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(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)(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)(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(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).