Chapter NR 106

Tss =   Tdir + (HLV x (L/100))

Where:

NR 106.55(5)(b) (b) Alternative heat loss value. An alternative heat loss value (HLV) may be used in the equation in par. (a). The alternative value shall be representative of seasonal influences on heat loss and be based on a comparison of effluent temperature at the location of discharge to the storm sewer or storm water conveyance channel and the point at which the storm sewer or storm water conveyance channel discharges to a surface water of the state.

NR 106.55(5)(c) (c) Site-specific information. The department may use available site-specific information to determine an alternative heat loss value or other data demonstrating the amount of heat loss in a storm sewer to establish an effluent temperature limitation for discharges to a storm sewer.

NR 106.55(6) (6) Limitations for receiving waters with unidirectional flow not designated as limited aquatic life. Except as provided in subs. (2) to (5), the department shall establish water quality-based effluent limitations to ensure that effluent is not discharged at elevated temperatures that may adversely affect humans or aquatic life at or near the point of discharge for discharges to surface waters with unidirectional flow.

NR 106.55(6)(a) (a) Flow ratio categories. Effluent temperature limitations shall be established based upon the designated use of the water and the ratio of streamflow to effluent flow as determined in Table 1. Effluent flow shall be equal to the value specified in s. NR 106.53 (2) (a).

Table 1 — Flow Ratio Categories

NR 106.55(6)(b) (b) Calculation of limitations. The methods described in this paragraph apply to the determination of both acute and sub-lethal effluent temperature limitations. Water quality-based effluent temperature limitations to meet the requirements of this subsection shall be determined using the following procedures:

WQBEL = [((WQC - Ta)(Qs + (1 - f)Qe)) / Qe] + Ta

Where:

NR 106.55(6)(c) (c) Limitations for mussel control. Short-term excursions from the effluent temperature limitation determined in this subsection may occur for the purposes of zebra or other mussel control if approved by the department and authorized in a permit on a case-by-case basis.

NR 106.55(6)(d) (d) More stringent limitations. The department shall establish more stringent effluent temperature limitations than those determined under the provisions of this subsection whenever it is demonstrated that the temperature of the discharge may cause or contribute to nonattainment of aquatic life uses and that more stringent limitations are necessary to assure the protection and propagation of a balanced indigenous population of shellfish, fish and wildlife in or on the body of water into which the discharge is made. Effluent temperature limitations under this paragraph shall be established whenever one or more of the mixing zone requirements in s. NR 102.05 (3), as they apply to temperature, are not maintained.

NR 106.55(7) (7) Limitations for inland lakes, impoundments and great lakes waters. The department shall establish water quality-based effluent limitations to ensure that the effluent is not discharged at elevated temperatures that may adversely affect humans or aquatic life at or near the point of discharge for discharges to surface waters that are inland lakes, impoundments, or Great Lakes waters that do not exhibit unidirectional flow.

NR 106.55(7)(a) (a) Limitations for mussel control. Short-term excursions from the effluent temperature limitation determined in this subsection may occur for the purposes of zebra or other mussel control if approved by the department and authorized in a permit on a case-by-case basis.

NR 106.55(7)(b) (b) Calculation of limitations. The methods described in this paragraph apply to the determination of both acute and sub-lethal effluent temperature limitations. Water quality-based effluent temperature limitations to meet the requirements of this subsection shall be determined using the following procedures:

WQBEL = [(WQC- Ta)/(e-a)] + Ta

Where:

a = [(A)(54.7 + B(150))] / [(8,345,000)(Qe)]

Where:

A =   Area of mixing zone in square feet, as follows:

B = A coefficient which is a function of Ta as follows:

Qe =   Effluent flow rate in mgd as specified in s. NR
  106.53 (2)

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 Note Note: 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)(a) (a) A mixing zone analysis that details the full extent and condition of the mixing zone.

NR 106.55(10)(b) (b) A demonstration that such effluent temperature limitations meet all mixing zone provisions of s. NR 102.05 (3).

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 History History: 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 NR 106.56 Establishment of water quality-based effluent limitations for temperature in WPDES permits.

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)(a) (a) The highest recorded representative daily maximum effluent temperature as measured or determined according to s. NR 106.54 (1).

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:

NR 106.56(3)(a) (a) The highest weekly average effluent temperature for the month as measured or determined according to s. NR 106.54 (2).

NR 106.56(3)(b) (b) The projected 99th percentile of all representative weekly average effluent temperatures for the month as measured or determined according to s. NR 106.54 (2).

NR 106.56(4) (4) Reasonable potential to exceed a limited aquatic life effluent limitation. A daily maximum effluent temperature limitation of 86°F shall be established in a WPDES permit for each month in which the representative daily maximum effluent temperature exceeds 86°F for discharges to limited aquatic life waters not classified as a wastewater effluent channel according to s. NR 104.02 (1), storm sewers or as a wetland regulated under ch. NR 103.

NR 106.56(5) (5) Reasonable potential to exceed a wastewater effluent channel effluent limitation. A daily maximum effluent temperature limitation of 120°F shall be established in a WPDES permit for each month in which the representative daily maximum effluent temperature exceeds 120°F for discharges to a wastewater effluent channel, as classified in s. NR 104.02 (1).

NR 106.56(6) (6) Reasonable potential to exceed a storm sewer effluent limitation. A daily maximum effluent temperature limitation greater than 120°F shall be established in a WPDES permit for a discharge to a storm sewer for each month in which the representative daily maximum effluent temperature exceeds the limitation determined according to the procedure in s. NR 106.55 (5).

NR 106.56(7) (7) Reasonable potential to exceed a wetland effluent limitation. A daily maximum or weekly average effluent temperature limitation shall be established in a WPDES permit for each month in which the representative daily maximum or weekly average effluent temperature, respectively, exceeds the limits for a discharge to a wetland determined according to the provisions in s. NR 106.55 (4).

NR 106.56(8) (8) Reasonable potential to exceed limitations for the protection of public health and welfare. A daily maximum effluent temperature limitation of 120°F shall be established in a WPDES permit for each month in which the representative daily maximum effluent temperature exceeds 120°F, unless the permittee demonstrates to the satisfaction of the department that the heated effluent is not discharged in a manner that will cause a potential for scalding of humans.

NR 106.56(9) (9) Limitations to protect downstream waters. Whenever the department determines that more stringent effluent temperature limitations than those established according to subs. (1) through (6) are necessary to attain or maintain water quality standards in downstream or other adjacent waters and the representative daily maximum or weekly average effluent temperatures exceed the limitations, then more stringent effluent temperature limitations shall be established in a WPDES permit.

NR 106.56(10) (10) Limitations to protect for cold shock. The department shall determine on a case-by-case basis if any additional conditions are necessary in a WPDES permit to protect against cold shock and in accordance with the standard specified in s. NR 102.28. Provisions under this subsection shall be in addition to the water quality-based effluent temperature limitations determined under this section.

NR 106.56(11) (11) Limitations to protect for rate of temperature change. The department shall determine on a case-by-case basis if any conditions are necessary in a WPDES permit to protect against detrimental health or reproductive effects to fish and aquatic life caused by excessive rates of temperature change.

NR 106.56(12) (12) Representative data unavailable. Whenever after October 1, 2010, the department issues or reissues a permit to a discharger for which representative effluent temperature data as described in s. NR 106.54 is not available, the following requirements shall be included in the issued or reissued permit:

NR 106.56(12)(a) (a) Monitoring to obtain representative effluent temperature as described in s. NR 106.54. Monitoring shall be required for a period of not less than one year. When effluent temperatures in any month are highly variable, monitoring for 2 years may be required. If the facility only operates during certain portions of the year, representative effluent temperature shall be measured during the period of operation.

NR 106.56(12)(b) (b) Water quality-based effluent temperature limitations determined under applicable methods described in s. NR 106.55 and as determined necessary under any applicable provision of this section. Compliance with the limitations shall be attained as soon as reasonably possible, but no later than the expiration date of the permit. The department may modify the permit at any time during the permit term and establish a compliance date to attain effluent temperature limitations sooner than the expiration date of the permit.

NR 106.56(12)(c) (c) If, after the data collection required under par. (a), it is determined that an effluent temperature limitation is not necessary under any applicable provision of this section, the water quality-based effluent temperature limitations in the permit may not be effective. A condition shall be included in the permit that invalidates any effluent temperature limitations and the compliance schedule in the permit. Continued monitoring of effluent temperature may be required.

NR 106.56(13) (13) Monitoring. The department shall establish on a case-by-case basis the monitoring and reporting frequency for temperature in a WPDES permit.

NR 106.56(14) (14) Limitations in permits. Effluent temperature limitations of 86oF, 120oF or greater than 120oF determined necessary under subs. (4) to (7) shall be expressed in permits as daily maximum effluent temperature limitations.

NR 106.56(14)(a) (a) Acute effluent temperature limitations determined necessary under this section shall be expressed in permits as daily maximum effluent temperature limitations.

NR 106.56(14)(b) (b) Sub-lethal effluent temperature limitations determined necessary under this section shall be expressed in permits as weekly average effluent temperature limitations.

NR 106.56(14)(c) (c) In all cases, monitoring data collected for purposes of reporting and determining compliance shall be representative effluent temperature data as described in s. NR 106.54.

NR 106.56 History History: CR 07-111: cr. Register September 2010 No. 657, eff. 10-1-10.

NR 106.57 NR 106.57 Effluent limitations for multiple thermal discharges. Whenever the department determines that more than one thermal discharge may be adversely affecting the water quality of the same receiving water, the provisions of both this subchapter and s. NR 106.11 shall be used to calculate the combined allowable heat load from the discharges necessary to meet the water quality criteria for temperature as specified in ch. NR 102. The resultant allowable thermal load shall be divided among the various discharges using an allocation method based on site-specific considerations. Whenever the department makes a determination under this subsection, the department shall specify the reasonable potential basis for any effluent temperature limitation and shall notify all permittees who may be affecting the water quality of the same receiving water of the determination and any limitations developed under this section. Any modifications to WPDES permits to account for multiple discharges shall include an opportunity for public comment pursuant to ch. 283, Stats.

NR 106.57 History History: CR 07-111: cr. Register September 2010 No. 657, eff. 10-1-10.

NR 106.58 NR 106.58 Effluent limitations based on water quality models.

NR 106.58(1) (1) At the time of permit application, a permittee may submit the results of scientifically defensible technical approaches, such as calibrated models and verified mathematical water quality models developed or adapted for a particular water body, simplified modeling approaches as outlined in “WATER QUALITY ASSESSMENT” (EPA-600/6-82-004), or other dynamic methods to be utilized in developing water quality-based effluent limitations.

NR 106.58(2) (2) Data used to support the analyses conducted under sub. (1) shall be representative of the long-term characteristics of the receiving water and shall be collected in a manner consistent with requirements of ch. NR 219.

NR 106.58(3) (3) The department shall review the results of the analyses conducted under sub. (1) on a case-by-case basis and shall determine the water quality-based effluent limitations necessary to ensure that the applicable water quality standards specified in ch. NR 102 are maintained.

NR 106.58(4) (4) Effluent limitations approved under this section are in lieu of the procedures in s. NR 106.55 (5), (6), and (7), and are not modifications to the water quality criteria specified in ch. NR 102.

NR 106.58 History History: CR 07-111: cr. Register September 2010 No. 657, eff. 10-1-10.

NR 106.59 NR 106.59 Effluent limitations for temperature for permits issued to publicly or privately owned domestic sewage treatment works.

NR 106.59(1) (1) Applicability. This section applies to specific outfalls from permittees with discharges subject to ch. NR 210.

NR 106.59(2) (2) Definitions. In this section, the following definitions are applicable to terms used:

NR 106.59(2)(a) (a) “Dissipative cooling” means the cooling effects associated with heat loss to the ambient water, the atmosphere and the surrounding environment.

NR 106.59(2)(b) (b) “Estimated daily maximum effluent temperature” means the highest temperature expected in a calendar day based on an average of effluent temperatures available. Available data may be from at least two other POTWs within a 100 mile radius that utilize similar wastewater treatment technology and have a similar ratio of domestic to industrial waste stream composition, or representative data of the POTW.

NR 106.59(2)(c) (c) “Existing POTW outfall” means any discharge structure that has been included in a WPDES permit issued prior to October 1, 2010, that was used to convey wastewater effluent to a surface water and has not been re-located.

NR 106.59(2)(d) (d) “New POTW discharge” means any point source subject to ch. NR 210 that has not received a WPDES permit from the department prior to October 1, 2010 or a permitted outfall re-located to a new receiving water after October 1, 2010.

NR 106.59(2)(e) (e) “POTW” means all publicly operated treatment works and privately owned domestic sewage treatment works subject to ch. NR 210.

NR 106.59(2)(f) (f) “Re-located POTW outfall” means any point source outfall structure associated with a previously issued WPDES permit that is moved or constructed after October 1, 2010 to convey wastewater to the same receiving water where fish and other aquatic life are materially exposed to a modified thermal pollutant load.

NR 106.59 Note Note: The department considers an outfall to be re-located when an assemblage of fish and other aquatic life are subjected to a heat load that they were not exposed to previously. In determining whether a change in location is a re-located outfall, the department shall consider the distance of the changed location, the potential for the heat load to adversely impact resident organisms, and whether or not the applicable provisions of s. NR 102.05 (3) are satisfied.

NR 106.59(3) (3) Acute limitations for existing POTW outfalls.

NR 106.59(3)(a) (a) The department shall establish acute effluent temperature limitations for an existing POTW outfall to surface waters classified as limited aquatic life whenever the representative daily maximum effluent temperature is greater than the applicable water quality criterion specified in s. NR 102.245.

NR 106.59(3)(b) (b) The department shall establish acute effluent temperature limitations for an existing POTW outfall to surface waters classified as cold water, warm water sport fish, warm water forage fish, or limited forage fish whenever the representative daily maximum effluent temperature is greater than the applicable water quality criterion specified in s. NR 102.25 or determined under s. NR 102.27. The applicable acute water quality criterion shall be based on representative ambient temperature of the receiving stream determined as follows:

NR 106.59(3)(b)1. 1. Except as provided in subd. 2., the representative ambient temperature shall be equal to the ambient temperatures in s. NR 102.25 or approved under s. NR 102.26.

NR 106.59(3)(b)2. 2. Where the Qe of a permitted POTW is significantly greater than the Qs of the receiving stream immediately upstream of the POTW outfall, the representative ambient temperature may be equal to the daily maximum effluent temperature.

NR 106.59(3)(b)3. 3. The provisions of subd. 2. are not applicable to a permitted POTW with a discharge outfall that shares a mixing zone with an upstream discharger.

NR 106.59(4) (4) Sub-lethal limitations for existing POTW outfalls. Upon request by the POTW at the time of permit application, the department may account for dissipative cooling of a POTW effluent in determining the need for sub-lethal effluent limitations. The department shall establish sub-lethal effluent limitations for an existing POTW outfall whenever the department determines that the effluent has a reasonable potential to cause or contribute to an exceedance of the applicable sub-lethal criterion outside of a small area of mixing and cooling. In determining the need for sub-lethal effluent limitations, the department shall consider the cooling of the effluent through dissipation of heat to the environment to the extent that a POTW provides information to support such determination as set forth below.