Illinois Administrative Code › Title 35 - ENVIRONMENTAL PROTECTION › Part 352 - PROCEDURES FOR DETERMINING WATER QUALITY BASED PERMIT LIMITATIONS FOR NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM DISCHARGERS TO THE LAKE MICHIGAN BASIN › Subpart D - ASSESSMENT OF REASONABLE POTENTIAL TO EXCEED WATER QUALITY STANDARDS, CRITERIA, AND VALUES › Section 352.421 - Estimation of Projected Effluent Quality

Current through Register Vol. 48, No. 28, July 12, 2024
a) The first step in determining if a
				reasonable potential to exceed the water quality standard exists for any
				particular pollutant parameter is the estimation of the maximum expected
				effluent concentration for that substance. That estimation will be completed
				for both acute and chronic exposure periods and is termed the PEQ. The PEQ
				shall be derived from representative facility specific data to reflect a 95
				percent confidence level for the 95th percentile value. These data will be
				presumed to adhere to a lognormal distribution pattern unless the actual
				effluent data demonstrates a different distribution pattern. If facility
				specific data in excess of 10 data values is available, a coefficient of
				variation that is the ratio of the standard deviation to the arithmetic average
				shall be calculated by the Agency. The PEQ is derived as the upper bound of a
				95 percent confidence bracket around the 95th percentile value through a
				multiplier from the following table applied to the maximum value in the data
				set that has its quality assured consistent with Section
				352.410 as
				appropriate for acute and chronic data sets.
PEQ = (maximum data point)(statistical multiplier)
Coefficient of
							 Variation
No. Samples
0.1
0.2
0.3
0.4
0.5
0.6
0.7
1
1.4
1.9
2.6
3.6
4.7
6.2
8.0
2
1.3
1.6
2.0
2.5
3.1
3.8
4.6
3
1.2
1.5
1.8
2.1
2.5
3.0
3.5
4
1.2
1.4
1.7
1.9
2.2
2.6
2.9
5
1.2
1.4
1.6
1.8
2.1
2.3
2.6
6
1.1
1.3
1.5
1.7
1.9
2.1
2.4
7
1.1
1.3
1.4
1.6
1.8
2.0
2.2
8
1.1
1.3
1.4
1.6
1.7
1.9
2.1
9
1.1
1.2
1.4
1.5
1.7
1.8
2.0
10
1.1
1.2
1.3
1.5
1.6
1.7
1.9
11
1.1
1.2
1.3
1.4
1.6
1.7
1.8
12
1.1
1.2
1.3
1.4
1.5
1.6
1.7
13
1.1
1.2
1.3
1.4
1.5
1.6
1.7
14
1.1
1.2
1.3
1.4
1.4
1.5
1.6
15
1.1
1.2
1.2
1.3
1.4
1.5
1.6
16
1.1
1.1
1.2
1.3
1.4
1.5
1.6
17
1.1
1.1
1.2
1.3
1.4
1.4
1.5
18
1.1
1.1
1.2
1.3
1.3
1.4
1.5
19
1.1
1.1
1.2
1.3
1.3
1.4
1.5
20
1.1
1.1
1.2
1.2
1.3
1.4
1.4
30
1.0
1.1
1.1
1.1
1.2
1.2
1.2
40
1.0
1.0
1.1
1.1
1.1
1.1
1.1
50
1.0
1.0
1.0
1.0
1.0
1.0
1.0
60 or greater
1.0
1.0
1.0
1.0
1.0
1.0
1.0
Coefficient of
							 Variation
0.8
0.9
1.0
1.1
1.2
1.3
10.1
12.6
15.5
18.7
22.3
26.4
5.4
6.4
7.4
8.5
9.7
10.9
4.0
4.6
5.2
5.8
6.5
7.2
3.3
3.7
4.2
4.6
5.0
5.5
2.9
3.2
3.6
3.9
4.2
4.5
2.6
2.9
3.1
3.4
3.7
3.9
2.4
2.6
2.8
3.1
3.3
3.5
2.3
2.4
2.6
2.8
3.0
3.2
2.1
2.3
2.4
2.6
2.8
2.9
2.0
2.2
2.3
2.4
2.6
2.7
1.9
2.1
2.2
2.3
2.4
2.5
1.9
2.0
2.1
2.2
2.3
2.4
1.8
1.9
2.0
2.1
2.2
2.3
1.7
1.8
1.9
2.0
2.1
2.2
1.7
1.8
1.8
1.9
2.0
2.1
1.6
1.7
1.8
1.9
1.9
2.0
1.6
1.7
1.7
1.8
1.9
1.9
1.6
1.6
1.7
1.7
1.8
1.9
1.5
1.6
1.6
1.7
1.8
1.8
1.5
1.5
1.6
1.6
1.7
1.7
1.3
1.3
1.3
1.3
1.4
1.4
1.1
1.2
1.2
1.2
1.2
1.2
1.1
1.1
1.1
1.1
1.1
1.1
1.0
1.0
1.0
1.0
1.0
1.0
1) If the PEQ
				is less than or equal to the water quality standard, there is no reasonable
				potential and no limit will be established in the permit.
2) If the PEQ is more than the water quality
				standard, the Agency will proceed to consideration of dilution and mixing
				pursuant to Section
				352.422.