Chapter NR 106

NR 106.06(5)(a) (a) Receiving water.

NR 106.06(5)(a)1. 1. The geometric mean of available data for the receiving water shall be used, except the arithmetic mean for pH shall be used.

NR 106.06(5)(a)2. 2. Representative seasonal values may be used.

NR 106.06(5)(a)3. 3. If information on the water quality parameters is not available, then information on the quality of similar water bodies in the area and best professional judgment may be used.

NR 106.06(5)(a)4. 4. The receiving water value of the water quality parameter shall be used to determine the effluent limitation. The receiving water value may be modified to account for the mixture of the receiving and effluent flows when any of the following conditions occur:

NR 106.06(5)(a)4.a. a. When the value of the water quality parameter in the effluent is significantly greater than or less than the value in the receiving water;

NR 106.06(5)(a)4.b. b. When the effluent flow is relatively large in comparison to the receiving water flow used in the calculation of the effluent; or

NR 106.06(5)(a)4.c. c. When, as a result of demonstrated or measured physical, chemical or biological reactions, the value of the water quality parameter, after mixing of the receiving water and the effluent, is significantly different than the background value of the water quality parameter in the receiving water.

NR 106.06(5)(b) (b) Effluent.

NR 106.06(5)(b)1. 1. The geometric mean of available data for the effluent shall be used, except the arithmetic mean for pH shall be used.

NR 106.06(5)(b)2. 2. If information on the water quality parameters is not available, then values representative of similar effluents may be used.

NR 106.06(6) (6) Effluent limitations based upon elevated background concentrations. Whenever the representative background concentration for a toxic or organoleptic substance in the receiving water is determined to be greater than any applicable water quality criterion or secondary value for that substance, the calculation of an effluent limitation and the determination of the need for the limitation in a permit shall be performed subject to all of the following:

NR 106.06(6)(a) (a) If the department has developed an EPA approved TMDL for the toxic or organoleptic substance in the receiving water, an effluent limitation for that substance shall be consistent with the TMDL.

NR 106.06(6)(b) (b) If no EPA approved TMDL has been developed and if the intake source of the wastewater is all from the same waterbody as the receiving water of the discharge, the department may determine that the discharge does not have a reasonable potential to cause or contribute to an excursion above the applicable water quality criterion or secondary value for the substance, and may determine that a numeric limitation is not necessary, provided the permittee has demonstrated that all of the following conditions are met:

NR 106.06(6)(b)1. 1. The permittee withdraws 100 percent of the intake water containing the substance from the same waterbody into which the discharge is made.

NR 106.06(6)(b)2. 2. The permittee does not contribute any additional mass of the identified intake substance to its wastewater.

NR 106.06(6)(b)3. 3. The permittee does not alter the identified intake substance chemically or physically in a manner that would cause adverse water quality impacts to occur that would not occur if the substance were left in-stream.

NR 106.06(6)(b)4. 4. The permittee does not contribute to a statically significant increase in the identified intake substance concentration, as determined by the department, at the edge of the mixing zone or at the point of discharge if a mixing zone is not allowed, as compared to the concentration of the substance in the intake water, unless the increased concentration does not cause or contribute to an excursion of water quality standard for that substance.

NR 106.06(6)(b)5. 5. The timing and location of the discharge would not cause adverse water quality impacts to occur that would not occur if the identified intake substance were left in the receiving waterbody.

NR 106.06(6)(c) (c) If no TMDL has been developed and the conditions in par. (b) are not met, an effluent limitation shall be included in the permit if the department determines that the discharge has a reasonable potential to cause or contribute to an excursion above the applicable water quality criterion or secondary value for the substance. The limitation shall be applied as follows:

NR 106.06(6)(c)1. 1. For discharges within the Great Lakes system, the effluent limitation for that substance shall be equal to the most stringent applicable water quality criterion or secondary value.

NR 106.06(6)(c)2. 2. For discharges outside of the Great Lakes system:

NR 106.06(6)(c)2.a. a. When all of the intake source of the wastewater is from the same waterbody as the receiving water of the discharge and the permittee has demonstrated that the conditions in par. (b) 3. to 5. are met the effluent limitation for that substance shall equal the representative background concentration of that substance in the receiving water. If the conditions in par. (b) 3. to 5. are not met, the effluent limitation for that substance shall be equal to the most stringent applicable water quality criterion or secondary value for that substance.

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.