattainment?

2008 VMT*

(million miles)

Percent 

VMT 

Growth 

(2002-2008 )

Sheboygan County, WI No 1,018 -10%

Calumet County No 371 -13%

Fond du Lac County No 1,132 +46%

Manitowoc County No 807 -27%

Ozaukee County No 962 -7%

Washington County No 1,363 +31%

* MOBILE model VMTs are those inputs into the NEI version 1.5. 

Traffic data show that the adjacent counties, as well as Sheboygan County, have relatively low VMT. 

Factor 3: Meteorology (Weather/Transport Patterns)

EPA evaluated available meteorological data to help determine how meteorological conditions, such as 

weather, transport patterns and stagnation conditions, would affect the fate and transport of precursor 

emissions contributing to ozone formation in the Sheboygan, WI MSA. EPA examined the frequency 

distribution of wind directions for summer (June-August) by averaging National Weather Service 

direction-sorted wind directions for a 30 year period. Table 7 shows the summertime 30-year averaged 

percentages of wind directions (winds blowing indo the subject county from the specified wind direction 

sector).

Table 7. Averaged Summertime Wind Direction Percentages for the Sheboygan, WI MSA

Wind Direction Percentage

North-Northeast 15.41%

East-Northeast 6.91%

East-Southeast 9.82%

South-Southeast 10.96%

South-Southwest 20.57%

West-Southwest 15.70%

West-Northwest 13.60%

North-Northwest 7.02%

The wind direction data presented in Table 7 show that there is no “predominant” summertime wind 

direction for Sheboygan County. The distribution is fairly even, with a slightly stronger southern 

component. 

The state provided wind direction data for hours from 2006 through 2008 when the 1-hour ozone 

concentration was greater than or equal to 75 ppb. This data is presented in Table 8.
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Table 8. Primary Wind Direction Percentages for Hours from 2006 Through 2008 When the 1-hour 

Ozone Concentration Was Greater Than or Equal to 75ppb in the Sheboygan, WI MSA

Wind Direction Percentage

North 0%

North-Northeast 0%

Northeast 0%

East-Northeast 1.7%

East 0%

East-Southeast 0.6%

Southeast 0.6%

South-Southeast 4.6 %

South 9.8%

South-Southwest 76.4%

Southwest 5.7%

West-Southwest 0.6%

West 0%

West-Northwest 0%

Northwest 0%

North-Northwest 0%

Table 8 indicates that when considering wind direction data for hours from 2006 through 2008 when the 

1-hour ozone concentration was greater than or equal to 75 ppb in the Sheboygan, WI MSA, the primary 

wind direction was from the south-southwest 76.4% of the time, and the wind had a southerly 

component 98.3% of the time. Thus winds that blow through Washington and Ozaukee counties and to 

a lesser extent Fond du Lac County may bring ozone or ozone precursors into the area on days when 

there are exceedances of the ozone standard at the violating monitor. 

Factor 4: Geography/Topography (Mountain Ranges or Other Air Basin Boundaries)

The Sheboygan, WI area does not have any geographical or topographical barriers significantly limiting 

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

evaluation. 

Factor 5: Jurisdictional Boundaries

Jurisdictional boundaries are considered for the purposes of providing a clearly defined legal boundary 

and to help identify the areas appropriate for carrying out the air quality planning and enforcement 

functions for nonattainment areas. Examples of jurisdictional boundaries include existing/prior 

nonattainment area boundaries for ozone or other urban-scale pollutants, county lines, air district

boundaries, township boundaries, areas covered by a metropolitan planning organization, state lines, and 

Reservation boundaries. 

The Sheboygan, WI area has previously established nonattainment boundaries associated with the 1-

hour and 1997 8-hour ozone NAAQS. For both previous ozone NAAQS, the nonattainment area was 

comprised of the entirety of Sheboygan County, which is synonymous with the Sheboygan, WI MSA. 
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Conclusion

The air quality monitor in Sheboygan County indicates a violation of the 2008 ozone NAAQS based on 

the 2010 design values. Based on the assessment of factors described above, EPA has preliminarily 

concluded that Sheboygan County meets the CAA criteria for inclusion in the Sheboygan, WI 

nonattainment area. This is the same area that comprised the Sheboygan, WI nonattainment area for the

1997 ozone NAAQS and the same area that was designated as nonattainment under the 1-hour NAAQS. 

The other counties considered all had low emissions, population, and VMT. Available meteorological 

data shows that winds that blow through Washington and Ozaukee counties and to a lesser extent Fond 

du Lac County may bring ozone or ozone precursors into the area on days when there are exceedances 

of the ozone standard at the violating monitor. However, the low emissions, population, and VMT in 

these counties leads to the conclusion that longer range transport is the significant contributor to 

violations of the standard in the Sheboygan, WI area. This conclusion is supported by modeling 

performed for the Cross-State Air Pollution Rule which shows the states of Illinois, Indiana, Wisconsin 

and Michigan contributing 28.209 ppb, 11.244 ppb, 8.437 ppb, and 3.117 ppb, respectively, to ozone 

concentrations at the Sheboygan County monitoring site. In conclusion, EPA intends to include only the

county of Sheboygan in the Sheboygan, WI nonattainment area.