INTRODUCTION

In this paper, we identify several methods for reviewing whether a State is on track

toward attaining the 1-hour national ambient air quality standard (NAAQS) for ozone within

prescribed time limits. These methods may be used during a mid-course review (MCR). In

the event that a required attainment date occurs too soon to permit a mid-course review,

these methods may also be used to perform an early attainment assessment submitted by the

end of the attainment year. Given the fact that attainment determinations are based on three

years of data, the early attainment assessment is especially important for areas in which,

during the two years prior to the attainment year, the areas have registered violations or

continue to observe exceedances. An early assessment will help determine why the air

quality has not improved as expected and provide an early opportunity to develop additional

emission reductions.

1.0 How Do I Determine If A SIP Is On Track Toward Attainment?

First we recommend an administrative review to determine whether the scheduled number

of measures called for in the SIP have been implemented. Then we recommend data analyses

to determine if it is likely that the State implementation plan (SIP) is on track toward

attainment. We recommend that analyses be performed to address several issues which need

to be understood to make a reliable judgment about whether a SIP is on track. Information

resulting from these analyses may be used in a weight of evidence determination to see if the

preponderance of evidence suggests attainment will occur within prescribed time limits.

Analysis to support the MCR should make use of the most up-to-date guidance (e.g., EPA

1996 modeling guidance), analytical techniques, and models such as MOBILE6, BEIS3 and/or

NONROAD. In many cases this will require an assessment of the impact changing from one

analytical technique or model to another will have on the original SIP analysis results.

1.1 Perform Administrative Review

A State should document whether it has implemented the measures planned prior to the

date of the mid-course review. This determination will need to be confirmed by the

appropriate U.S. EPA Regional Office(s). A State also should show whether

administrative/legal prerequisites are in place to implement previously agreed to measures

prior to the required attainment date.

If a State’s implementation plan relies on regional control measures, for a MCR to be

productive, a substantial portion of these need to have been implemented prior to the most

recent ozone season in the nonattainment area for which the mid-course review is being

performed. For example, if NOx SIP call measures are implemented by Spring, 2004, and this

constitutes an important part of the strategy for meeting the NAAQS in a particular

nonattainment area, the mid-course review should include data from the Summer 2004.

2

Further to facilitate a productive review, a substantial portion of a State’s local control

measures needs to have been put in place prior to the most recent ozone season preceding the

mid-course review. Unless substantial progress has been made implementing local and

(where necessary) regional measures, it is unlikely that the signal resulting from

implementation of a SIP will be sufficiently strong to permit a meaningful mid-course analysis.

1.2 Analyze Available Air Quality, Meteorological, Emissions And Modeling Data

These analyses should address several key issues to help judge whether a SIP is on track

toward attainment.

 

 

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