Section NR 106.55 - Determination of water quality-based effluent limitations for temperature in WPDES permits(1) GENERAL. The department shall determine water quality-based effluent limitations for temperature to attain and maintain water quality standards and criteria specified in or determined according to procedures in subch. II of ch. NR 102.(2) LIMITATIONS FOR WATERS DESIGNATED AS LIMITED AQUATIC LIFE. The daily maximum effluent temperature limitation shall be 86°F for discharges to surface waters classified as limited aquatic life according to s. NR 104.02(3) (b) 1. and as defined in s. NR 104.02(1), except for those classified as wastewater effluent channels and for wetlands regulated under ch. NR 103.(3) LIMITATIONS FOR WATERS DESIGNATED AS WASTEWATER EFFLUENT CHANNELS. The daily maximum effluent temperature limitation shall be 120°F for discharges to surface waters classified as limited aquatic life wastewater effluent channels according to s. NR 104.02(3) (b) 1. and as defined in s. NR 104.02(1) (d).(4) LIMITATIONS FOR WETLANDS. Effluent temperature limitations shall be established for wetlands on a case-by-case basis to meet the water quality standards provided in ch. NR 103, but in no case shall the effluent temperature limitation be greater than 120°F.(5) LIMITATIONS FOR DISCHARGES TO STORM SEWERS.(a)General. A permittee may request, at time of permit application, an effluent limitation greater than the effluent temperature limitations required under subs. (2) to (4), (6) or (7) if the discharge is to a storm sewer or other storm water conveyance channel. The permittee may request that the higher effluent limitation be greater than 120°F if the permittee is able to demonstrate 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. An effluent temperature limitation established under this subsection shall be determined according to the following equation: Tss = Tdir + (HLV x (L/100))
Where:
Tss = Effluent temperature limitation for discharge to a storm sewer in degrees Fahrenheit dir
T = Effluent temperature limitation determined under sub. (2), (3), (4), (6) or (7) in degrees Fahrenheit
HLV = Heat loss value assumed to be 0.25 unless an alternative value is determined to be representative of site-specific conditions
L = Length (in feet) of the storm sewer or other storm water conveyance channel between the effluent discharge location and the point at which the storm sewer or storm water conveyance channel discharges to a surface water of the state.
(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. (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.(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. (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
Warm Water and Limited Forage Fish Designated Waters | Cold Water Designated Waters | Effluent Temperature Limitation |
Qs:Qe > 20:1 | Qs:Qe> 30:1 | 120°F |
20:1 >Qs:Qe > 2:1 | 30:1 > Qs:Qe > 2.5:1 | 120°F or the sub-lethal WQBEL as calculated in par. (b), whichever is lower |
Qs:Qe < 2:1 | Qs:Qe < 2.5:1 | Sub-lethal and acute WQBELs as calculated in par. (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 - T a)(Q s + (1 - f)Q e)) / Q e] + T a
Where:
WQBEL = Water quality-based effluent temperature limitation (in degrees Fahrenheit)
WQC = Water quality criteria (in degrees Fahrenheit) as defined in ss. NR 102.25 and 102.27
Ta = Ambient temperature (in degrees Fahrenheit) as determined in ss. NR 102.25 and 102.26
Qs = Receiving water flow rate equal to 1/4 7-Q 10 or 1/4 4-day, 3-year biological flow as specified in s. NR 106.53(1) (a) unless an alternative receiving water flow rate has been determined in accordance with s. NR 106.53(1) (b) to (e)
f = Fraction of the effluent flow that is with - drawn from the receiving water, where " f" ranges from 0 to 1 and is unitless
Qe = Effluent flow rate in mgd as specified in s. NR 106.53(2) (b) to (d)
(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.(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.(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.(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.(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:
WQBEL = Water quality-based effluent temperature limitation (in degrees Fahrenheit)
WQC = Water quality criteria (in degrees Fahrenheit) as defined in ss. NR 102.25 to 102.27
Ta = Ambient temperature (in degrees Fahrenheit) as determined in ss. NR 102.25 to 102.27
e-a = An empirical factor; "e" is the base of the natural logarithm and the exponent " a " is calculated as follow
a = [(A)(54.7 + B(150))] / [(8,345,000)(Qe)]
Where:
A = Area of mixing zone in square feet, as follows:
Maximum Area Allowed (square feet) | Water Body |
31,416 = | inland lake or impoundment offshore discharge |
15,708 = | inland lake or impoundment shore discharge |
15,708 = | Great Lakes harbor discharge |
3,141,593 = | Great Lakes off-shore discharge |
3,125,000 = | Great Lakes shore discharge |
The maximum area of the mixingzone is subject to all applicable portions of s. N R 102.0 5 ( 3)
B = A coefficient which is a function of Ta as follows:
Ta | B |
< 59.9 | 0.405 |
60-69.9 | 0.555 |
70-79.9 | 0.667 |
> 80 | 0.990 |
Qe = Effluent flow rate in mgd as specified in s. NR 106.53(2)
(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: (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. 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.
(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). (c) Effluent temperature limitations determined in accordance with par. (b) shall be expressed in a permit as a function of effluent flow.(d) Permits that contain flow-related effluent temperature limitations shall require daily monitoring of effluent temperature during times of discharge.(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.(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:(a) A mixing zone analysis that details the full extent and condition of the mixing zone.(b) A demonstration that such effluent temperature limitations meet all mixing zone provisions of s. NR 102.05(3).(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.(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.(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.(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).(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.Wis. Admin. Code Department of Natural Resources NR 106.55
CR 07-111: cr. Register September 2010 No. 657, eff. 10-1-10.Amended by, CR 15-085: am. Table 1 (title) Register August 2016 No. 728, eff. 9/1/2016