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      Environmental Protection                                                EPA420-B-03-010
      A9encv                                                              October 2003
               Boundary Scenarios for 8-hour Ozone Nonattainment Areas
                Previously Designated as Nonattainment or Maintenance
                            for the 1-hour Ozone Standard

                         Reference Document for Commenters
Note: The purpose of this reference document is to assist the public in understanding Section
VI.A.2. of EPA's proposal entitled, "Transportation Conformity Rule Amendments for the New
8-hour Ozone and PM2.5 National Ambient Air Quality Standards and Miscellaneous Revisions
for Existing Areas." The transportation conformity proposal was signed on October 22, 2003.
Section VI. of the proposal is entitled, "Regional Conformity Tests in 8-hour Ozone Areas That
Have 1-hour Ozone SIPs."

The hypothetical boundary scenarios described in Section VI. are for 8-hour ozone
nonattainment areas that were also designated nonattainment under the 1-hour ozone air quality
standard. These boundary scenarios are important for applying the proposed conformity test
options in these areas.  The proposed test options would apply for such areas before 8-hour
ozone SIPs and motor vehicle emissions budgets are available for conformity purposes.
SCENARIO 1: 8-hour and 1-hour Ozone Boundaries Are Exactly the Same

In this scenario, the 8-hour and 1-hour ozone boundaries cover exactly the same geographical
area.
SCENARIO 2: 8-hour Ozone Boundary Is Smaller Than and Within the 1-hour Ozone
Boundary

In this scenario, the 8-hour ozone nonattainment area is smaller than and completely
encompassed by the 1-hour ozone boundary.

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SCENARIO 3: 8-hour Ozone Boundary Is Larger Than the 1-hour Ozone Boundary

In this scenario, the entire 1-hour ozone boundary is within a larger 8-hour ozone nonattainment
area.
SCENARIO 4: 8-hour Ozone Boundary Overlaps With the 1-hour Ozone Boundary

In this scenario, the 8-hour and 1-hour ozone boundaries partially overlap.

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