Attachment 1

Michigan Area Designations For the 

24-Hour Fine Particle National Ambient Air Quality Standard

The table below identifies the counties in Michigan that EPA has
designated as not attaining the 2006 24-hour fine particle (PM2.5)
standard.  A county or part thereof is designated as nonattainment if it
has an air quality monitor that is violating the standard or if the
county is determined to be contributing to the violation of the
standard.

 

Area 	Michigan Recommended Nonattainment Counties	EPA’s Designated
Nonattainment Counties

Detroit	Livingston

Macomb

Monroe

Oakland

St. Clair*

Washtenaw

Wayne*	Livingston

Macomb

Monroe

Oakland

St. Clair

Washtenaw

Wayne

Grand Rapids	Kent	Kent

Ottawa

* Michigan recommended that Wayne and St. Clair Counties each be a
separate area.  EPA designated the seven counties as a single
nonattainment area.

EPA has designated the remaining counties in the state as
“attainment/unclassifiable.”  

EPA Technical Analysis for Detroit-Ann Arbor-Flint, Michigan 

There are monitors with data showing violations of the 2006 PM2.5 NAAQS
in Monroe, Oakland, St. Clair, Wayne, and Washtenaw Counties.  EPA
previously designated these five counties, along with Livingston and
Macomb Counties, as the nonattainment area for the 1997 PM2.5 NAAQS.   

Michigan recommended that EPA designate all seven counties as
nonattainment for the 2006 PM2.5 NAAQS.  However, Michigan recommended
that the nonattainment area be subdivided into three separate areas. 
The first area would include only Wayne County, which Michigan
characterized as distinctly industrialized.  The second area would
include just St. Clair County, which Michigan characterized as being
especially influenced by international transport from Canada.  The third
area would include the remaining five counties.  EPA reviewed relevant
information for these seven counties and for surrounding counties, and
in particular, considered Michigan’s recommendation of three separate
nonattainment areas for the Detroit area.

EPA agrees with the counties Michigan recommended for designation as
nonattainment for the 2006 PM2.5 NAAQS, but disagrees with Michigan’s
recommendation to subdivide the nonattainment area into three separate
areas.  While some components of the observed concentrations vary in
magnitude and significance from location to location, EPA believes that
a high fraction of the overall observed PM2.5 concentrations at monitors
throughout the Detroit area reflect common origins, including not only a
common regional transported component but also a common metropolitan
scale impact from sources located throughout the seven counties in the
Detroit area..  The level of commuting from county to county is also
such that planning by necessity must address the Detroit area as a
single broad area.  Indeed, the existing metropolitan planning
organization already addresses the seven counties of the existing 1997
PM2.5 NAAQS nonattainment area, and thus is already designed to conduct
planning for the prospective nonattainment area as a whole.  While
Michigan may ultimately opt for a mix of control strategies that include
controls to address emissions that have especially significant impacts
in particular areas, EPA believes that the particulate matter
concentrations in various parts of the area are sufficiently
interrelated that it is essential that a single plan be developed for
the entire Detroit area that addresses the combined effects throughout
the area.  

EPA reviewed the relevant information for other counties within the
combined statistical area as well as counties adjacent to the combined
statistical area in order to determine the appropriate nonattainment
area.  Genesee County, which includes Flint, has moderately low
emissions, and the county has a low CES, reflecting the distance of the
county from violating monitors in the Detroit area and the relative
infrequency with which winds blow from Genesee County to those violating
monitors on high concentration days.  A further reason for excluding
Genesee County is to facilitate planning by providing consistency with
other designations, including the exclusion of the county from the
nonattainment area defined for the 1997 PM2.5 NAAQS and the treatment of
Flint as a separate ozone nonattainment area (now maintenance area) from
the Detroit area.  Lucas County, Ohio is more commonly upwind of most of
the violating monitors in the Detroit area, but Lucas County is somewhat
distant from the violating monitors in the Detroit area, and Lucas
County (dominated by Toledo) is a separate and distinct urban area with
little commuting into or other connection with the Detroit area.  Other
nearby counties have relatively low emissions and no other information
warranted inclusion of the counties in the Detroit nonattainment area. 
Based upon analysis of the Detroit area considering information relevant
to the factors that EPA recommended in guidance, analytical tools
discussed below, and other information provided by Michigan, EPA has
determined that Michigan’s recommended nonattainment counties and
attainment counties were appropriate.

Figure 1 is a map of the counties in the nonattainment area and other
relevant information such as the locations and design values of air
quality monitors, and the metropolitan area boundary.

 

Figure 1

For this area, EPA previously established PM2.5 nonattainment boundaries
for the 1997 PM2.5 NAAQS that included seven counties, with all being
located in Michigan.  

In its December 17, 2007 letter, Michigan recommended that the same
counties be designated as “nonattainment” for the 2006 24-hour PM2.5
standard based on air quality data from 2004-2006.  Michigan did
recommend dividing the seven counties into three separate nonattainment
areas.  This varies from the designation of these counties as a single
nonattainment area for the 1997 PM2.5 NAAQS.  

In August 2008, EPA notified Michigan of its intended designations.  In
this letter, EPA also requested that if the State wished to provide
comments on EPA’s intended designation, it should do so by October 20,
2008.  EPA stated that it would consider any additional information
(e.g., on power plants or partial county areas) provided by the state in
making final decisions on the designations.  Michigan did not provide
information on power plants in Southeast Michigan, and neither EPA nor
Michigan recommended designating any partial county areas.  Michigan did
provide further information in support of its initial recommendations; 
further discussion of this information is provided in the response to
comments document.

Based on EPA's technical analysis described below, EPA designated seven
Michigan counties as nonattainment for the 2006 24-hour PM2.5
air-quality standard as a single, unified Detroit nonattainment area.

The following is a review of data for relevant factors for the Detroit,
Michigan area. 

Factor 1:  Emissions data

For this factor, EPA evaluated county level emission data for the
following PM2.5 components and precursor pollutants:  “PM2.5 emissions
total,” “PM2.5 emissions carbon,” “PM2.5 emissions other,”
“SO2,” “NOx,” “VOCs,” and “NH3.”  “PM2.5 emissions
total” represents direct emissions of PM2.5 and includes: “PM2.5
emissions carbon,” “PM2.5 emissions other”, primary sulfate (SO4),
and primary nitrate.  (Although primary sulfate and primary nitrate,
which are emitted directly from stacks rather than forming in
atmospheric reactions with SO2 and NOx, are part of “PM2.5 emissions
total,” they are not shown in Table 1 as separate items).  “PM2.5
emissions carbon” represents the sum of organic carbon (OC) and
elemental carbon (EC) emissions, and “PM2.5 emissions other”
represents other inorganic particles (crustal).  Emissions of SO2 and
NOx, which are precursors of the secondary PM2.5 components sulfate and
nitrate, are also considered.  VOCs (volatile organic compounds) and NH3
(ammonia) are also potential PM2.5 precursors and are included for
consideration. 

Emissions data were derived from the 2005 National Emissions Inventory
(NEI), version 1.  See
http://www.epa.gov/ttn/naaqs/pm/pm25_2006_techinfo.html.

EPA also considered the Contributing Emissions Score (CES) for each
county.  The CES is a metric that takes into consideration emissions
data, meteorological data, and air quality monitoring information to
provide a relative ranking of counties in and near an area.  Note that
this metric is not the exclusive manner for considering data for these
factors.  A more detailed description can be found at
http://www.epa.gov/ttn/naaqs/pm/pm25_2006_techinfo.html#C.

Table 1 shows emissions of PM2.5 and precursor pollutants components
(given in tons per year) and the CES for violating and potentially
contributing counties in the Detroit area.  Counties that are part of
the Detroit nonattainment area for the 1997 PM2.5 NAAQS are shown in
boldface.  Counties are listed in descending order by CES.

Table 1.  PM2.5 24-hour Component Emissions, and CESs

County	State Recommended Nonattainment?	CES	PM2.5

emissions 

total	PM2.5

emissions 

carbon	PM2.5

emissions 

other	SO2

	NOx

	VOCs

	NH3



Monroe, MI	Yes	100	6,476	752	5,723	129,523	49,678	11,507	937

St. Clair, MI	Yes	100	3,120	547	2,574	69,799	29,200	9,656	470

Wayne, MI	Yes	100	8,401	2,701	5,699	67,359	98,677	80,390	2,442

Macomb, MI	Yes	46	1,834	834	999	5,412	27,287	32,074	1,019

Oakland, MI	Yes	37	3,116	1,556	1,559	7,070	49,789	57,995	1,525

Washtenaw, MI	Yes	13	1,412	560	852	2,042	15,859	16,169	1,194

Livingston, MI	Yes	4	1,383	472	910	937	7,533	9,913	479

Lucas, OH	No	13	2,395	758	1,637	26,551	31,475	23,612	1,780

Genesee, MI	No	3	1,550	602	948	2,029	18,603	20,570	808



Oakland, Macomb, Monroe, St. Clair, and Wayne Counties all have high a
CES relative to other counties in the area, and high emissions.  In
particular, Wayne, Monroe, St. Clair, and Oakland Counties have high
amounts of direct PM2.5 emissions that add directly to the aggregate
ambient levels of PM2.5 at violating monitors in Wayne County.  Monroe,
St. Clair, and Wayne Counties have particularly large amounts of
emissions of SO2 and NOx that combines with other precursors in this
area to make secondarily formed PM2.5 particles that cumulatively add to
the ambient levels of PM2.5, primarily from large stationary source
emissions.  By contrast, other counties in the area like Oakland,
Macomb, and Washtenaw, have large amounts of NOx and VOC emissions, more
indicative of smaller stationary sources and mobile sources that
cumulatively contribute to violations of the NAAQS in the Detroit area. 
EPA notes that these emissions occur in geographic areas well within the
range of transport for PM2.5 and PM2.5 precursors.  EPA has concluded,
consistent with the recommendation of Michigan, that other counties in
the area do not require inclusion within the nonattainment area, based
on emissions.  Lucas County, Ohio, in the Toledo area, has emissions
similar to Macomb and Oakland Counties though it is further from Wayne
County as the Table 2 data show.  Thus based on the emissions factor,
Lucas County, Ohio is a possible candidate for being designated as
nonattainment.  Genesee County has relatively low emissions.

Table 2 provides the data for CES weighting factors.  The trajectory
factors are used in CES calculations to account for seasonal
meteorology.  For the top 10% of days in both the cold and warm seasons,
wind trajectories were run for a 48 hour period preceding the high
monitor reading.  The amount of time the air mass was over a county
within the mixing height was calculated.  The values were scaled so that
the maximum value is 100.  Thus, the county that is most likely to be
upwind of a monitor on a high concentration day in a season is given a
score of 100.  The scores for the other counties will reflect the
relative likelihood of being upwind.  As the concentration of a
pollutant will decrease as it goes further downwind, a distance
weighting factor is also used in calculating the CES.  The distance
factor listed on Table 2 provides the distance from the center of a
county to the center of the violating county.  If a county is violating,
the distance used is the average distance from the center to the county
line.

  Table 2.  CES Factor Data

County	CES	Trajectory Factor- Cold	Trajectory Factor- Warm	Distance (mi)

Monroe, MI	100	91	99	25.1

St. Clair, MI	100	29	25	56.4

Wayne, MI	100	100	100	13.3

Macomb, MI	46	58	50	37

Oakland, MI	37	53	49	29.1

Washtenaw, MI	13	52	56	25.1

Livingston, MI	4	24	23	38.3

Lucas, OH	13	69	79	50.4

Genesee, MI	3	11	10	55.5



Factor 2:  Air quality data 

This factor considers the 24-hour PM2.5 design values (in µg/m3) for
air quality monitors in counties in the Detroit area based on data for
the 2005-2007 period.  These data are from Federal Reference Method
(FRM) monitors located in the state.  A monitor’s design value
indicates whether that monitor attains a specified air quality standard.
 The 24-hour PM2.5 standards are met when the 3-year average of a
monitor’s 98th percentile values are 35 µg/m3 or less.  A design
value is only valid if minimum data completeness criteria are met.

The 24-hour PM2.5 design values for counties in the Detroit area are
shown in Table 3.  

	Table 3.  Air Quality Data

County	State 

Recommended

Nonattainment?	Design Values

2004-2006	Design Values

2005-2007

Monroe, MI	Yes	39	38

St. Clair, MI	Yes	39	41

Wayne, MI	Yes	44	43

Macomb, MI	Yes	36	35

Oakland, MI	Yes	39	40

Washtenaw, MI	Yes	38	39

Livingston, MI	Yes	0	0

Lucas, OH	No	35	35

Genesee, MI	No	30	29



Oakland, Monroe, St. Clair, Washtenaw, and Wayne all have monitors with
2005-2007 design values in excess of the 2006 24-hour PM2.5 standards. 
Macomb County has a monitor with a 2005-2007 design value that now meets
the air quality standards, although its 2004-2006 design value did not
meet the standards.  Genesee County and Lucas County, Ohio also are
meeting the standard.  Livingston County does not have PM2.5 air quality
monitoring data.

For purposes of its review, EPA used data available from the Chemical
Speciation Network and the Interagency Monitoring of Protected Visual
Environments (IMPROVE) network to estimate the composition of fine
particle mass on days with the highest fine particle concentrations. 
Analysis of these data indicates that the days with the highest fine
particle concentrations in the Detroit area occur about 35% in the warm
season and 65% in the cool season.  In the warm season, the average
chemical composition of the highest days is 20% sulfate, no nitrate, 67%
carbon, and 13% crustal.  In the cool season, the average chemical
composition of the highest days is 20% sulfate, 45% nitrate, 24% carbon,
and 10% crustal.  These data indicate that sources of SO2, NOx, and
direct PM2.5 emissions contribute to violations in the area.  Sources of
these types of emissions are located throughout the seven counties that
EPA has concluded should be designated nonattainment for the 2006 PM2.5
NAAQS. 

Factor 3: Population density and degree of urbanization (including
commercial development)

Table 4 shows the 2005 population for each county in the area being
evaluated, as well as the population density for each county in that
area.  Population data gives an indication of whether it is likely that
population-based emissions might contribute to violations of the 24-hour
PM2.5 standards. 

Table 4.  Population

County	State Recommended Nonattainment?	2005 Population	2005 Population
Density (pop/sq mi)

Wayne, MI	Yes	1,990,932 	3227

Oakland, MI	Yes	1,213,669 	1339

Macomb, MI	Yes	   828,950 	1718

Lucas, OH	No	   447,410 	1290

Genesee, MI	No	   442,732 	684

Washtenaw, MI	Yes	   342,124 	475

Livingston, MI	Yes	   181,404 	309

St. Clair, MI	Yes	   171,079 	232

Monroe, MI	Yes	   153,772 	275



Oakland and Wayne Counties both have over a million residents.  Macomb
County trails with a population that is still over 800,000.  The
population density of these three counties stands out as being well
above that of the other area counties.  EPA believes that the high
population of these counties is reflective of emissions activities that
cumulatively contribute to violations at monitors in Wayne County. 
Lucas County, Ohio has a population density slightly lower than Oakland
County’s figure, but it is in the Toledo area which is in attainment
of the 2006 PM2.5 standards.  The populations and population densities
of the other area counties are still large enough that this factor does
not suggest inclusion or exclusion in the Detroit nonattainment area. 

Factor 4: Traffic and commuting patterns 

This factor considers the number of commuters in each county who drive
to another county within the Detroit area, the percent of total
commuters in each county who commute within the area, as well as the
total Vehicle Miles Traveled (VMT) for each county in millions of miles
(see Table 5).  A county with numerous commuters is generally an
integral part of an urban area and is likely contributing to fine
particle concentrations in the area.   A large amount of VMT is also
indicative of a large amount of mobile source related PM2.5 precursor
emissions, especially NOx and VOC. 

Table 5.  Traffic and Commuting Patterns

County	State Recommended Nonattainment?	2005 VMT

(106 mi)	Number Commuting to any violating counties 	Percent

Commuting to any violating counties 	Number Commuting within/to
statistical area 	Percent

Commuting within/to statistical area 

Wayne, MI	Yes	 19,866 	816,490 	99 	    819,550 	          99 

Macomb, MI	Yes	   6,790 	379,440 	99 	    380,980 	          99 

St. Clair, MI	Yes	   1,422 	74,030 	97 	      75,260 	          99 

Oakland, MI	Yes	 13,709 	585,240 	97 	    596,830 	          99 

Washtenaw, MI	Yes	   4,105 	161,830 	96 	    164,460 	          97 

Monroe, MI	Yes	   2,058 	53,620 	78 	      53,750 	          78 

Livingston, MI	Yes	   1,925 	39,760 	50 	      76,610 	          96 

Genesee, MI	No	   5,447 	26,310 	14 	    178,980 	          96 

Lucas, OH	No	   4,418 	7,740 	4 	        7,780 	            4 



The listing of counties on Table 5 reflects a ranking based on the
number of people commuting to other counties.  The counties that are in
the nonattainment area for the 1997 PM2.5 NAAQS are shown in boldface. 
The commuting data implies that all the counties that are in the 1997
standards nonattainment area counties are all integrated into the
Detroit area.  In particular, the commuting data for Lucas County, Ohio
show little connection of this county to the Detroit area with just 4%
of its workers commuting to violating counties and into the Detroit
area.  In contrast, the seven counties in the Detroit area all have a
high percentage of workers commuting to violating counties and within
the Detroit area.  In terms of VMT, this data reflect that Wayne,
Oakland, Macomb, and Washtenaw have relatively large numbers of both
drivers and miles traveled that indicate significant NOx and VOC
emissions.  These emissions occur within a geographic area that is well
within the range for transport to the violating monitors in Wayne
County, and meteorological data confirm that this transport can occur on
days with high ambient PM2.5 levels in Wayne County.  This factor
suggests that Livingston, Macomb, Monroe, Oakland, St. Clair, Washtenaw,
and Wayne should be included in the Detroit nonattainment area.  This
factor also indicates that Lucas County, Ohio is not a part of the
Detroit area and thus is weak candidate for inclusion in the Detroit
nonattainment area.

Note:  The 2005 VMT data used for table 5 and 6 of the 9-factor analysis
has been derived using methodology similar to that described in
“Documentation for the final 2002 Mobile National Emissions Inventory,
Version 3, September 2007, prepared for the Emission Inventory Group,
U.S. EPA.  This document may be found at:
ftp://ftp.epa.gov/EmisInventory/2002finalnei/documentation/mobile/2002_m
obile_nei_version_3_report_092807.pdf.  The 2005 VMT data were taken
from documentation which is still draft, but which should be released in
2008.

Factor 5:  Growth rates and patterns  

This factor considers population growth for 2000-2005 and growth in
vehicle miles traveled for 1996-2005 for counties in Detroit area, as
well as patterns of population and VMT growth.  A county with rapid
population or VMT growth is generally an integral part of an urban area
and likely to be contributing to fine particle concentrations in the
area.

Table 6 below shows population, population growth, VMT, and VMT growth
for counties that are included in the Detroit area.  Counties are listed
in descending order based on VMT growth between 1996 and 2005.

Table 6.  Population and VMT Growth and Percent Change

County	Population (2005)	Population % change (2000-05)	2005 VMT

(106 mi)	VMT

% change

(1996-2005)

Oakland, MI	 1,213,669 	1 	    13,709 	          42 

Monroe, MI	    153,772 	5 	     2,058 	          38 

Washtenaw, MI	    342,124 	5 	     4,105 	          37 

Genesee, MI	    442,732 	1 	     5,447 	          23 

Livingston, MI	    181,404 	14 	     1,925 	          18 

Wayne, MI	 1,990,932 	-3	    19,866 	          10 

Lucas, OH	    447,410 	-2	     4,418 	            8 

Macomb, MI	    828,950 	5 	     6,790 	            8 

St. Clair, MI	    171,079 	4 	     1,422 	         -23



Livingston County experienced population growth of 14% from 2000 to
2005.  The population change was 5% or less in the other counties during
the same period.  Considering VMT growth, Oakland County had the
greatest percent increase.  Monroe and Washtenaw also had large VMT
growth.  The other area counties had more modest VMT growth except for
St. Clair County.  VMT dropped by 23% in St. Clair County.

Factor 6:  Meteorology (weather/transport patterns)

For this factor, EPA considered data from National Weather Service
instruments and other meteorological monitoring sites in the area.  Wind
direction and wind speed data for 2005-2007 were analyzed, with an
emphasis on “high PM2.5 days” for each of two seasons, an
October-April “cold” season and a May-September “warm” season. 
These high days are defined as days where any FRM or FEM air quality
monitors had 24-hour PM2.5 concentrations above 95% on a frequency
distribution curve of PM2.5 24-hour values. 

For each air quality monitoring site, EPA developed a “pollution
rose” to understand the prevailing wind direction and wind speed on
the days with highest fine particle concentrations.  The figure
identifies 24-hour PM2.5 values by color; days exceeding 35 μg/m3 are
denoted with a red or black icon.  A dot indicates the day occurred in
the warm season; a triangle indicates the day occurred in the cool
season.  The center of the figure indicates the location of the air
quality monitoring site, and the location of the icon in relation to the
center indicates the direction from which the wind was blowing on that
day.  An icon that is close to the center indicates a low average wind
speed on that day.  Higher wind speeds are indicated when the icon is
further away from the center.

Pollution roses for three Detroit area counties are provided as Figure
2A, 2B, and 2C.  In the Wayne County figure, Figure 2A, winds on high
concentration days tend to come from South to Southwest.  Therefore,
counties located to the south and southwest of the violating monitor in
Wayne County are more likely than others to be contributing to the
violation when considering meteorology alone.  As Michigan recommended
dividing the area into three nonattainment areas, EPA also examined
pollution roses for other counties.  Figure 2B is the pollution rose for
St. Clair County.  It shows the winds in St. Clair County tend to be
from the South.  St. Clair County is in the northern portion of the
Detroit area.  This suggests emissions from other Detroit area counties
contribute to the St. Clair County violation.  Oakland County is North
of Wayne County and Southwest of St. Clair County.  The pollution rose
for Oakland County is Figure 2C.  It shows the winds come from South to
Southeast most frequently, but it also comes from Northeast
occasionally.  Considering this factor, Wayne County emissions appear to
affect the PM2.5 concentrations in Oakland County.  Considering that the
wind is occasionally from other directions, other counties in the area
may also contribute to the violation in Oakland County.  This factor
does not indicate that Wayne County or St. Clair County should be
separate nonattainment areas from the rest of the Detroit area.  

 

Figure 2A Wayne County

 

Figure 2B St. Clair County

 

Figure 2C Oakland County

Note:  the meteorology factor is also considered in each county’s
Contributing Emissions Score because the method for deriving this metric
included an analysis of trajectories of air masses for high PM2.5 days.

Factor 7:  Geography/topography (mountain ranges or other air basin
boundaries)

The geography/topography analysis evaluates the physical features of the
land that might have an effect on the air shed and, therefore, on the
distribution of PM2.5 over the area.

The Detroit area does not have any geographical or topographical
barriers significantly limiting air-pollution transport within its air
shed.  This supports the conclusion that emissions and emissions
activities in the counties surrounding Wayne County can transport to
violating monitors and add to the aggregate ambient PM2.5 in the area.  

Factor 8:  Jurisdictional boundaries

In evaluating the jurisdictional boundary factor, EPA gave special
consideration to areas that were already designated nonattainment in
2005 for violating the 1997 fine particle standards.  Analysis of
chemical composition data in these areas indicates that the same
components that make up most of the PM2.5 mass in the area on an annual
average basis such as sulfate and direct PM2.5 carbon in many eastern
areas also are key contributors to the PM2.5 mass on days exceeding the
24-hour PM2.5 standard.  These data indicate that in many cities, the
same source categories that contribute to violations of the annual
standard also contribute to exceedances of the 24-hour standard.  

EPA has generally concluded that counties that were designated as having
emissions sources contributing to fine particle concentrations exceeding
the 1997 standards (all areas violated the annual standard, two also
violated the previous 24-hour standard) also contribute to fine particle
concentrations on the highest days.  For this reason, EPA believes that
for most existing nonattainment areas, the nonattainment area for the
2006 24-hour standard should be the same.  Consideration also should be
given to existing boundaries and organizations as they may facilitate
air quality planning and the implementation of control measures to
attain the standard.  Areas already designated as nonattainment
represent important boundaries for state air quality planning.

The Southeast Michigan Council of Governments (SEMCOG) is the
Metropolitan Planning Organization (MPO) for Livingston, Macomb, Monroe,
Oakland, St. Clair, Washtenaw, and Wayne counties.  This planning
organization already exists to facilitate coordinated air planning
across the Detroit area, including all seven counties that EPA is
designating nonattainment for the PM2.5 NAAQS.  SEMCOG webpage:
http://www.semcog.org/

The Detroit ozone nonattainment area includes Lenawee, Livingston,
Macomb, Monroe, Oakland, St Clair, Washtenaw, and Wayne Counties.  The
Flint ozone maintenance area includes Genesee and Lapeer Counties.

In this area, EPA’s analysis has confirmed that the same boundaries
are appropriate for the 1997 PM2.5 NAAQS and the 2006 PM2.5 NAAQS.  In
particular, EPA has concluded that the same emissions sources and
activities are contributing to violations of both NAAQS, as evidenced by
the emissions inventories for these counties and speciated PM2.5 data
for this area.  In addition, the geographic location of these counties
adjacent to Wayne County, and the meteorological data for this area,
confirms that these emissions are contributing to ambient PM2.5 levels
at the violating monitor in Wayne County.  Thus, the existence of the
prior boundaries and the local planning organization covering that area,
will serve to facilitate development of a more effective and coordinated
nonattainment area plan that will be more likely to result in
achievement of the NAAQS as expeditiously as practicable.

Since a planning body is already established to provide planning on
exactly the boundaries EPA and the State have recommended, the
jurisdictional boundaries factor supports establishing a seven county
nonattainment area.  The jurisdictional boundary factor indicates a link
between the seven counties that EPA is designating nonattainment in the
Detroit area.  Thus, this factor gives EPA an indication that dividing
the counties into separate nonattainment areas would be inappropriate.

Factor 9:  Level of control of emission sources 

Under this factor, the existing level of control of emission sources is
taken into consideration.  The emissions data used by EPA in this
technical analysis and provided in Table 1 under Factor 1 represent
emissions levels taking into account any control strategies implemented
in the Detroit area before 2005 on stationary, mobile, and area sources.
 Data are presented for PM2.5 components that are directly emitted,
carbonaceous PM2.5 and crustal PM2.5, and for pollutants which react in
the atmosphere to form fine particles such as SO2, NOx, VOC, and
ammonia.  

In considering county-level emissions, EPA used data from the 2005
National Emissions Inventory, the most updated version of the national
inventory available at the beginning of the designations process in late
2007.  However, EPA recognized that for certain counties, emissions may
have changed since 2005.  For example, certain power plants or large
sources of emissions in or near this area may have installed emission
controls or otherwise significantly reduced emissions since 2005.  Some
States provided updated information on emissions and emission controls
in their comments to EPA.  EPA considered such additional information in
making final designation decisions.  

With regard to nearby power plants, EPA considered information about
whether a specific plant installed federally enforceable emission
controls by December 2008 resulting in significant emissions reductions.
 A control requirement is considered to be federally-enforceable if it
is required by a State regulation adopted in a State implementation
plan, if it is included in a federally-enforceable Title V operating
permit, or if it is required by a consent decree which also requires the
controls to be included in federally enforceable permit upon termination
of the consent decree.  In making final decisions, EPA also considered
whether a facility would continue to emit pollutants which contribute to
PM2.5 exceedances even after emission controls are operational. 

Michigan did not provide other information regarding power plants or any
other large sources in the Detroit area to indicate that the emissions
have recently changed at these sources in any material way.

EPA Technical Analysis for Grand Rapids, Michigan 

A monitor in Grand Rapids (Kent County) is showing violations of the
2006 PM2.5 NAAQS.  Michigan recommended a nonattainment area for the
2006 PM2.5 standards consisting solely of Kent County.  EPA reviewed
relevant information for the six counties in the combined statistical
area for Grand Rapids and for surrounding counties.	 

EPA has concluded that the appropriate nonattainment area for Grand
Rapids consists of Kent and Ottawa Counties.  Kent County is violating
the air quality standards and contributes to those violations.  Ottawa
County is immediately adjacent to Kent County.  Ottawa County has
greater emissions of most of the relevant pollutants than Kent County,
and indeed EPA’s CES analysis suggests that Ottawa County contributes
more to the violations in Kent County than Kent County itself.  A
sizable fraction of Ottawa County commuters commute into Kent County. 
The pollution rose for this area likewise confirms that there are winds
from the direction of Ottawa County towards Kent County on days with
high ambient PM2.5 levels, and thus supports the conclusion that there
is contribution from the direction of Ottawa County towards the
violating monitor in Kent.  Kent and Ottawa comprise the Grand Rapids
ozone maintenance area, so a planning area that consists of these two
counties will also provide for air planning consistent with historical
practice.  

EPA reviewed relevant information for other counties within the combined
statistical area as well as for counties adjacent to the combined
statistical area in order to determine the appropriate nonattainment
area.  Muskegon and Allegan Counties have moderate emissions, but low
population, low percentage of commuters commuting into Kent County, and
low probable impact on violations in Kent County.  Therefore, EPA
believes that the Grand Rapids PM2.5 nonattainment area should not
include these two counties.  Other Michigan counties in or near the
combined statistical area have relatively low emissions, and no other
relevant information warranted inclusion of these counties in the
nonattainment area.

Figure 1 is a map of the counties in the nonattainment area and other
relevant information such as the locations and design values of air
quality monitors, and the metropolitan area boundary.

 

Figure 1

In its December 17, 2007 letter, Michigan recommended that only Kent
County be designated as “nonattainment” for the 2006 24-hour PM2.5
standard based on air quality data from 2004-2006.  

In August 2008, EPA notified Michigan of its intended modification of
the State’s recommendation to include Ottawa County.  In this letter,
EPA also requested that if the State wished to provide comments on
EPA’s intended designation, it should do so by October 20, 2008.  EPA
stated that it would consider any additional information (e.g., on
reduced emissions from sources or appropriate partial county areas)
provided by the state in making final decisions on the designations. 
The information that Michigan provided is discussed here and in the
response to comments document.

Based on EPA's technical analysis described below, EPA is designating
two Michigan counties as nonattainment for the 2006 24-hour PM2.5 NAAQS
as the Grand Rapids nonattainment area, based upon currently available
information.  

The following is a review of data for relevant factors for the Grand
Rapids, Michigan area. 

Factor 1:  Emissions data

For this factor, EPA evaluated county level emission data for the
following PM2.5 components and precursor pollutants:  “PM2.5 emissions
total,” “PM2.5 emissions carbon,” “PM2.5 emissions other,”
“SO2,” “NOx,” “VOCs,” and “NH3.”  “PM2.5 emissions
total” represents direct emissions of PM2.5 and includes: “PM2.5
emissions carbon,” “PM2.5 emissions other”, primary sulfate (SO4),
and primary nitrate.  (Although primary sulfate and primary nitrate,
which are emitted directly from stacks rather than forming in
atmospheric reactions with SO2 and NOx, are part of “PM2.5 emissions
total,” they are not shown in Table 1 as separate items).  “PM2.5
emissions carbon” represents the sum of organic carbon (OC) and
elemental carbon (EC) emissions, and “PM2.5 emissions other”
represents other inorganic particles (crustal).  Emissions of SO2 and
NOx, which are precursors of the secondary PM2.5 components sulfate and
nitrate, are also considered.  VOCs (volatile organic compounds) and NH3
(ammonia) are also potential PM2.5 precursors and are included for
consideration. 

Emissions data were derived from the 2005 National Emissions Inventory
(NEI), version 1.  See
http://www.epa.gov/ttn/naaqs/pm/pm25_2006_techinfo.html.

EPA also considered the Contributing Emissions Score (CES) for each
county.  The CES is a metric that takes into consideration emissions
data, meteorological data, and air quality monitoring information to
provide a relative ranking of counties in and near an area.  Note that
this metric is not the exclusive manner for considering data for these
factors.  A more detailed description can be found at
http://www.epa.gov/ttn/naaqs/pm/pm25_2006_techinfo.html#C.

Table 1 shows emissions of PM2.5 and precursor pollutants components
(given in tons per year) and the CES for violating and potentially
contributing counties in the Grand Rapids area.  Counties that are part
of the Grand Rapids nonattainment area for the 1997 PM2.5 NAAQS are
shown in boldface.  Counties are listed in descending order by CES.

Table 1.  PM2.5 24-hour Component Emissions, and CESs

County	State Recommended Nonattainment?	CES	PM2.5

emissions 

total	PM2.5

emissions 

carbon	PM2.5

emissions 

other	SO2

	NOx

	VOCs

	NH3



Ottawa, MI	No	100	3,153	667	2,485	46,545	27,918	14,897	3,837

Kent, MI	Yes	71	2,102	895	1,207	5,005	24,130	33,459	2,152

Allegan, MI	No	17	1,238	423	814	994	5,271	11,625	4,196

Muskegon, MI	No	15	1,808	490	1,317	14,804	11,273	10,400	709

Barry, MI	No	6	764	274	491	287	1,789	4,769	618

Ionia, MI	No	5	823	223	600	375	2,440	3,556	2,122



The CES and emissions of Kent and Ottawa Counties are well above all
other counties in the area.  Indeed, the CES for Ottawa is higher than
that of Kent County.  Allegan and Muskegon Counties have moderate
emissions, but the relatively low CES for each suggests that these
counties would have substantially less impact on Kent County than Ottawa
County. Barry and Ionia Counties have even less impact, based upon their
respective CES and emissions.   Moreover, the emissions inventories
confirm that Ottawa County has the highest amount of emissions of direct
PM2.5, SO2, NOx and VOCs for this area.  As noted below, these emissions
occur in an area that is geographically close to, and generally upwind
of, the violating monitor in Kent County.  Thus the CES and emissions
support inclusion of Ottawa County within the Grand Rapids area. 

Table 2 provides the data for CES weighting factors.  The trajectory
factors are used in CES calculations to account for seasonal
meteorology.  For the top 10% of days in both the cold and warm seasons,
wind trajectories were run for a 48 hour period preceding the high
monitor reading.  The amount of time the air mass was over a county
within the mixing height was calculated.  The values were scaled so that
the maximum value is 100.  Thus, the county that is most likely to be
upwind of a monitor on a high concentration day in a season is given a
score of 100.  The scores for the other counties will reflect the
relative likelihood of being upwind.  As the concentration of a
pollutant will decrease as it goes further downwind, a distance
weighting factor is also used in calculating the CES.  The distance
factor listed on Table 2 provides the distance from the center of a
county to the center of the violating county.  If a county is violating,
the distance used is the average distance from the center to the county
line.

  Table 2.  CES Factor Data

County	CES	Trajectory Factor- Cold	Trajectory Factor- Warm	Distance (mi)

Ottawa, MI	100	99	88	23.3

Kent, MI	71	79	63	16.3

Allegan, MI	17	100	100	34.7

Muskegon, MI	15	63	41	38

Barry, MI	6	63	62	32.5

Ionia, MI	5	44	33	24.8



Factor 2:  Air quality data 

This factor considers the 24-hour PM2.5 design values (in µg/m3) for
air quality monitors in counties in the Grand Rapids area based on data
for the 2005-2007 period.  These data are from Federal Reference Method
(FRM) monitors located in the state. A monitor’s design value
indicates whether that monitor attains a specified air quality standard.
 The 24-hour PM2.5 standards are met when the 3-year average of a
monitor’s 98th percentile values are 35 µg/m3 or less.  A design
value is only valid if minimum data completeness criteria are met.

The 24-hour PM2.5 design values for counties in the Grand Rapids area
are shown in Table 3.  

	Table 3.  Air Quality Data

County	State 

Recommended

 Nonattainment?	Design Values

2004-2006	Design Values

2005-2007

Ottawa, MI	No	34	34

Kent, MI	Yes	37	36

Allegan, MI	No	34	34

Muskegon, MI	No	35	33

Barry, MI	No



Ionia, MI	No





The Kent County 2005-2007 design value is above the 2006 standards. 
Allegan, Muskegon, and Ottawa Counties meet the 2006 standards.  There
is no air quality monitoring data for Barry and Ionia Counties. 
However, the absence of a violating monitor alone does not eliminate
counties from nonattainment status.  Each county has been evaluated
based on the weight of evidence of the nine factors and other relevant
information.

For purposes of its review, EPA used data available from the Chemical
Speciation Network and the Interagency Monitoring of Protected Visual
Environments (IMPROVE) network to estimate the composition of fine
particle mass on days with the highest fine particle concentrations. 
Analysis of these data indicates that the days with the highest fine
particle concentrations in the Grand Rapids area occur about 43% in the
warm season and 57% in the cool season.  In the warm season, the average
chemical composition of the highest days is 59% sulfate, no nitrate, 37%
carbon, and 4% crustal.  In the cool season, the average chemical
composition of the highest days is 22% sulfate, 49% nitrate, 27% carbon,
and 1% crustal.  These data indicate that sources of SO2, NOx, and
direct PM2.5 emissions contribute to violations in the area.  Ottawa and
Kent County have relatively large emissions of the pollutants (or
precursors thereof) that are found in significant quantities on the
speciation monitor.

Factor 3: Population density and degree of urbanization (including
commercial development)

Table 4 shows the 2005 population for each county in the area being
evaluated, as well as the population density for each county in that
area.  Population data gives an indication of whether it is likely that
population-based emissions might contribute to violations of the 24-hour
PM2.5 standards.  Kent County has the largest population in the area. 
The population exceeds 100,000 people in Ottawa, Muskegon, and Allegan
Counties.  Barry and Ionia Counties have modest populations.  This
evidence supports designating Kent and Ottawa Counties as the
nonattainment area.

Table 4.  Population

County	State Recommended Nonattainment?	2005 Population	2005 Population
Density (pop/sq mi)

Kent, MI	Yes	    595,979 	685

Ottawa, MI	No	    255,187 	442

Muskegon, MI	No	    174,971 	333

Allegan, MI	No	    113,052 	134

Ionia, MI	No	     64,468 	111

Barry, MI	No	     59,817 	103



Factor 4: Traffic and commuting patterns 

This factor considers the number of commuters in each county who drive
to another county within the Grand Rapids area, the percent of total
commuters in each county who commute within the area, as well as the
total Vehicle Miles Traveled (VMT) for each county in millions of miles
(see Table 5).  A county with numerous commuters is generally an
integral part of an urban area and is likely contributing to fine
particle concentrations in the area.  

Table 5.  Traffic and Commuting Patterns

County	State Recommended Nonattainment?	2005 VMT

(106 mi)	Number Commuting to any violating counties

	Percent

Commuting to any violating counties 

	Number Commuting within/to statistical area 	Percent

Commuting within/to statistical area 

Ottawa, MI	No	    2,024 	29,960 	25 	    119,480 	          99 

Kent, MI	Yes	    6,342 	258,700 	91 	    277,270 	          98 

Allegan, MI	No	    1,159 	8,380 	16 	      44,550 	          87 

Muskegon, MI	No	    1,699 	4,510 	6 	      74,240 	          99 

Barry, MI	No	       417 	6,940 	26 	      19,930 	          74 

Ionia, MI	No	       658 	7,090 	27 	      20,730 	          78 



The listing of counties on Table 4 reflects a ranking based on the
number of people commuting to other counties.  The commuting statistics
show that there is limited commuting into Kent County, the only
violating county in the area.  There is some commuting from Ottawa
County to Kent County.  There are just a few commuters into Kent County
from the other area counties.  Within this area, Ottawa County does have
the second highest number of commuters to Kent County, and the second
highest amount of VMT.  Although information related to this factor is
not conclusive, EPA believes that this supports inclusion of Ottawa
County in the Grand Rapids area.  These data also support excluding
Muskegon and Allegan Counties from the nonattainment area.

Note:  The 2005 VMT data used for table 5 and 6 of the 9-factor analysis
has been derived using methodology similar to that described in
“Documentation for the final 2002 Mobile National Emissions Inventory,
Version 3, September 2007, prepared for the Emission Inventory Group,
U.S. EPA.  This document may be found at:
ftp://ftp.epa.gov/EmisInventory/2002finalnei/documentation/mobile/2002_m
obile_nei_version_3_report_092807.pdf.  The 2005 VMT data were taken
from documentation which is still draft, but which should be released in
2008.

Factor 5:  Growth rates and patterns  

This factor considers population growth for 2000-2005 and growth in
vehicle miles traveled for 1996-2005 for counties in Grand Rapids area,
as well as patterns of population and VMT growth.  A county with rapid
population or VMT growth is generally an integral part of an urban area
and likely to be contributing to fine particle concentrations in the
area.

Table 6 below shows population, population growth, VMT, and VMT growth
for counties that are included in the Grand Rapids area.  Counties are
listed in descending order based on VMT growth between 1996 and 2005.

Table 6.  Population and VMT Growth and Percent Change

County	Population (2005)	Population % change (2000-2005)	2005 VMT

(106 mi)	VMT

% change

(1996-2005)

Kent, MI	    595,979 	3 	     6,342 	          31 

Muskegon, MI	    174,971 	3 	     1,699 	          24

Barry, MI	     59,817 	5 	        417 	          18 

Ionia, MI	     64,468 	5 	        658 	            4 

Allegan, MI	    113,052 	7 	     1,159 	           -1 

Ottawa, MI	    255,187 	7 	     2,024 	           -5



The populations in the area are all rather stable with the limited
growth rates.  Kent, Muskegon, and Barry Counties are experiencing
strong VMT growth.  VMT is declining in Ottawa County.  There was little
VMT change in Allegan and Ionia Counties.

Factor 6:  Meteorology (weather/transport patterns)

For this factor, EPA considered data from National Weather Service
instruments and other meteorological monitoring sites in the area.  Wind
direction and wind speed data for 2005-2007 were analyzed, with an
emphasis on “high PM2.5 days” for each of two seasons, an
October-April “cold” season and a May-September “warm” season. 
These high days are defined as days where any FRM or FEM air quality
monitors had 24-hour PM2.5 concentrations above 95% on a frequency
distribution curve of PM2.5 24-hour values. 

For each air quality monitoring site, EPA developed a “pollution
rose” to understand the prevailing wind direction and wind speed on
the days with highest fine particle concentrations.  The figure
identifies 24-hour PM2.5 values by color; days exceeding 35 μg/m3 are
denoted with a red or black icon.  A dot indicates the day occurred in
the warm season; a triangle indicates the day occurred in the cool
season.  The center of the figure indicates the location of the air
quality monitoring site, and the location of the icon in relation to the
center indicates the direction from which the wind was blowing on that
day.  An icon that is close to the center indicates a low average wind
speed on that day.  Higher wind speeds are indicated when the icon is
further away from the center.

The pollution rose for the Grand Rapids area is provided as Figure 2. 
Winds on high concentration days tend to come from the East to
Southwest.  These data indicate that Ottawa County (as well as Allegan
County) will commonly be upwind of Kent County on high concentration
days.

 

Figure 2

Note:  the meteorology factor is also considered in each county’s
Contributing Emissions Score because the method for deriving this metric
included an analysis of trajectories of air masses for high PM2.5 days.

Factor 7:  Geography/topography (mountain ranges or other air basin
boundaries)

The geography/topography analysis evaluates the physical features of the
land that might have an effect on the air shed and, therefore, on the
distribution of PM2.5 over the area.

The Grand Rapids 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 the
decision-making process.

Factor 8:  Jurisdictional boundaries

In evaluating the jurisdictional boundary factor, EPA gave special
consideration to areas that were already designated nonattainment in
2005 for violating the 1997 fine particle standards.  However, the Grand
Rapids area was designated attainment for the 1997 standards, so
nonattainment area boundaries for the 1997 standards were not a factor
in determining the Grand Rapids nonattainment area boundaries.

The Grand Valley Metropolitan Council is the metropolitan planning
organization for Allegan, Barry, Ionia, Kent, Montcalm, and Ottawa
Counties in Michigan.  Its web site is   HYPERLINK "http://www.gvmc.org"
 www.gvmc.org .

The Grand Rapids, Michigan ozone maintenance area consists of Kent and
Ottawa Counties.  To the degree appropriate, based upon violations and
contributions to violations of the ozone and PM2.5 NAAQS in a particular
area, EPA believes it may be helpful for air planning purposes and for
attainment of both NAAQS, for there to be some consistency between ozone
and PM2.5 nonattainment area boundaries.  Furthermore, the
jurisdictional boundary factor indicates a link between Kent and Ottawa
Counties.  Therefore, this factor supports a nonattainment area that
includes Kent and Ottawa Counties.  While this factor suggests some link
between Kent County and other counties in Southwest Michigan, other
factors suggest less linkage.

Factor 9:  Level of control of emission sources 

Under this factor, the existing level of control of emission sources is
taken into consideration.  The emissions data used by EPA in this
technical analysis and provided in Table 1 under Factor 1 represent
emissions levels taking into account any control strategies implemented
in the Grand Rapids area before 2005 on stationary, mobile, and area
sources.  Data are presented for PM2.5 components that are directly
emitted, carbonaceous PM2.5 and crustal PM2.5, and for pollutants which
react in the atmosphere to form fine particles such as SO2, NOx, VOC,
and ammonia.  

In considering county-level emissions, EPA used data from the 2005
National Emissions Inventory, the most updated version of the national
inventory available at the beginning of the designations process in late
2007.  However, EPA recognized that for certain counties, emissions may
have changed since 2005.  For example, certain power plants or large
sources of emissions in or near this area may have installed emission
controls or otherwise significantly reduced emissions since 2005.  Some
States provided updated information on emissions and emission controls
in their comments to EPA.  EPA considered such additional information in
making final designation decisions.  

With regard to nearby power plants, EPA considered information about
whether a specific plant installed federally enforceable emission
controls by December 2008 resulting in significant emissions reductions.
 A control requirement is considered to be federally-enforceable if it
is required by a State regulation adopted in a State implementation
plan, if it is included in a federally-enforceable Title V operating
permit, or if it is required by a consent decree which also requires the
controls to be included in federally enforceable permit upon termination
of the consent decree.  In making final decisions, EPA also considered
whether a facility would continue to emit pollutants which contribute to
PM2.5 exceedances even after emission controls are operational. 

Michigan provided information regarding emission control devices planned
in the future for a Kent County power plant.  EPA considered this
information in the process of the final designation.  However, EPA is
promulgating these designations based on current emissions and air
quality, not on potential future emissions or air quality.  Therefore,
this information about future reductions in contribution was not
relevant to this designation.  EPA notes that such reductions may be
appropriate for consideration in the development of the nonattainment
area SIP for this area. 

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, the 24-hour PM2.5 standard was revised from 65 micrograms per cubic
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averages for 3 consecutive years).  

