(DVF)I = the estimated future design value for the time attainment is required, ppb or ug/m3.

Equation (3.1) looks simple enough. However, several issues must be resolved before

applying it.

(1) How is a “site-specific” baseline design value ((DVB)I) calculated?

(2) In calculating the (RRF)I , what do we mean by “near” site I?

(3) Several surface grid cells may be “near” the monitor, which one(s) of these should be used to

calculate the (RRF)I ?

(4) How do you calculate future design values in unmonitored areas?

(5) Which base year emissions inventory should be projected to the future for the purpose of

calculating RRFs?

(6) Which future year should emissions be projected to in order to assess attainment using the

modeled attainment test?

3.1 Calculating site-specific baseline concentrations.

The modeled attainment test is linked to the form of the ozone and PM2.5 NAAQS

through the use of monitored design values. Official design values are calculated in different

ways for 8-hour ozone, annual average PM2.5, and 24-hour average PM2.5. The following is a

brief description of the calculations:


The 8-hour ozone design value is calculated as the 3 year average of the fourth highest

monitored daily 8-hour maximum value at each monitoring site. The standard is met if the

design value is <0.8 ppm (in practice, this translates to < 85 ppb). The detailed description of the

methodology can be found in 40 CFR Part 50.10, and Appendix I to Part 50.

Annual Average PM2.5

The annual average PM2.5 standard is met if, over a consecutive three year period, the average

arithmetic mean concentration of PM2.5 is less than or equal to 15.0 :g/m3. The annual

arithmetic mean at a monitoring site is calculated by averaging the four quarterly arithmetic

mean concentrations observed during a calendar year at the site. The annual mean concentration

averaged over three years must be < 15.0 :g/m3 at all monitoring sites. The details can be found



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