Chapter NR 106

NR 106.06(6)(c)2.b. b. When all of the intake source of the wastewater is from a waterbody that is different than the receiving water of the discharge, the effluent limitation for that substance shall be equal to the lowest applicable water quality criterion or secondary value.

NR 106.06(6)(c)2.c. c. When the intake source of the wastewater is in part from the same waterbody as the receiving water and in part from a different waterbody, the effluent limitation may be derived using subd. 2 .a and b. to reflect the flow-weighted average of each source of the wastewater, provided that adequate monitoring to determine compliance can be established and is included in the permit.

NR 106.06(6)(d) (d) The determination of representative background concentrations for toxic or organoleptic substances in this subsection shall be statistically (P £ 0.01) or otherwise appropriately determined as the reasonably expected maximum background concentration for that substance.

NR 106.06(6)(e) (e) For purposes of this subsection, an intake pollutant in the source water is considered to be from the same waterbody as the receiving water of the discharge if the permittee successfully demonstrates all of the following to the department:

NR 106.06(6)(e)1. 1. That the pollutant would have reached the outfall point in the receiving water within a reasonable period had it not been withdrawn by the permittee.

NR 106.06(6)(e)2. 2. That the background concentration of the pollutant in the receiving water is at a similar concentration level to that in the intake water.

NR 106.06(6)(e)3. 3. That other water quality characteristics, including temperature, pH and hardness are similar in the intake water and the receiving water.

NR 106.06 Note Note: The term “same waterbody” may include a hydrologic connection between groundwater and surface water. See definition in s. NR 106.03 (11m).

NR 106.06(7) (7) Applicability of water quality criteria expressed as dissolved concentrations. Effluent limitations may be established in a permit under this subsection based upon the acute and chronic aquatic life toxicity criteria expressed as dissolved concentrations that are determined using the procedures specified in ss. NR 105.05 (5) and 105.06 (8). Effluent limitations for metals calculated under this section shall be expressed as total recoverable in a permit. All of the following shall apply in establishing effluent limitations under this subsection:

NR 106.06(7)(a) (a) Determine the effluent limitations according to the procedures specified in this chapter using the water quality criteria expressed as total recoverable from tables 1 to 6 in ch. NR 105. Determine the necessity for water quality based effluent limitations according to s. NR 106.05. If the procedures in s. NR 106.05 do not result in the need for effluent limitations based upon the total recoverable criteria, then no limitations shall be established in the permit and there is no further review. If the procedures in s. NR 106.05 do result in the need for effluent limitations based upon the total recoverable criteria, then the limitations shall be established in the permit or the permittee may request that effluent limitations be established based on criteria expressed as dissolved concentrations according to par. (b).

NR 106.06(7)(b) (b) If, following the procedures in par. (a), the permittee requests that effluent limitations be established based on criteria expressed as dissolved concentrations, the department shall determine the effluent limitations according to the procedures specified in this chapter using WQTRAN, the water quality criterion expressed as a dissolved concentration, and shall determine the necessity for water quality based effluent limitations according to s. NR 106.05. If the procedures in s. NR 106.05 do not result in the need for effluent limitations based upon the criteria expressed as dissolved concentrations, WQTRAN, then no limitations shall be established in the permit and the monitoring conditions in par. (c) 1. shall be included in the permit. If the procedures in s. NR 106.05 do result in the need for effluent limitations based upon the criteria expressed as dissolved concentrations, then the limitation is established in the permit and the requirements in par. (c) apply.

NR 106.06(7)(c) (c) If, following the procedures in par. (b), effluent limitations are established based upon water quality criteria expressed as dissolved concentrations, then the following shall also be included in the permit:

NR 106.06(7)(c)1. 1. Monitoring requirements which may include, but are not limited to, effluent monitoring, monitoring of effluent toxicity, in-stream monitoring for unfiltered and filtered substances which may be limited in the permit, or other monitoring. Testing methods which allow appropriately sensitive detection limits may also be specified.

NR 106.06(7)(c)2. 2. Conditions which require the permittee to document that reasonable steps have been taken to minimize or eliminate the sources of the substances for which effluent limitations expressed as dissolved concentrations have been established in the permit. The documentation may consist of implementation of a formal pre-treatment program, pollution reduction activities, and other documented efforts which are reasonably likely to reduce or eliminate sources of the substance. The documentation shall be submitted as specified in the permit, unless, prior to issuance of the permit, documented source elimination or reduction efforts have occurred. If reasonable steps have not been taken as specified in the permit, the department may establish effluent limitations based upon a water quality criterion expressed as total recoverable concentrations.

NR 106.06(7)(d) (d) The procedures in pars. (a) to (c) may also be used to establish effluent limits based on aquatic life secondary values.

NR 106.06(8) (8) Cumulative risk for human carcinogens.

NR 106.06(8)(a) (a) If an effluent for a particular discharger contains more than one substance for which a human cancer criterion (HCC) exists at levels which warrant water quality based effluent limits, the incremental risk of each carcinogen should be assumed to be additive. Except as provided in par. (b), the water quality based limitation for each carcinogen shall be established in a permit to protect against additive or synergistic effects possibly associated with simultaneous multiple chemical human exposure such that the following condition is met:

Where:

NR 106.06 Note Note: This additional condition is equivalent to a total incremental risk of cancer due to multiple chemicals not exceeding 10-5.

NR 106.06(8)(b) (b) If information is provided to the department that the carcinogenic risk is not additive, the limitations for each carcinogen will be determined based on that information.

NR 106.06(9) (9) Sediment deposition. The limitations calculated according to the procedures in this section may be reduced to prevent contamination of sediment with toxic substances or to prevent accumulation of the substance in sediments if determined necessary to protect water quality.

NR 106.06(10) (10) Environmental fate. The limitations calculated pursuant to this section may be modified to account for degradation of the substance based on information available to the department provided that:

NR 106.06(10)(a) (a) The rate of degradation is documented by field studies supplied by the discharger, and

NR 106.06(10)(b) (b) The field studies demonstrate rapid and significant loss of the substance inside the mixing zone under the full range of critical conditions expected to be encountered; and

NR 106.06(10)(c) (c) The field studies are reviewed and approved by the department.

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)

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

Table 2 — Daily Multiplication Factor

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)

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: