Mich. Admin. Code R. 323.1211 - Reasonable potential for chemical-specific water quality-based effluent limits (WQBELs)

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 p^th 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 3 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

(4) If the analysis in subrule (3) of this rule demonstrates that the toxic substance concentration has a reasonable potential to cause or contribute to an excursion above any water quality value, then a WQBEL or WQBELs shall be established in the permit. For the purpose of an NPDES permit, a chronic or acute WLA based on a water quality value shall be equal to a WQBEL and shall be expressed using the following permit averaging periods:

(a) Chronic WLAs for the protection of aquatic life, human health, and wildlife shall be expressed as monthly average WQBELs.

(b) Acute WLAs for the protection of aquatic life shall be expressed as daily maximum WQBELs.

Monitoring frequency to evaluate compliance with WQBELs shall be established by the department on a case-by-case basis.

(5) Monthly average WQBELs shall be expressed as both a concentration value and a corresponding mass load. The mass and concentration limits shall be calculated using the same facility design flows. Appropriate adjustments may be made to address facilities that receive wet-weather flows. Daily maximum WQBELs shall be expressed as both a concentration value and a corresponding mass load for those substances identified in R 323.1205(u)(ii) and other toxic su b stances a s appropriate.

(6) For each toxic substance which a permittee reports as known or believed to be present in its discharge, and for which data sufficient to calculate tier II values for noncancer human health and aquatic life do not exist, all of the following provisions apply:

(a) The department shall use all available, relevant toxicity information to estimate ambient screening values for the toxic substance that will protect humans from noncancer health effects and aquatic life from acute and chronic effects.

(b) Using the provisions specified in R 323.1209, the department shall develop PELs based on the estimated ambient screening value and compare the PELs with the PEQ. If the PEQ exceeds any of the PELs, then the department shall generate, or require the permittee to generate, the minimum data necessary to derive tier II values for noncancer human health and aquatic life.

(c) The data generated in accordance with subdivision (b) of this subrule shall be used to calculate water quality values. The values shall be used in calculating the PELs pursuant to subrule (2) of this rule for the purpose of determining whether a WQBEL must be included in the permit. If the department finds that the PEQ exceeds the PEL, then a WQBEL for the toxic substance shall be established in the permit consistent with R 323.1211.

(7) All of the following conditions apply when considering intake toxic substances in establishing limitations in NPDES permits:

(a) The department may determine that there is no reasonable potential for the discharge of an identified intake toxic substance to cause or contribute to an excursion above any water quality value if a discharger demonstrates, to the satisfaction of the department, or the department determines, all of the following:

(i) The facility withdraws 100% of the intake water containing the toxic substance from the same body of water into which the discharge is made.

(ii) The facility does not contribute a measurable increased mass of the identified intake toxic substance to its wastewater.

(iii) The facility does not alter the identified intake toxic substance chemically or physically in a manner that would cause adverse water quality impacts to occur that would not occur if the toxic substances were left in- stream.

(iv) The facility does not increase the identified intake toxic substance concentration, as defined by the department, at the edge of the mixing zone or if a mixing zone is not allowed at the point of discharge, as compared to the toxic substance concentration in the intake water, unless the increased concentration does not cause or contribute to an excursion above an applicable water quality standard.

(v) The timing and location of the discharge would not cause adverse water quality impacts to occur that would not occur if the identified intake toxic substance were left in-stream.

(b) If there is a finding under subdivision (a) of this subrule that a toxic substance in the discharge does not have the reasonable potential to cause or contribute to an excursion above a water quality value, then a WQBEL is unnecessary and the permit may require monitoring necessary to demonstrate that the conditions in subdivision (a) of this subrule are maintained during the permit term. Unique situations for commingled waste streams at facilities will be addressed on a case-by-case basis.

(c) Absent a finding under subdivision (a) of this subrule, the department shall use the procedures described in subrules (2) through (5) of this rule to determine whether a discharge has the reasonable potential to cause or contribute to an excursion above any water quality value.

(d) If the background receiving water concentration of the intake toxic substance of concern exceeds the most stringent applicable water quality value for that toxic substance, then all of the following provisions apply:

(i) If the facility meets the conditions in subdivision (a)(i) and (iii) to (v) of this subrule, then a no net addition limit may be established for the toxic substance of concern at a mass and concentration that are no greater than the mass and concentration of the toxic substance identified in the facilitys intake water. In determining whether there has been an addition, recognized statistical concepts shall be considered. For toxic substances contained in the intake water provided by a water system, the concentration of the intake toxic substance shall be determined at the point where the raw water is removed from the same body of water, except that it shall be the point where the water enters the water suppliers distribution system where the water treatment system removes any of the identified toxic substances from the raw water supply. Mass shall be determined by multiplying the concentration of the toxic substance by the volume of the facilitys intake flow received from the water system. Following establishment of a TMDL developed under R 323.1207 for the water body segment encompassing the facility, any use of no net addition limits shall be consistent with the TMDL.

Note: The Water Quality Guidance for the Great Lakes System, 40 C.F.R. Part 132 (1995), indicates that a permit may not authorize no net addition limits that are effective after March 23, 2007. The preamble to 40 C.F.R. Part 132 indicates that the environmental protection agency (EPA) will revisit this requirement by March 23, 2002, to consider possible extensions. After the redetermination by EPA, the department will consider modifying these rules to incorporate a phaseout date for no net addition limits, if still necessary.

(ii) If the intake toxic substance in a facilitys discharge originates from a water that is not the same body of water as the receiving water, then WQBELs shall be established based upon the most stringent water quality value for that toxic substance.

(iii) If a facility discharges an intake toxic substance that originates in part from the same body of water, and in part from a different body of water, then the department may apply the conditions of paragraphs (i) and (ii) of this subdivision to derive an effluent limitation reflecting the flow-weighted average of each source of the toxic substance.

Notes

Mich. Admin. Code R. 323.1211

1997 AACS; 2006 AACS