Chapter NR 106

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.

NR 106.59(4)(a) (a) The POTW shall provide any of the following information to allow the department to determine whether or not sub-lethal criteria are exceeded outside a small area of mixing and cooling.

NR 106.59(4)(a)1. 1. A written description of the physical characteristics of the receiving water or outfall that encourage rapid dilution, diffusion, dispersion, or dissipation of heat.

NR 106.59(4)(a)2. 2. A written description of the presence or absence of other thermal loads to the receiving stream.

NR 106.59(4)(a)3. 3. The minimum and maximum effluent temperature for each calendar week for each permitted outfall over the past two years.

NR 106.59(4)(b) (b) In addition to the information submitted in par. (a), the POTW shall submit existing information it has collected, generated, reviewed, or received regarding the following site-specific conditions:

NR 106.59(4)(b)1. 1. Information regarding the biological quality of the animal and plant community of the receiving water including, but not limited to, species composition, richness, diversity, density, distribution, age structure, spawning incidence, and presence of any state or federally listed threatened or endangered species.

NR 106.59(4)(b)2. 2. Data concerning the physical characteristics of the receiving water or permitted outfalls that encourage rapid dilution, diffusion, dispersion, and/or dissipation of heat.

NR 106.59(4)(b)3. 3. The minimum and maximum temperature of the receiving water upstream of all permitted outfalls for each calendar month over the past two years.

NR 106.59(4)(c) (c) In evaluating the potential for exceedance of sub-lethal criteria outside a small area of mixing and cooling, the department shall consider site-specific information including, but not limited to:

NR 106.59(4)(c)1. 1. The physical characteristics of the receiving water including those related to mixing, turbulence, diffusion, dilution, dispersion, and heat dissipation.

NR 106.59(4)(c)2. 2. The occurrence of other thermal mixing zones and their influence on the dissipative potential of the receiving water.

NR 106.59(4)(c)3. 3. The variability of effluent temperature from the POTW.

NR 106.59(4)(c)4. 4. The expected difference between the ambient receiving water temperature and the representative effluent temperature.

NR 106.59(4)(c)5. 5. The attainment status of the receiving water biological community in response to the discharge of heated effluent.\

NR 106.59(4)(c)6. 6. The potential impacts to state or federally listed threatened or endangered species.

NR 106.59 Note Note: The absence of information pertaining to subds. 1. to 6., shall not preclude a determination that a sub-lethal effluent limitation is not necessary.

NR 106.59(4)(d) (d) In addition to the requirements in pars. (a) and (b), the department reserves the right to request additional information from the POTW to support the request for consideration of dissipative cooling.

NR 106.59(4)(e) (e) If the department determines that a sub-lethal effluent limitation for temperature is not necessary, a specific request for comment on the department’s determination shall be included in the public notice for the proposed permit.

NR 106.59(5) (5) Acute limitations for new POTW discharges or re-located POTW outfalls.

NR 106.59(5)(a) (a) The department shall establish acute effluent temperature limitations for a new POTW discharge or re-located POTW outfall to a surface water classified as limited aquatic life whenever the estimated daily maximum effluent temperature is greater than the applicable water quality criterion specified in s. NR 102.245.

NR 106.59(5)(b) (b) The department shall establish acute effluent temperature limitations for a new POTW discharge or re-located POTW outfall to a surface water classified as cold water, warm water sport fish, warm water forage fish, or limited forage fish whenever the estimated 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 the ambient temperatures in s. NR 102.25 or approved under s. NR 102.26.

NR 106.59(6) (6) Sub-lethal limitations for new POTW discharges or re-located 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 a new POTW discharge or re-located POTW outfall whenever it is determined 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:

NR 106.59(6)(a) (a) The POTW shall provide any of the following information to allow the department to determine whether or not the sub-lethal criteria are exceeded outside of a small area of mixing and cooling:

NR 106.59(6)(a)1. 1. A written description of the physical characteristics of the receiving water or outfall that encourage rapid dilution, diffusion, dispersion, and dissipation of heat.

NR 106.59(6)(a)2. 2. A written description of the presence or absence of other thermal loads to the receiving water.

NR 106.59(6)(a)3. 3. The minimum and maximum known effluent temperature for each calendar week for each previously permitted outfall over the past two years.

NR 106.59(6)(a)4. 4. The maximum expected effluent temperature for each calendar month for each new outfall.

NR 106.59(6)(b) (b) In addition to the information submitted in par. (a), the POTW shall submit existing information it has collected, generated, reviewed, or received regarding the following site-specific conditions: