(7) Subtract the result in (6) from the primary PM2.5 identified in (3)

(8) For each of the 5 years used to calculate the 5 year weighted average design value, subtract

the result from (7) from each quarter for each year. The “new” annual 98th percentile value is the

highest quarterly concentration in each year.

(9) Average the annual 98th percentile concentrations to get 3 design values and then average the

3 DV to get the final future year 5 year weighted average DV.

Annual NAAQS Example:

For quarter 4, a monitor has a 5 year weighted mean concentration of 17.0 ug/m3.

(1) It is believed that several steel mills in the area are contributing to the local

component of PM2.5 at the monitor

(2) Based on comparisons to other monitors in the area, it is believed that the local PM2.5

component at the monitor for quarter 4 is 2 ug/m3.

(3) Using receptor modeling, it is determined that, on average, the steel mills are contributing a

local PM2.5 component in quarter 4 of approximately 1 ug/m3.

(4) Modeling with a dispersion model shows the following contribution at the monitor from the

identified local sources (steel mills):

Base: 2.0 ug/m3

Future: 1.5 ug/m3

(5) Quarter 4 RRF_local = 1.5/2.0 = 0.750.

(6) 1 ug/m3 * 0.750 = 0.75 ug/m3.

(7) 0.75 ug/m3 - 1 ug/m3 = -0.25 ug/m3 (total Q4 reduction from identified local sources is 0.25

ug/m3)

(8) Quarter 4 New DV = 17.0 – 0.25 ug/m3 = 16.75 ug/m3

(9) Steps 1-8 are repeated for each quarter with similar results. The annual DV = (Q1 New DV +

Q2 New DV + Q3 New DV + Q4 New DV)/4

24 Hour NAAQS Example:

The baseline design values are calculated from the 5 year base period centered around the

modeling year.

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