Document ID: EPA-HQ-OAR-2007-0225-0032
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2007-08-02T04:00Z

Chapter 4:	Approach for Estimating Reductions for Full Attainment
Scenario 

This chapter presents the methodology used to estimate emission
reductions that may be needed to reach national attainment of the
proposed tighter alternate primary 8-hour ozone standard of 0.070-0.075
ppm.  After applying the hypothetical control strategy described in
Chapter 3, there were many areas that were still not projected to attain
the more stringent standard modeled of 0.070 ppm.  This chapter presents
the methodology EPA developed to determine emissions reductions needed
for national attainment of the alternate standards on each end of the
proposed range (e.g. 0.070 and 0.075 ppm).  It also presents estimated
emission reductions needed to attain a more stringent option analyzed of
0.065 ppm.   

4.1  	Development of Air Quality Impact Ratios for Determination of
Extrapolated Costs

Table 3a.11 lists the highest projected design value in each monitored
county for the 2020 baseline (current standard – effectively 0.084
ppm) and after application of the illustrative national control strategy
designed to attain an alternate primary standard of 0.070 ppm.   From
this table one can determine the counties that did not meet the target
air quality levels after implementation of the national hypothetical
0.070 control scenario.  Because the goal of the RIA is to estimate the
estimated incremental costs of full attainment, some estimate of the
remaining emissions needed to reach these targets is required for each
of these areas.

It was beyond the scope of this illustrative analysis to perform
detailed area-specific analyses of the predicted additional emissions
reductions needed to meet various air quality goals.  Instead, based on
existing air quality sensitivity modeling, EPA developed several simple,
generic relationships of the expected air quality improvement to be
achieved as a result of ozone precursor reductions.  These relationships
are referred to here as "impact ratios" and have units of ppb of ozone
improvement per thousand tons of ozone precursor emissions reduction
(ppb/kton).  Two separate approaches were used to develop the impact
ratios.  The following paragraphs describe the development of the impact
ratios used in the extrapolated cost analysis of this RIA.  Based on
data presented later in this chapter and considering the uncertainties
and limitations of both approaches, we decided to use a single impact
ratio for NOx and a single impact ratio for VOC for the purposes of this
illustrative analysis for all areas in the U.S. that are included in the
extrapolated cost analysis.

4.1.1	Approach A: Use of Sensitivity Modeling of Local Emissions
Reductions

In this approach, the impact ratios were calculated based on modeling
results from four existing, 36 km CMAQ 2010 emissions sensitivity
simulations and a 2010 base case simulation derived from previously
completed modeling:

	

90% NOx reduction in all anthropogenic sectors in nine specific local
areas,

90% NOx reduction in all anthropogenic sectors over the rest of the
U.S.,

90% VOC reduction in all anthropogenic sectors in nine specific local
areas,

90% VOC reduction in all anthropogenic sectors over the rest of the U.S.

We calculated the ppb/kton ratios for five of the nine zones shown in
Figure 4.1 that are included in the extrapolated costs analysis: Dallas,
Atlanta, the Lake Michigan area, the Northeast Corridor, and central
California. It is expected that these five zones would provide a
representative range of ratios, so the analysis was not done for Denver,
Phoenix, and Salt Lake City.  Because we were not calculating
extrapolated tons for Seattle, the ratio determination was not done for
that region.  For monitoring sites in each of these five geographic
areas we compared the ozone improvement between the predicted ozone
concentrations in 2020, absent any additional controls for ozone, and
the 90% control cases (simulations 1 and 3) against the tons of NOx and
VOC reduced within the corresponding control area.  The impact ratio for
each site was calculated by dividing the ozone improvement by the
corresponding tons reduced.  Impact ratios were calculated for 88 sites
over the five analysis zones.  The results from Approach A are
summarized in Table 4.2

Figure 4.1:  Nine Local Control Areas in Existing 2010 Sensitivity Runs

The advantage to this approach is that it allows for all-sector,
local-only controls without consideration of transport effects.  This
approach is best-suited for areas in which ozone transport is not a
large contributor to the local ozone problem, relative to local
emissions (e.g., Atlanta, Dallas).

Table 4.1:  Summary of site-specific impact ratios over the five
analysis zones of Approach A.

	Minimum Impact Ratio 	Maximum Impact Ratio	Average Impact Ratio
Controlling County Impact Ratio

Atlanta	0.051	0.187	0.123	0.187

Central CA	0.077	0.106	0.095	0.106

Dallas	0.118	0.138	0.130	0.135

Lake Michigan Area	-0.022	0.052	0.010	0.032

Northeast Corridor	0.002	0.035	0.022	0.035

It is important to note that we are not able to factor in impacts of
controls outside of the local regions using this methodology and thus,
the impact ratios are likely to be conservative.  Additionally,
depending upon the source-receptor relationship at a particular
location, some impact ratios would be expected to be lower than others
due to prevailing transport direction.  For instance, one would not
expect a location in the southern portion of the Northeast Corridor to
show much local air quality improvement when the majority of the
controls were implemented upwind.  Other limitations to this approach
include: the assumption that response to NOx and VOC reductions is
linear between 0% and 90% control, the assumption that ratios developed
from 2010 base case modeling are applicable to 2020 post-strategy ozone,
and the fact that impact ratios calculated from a single month of 36 km
modeling may not be appropriate for an analysis of urban scale ozone.

A sample calculation for one of the sites in the five analysis zones (a
monitoring site located in Denton TX) is shown below:

A 90% NOx reduction equals 130.4 ktons in the local Dallas area.

The ozone improvement from this reduction was 17.6 ppb (87.9 to 70.3).

This yields an impact ratio of 0.135 ppb/kton for this county.

4.1.2	Approach B: Use of 2020 Baseline and RIA Control Scenario

In the second approach, we used the results from the 2020 baseline
(current standard, effectively .084 ppm) and the 2020 national .070
hypothetical control scenario to calculate impact ratios for Atlanta,
Houston, the Lake Michigan Area and the Northeast Corridor.  We focused
on these four analysis zones because they were expected to require
extensive extrapolated tons to attain the air quality targets.  We did
not use this approach in the western U.S. because there was very little
difference in the controls between those two cases in California.  We
calculated impact ratios for monitoring sites in each zone by dividing
the ozone change at each by the NOx emissions reductions that led to
that ozone reduction.  For the specific purpose of estimating impact
ratios, we have made the unrealistic but simplifying assumption that the
air quality change can be ascribed to the total NOx emissions changes
within 200 km of the area.  Different assumptions about which emissions
are responsible for the air quality change would yield different impact
ratios. 

The advantage to Approach B is that it allows for an estimate of the
impact of actual controls applied regionally because controls in the
hypothetical 2020 .070 run cover nearly the entire eastern US.  Thus,
this approach is best suited for areas in which ozone transport is a
large contributor to the local ozone problem (e.g., the Lake Michigan
area and the Northeast Corridor).  The primary disadvantage to this
approach is that the 2020 .070 control scenario is weighted toward
non-EGU point source controls which may result in non-homogeneous
reductions and thereby affect individual county impact ratios.  Impact
ratios were calculated for 47 counties over the four analysis zones. 
The results from Approach B are summarized in Table 4.2.

A sample calculation for one of the counties (Kenosha WI) is shown
below:

The RIA control scenario resulted in a NOx reduction of 16.8 ktons in
the Chicago zone.

The ozone improvement from this reduction was 1.6 ppb (86.6 to 85.0).

This yields an impact ratio of 0.095 ppb/kton for this county.

Table 4.2:  	Summary of site-specific impact ratios over the four
analysis zones of Approach B.

	Minimum Impact Ratio 	Maximum Impact Ratio	Average Impact Ratio
Controlling County Impact Ratio

Atlanta	0.041	0.129	0.068	0.070

Houston	0.050	0.057	0.054	0.057

Lake Michigan Area	-0.006	0.095	0.064	0.095

Northeast Corridor	0.068	0.155	0.110	0.105

4.2	Results from Impact Ratio Analyses

In general, both approaches indicate that impact ratios could range
between 0.03 and 0.20 ppb/kton.  However, the approaches did not yield
consistent impact ratios for individual analysis zones.  Individual
local impact ratios are likely influenced by: the importance of
transport, the local NOx/VOC ratio, the meteorology within the region,
and the location of monitors relative to specific source areas.

Table 4.3 shows the impact ratios for each of the controlling counties
within the areas considered.  Figure 4.2 shows the range of
county-specific impact ratios calculated over the four areas included in
the calculations for Approach B.  Based on these data and considering
the uncertainties and limitations of both approaches, we decided to use
a single impact ratio for NOx and a single impact ratio for VOC for the
purposes of this illustrative analysis for all areas in the U.S. that
are included in the extrapolated cost analysis.  These general impact
ratios are:

NOx impact ratio = 0.100 ppb/kton

VOC impact ratio = 0.025 ppb/kton

Table  4.3.  The NOx impact ratios at the controlling counties for each
methodology over the analysis zones.

Analysis Area	Impact Ratio at controlling county

	Approach A	Approach B

Atlanta	0.187	0.070

Central California	0.106

	Dallas	0.135

	Houston

0.057

Lake Michigan area	0.032	0.095

Northeast Corridor	0.035	0.105

Figure  4.2.  The NOx impact ratios at each county (sorted from lowest
to highest) for the Approach B over the four analysis areas

The selection of a 0.100 ppb/kton ratio was based on a consideration of
all estimated impact ratios from the bounding exercise of both
approaches and the technical limitations of  approaches.  There were
three specific reasons why we thought 0.100 ppb/kton represented the
best choice for extrapolating the tons needed to attain an air quality
target beyond the reductions from the RIA control scenario:

0.100 is within, and near the midpoint of,  the 0.03 to 0.20 range

0.100 is very close to the median value from Approach B (0.093 ppb/kton)

0.100 is very close to the average value at the key sites (0.091
ppb/kton).

The various methods did not generate consistent area-specific NOx impact
ratios.  Actual area-specific impact ratios are likely influenced by:
importance of transport, local NOx/VOC ratios, meteorology, and the
location of monitors relative to source areas. Higher impact ratios
would yield lower estimates of needed extrapolated tons and lower impact
ratio estimated would yield higher extrapolated tons/costs.  

Note: A sample calculation for “Area X” will be provided in a
subsequent version of Chapter 4. 

We intend to conduct additional sensitivity modeling for the final RIA
to improve the estimates of extrapolated tons needed to meet various
targets.   While it is premature to specify the exact nature of these
simulations, we expect this modeling to provide more information about
the non-linear responsiveness of ozone, the geographic variation in
ozone responsiveness, the impacts of local versus upwind emissions
reductions, and the relationship between NOx and VOC controls in various
areas.

4.3	Determination of Extrapolated Tons Control Areas

The extrapolated tons analysis varied slightly from the geographic areas
in which controls were applied for the illustrative 0.070 control
strategy described in Chapter 3.  In the extrapolated tons analysis, we
aggregated all counties that were above the air quality goal into
discrete control areas, that is, areas from which the tons would need to
be extracted in order to meet the target.  These control areas were
either regional, statewide, or local depending upon the nature of the
ozone problem within the area.  Two regional areas were identified: the
Ozone Transport Region and the Lake Michigan region.  Both of these
areas have traditionally employed multi-State control plans to lower
ozone in those regions.  For states with multiple areas above the air
quality target, we assumed that statewide control programs would be
developed to bring these areas into attainment.  For example, for the
0.065 ppm target, Ohio exceeds the air quality target in Cincinnati,
Cleveland, and Columbus.  We assumed that extrapolated tons could be
achieved anywhere in Ohio to meet the targets in all three areas.  All
remaining counties were treated as places where local controls would be
effective.  The only exceptions to the statewide assumption were in
Texas and California.  We separated the El Paso area into its own area
due to its distance (i.e., far greater than 200 km, which was the
distance used for the 0.070 control strategy) from the Eastern Texas
areas (Dallas, Houston).  In California, we combined the Sacramento and
San Joaquin Valley counties into a single control area, but created a
separate control area for Southern California.  Table 4.4 shows how the
monitoring counties were aggregated into the extrapolated tons control
areas for the 0.070 ppm target.

Table  4.4  List of ozone monitoring counties and how they were
aggregated into extrapolated tons control areas for the 0.070 air
quality target.

4.4   	Selection of Air Quality Goal for this analysis

Under the Clean Air Act, areas are required to reach the air quality
standards as expeditiously as practicable and within certain statutorily
defined time periods.   In advance of formal designations and ozone
pollution level classifications, which will depend upon future air
quality data, it is uncertain when areas would be required to attain a
new ozone standard.  In addition, states may request, and EPA must
grant, a higher classification which under the law provides flexibility
for a state to justify a later attainment date. (The state
implementation plan must show that the attainment date selected for an
area is as expeditious as practicable, and no later than the maximum
statutory date for the area's classification.)  In view of these and
other factors, it is beyond our capability to simulate in advance the
state implementation process to determine the appropriate attainment
date and required controls for each potential nonattainment area for a
new standard.  Instead, we have constructed an illustrative analysis
that provides a level playing field for comparison of the impacts of
potential new, alternative standards.

An important consideration in the determination of the amount of air
quality improvement needed to reach a tighter ozone standard is the
dates by which each area must come into attainment.  As discussed
earlier, for several analytical reasons we selected the year 2020 (i.e.,
approximately 10 years from designations), as the analytical target year
for this analysis.  Therefore, this analysis presents two sets of
results.  The first reflects attainment of the alternative ozone
standards in all locations of the U.S. except two areas of California in
2020.  These two areas of California are not planning to meet the
current standard by 2020 (see discussion below), so the estimated costs
and benefits for these areas are based on reaching an estimated progress
point (their “glidepath” targets) in 2020.  The second set of
results, for California only, estimate the costs and benefits from
California fully attaining the alternative standards in a year beyond
2020 (glidepath estimates, plus the increment needed to reach full
attainment beyond 2020, added together for a California total). However,
as noted above, we are not attempting to prejudge the attainment dates
and controls that ultimately will be determined through the SIP process,
and it may turn out that attainment occurs later than 2020 for
additional areas, particularly in areas where the future SIP process
shows that very high-cost controls would be needed to attain by 2020. 
For reasons explained below, assuming longer attainment dates would
reduce costs and benefits of meeting the current and alternative
standards, and would reduce costs more sharply in areas assumed to
employ high-cost controls to meet an artificial deadline.  

The South Coast (Los Angeles area) and San Joaquin Air Quality
Management Districts recently have proposed for comment state
implementation plans with the statutory maximum 20-year attainment dates
(June 2024, with attainment-level reductions by 2023) for meeting the
current 8-hour standard, which would involve a request to reclassify
those two areas to the “extreme” classification. This presented an
analytical dilemma for this analysis because assuming that these areas
would be classified severe or extreme for purposes of a new standard,
these areas would not be required to attain any new standard until after
the analytical year of 2020.  If an area is initially classified severe,
the law still would allow the state to request reclassification to
extreme and to demonstrate that a 20-year attainment date (e.g., in
2030, if designations occurred in 2010) is as expeditious as
practicable.  Thus, an assumption that these areas would attain a
tighter standard by 2020, significantly earlier than would be required
under the Clean Air Act, would artificially inflate both the costs and
benefits of the nation attaining the new standard in 2020 on a national
level. 

A further reason that we believe it would be inappropriate for the
analysis to assume attainment by 2020 with new, more stringent
alternative standards in the San Joaquin and South Coast areas is that
existing rules, especially for on-road and non-road mobile sources, will
achieve substantial additional reductions in NOx and VOC after 2020
before reaching their full impact in 2030.  If San Joaquin and South
Coast received the maximum statutory 20-year attainment dates for new
alternative standards, for example, they would have an attainment date
in 2030, and would benefit from reductions in NOx and VOC from existing
rules between 2020 and 2030.  By 2029, existing rules for onroad and
nonroad engines would achieve 62,000 tons of residual emissions
reductions needed for attainment at no cost beyond the baseline for this
analysis.   By contrast, assuming 2020 attainment for these areas would
result in assuming additional high-cost reductions from unknown control
measures.  Therefore, assuming 2020 attainment for these areas could
result in a significant overestimate of costs.  Likewise, the benefits
would be overestimated because the tons are attributable to these
existing rules that have reductions occurring after 2020 and are not
part of our hypothetical control strategy. 

Thus, for this analysis we have chosen to present the 2020 costs and
benefits in a way that reflects partial attainment in certain California
areas, an outcome consistent with the Clean Air Act.  This national
estimate includes full attainment in all locations except two areas of
California, which do not plan to meet the current standard by 2020, and
so have estimates for a progress point in 2020 (their “glidepath”
targets). The second set of results presents a total for California
only, which adds the 2020 progress point to the additional tons of
emissions that may be needed in California to fully attain the standards
in a year beyond 2020.

The following table shows the results of the calculation of the
glidepath targets for these two areas used in this analysis.  The
glidepath targets reflect the more stringent of two air quality targets:
 (1) the improvement assumed by 2020 to meet the current standard by
years specified below, or the improvement needed by 2020 to make linear
air quality progress between 2010 and a post-2020 attainment date for
the more stringent, alternative standards.  For Los Angeles County, the
glidepath air quality targets below for all three alternative standards
are set based on reductions needed to meet the current standard, with
the level of the current standard being achieved in 2021.  For Kern
County in the San Joaquin area, the glidepath for the .075 alternative
standard is based on achieving the level of the current standard by
2020.  For the other two alternative standards, the 2020 glide path
targets for San Joaquin are based on meeting the level of the
alternative, more stringent standards in 2025.

	

Table 4-5:  2020 Air Quality Glidepath Targets for LA and Kern County

Alternative Standard Level	LA County	Kern County

.075 ppm	 86.9 ppb*	84.9 ppb

.070 ppm	  86.9 ppb	82.9 ppb

.065 ppm	  86.9 ppb	79.9 ppb

* targets are expressed in ppb for clarity of presentation

As noted above, since our glidepath calculations and cost-benefit
estimates were made, the two California districts have proposed state
implementation plans for the current standard that allow the statutory
maximum 20-year period for attainment.  This in turn suggests that that
it would be reasonable solely for purposes of this analysis to assume a
20-year period for implementation of new standards.  In part because
decisions regarding our analysis were made prior to the California
proposals, the assumed time periods in this analysis for attainment by
the San Joaquin and Los Angeles areas are shorter -- both for the
current standards, and for the potential alternative standards.  This
suggests that the glidepath figures above are all more stringent than
likely implementation of the Clean Air Act, and that as a result our
analysis applies more unknown controls than would be needed in these
areas for the current and alternative standards assuming 20-year
deadlines.  Thus, our estimated 2020 costs and benefits for the two
California areas, which influence the total cost and benefit figures in
this draft RIA, are higher than would likely occur under the Clean Air
Act for the current and the potential alternative standards.  We intend
to consider this issue further in the final RIA.

4.5	National 2020 Estimates of Additional Emissions Reductions Needed to
Meet Three Potential Air Quality Targets

This analysis presents two sets of estimates: national 2020 estimates,
and California-only estimates.  This section presents the national 2020
estimates.

The national 2020 estimates assume full attainment in all locations
except two areas of California, which are assumed to meet 2020 air
quality glidepath targets on their way toward full attainment after
2020.  These 2020 national estimates present incremental tons that may
be needed to meet the three separate air quality targets were considered
as part of this analysis: 0.075 ppm and 0.070 ppm, which bound the range
that is being proposed, and a more stringent alternative of 0.065 ppm. 
After the RIA control scenario, there were 50, 126, and 280 counties
above these three thresholds, respectively.  The aggregation technique
discussed above grouped these counties into 11, 20, and 29 extrapolated
ton control areas for the three targets.  The calculation of additional
tons needed does not account for the effects of ozone transport
reductions (e.g. the impact of Lake Michigan region reductions on the
OTR).  The national 2020 total estimated incremental tons that may be
needed to attain the three targets are summarized below and presented in
Tables 4.5 - 4.7.

0.075 = 467,000 tons of additional NOx control

0.070 = 1,230,000 tons of additional NOx control

0.065 = 2,535,000 tons of additional NOx control

Table 4.6   Estimated Annual Incremental Tons Needed for an 0.065 ppm
Air Quality Target in 2020 (29 areas)

Control Region	Controlling County	Post-scenario design value (ppb)
Incremental Extrapolated NOx Tons

Lake Michigan region	Kenosha WI	85.0	174,000

Ozone Transport Region	Fairfield CT	87.1	173,000

Eastern TX areas (Houston/Dallas/Beaumont)	Harris TX	90.5	166,000

VA areas (Norfolk/Richmond/Roanoke)	Suffolk City VA	80.8	149,000

Detroit, MI	Macomb MI	78.4	125,000

Phoenix, AZ	Maricopa AZ	77.6	117,000

Denver, CO	Jefferson CO	76.9	110,000

OH areas (Cleveland/Columbus/Cincinnati)	Geauga OH	76.5	106,000

Atlanta, GA	Fulton GA	76.0	101,000

St Louis, MO-IL	St Louis City MO	75.7	98,000

Indiana areas (Indianapolis / Evansville)	Shelby IN	74.5	86,000

LA areas (Baton Rouge/New Orleans/Shreveport)	E Baton Rouge LA	74.4
85,000

KY areas (Louisville/Paducah/Bowling Green)	Clark IN	74.0	81,000

TN areas (Knoxville/Memphis/Nashville)	Crittenden AR	72.9	70,000

NC areas (Charlotte / Raleigh)	Mecklenburg NC	72.3	64,000

Salt Lake City, UT	Salt Lake UT	72.2	63,000

Las Vegas, NV	Clark NV	72.0	61,000

FL areas (Tampa / Panama City / Pensacola)	Hillsborough FL	71.4	55,000

Sacramento / San Joaquin Valley / S Fran	Kern CA**	96.3	50,000

Jackson, MS	Jackson MS	70.6	47,000

New Mexico areas (Farmington / Las Cruces)	Dona Ana NM	70.3	44,000

OK areas (Tulsa, Marshall)	Tulsa OK	70.3	44,000

Huntington, WV-KY	Cabell WV	69.9	40,000

El Paso, TX	El Paso TX	69.3	34,000

Kansas City, MO/KS	Wyandotte KS	69.0	31,000

Little Rock, AR	Pulaski AR	68.7	28,000

Mobile AL	Mobile AL	68.6	27,000

Columbia, SC	Richland SC	66.9	10,000

Los Angeles South Coast Air Basin, CA	Los Angeles CA**	105.0	0*

*In EPA’s illustrative analysis for the PM NAAQS RIA, there were
reductions of NOx in California.  The amount of reductions assumed there
are sufficient for these counties to achieve their glidepath targets in
2020.

** Los Angeles and Kern Counties have expected attainment dates after
2020.  This analysis counts the portion of reductions assumed by this
analysis by 2020 or earlier.  

Table  4.7.  Estimated Annual Incremental Tons Needed for an 0.070 ppm
air quality target in 2020 (20 areas)

Control Region	Controlling County	Post-scenario design value (ppb)
Incremental Extrapolated NOx Tons

Lake Michigan region	Kenosha WI	85.0	124,000

Ozone Transport Region	Fairfield CT	87.1	123,000

Eastern TX areas (Houston/Dallas)	Harris TX	90.5	116,000

VA areas (Norfolk/Richmond)	Suffolk City VA	80.8	99,000

Detroit, MI	Macomb MI	78.4	75,000

Phoenix, AZ	Maricopa AZ	77.6	67,000

Denver, CO	Jefferson CO	76.9	60,000

OH areas (Cleveland/Columbus/Cincinnati)	Geauga OH	76.5	56,000

Atlanta, GA	Fulton GA	76.0	51,000

St Louis, MO-IL	St Louis City MO	75.7	48,000

Indiana areas (Indianapolis)	Shelby IN	74.5	36,000

LA areas (Baton Rouge)	E Baton Rouge LA	74.4	35,000

KY areas (Louisville)	Clark IN	74.0	31,000

Sacramento / San Joaquin Valley	Kern CA**	96.3	20,000

TN areas (Memphis)	Crittenden AR	72.9	20,000

NC areas (Charlotte)	Mecklenburg NC	72.3	14,000

Salt Lake City, UT	Salt Lake UT	72.2	13,000

Las Vegas, NV	Clark NV	72.0	11,000

FL areas (Tampa)	Hillsborough FL	71.4	5,000

Los Angeles South Coast Air Basin, CA	Los Angeles CA**	105.0	0*

* In EPA’s illustrative analysis for the PM NAAQS RIA, there were
reductions of NOx   in California.  The amount of reductions assumed
there are sufficient for these counties to achieve their glidepath
targets in 2020.

** Los Angeles and Kern Counties have expected attainment dates after
2020.  This analysis counts the portion of reductions assumed by this
analysis by 2020 or earlier.  

Table 4.8.  Estimated Annual Incremental Tons Needed for an 0.075 ppm
air quality target in 2020 (11 areas)

Control Region	Controlling County	Post-scenario design value (ppb)
Incremental Extrapolated NOx Tons

Lake Michigan region	Kenosha WI	85.0	74,000

Ozone Transport Region	Fairfield CT	87.1	73,000

Eastern TX areas (Houston/Dallas)	Harris TX	90.5	66,000

VA areas (Norfolk)	Suffolk City VA	80.8	49,000

Detroit, MI	Macomb MI	78.4	25,000

Phoenix, AZ	Maricopa AZ	77.6	17,000

Denver, CO	Jefferson CO	76.9	10,000

OH areas (Cleveland)	Geauga OH	76.5	6,000

Atlanta, GA	Fulton GA	76.0	1,000

Sacramento / San Joaquin Valley	Kern CA**	96.3	0*

Los Angeles South Coast Air Basin, CA	Los Angeles CA**	105.0	0*

*In EPA’s illustrative analysis for the PM NAAQS RIA, there were
reductions of NOx in California.  The amount of reductions assumed there
are sufficient for these counties to achieve their glidepath targets in
2020.

** Los Angeles and Kern Counties have expected attainment dates after
2020.  This analysis counts the portion of reductions assumed by this
analysis by 2020 or earlier.  

4.6  	Estimates of Additional Tons Needed for Three Potential Air
Quality Targets (California only, post-2020 Attainment)

The second estimates presented are for California only.  Tables 4.8 –
4.10 below, present the estimated tons needed to attain California’s
glidepath targets in 2020 and the additional increment of tons that may
be needed for full attainment in a year beyond 2020

Table 4.8   California:  Estimated Tons Needed For Attainment 0.065 ppm
air quality target (beyond 2020)

Control Region	Controlling County	Post-scenario design value (ppb)	Total
Extrapolated NOx Tons	Glidepath Extrapolated NOx Tons	Remaining tons
needed (2020- attainment)	“Credit” tons from mobile rules

2020-2030	Tons needed after mobile reductions

Sacramento / San Joaquin Valley / S Fran	Kern CA	96.3	190,000	50,000
140,000	23,300	116,700

Los Angeles South Coast Air Basin, CA	Los Angeles CA	105.0	188,000	0
188,000	38,500	149,500

 

Table 4.9  California:  Estimated Tons Needed for Attainment of 0.070
ppm air quality target (beyond 2020)

Control Region	Controlling County	Post-scenario design value (ppb)	Total
Extrapolated NOx Tons	Glidepath  Extrapolated NOx Tons	Remaining tons
needed (2020- attainment)	“Credit” tons from mobile rules

2020-2030	Tons needed after mobile reductions

Sacramento / San Joaquin Valley	Kern CA	96.3	140,000	20,000	120,000
23,300	96,700

Los Angeles South Coast Air Basin, CA	Los Angeles CA	105.0	138,000	0
138,000	38,500	99,500

 

Table 4.10 California:  Estimated Tons Needed for Attainment of 0.075
ppm air quality target (beyond 2020)

Control Region	Controlling County	Post-scenario design value (ppb)	Total
Extrapolated NOx Tons	Glidepath Extrapolated NOx Tons	Remaining tons
needed (2020- attainment)	“Credit” tons from mobile rules

2020-2030	Tons needed after mobile reductions

Sacramento / San Joaquin Valley	Kern CA	96.3	90,000	0	90,000	23,300
66,700

Los Angeles South Coast Air Basin, CA	Los Angeles CA	105.0	88,000	0
88,000	38,500	49,500

 

 The negative value of minimum impact ratio in the Lake Michigan area
indicates that ozone levels at one monitoring site are projected to
increase slightly with 90% local NOx control.  This 'ozone disbenefit'
has been projected by the model to occur in a very few, highly
localized, areas with large amounts of NOx emissions.  This lone
negative value is not representative of regional impact ratios."

  The controlling county is the county within an area whose design value
is farthest away from attaining the air quality target.

 The lone negative value of impact ratio occurs in the Lake Michigan
area and indicates that ozone levels at that site are projected to
increase slightly in response to the RIA control scenario.  This 'ozone
disbenefit' has previously been projected by the model to occur in a
very few, highly localized, areas with large amounts of NOx emissions. 
This lone negative value is not representative of regional impact
ratios.

 Proposed State Strategy for California's State Implementation Plan
(SIP) for the New PM2.5 and 8-Hour Ozone Standard, California Air
Resources Board web page,
http://www.arb.ca.gov/planning/sip/2007sip/2007sip.html, update May 30,
2007.

 62,000 tons was estimated by subtracting the California county level
Onroad and Nonroad 2030 NOx and VOC emissions from their totals in 2020.
 These differences were estimated for counties listed under the CA
control regions (Los Angeles and Kern County) detailed in Table 4.4.
(Los Angeles accounted for 38,500 tons, while Kern accounted for 23,300
tons, for a total of 61,800 rounded to 62,000).  In order to estimate
total emissions for both VOC and NOx, VOC emission reductions for these
counties were adjusted using the adjustment factor detailed earlier in
the chapter (4 VOC tons = 1 NOx ton).  Given that the San Joaquin and
South Coast air quality management districts have adopted plans allowing
until June 2024 (20 years from designation) to meet the current
standard, EPA believes that it would be consistent for purposes of this
analysis to assume a 20-year period for attainment of a new more
stringent standard.  If designations occurred in 2010, the 20-year
attainment period would end in 2030.  Significant emissions reductions
from implementation of mobile source rules are anticipated between 2020
and 2030.  Consistent with the non-EGU growth assumptions for the rest
of the RIA, non-EGU emissions are assumed to stay constant. EGU
emissions are a small fraction of the California inventory and are
assumed not to significantly affect the change in the state’s
emissions between 2020 and 2030.  Accordingly, we have used the
difference between 2020 and 2030 mobile emissions to estimate the
post-2020 emissions reductions that will assist the two California areas
in reaching attainment.

 Assumptions made for the purposes of this analysis were made prior to
two California areas adopting SIPs which assumed attainment by June
2024.   For purposes of this analysis, San Joaquin (including Kern
County) was assumed to meet the current standard by 2020 (consistent
with the analysis assumption for most areas), and South Coast (including
Los Angeles County) was assumed to meet the current standard in 2021
(the maximum attainment date of a severe-17 area is in June 2021). 
Because the San Joaquin and South Coast air districts have adopted SIPs
with later attainment dates for the current standard,, we recognize that
the assumptions used in this analysis are not likely to be the actual
years of attainment for these two areas.  

 While the proposed rule takes comment on a range of alternate standards
from 0.060 ppm to 0.084 ppm, the RIA analysis focused on a more limited
range

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