Chapter NR 106

NR 106.06(11) (11) Other methods of calculation. In lieu of sub. (4), scientifically defensible technical approaches such as calibrated and verified mathematical water quality models developed or adapted for a particular stream, simplified modeling approaches as outlined in “WATER QUALITY ASSESSMENT” (EPA-600/6-82- 004), or dynamic methods may be utilized in developing water quality based effluent limitations such that applicable water quality standards specified in chs. NR 102 to 105 are maintained.

NR 106.06 History History: Cr. Register, February, 1989, No. 398, eff. 3-1-89; am. (1) (a), (4) (c) 12., (d) 1., (4) (e) 1.,(6) (e), cr. (1) (b) 2., (2), (3) (d), (4) (c) 7. to 11., (d) 2., (e) 3., (5) (a) 4., (6) (c) 2., (d), (7), renum. (1) (b), (2) (a) to (c), (3) (a) to (c) 6., 9., (d) 1. and 3., (e) 1. to 6., (4) to (8) to be (8) to (11) and am. (3) (b), (c) (intro.), 4. to 6., (4) (a), (b) (intro.) 1., 2.,, (c) 4. and 5., (6) (a) to (c), (11) (d) 2., (4) (e) 3., (5) (a) 4., (6) (c) 2. and (d) 5. and (7), r. (2) (d), (3) (c) 7. and 8., (d) 2., (e) 7., Register, August, 1997, No. 500, eff. 9-1-97; CR 09-123: am. (4) (e) (title) Register July 2010 No. 655, eff. 8-1-10; CR 15-084: r. (2) (a), (b), cr. (2) (am), (bg), (br), r. and recr. (6) Register August 2016 No. 728, eff. 9-1-16; CR 15-085: r. and recr. (3) (b), cr. (3) (bm), am. (3) (c) (intro.), 4., 5., cr. (3) (e), (4) (f), am. (7) (intro.) Register August 2016 No. 728, eff. 9-1-16; correction in (3) (c) (intro.) made under s. 35.17, Stats., Regiter August 2016 No. 728.

NR 106.07 NR 106.07 Application of and compliance with water quality based effluent limitations in permits.

NR 106.07(1) (1) Permit monitoring frequency. The department shall determine on a case-by-case basis the monitoring frequency to be required for each water quality based effluent limitation in a permit.

NR 106.07(2) (2) General. Except as provided in subs. (3) and (4), a chemical specific water quality-based effluent limitation that is calculated under this chapter shall be expressed in the permit as both a concentration limitation and a mass limitation unless the pollutant cannot appropriately be expressed by mass or a mass limitation is infeasible because the mass of the pollutant cannot be related to a measure of operation. Water quality-based mass limits for discharges of chlorine are not required in permits. The concentration limitation shall be expressed in units of mg/L or equivalent units. The mass limitation shall be expressed in units of kg/day or equivalent units. All of the following procedures shall be used when calculating mass limitations:

NR 106.07(2)(a) (a) For dischargers subject to ch. NR 210, an acute toxicity based concentration limitation that is derived by the procedure in s. NR 106.06 shall be converted to a mass limitation by using the discharger’s maximum effluent flow, expressed as a daily total flow, that is anticipated to occur for 24 continuous hours during the design life of the treatment facility.

NR 106.07(2)(b) (b) For all other dischargers not subject to ch. NR 210, an acute toxicity based concentration limitation that is derived by the procedures in s. NR 106.06 shall be converted to a mass limitation by using the discharger’s maximum effluent flow, expressed as a daily total flow, that has occurred for 24 continuous hours and represents normal operations. When calculating a mass limitation, the department may consider a projected increase in effluent flow that will occur when production is increased or modified, or another wastewater source, including storm water, that is added to an existing wastewater treatment facility. Limitations calculated under this paragraph are subject to the antidegradation requirements of ch. NR 207.

NR 106.07(2)(c) (c) A chronic toxicity, human health, or wildlife-based concentration limitation that is determined by the procedures in s. NR 106.06 shall be converted to a mass limitation by using the same effluent flow rate that was used in s. NR 106.06 (4) (d) to calculate the concentration limitation.

NR 106.07(2)(d) (d) A chronic toxicity-based mass limitation that is determined by the procedures in s. NR 106.11 shall be converted to a concentration limitation by using an effluent flow rate from s. NR 106.06 (4) (d).

NR 106.07 Note Note: An example of when a mass limitation is infeasible is water quality-based mass limits for discharges of temperature.

NR 106.07(3) (3) Expression of concentration limitations in permits for continuous discharges subject to ch. NR 210.

NR 106.07(3)(a) (a) Applicability. The procedures for expressing limitations in permits in this subsection apply to continuous discharges subject to ch. NR 210 when there is reasonable potential under s. NR 106.05 to exceed a water quality-based effluent limitation based on fish and aquatic life protection, human health, or wildlife protection that is calculated under s. NR 106.06. This subsection does not apply if another provision in this chapter or another Wisconsin administrative code chapter requires a different time period for expressing limits for a specific pollutant, type of discharge, or parameter, or if the department determines that expression of limitations in accordance with this subsection is impracticable under sub. (10).

NR 106.07 Note Note: An example of a different time period for expressing limits for a specific pollutant or parameter is WET limitations as specified in s. NR 106.09.

NR 106.07(3)(b) (b) Expression of water quality-based effluent limitations based on acute criterion. If there is reasonable potential under s. NR 106.05 to exceed a water quality-based effluent limitation calculated under s. NR 106.06 for a pollutant that is based on an acute criterion or secondary value, that limitation shall be expressed as a daily maximum and included in the permit.

NR 106.07(3)(c) (c) Expression of water quality-based effluent limitations based on chronic criterion. If there is reasonable potential under s. NR 106.05 to exceed a water quality-based effluent limitation calculated under s. NR 106.06 for a pollutant that is based on a chronic criterion or secondary value that limitation shall be expressed as a weekly average and included in the permit.

NR 106.07(3)(d) (d) Expression of water quality-based effluent limitations based on human health or wildlife criterion. If there is reasonable potential under s. NR 106.05 to exceed a water quality-based effluent limitation calculated under s. NR 106.06 for a pollutant that is based on a human health or wildlife criterion or secondary value that limitation shall be expressed as a monthly average and included in the permit.

NR 106.07(3)(e) (e) Additional permit limitations. Both a weekly average and monthly average permit limitation shall be included in a permit for a pollutant whenever any water quality-based effluent limitation for that pollutant is determined necessary under pars. (b) to (d). A daily maximum limitation shall be included in a permit in addition to the weekly average and monthly average limitation if the daily maximum limitation is determined necessary under par. (b). The department shall use all of the following procedures to include weekly average and monthly average limitations in permits:

NR 106.07(3)(e)1. 1. If a daily maximum limitation is the only limitation determined necessary for a pollutant under s. NR 106.05, a weekly average and monthly average limitation shall still be included in the permit and shall be set equal to the daily maximum limitation or the calculated weekly average and monthly average water quality-based effluent limitations, whichever is more restrictive.

NR 106.07(3)(e)2. 2. If a weekly average limitation is determined necessary for a pollutant under s. NR 106.05, but a monthly average limitation is not determined necessary for that pollutant in the permit under s. NR 106.05, a monthly average limitation shall still be included in the permit and shall be set equal to the weekly average limitation or the monthly average water quality-based effluent limitation calculated under s. NR 106.06, whichever is more restrictive. A daily maximum limitation shall be included if deemed necessary under s. NR 106.05.

NR 106.07(3)(e)3. 3. If a daily maximum and monthly average limitation are determined necessary in a permit for a pollutant under s. NR 106.05, but a weekly average limit is not necessary for that pollutant under s. NR 106.05, a weekly average limitation shall still be included in the permit for the pollutant and shall be set equal to the daily maximum limitation or the weekly average water quality-based effluent limitation calculated under s. NR 106.06, whichever is more restrictive.

NR 106.07(3)(e)4. 4. If a monthly average limitation is the only limitation determined to be necessary for a pollutant under s. NR 106.05, a weekly average limitation shall still be included in the permit and shall be set equal to the weekly average water quality-based effluent limitation calculated under s. NR 106.06, or a weekly average limitation calculated using the following procedure, whichever is more restrictive:

Weekly Average Limitation = (Monthly Average Limitation x MF)

- See PDF for table

- See PDF for table

NR 106.07(3)(e)5. 5. Limitations calculated under subds.1. to 4. shall be expressed in terms of concentration unless the department determines that a mass limitation is also necessary to protect fish and aquatic life, human health, or wildlife due to the variability of effluent flow or stream flow or other site-specific factors.

NR 106.07 Note Note: This methodology is based on the Technical Support Document for Water Quality-based Toxics Control (March 1991). PB91-127415.

NR 106.07(4) (4) Expression of concentration limitations in permits for continuous discharges not subject to ch. NR 210.

NR 106.07(4)(a) (a) Applicability. The procedures for expressing limitations in this subsection apply to continuous discharges that are not subject to ch. NR 210 and when there is reasonable potential under s. NR 106.05 to exceed a water quality-based effluent limitation based on fish and aquatic life protection, human health, or wildlife protection that is calculated under s. NR 106.06. This subsection does not apply if another provision in this chapter or another Wisconsin administrate code chapter requires a different time period for expressing limits that is specific to a pollutant, type of discharge, or other parameter, or if the department determines that expression of limitations in accordance with this subsection is impracticable under sub. (10).

NR 106.07 Note Note: An example of a different time period for expressing limits for a specific pollutant or parameter is WET limitations as specified in s. NR 106.09.

NR 106.07(4)(b) (b) Expression of water quality-based effluent limitations based on acute criterion. If there is reasonable potential under s. NR 106.05 to exceed a water quality-based effluent limitation calculated under s. NR 106.06 for a pollutant that is based on an acute criterion or secondary value that limitation shall be expressed as a daily maximum and included in the permit.

NR 106.07(4)(c) (c) Expression of water quality-based effluent limitations based on chronic criterion. If there is reasonable potential under s. NR 106.05 to exceed a water quality-based effluent limitation calculated under s. NR 106.06 for a pollutant that is based on a chronic criterion or secondary value that limitation shall be expressed as a weekly average and included in the permit.

NR 106.07(4)(d) (d) Expression of water quality-based effluent limitations based on human health or wildlife criterion. If there is reasonable potential under s. NR 106.05 to exceed a water quality-based effluent limitation calculated under s. NR 106.06 for a pollutant that is based on a human health or wildlife criterion or secondary value that limitation shall be expressed as a monthly average and included in the permit.

NR 106.07(4)(e) (e) Additional permit limitations. Both a daily maximum and monthly average permit limitation shall be included in a permit for a pollutant whenever any water quality-based effluent limitation for that pollutant is determined necessary under pars. (b) to (d). A weekly average limitation shall be included in a permit in addition to daily maximum and monthly average limitation if the weekly average limit is determined necessary under par. (c). The department shall use all of the following procedures to include daily maximum and monthly average limitations in permits:

NR 106.07(4)(e)1. 1. If a daily maximum limitation is the only limitation determined necessary for a pollutant under s. NR 106.05, a monthly average limitation shall still be included in the permit and set equal to the daily maximum limitation or the monthly average water quality-based effluent limitation calculated under s. NR 106.06, whichever is more restrictive.

NR 106.07(4)(e)2. 2. If a weekly average limitation is the only limitation determined necessary for a pollutant under s. NR 106.05 a monthly average limitation shall still be included in the permit and shall be set equal to the weekly average limitation or the monthly average water quality-based effluent limitation calculated under s. NR 106.06, whichever is more restrictive. A daily maximum limitation shall also be included in the permit and set equal to the daily maximum water quality-based effluent limitation calculated under s. NR 106.06 or a daily maximum limitation calculated using the following procedure, whichever is more restrictive:

Daily Maximum Limitation= WQBELc x DMF

- See PDF for table

Table 2 — Daily Multiplication Factor

- See PDF for table

NR 106.07(4)(e)3. 3. If a monthly average limitation is determined necessary, but a daily maximum limitation is not determined necessary for that pollutant under s. NR 106.05, a daily maximum limitation shall still be included in the permit and shall be set equal to the daily maximum water quality-based effluent limitation calculated under s. NR 106.06 or a daily maximum limitation calculated using the following procedure, whichever is more restrictive:

Daily Maximum Limitation = (Monthly Average Limitation x MF)

- See PDF for table

NR 106.07(4)(e)4. 4. Limitations calculated under subds. 1. to 3. shall be expressed in terms of concentration unless the department determines that a mass limitation is also necessary to protect fish and aquatic life, human health, or wildlife due to the variability of effluent flow or stream flow or other site-specific factors.

NR 106.07 Note Note: This methodology is based on the Technical Support Document for Water Quality-based Toxics Control (March 1991). PB91-127415.

NR 106.07(5) (5) Expression of concentration limitations in permits for noncontinuous discharges.

NR 106.07(5)(a) (a) Applicability. The procedures for expressing limitations in this subsection apply to seasonal discharges, discharges proportional to stream flow, or other unusual discharge situations that do not meet the definition of a continuous discharge under s. NR 205.03 (9g) when there is reasonable potential under s. NR 106.05 to exceed a water quality-based effluent limitation based on fish and aquatic life protection, human health, or wildlife protection. Water quality-based effluent limitations shall be calculated under s. NR 106.06.

NR 106.07(5)(b) (b) Acute reasonable potential. Pursuant to s. NR 106.05, if there is reasonable potential to exceed a water quality-based effluent limitation for a pollutant that is based on an acute criterion or secondary value then the acute concentration limitation calculated under s. NR 106.06 shall be expressed as a daily maximum and included in the permit.

NR 106.07(5)(c) (c) Chronic and human health or wildlife reasonable potential. Pursuant to s. NR 106.05, if there is reasonable potential to exceed a water quality-based effluent limitation for a pollutant based on a chronic, a human health, or a wildlife criterion or secondary value, limitations shall be included in the permit and expressed on a case-by-case basis. The department shall consider all of the following factors:

NR 106.07(5)(c)1. 1. Frequency and duration of discharge.

NR 106.07(5)(c)2. 2. Total mass of discharge.

NR 106.07(5)(c)3. 3. Maximum flow rate of discharge.

NR 106.07(5)(c)4. 4. Whether the pollutant is subject to a technology-based limitation or other limitation expressed by mass, concentration, or other appropriate measure in the permit.

NR 106.07(5m) (5m) Coefficient of variation.

NR 106.07(5m)(a) (a) The coefficient of variation (CV) shall be calculated as the ratio of the standard deviation of the representative effluent data divided by the arithmetic average of the representative effluent data, except as provided in par. (b).

NR 106.07(5m)(b) (b) If there are fewer than 10 representative data points the CV shall be set equal to 0.6.

NR 106.07(5m)(c) (c) When calculating the CV in par. (a) a monitoring result less than the limit of detection may be assigned a value of zero. If the effluent limitation is less than the limit of detection, the department may substitute a value other than zero for results less than the limit of detection, after considering the number of monitoring results that are greater than the limit of detection and if warranted when applying appropriate statistical techniques.

NR 106.07(6) (6) limitations below the level of detection or quantification. When the water quality based effluent limitation for any substance in a permit is less than the limit of detection or the limit of quantitation, the following conditions shall apply:

NR 106.07(6)(a) (a) The permittee shall perform monitoring required in the permit using an acceptable analytical methodology for that substance in the effluent which produces the lowest limit of detection and limit of quantitation.

NR 106.07(6)(b) (b) The permittee shall determine the limit of detection and limit of quantitation using a method specified by the department.

NR 106.07(6)(c) (c) Compliance with concentration and mass limitations shall be determined as follows:

NR 106.07(6)(c)1. 1. When the water quality based effluent limitation is less than the limit of detection, effluent levels less than the limit of detection are in compliance with the effluent limitation.

NR 106.07(6)(c)2. 2. When the water quality based effluent limitation is less than the limit of detection, effluent levels greater than the limit of detection, but less than the limit of quantitation are in compliance with the effluent limitation except when analytically confirmed and statistically confirmed by a sufficient number of analyses of multiple samples and use of appropriate statistical techniques. The department may require in a permit additional monitoring when effluent levels are between the limit of detection and the limit of quantitation.

NR 106.07(6)(c)3. 3. When the water quality based effluent limitation is greater than the limit of detection, but less than the limit of quantitation effluent levels less than the limit of detection or less than the limit of quantitation are in compliance with the effluent limitation.

NR 106.07(6)(d) (d) When the water quality based effluent limitation is expressed in the permit as a daily maximum or average mass limitation, compliance is determined according to par. (c) after converting the limit of detection and limit of quantitation to mass values using appropriate conversion factors and the actual daily effluent flow, or actual average effluent flow for the averaging period.

NR 106.07(6)(e) (e) Except as provided in this paragraph, when calculating an average or mass discharge level for determining compliance with an effluent limitation according to the provisions of par. (c), a monitoring result less than the limit of detection may be assigned a value of zero. If the effluent limitation is less than the limit of detection, the department may substitute a value other than zero for results less than the limit of detection, after considering the number of monitoring results that are greater than the limit of detection and if warranted when applying appropriate statistical techniques.

NR 106.07(6)(f) (f) Unless the permittee can demonstrate continuous compliance with the limit, the department shall include a condition in the permit requiring the permittee to develop and implement or update and implement a cost-effective pollutant minimization program as specified in s. NR 106.04 (5).

NR 106.07(7) (7) Whole effluent toxicity as alternative limit. The department may establish a whole effluent toxicity limitation according to s. NR 106.09 as an alternative to a chemical specific water quality-based effluent limitation based on a fish and aquatic life secondary acute or secondary chronic value determined according to ss. NR 105.05 (4) and 105.06 (6). The alternative whole effluent toxicity limitation shall meet all the following conditions:

NR 106.07(7)(a) (a) The fathead minnow (Pimephales promelas) or the cladoceran Ceridaphnia dubia were represented in the toxicological database used to generate the secondary value:

NR 106.07(7)(b) (b) The permittee has requested the alternative whole effluent toxicity limitation; and

NR 106.07(7)(c) (c) Whole effluent toxicity testing required in the permit shall be conducted at a frequency to be determined by the department, but at least once every 3 months during the entire term of the permit.

NR 106.07(8) (8) Secondary values and studies within the Great Lakes basin. If the effluent limitation based on a secondary value is established in a permit, a permittee discharging to the Great Lakes as defined in s. NR 102.22 (5) may request that additional time be added to the compliance schedule, according to s. NR 106.117 (2), for the permittee to conduct studies, other than studies for site-specific criteria under s. NR 105.02 (1), that are needed to propose a revision to the secondary value upon which the effluent limitation is based. During this time, the permittee may provide additional data necessary to either refine the secondary value or calculate a water quality criterion.

NR 106.07(9) (9) Wet weather mass limitations. In addition to the mass limitation calculated under sub. (2) (c), for a discharger subject to ch. NR 210 and which discharges on a year-around basis, the department shall include in the permit an alternative wet weather mass limitation. For purposes of compliance, this alternative wet weather mass limitation shall apply when the mass discharge level exceeds the mass limitation calculated under sub. (2) (c) and when the permittee demonstrates to the satisfaction of the department that the discharge exceedance is caused by and occurs during a wet weather event. For purposes of this subsection, a wet weather event occurs during and immediately following periods of precipitation or snowmelt, including but not limited to rain, sleet, snow, hail or melting snow, during which water from the precipitation, snowmelt or elevated groundwater enters the sewerage system through infiltration or inflow, or both. In calculating this alternative wet weather mass limitation, the department shall use the concentration limit determined by the procedures in s. NR 106.06, the appropriate conversion factor and the appropriate effluent flow given in either par. (a) or (b).

NR 106.07(9)(a) (a) For effluent limitations based on aquatic life chronic toxicity criteria or secondary chronic values, the maximum effluent flow, expressed as a daily average, that is anticipated to occur for 7 continuous days during the design life of the treatment facility.

NR 106.07(9)(b) (b) For effluent limitations based on wildlife, human threshold or human cancer criteria or secondary values, or taste and odor criteria, the maximum effluent flow, expressed as a daily average, that is anticipated to occur for 30 continuous days during the design life of the treatment facility.

NR 106.07(10) (10) Alternative methods for limit expression. The department may use an alternative method from the methodology specified in subs. (3) to (5) to express water quality-based effluent limitations in permits if the department determines that the methods in subs. (3) to (5) are impracticable and an alternative methodology is necessary and appropriate and adequately protective of the designated uses of the receiving and downstream waters as specified in ch. NR 102.

NR 106.07 History History: Cr. Register, February, 1989, No. 398, eff. 3-1-89; renum. (2) to (5) to be (3) to (6) and am., cr. (2), (6) (d) to (f) and (7) to (9), Register, August, 1997, No. 500, eff. 9-1-97; correction in (7) made under s. 13.93 (2m) (b) 1., Stats., Register, October, 1999, No. 526; correction in (8) made under s. 13.93 (2m) (b) 7., Stats., Register February 2004 No. 578; CR 09-123: am. (2) (intro.), (a) and (b) Register July 2010 No. 655, eff. 8-1-10; CR 15-085: cr. (1) (title), r. and recr. (2) to (5), cr. (5m), (6) (title), (7) (title), (8) (title), am. (8), cr. (9) (title), (10) Register August 2016 No. 728, eff. 9-1-16.

NR 106.08 NR 106.08 Determination of the necessity for whole effluent toxicity testing requirements and limitations.

NR 106.08(1) (1) General. The department shall establish whole effluent toxicity testing requirements and limitations whenever necessary to meet applicable water quality standards as specified in chs. NR 102 to 105 as measured by exposure of aquatic organisms to an effluent and specified effluent dilutions. When considering the necessity for whole effluent toxicity testing requirements and limitations, the department shall consider in-stream biosurvey data and data from ambient toxicity analyses, whenever such data are available.

NR 106.08(2) (2) Determination of necessity. If representative discharge data are available for an effluent being discharged from a point source, whole effluent toxicity testing requirements are necessary when any of the following apply:

NR 106.08(2)(a) (a) Existing aquatic life toxicity test data generated according to standard test protocols indicate a potential for an effluent from a point source discharge to adversely impact the receiving water aquatic life community.

NR 106.08(2)(b) (b) A water quality-based effluent limitation for a toxic substance is determined necessary in s. NR 106.05.

NR 106.08(3) (3) Representative data. Toxicity test data available to the department shall be considered representative when all of those data meet the following conditions:

NR 106.08(3)(a) (a) Data are representative of normal discharge conditions and current effluent quality.

NR 106.08(3)(b) (b) Data were produced by a lab certified or registered under ch. NR 149.

NR 106.08(3)(c) (c) Data were produced from toxicity test procedures specified in the permit.

NR 106.08(3)(d) (d) Data were produced from toxicity tests that met all applicable quality assurance or quality control requirements specified in the permit.

NR 106.08(4) (4) No representative data. If no representative discharge data are available for an effluent being discharged from a point source, whole effluent toxicity testing requirements are necessary if, in the judgment of the department, water quality standards may be exceeded. In such cases, all of the following factors shall be considered:

NR 106.08(4)(a) (a) Any relevant information that is available that indicates a potential for an effluent to impact the receiving water aquatic life community.

NR 106.08(4)(b) (b) Available dilution in the receiving water.