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Draft Technical Support Document

Michigan 

Area Designations For the 

2010 SO2 Primary National Ambient Air Quality Standard

Summary

Pursuant to section 107(d) of the Clean Air Act, EPA must initially designate areas as either 

“unclassifiable”, “attainment”, or “nonattainment” for the 2010 one-hour sulfur dioxide (SO2) 

primary national ambient air quality standard (NAAQS). The Clean Air Act defines a 

nonattainment area as one that does not meet the NAAQS or that contributes to a violation in a 

nearby area. 

Michigan submitted recommendations on June 1, 2011. Table 1 below lists Michigan’s 

recommendations and identifies the counties or portions of counties in Michigan that EPA 

intends to designate “nonattainment” based on monitored violations. 

Table 1. Nonattainment Area Designations for Michigan

Area Michigan’s Recommended 

Designations of 

Areas/Counties

EPA's Intended 

Designation of 

Areas/Counties

Detroit, MI

 Wayne County (partial)

 -An area bounded on the 

 east by the Michigan-

 Ontario border, on the south

 by the Wayne County-

 Monroe County border, on 

 the west by Interstate 75 

 north to Southfield Road, 

 Southfield Road to 

 Interstate 94, and Interstate 

 94 north to Michigan 

 Avenue, and on the north by

 Michigan Avenue to 

 Woodward Avenue and a 

 line on Woodward Avenue 

 extended to the Michigan-

 Ontario border

Nonattainment Nonattainment
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Background

On June 3, 2010, EPA revised the primary SO2 NAAQS (75 FR 35520, published on June 22, 

2010). EPA revised the primary SO2 standard by establishing a new one-hour standard at a level 

of 75 parts per billion (ppb) which is attained when the three-year average of the 99th percentile 

of one-hour daily maximum concentrations does not exceed 75 ppb. EPA has determined that 

this is the level necessary to provide protection of public health with an adequate margin of 

safety, especially for children, the elderly and those with asthma. These groups are particularly 

susceptible to the health effects associated with breathing SO2. EPA is revoking the two prior

primary standards of 140 ppb evaluated over 24 hours, and 30 ppb evaluated over an entire year 

because they will not add additional public health protection given a one-hour standard at 75 

ppb. Accordingly, EPA is not designating areas in this process on the basis of either of these two 

primary standards. Similarly, the secondary standard for SO2 has not been revised, so EPA is 

not designating areas in this process on the basis of the secondary standard. 

EPA’s SO2 Designation Approach

Section 107(d) of the Clean Air Act requires that not later than one year after promulgation of a 

new or revised NAAQS, state Governors must submit their recommendations for designations 

and boundaries to EPA by June 2011. Section 107(d) also requires EPA to provide notification 

to states no less than 120-days prior to promulgating an initial area designation that is a 

modification of a state’s recommendation. EPA was to promulgate initial area designations 

within two years of promulgation of the revised primary standard, although EPA has extended 

this deadline for one additional year due to having insufficient information to promulgate the 

designations. If a state did not submit designation recommendations, EPA will promulgate the 

designations that it deems appropriate. If a state or tribe disagrees with EPA’s intended 

designations, they have an opportunity to demonstrate why any proposed modification is 

inappropriate.

Designations guidance was issued by EPA through a March 24, 2011, memorandum from 

Stephen D. Page, Director, U.S. EPA, Office of Air Quality Planning and Standards, to Air 

Division Directors, U.S. EPA Regions I-X. This memorandum identifies factors EPA intends to 

evaluate in determining boundaries for areas designated nonattainment. These five factors 

include: 1) air quality data; 2) emissions and emissions-related data (location of sources and 

potential contribution to ambient SO2 concentrations); 3) meteorology (weather/transport patterns); 

4) geography/topography (mountain ranges or other air basin boundaries); and 5) jurisdictional 

boundaries (e.g., counties, air districts, pre-existing nonattainment areas, reservations, metropolitan 

planning organization), among any other criteria deemed to be relevant to establishing appropriate 

area designations and boundaries for the one-hour SO2 NAAQS.

The March 24, 2011, memo recommended that area boundaries default to the county boundary unless 

information provided by the state or tribe justifies a larger or smaller boundary than that of the 

county. EPA believes it is appropriate to evaluate each potential area on a case-by-case basis, and to 

recognize that area-specific analyses conducted by states, tribes and/or EPA may support a differing 

boundary than that of a default county boundary.
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In this technical support document, EPA discusses its review and technical analysis of the 

recommendations regarding areas with monitored violations submitted by Michigan for designations 

for the one-hour SO2 standard and any modifications from these recommendations.

Definition of important terms used in this document:

1) Designated nonattainment area – an area which EPA has determined, based on a state 

recommendation and/or on the technical analysis included in this document, has violated the 

2010 SO2 NAAQS, based on the most recent three years of air quality monitoring data, or 

contributes to a violation in a nearby area. 

2) Recommended nonattainment area – an area a state or tribe has recommended that EPA 

designate as nonattainment.

3) Violating monitor – an ambient air monitor meeting all methods, quality assurance and siting 

criteria and requirements whose valid design value exceeds 75 ppb, as described in Appendix T 

of 40 CFR part 50.

4) 2010 SO2 NAAQS – The NAAQS for SO2 promulgated in 2010. This NAAQS is 75 ppb, 

based on the three year average of the 99th percentile of the annual distribution of daily 

maximum one-hour average concentrations. See 40 CFR Part 50.17.

5) Design Value - a statistic computed according to the data handling procedures of the NAAQS 

(in 40 CFR 50 Appendix T) that, by comparison to the level of the NAAQS, indicates whether 

the area is violating the NAAQS.

Technical analysis for the Detroit, MI Area

Introduction

This technical analysis for the Detroit, MI area identifies Wayne County with a monitor that 

violates the 2010 SO2 NAAQS, and evaluates nearby counties for contributions to SO2

concentrations in the area. EPA has evaluated this county and nearby counties based on the 

evidence for the factors recommended in the March 24, 2011 EPA guidance.

Figure 1 is a map of the area showing the locations and design values of air quality monitors in 

the area, and the counties surrounding any violating air quality monitors. Notably, a monitor at 

Southwest High School in Detroit recorded a 2009 to 2011 design value of 90 ppb. One other 

monitor operates in the area, at Allen Park, also in Wayne County, about 12 kilometers to the 

southwest. The Allen Park monitor recorded a 2009 to 2011 design value of 49 ppb. 
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Figure 1. Map of sources and monitors in the Detroit, MI area and the intended Detroit 

nonattainment area

Michigan analyzed the sources that might be contributing to the violation at Southwest High 

School. This assessment identified a series of major sources located south of downtown Detroit 

and within a few kilometers of the Detroit River. Based on this assessment, Michigan’s June 1, 

2011 submittal recommended designating a nonattainment area bordered by the MichiganOntario border (in the Detroit River) on the east, the Wayne-Monroe county border on the south, 

Interstate 75, Southfield Road and Interstate 94 on the west, and Michigan Avenue on the north. 

Since Michigan Avenue does not extend fully to the Michigan-Ontario border, Michigan 

subsequently clarified that their recommended nonattainment area should be considered to be 

bounded by Michigan Avenue from Interstate 94 to Woodward Avenue and by Woodward 

Avenue and an extending line as if Woodward Avenue extended to the Michigan-Ontario border. 

Michigan’s recommended nonattainment area averages approximately 6 kilometers east-west 

and about 40 kilometers north-south.

Based on EPA's technical analysis described below, EPA agrees with and intends to designate a 

Detroit, MI nonattainment area for the 2010 SO2 NAAQS with the boundaries recommended by 

Michigan.
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Detailed Assessment

Air Quality Data 

This factor considers the SO2 air quality monitoring data, including the design values (in ppb) 

calculated for all air quality monitors in the Detroit area based on data for the 2008-2010 period.

The 2010 SO2 NAAQS design values for the Detroit, MI area in Michigan are shown in Table 2.

Table 2. Air Quality Data in the Detroit Area

County State Recommended

Nonattainment?

Monitor Air Quality 

System ID

Monitor Location SO2 Design Value, 

2008-2010 (ppb)

Wayne Yes 26-163-0015 42.3028, 83.1065 90

Included in area 26-163-0001 42.2286, 83.2082 49

Monitor in Bold has the highest 2008-2010 design value in the county.

The Southwest High School monitor in Wayne County shows a violation of the 2010 SO2

NAAQS. 

Emissions and Emissions-Related Data

Evidence of SO2 emissions sources in the vicinity of a violating monitor is an important factor 

for determining whether a nearby area is contributing to a monitored violation. For this factor, 

EPA evaluated county level emission data for SO2 and any growth in SO2 emitting activities

since the date represented by those emissions data.

Emissions

The most recent year for which national emissions information was compiled was 2008. 

Michigan provided emissions data for 2009 generally showing emissions similar to 2008 

emissions. Therefore, EPA primarily relied on the 2008 National Emissions Inventory (NEI)

emissions data (NEI08V2). 

Table 3 shows total emissions of SO2 (given in tons per year) for major sources in Wayne 

County and for sources emitting over 1000 tons per year in adjoining Monroe and St. Clair 

Counties. Table 3 also shows pertinent information for sources in these counties emitting greater 

than 100 tons per year of SO2 according to the 2008 NEI. 
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Table 3. SO2 Emissions in the Detroit Area (NEI08V2)

County Facility in 

State 

Recommen

ded N.A. 

Area?

Facility Emissions 

NEI08V2

(tons per 

year)

Facility Location Distance 

to SWHS

monitor 

(km)

Total County 

SO2 Emissions 

(tons per year)

Wayne Yes DTE Trenton Channel 27,622 42.1237, 83.1812 21 55,791

Yes DTE River Rouge 14,491 42.2727, 83.1124 3

Yes USS Great Lakes 6,755 42.2817, 83.1102 2

Yes Wyandotte Muni 1,793 42.2082, 83.1456 11

No GM Hamtramck 566 42.3820, 83.0449 10

Yes Severstal 558 42.3032, 83.1655 5

Yes Dearborn Industrial 

Generation

401 42.3026, 83.154 4

Yes Carmeuse Lime/River 

Rough

395 42.2774, 83.128 3

No Detroit WTP 225 42.2217, 83.3622 23

No Detroit Resource 

Recovery

200 42.3686, 83.0517 7

Monroe No DTE Monroe 118,382 41.8917, 83.3461 54 135,800

No J.R. Whiting 9,260 41.7917, 83.4486 63

No Holcim Cement 7265 41.9933, 83.6596 57

St. Clair No Belle River power 

plant

62,114 42.7748, 82.4945 73 64,389

No E.B. Eddy Paper 1,019 42.9865, 82.4415 93

All of the largest sources in Wayne County are located within the recommended nonattainment 

area. While three sources in Wayne County emitting over 100 tons per year are located outside 

the recommended nonattainment area, these are relatively smaller sources located at sufficient 

distance from the violating monitor to be judged unlikely to have significant impacts at the 

monitor.

Monroe County has a power plant with by far the most emissions of any facility in the area. This 

facility is also located at a substantial distance from the violating monitor. Using emissions 

divided by distance as a rough indicator of impacts, this facility is likely to have less impact than 

DTE’s River Rouge plant and USS’ Great Lakes Works but more impact than other sources in 

the area. Thus, full consideration of the impact of this plant requires consideration of recent 

emission controls at this plant. The other plant in Monroe County and the plant in St. Clair 

County are at even greater distances and are unlikely to have a significant impact on

concentrations at the violating monitor.

Emissions Controls

The emissions data used by EPA in this technical analysis and provided in Table 3 represent 

emissions levels taking into account any control strategies implemented on stationary sources in 

this area up to and including 2008. Michigan did not provide any additional information on 

emissions reductions resulting from controls put into place after 2008. However, EPA examined 

emissions data submitted into EPA Clean Air Markets data base for the Monroe power plant. 
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These data show that this facility installed wet limestone scrubbing systems on two of its four 

units in 2009, reducing SO2 emissions from the 2008 level of 118,382 tons to a 2010 level of 

47,608 tons. Emissions in 2011 from this facility were similar to its emissions in 2010. Given 

this decline in emissions, the Monroe plant is likely to have significantly less impact than sources 

in Wayne County that are much closer to the violating monitor, so that the plant may reasonably 

be judged not to be a significant nearby contributor to the violations.

Meteorology (weather/transport patterns)

When considering a one-hour standard, violations can occur at anytime, even when weather 

patterns are varied from the normal trends of the area. For this area, wind patterns can be from 

any direction. Therefore, for a one-hour standard, it is useful to consider all directions to have 

potential contribution. Nevertheless, winds in this area come from the southwest more 

frequently than from other quadrants, so sources to the south and west of the Southwest High 

School monitor are most likely to contribute to violations at this monitor.

Geography/topography (mountain ranges or other air basin boundaries)

The Detroit area does not have any geographical or topographical barriers significantly limiting 

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

determining the nonattainment boundary.

Jurisdictional boundaries 

Michigan does not have any current SO2 nonattainment areas. Nonattainment areas in Michigan 

have often been defined on the basis of roadways, and roadways in Michigan have well 

established locations and are a suitable basis for defining nonattainment areas.

Other Relevant Information

EPA did not receive additional information relevant to establishing a nonattainment area 

boundary for this area.

Conclusion

The nonattainment area recommended by Michigan includes the sources that are likely to be 

contributing to the violation at the Southwest High School monitor. While a very large source is 

located in Monroe County south of the recommended nonattainment area, this source has 

recently installed significant emission controls, and the source is sufficient distance from the 

violation monitor to warrant its exclusion from the nonattainment area. Other sources outside 

Michigan’s recommended nonattainment area are also likely not to be having a significant 

impact on SO2 concentrations at the violating monitor. Therefore, EPA intends to designate a 

Detroit, MI nonattainment area using the boundaries recommended by Michigan.