NR 106.55(8)(8) Limitations for discharges with fluctuating or variable effluent flow rates. A permittee may request flow-related effluent temperature limitations for discharge flows that fluctuate or vary on a frequent basis. Flow-related effluent temperature limitations shall be determined as follows:

NR 106.55(8)(a)(a) At the time of permit application, the permittee shall submit representative minimum and maximum effluent flow data for the interval of variability for which effluent flow-related limitations are requested.

NR 106.55 NoteNote: For example, if the interval of variability is for a particular season or time of the year, then maximum and minimum effluent flow data submitted should be for that season.

NR 106.55(8)(b)(b) Effluent temperature limitations shall be determined following the procedures of subs. (6) or (7), as appropriate, using both the minimum and maximum effluent flow rates submitted in par. (a).

NR 106.55(8)(c)(c) Effluent temperature limitations determined in accordance with par. (b) shall be expressed in a permit as a function of effluent flow.

NR 106.55(8)(d)(d) Permits that contain flow-related effluent temperature limitations shall require daily monitoring of effluent temperature during times of discharge.

NR 106.55(9)(9) Limitations to protect downstream waters. The department may calculate more stringent effluent temperature limitations than those determined under this section whenever more stringent limitations are necessary to attain or maintain water quality standards in downstream or other nearby waters that may be affected by the heated discharge.

NR 106.55(10)(10) Limitations based on site-specific mixing zone analysis. The department may calculate effluent temperature limitations that differ from those determined under this section. A request by the permittee for a site specific mixing zone shall include all of the following:

NR 106.55(10)(c)(c) A demonstration that such effluent temperature limitations shall attain all aquatic life uses in the body of water into which the discharge is made.

NR 106.55(10)(d)(d) A demonstration that such effluent temperature limitations shall provide a level of protection equivalent to or better than that provided by the temperature water quality criteria in ch. NR 102.

NR 106.55(11)(11) Limitations based on installation of diffusers and other mechanical devices. The department may calculate effluent temperature limitations that differ from those determined under this section whenever the permittee installs diffusers or other mechanical devices used to ensure rapid mixing of effluent and significantly reduces or eliminates the size of the mixing zone. It shall be demonstrated that the resulting mixing zone meets all mixing zone provisions of s. NR 102.05 (3), and that the resulting mixing zone will attain all aquatic life uses in the body of water into which the discharge is made and provide a level of protection equivalent to or better than that provided by the temperature water quality criteria in ch. NR 102.

NR 106.55(12)(12) More stringent limitations. The department shall establish more stringent effluent temperature limitations than those determined under s. NR 106.55 (2) to (11) whenever the department determines that the discharge may cause or contribute to non-attainment of s. NR 102.04 (4) (e).

NR 106.55(13)(13) Limitations based on water quality models. The department may calculate water quality-based effluent limitations that differ from those specified in this section using water quality modeling submitted pursuant to s. NR 106.58.

NR 106.55 HistoryHistory: CR 07-111: cr. Register September 2010 No. 657, eff. 10-1-10; CR 15-085: am. Table 1 (title) Register August 2016 No. 728, eff. 9-1-16.

NR 106.56(1)(1) General. The department shall use the methods in this section to determine the need to establish water quality-based effluent temperature limitations in a permit.

NR 106.56(2)(2) Reasonable potential to exceed an acute effluent limitation. An acute water quality-based effluent limitation for temperature shall be established in a WPDES permit for each month in which the representative daily maximum effluent temperature for that month exceeds the acute water quality-based effluent limitation determined in s. NR 106.55. The representative daily maximum effluent temperature used in this subsection shall be the greater of the following:

NR 106.56(2)(b)(b) The projected 99th percentile of all representative daily maximum effluent temperatures as measured or determined according to s. NR 106.54 (1).

NR 106.56(3)(3) Reasonable potential to exceed a sub-lethal effluent limitation. A sub-lethal water quality-based effluent limitation for temperature shall be established in a WPDES permit for each month in which the representative weekly average effluent temperature for that month exceeds the sub-lethal water quality-based effluent limitation calculated in s. NR 106.55. The representative weekly average effluent temperature used in this subsection shall be the greater of the following: