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:

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(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 HistoryHistory: 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(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(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(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: