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ENVIRONMENTAL PROTECTION AGENCY
Treasury Department
CFR Citation: 40 CFR Part 52
DC ID: [DC052-7007, MD143-3102, VA129-5065; FRL-7484-6]
NOTICE: Part III
DOCUMENT ACTION: Final rule.
SUBJECT CATEGORY: Approval and Promulgation of Air Quality Implementation Plans; District of Columbia, Maryland, Virginia; Post 1996 Rate-of-Progress Plans and One-Hour Ozone Attainment Demonstrations
EFFECTIVE DATES: This final rule is effective on May 19, 2003.
DOCUMENT SUMMARY: EPA is conditionally approving the severe ozone nonattainment
area State Implementation Plan (SIP) revision for the Metropolitan
Washington severe ozone nonattainment area. This SIP revision includes
the onehour severe ozone attainment demonstration, the 19961999 portion of the severe area rateofprogress (ROP) plan and
transportation control measures for the Metropolitan Washington DC
ozone nonattainment area (the Washington area) submitted by the
District of Columbia's Department of Health (DoH), by the Maryland
Department of the Environment (MDE) and by the Virginia Department of
Environmental Quality (VADEQ). EPA is conditioning approval on
commitments submitted by DoH, MDE and VADEQ to submit adopted control
measures that qualify as contingency measures to be implemented for
failure of the Washington area to attain the onehour ozone standard
for serious areas by November 15, 1999 and adopted contingency measures
that will be implemented should the area fail to attain by the November
15, 2005 severe ozone attainment deadline or fail to achieve any post
1996 threepercent year emissions reduction requirement. Approval is
also conditioned on commitments that require the Washington area
jurisdictions to submit a revised rateofprogress plan that includes
emission reductions of ozone precursors of at least 3 percent per year
from November 15, 1999 to the November 15, 2005, an updated attainment
demonstration that reflects revised MOBILE6based motor vehicle
emissions budgets, a revised analysis of reasonably available control
measures (RACM) and to revise the attainment demonstration as necessary
to reflect the revised budgets and RACM analysis. Approval is also
conditioned on the Washington area jurisdictions submitting a SIP
revision that meets all of the requirements of a severe area SIP
including, but not limited to lower major stationary source thresholds,
revised offset ratios, any required transportation control strategies
and a fee requirement for major sources should the area fail to attain
by 2005.
SUMMARY: Environmental Protection Agency,
SUPPLEMENTAL INFORMATION
The use of ``we,'' ``us,'' or ``our'' in this document refers to EPA. This SUPPLEMENTARY INFORMATION section is organized to address the following questions:
I. What Action Is EPA Taking Today?
II. What Were the Conditions for Approval Provided in the Notice of
Proposed Rulemakings for the 19961999 ROP Plan and Attainment Demonstration?
III. What Comments Were Received on the Proposed Conditional Approvals and How Has EPA Responded to them?
IV. Applicability of Revised Motor Vehicle Emissions Budgets V. Final Action
VI. Statutory and Executive Order Reviews
I. What Action Is EPA Taking Today?
EPA is taking a final action to conditionally approve the
Washington area severe ozone nonattainment SIP. This SIP revision
includes previously submitted attainment demonstration and 19961999
ROP plan SIPs and contingency measures that now apply to the Washington
area as a severe area ozone nonattainment area. EPA is issuing a final
conditional approval on the basis that the Washington area
jurisdictions must revise and submit a severe area SIP that is
consistent with the principle that attainment must be achieved as
expeditiously as possible but no later than the severe ozone area
attainment deadline of November 15, 2005 and that the previously
submitted attainment demonstration and ROP SIPs must include
contingency measures, RACM, motor vehicle emissions budgets that are
consistent with a severe attainment deadline and all of the remaining
severe ozone nonattainment area requirements. On February 3, 2003 (68
FR 5246), EPA proposed to conditionally approve these SIP revisions as
a severe area attainment demonstration and only the 19961999 portion
of the Washington area's ROP obligation in accordance with section
110(k)(4) of the Clean Air Act (CAA), on the basis of commitments from
DoH, MDE and VADEQ to remedy these certain limited inadequacies. EPA
has since determined that the severe ozone nonattainment requirements
in their entirety are inseparable from the overall Washington Area
attainment demonstration. EPA is therefore authorized to conditionally
approve the attainment demonstration as a whole based on commitments
submitted on April 7 and 8, 2003, from Maryland, the District and
Virginia, respectively, to submit measures to complete the severe area
requirements to revise the previously submitted SIPs listed in Tables 1
and 2 of this notice to be consistent with and to include all of the
section 182(d) requirements of a severe ozone nonattainment area SIP.
The specific commitments submitted by the Washington area jurisdictions are to:
(A) Revise the 19961999 portion of the severe area ROP plan to
include a contingency plan containing those adopted measures that
qualify as contingency measures to be implemented should EPA determine
that the Washington area failed to achieve the required 9 percent rate ofprogress reductions by November 15, 1999.
(B) Revise the severe area ROP to provide emission reductions of
ozone precursors of at least 3 percent per year from November 15, 1999 to the November 15, 2005 severe ozone attainment date.
(C) Revise the severe area ROP plan to include a contingency plan
containing those adopted measures that qualify as contingency measures
to be implemented should EPA determine that the Washington area failed
to achieve the ROP reductions required for the post1999 period.
(D) Revise the Washington area severe attainment demonstration to
include a contingency plan containing those adopted measures that
qualify as contingency measures to be implemented for the failure of
the Washington area to attain the onehour ozone standard for serious areas by November 15, 1999.
(E) Update the Washington area severe attainment demonstration to [[Page 19107]]
reflect revised MOBILE6based motor vehicle emissions budgets,
including revisions to the attainment modeling/weight of evidence
demonstration and adopted control measures, as necessary, to show that
the SIP continues to demonstrate attainment by November 15, 2005.
(F) Revise the Washington area severe attainment demonstration to
include a contingency plan containing those measures to be implemented
if the Washington area does not attain the onehour ozone standard by November 15, 2005.
(G) Revise the Washington area severe attainment demonstration to
include a revised RACM analysis and any revisions to the attainment
demonstration including adopted control measures, as necessitated by such analysis.
(H) Revise the major stationary source threshold to 25 tons per year.
(I) Revise Reasonably Available Control Technology (RACT) rules to include the lower major source applicability threshold.
(J) Revise new source review offset requirements to require an offset ratio of at least 1.3 to 1.
(K) Submit as part of the SIP a fee requirement for major sources of volatile organic compounds (VOC) and nitrogen oxides
(NO
Details on EPA's analysis of the previously submitted SIP revisions and their adequacy with respect to the requirements of a severe ozone nonattainment area are explained in detail in the proposal notice and will not be restated here.
Under the CAA, EPA is required to approve or disapprove a State's submission no later than 12 months after the submission is determined or deemed complete. On November 13, 2002, the Sierra Club filed a complaint in the United States District Court for the District of Columbia (District Court) against the EPA (Sierra Club v. Whitman, No. 1:02CV02235(JR)) claiming, among other things, that the EPA had not issued a final action on several SIP revisions (those listed in Tables 1 and 2 of this document) submitted by the District, Maryland and Virginia for the Washington area. On December 18, 2002, the District Court issued an order directing the EPA to publish, by February 3, 2003, a notice of proposed rulemaking on these SIP revisions and to publish by April 17, 2003, a final rule on these SIP revisions. This final rulemaking action complies with the Court's Order to publish a final action on these SIP revisions by April 17, 2003.
Tables 1 and 2 identify the submittal and amendment dates for the
ROP plans and attainment demonstrations for which EPA is taking final action to conditionally approve.
Table 1.19961999 ROP Plans
DC MD VA
Initial submittal dates......... November 10, 1997.. December 24, 1997.. December 19, 1997.
Amendment dates................. May 25, 1999....... May 20, 1999....... May 25, 1999.
Table 2.Attainment Demonstrations
DC MD VA
Initial submittal dates......... April 24, 1998..... April 29, 1998..... April 29, 1998.
Amendment dates................. October 27, 1998... August 17, 1998.... August 18, 1998.
Supplemental dates.............. February 16, 2000.. February 14, 2000 February 9, 2000.
(MD SIP No. 0001).
Supplemental dates.............. March 22, 2000..... March 31, 2000 (MD March 31, 2000.
SIP No. 0002).
II. What Were the Conditions for Approval Provided in the Notice of
Proposed Rulemakings for the 19961999 ROP Plan and Attainment Demonstration?
Under section 110(k)(4) of the CAA, the EPA ``may approve a plan
revision based on a commitment of the State to adopt specific
enforceable measures by a date certain, but not later than 1 year after
the date of approval of the plan revision. Any such conditional
approval shall be treated as a disapproval if the State fails to comply
with such commitment.'' In the Notice of Proposed Rulemaking published
on February 3, 2003 (68 FR 5246), EPA proposed to conditionally approve
the Washington area severe attainment demonstration and 19961999
portion of the ROP plan on the basis that the Washington area
jurisdictions had committed to submit to EPA by April 17, 2004 revised SIPs that meet the following conditions.
(A) Revise the 19961999 portion of the severe area ROP plan to
include a contingency plan containing those adopted measures that
qualify as contingency measures to be implemented should EPA determine
that the Washington area failed to achieve the required 9 percent rate ofprogress reductions by November 15, 1999.
(B) Revise the Washington area severe attainment demonstration to
include a contingency plan containing those adopted measures that
qualify as contingency measures to be implemented for the failure of
the Washington area to attain the onehour ozone standard for serious areas by November 15, 1999.
(C) Update the Washington area severe attainment demonstration to
reflect revised MOBILE6based motor vehicle emissions budgets,
including revisions to the attainment modeling/weight of evidence
demonstration and adopted control measures, as necessary, to show that
the SIP continues to demonstrate attainment by November 15, 2005. [[Page 19108]]
(D) Revise the Washington area severe attainment demonstration to
include a contingency plan containing those measures to be implemented
if the Washington area does not attain the onehour ozone standard by November 15, 2005.
(E) Revise the Washington area severe attainment demonstration to
include a revised RACM analysis and any revisions to the attainment
demonstration adopted control measures as necessitated by such analysis.
III. What Comments Were Received on the Proposed Conditional Approvals and How Has EPA Responded to Them?
In EPA's Notice of Proposed Rulemaking published on February 3, 2003 (68 FR 5246) EPA proposed conditional approval of the Washington area's severe area attainment demonstration and the 19961999 portion of the severe area ROP obligation. EPA also proposed disapproval in the alternative to preserve the courtordered schedule to issue a final rule by April 17, 2003 in the event that EPA could not issue a final conditional approval with respect to either or both the attainment demonstration and 19961999 ROP plan. EPA received comments from the Virginia Department of Transportation on March 5, 2003 supporting EPA's proposed conditional approval. These comments will not be addressed here. On March 5, 2003 EPA also received comments from the Sierra Club. The Sierra Club's March 5 comments specifically incorporate by reference comments submitted by the Sierra Club and others on February 14, 2000, October 30, 2000, November 15, 2000, November 20, 2000, September 9, 2002, and December 13, 2002.
To the extent that the previously submitted comments are germane to
the current action, EPA generally incorporates by reference its prior
responses to those comments published at 66 FR 586, January 3, 2001,
and 68 FR 5246, February 3, 2003. We respond with particularity to many
of the previously submitted comments (1) to the extent that events
occurring after publication of EPA's prior responses require that our
prior responses be updated and revised or (2) to the extent that we
feel that consolidating prior responses helps create a more
comprehensive record for the current rulemaking. The following discussion summarizes and responds to particular comments.
A. Comments in the March 5, 2003
1. Conditional Approval
Comment: The commenter argues that EPA cannot conditionally approve the Washington area SIPs for various reasons. First, the commenter alleges that even EPA concedes that it cannot fully approve the SIPs based on various defects noted by the D.C. Circuit court in Sierra Club v. Whitman, 294 F.3d 155, 163 (D.C. Cir. 2002), therefore, EPA cannot conditionally approve the SIPs. The commenter further alleges that conditional approval cannot be used to circumvent or postpone statutory deadlines, and that conditional approval will prevent the Washington area from attaining the ozone standard as expeditiously as possible, prevent achievement of Post1999 ROP and prevent timely implementation of contingency measures in the event the area fails to achieve timely rateofprogress or attainment. The commenter also asserts that conditional approval cannot be used when a state has failed to submit a relevant substantive SIP component at all; that the SIP components at issue were due on November 15, 1994; that the States' commitments do not identify ``specific enforceable measures'' to be adopted by a date certain; that the commitments are to fix major components not minor details; that conditional approval is not allowable here because EPA has already allow the States to defer submission of various required SIP components for more than one year; and finally, that all of the defects the commenter has identified means any conditional approval would violate section 110(l) of the Act.
Response: The commenter misconstrues the conditional approval mechanism. Conditional approval under section 110(k)(4) is quite different from full approval under section 110(k)(3) of the Act, which the Court of Appeals considered in Sierra Club. Conditional approval is a statutory technique that allows EPA to give a limited form of approval to SIPs that do not meet all of the standards for full approval, but where a substantive SIP also includes commitments made by the states to remedy limited, identified deficiencies through the adoption of specific enforceable measures by a date certain. 42 U.S.C. 7410(k)(4). Here, the States have committed to undertake various analyses and ultimately adopt specific enforceable measures as appropriate to remedy the deficiencies in the currently submitted SIP revisions. Based on the fact that the SIP contains most of the substantive components for the required plans as well as commitments to correct limited deficiencies, which EPA received after the court ruling, the statute provides for EPA to conditionally approve the SIPs even though the court found that EPA could not fully approve them. The Court of Appeals did not address whether EPA could conditionally approve the SIPs as the issue of conditional approval was not before the court and the States had not made appropriate commitments at the time of the court ruling.
With respect to the assertion that EPA cannot use the conditional approval mechanism to allow areas to avoid a statutory deadline, and the complaint about SIP submittal deadlines that have long passed, EPA is dealing in this case with a SIP that was submitted by the States, reviewed by EPA and approved by EPA in January 2001 through noticeand comment rulemaking. EPA's approval was then vacated by the Court of Appeals on July 2, 2002, after judicial review. Whatever the merits of any argument about delays that occurred previously, EPA must now take action on the SIPs under court order based on the submittal before the agency. That submittal consists of the previously submitted SIP and the recently submitted commitments by the States to conduct the appropriate analyses and submit any necessary measures to rectify certain limited defects in the SIPs. EPA believes it is appropriate to conditionally approve the SIPs that the States have recently committed to revise to satisfy deficiencies which were the basis for vacatur by the Court of Appeals. The States could not have been expected to remedy these deficiencies previously as EPA had in fact approved the SIPs without noting any such deficiencies prior to the court ruling. The States have now committed to revise the SIPs on an expeditious schedule that is no later than one year following EPA's final action. Furthermore, EPA notes that there is nothing in the statute that limits the use of conditional approval to SIP revisions that are submitted by the statutory due date. Nor does the statute link the period for conditional approval to the time by which the SIP was due. Finally, EPA has never before conditionally approved these SIPs nor have the States previously made commitments to submit all of these portions of the attainment demonstration within a year. For these reasons, EPA believes it is reasonable to use this tool in this case.
The commenter further claims that a conditional approval will delay
timely attainment. However, the commitments are to submit any necessary
additional measures by April 2004 while the attainment date for the area is not until
[[Page 19109]]
November 2005, so all deficiencies will be cured at least 18 months
prior to the attainment date and will therefore not delay timely
attainment because the States will need to ensure any necessary
emission controls are in place by the beginning of the 2005 ozone
season. One year should provide sufficient time to implement any
necessary controls. To the extent the commenter addresses alleged
deficiencies in the 2005 attainment date itself, these comments will be
addressed in section III.A.2. of this document responding to comments on the attainment demonstration.
The commenter next claims that EPA cannot use the conditional approval mechanism where states have failed to submit a substantive SIP component at all, alleging that in this case various parts of the attainment demonstration, such as ROP plans, contingency measures and RACM, constitute separate SIP components. EPA had indeed argued in Sierra Club, supra, that these were separate SIP requirements and for that reason the attainment demonstration should have been upheld without them. However, the Court of Appeals agreed with the contrary argument, which was actually made by the commenter, and held that ROP plans, RACM and contingency measures are actually parts of the overall Washington Area attainment demonstration and must be included within it. See Sierra Club v. Whitman, 285 F.3d at 16364 (D.C. Cir. 2002). The attainment demonstration includes many components in addition to these. The attainment demonstration already demonstrates attainment no later than November 15, 2005, based on photochemical grid modeling and a suite of adopted and SIP approved control measures that reduce local emissions down to the allowable levels established by the photochemical grid modeling. A list of these control measures can be found in the notice of proposed rulemaking for this action. See 68 FR at 52525253 and at 52555256, February 4, 2003. Given that these items to which the States have committed are a part of the overall Washington area attainment demonstration rather than separate SIP components, EPA concludes that it is authorized to conditionally approve an attainment demonstration that contains commitments to submit limited components of the attainment demonstration.
The commenter then argues that these elements of the attainment demonstration are so significant that the SIPs cannot be conditionally approved without them. However, the primary portions of the attainment demonstration are the adopted control measures themselves coupled with the modeling demonstration showing that implementation of these measures will result in attainment by the requisite date. The RACM analysis merely analyzes potential additional measures to determine whether any could advance the attainment date; the post1999 ROP analysis addresses interim progress prior to the attainment date; and the contingency measures address measures to be implemented in the event rateofprogress or attainment is not timely achieved. Although all of these elements are important portions of the overall attainment demonstration SIP, EPA does not believe that any of them amount to such a significant portion of the attainment demonstration that the demonstration cannot be conditionally approved based on the States commitment to complete the additional analyses along with adoption of any necessary additional measures in the short term. EPA addresses the commenters specific concerns about the substance of these three SIP portions elsewhere in responding to comments regarding the individual elements of the attainment demonstration.
Further, the commenter alleges that conditional approval is inappropriate in this case because the States have purportedly not made commitments to adopt specific enforceable measures as required by section 110(k)(4). In contrast, EPA believes that the commitments submitted by the States do indeed commit the States to ultimately adopt specific enforceable measures if such measures are determined to be needed based on further analysis. The commitment letters specifically state that the States will submit adopted contingency measures requisite to satisfy the contingency measure requirements for various circumstances relating to ROP and attainment. The States further commit not only to conduct the various RACM and mobile modeling analyses, but also to revise the attainment demonstration itself as appropriate in light of these analyses. EPA believes that there can be no interpretation of these commitment letters other than a conclusion that the States have committed to submit specific enforceable measures to support the revised attainment demonstration if necessary. However, since the States have submitted additional commitment letters for various reasons described elsewhere in this document, the States have clarified in those letters their intent to submit specific measures in support of the demonstrations, if appropriate. It is true that the States have not yet identified the specific measures that could ultimately be adopted, however it would be impossible for them to do so in advance of conducting the requisite RACM and modeling analyses.
The commenter argues that contingency measures should not be the subject of a conditional approval in DC because it is likely that by the summer of 2003 it could be determined that the DC area will fail to attain in 2004 and the contingency measures would then be triggered. However, contingency measures are not required to be implemented under the Act until an area fails to attain by the applicable attainment date. (CAA section 172(c)(a)). The statute does not require implementation of contingency measures prior to the attainment date based on a projection that the area will not attain when the attainment date is reached. Given that the States have committed to submit all necessary contingency measures by April 2004, any needed contingency measures would be available for implementation should EPA make a determination by May 15, 2006 under section 181(b)(2) of the Act that the area failed to attain by November 15, 2005.
We also disagree with the commenters' allegation in comments previously submitted on September 9, 2002 that the motor vehicle emissions budgets (MVEBs) in the attainment demonstration do not reflect the potential to lower the MVEB through transportation related control measures should the area fail to attain or to meet ROP requirements. With respect to those contingency measures that would be triggered by the failure to attain, the attainment year MVEB would never account for these contingency measures because such measures would never be triggered until after the attainment year. Should those contingency measures be triggered, it would be appropriate at that time for the state to revise the budgets to reflect implementation of such measures in future years, but this cannot be done in advance of implementation of the measures as it is unclear whether the measures would ever in fact be implemented.
Similarly, with respect to contingency measures triggered by the
failure to meet ROP, the obligation to account for those contingency
measures is not triggered until it has been determined that the area
has failed to meet its ROP requirements. EPA is allowing the Washington
area jurisdictions to demonstrate the first required post1999 nine
percent ROP (which was due under the statute by November 15, 2002), as [[Page 19110]]
expeditiously as practicable, if control measures currently in the
SIPs, or already promulgated by EPA, did not achieve the required nine
percent reduction by November 15, 2002. (See 68 FR 3418). Therefore,
the date for fulfilling the first post1999 ROP requirement lies in the
future, and the requirement to implement any needed contingency
measures for failure to meet that ROP has not been, and may not ever
be, triggered. This is true, too, for the 1999 ROP requirement. It has
not yet been determined that the Washington area did, or did not, meet
its 1999 ROP requirement and the requirement to implement contingency
measures for failure to meet the 1999 ROP requirement has not yet been
(and may not ever be) triggered. As with any contingency measures that
would be implemented for a future failure to attain, because the
obligation to implement contingency measures for failure to meet the
post1999 ROP requirements has not arisen, the area has no obligation
to account for these measures in the attainment demonstration MVEB.
Finally, the commenter argues that all the defects it has asserted entail that any conditional approval would violate section 110(l) of the Act, which prohibits EPA from approving a SIP revision that would interfere with any applicable requirement of the Act. However, EPA has concluded that the submitted attainment demonstration, coupled with the commitments the States have made to remedy the deficiencies in their demonstrations, fully satisfy all of the applicable requirements of the Act requisite to support a conditional approval.
2. Attainment Demonstration
a. RACM and Attainment as Expeditiously as Practicable.
Comment: The commenter argues that the submitted SIPs do not provide for attainment as expeditiously as practicable, as required by the Act, because the States have not properly analyzed whether any additional RACMs could advance the 2005 attainment date.
Response: EPA acknowledges that the RACM analyses in the SIPs are
not sufficient, as noted by the Court of Appeals in Sierra Club, supra.
However, the attainment demonstration does provide for attainment by
2005, a date consistent with the outside statutory date for attainment
for severe ozone nonattainment areas and one that is only two years
away. EPA therefore concludes, in light of the States commitments to
conduct a RACM analysis and submit any additional measures determined
to constitute RACM within a year, that it is appropriate to
conditionally approve the attainment demonstration SIPs at this time.
Should the RACM analyses determine that there are in fact potential
RACM that could advance the attainment date, then EPA could approve an
earlier attainment demonstration including such measures. However, in
advance of completion of such RACM analyses EPA believes on the basis
of the attainment demonstration before it that the SIP does demonstrate
attainment as expeditiously as practicable. This preliminary conclusion
is neither arbitrary nor capricious given the short period of time
until the attainment date. Although no final conclusions can be reached
until the RACM analyses are completed, given the time necessary for
implementation of measures EPA believes it is unlikely that sufficient
measures could be adopted and implemented to allow the Washington area
to reach attainment by the 2004 ozone season. Specifically, the state
process for developing control requirements in the form of SIP
revisions, providing a public hearing, and adopting SIP revisions,
typically takes at least a full year. In addition, the state typically
allows a period of at least a year, often longer, for sources to
implement required controls. Even if these process were significantly
accelerated, it is highly unlikely that controls would be implemented by the start of the 2004 ozone season.
b. Demonstration of Attainment by 2005.
Comment: We received comments declaring that the attainment demonstration, and EPA's analysis of it, look only at ozone levels in 2005, not 2003 and 2004. The comments assert that to demonstrate attainment by November 15, 2005, the demonstration of attainment must show that no monitor in the nonattainment area will have an average of more than 1.0 expected exceedance per year for the period 20032005 but that the demonstration does not address the entire period. The comments cite Sec. 50.9 of 40 CFR part 50.
Response: EPA disagrees with the comment. While EPA does agree that Sec. 50.9 of 40 CFR part 50 establishes the form of the 1hour ozone standard in terms an annual average number of expected exceedances, EPA's guidance for conducting an attainment demonstration are a reasonable interpretation of the requirements for an attainment demonstration required under section 182(c) of the CAA in light of the form of the ozone NAAQS.
Air quality models do not know what year is being modeled, only the emissions levels and the meteorology. The meteorology component would be the same for any year because historical weather episodes are modeled.
Under EPA's modeling guidance the States are required to model severe episodes corresponding to those weather conditions thought to generate high levels of ground level ozone. In contrast, all monitored exceedances count towards a determination of whether all monitors are actually meeting the standard under the standard set in 40 CFR 50.9 and appendix H to 40 CFR part 50. A monitored value of 0.125 ppm counts as one exceedance to the same extent as a value of 0.150 ppm. Modeling demonstrating that the most severe episodes will yield few or no exceedances will be consistent with elimination of exceedances on less severe weather days.
As EPA stated in the technical support for this rule, the modeling demonstration considered severe episodes: the ozone forming potential rank is very high for one dayJuly 20, 1991. This is the thirteenth most severe day out of approximately the last 50 years, one that is likely to recur only once every 4 to 5 years on average. This type of day is not likely to occur often enough to be a major causative factor for nonattainment, especially since the emission controls modeled in this plan should eliminate ozone exceedances for all but the most meteorologically severe days.
EPA has concluded that the modeling analysis allows anthropogenic
emissions in the Washington area of 360 tons per day of VOC and 538 tons per day of NO
To reduce future year emissions to levels consistent with the modeling demonstration, the attainment demonstration has to provide for enough emission reductions net of growth to reduce emissions down to the levels allowed by the attainment modeling demonstration. Therefore, the attainment demonstration has to provide for emission reductions to accomplish two purposes: first, the plan has to offset growth in emissions due to increases in emissionsrelated activity to reduce emissions to the base year levels; and, second, the plan has to produce sufficient additional reductions beyond that needed to offset post1990 growth to reduce emissions to the levels allowed by the attainment modeling demonstration.
When viewed from this perspective, the Post1996 ROP plan for the
1999 milestone (hereafter ``the 19961999 ROP plan'') had to achieve reductions
[[Page 19111]]
net of growth of 128.3 tons per day of VOC and 116.2 tons per day of
NO
The attainment modeling considered the effects of the OTC Phase II
NO
\1\ These controls have been approved into the SIPs. See 65 FR
78416, December 15, 2000, and 65 FR 80783, December 22, 2000.
\2\ These controls have been approved into the SIPs. See 66 FR
55099, November 1, 2001, and 66 FR 1866, January 10, 2001; and 65 FR 78100, December 14, 2000
The Phase II RFG program is projected to yield 23.5 tons per day of VOC reductions in 2005 versus a little less than 16 in 1999. Much of this additional benefit would have been achieved in calendar year 2000 when the second phase of the program was implemented to achieve the mandated additional VOC reductions over and above that required by the first phase.
The attainment plan requires reductions net of growth of 148.5 tons
per day of VOC and 192.9 tons per day of NO
The Plan's local emissions levels are very close to that required
under the local air quality modeling in 1999 once the RFG and Phase II
NO
c. The Ozone Standard.
Comment: The commenter stated that EPA had based its proposed approval of the attainment demonstration on the assumption that the 1 hour ozone standard is 0.125 ppm, when the actual standard is 0.12 ppm.
Response: The level of the 1hour ozone National Ambient Air Quality Standard (NAAQS) is defined in 40 CFR 50.9 as 0.12 parts per million (ppm), not 120 parts per billion (ppb) as implied by the commenter. In other words, the 1hour ozone NAAQS is specified as two significant digits and the data handling approach employed to compare ambient air quality data to the 1hour ozone standard is to round to two decimal places as per the regulations and guidance referenced above.
Although the 1hour NAAQS itself includes no discussion of specific data handling conventions, EPA's publicly articulated position and the approach long since universally adopted by the air quality management community is that the interpretation of the 1hour ozone standard requires rounding ambient air quality data consistent with the stated level of the standard. EPA has clearly communicated the data handling conventions for the 1hour ozone NAAQS in regulation and guidance documents. In the 1990 Amendments to the CAA, Congress expressly provided that ``[e]ach regulation, standard, rule, notice, order and guidance promulgated or issued by the Administrator under this Act, as in effect before the date of the enactment of the Clean Air Act Amendments of 1990 shall remain in effect according to its terms * * *'' Thus, under the amended CAA, Congress expressly carried forth EPA interpretations set forth in guidance such as the guideline documents interpreting the NAAQS.
As early as 1977, two years before EPA promulgated the 1hour ozone
NAAQS, EPA provided in guidance that the level of the standard dictates
the number of significant figures to be used in determining whether the
standard was exceeded (see ``Guidelines for the Interpretation of Air
Quality Standards,'' OAQPS No. 1.2008, February 1977). In addition,
the regulations governing the reporting of annual summary statistics
from ambient monitoring stations for use by EPA in determining national
air quality status clearly indicate the rounding convention to be used
for 1hour ozone data (40 CFR part 58, appendix F). In 1979, EPA issued
additional guidance specific to ozone in which EPA provided that ``the
stated level of the standard is taken as defining the number of
significant figures to be used in comparisons with the standard. For
example, a standard level of 0.12 ppm means that measurements are to be
rounded to two decimal places (.005 rounds up), and, therefore, 0.125
ppm is the lowest concentration value in excess of the level of the
standard.'' See ``Guideline for the Interpretation of Ozone Air Quality
Standards,'' EPA450/479003, at p. 6. EPA's guidance on air quality
modeling is consistent with those Guidelines. See, e.g., Guidance on
Use of Modeled Results to Demonstrate Attainment of the Ozone NAAQS, July 1996.
d. Modeled Demonstration of Attainment.
Comment 1: The commenter alleges that photochemical grid modeling
shows that the Washington area will not attain the ozone standard by
the November 2005 attainment date and because the ``weight of
evidence'' (WOE) analysis used by EPA to conclude that the Washington
area has demonstrated attainment by November 2005 is not authorized by
the Act or by EPA rules. The comments claim that the modeling
demonstration and WOE used in the attainment demonstration for the
Washington area do not meet requirements of section 182(c) of the CAA
and EPA's own regulations for photochemical grid modeling and other
analytical methods, that the WOE is an alternative method to
photochemical grid modeling which has not been shown to be equally
effective to the Urban Airshed Model (UAM), and that WOE is a
proscribed rollback method. Also, the commenter claims the most recent
modeling guidance is flawed because: it is allegedly a rollback
technique; because it allegedly allows the averaging across the three
highest air quality sites across a region, whereas EPA's 1991 and 1996
modeling guidance requires that attainment be demonstrated at each site and, thus,
[[Page 19112]]
effectively lowers the total emission reduction needed to attain at the
highest site; and because of alleged flaws in the techniques for
determining the magnitude of additional emission reductions. The
commenter therefore asserts that approval of the attainment
demonstration would be arbitrary, capricious and contrary to law for
reasons set forth in comments submitted on March 5, 2003, as well as
those previously submitted to EPA on February 14, 2000. Such comments
also included EPA's treatment of overprediction of ozone levels by the
photochemical grid model, EPA's treatment of modeled exceedances over
the standard and EPA's treatment of the photochemical grid modeling
results prediction of exceedances even over the levels allowed after a
downward adjustment under EPA's alternative test. Finally, the
commenter asserts that EPA failed to adequately explain certain
adjustments made to the photochemical grid modeling for the Washington area.
Response 1:
WOE is consistent with the CAA and EPA regulations.
With respect to the allegation that the WOE analysis used by EPA is not authorized by the Act or EPA rules, EPA consistently has interpreted the CAA to allow for a weightofevidence analysis as an interpretive adjunct to the photochemical grid modeling used to show that the Washington area will attain the ozone standard in 2005. See, e.g., 66 FR 634, January 3, 2001; 66 FR 666, January 3, 2001; 66 FR 54143, October 26, 2001; 66 FR 54577, October 29, 2001; 66 FR 54597, October 29, 2001; 66 FR 54666, October 30, 2001; 66 FR 56903, November 13, 2001; 66 FR 56931, November 13, 2001; 66 FR 56944, November 13, 2001; 66 FR 57159, November 14, 2001; 66 FR 63921, December 11, 2001; 67 FR 5151, February 4, 2002; 67 FR 5170, February 4, 2002; 67 FR 30574, May 7, 2002; 67 FR 61786, October 2, 2002; 67 FR 72576, December 6, 2002; and 67 FR 72574, December 6, 2002. Because WOE is an adjunct to photochemical grid modeling, not a separate analysis, the commenter's assertion that the modeling for the Washington area is not consistent with the CAA is a misstatement.
As described in more detail below, the EPA allows states to supplement their photochemical modeling results with additional evidence designed to account for uncertainties in the photochemical modeling databases and application in order to demonstrate attainment. This approach is consistent with the requirement of section 182(c)(2)(A) that the attainment demonstration ``be based on photochemical grid modeling,'' because the modeling results constitute the principal component of EPA's analysis with supplemental information designed to account for uncertainties in the model. This interpretation and application of the photochemical modeling requirement of section 182(c)(2)(A) finds further justification in the broad deference Congress granted EPA to develop appropriate methods for determining attainment, as indicated in the last phrase of section 182(c)(2)(A).
This interpretation of the Act has been upheld by the Court of Appeals for the Fourth Circuit, which stated ``EPA has long recognized that there are uncertainties inherent in available models and in estimating future emissions * * *. EPA thus allows the use of supplemental analysis, including a ``weight of evidence'' analysis, to demonstrate attainment in cases where the modeling shows ozone levels exceeding the NAAQS.'' 1000 Friends of Maryland v. Browner, 265 F.3d 216, 234 (4th Cir. 2001)(internal quotation omitted).
The flexibility granted to EPA under section 182(c)(2)(A) is also
reflected in the regulations EPA promulgated for modeled attainment
demonstrations. These regulations provide, ``The adequacy of a control
strategy shall be demonstrated by means of applicable air quality
models, data bases, and other requirements specified in (40 CFR part
51, appendix W) (Guideline on Air Quality Models).'' \3\ 40 CFR
51.112(a)(1). The regulations further provide, ``Where an air quality
model specified in appendix W * * * is inappropriate, the model may be
modified or another model substituted [with approval by EPA, and after]
notice and opportunity for public comment * * *.'' Appendix W, in turn,
provides that, ``The Urban Airshed Model (UAM) is recommended for
photochemical or reactive pollutant modeling applications involving
entire urban areas,'' but further refers to EPA's modeling guidance for
data requirements and procedures for operating the model. 40 CFR part
51, appendix W, section 6.2.1.a. The modeling guidance discusses the
data requirements and operating procedures, as well as interpretation
of model results as they relate to the attainment demonstration. This
provision references guidance published in 1991; however, EPA
envisioned that the guidance would change as we gained experience with
model applications, which is why the guidance is referenced, but does
not appear, in Appendix W. With updates in 1996 and 1999, the evolution
of EPA's guidance has led us to the use of the photochemical grid
model, as well, or in conjunction, with additional analytical methods approved by EPA.
\3\ The August 12, 1996 version of ``Appendix W ot Part 51
Guideline on Air Quality Models'' was the rule in effect for these
attainment demonstrations. EPA is proposing updates to this rule
which will not be in effect until the new rule is promulgated.
EPA's interpretation of the CAA is consistent with the statute's requirement that the attainment demonstration be ``based on photochemical grid modeling.'' Giving the phrase ``based on'' its ordinary meaning, the statute requires only that an attainment demonstration ``arise from'' photochemical grid modeling, using the modeling as a ``starting point'' or ``foundation.'' See McDaniel v. Chevron Corp., 203 F.3d 1099, 1111 (9th Cir. 2000) (reviewing cases interpreting the phrase ``based on''); United States v. United Technologies. Corp., 985 F.2d 1148, 1158 (2d Cir. 1993) (``based upon'' does not mean ``solely''). EPA's weightofevidence analysis is consistent with the plain meaning of the statute because photochemical grid modeling is the starting point of the analysis; indeed, the very purpose of the WOE analysis is to determine whether the modeling, in light of all the evidence, demonstrates attainment.
Even if the statutory language is ambiguous, EPA's interpretation is reasonable under Chevron U.S.A. Inc. v. Natural Res. Def. Council, 467 U.S. 837, 84245 (1984). The comments apparently are based on the premise that the statute should be read to say an attainment demonstration must be based solely on photochemical grid modeling without reliance on any analytical adjuncts. Even if this were a plausible reading of the statute, EPA's interpretation is equally permissible. See United Technologies, 985 F.2d at 1158. Our interpretation adheres to the normal meaning of the statutory language and is supported by the broad discretion that Congress granted to EPA in section 182(c)(2)(A).
Because EPA reasonably determined that WOE analysis is based on
photochemical grid modeling, there is no merit to the alternative
statutory argument found in the comments. The comments contend that WOE
qualifies as an ``other analytical method'' under section 182(c)(2)(A),
requiring the EPA Administrator to determine that weightofevidence is
``at least as effective'' as photochemical grid modeling. As noted,
however, weightofevidence analysis is ``based on photochemical grid
modeling''; therefore, EPA did not employ an ``other analytical method''
[[Page 19113]]
that would have required an effectiveness determination by the Administrator.\4\
\4\ For the same reasons, EPA was not required to address
whether its 1996 or 1999 Modeling Guidance is a ``substitute'' for modeling or is an adequate model by itself.
Under ``Guidance on the Use Of Modeled Results to Demonstrate Attainment of the Ozone NAAQS,'' EPA454/B95007, June 1996 (hereafter the 1996 Guidance), the modeled attainment test compares model predicted 1hour daily maximum ozone concentrations in all grid cells for the attainment year to the level of the NAAQS. The results may be interpreted through either of two modeled attainment or exceedance tests: A deterministic test or a statistical test. Under the deterministic test, a predicted concentration above 0.124 parts per million (ppm) ozone indicates that the area is expected to exceed the standard in the attainment year and a prediction at or below 0.124 ppm indicates that the area is expected to not exceed the standard. Under the statistical test, attainment is demonstrated when all predicted (i.e., modeled) 1hour ozone concentrations inside the modeling domain are at, or below, an acceptable upper limit above the NAAQS permitted under certain conditions (depending on the severity of the episode modeled).
Based upon our experience with application of the models, which we did not have in 1991, EPA issued the 1996 Guidance to update the 1991 guidance referenced in 40 CFR part 50, appendix W, to make the modeled attainment test more closely reflect the form of the NAAQS (i.e., the statistical test described above), and the meteorological conditions accompanying observed exceedances. The 1996 Guidance also allows for consideration of additional evidence to address uncertainties in the modeling databases and application. Therefore, when modeling does not conclusively demonstrate attainment, EPA has concluded that additional analyses may be presented to help determine whether the area will attain the standard. As with other predictive tools, there are inherent uncertainties associated with air quality modeling and its results. The inherent imprecision of the model means that it may be inappropriate to view the specific numerical result of the model as the only determinant of whether the SIP controls are likely to lead to attainment.
EPA's 1996 Guidance recognizes these limitations, and provides a means for considering other evidence to help assess whether attainment of the NAAQS is likely to be achieved. The process by which this is done is called a weightofevidence or WOE determination. Under a WOE determination, the state can rely on, and EPA will consider factors such as other modeled output (e.g., changes in the predicted frequency and pervasiveness of 1hour ozone NAAQS exceedances); actual observed air quality trends (i.e., analyses of monitored air quality data); estimated emissions trends; and the responsiveness of the model predictions to further controls in addition to the results of the modeled attainment test.
In 1999, EPA issued additional guidance (hereafter, the 1999
Guidance)\5\ that makes further use of model results for base case and
future emission estimates to predict a future design value. This
guidance describes the use of an additional component of the WOE
determination, which requires, under certain circumstances, additional
emission reductions that are or will be approved into the SIP, but that
were not included in the modeling analysis, that will further reduce
the modeled design value. An area is considered to monitor attainment
if each monitor site has air quality observed ozone design values (4th
highest daily maximum ozone using the three most recent consecutive
years of data) at or below the level of the standard (which is 124
ppb). Therefore, it is appropriate for EPA, when making a determination
that a control strategy will provide for attainment, to determine
whether or not the model predicted future design value is expected to be at or below the level of the standard.
\5\ ``Guidance for Improving Weight of Evidence Through
Identification of Additional Emission Reductions, Not Modeled.''
U.S. Environmental Protection Agency, Office of Air Quality Planning
and Standards, Emissions, Monitoring, and Analysis Division, Air Quality Modeling Group, Research Triangle Park, NC 27711.
Since the form of the 1hour ozone NAAQS allows exceedances, it did
not seem appropriate for EPA to require the test for attainment to be
``no exceedances'' in the future model predictions. The method outlined
in the 1999 Guidance uses the highest measured design value from all
sites in the nonattainment area for each of three years. The three year
``design value'' represents the air quality observed during the time
period used to predict ozone for the base emissions. This is
appropriate because the model is predicting the change in ozone from
the base period to the future attainment date. The ``design value''
calculation accounts for the fact that the NAAQS allows limited
exceedances of the ozone standard without a resulting violation. The
three yearly design values (highest across the area) are averaged to
account for annual fluctuations in meteorology.\6\ The result is an
estimate of an area's base year design value. The base year design
value is multiplied by a ratio of the peak model predicted ozone
concentrations in the attainment year (i.e., average of daily maximum
concentrations from all days modeled) to the peak model predicted ozone
concentrations in the base year (i.e., average of daily maximum
concentrations from all days modeled). The result is an attainment year
design value based on the relative change in peak model predicted ozone concentrations from the base year to the attainment year.
\6\ The commenter criticized the 1999 Guidance because it
allegedly allows the averaging across the three highest air quality
sites across a region, whereas EPA's earlier (1991 and 1996)
modeling guidance requires that attainment be demonstrated at each
site and, thus, effectively lowers the total emission reductions
needed to attain at the highest site. The commenter's concern is
misplaced. The 1999 Guidance uses averaging of the worst modeled air
quality value across episode days or worst design value across a
three year period. Also, the WOE determination, in turn, is intended
to be a qualitative assessment of whether additional factors
(including the additional emissions reductions not modeled), taken
as a whole, indicate that the area is more likely than not to attain.
The use of this analytical adjunct, however, does not mean that a state's attainment demonstration is ``based on'' something other than photochemical grid modeling, or that WOE is ``less effective'' than photochemical grid modeling. To the contrary, WOE analysis is used to assess the photochemical grid modeling results; it supplements, but does not replace, the modeling. See 1996 Guidance at S1 (``In a weight of evidence determination, model results are weighed heavily''). It follows that the WOE approach is consistent with the CAA requirement that the attainment demonstration ``be based on photochemical grid modeling,'' because WOE is merely an adjunct for assessing the photochemical grid modeling. In the case of the Washington area demonstration, photochemical grid modeling is the primary basis for the attainment demonstration. See 1996 Guidance at S1.
The 1999 Guidance is reasonable and is not a proportional rollback.
As stated previously, episodic photochemical grid modeling is the
primary basis for the attainment demonstration, as it was used to
define the majority of the control strategy. However, the modeling and
corroborative analyses, which form the basis of the weight of evidence analysis, provide a preponderance of evidence to
[[Page 19114]]
support EPA's determination that attainment of the 1hour ozone NAAQS
will be achieved in 2005. One of these WOE analyses involved the use of
a relative reduction factor (derived from the local model results) to
determine if any additional NO
In contrast to the claims in the adverse comments, EPA did not rely
on ``proportional'' rollback as defined in section 14.0 of 40 CFR part
51, appendix W which defines ``rollback'' as ``a simple model that
assumes that if emissions from each source affecting a given receptor are decreased by the same percentage, ambient air quality
concentrations decrease proportionately.'' The prohibition regarding
proportional modeling in section 6.2.1.e of appendix W (i.e.,
``Proportional (rollback/forward) modeling is not an acceptable
procedure for evaluating ozone control strategies'') applies to the use
of a rollback method which is empirically/mathematically derived and
independent of model estimates or observed air quality and emissions
changes as the sole method for evaluating control strategies. A true
proportional rollback model does not rely on any photochemical grid
modeling, and it assumes, for example, that a 20 percent decrease in
NO
Other comments on the 1999 Guidance are not germane to the Washington area.
The comments alleged flaws in the two techniques for determining the magnitude of additional emission reductions. With respect to comments on these two techniques for determining the magnitude of additional emission reductions contained in the 1999 Guidance, EPA believes these comments do not apply in the case of EPA's analysis of the attainment demonstration for the Washington area.
The first allegation is that these techniques allow averaging the three highest design values across a nonattainment area whereas EPA's modeling guidance requires that attainment be demonstrated at each site. The alleged effect of this averaging technique is that lower air quality concentrations are averaged against higher concentrations thus reducing the total emission reduction needed to attain at the highest site.
The second allegation concerns the assumption that the contribution
of VOC versus NO
The 1999 Guidance provided a twostep method for evaluating the air quality modeling results. The first step is an assessment of whether attainment is demonstrated by a showing that a future year design value will be 0.124 ppm or less. In the event that the predicted attainment year design value is above the standard, the second step of the 1999 Guidance provides two techniques for identifying additional emission reductions, that were not modeled, and which at a minimum provide an estimated attainment year design value at the level of the standard. The first technique is the use of a ``relative reduction factor (RRF)'' analysis to estimate a future design value.\7\ We used this analytical method to demonstrate that the Washington area will attain the standard. Attainment can be demonstrated by showing that the future year design value will be 0.124 ppm or less. Modeling predicts the peak ozone values in the attainment year, but it cannot predict the future design value for that year due to the limited number of days that can reasonably be modeled. The RRF analysis, however, provides an estimate of future design value based on the principle that a control strategy that reduces ozone peaks will similarly reduce design values. The RRF analysis has two steps. First, the state derives the RRF from the modeled reduction in ozone peaks between the base year and the attainment year. Second, the state applies the RRF to the design value for the base year to estimate the future design value in the attainment year. EPA has concluded that for the Washington area the RRF analysis demonstrates a future year design value of 119.6 ppb which is less than 124 ppb. Using the 1999 Guidance, EPA never needed to go beyond the RRF technique to determine that the Washington area will attain the ozone standard. Therefore, the other comments regarding the techniques for determining the magnitude of such additional reductions are not germane to this rulemaking and are not addressed in this document.
\7\ 1999 Guidance at 34.
EPA's treatment of overprediction of ozone levels, of modeled exceedances and downward adjustment of results.
As another element of EPA's WOE analysis, we evaluated the
photochemical grid modeling for the Washington area. We analyzed the
severity of the episodes modeled for the Washington area and have
concluded that these would be adequate for determining the emission
reductions needed for attainment in the Washington area. When the
emission inventory with the control strategy is modeled, peak ozone
concentration is reduced by approximately 22 ppb from the modeled peak
concentrations in the 1991 base cases. When the average modeled peak
ozone reduction from the base year modeling to the attainment year
modeling (22 ppb) is subtracted from the peak measured concentration
for July 16 (137 ppb) and July 19 (132 ppb), the resulting
concentrations are 115 ppb and 110 ppb respectively. However, when the
modeled ozone reduction is applied to the peak monitored level on July
20 (178 ppb), the resulting concentration is 156 ppb. When the day
specific reduction of peak modeled ozone concentration from the base
year modeling to the attainment year modeling is subtracted from the
peak measured concentrations on July 16th, July 19th, and July 20th,
the result is 120 ppb, 103 ppb, and 158 ppb respectively. Both methods
(average, dayspecific) resulted in two of the three days showing
values below the ozone standard indicating attainment for these days.
However, both methods resulted in values above the standard for July 20th.\8\
\8\ The details of this analysis and the method and calculation
details by which EPA determined how much the model overpredicts
monitored ozone concentrations is explained in ``First Amendment to
Technical Support Document for Approval and Promulgation of Air
Quality Implementation Plans; District of Columbia, Maryland, and
Virginia; Post1996 RateofProgress Plan for the Metropolitan Washington, DC Nonattainment Area'' dated April 10, 2003.
EPA has evaluated the ozone formation potential of the July 20,
1991, episode day and determined that it is 13th most severe day out of
approximately the last 50 years with an average reoccurrence of once
every 45 years; this type of day is not likely to occur often enough
to be a major causative factor for nonattainment because the standard
allows up to three monitored exceedances in any three year period. Because modeling for the Washington area showed some peak
concentrations above 124 ppb, EPA conducted the RRF analysis which is [[Page 19115]]
discussed in prior paragraphs of this section to determine what
additional emission reductions may be needed to support ozone
attainment in the Washington area using EPA's 1999 Guidance. As stated
in previous paragraphs of this section, EPA has concluded that the
Washington area does not need any additional emission reductions beyond
those contained the attainment demonstration for the Washington area to ensure attainment of the ozone NAAQS.
While the modeling results suggest that exceedances may still occur, EPA's 1996 Guidance allows for consideration in the weightof evidence analysis of whether the model overpredicts or underpredicts in the base case and consideration of other evidence.
The base case model performance for both of the July 1991 episodes show good alignment of the modeled ozone plume in comparison to monitored ozone values (e.g., the model predicted peak concentrations and monitored peak concentrations are generally paired in space). Therefore, the degree to which the peak predicted values exceed the measured values in the same general vicinity, indicates that the model is systematically overpredicting ozone concentration, while adequately representing the spacial distribution of ozone.
With respect to the assertion that EPA did not explain how adjusting model results to account for model over prediction is consistent with EPA's modeling rule, 40 CFR part 51, appendix W, the modeling rule encourages the assessment of model uncertainty as one of the factors affecting the model results. In EPA's view, model over prediction is only a rough approximation of the extent of modeling uncertainty. Consideration of model performance (specifically, a bias to under or overpredict ozone levels) is one way to assess modeling uncertainty. For the Washington area, EPA explained how performance was more closely reviewed and used as part of the WOE determination.
As a further part of the WOE analysis to corroborate the likelihood that the Washington area will attain the 1hour ozone standard by the attainment date of 2005, EPA developed relative redu
FOR FURTHER INFORMATION CONTACT Christopher Cripps, (215) 814-2179, or by email at cripps.christopher.@epa.gov.
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