See the overview response to comments on power plant issues, located at
the beginning of Section IV.

The CAA requires that a nonattainment area must include not only the
area that is violating the standard, but also nearby areas that
contribute to the violation.  Thus, for each monitor or group of
monitors that indicate violations of a standard, EPA is establishing
nonattainment boundaries that cover a sufficiently large area to include
both the area that violates the standard and the areas that contribute
to the violations.  EPA’s designations guidance for the 2006 PM2.5
standard suggests that the same boundaries established for implementing
the annual PM2.5 standard may also be appropriate for implementing the
24-hour PM2.5 NAAQS in areas where both standards are violated.  Walker
County (partial) and Shelby County are part of the existing Birmingham
nonattainment area.  EPA finds that it is appropriate to include the
same counties in the nonattainment area for the 24-hour standard since
these counties have high emission levels and air quality data indicate
that the same PM2.5 components that are the biggest contributors to
PM2.5 mass on an annual average basis in this area (e.g., sulfate from
SO2 emissions) are also key components of PM2.5 mass on the highest
days.

In addition, Plant Gorgas in Walker County and Plant Gaston in Shelby
County have emissions that are not fully controlled.  Two units at Plant
Gorgas do not have scrubbers.  For the first half of 2008, emissions
from the plant totaled 14,000 tons SO2 and 10,000 tons NOX.  At Plant
Gaston, while a scrubber will be installed on the largest unit in 2010,
four other units will remain without scrubbers.  The 2007 emissions from
these four units were substantial, more than 75,000 tons SO2 and 12,000
tons NOX.

While Alabama anticipates installation and operation of additional
controls in the future, EPA must judge whether current emission levels,
supported by current regulations that provide assurance of continued
operation of existing controls, contribute to existing violations.  EPA
continues to believe that emissions from Walker County (partial) and
Shelby County contribute to violations of the 24-hour PM2.5 NAAQS in
Jefferson County.

The State of Alabama makes the following points as rationale for
excluding Walker County from the Birmingham nonattainment area:

Alabama:

Walker County has a very low population density and VMT compared to
Jefferson County.

EPA Response:

Population and population density were one type of information that EPA
used nationwide to determine the appropriate boundaries for PM
nonattainment 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 standard.  EPA agrees that Walker County has a
relatively smaller population size and density than Jefferson County.
Of the CSA population, about 6 percent (69,980) reside in Walker County,
while about 56 percent (656,014) reside in Jefferson County.  The
population density per square mile is 87 in Walker County and is 584 in
Jefferson County.  Of the CSA vehicle miles traveled, about 5.5 percent
(797) are in Walker County, while about 58.7 percent (8,545) are in
Jefferson County.

Low population density and VMT compared to the remainder of the areas
under consideration for the nonattainment area are among the reasons
that EPA determined that it would be appropriate to include only a
portion of Walker County, rather than the entire County.  EPA believes a
partial nonattainment area designation remains appropriate for Walker
County in view of the large amount of PM2.5 and PM2.5 precursor
emissions from Plant Gorgas and in evaluation of other information such
as the CES and the pollution rose for this area which indicate that the
emissions from this portion of Walker County are contributing to
violations of the NAAQS in adjacent Jefferson County.

Alabama:

The wind infrequently blows from the direction of Walker County towards
Jefferson County on days with high PM2.5 concentrations.

EPA Response:

EPA disagrees with Alabama’s conclusion that winds blow infrequently
from the direction of Walker County towards Jefferson County on days
that are relevant to violations in this area.  The pollution rose in
EPA’s TSD for the Birmingham area reflects both the high number of
days on which winds blow from the direction of the County and the high
ambient levels on those days throughout the year.  Therefore, EPA
believes that elevated PM2.5 levels at the violating monitors originate
from multiple directions in the Birmingham area, including from the
direction from Walker County.

In addition, EPA’s CES score confirms the high degree of contribution
from Walker County to Jefferson County compared to all other counties in
the area except Shelby.  The CES methodology takes into account the
influence of emissions and meteorology on days with high 24-hour fine
particle concentrations and also incorporates the seasonal composition
of fine particle mass and source receptor distance relationships.  Even
though the majority of emissions from all of Walker County emanate from
one source in a small part of that County, the CES score for the County
is 17, which reflects the significance of the level of fine particle
transport to the violating ambient monitor.  The CES scores for other
counties in the area are 100 for Jefferson County, 39 for Shelby County,
and 5 or less for all other counties.  The scores suggest that
particulate matter emissions from Walker County and Shelby County and
the average wind trajectories on high PM fine days have a significant
impact on PM fine levels at the violating ambient monitor in Jefferson
County.

The State of Alabama makes the following points as rationale for
excluding Shelby County from the Birmingham nonattainment area:

Alabama:

The monitor in Shelby County measures attainment of the 24-hour PM2.5
standard, along with five of the eight Jefferson County monitors.  Data
from monitors located between Shelby County and the non-attaining
monitors in Jefferson County do not suggest that Shelby County is
significantly contributing to nonattainment in Jefferson County; rather,
the data shows an obvious local emissions impact around the violating
Birmingham monitors.

EPA Response:

The presence of an attaining monitor in Shelby County does not establish
whether emissions activity in Shelby County is contributing to
violations in adjacent Jefferson County.  EPA believes that whether
Shelby County itself contributes to the violations in Jefferson County
must be evaluated using the types of information that EPA has utilized
in the TSD for this area.  Likewise, EPA does not agree that the
existence of one or more attaining Jefferson County monitors located
between Shelby County and the violating monitors in Jefferson County
establishes whether or not Shelby County is contributing.  The amount of
emissions in Shelby County, the proximity of Shelby to the violations in
Jefferson and meteorological data indicating transport of those
emissions from Shelby towards Jefferson County suggest that the
emissions from Shelby County combine with the emissions from Jefferson
County sources (and others) and cumulatively result in the violations at
the monitors in Jefferson County.

The pollution rose in the TSD for this area confirms that winds blow
from the direction of Shelby towards Jefferson on days with high ambient
PM2.5 in Jefferson County.  The CES score for Shelby was 39, which
places it second only to Jefferson County in the Birmingham area, and
thus ranks its relative contribution to violations in Birmingham higher
than all other surrounding counties.  This information supports EPA’s
conclusion that Shelby is contributing, as that term is intended in
section 107(d) of the CAA.

Alabama:

Alabama argued that only 73 percent of the MSA population resides in
Jefferson County.

EPA Response:

As stated above, population and population density were only one form of
information that EPA evaluated nationwide to determine the appropriate
boundaries for nonattainment areas for the 2006 24-hour PM2.5 NAAQS.  In
conducting our analysis EPA referred primarily to CSA, as defined in OMB
BULLETIN NO. 07-01 (Update of Statistical Area Definitions and Guidance
on Their Uses), December 18, 2006.  According to 2005 population data,
of the Birmingham CSA population, about 14.7 percent (171,373) reside in
Shelby County, while about 56 percent (656,014) reside in Jefferson
County.  The population density per square mile is 212 in Shelby County
and is 584 in Jefferson County.  Although Shelby County does have
smaller population than Jefferson, this does not negate the other types
of information that establish the contribution of Shelby to violations
in Jefferson, such as the particularly high emissions of SO2 and NOX,
the relatively high level of commuting between these counties, and the
lack of topography or other barriers to transport of pollutants from
Shelby to Jefferson.  EPA believes this data continues to support a
nonattainment area designation for Shelby County.

Alabama:

Jefferson County's VMT is approximately five times that of Shelby
County's.

EPA Response:

EPA agrees.  Of the total CSA vehicle miles traveled, approximately 11.3
percent (1,640) of the VMT in 2005 were in Shelby County, while about
58.7 percent (8,545) of the VMT are in Jefferson County.  EPA notes that
this amount of VMT reflects a significant amount of NOX and VOC
emissions, and that these emissions do contribute to violations in this
area, albeit less than the emissions resulting from mobile sources
within Jefferson County itself.  However, EPA’s assessment of this
single form of information does not preclude it from determining that
Shelby County contributes to increased ambient PM2.5 levels in the
Birmingham area, based upon this and other information.

Alabama:

The bulk of the SO2 and NOX point source emissions from Shelby County
can be attributed to Alabama Power‘s Plant Gaston.  However, several
control measures have been installed and will not be reflected in any
previous inventory.

EPA Response:

EPA agrees that Alabama Power Company – Plant Gaston is the most
significant individual source of NOX and SO2 emissions in Shelby County.
 The emissions from this plant are approximately 130,000 tons per year
of SO2 and 20,000 tons per year of NOX as well as a large quantity of
direct PM2.5.  These emissions make this source among the largest in the
Birmingham area, and these emissions are of the types that are well
represented in the speciated data for ambient PM2.5 in this area.  These
emissions occur in a county immediately adjacent to Jefferson County,
and only about 28 miles from the violating monitors in Jefferson County.
 Thus, these emissions occur at a location that is well within the range
for transport of PM2.5 and PM2.5 precursors.  Other analytical tools
used by EPA, such as the CES score and the pollution rose for this area
also confirm that emissions from this plant contribute to violations in
the Birmingham area.  The emission units at Plant Gaston are not
controlled by SO2 scrubbers, although the largest of the facility’s
five units is scheduled for a scrubber to be installed by 2010.

Alabama argues that the installation of scrubbers on one unit of this
source in 2010 is a reason to exclude Shelby County from the Birmingham
nonattainment area.  EPA disagrees.  Section 107(d) obligates EPA to
designate as nonattainment “any area that does not meet” the NAAQS,
and any nearby area that “contributes” to those violations.  Given
the present tense formulation of this provision, EPA does not believe it
is appropriate to base designations on projections of future violations
or future contributions, but rather upon the facts at the time of the
designation.

With respect to the overall level of control at this source, EPA notes
that not all of the units at this source are fully controlled and that
additional emissions reductions may be necessary and appropriate for
this source.  The determination of what level of control for this source
should be required will be addressed in the nonattainment area plan
developed for the Birmingham area, and it would be inappropriate for
Alabama and EPA to prejudge that decision in the context of the
designations.  Based upon the amount and type of emissions, and the
location of this source, EPA has concluded that it continues to
contribute to violations in the Birmingham area.

The State of Alabama makes the following points as rationale for
designating only a portion of Jefferson County as nonattainment, which
is a change from its original recommendation.

Alabama:

Alabama revised its original recommendation that EPA designate all of
Jefferson County as nonattainment, on the grounds that the area should
include “only the local airshed for the monitors violating the 24-hour
PM2.5 standard.”

EPA Response:

EPA disagrees with Alabama’s view that the violating monitors in
Birmingham are located in a “local airshed” that is distinct from
the remainder of the Birmingham area.  EPA has considered nonattainment
areas boundaries for smaller areas (including for partial counties),
when there is clear factual evidence that the designated area is in a
separate airshed from the immediately surrounding areas, e.g., when the
area is separated by mountain ranges that clearly impede air flow
between the areas.  Given the topography and the meteorological evidence
in the Birmingham area, EPA sees no factual basis for a credible claim
that the violating monitors in this area are in an airshed separate from
the remainder of Jefferson County, or from Walker County and Shelby
County.

Alabama:

The data from the Jefferson County monitors, along with an air quality
study commissioned in 2005 by the Alabama Department of Environmental
Management (ADEM) and the Jefferson County Department of Health,
indicates the clear existence of a local emissions influence on the
violating monitors.  This study concluded that there is a well-defined
local source influence in addition to a regional component of the annual
PM2.5 concentrations measured at the Wylam and North Birmingham
monitors.  Only three of the eight Jefferson County monitors violate the
24-hour standard, all of which will be captured by the partial area that
we are proposing for nonattainment designation.

EPA Response:

EPA agrees that “local” emissions sources have an influence on the
violations in the Birmingham area.  Alabama does not contend, however,
nor could it, that all of the ambient PM2.5 at the violating monitors in
this area are the result of one or more specific sources in the near
vicinity of the monitors.  EPA believes that the violations in
Birmingham are the result of the cumulative impacts of emissions from
various sources in Jefferson County and nearby Walker and Shelby
Counties, in addition to emissions from sources that are not in nearby
areas or are in other States.  As a result, under section 107(d) EPA
must include these nearby areas within the boundaries of the
nonattainment area for Birmingham.

Alabama:

In support of its recommendation that EPA designate only a portion of
Jefferson County nonattainment, Alabama also referred to the results of
a study it commissioned from Envair “to investigate the source(s) of
particulate matter pollution in and around the NBHM and WYL monitors.”
 According to Alabama, “monitoring data clearly indicated a strong
local influence on the high particulate matter concentrations.”

EPA Response:

EPA does not agree that the Envair study supports a position that only
“local” sources are contributing to violations of the NAAQS in this
area.  Even the portions of the study quoted by the State in its October
2, 2008, letter indicate that contribution is the result of emissions
across a broader area than that recommended by Alabama.  In addition to
a “large regional influence” and a “significant influence of local
sources,” the Envair study notes that the ambient levels are
“supplemented by a general urban component” of emissions.
Similarly, in addition to the “local” stationary sources that
Alabama would evidently like to encompass within a much smaller
designated area, the Envair study notes that there is a “complementary
contribution of emissions from local transportation sources, including
motor vehicles and railroads.”  EPA recognizes the study indicates
that there is a strong local influence from certain industrial
facilities in the Birmingham area.  However, while the study does
implicate some of the very large local sources as significant
contributors, it does not say those are the only sources.  Total fine
particle mass on the high concentration days in Birmingham indicates
that other metropolitan-area sources such as transportation and power
plants also contribute.  Finally, the Envair study was developed to
analyze the area for purposes of the 1997 annual PM2.5 NAAQS, so it does
not necessarily translate to what may be appropriate for the 2006 24
hour PM2.5 NAAQS for this area.

California Air Resources Board (CARB) Multi-Area

CARB:

The State of California requested that EPA modify the proposed
nonattainment boundaries to be consistent with California’s original
recommendations for the City of Calexico, Sacramento County, City of
Chico, and the combined cities of Yuba City/Marysville.  The State and
EPA are in agreement regarding the boundaries for the South Coast Air
Basin, San Joaquin Valley Air Basin, and San Francisco Bay Area.  The
State of California provided additional information to document the
extent of international transport causing the localized impacts in
Imperial County, and the localized impact of wood smoke in the other
areas at issue.

EPA Response:

EPA appreciates the additional information submitted by the CARB in
their letter dated October 15, 2008.  As CARB pointed out in their
letter, States and Tribes need to submit recommendations identifying
where violations are occurring and including nearby areas that contain
emission sources that contribute to the observed violations.

In response to the information submitted by CARB, EPA has modified our
previous recommendations for Imperial County, Butte County, Yuba/Sutter
Counties, and the Sacramento area (including Yolo, Solano, Placer and El
Dorado Counties).  EPA originally recommended a larger nonattainment
boundary for these areas but has reduced their size in light of further
information and analysis provided in CARB’s October 15 letter.  While
EPA has reduced the size of these areas, they still include the
violating monitors and the contributing sources in nearby areas and they
are still larger than those recommended by the State of California.

Several factors led EPA to recommend a larger PM2.5 nonattainment area
than recommended by California.  A significant consideration in
expanding the nonattainment areas recommended by California was that the
State relied on future mobile source controls at a statewide level to
address NOX emissions and, therefore, discounted mobile sources as an
important consideration in their analysis.  During the designation
process, as required by section 107 of the CAA, EPA determined
violations of the 2006 24-hour fine particulate NAAQS based solely on
the most recent three complete years of certified monitoring data.  EPA
set boundaries based on available data and analysis that best represents
present-day conditions, and not on projected emissions reductions that
may occur after area designations areas are finalized.  Section 107
requires EPA to designate all areas within three years of promulgation
of a new NAAQS, and to designate as nonattainment any area that violates
or contributes to a nearby area that violates a NAAQS.  The statute is
written in the present tense and thus EPA believes it can only base
designations on controls that are in place and federally enforceable by
the effective date of final designations.  Based on speciation data
provided by CARB, organic carbon and nitrates were identified as the
major components of PM2.5 where violations occurred, which were
attributed to residential woodburning and mobile sources, respectively.
Therefore, EPA’s nonattainment areas were intended to capture the
extent of these particular sources which could be contributing to
observed violations of the PM2.5 standard.

While EPA agrees with CARB that there are more localized impacts from
residential woodsmoke emissions, as explained above, it does not agree
that the contribution of mobile sources can be discounted based on the
prospect of future controls.  EPA views mobile source emissions as a
significant component of regional PM2.5 levels in the Sacramento Valley
and elsewhere.  It appears that the combination of this regional
pollution and local woodsmoke emissions in certain areas leads to
violations of the PM2.5 standard, particularly during stagnant
conditions.  Considering this, EPA looked at the location of the
violating monitors and the sources of both woodsmoke and nitrates to
determine the appropriate boundaries, which are larger than what
California recommended.

Chicago, IL-IN

The State of Indiana

Indiana:

The monitors in the Chicago area located closest to the Indiana State
line … that should be more directly impacted by emissions from Lake
and Porter County sources, are monitoring attainment of the 24-hour
standard.”  Indiana feels that if it contributed to the violations in
Illinois, the monitors near the State boundary would record higher
concentrations.  Indiana feels the violating monitors in Illinois are
“most likely affected by localized emission sources.

EPA Response:

The fine particulate concentration in an area and thus the monitors
measuring the concentration are influenced by emissions from a variety
of sources.  The concentration is the result of complex atmospheric
chemistry that forms fine particulate from precursors and can change the
distribution of directly emitted particulate.  Fine particulate
pollution is the result of emissions from local, urban, and
regional-scale emissions.  The emissions from a county do not have to
cause a violation to be considered as contributing to a violation.
Emissions from the area counties can increase the PM2.5 concentration
across the area which adds to regional background concentration.
Emissions from some sources or clusters of sources can further raise the
local PM2.5 concentration which results in a monitor or some area
monitor recording a violation.  A county does have to cause the “last
microgram or few micrograms” that cause a monitor to record a
violation.  It just needs to add to the total concentration to be
considered contributing.  Lake and Porter Counties, Indiana have the
second and fourth most direct PM2.5 emissions in the 10-county
nonattainment area.  Lake County, Indiana has the second highest
emissions in the area of the two main precursors, SO2 and NOX.  The SO2
and NOX emissions from Porter County are higher than the emissions from
other Chicago area counties.  The level of PM2.5, SO2, and NOX emissions
from Lake and Porter Counties, Indiana are high enough to contribute to
the violations in the Chicago nonattainment area.

Indiana:

Indiana requested Lake and Porter Counties be designated as a
nonattainment area separate from the Illinois portion of the Chicago
area.  Indiana notes that seven of the 18 PM2.5 monitors in the area
violated the PM2.5 standards for 2005-2007, the most recent complete
period.  Indiana feels that “it is unnecessary to extend the
restrictions of a nonattainment area outside the Chicago area.

EPA Response:

EPA agrees that it is not necessary to extend the nonattainment area
beyond the Chicago metropolitan area.  In fact, EPA designated six
counties within the Chicago combined statistical area as attainment
including Jasper, LaPorte, and Newton Counties in Indiana.  Indiana’s
comments does suggest it feels that Lake and Porter Counties, Indiana
are not a part of the Chicago area.  EPA has information that shows
these counties are an integral part of the Chicago area.  Commuting data
shows that nearly 42,000 workers commute from Lake County, Indiana into
Illinois and more 6,500 worker commute to Illinois from Porter County.
Over 13,000 workers go into Lake and Porter Counties from Illinois.  The
Chicago PM2.5 (1997 standards) and the ozone nonattainment areas both
include Lake and Porter Counties, Indiana.  Lake and Porter Counties are
also included the Chicago combined statistical area as defined by the
Census Bureau.  EPA has concluded that Lake and Porter Counties in
Indiana are an integral part of the Chicago area and thus should not be
treated as a separate nonattainment area.  Illinois and Indiana should
work together to develop a plan to bring the entire area into
attainment.

Indiana:

Indiana provided information on emissions from Lake and Porter Counties.
 It listed the PM2.5 and NOX emissions from the Indiana portion of the
Chicago area and compares them to the emissions from the entire area.
Indiana noted that “most of the area in Lake and Porter Counties is
urban” and that the two counties emit 66.3 percent of NOX and 75.3
percent of PM2.5 emissions in the Indiana portion of Chicago.  Indiana
included a chart with the 2002, 2010, 2020, and 2030 emissions of PM2.5
and NOX for the Illinois portion, the Indiana portion, and the Chicago
area.  The chart shows the Indiana portion responsible for about 15
percent of the Chicago area emissions in 2002.  That amount decreases in
the future projections.

EPA Response:

EPA agrees that most of the emissions in the Indiana portion of the
Chicago area are from Lake and Porter Counties.  That is why EPA
included Lake and Porter Counties in the Chicago nonattainment area and
designated Jasper, LaPorte, and Newton Counties as attainment.  It is
not clear where the Indiana emissions data provided by the State is
from.  EPA used emission date from the 2005 National Emissions Inventory
is assessing areas for the designations under the 2006 PM2.5 standards.
The 2005 emissions from Lake and Porter Counties of PM2.5 and NOX are
much higher than the 2002 Indiana portion totals the State provided.
Indiana did not list SO2 emissions on it chart.  EPA also concluded that
the PM2.5, NOX, and SO2 emissions from Lake and Porter Counties
contribute to the violations being monitored in the Chicago area.  The
future reductions projected on the table are impressive.  As it is a
projection, EPA cannot use this information in designation decisions.

Indiana:

Indiana stated that, “Lake and Porter Counties are subject to the most
stringent group of emission controls within the State of Indiana.  This
collection of permanent and enforceable controls is equally as stringent
as those applied elsewhere in the Chicago MSA and in some cases, more
stringent.

EPA Response:

EPA commends Indiana for applying strict controls to its sources in Lake
and Porter Counties.  Reducing emissions throughout the Chicago area
helps improve the air quality and move the area closer to attaining the
air quality standards.

Indiana:

Indiana notes that vehicles registered in Lake and Porter Counties are
subject to reformulate gasoline and vehicle inspection and maintenance
programs.  Indiana tests all 1976 model year and newer vehicles in its
program.  Indiana states that Illinois does not test pre-1996 model year
vehicles in its program.  Indiana feels that the Illinois program misses
“high-emitters” by exempting pre-1996 vehicles.

EPA Response:

The Illinois inspection and maintenance program and others around the
nation discontinued testing pre-1996 model year vehicles because there
are few of these vehicles left in operation.  Even though the vehicles
do emit more, the decreasing number of vehicles remaining on the road
means that the emission reductions from testing older vehicles are
small.  A large amount of mobile source emissions come from sources
other that cars and light trucks, such as heavy trucks.  The Lake and
Porter Counties mobile source emissions from non-road sources had higher
PM2.5 and SO2 and similar NOX emissions as the on-road inventory (2005
NEI data).

Indiana:

NOX emissions within Northwest Indiana area are projected to decline by
almost 42 percent between 2005 and 2020.

“[The] [e]mission reduction benefits from federal rules are factored
into the changes.  …Further, due to implementation of the NOX SIP Call
across the eastern Unites States, fine particles and precursors for fine
particles emissions entering this area are also decreasing.”

EPA Response:

As Indiana stated, the benefits of federal rules cutting emissions of
PM2.5 and its precursors are beginning to benefit the Chicago area and
other areas throughout the nation.  National emission reduction program
help decrease the regional background concentration of PM2.5.  However,
such future projected emissions reductions do not negate the obligation
under section 107(d) for EPA to designate as nonattainment those areas
that are violating, or contributing to violations of, the 200 PM2.5
NAAQS based on the most recent three years of data.  Congress amended
section 107(d) to eliminate provisions that previously directed EPA to
base designations for selected NAAQS based on projected future
attainment status (e.g., for SO2).  Section 107(d) is now phrased in the
present tense, and EPA interprets this provision to require designations
based upon current facts, not some projected future facts.  To the
extent that current federal programs will result in near term emission
reductions, these will be reflected in the nonattainment area SIPs
developed for these areas, and thus will play an important role in
helping these areas to attain the NAAQS as expeditiously as practicable.
 They are not, however, a basis for ignoring current violations or
contribution to violations.

Indiana:

Over 80 percent of Lake County’s workforce is employed within the
county.  Over 60 percent of Porter County’s workforce is employed
within the county, and the majority of those employed outside the county
commute to Lake County, and not Chicago.  Therefore, the portion of
commute traffic with Chicago from Lake and Porter Counties is
insignificant.  Indiana adds, “gasoline-powered commuter vehicles are
insignificant emitters of sulfates, which is the driving precursor for
violating sites in Northeast Illinois.”

EPA Response:

The commuting data helps show a link between the Illinois and Indiana
portions of the Chicago area.  Commuting data shows that nearly 42,000
workers commute from Lake County, Indiana into Illinois and more 6,500
worker commute to Illinois from Porter County.  Over 13,000 workers go
into Lake and Porter Counties from Illinois.  There are also nearly
22,000 Porter County workers commuting into Lake County, Indiana.  The
number of workers commuting between the Illinois and Indiana portions of
the area is large even if the percentages are not because of the large
populations of the area counties.  EPA does not agree that SO2 is  the
“driving precursor” in an area because the direct PM2.5 emissions
and all PM2.5 precursor emissions in an area cumulatively add to the
ambient PM2.5 concentration in a violating area.  The PM2.5
concentration is not the result of one precursor solely.  Reductions of
direct emissions or in any precursor will benefit the air quality.
Details about appropriate control strategies for any area, including the
evaluation of which sources of which pollutants to control, consistent
with the requirements of section 172, in order to attain the NAAQS
expeditiously is among the questions the State and EPA will resolve
during the development of the nonattainment area SIP for such area.

Indiana:

Indiana further analyzed the days that the monitoring levels in the
Chicago area were substantially higher than the next highest monitor
value in the region on that date, as shown below.  Indiana then compared
those days to wind data to determine the direction of prevailing winds
during those days.  …  The comparison for the highest monitor value
days for the Chicago monitors show winds from different directions with
winds predominately from the east, south, west, and southwest.  Based on
this sample of high fine particle monitor value days, while emissions
from all surrounding areas may have small impacts, it is evident that
there is no significant impact from Northwest Indiana.  … Further
analysis of high fine particle days included a back trajectory analysis.
 A back trajectory measures the winds at different heights in the
atmosphere to determine from what locations pollutants may be picked up
and transported to an area.

EPA Response:

Indiana examined the meteorology on only three days, October 27, 2004,
February 3, 2005, and January 23, 2006.  The conclusion that emissions
from the Indiana portion of the area do not contribute to violations
cannot be reasonably reached using such a small data set.  As the PM2.5
concentration in an area involves complex atmospheric reactions of the
precursor pollutants that blend with direct PM2.5 emissions, one cannot
say the wind drew emissions from a downwind area to create the
concentration being measured at a monitor.  Therefore, EPA does not
consider Indiana’s hypothesis to be proved true from the limited
sample it analyzed.

Indiana:

Culpability analysis prepared and submitted by Indiana to EPA on April
3, 2008 demonstrates that not only are Lake and Porter counties not
culpable for monitored violations in northeast Illinois, counties
designated as attainment in southeast Wisconsin are more culpable to
measured levels in northeast Illinois than are Lake and Porter counties.
 Analysis of trajectory information for four days in which
concentrations in Chicago were significantly higher than elsewhere
indicated that three of these four days had winds from directions other
than from Northwest Indiana.

EPA Response:

On April 3, 2008, Indiana submitted a request that EPA redesignate Lake
and Porter Counties to attainment for the annual PM2.5 standard; this
submittal included culpability analysis for annual average PM2.5 for
various sites in the Chicago-Northwest Indiana area.  Indiana provided a
synopsis of this analysis as Appendix D of its comment letter to its
24-hour PM2.5 designations submittal of May 30, 2008.  EPA disagrees
with this comment for the following reasons.  First, this is not the
proper forum for addressing culpability for annual average PM2.5
concentrations.  This analysis of culpability for annual average PM2.5
concentrations does not clearly address contributions to 24-hour PM2.5
concentrations.  Second, based on 2005-2007 air quality data, Lake
County, Indiana, now has a violating monitor for the 24-hour standard.
EPA’s analysis concludes that adjacent Porter County, Indiana (24,000
tons SO2; 30,000 tons NOx), is contributing to this violation.  Third,
the limited information presented in this analysis does not clearly
demonstrate that Lake and Porter Counties do not contribute to other
violating monitors in the Chicago nonattainment area.  In fact,
Indiana’s analysis is reasonably consistent with EPA’s findings,
concluding not that Lake and Porter counties contribute on every day
with high concentrations in Chicago, but that the winds carry
significant emissions from those counties toward violating monitors in
Illinois with sufficient frequency to warrant a determination that Lake
and Porter counties contribute to violations in Chicago.

EPA Response to Additional Modeling Results Referenced in Indiana
Comment Letter:

Indiana Department of Environmental Management (DEM) states that the
fine particle contribution from Indiana’s portion of the Chicago
nonattainment area (Lake and Porter counties) is less than 1.0 μg/m3
and that these results verify that Lake and Porter counties do not
contribute significantly to measured values in Illinois.

μg/m3 contribution for the annual standard of 15 μg/m3 is clearly a
significant contribution and for a short term standard like the 24-hour
PM2.5 NAAQS.  This contribution could be much higher when monitors in
the southwest region of Lake Michigan indicate a violation of the
standard.  This contribution would also be larger if current year
emissions during 2005-2007 were used in the modeling analysis since
mobile source emissions are higher and other projected 2012 controls
would not be in place.  For these reasons, the modeling submitted by
Indiana is not appropriate for the purpose of designating the Chicago
24-hour PM2.5 nonattainment area, but clearly shows a significant
contribution to Chicago.

Chico, CA

CARB:

The only violating monitor in Butte County is located in the City of
Chico, which has a 2007 Design Value of 55 μg/m3.  Chico, the largest
urban area in Butte County, has a population three-to-five times other
areas in the county.  Based on the localized nature of the primary
emission contribution to winter PM2.5, CARB considers the urban area of
Chico an appropriate nonattainment boundary for PM2.5.

A diurnal analysis of concentrations at Chico and Gridley, during Chico
exceedance days, highlights the localized nature of the PM2.5 pollution
episodes.  The nighttime increases at Chico, the result of residential
wood burning, are not reflected at the monitoring site at Gridley.  The
majority of exceedance days occur during periods of stagnant or low
wind, keeping pollutants close to the emission sources.

EPA Response:

CARB has recommended only the City of Chico as the nonattainment area of
Butte County.   There are a number of reasons why EPA disagreed with
this recommendation.  In developing the boundaries for Butte County, EPA
considered several factors contained in Agency guidance for PM2.5
designations, including air quality data, emissions data, population
data, commuting patterns, geography, topography, meteorology and other
information such as CES scores, chemical speciation data, and wintertime
inversion data.  EPA also considered information provided by the State
of California such as information on residential wood burning.

Exceedances of the PM2.5 standard most often occur in Chico during the
winter months and speciation data suggest that residential wood burning
and mobile source emissions are the most important sources.  Area source
data show that residential wood burning is the dominant source of PM2.5
and, therefore, could be linked to PM2.5 exceedances measured in Chico.
This data also suggests that other population centers in Butte County
could experience high PM2.5 levels as a result of residential wood
burning.  With respect to mobile sources, the Butte County inventory
shows significant mobile source emissions which can also contribute to
regional PM2.5 pollution.  Since both sources are associated with the
population centers, EPA has determined that the nonattainment area in
Butte County should include Chico, Paradise and Oroville, and Gridley.

The area recommended by California, namely the city limits of the City
of Chico, does not include all of Chico’s urban population nor does it
include other population centers in Butte County, including Paradise,
Gridley and Oroville.  The total population of Butte County is 214,000.
According to the 2000 US Census, the population of Chico was 59,444, the
population of Paradise was 26,408 and the population of Oroville was
13,004.  Moreover, the City of Chico has been experiencing significant
growth, growing from 59,954 to 71,728 between 2000 and 2006, and we
would expect future growth to continue extending beyond the existing
city boundaries.

Finally, topography is considered to be an important factor given that
inversion layers during the winter, when PM2.5 exceedances typically
occur, can contribute to higher pollution levels in the Sacramento
Valley.  In addition to affecting the City of Chico, these conditions
are expected to create similar pollution conditions in areas with large
populations and commuting patterns and, thereby, provide further reason
to expand the nonattainment boundary beyond the City of Chico.

Cincinnati-Hamilton, OH-KY-IN

The State of Kentucky

Kentucky:

To have Boone County, Campbell County, and Kenton County designated
nonattainment would invoke additional, substantial, unnecessary
requirements on local government planning agencies with little or no
benefit to the area.  Substantial local emission reductions from Boone
County have already occurred, or will have occurred well before
attainment dates for this standard.  Drastic emission reductions are
scheduled to occur in the mobile sector throughout the next several
years that will greatly impact pollutant levels in the area.  Couple
these changes with those anticipated by the CAIR, or its replacements,
provisions which will further reduce SOX and NOX emissions within the
region, and the air monitoring data demonstrating attainment of the
PM2.5 standard, and the result should be that these counties be
designated attainment for the PM2.5 standard.

EPA Response:

EPA’s 9-factor analysis has determined that emissions from Boone
County, Campbell County, and Kenton County contribute to violations in
violations in nearby Hamilton and Butler counties, Ohio, and that it is
appropriate to include these counties in the Cincinnati-Hamilton
nonattainment area.  EPA believes that consideration of all 9 factors
compels designating these counties nonattainment, consistent with the
existing nonattainment boundary for the annual PM2.5 standard.  As
stated in Section V, EPA determined the existence of violations of the
2006 24-hour fine particulate NAAQS based solely on the most recent
three complete years of certified monitoring data.  EPA is setting
boundaries based on available current data and analyses that best
represent present-day conditions, and not on projected emissions
reductions that may occur after designation areas are finalized.   This
is consistent with the explicit provisions of section 107(d), that
define “nonattainment” to be those areas that violate or contribute
to violations of the NAAQS.

While EPA acknowledges that local emission reductions have been and
continue to be achieved in the area, we are considering only the current
emission controls in place for designation purposes.  Any local emission
reductions in the area that occur before the required attainment date
will help further improve air quality and should be included in the
attainment plan.  However, the uncertainty of future emission
reductions, and also any future new or expanded sources, renders
assumptions about them unsuitable for use in establishing nonattainment
area boundaries.

μg/m3 for the 2005-2007 period indicates that considerable emission
reductions are still needed for the area to attain.  Analysis of
chemical composition data for Cincinnati 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) also are key
contributors to the PM2.5 mass on days exceeding the 24-hour PM2.5
standard.  In addition, these data show that nitrate (formed from NOX
emissions) can also be an important component on high days in the cool
season.  For example, nitrate was 44 percent of PM2.5 mass on a cool
season high day in the 2005-2007 period.  These data indicate that the
same source categories that contribute to violations of the annual
standard also contribute to exceedances of the 24-hour standard.  EPA
concludes that counties that were designated as having emissions sources
contributing to fine particle concentrations which continue to exceed
the 1997 standards also contribute to fine particle concentrations on
the highest days.  This is another reason that EPA believes that Boone,
Kenton, and Campbell Counties should be included in the nonattainment
area for the 2006 24-hour standard as well.

The State of Kentucky makes the following points as additional rationale
for excluding Boone, Kenton, and Campbell Counties from the Cincinnati
nonattainment area.

Kentucky:

Kentucky believes that EPA’s use of the contributing emissions scoring
approach was skewed.  A review of actual percentages of emissions
contributions to the area shows that Boone, Kenton, and Campbell
Counties do not have the potential to contribute to PM2.5 levels within
the region.

EPA response:

The CES is an initial screening tool used to determine potential
nonattainment area boundaries which can then be modified using
additional information provided by the State or other sources.  EPA has
recommended other types of information for this purpose through guidance
which could be considered in the final decision.

The CES for Boone, Kenton, and Campbell are lower than those for other
contributing counties (Clermont, OH; Dearborn, IN) in the area.
However, EPA does not find that emissions from these counties (Boone:
5383 tons of SO2, 10852 tons NOX, and 1600 tons direct PM2.5; Kenton:
1300 tons SO2, 6316 ton NOX, 537 tons PM2.5; Campbell:  730 tons SO2,
4231 tons NOX, 412 tons PM2.5) are without the potential to contribute
to PM2.5 in the region.  One key source of emissions located in Boone
County is the Cincinnati-Northern Kentucky International Airport.

Kentucky:

Contributions from commuters and vehicle miles traveled in Boone,
Kenton, and Campbell Counties have been shown to have no potential to
impact PM2.5 levels within the region when compared to the levels from
other counties and therefore should not be used to determine
nonattainment status for this county.

EPA Response:

EPA believes that commuting and vehicle miles traveled data are an
important factor in the inclusion of these counties in the nonattainment
area.  Boone County has 1 million VMT and 43,000 commuters annually;
Kenton County has 1.6 million VMT and 74,000 commuters annually; and
Campbell County has 1 million VMT and 42,000 commuters annually.  EPA
has not suggested any threshold of significance for VMT and commuting,
but EPA believes these VMT and commuting data indicate that these
counties are an integral part of the Cincinnati-Hamilton urban area and
that vehicle emissions from these counties are likely contributing to
elevated fine particle concentrations on high days.

Kentucky:

The populations of Boone, Kenton, and Campbell Counties are not
significant enough to have the potential to impact PM2.5 levels in the
region.  Each county’s population represents a small percentage of the
population of EPA’s proposed nonattainment boundaries.

EPA Response:

The 2005 population of Boone County is 106,000; Kenton County is
153,000; and Campbell County is 87,000.  All three have a moderate level
of population and population density when compared to other contributing
counties in the area and across the country.  Together, the population
of the northern Kentucky counties is substantial at around 350,000.  As
noted above, the residents of these counties are responsible for a
substantial amount of vehicle miles traveled and commuting in the
Cincinnati area, and EPA believes this contributes to PM2.5 NAAQS
exceedances in the area.

Kentucky:

There are no violating monitors in Boone, Kenton, or Campbell County.

EPA Response:

μg/m3; Butler, OH with design value of 38 μg/m3).

Kentucky:

Duke Energy East Bend Station Unit 2, which is located in Boone County,
Kentucky, is an electric power generating station consisting of one
pulverized coal-fired, dry bottom, wall-fired boiler.  The boiler (Unit
02) has an input capacity of 6313 mmBtu/hr.  Unit 2 is equipped with an
electrostatic precipitator (ESP), FGD unit, low nitrogen oxide burners
and a SCR unit.  As can be seen in the table on page 11 of Kentucky’s
comment letter, these controls provide for significant reductions in
precursor PM2.5 pollutants.  Although at this point in time it is
uncertain what reductions can be attributed to CAIR or its replacement,
it is certain that some manner of control similar to CAIR will be
implemented.  This will further reduce these emissions since the SCR
should be operated year-round instead of only during the ozone season.
Kentucky’s NOX SIP Call regulations remain in effect and if CAIR
continues to be in limbo will cover the 2009 allocation timeframe.

EPA Response:

See the overview response to comments on power plant issues, located at
the beginning of Section IV.

EPA acknowledges that the East Bend Station in Boone County has emission
controls in place for both SO2 and NOX.  Emissions in 2007 were 2452
tons of SO2 and 5563 tons of NOX.  However, EPA has not included Boone
County in the nonattainment area solely on the basis of the presence of
the East Bend plant.  Based on the amount of emissions from the plant,
the geographic location of the plant, and the meteorological data for
this area, and the speciated data for this area indicating that such
emissions play a role in the formation of the ambient PM2.5 in this
area, EPA has concluded that this source still contributes to violations
in the area, as that term is intended in section 107(d).  Therefore, it
is appropriate that the State and EPA will evaluate the source in the
nonattainment area SIP development process.

EPA notes that reductions required by CAIR, or any replacement rule
under section 110(a)(2)(D) or section 126, to reduce interstate
transport would not be in lieu of the requirements under section 172 for
nonattainment areas.  Thus, additional controls may also be necessary
for local attainment needs.  Section 110(a)(2)(D) and section 126
address a different issue than section 107(d).

A number of other factors in EPA’s decision for inclusion of Boone
County are explained in the responses above.

Kentucky:

The air monitoring data demonstrates attainment of the PM2.5 Standard.

EPA Response:

Although there are no ambient monitors in Boone and Campbell Counties
and the ambient monitor in Kenton County currently shows attainment,
there are several violating monitors in nearby Hamilton County, which
has a design value of 41 (g/m3, based on 2005-2007 data.  Analysis of
all additional data described in the TSD indicates these counties are
contributing to the violating monitor.  Section 107 requires designation
of areas that, although not they themselves violating, are contributing
to nearby nonattainment.

The State of Indiana

Indiana:

AEP-Tanners Creek (in Dearborn County) will be installing Selective
Non-Catalytics Reduction (SNCRs) on three of its four units, with
operation to begin in mid-2009.  This will achieve an additional 30
percent reduction in NOX.  Indiana believes that emissions from Dearborn
County do not affect the downwind area’s ability to attain the 24-hour
standard.  EPA must substantiate its assumption that this township is
contributing to upwind monitored violations with source apportionment
analysis and a model-based culpability analysis.

EPA Response:

See the overview response to comments on power plant issues, located at
the beginning of Section IV.

EPA disagrees with Indiana regarding its claim that emissions from the
Tanner’s Creek power plant located in the existing partial county
nonattainment area in Dearborn County do not contribute to PM2.5
concentrations in Cincinnati.  EPA’s analysis has evaluated emission
levels, speciation data, evidence from the pollution rose and other
meteorological data for this area that there is contribution from the
direction of this source to the rest of the nonattainment area, and the
level of emission controls on the source.  The Tanner’s Creek plant
has four units, none of which have a scrubber or SCR.  Emissions in
2005-2007 were substantial:  in the range of 33,000 to 46,000 tons of
SO2 and about 9000 tons NOX.  The plant is located close by, about 17
miles from the closest violating monitor.  EPA is assessing current
contributions to current violations, regardless of whether emissions may
decline in the future, consistent with the requirements of section
107(d).  Indiana does not address SO2 emission control at this plant;
SO2 emissions are currently relatively high, and EPA expects SO2
emissions from this facility to remain relatively high

Cincinnati is an existing PM2.5 nonattainment area which has not
attained the 1997 standards.  Its 2005-2007 annual design value is still
well above the standard at 17.3 μg/m3, indicating that considerable
emission reductions are still needed for the area to attain.  Analysis
of chemical composition data for Cincinnati 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) also are key
contributors to the PM2.5 mass on days exceeding the 24-hour PM2.5
standard.  In addition, these data show that nitrate (formed from NOX
emissions) can also be an important component on high days in the cool
season.  For example, nitrate was 44 percent of PM2.5 mass on a cool
season high day in the 2005-2007 period.  These data indicate that the
same source categories that contribute to violations of the annual
standard also contribute to exceedances of the 24-hour standard.  EPA
concludes that counties that were designated as having emissions sources
contributing to fine particle concentrations which continue to exceed
the 1997 standards also contribute to fine particle concentrations on
the highest days.  This is another reason that EPA believes that
Dearborn county should be included in the nonattainment area for the
2006 24-hour standard as well.

EPA also disagrees with the commenter’s supposition that EPA must
“substantiate its assumption that this township is contributing to
upwind monitored violations with source apportionment analysis and a
model-based culpability analysis.”  Nothing in section 107(d) requires
that a modeling analysis be conducted to determine a “contribution”
and to make a nonattainment designation.  The best available evidence
indicates that Dearborn County contributes to violations in the
Cincinnati area.

Clarksville, TN-KY

The State of Tennessee

Tennessee:

The State of Tennessee believes that Montgomery County should be
classified as “unclassifiable” by the December 18, 2008, deadline,
and that monitoring data support the State’s declaration that
Montgomery County will measure attainment.  The State of Tennessee
claims that ambient PM2.5 data for 2007 may be skewed by the impact of
Georgia and Florida wildfires during 2007.  Data for 2008 will be
certified before the February 2009 deadline to have relatively low
readings for 2006-2008 considered.

The State of Tennessee believes Stewart County and Humphreys County
should be classified as “attainment.”  However, if EPA designates
Humphreys and Stewart Counties as nonattainment, the State believes EPA
should designate only significantly contributing portions of Humphreys
and Stewart Counties.  The State notes that EPA has previously concluded
that a partial area of a county may be designated nonattainment if that
partial area includes the emissions point of concern.  Tennessee
believes this same situation exists for both counties of Humphreys and
Stewart, if both are non-attaining.  The State of Tennessee proposes as
boundaries for the partial areas census block groupings that include the
Tennessee Valley Authority (TVA) New Johnsonville Fossil Plant in
Humphreys County and TVA Cumberland Fossil Plant in Stewart County.

EPA Response:

EPA finds that ambient monitoring data for Montgomery County is complete
for 2005 – 2007 and therefore there is no basis to designate the
county “unclassifiable” at this time.  Therefore, EPA must designate
Montgomery nonattainment based on valid data for 2005 - 2007.

EPA acknowledges Tennessee has proposed as boundaries for the partial
areas census block groupings that include the TVA New Johnsonville
Fossil Plant in Humphreys County and TVA Cumberland Fossil Plant in
Stewart County.  EPA agrees with the proposed census block boundaries
and is designating only the contributing portions of Humphreys and
Stewart Counties.

EPA acknowledges that SO2 and NOX emissions have declined at TVA
Cumberland Fossil Plant and TVA Johnsonville Fossil Plant.  However, EPA
has determined that, even at current reduced emission levels, the
surrounding partial-county areas should be designated as nonattainment
based on their contribution to the violating monitor in nearby
Montgomery County.

Tennessee:

The primary sources of concern are two coal-fired power plants: the TVA
New Johnsonville Fossil Plant in Humphreys County and TVA Cumberland
Fossil Plant in Stewart County.  The proposed boundaries for the partial
areas that include these power plants are census block groupings as
listed in Table 1 and mapped in Attachment 1 (Humphreys County) and
Attachment 2 (Stewart County) of Tennessee’s comment letter.

If EPA determines that Humphreys and Stewart Counties must be designated
as nonattainment, the EPA should designate only the census block
groupings indicated in Table 1 and the attachments.  At each of the TVA
power plants, SO2 and NOX emissions continue to decline, and any further
control methodologies would be federally enforceable through operating
permit conditions and continued NOX SIP Call provisions within Tennessee
Air Pollution Control Regulations.  As stated in TVA's letter to EPA,
dated October 1, 2008, TVA Cumberland Fossil Plant in Stewart County has
two combustion units with each unit's emissions controlled with low-NOX
burners, SCRs, ESPs, and wet limestone scrubbers.  Also, the TVA
Johnsonville Fossil Plant in Humphreys County continues to utilize
electrostatic precipitators and selective non-catalytic reduction as
emission controls on all ten units.

EPA Response:

See the overview response to comments on power plant issues, located at
the beginning of Section IV.

The CAA requires that a nonattainment area must include not only the
area that is violating the standard, but also nearby areas that
contribute to the violation.  Thus, for each monitor or group of
monitors that indicate violations of a standard, EPA is establishing
nonattainment boundaries that cover a sufficiently large area to include
both the area that violates the standard and the areas that contribute
to the violations.  The Clarksville area includes the TVA New
Johnsonville Fossil Plant in Humphreys County (2007 emissions: 65,000
tons SO2 and 19,000 tons NOX) and TVA Cumberland Fossil Plant in Stewart
County (2007 emissions: 17,000 tons SO2 and 33,000 tons NOX).  The New
Johnsonville Plant currently has no scrubbers or SCR installed on its 10
units.  The Cumberland Plant, while relatively well-controlled, still
has high SO2 and NOX emissions and is located in close proximity to the
violating monitor.  EPA has concluded that these sources do factually
contribute to the violations in the nearby area, notwithstanding the
current level of control at the Cumberland plant.  Under section 107(d),
EPA believes that the level of control of emissions from a source is a
relevant inquiry in the designations process to assure that EPA and the
State are using up to date and accurate emissions information.  EPA does
not believe that the level of control alone should be used as a basis to
exclude from a nonattainment area a source that is otherwise deemed to
be contributing to the violations based upon information such as its
amount of emissions, geographic location, and meteorological connection
to the nearby violating area.

The State of Kentucky

Kentucky:

To have Muhlenberg County designated nonattainment would invoke
additional, substantial, unnecessary requirements on local government
planning agencies with little or no benefit to the area.  Substantial
local emission reductions from Muhlenberg County have already occurred,
or will have occurred well before attainment dates for this standard.
Drastic emission reductions are scheduled to occur in the mobile sector
throughout the next several years that will greatly impact pollutant
levels in the area.  Couple these changes with those anticipated by the
CAIR, or its replacements, provisions which will further reduce SOX and
NOX emissions within the region, and the air monitoring data
demonstrating attainment of the PM2.5 Standard, and the result should be
that these counties be designated attainment for the PM2.5 Standard.

EPA Response:

EPA commends Muhlenberg County for local emission reductions that have
been and continue to be achieved.  However, EPA’s 9-factor analysis
has determined that emissions from Muhlenberg County contribute to
nonattainment in Montgomery County, Tennessee, and that it is
appropriate to include this County in the Clarksville nonattainment
area.  EPA believes that consideration of all nine factors compels
designating this County nonattainment, in particular the boundaries
surrounding the TVA Paradise Power Plant and the Kentucky Utilities
Green River Power Plant.  As stated in Section V, EPA determined
violations of the 2006 24-hour fine particulate NAAQS based solely on
the most recent three complete years of certified monitoring data.  EPA
is setting boundaries based on available data and analysis that best
represents present-day conditions, and not on projected emissions
reductions that may occur after designation areas are finalized.

The State of Kentucky makes the following points as additional rationale
for excluding Muhlenberg County from the Clarksville nonattainment area.

Kentucky:

Kentucky believes that EPA’s use of the contributing emissions scoring
approach was skewed.  A review of HYSPLITS on days of high monitor
readings shows that Muhlenberg County does not have the potential to
contribute to PM2.5 levels within the region.

EPA Response:

EPA disagrees with Kentucky that the HYSPLIT analysis is more refined
than the CES.  First, the HYSPLIT trajectories submitted by the State
show only days between 2004 and 2006.  Since Clarksville, TN violated
the 24-hour NAAQS with data collected from 2005 to 2007, data from that
three-year period were used to calculate the CES for the area.
Furthermore, EPA trajectories were calculated for each “high” day at
three hour intervals across the day with each of the eight start times
starting at four heights at or below the mixing height.  They were
calculated at specific hours during which the air would have arrived at
the site during the high day.

Second, the trajectories presented by Kentucky all arrive at the site
six hours after the end of the high day.  This is not as accurate in
determining whether air was passing over a contributing area on the
actual day of the exceedance.  Air could have been coming from other
directions and over other land areas during the high day in question
which would not be reflected in trajectories arriving at the site after
the high day.  EPA began trajectories at or below the mixing height in
all instances.  Only those points along the trajectory that remained
within the mixing layer were used in computing the CES.  It is not
certain whether the three starting heights the State used for their
backward trajectories were started at or below the mixing height.  Also,
since EPA started trajectories at four starting heights within the
mixing layer for eight different starting times, there were a total of
32 trajectories to examine to see if the air parcels followed consistent
paths throughout the day.  This level of robustness was not captured by
the State whose examples show several days where the three trajectories
that were run do not consistently follow the same path to Montgomery
County, TN.  When examining backward trajectories started at staggered
starting times across the “high” day and at multiple starting
heights, there are days when the trajectories consistently pass over
Muhlenberg County on their way to the Montgomery County, TN.

Lastly, the results of the State run trajectories are plotted on maps
with only State boundaries given.  This provides no sense of spatial
resolution as to where Muhlenberg County is located in relation to the
trajectory paths.

Kentucky:

TVA Paradise, which is located in Muhlenberg County, is a facility that
consists of three cyclone-furnace coal-fired boilers.  All three
coal-fired boilers are equipped with staged overfire air and selective
catalytic reduction modules for nitrogen oxides emission control.
Boiler Units 1 and 2 are equipped with venturi-type limestone slurry
flue gas desulfurization scrubbers for SO2 and particulate control.
Boiler Unit 3 is equipped with an electrostatic precipitator and a wet
limestone FGD scrubber for particulate and SO2 control.  The Unit 3 FGD
scrubber that came online in 2006 has significantly reduced the TVA
Paradise SO2 emissions by 49,704 tons per year (tpy) given the Unit 3
2005 emissions (53,519 tpy) compared to the Unit 3 2007 emissions (3,815
tpy).  TVA Paradise’s total SO2 emissions in 2005 were 84,401 tpy
while in 2007 its SO2 emissions had decreased to 33,818 tpy due to the
addition of the Unit 3 scrubber.  In addition, although not considered
as BART since TVA had previously related to the Kentucky Division of Air
Quality (KYDAQ) its intent to install controls to mitigate SO2 emissions
at TVA Paradise, TVA plans to install hydrated lime injection controls
on TVA Paradise Units 1-3 at to address SO2 emissions and improve
visibility at Class I areas.  Given the TVA Paradise existing emission
controls that are in place that have significantly reduced the emissions
at TVA Paradise and additional controls planned, KYDAQ requests that EPA
reconsider its decision and not designate Muhlenburg County as
nonattainment for the 24-hour particulate matter standard (see table on
page 28 of Kentucky comment letter).

EPA Response:

See the overview response to comments on power plant issues, located at
the beginning of Section IV.

In regard to the TVA Paradise plant in Muhlenberg County, an important
consideration for EPA is the level of emissions and contribution from
the plant even with emission controls in place.  As noted in the
State’s comment above, the TVA Paradise plant now has scrubbers and
SCR in place on all three units, yet 2007 emissions were still
substantial: 33,000 tons of SO2, and 43,000 tons of NOX.  In addition to
the TVA Paradise plant, the smaller Green River power plant is also
located nearby in Muhlenberg County.  It has two units without scrubbers
or SCR, and 2007 emissions totaling 22,000 tons of SO2 and 2000 tons of
NOX.  Thus, based on the most recent information available, the two main
sources of emissions in Muhlenberg County account for 55,000 tons of SO2
and 45,000 tons of NOX per year.  In addition, meteorological data
indicate that, on high PM2.5 days, emissions from Muhlenberg County can
be transported to the location of the violating monitor.

Under section 107(d), EPA believes that the level of control of
emissions from the source is a relevant inquiry in the designations
process to assure that EPA and the State are using up to date and
accurate emissions information.  EPA does not believe that the level of
control alone should be used as a basis to exclude from a nonattainment
area a source that is otherwise deemed to be contributing to the
violations based upon information such as its amount of emissions,
geographic location, and meteorological connection to the nearby
violating area.  Based upon this evidence relevant to designations, in
accordance with section 107(d), EPA has concluded that emissions from
Muhlenberg County are contributing to violations in the Clarksville
area.  Thus, these sources will be evaluated by the State and EPA for
additional cortrols, as necessary, in the development of the
nonattainment area plan for this area.  It would be premature to
determine whether such sources are adequately controlled for local
nonattainment area needs at this time.

Kentucky:

Muhlenberg County, a county that is not in the Clarksville MSA and is
geographically separated from Montgomery County by other counties not
proposed as nonattainment, should not be identified as contributing to
such nonattainment status, and therefore should not be included within
the nonattainment boundary for the Clarksville nonattainment area.

EPA Response:

EPA agrees that, like Humphries County, TN, Muhlenberg County is not in
the Clarksville metropolitan statistical area and is geographically
separated from Montgomery County, TN, the site of the violating monitor
by other counties not proposed as nonattainment.  However, based on high
emissions from the power plants in these counties, coupled with
meteorological data indicating wind direction from these counties, EPA
believes sources in Humphries County, TN, and Muhlenberg County do
contribute to the violating monitor in Montgomery County, TN and thus
must be included within the designated nonattainment area.

Kentucky:

EPA’s proposal finds that only two of its nine delineated factors
weigh in favor of designating Muhlenberg County as contributing to
violations of the standard in Clarksville, Tennessee.  The results of
EPA’s assessment of the other seven factors should warrant designation
of Muhlenberg County as attainment.

EPA Response:

Section 107(d)(1)(A)(i) of the Act specifies that a nonattainment area
shall include “any area that does not meet (or that contributes to
ambient air quality in a nearby area that does not meet) the national
primary or secondary ambient air quality standard for the pollutant.”
Based upon emission levels and emissions from electric generating units
in Muhlenberg County, EPA believes Muhlenberg County contributes to
ambient air quality that does not meet the 24-hour PM2.5 NAAQS in the
Clarksville area.  EPA considered all of the nine factors as well as
other data in each area in determining whether the area as a whole
contributed to nearby violating monitors.  If a few factors weighed
heavily in a conclusion that an area contributed, the area would be
included in the nonattainment area even if several other factors weighed
less significantly.  Further, the nine factors are not all equivalent
measures of potential nonattainment, and certain factors could carry
more weight in a given nonattainment area.  Based upon its analysis of
all the data, EPA continues to conclude that these areas should be
included in the Clarksville nonattainment area.

Kentucky:

The air monitoring data demonstrates attainment of the PM2.5 Standard.

EPA Response:

Although there are no ambient monitors in Muhlenberg County, the air
monitoring data demonstrates violating monitors in nearby Montgomery
County, TN, which has a design value of 38 (g/m3, based on 2005-2007
data.  Analysis of all additional data described in the TSD indicates
that Muhlenberg is contributing to the violating monitor.  Section 107
requires designation of areas that, although not violating, are
contributing to nearby nonattainment.

Cleveland-Akron-Lorain, OH

Ohio:

The State of Ohio objected to EPA’s inclusion of Ashtabula Township,
Ashtabula County within the Cleveland nonattainment area for the 2006
24-hour PM2.5 NAAQS.  Among other arguments, Ohio explained that a
significant change of circumstances at the power plant in Ashtabula
Township had drastically reduced emissions at that plant:

“The actual emissions from Cleveland Electric Illuminating power
plant, located in Ashtabula Township (Ashtabula Co.), are less than a
three percent (3 percent) of its allowable emissions.  Besides having
electrostatic precipitators, the plant has only operated one unit since
2002.  In addition, Ashtabula County has insignificant emissions due to
low population and insignificant commuting traffic.  Ohio EPA believes
the above factors demonstrate that Ashtabula is not contributing to the
PM2.5 problems in this nonattainment area.  Moreover, a Cleveland area
windrose (enclosed) shows that, for most of the time, the wind is coming
from the southwest; consequently it is likely that high pollution levels
being detected in Ashtabula County are coming from counties south and
west of this County and not from local sources.”

By letter dated December 9, 2008, Ohio subsequently established that
three of the four boilers at this plant have permanently shut down, that
the permit for operating these boilers has expired, and that these
boilers are now prohibited from operating.  This letter confirmed that
the reductions of emissions from this plant are thus permanent.

EPA Response:

See the overview response to comments on power plant issues, located at
the beginning of Section IV.

EPA has determined that Ashtabula Township does not contribute to
violations of the 2006

24-hour PM2.5 NAAQS in the Cleveland area, and thus has concluded that
it is not necessary to include it within the designated nonattainment
area.  EPA notes that it is not the decrease in emissions in the
abstract that compels this conclusion.  EPA has considered the permanent
decrease in emissions at the source in light of other information
relevant to the designation.  With these shutdowns, the source has
decreased its emissions substantially.  These reductions have already
occurred, and are not future or contingent reductions.  Based on data
from the first six months of 2008, emissions from this plant were about
1500 tons SO2 and 500 tons NOX (equating to estimated annual emissions
of 3000 tons SO2 and 1000 tons NOX).

These smaller amounts of emissions have rendered the source a relatively
small source in the context of the Cleveland area.  These reductions
should be viewed in terms of the meteorological data and other
information relevant to the Cleveland area for the 2006 24-hour PM2.5
NAAQS.  EPA examined back trajectory information for days with high
concentrations at the area’s violating monitors, and found that winds
blow occasionally but less frequently from Ashtabula County on these
critical days than from other area counties.  The pollution rose for a
critical monitor in Cuyahoga County (representative of conditions under
which high concentrations occur in the area) indicates that impacts from
the direction of Ashtabula Township to the violating monitors in
Cuyahoga and Summit Counties are relatively low, compared to
contribution from other areas.  The CES score provides an integrated
consideration of emission levels and frequency of being upwind; the CES
scores for the Cleveland area counties indicated that Ashtabula County
has among the smallest contributions to the Cleveland area.  As noted
elsewhere, EPA believes that the designations for the 2006 24-hour PM2.5
NAAQS must be based on the facts and circumstances of each geographic
area.  Unlike other partial counties within Ohio, EPA believes that the
source in Ashtabula Township is not contributing to violations of the
24-hour PM2.5 NAAQS in a nearby area.

It should be noted that EPA does not agree with other arguments made by
Ohio to support exclusion of Ashtabula Township from the Cleveland area.
 The fact that actual emissions from the plant are only 3 percent of
“allowable emissions” does not eliminate the possibility for
contribution, and in fact would raise concerns that the source could
drastically increase emissions consistent with its allowable limits.
The concept of “allowable emissions” is not germane to the
designations process under section 107(d), and the fact that a source
might be able to emit some amount of a pollutant without violating other
Federal or State statutory, regulatory, or permit limits does not
establish whether that source is contributing to violations of a NAAQS
in a nearby area.  Similarly, the fact that the source has certain
controls is relevant, but does not answer whether the source is
contributing notwithstanding the level of control.  The amount of
population in and commuting from Ashtabula County were not under
consideration as a basis for inclusion of Ashtabula Township; that
proposed inclusion was based upon concerns about the amount of emissions
from the electric generating plant.  While EPA agrees that the pollution
rose for the Cleveland area does support the exclusion of Ashtabula
Township, EPA would not agree that winds are always blowing from the
southwest in this area, or that all pollution transport in this area of
the country always comes from that direction.  To be clear, EPA believes
that the pollution rose, the CES score, and the back trajectories for
this area all reasonably support the conclusion that the source in
Ashtabula Township is not contributing to violations of the 2006 PM2.5
24-hour NAAQS in Cuyahoga and Summit Counties

It should also be noted that EPA’s decision not to include Ashtabula
Township within the Cleveland nonattainment area for the 2006 24-hour
PM2.5 NAAQS does not affect or negate the inclusion of Ashtabula
Township within the Cleveland nonattainment area for the 1997 annual
PM2.5 NAAQS.  To the extent that emissions of direct PM2.5, SO2, and NOX
from the source in Ashtabula Township contribute to violations of the
annual PM2.5 NAAQS in the Cleveland area, Ohio will be required to
evaluate those emissions, and control them as appropriate, to provide
for attainment of the annual PM2.5 NAAQS as expeditiously as practicable
in this area.

Columbus, OH

Ohio:

The State of Ohio objected to EPA’s proposed inclusion of Franklin
Township, Coshocton County, within the nonattainment area for Columbus
for the 2006 24-hour PM2.5 NAAQS.  In its October 8, 2008, letter, Ohio
generally objected to this on the grounds that “the existence of an
electric generating unit in a township should not be the sole factor in
determining nonattainment.”  More specifically, Ohio argued in that
letter that Franklin Township should be excluded because the source
located there is adequately controlled, or will be in the future:

“The emissions from the Conesville power plant located in Franklin
Township (Coshocton Co.) have long been controlled with efficient
control equipment, and some of the units are expected to have additional
controls by the year 2009.  Currently there are four operating units and
two units that shut down permanently in 2006.  Besides electrostatic
precipitators, these operating units have installed or are planning to
install flue gas desulfurization systems.  Moreover, the largest unit
(800 MW) will have a SCR system in place and operating for the entire
ozone season, starting in June 2009.  In addition this unit (800 MW)
will have SCR equipment in continuous operation (the whole year)
starting in year 2011, increasing the nitrogen oxides emission
reductions.”

EPA Response:

See the overview response to comments on power plant issues, located at
the beginning of Section IV.

EPA disagrees with the reasons provided by Ohio for exclusion of
Franklin Township from the Columbus nonattainment area.  First, Ohio is
incorrect that the “existence” of the source is the sole reason for
EPA’s inclusion of Franklin Township.  EPA’s analysis has evaluated
not just the existence of the source, but also other considerations
including:  the significant quantity of emissions of the pollutants
(including PM2.5 precursors and directly emitted PM2.5) that speciated
PM2.5 data in this nonattainment area show to be of concern; evidence
from the pollution rose for this area that there is contribution from
the direction of this source to the rest of the nonattainment area; and
the CES score that likewise indicates that emissions from Franklin
Township contribute to violations in the Columbus area.

For example, emissions information available to EPA indicates that the
Conesville plant currently emits approximately 100,000 tons per year of
SO2 (over 106,000 tons in 2005, over 90,000 tons in 2006, and over
114,000 tons per year in 2007).  Similarly, the emissions of NOX from
this source are approximately 20,000 tons per year.  Emissions of this
magnitude place the Conesville plant among the largest sources of PM2.5
precursors in the country and make it the largest individual source in
the Columbus area.  Meteorological data derived in support of the CES
scores show that elevated levels of ambient PM2.5 in some cases occur on
days when winds are blowing generally from the direction of Franklin
Township towards the rest of the Columbus nonattainment area.  This
conclusion is further supported by the CES scores for the Columbus area,
which includes a score of 16 for Coshocton County (principally
attributable to Franklin Township), a score that is higher than for
other counties in the Columbus nonattainment area that Ohio agrees
should properly be within the nonattainment area.  Based upon this
evidence relevant to designations in accordance with section 107(d), EPA
concluded that emissions from Franklin Township are “contributing”
to violations in Columbus.  In the context of the nonattainment SIP for
this area, Ohio will have the opportunity and the obligation to perform
further analysis and attainment demonstration modeling that can further
explore the contribution of the source and the appropriate course of
action to reduce that contribution.

EPA also disagrees with Ohio’s conclusions relating to the level of
control of the Franklin Township source as a basis for excluding it from
the nonattainment area.  As noted above, EPA has concluded that the
source in Franklin Township does contribute to the violations,
notwithstanding its current level of control.  Under section 107(d), EPA
believes that the level of control of emissions from the source is a
relevant inquiry in the designations process to assure that EPA and the
State are using up to date and accurate emissions information.  EPA does
not believe that the level of control should be used as a basis to
exclude a source that is otherwise deemed to be contributing to the
violations, based upon information such as its amount of emissions,
geographic location, and meteorological connection to the nearby
violating area.  Whether sources in an area that is violating or is
contributing to violations of the NAAQS are adequately controlled is
more appropriately assessed during the development of the nonattainment
area SIP for an area.  Section 107(d) does not require EPA, in essence,
to construct a mock-up nonattainment area plan for an area and to
predetermine appropriate levels of pollution control on behalf of the
State, as a necessary step in promulgating the designation for the area.
 In short, the level of control of a source does not in isolation answer
whether the source is contributing to the violations.

For example, Ohio argues that this plant is currently well controlled
but will have additional controls, either in 2009 or in some unspecified
future plans.  As noted above, EPA has concluded that this source
currently has particularly high levels of PM2.5 and PM2.5 precursor
emissions and that other information such as meteorological data
confirms that these emissions are contributing to violations in the
Columbus area.  This contribution is occurring, notwithstanding that the
source in question has some significant pollution controls in place.  By
inclusion of Franklin Township within the nonattainment area, Ohio and
EPA will evaluate this source as part of the development of the
nonattainment area plan to assure that it is adequately controlled and
controlled in a timely fashion, to provide for expeditious attainment of
the 24-hour PM2.5 NAAQS in the Columbus area as required by the CAA.
This inquiry may conclude that the source is appropriately controlled,
but that assessment must occur during the proper process contemplated by
the CAA for development of nonattainment area plans.

With respect to future or planned future emissions reductions at the
source, EPA has concluded that for evaluating contribution for
designations under section 107(d), it is appropriate to look at the
actual level of emissions in the relevant three year period, whether
2005-2007, or 2006-2008 if a State elects to submit additional data for
2008.  Given the present tense formulation of section 107(d), EPA does
not believe it is appropriate to base designations on projections of the
future.  Thus, Ohio has indicated that the source in Franklin Township
is installing a scrubber and SCR on its largest unit that will be
operational in the ozone season in 2009, and operational year round in
2011.  Although EPA supports these important steps by the source, they
nevertheless will result in emissions reductions that will happen beyond
the period that is appropriate for consideration in the designations
process.  However, these reductions will occur during the time that Ohio
is developing the nonattainment area plan for this area, and they may
properly be taken into account during that process.  Ohio may conclude,
and EPA may ultimately agree, that these reductions of SO2 and NOX are
all that is necessary to reduce NOX emissions from this specific source
within the PM2.5 nonattainment area plan for Columbus, but it would be
inappropriate to prejudge that outcome now.

Davenport-Moline-Rock Island, IA-IL

The State of Illinois

Illinois:

The Illinois Environmental Protection Agency has worked closely with the
Iowa Department of Natural Resources (DNR) to perform the following
technical analyses, and both States agree that Rock Island County does
not contribute to violations of the 24-hour PM2.5 standard in Davenport.

EPA Response:

EPA reviewed the additional information provided by Illinois including
modeling analyses.  The modeling shows a minor contribution from the
Rock Island point sources.  Some additional contribution is expected
from area and mobile sources from the urbanized areas of Rock Island
County, Illinois and Scott County, Iowa.  So even with violating
monitoring being highly affected by a local source, sources from the
entire urban area also contribute to violation.  Contributing counties
are designated as nonattainment, even if the contribution is minor.  EPA
is designating partial county areas in Scott County, Iowa and Rock
Island County, Illinois to include the sources contributing to the
monitored violations in Davenport.

EPA Response to Additional Modeling Results Referenced in Illinois
Comment Letter:

The AERMOD modeling performed by Illinois EPA is not documented with any
supporting information.  No information is given about the methodology
used for the application of AERMOD.  For instance, the approach to
incorporate concentrations associated with calm wind speeds and the
selection of “urban/rural” deposition will make a noticeable
difference in model estimates.

Illinois EPA asserts that the maximum impact of all Rock Island County
sources combined is 1.17 μg/m3 based on their AERMOD simulations.
These AERMOD simulations include eight stationary point sources, which
are unlikely to be inclusive of all point sources in the county.
Additionally, this analysis does not include any other anthropogenic
emissions such as mobile sources and area sources.  If all anthropogenic
sources were included in addition to the eight stationary sources, the
impacts would be even larger than Illinois EPA’s estimated 1.17
μg/m3, which in itself could be considered a significant contribution.

Illinois EPA asserts that when using CAMx zero-out modeling, all
anthropogenic emissions sources in Rock Island County contribute a
maximum of 2 ug/m3 in Davenport.  This could be considered significant.

Illinois EPA asserts that Rock Island County contributes less than 1
percent of each sulfate, nitrate, and primary PM2.5 on the highest 2
percent of PM2.5 concentration days in 2002 using CAMx source
apportionment applied with a Central Regional Air Planning Association
(CENRAP) modeling platform.  EPA agrees that these results indicate that
Rock Island sources have a limited impact on secondarily formed
particulate impacting the grid cell containing the violating monitor.
However, given the uncertainties in the modeling, as described further
in the TSD, EPA finds the results informative but not conclusive about
the impacts of Rock Island’s emissions on the violating monitor.  The
modeling results do not support the State’s position that emissions
sources in Rock Island do not contribute to the violating monitor.

The State of Iowa

Iowa:

The Davenport/Scott County monitor is located 150 meters from Blackhawk
Foundry.  The monitor records exceedances on days when other area
monitors record relatively lower values.  In addition, pollution roses
indicate that the greatest differences in readings between the Blackhawk
Foundry monitor and another local monitor (the Jefferson School monitor)
occur when winds blow from the foundry toward the monitor, suggesting
influences from foundry emissions.

EPA Response:

The comments relating to proximity of the Davenport (Blackhawk Foundry)
monitor to a source and the comparison of exceedance day readings to
readings at other monitors raise many of the same issues as described in
the Muscatine section of this document.  EPA incorporates its response
regarding the Muscatine monitor in its response regarding Davenport.
EPA also notes that the Davenport monitor is a federal reference method,
source-oriented middle scale monitor, eligible for comparison to the
24-hour PM2.5 NAAQS, and that Iowa has not raised issues concerning the
siting of the monitor or validity of data collected at the monitor.

EPA acknowledges that the pollution roses provided by the state indicate
large differences in monitored readings between Blackhawk Foundry and
other monitors on exceedance days.  However, as described below, we are
unable to conclude on this basis that contributions from Blackhawk
Foundry alone are the sole basis for the monitored exceedances.

Iowa:

PSAT simulation is consistent with the zero-out results (discussed
above), showing very small contributions from sulfate and nitrate
emissions sources in Rock Island County, and similar contributions from
Scott and Muscatine Counties to particulate sulfate and nitrate
concentrations at the violating monitors.

EPA Response:

EPA agrees that the primary contributing pollutant from local sources in
the area to the violating monitors is direct PM2.5 rather than precursor
emissions.  EPA’s analysis of this information is discussed in more
detail in the TSD for Scott and Muscatine counties.  However, as
explained elsewhere, EPA believes that other nearby sources of PM2.5 in
each area nonetheless contribute, or have the potential to contribute.
(See also, the discussion of contributing emissions in the TSD for Rock
Island.)

Iowa:

Iowa has re-reviewed the nine factors, in particular wind roses in the
two areas, as well as the growth pattern in Rock Island County (which
the commenter states indicates negative growth for the foreseeable
future), and believes that the data support the smaller boundary
originally recommended by the State.

EPA Response:

EPA has carefully considered all of the information submitted by Iowa
and Illinois regarding appropriate boundaries.  Wind roses, for example,
are instructive, but not dispositive of the appropriate boundary for an
area.  For example, as discussed above and in the TSD for Scott County,
point source modeling shows that other local point sources in the area
contribute to monitored exceedances.  EPA has reviewed this information,
and additional information made available to EPA after the 120-day
letter (and included in the docket), and has revised its 9-factor
analysis based on this review (see the TSDs for a detailed discussion of
the analyses).  Although this analysis has caused EPA to determine that
a partial county boundary is appropriate, EPA does not agree, for
reasons stated herein and in the TSDs, that the very small boundaries
suggested by the state are appropriate.

Below are EPA’s responses to the State of Iowa’s contention that
modeling and other emissions impact analyses show that local point
sources contribute significantly to violating monitors even on days when
regional contributions are moderate to low, and that emissions from
other local sources, and sources outside the vicinity of the Blackhawk
Foundry monitor, do not significantly contribute to violations.

Iowa:

AERMOD dispersion modeling shows that on “most” exceedance days,
Blackhawk Foundry contributions were between 20 percent and 25 percent
of the local source contributions, and that the “vast majority” of
the remaining PM2.5 emissions are attributable to sources outside Scott
and Rock Island Counties.  This shows that the foundry “causes or
contributes” to the exceedances, thus justifying a small boundary
around the source’s area of impact.

EPA Response:

This comment was submitted in conjunction with Iowa’s October 20, 2008
response to EPA’s letter informing Iowa of its intent to modify the
state’s initial boundary designations for eastern Iowa (the 120-day
letter).  At that time, Iowa had not modeled impacts from other local
direct PM2.5 point sources on concentrations at the violating monitor.
Iowa subsequently modeled (using AERMOD) additional local sources and
argued that they have a minimal impact on concentrations at the
violating monitor. In fact, the modeling of direct PM2.5 emissions shows
that other point sources in the area impact the monitor, and the
nonattainment boundary which EPA is promulgating will encompass all of
these PM2.5 sources.  In addition, EPA has determined that the
uncertainty regarding the AERMOD data and the lack of speciation data at
the violating monitor, as described in the TSDs, prevents us from
concluding that local sources of direct PM2.5 other than the Blackhawk
Foundry (i.e., sources outside the state’s recommended boundary) do
not contribute to the violations.  Whether these other sources should
ultimately be required to reduce emissions will be determined by the
state during the development of the implementation plan for the area.

EPA has also performed a positive matrix factorization (PMF) analysis on
speciation data from the Jefferson School monitoring site in Davenport.
This analysis is detailed in the TSD for Scott County.  The analysis
indicates that a unique source other than Blackhawk Foundry contributed
to the mass at the nearby Jefferson monitor.  Although this is not the
violating monitor, it indicates the influence of a source outside the
state’s recommended nonattainment area on a nearby monitor in the
area.  This finding supports EPA’s decision to promulgate a boundary
larger than that recommended by the state.

Iowa:

The State’s recommended boundary includes the only sources of direct
PM2.5 emissions in the two-county area which have any significant
contributions to predicted concentrations of the violating monitor on
exceedance days.

EPA Response:

As stated in response to II)A), EPA does not believe the AERMOD modeling
is adequate to determine that the other point sources of direct PM2.5 in
the area are not contributing to violations.  In fact the modeling and
other analyses show that other sources do have some impact.  EPA
believes that other point sources in the area should be included in the
nonattainment boundary.

Iowa:

The results of CAMx model sensitivity analyses and AERMOD runs show that
Rock Island County should not be included in the nonattainment area due
to insignificant contributions to predicted concentrations at the
monitor, based on the following factors:  (1) the June 8, 2007 EPA
guidance does not provide for CBSA presumptive boundaries for 24-hour PM
violations;  (2) the mere presence of a broad mix of sources in Rock
Island does not indicate their potential contributions;  (3) a zero-out
run of direct PM emissions in Rock Island County results in an
insignificant reduction in base-case contributions at the violating
monitor and an even smaller reduction at other area monitors.  There are
similar negligible reductions when sulfate and nitrate precursors are
subject to zero-out runs; and (4) a sensitivity analysis of mobile
source commuting activity between Scott and Rock Island counties shows
that traffic patterns and motor vehicle emissions do not influence the
violating monitor on exceedance days.

EPA Response:

EPA has determined that the urbanized portion of Rock Island County will
be included in the nonattainment area, for reasons detailed in the
technical support document prepared by EPA for the State of Illinois and
included in the docket for the accompanying rulemaking.  EPA’s TSD for
Scott County also contains some discussion of the issues.  With respect
to Iowa’s specific comments, EPA provides the following responses:

	(1)  EPA agrees that there are no presumptive boundaries for the 2006
24-hour PM2.5 standard designations.  The 2007 guidance does provide,
however, that one of the 9 factors in the boundary analysis is
jurisdictional boundaries, which could include consideration of CBSA,
MSA, or county boundaries.  However, EPA analyzes all of the factors,
and may conclude that smaller or larger boundaries are appropriate,
based on a case-by-case review.  In the case of Rock Island and Scott
counties, EPA has analyzed these factors and has concluded that the
urbanized portion of these counties should be included in the
nonattainment area.  This conclusion is not based on any presumptive
boundary for the area, but is the result of application of the 9-factors
to the specific information available for the Quad Cities area.

	(2)  EPA agrees that the “mere presence” of sources in an area does
not necessarily demonstrate their contribution to violations of the
NAAQS.  However, as described in the TSDs and the record for the
designations, including this response to comments, EPA has determined
that sources of emissions in Rock Island County may contribute to the
violations recorded in Davenport.  Therefore, EPA is including a portion
of the county in the nonattainment area.

	(3)   The zero-out modeling is instructive but not conclusive with
respect to the appropriate boundaries.  In addition, in establishing
boundaries for contributing sources or areas in the Quad Cities, we do
not believe it is appropriate to establish a bright line regarding the
amount of reduction in predicted concentration which an area must be
below to show that it is not contributing to violations of the NAAQS
(for example, that a 4% reduction in a zero-out run is insignificant,
but some higher amount is significant).  Instead, as explained in more
detail in the TSDs, in this response to comments, and in other materials
in the record, we are establishing the nonattainment boundary to
encompass most of the sources of PM2.5-related emissions in the area
which could, based on available information, contribute to PM2.5
concentrations at the violating monitor.  The states will subsequently
determine, through refined analyses during development of their
implementation plans, the emissions reductions needed, the portions of
the nonattainment area in which they must occur, and the sources which
must reduce emissions in order to achieve the NAAQS.  EPA believes that
the boundaries defined in this rulemaking will enable the states to
perform these analyses and develop strategies to achieve the standards.

	(4)  EPA agrees, as described in more detail in the TSDs and other
information supporting the decision, that direct PM2.5 emissions are a
critical component of the PM2.5 concentrations at the violating monitor
in Davenport. However, zero-out modeling results provided by the state
do show that emissions (including mobile) from Rock Island contribute to
the violating monitor on exceedance days and support EPA’s decision to
include a portion of Rock Island in the nonattainment area.  This is
discussed in more detail in the TSDs for the area, and most
significantly, in the Rock Island County TSD.

Iowa:

The modeling shows that sources in rural Scott County do not cause or
contribute to violations of the PM2.5 NAAQS.  Zero-out runs show that
eliminating emissions from rural portions of the county result in only
minimal reductions in PM2.5 concentrations at the violating monitor on
predicted exceedance days.

EPA Response:

As explained in the TSD, EPA believes that the rural portion of Scott
County, which does not contain point sources of PM2.5 emissions, likely
does not have a significant contribution to the PM2.5 concentrations at
the violating monitor, so as to require inclusion of that portion in the
nonattainment area.  However, EPA’s conclusion does not mean that
other portions of the county containing sources of PM2.5-related
emissions from point and area sources need not be included.  This is due
in part to the fact that, as stated in the TSD for Iowa, zero-out
techniques, although appropriate for resolving non-point sources, in
this instance, are not yet capable of reliably assessing the impacts of
a single source at the source receptor distances encountered in Scott
County.  Therefore, EPA is including the urbanized portion of the county
and those nearby rural portions containing PM2.5 emissions of concern in
the nonattainment boundary for the area.

Dayton-Springfield, OH

Ohio:

In its initial designation recommendations to EPA in December 2007, and
in its October 2008 letter responding to EPA’s proposed modifications
thereto, the State of Ohio has argued that Clark County should be
excluded from the Dayton nonattainment area for the 2006 24-hour PM2.5
NAAQS.  Ohio premised its initial recommendation on the lack of
monitored violations in Clark County, relatively low SO2 and NOX
emissions, population of 142,000 people, relatively low commuting, and
the geographic location of Clark County to the northeast of the
violations of the NAAQS in Montgomery County.  Subsequent data from
2005-2007 indicates that Clark is violating the NAAQS and EPA
accordingly notified Ohio of its intention to modify the State’s
recommendation to include Clark County in the Dayton nonattainment area.
 In its response to EPA’s proposed modification, Ohio acknowledged
“high pollution levels being detected in Clark County” but argued
that these concentrations are attributable to sources southwest of Clark
County and not due to local sources.

EPA Response:

Under section 107(d), EPA must designate as “nonattainment” both
those areas that are violating the NAAQS and those areas that are
contributing to violations in a nearby area.  Based upon 2005 to 2007
monitoring data, Clark County is itself violating the 2006 24-hour PM2.5
NAAQS.  Thus, Ohio’s arguments with respect to the level of
contribution of emissions from Clark County to Montgomery County do not
override the obligation of EPA to designate Clark County as
nonattainment.

EPA has concluded that it is appropriate to designate Clark County as a
part of the Dayton area because it is immediately adjacent to Montgomery
County (which is also violating the NAAQS) and Greene County (which is
contributing to violations in Montgomery).  EPA agrees that the
contribution of emissions in Clark County to violations in nearby
Montgomery County is relatively low.  For example, compared to
Montgomery County, Clark County has a lower total emissions, lower
population, and lower commuting levels of commuting, but the amount of
each of these is not insignificant in the context of this area.  In
particular, the number of commuters from Clark County to other Counties
within the area is approximately 60,000 and reflects a percentage of
commuting comparable to that of Montgomery and Greene Counties and a
number and amount of commuting comparable to that of Greene County.
This information indicates some contribution from Clark County to
Montgomery County.  Moreover, the pollution rose for a critical
Montgomery County site supports the conclusion that there is
contribution from the direction of Clark County on some of the days with
relatively high ambient PM2.5 levels.  Finally, EPA considered that
Clark County is already a member of the Miami Valley Regional Planning
Commission and has typically been included with other Dayton area
counties in the nonattainment area for ozone.  Under these
circumstances, EPA is designating Clark County nonattainment and
including it within the boundaries of the Dayton area, rather than a
separate nonattainment area.

Ohio argues, on the basis of wind data, that there is also contribution
from Montgomery County to Clark County.  As noted above, Clark County is
violating the NAAQS based upon 2005-2007 data.  The new information from
Ohio would perhaps support EPA designating Montgomery and Greene
Counties nonattainment based upon their contribution to Clark, but EPA
does not consider this necessary given that Montgomery County is itself
violating the NAAQS, and that both Ohio and EPA agree that Greene County
is contributing to violations in Montgomery County.  Thus, the wind data
could be support for designating the same three counties as part of the
Dayton area, but EPA does not consider this necessary.

Detroit-Ann Arbor, MI

Michigan:

In our December 18, 2007, letter to EPA, we recommended that southeast
Michigan be divided into three separate nonattainment areas consisting
of St. Clair County, which appears to be influenced by Canadian
emissions; Wayne County, which has higher concentrations of PM2.5 than
the other counties due to local emissions sources; and the remaining
five counties as a third nonattainment area.

EPA Response:

EPA disagrees with Michigan’s recommendation to divide the Detroit
nonattainment area into three separate nonattainment areas.  EPA
generally will not divide areas because having one area allows for
better planning.  Instead of assessing the impact of a source on several
nonattainment areas, determining the impact is simplified when there is
just one area.  Having a single nonattainment area also eliminates the
need to integrate planning for multiple adjacent areas.

Specifically in the Detroit area, the metropolitan planning organization
addresses the seven counties of the existing nonattainment area and thus
is already designed to conduct planning for the prospective
nonattainment area as a whole.  Michigan wrote that the air quality in
Saint Clair County may be affected by international transport and that
local sources influence the air quality in Wayne County.  The air
quality in these counties is also affected by the same common sources as
all counties in the Detroit area.  The populations and commuting data
also indicates a connection between the metropolitan area counties.
Therefore, it makes sense to have a single Detroit nonattainment area
instead of dividing the area into three parts.  Michigan can certainly
include a mix of controls implemented for area-wide air quality
improvement and specific control measures to address the unique sources
affecting the air quality in Saint Clair and Wayne Counties.  A single
seven county nonattainment area allows Michigan the greatest flexibility
in improving the air quality in the Detroit area.

Michigan:

In its October 14, 2008, letter to EPA, Michigan reiterates arguments
that “the industrialized area of Wayne County is unique to the rest of
the region and should be dealt with separately.”  To support this
argument, Michigan argued that only monitors in Wayne County have shown
violations of the annual PM2.5 NAAQS since 2003.  Michigan asserted that
because of this monitor, six other counties in the Detroit area have
“been kept in nonattainment.”   For the 24-hour PM2.5 NAAQS,
Michigan conceded that monitors in both Wayne and St. Clair show
violations of the NAAQS with 2006-2008 data (based on analysis using
data from the first half of 2008), but repeated arguments that
designating a large area is “unnecessary and heavy handed.”

EPA Response:

EPA disagrees with Michigan’s approach to assessing what areas should
be designated nonattainment under section 107(d).  EPA reads the statute
to require designation of those areas that are violating and those areas
that are contributing to violations in nearby areas.  EPA does not
interpret the term “contributing” to be limited merely to the area
allegedly contributing the last increment of ambient PM2.5 that results
in a violation in the area; rather, EPA interprets the term to include
the full range of nearby sources of PM2.5 and PM2.5 precursors that are
cumulatively contributing to the violation.

5-2007 design values for Monroe (38 μg/m3), Oakland (40), St. Clair
(41), Washtenaw (39), and Wayne (43) Counties all are above 24-hour fine
particulate standard.  Michigan used data from only the first two
quarters of 2008 to make its projections of the 2006-2008 design values
in its October 2008 letter.  Design values must be calculated using
three complete years of monitoring data.  Considering that five of seven
counties in the Detroit nonattainment area have design value violating
the 24-hour fine particulate standard, the high particulate
concentrations are distributed through the area and not just affecting
two counties.

Michigan:

Michigan argued that the PM2.5 problem in Southeast Michigan “has been
driven by the high values in the industrialized portion of Wayne
County.”  Michigan reiterated that six other counties are being
designated nonattainment for the 24-hour PM2.5 NAAQS

“because of one monitor that is in the most industrialized area of
Wayne County, directly downwind of a steel mill, auto manufacturing
plant and oil refinery.”  Michigan argued that this monitor is
“strongly influenced” by “local sources.”

Michigan argued that the “history” of PM10 and PM2.5 violations in
this industrial center supports “focused attainment plans” for a
separate nonattainment area in Wayne County.

EPA Response:

EPA disagrees with Michigan’s implications that violations of the 2006
24-hour PM2.5 NAAQS are solely the result of emissions in the
“industrialized” portion of Wayne County.  EPA does not dispute that
the violating monitor is near a number of stationary sources, or that
the emissions from such sources do contribute to the violations at that
monitor.  However, EPA’s obligation is to include within the
nonattainment area not merely the nearest sources to the monitor, but
rather to include those areas that contain emissions sources that are
“contributing” to the violations at that monitor.  Michigan does not
contend that all of the ambient PM2.5 at the violating monitor in Wayne
is the result of emissions exclusively within the near vicinity of the
monitor, nor even exclusively within Wayne County.  Regardless of
whether a significant percentage of the ambient PM2.5 at the monitor was
the result of emissions from sources in the near vicinity of the
monitor, EPA must consider other sources that account for the remaining
ambient PM2.5 at the monitor, and EPA must promulgate boundaries that
correctly include those other sources of the remaining ambient PM2.5
within the nonattainment area.

EPA’s view is that the information relevant to evaluating contribution
to violations in this area compels the conclusion that areas outside
Wayne County but nearby to Wayne County are contributing to the
violations, as contemplated by section 107(d).  Thus, for example,
evidence such as the emissions inventory of direct PM2.5 and PM2.5
precursors for other nearby counties, the pollution roses for this area,
the CES scores for other counties, and the amount of emissions reflected
by commuters and VMT for other counties, all tend to support that there
are emissions and emissions activities in the surrounding counties in
the Detroit area that are cumulatively contributing to the ambient
levels of PM2.5 at the violating monitors in both Wayne and St. Clair
Counties as well as at the other monitors in the area that are currently
violating the standard.  In accordance with the Clean Air Act, these
sources in these areas are thus appropriate for inclusion within the
nonattainment area boundaries, and thus for evaluation for control in
the nonattainment plan for this area.

EPA also disagrees with Michigan’s suggestion that past history with
PM10, and implicitly with the designation for this area for PM10, is
supportive of the State’s view.  PM10 is a different NAAQS, with a
different size indicator, that forms differently and behaves differently
in the ambient area, typically emitted by different sources and
requiring different control strategies.  The relevance of past history
with PM10, especially given the facts of this area and the nature of the
PM2.5 particles in this area, is negligible.

Michigan:

To support its arguments with respect to Wayne County, Michigan
submitted a study commissioned by the Southeast Michigan Council of
Governments (SEMCOG) to analyze monitor data in the Detroit area.
Michigan described the purpose of this study as to determine the
“drivers (i.e., local source, regional transport, or meteorology) for
high PM2.5 days in South East Michigan.”  The State argued that the
“drivers” of high PM2.5 at the “majority” of monitors with high
readings “are regional transport (background levels entering Southeast
Michigan) and/or poor atmospheric ventilation across the network.”
Michigan also noted that the report indicates that ambient
concentrations are caused by “regional-scale contributions,
urban-scale contributions, and neighborhood-scale contributions.”

EPA Response:

EPA fully agrees with the SEMCOG contractor’s finding, as summarized
by Michigan, that ambient concentrations reflect contributions on
various scales ranging from regional scale to urban scale to
neighborhood scale.  Indeed, Michigan argues that the Dearborn monitor
records especially high values because it reflects impacts from both an
industrial zone plume and the urban scale plume.  EPA agrees with this
view as well.  Where Michigan appears to disagree with EPA is in
recommending a subdivision of the metropolitan area into three zones
that Michigan argues have separate sets of local contributors, without
regard for the resulting segregation of the common origins of the urban
scale contribution into three separate nonattainment areas.

EPA commends SEMCOG for sponsoring work to understand the origins of the
24-hour PM2.5 problem in Southeast Michigan.  However, this work is
likely to have more utility in the attainment planning phase than in the
designations phase.  The contractor finds that many monitors have high
concentrations if and only if other monitors also have high
concentrations.  This finding is consistent with the premise noted
above, that a significant element of high concentrations in the Detroit
area is an “urban plume.”  However, the majority of the
contractor’s work is designed not to define the origins of this urban
plume but rather to define the origins of concentrations in excess of
the combined impact of the urban plume and regional scale contributions.
 This work, by its very nature, is prone to focus on the contributions
of heterogeneously distributed sources that have disparate impacts at
different locations.  Conversely, this work, by its very nature, is
prone to disregard the impacts of sources that have relatively
homogeneous impacts, which can occur either because similar sources are
homogeneously distributed or because the emissions undergo a process
that disperses the impact (which would be expected to occur during
photochemical formation of secondary particles).  As a result, the study
is more useful for defining subsections of the area that may have unique
contributions than it is in defining what source area contributes to the
relatively homogeneous “urban plume.”

From this perspective, it is clear that the “drivers” identified by
Michigan represent evenly distributed sources of locally significant
sources that may cause some monitors to record concentrations that are
distinguishable from concentrations observed elsewhere.  It is equally
clear that the “drivers” identified by Michigan are almost by
definition not the sources distributed throughout the metropolitan area
that contribute to the urban plume described by the contractor.  Thus,
while EPA and Michigan agree that the “drivers” must be part of the
nonattainment area, EPA finds it equally important to include the range
of sources that contribute to the “urban plume.”

From another perspective, the concept of the “driver” of
concentrations on days with high ambient PM2.5 levels is merely using
different terminology to accomplish the same goal – to argue that only
the source or sources that add the last microgram of ambient PM2.5
levels above a standard is the only source or sources contributing to
the total ambient level.  EPA does not agree that this is the
appropriate method to evaluate the full range of sources that are
cumulatively contributing to the violation of the NAAQS.

Second, it must be noted that it is likewise not appropriate to argue
that regional transport from greater distances, or even from other
States, is a grounds to exclude the nearby areas that are also
contributing to the violations in the area.  The Clean Air Act provides
other tools to address the influx of regional transport, especially
under section 110(a)(2)(D) and section 126.  In the context of
designations, it is the obligation of EPA to designate areas that are
violating the NAAQS and nearby areas that are contributing to those
violations.  EPA does not agree that all of the ambient PM2.5 at the
violating monitors in the Detroit area comes either from the sources
immediately adjacent to the monitors or from other States – there are
geographic areas between those extremes that contain sources with
emissions that are contributing to the violations.

The report noted that the ambient concentrations are the result of
emissions from not just local and distant sources, but also from sources
on an urban-scale.  Having a single Detroit nonattainment area allows
Michigan to address sources through the seven county area that affect
the air quality and thus contribute to the violations.  While EPA is not
prejudging the mix of emission controls that Michigan should adopt to
provide for attainment, the Act mandates that EPA promulgate a
nonattainment area that includes the full area violating the standard
and nearby area contributing to the violations, in part to assure that
an integrated plan is developed based on consideration of control
options for all sources that contribute to the violations.

Michigan:

Michigan highlighted a conceptual diagram illustrating its view of the
progression of PM2.5 concentrations along a transect running from
southwest to northeast in support of its argument that the Dearborn
monitor in Wayne County is in a “unique” position “in the core of
the industrialized zone plume and urban scale plume, which results in
much higher values due to local sources than the other monitors in the
area.  The State further argued that data from the New Haven monitor
site, “downwind” from Detroit, did not show the same impacts of the
“urban scale contributions or the industrial zone plume.”

EPA Response:

The diagram supplied by Michigan as Figure 2 in its letter illustrates
that the ambient concentration is affected by regional, urban, and
local-scale emissions.  Both EPA and the States have responsibilities
for programs to reduce regional-scale emissions.  The States must
develop control measures to reduce both the urban and local-scale
emissions to bring areas into attainment.  Specifically for Detroit,
Figure 2 suggests that the regional and urban-scale emission create
ambient concentrations near the PM2.5 standard (the Macomb County
monitor is close to the standard).  Thus Michigan would have to
eliminate almost all of the local-scale emissions from the “industrial
zone” to reach attainment unless there are also regional and
urban-scale reductions.  Therefore, Michigan’s diagram highlights the
importance of designating a broad Detroit nonattainment area that
includes a complete set of the sources in the Detroit metropolitan area
that contribute to these violations.

Michigan:

Michigan also highlighted Table 2 in its letter to support its arguments
regarding Wayne County.  According to Michigan, 13 of the 15 monitors in
the area, for 85 percent of the high days between 1999 and 2006,
occurred on days when “the entire network was exhibiting high PM.”
By comparison, Michigan argued that the Dearborn and Wyandotte monitors
“frequently had exceedances on days when the entire network was not
exhibiting high PM.”  Michigan reasoned that this proves that these
monitors are “significantly influenced by nearby emissions sources.”

EPA Response:

This illustrates that violations can be caused by local or broader scale
emissions.  Local sources will cause high concentrations at nearby
monitors, while emissions on a broader scale will cause high
concentrations over a wide area.  The fact that most or all of the
Detroit area monitors will record high concentrations on the same day
suggests there are broader scale sources that affect the entire area.
That is, the existence of days when “the entire network was exhibiting
high PM” lends support to EPA’s decision to designate Southeast
Michigan as a single seven-county nonattainment area.

Michigan:

Michigan also pointed to Figure 3 in its letter as evidence that the
Dearborn monitor in Wayne County has “a much higher percentage of high
days than other monitors.”  As evidence, the State noted that the
Dearborn monitor has many more days above 30 μg/m3 compared to the
Allen Park monitor.  Again, Michigan argued that the higher readings at
the Dearborn monitor than at the Allen Park, which the State
characterizes as near but upwind from the Dearborn monitor, indicate
that the latter monitor has a “strong influence from local sources.”

EPA Response:

As noted previously, the Act requires that EPA designate nonattainment
areas that include all nearby sources that contribute to nonattainment,
including both the local sources (i.e., sources nearby the monitor) and
sources elsewhere in the metropolitan area that contribute to the
violations.  To the extent that local sources cause a monitor to observe
more high concentration days, these local sources arguably make the
violation more difficult to address.  Nevertheless, while the Act gives
the State substantial discretion in selecting what combination of
controls of local sources, controls of metropolitan area sources, and
controls of sources elsewhere in the State to adopt to address the
nonattainment problem, the Act dictates that EPA define a nonattainment
area and planning area in which the full range of nearby contributing
sources are included.

Michigan:

μg/m3 excess of PM2.5, and that this quadrant is the direction of “a
steel mill, an auto manufacturing plant, an oil refinery and other
smaller industries.”  By comparison, Michigan notes that other
monitors show a lesser impact, less than 2 μg/m3.

EPA Response:

EPA believes that Michigan is focusing on local deviations from broadly
high concentrations and fails to address the contributions from sources
throughout the metropolitan area to the “urban plume.”  The
“expected value” appears to be largely a reflection of the sum of
regional scale and metropolitan scale impacts, and the “excess”
appears to be a reflection of local (neighborhood scale) source impacts.
 Such a differentiation may be useful for attainment planning purposes,
but EPA’s obligation in promulgating designations is to define a
nonattainment area that includes nearby sources contributing to the
“expected value” as well as sources contributing to the
“excess.”

Again, Michigan evidently starts from the premise that the only areas
that should be designated as “nonattainment,” are the area in which
they claim there are sources that add the last increment of ambient
PM2.5 that results in violations at the Dearborn monitor, ignoring the
other contribution from other sources in nearby areas.  EPA does not
subscribe to this approach, as it is the cumulative impact of emissions
sources and activities throughout the Detroit area that are, in the
aggregate, contributing to the total amount of ambient PM2.5 at the
violating monitor.  The purpose of the designations process is not to
seek only the individual source next to the monitor that adds the last
increment, but rather to identify the range of sources that are
contributing.  This is logical, because these are the sources that will
need proper evaluation in the context of the development of the
nonattainment SIP, and control to assure expeditious attainment of the
NAAQS, as appropriate.

Taken at face value, the analysis submitted by Michigan may well serve
to identify many of the specific sources that the State must control in
the nonattainment area SIP for Detroit to assure that this entire area
attains the 2006 24-hour PM2.5 NAAQS expeditiously.  However, this
analysis must look more broadly at all sources throughout the area
designated nonattainment and assure that all source categories are
evaluated for potential control, consistent with the requirements of the
CAA and consistent with attainment of the NAAQS as expeditiously as
practicable.  After all, the widespread violations being record by
monitors throughout the Detroit area are not being caused solely by a
few select sources in one portion of the area.

In EPA’s view, it is meaningless to claim “more robust mathematical
support” for an analytical tool that pursues a different type of
information that is less relevant to the issue at hand.  The tool is
being used to identify locally significant sources, and there is no
dispute that locally significant sources should be included in the
nonattainment area.  Consequently, EPA’s tools, which better address
what areas have sources that contribute to the “urban plume,”
provide better information with which to determine nonattainment area
boundaries.

Michigan:

Michigan argued that the evidence it provided concerning the
“unique” aspects of Wayne County support designating it as a
separate nonattainment area within the Detroit area.

EPA Response:

Michigan has recommended that seven counties in Southeast Michigan be
designated nonattainment, and EPA agrees with this recommendation.  The
disagreement between EPA and Michigan relates to Michigan’s
recommendation that these seven counties be divided into three separate
nonattainment areas rather than combined into a single nonattainment
area.  Since CAA section 107 requires each nonattainment area to include
the area that is violating and any nearby area contributing to that
violation, the recommended subdivision into multiple nonattainment areas
would require justification either that the subdivided areas are not
nearby or that the areas do not contribute to each other.  For example,
justification would need to be provided either that Wayne County is not
nearby to its neighboring counties or that there is no contribution from
Wayne County to the violations in various other Southeast Michigan
counties and no contribution from the other counties to the violations
in Wayne County.  Michigan provided no such justification, and EPA
believes that the evidence contradicts any such claim.

The information also suggests it would be difficult for the air quality
through the Detroit area to meet the standards relying just on localized
measures within Wayne County.  The fact that some portions are impacted
more by local sources is not unique.  This is common in cities around
the nation. This allows the State to determine how it will use area-wide
measures combined with controls focused on specific sources to bring the
area’s air quality into attainment.  EPA designated adjacent counties
in different nonattainment areas only when the counties were clearly in