Step 5. Sum the quarterly components to get quarterly “potential” 98th percentile PM2.5


Sum the quarterly components to get quarterly “potential” 98th percentile PM2.5 values. Repeat

this procedure for each quarter and for each of the 5 years of ambient data. The highest daily

value (from the 4 quarterly values) for each year at each monitor is considered to be the

estimated 98th percentile value for that year.

Step 6. Calculate future year 5 year weighted average 24-hour design values and compare

to the NAAQS.

The estimated 98th percentile values for each of the 5 years are averaged over 3 year intervals

to create design values and then the 3 design values are averaged to create the 5 year weighted

average for each monitor. Compare the projected 24-hour design values to 65 ug/m3.

The recommended test is illustrated in example 5.2. In the interest of brevity, some of the steps

are only illustrated for quarter 1. The actual calculations would also use analogous data for the

other three quarters.

Example 5.2

Given: (1) Area “D” has 1 monitoring site. The 98th percentile values for 5 years of observed

data are as follows (year 3 is being modeled for the attainment test):

Year 1- 80 ug/m3

Year 2- 68 ug/m3

Year 3- 71 ug/m3

Year 4- 58 ug/m3

Year 5- 74 ug/m3

Step 1- Compute observed 98th percentile values for each year and next highest

concentrations for each quarter.

The maximum quarterly values from the 5 years which are equal to or less than the 98th

percentile concentration are as follows:



n651 - n652 - n653 - n654 - n655 - n656 - n657 - n658 - n659 - n660 - n661 - n662 - n663 - n664 - n665 - n666 - n667 - n668 - n669 - n670 - n671 - n672 - n673 - n674 - n675 - n676 - n677 - n678 - n679 - n680 - n681 - n682 - n683 - n684 - n685 - n686 - n687 - n688 - n689 - n690 - n691 - n692 - n693 - n694 - n695 - n696 - n697 - n698 - n699 - n700


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