selected for modeling. If corroboratory analyses produce strong evidence that a control strategy

is unlikely to meet the NAAQS, then the strategy may be inadequate, even if the modeled

attainment test is passed.

5. Focusing the modeled attainment test only at monitoring sites could result in control

targets which are too low if the monitoring network is limited or poorly designed. We

recommend a test which includes a review of the strategy’s impact at locations without monitors.

This exercise provides a supplemental test to determine whether there is a need for further action

despite passing the modeled attainment test at all monitoring sites. While this test may indicate

potential unmonitored violations, ultimately, the best way to account for a limited or poorly

designed monitoring network is to use the model results, or other available analyses, to help

determine locations where additional monitors should be sited.

3.0 What Is The Recommended Modeled Attainment Test?

In Section 2, we provided an overview of the recommended modeled attainment test. In

this section we provide more details on the calculation of baseline design values, the definition

of “nearby grid cells”, and an “unmonitored area analysis” which provides estimates of future

year values in unmonitored areas. Sections 4, 5, and 6 provide more specific details and

examples for attainment tests for ozone and PM2.5, and the uniform rate of progress assessment

for regional haze respectively.

We begin by establishing the basic equation on which all of the tests are built upon.

Equation (3.1) describes the recommended modeled attainment test, applied near monitoring site


(DVF)I = (RRF)I (DVB)I (3.1)


(DVB)I = the baseline concentration monitored at site I, units in ppb or ug/m313;

(RRF)I = the relative response factor, calculated near site I, unitless

The relative response factor is the ratio of the future concentration predicted near a

monitor (averaged over multiple days) to the baseline concentration predicted near

the monitor (averaged over the same days), and

(DVF)I = the estimated future design value for the time attainment


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