Michigan Administrative Code › Department - Environmental Quality › Water Resources Division › Water Resources Protection › Part 8 - WATER QUALITY-BASED EFFLUENT LIMIT DEVELOPMENT FOR TOXIC SUBSTANCES › Section R. 323.1211 - Reasonable potential for chemical-specific water quality-based effluent limits (WQBELs)

Current through Vol. 24-12, July 15, 2024
Rule 1211
.
(1) Chemical-specific water quality-based
				  effluent limits (WQBELs) shall be incorporated into a national pollutant
				  discharge elimination system (NPDES) permit where the department determines
				  that a toxic substance is or may be discharged into the waters of the state at
				  a level that has the reasonable potential to cause or contribute to an
				  excursion above any water quality value. The determination shall be made by
				  developing preliminary effluent limitations (PELs) and comparing the effluent
				  limitations to the potential effluent quality (PEQ) of the discharge.
(2) PELs shall be developed for each toxic
				  substance that the permittee reports as known or believed to be present in its
				  discharge using the wasteload allocation (WLA) provisions specified in R
				  323.1207 or R 323.1209. At a minimum, PELs are required and shall be developed
				  for the protection of aquatic life and noncancer human health effects where
				  aquatic life values, human noncancer values, or the minimum data to calculate
				  the aquatic life or human noncancer values are available. If there are
				  insufficient data to calculate aquatic life or human noncancer values, then the
				  department shall follow the provisions in subrule (6) of this rule. PELs shall
				  also be developed for the protection of wildlife and human health cancer
				  effects where human cancer values, wildlife values, or the minimum data to
				  calculate human cancer or wildlife values are available.
(3) The PEQs shall be determined by either of
				  the following procedures:
(a) If 10 or more
				  representative facility-specific effluent samples are available that are
				  greater than the detection limit, then the maximum PEQ shall equal the upper
				  ninetififth percentile of all the representative daily discharge concentrations
				  and the average PEQ shall equal the upper ninetififth percentile of all the
				  representative 30-day average discharge concentrations. The upper ninetififth
				  percentile of the daily discharge concentrations and 30-day average discharge
				  concentrations shall be calculated as follows:
P95 = exp (mudn + Zp sigmadn)
Where: P95 = upper ninetififth percentile of n-day average
					 discharge concentrations.
d = ratio of the number of daily discharge concentrations
					 less than the limit of detection to the total number of discharge
					 concentrations.
n = number of discharge concentrations used to calculate an
					 average over a specified monitoring period (n=1 for daily concentrations and 30
					 for 30- day averages).
exp = base e (or approximately 2.718) raised to the power
					 shown between the parentheses in the P95 equation.
Zp = Z value corresponding to the upper
					 pth percentile of the standard normal
					 distribution.
p =
					 (0.95-dn)/(1-dn).
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ln = natural logarithm.
m = mean of discharge concentrations greater than the limit
					 of detection.
s = standard deviation of discharge concentrations greater
					 than the limit of detection.
Reasonable potential for the discharge of a toxic
					 substance to cause or contribute to an excursion above any water quality value
					 will be considered to exist if the average or maximum PEQ exceeds any of the
					 chronic or acute PELs, respectively, developed in accordance with subrule (2)
					 of this rule.
(b) If
				  sufficient data are not available to use the process described in subdivision
				  (a) of this subrule, then the PEQ shall be determined by identifying the total
				  number of representative effluent samples, both detectable and nondetectable,
				  and multiplying the maximum effluent concentration by the appropriate factor
				  from table  4 developed by assuming a 0.6
				  coefficient of variation. Reasonable potential for the discharge of a toxic
				  substance to cause or contribute to an excursion above any water quality value
				  will be considered to exist if the PEQ exceeds any of the PELs developed in
				  accordance with subrule (2) of this rule. For purposes of this subdivision, the
				  department shall consider other scientifically defensible approaches on a
				  case-by-case basis which are consistent with procedure 5.B.2 of Appendix F, 40
				  C.F.R. Part 132 (1995), which is adopted by reference in R 323.1221, for use in
				  determining reasonable potential. If requested by the permittee, one such
				  approach that is acceptable to the department is the prediction level concept
				  specified in Gibbons, 1994, Statistical Methods for Groundwater Monitoring -
				  Wiley, New York where representative effluent data appropriate for use with
				  this method is provided. If the prediction level approach is proposed for use
				  with data sets containing values both above and below the detection level, then
				  a process to address the less than detection values, that is acceptable to the
				  department, shall be provided by the permittee.
Table 4. Reasonable potential multiplying factors: 95%
					 confidence level and 95% probability basis.
Number of Samples
1
2
3
4
5
6
7
8
9
Multiplying Factor
6.2
3.8
3.0
2.6
2.3
2.1
2.0
1.9
1.8
10
11
12
13
14
15
16
17
18
19
1.7
1.7
1.6
1.6
1.5
1.5
1.5
1.4
1.4
1.4
20
30
40
50
60
70
80
90
100
1.4
1.2
1.1
1.0
1.0
0.9
0.9
0.9
0.9