Section NR 106.53 - Parameters used to establish water quality-based effluent limitations for temperature(1) RECEIVING WATER FLOW RATE (QS). The value of receiving water flow rate (Qs) used to determine effluent limitations for discharges to flowing waters shall be as follows: (a) Qs shall equal 1/4 of the average minimum 7-day flow which occurs once in 10 years (1/4 7-day Q10) or, if sufficient information is available to calculate a biologically based receiving water design flow, 1/4 of the flow which prevents an excursion from the applicable water quality criteria using a duration of 4 days and a frequency of less than once every 3 years (1/4 4-day, 3-year biological flow).(b) Qs may be reduced from those values calculated in par. (a) wherever natural receiving water flow is significantly altered by flow regulation or other types of water diversion structures.(c) The discharger shall be allowed to demonstrate, through appropriate and reasonable methods that an adequate passageway for movement of aquatic life exists in the cross-section of the receiving water or that dilution is accomplished rapidly such that the extent of the mixing zone is minimized. In complex situations, the department may require that the demonstration under this paragraph include water quality modeling or field dispersion studies.(d) Based upon the results of a demonstration submitted under par. (c), Qs may be modified from that specified in par. (a) or (b). A modified Qs shall be determined on a case-by-case basis and shall be approved in writing by the department. Qs may not exceed the larger of the 7-day Q10 or the 4-day, 3-year biologically based design flow, except when a permit allows the use of real-time data for the determination of water quality based effluent limitations for temperature, as provided in s. NR 106.54(4).(e) The value of Qs may not exceed that of par. (a) if the department determines that the discharge has a potential to jeopardize the continued existence of any endangered or threatened species listed under ch. NR 27 or section of the federal Endangered Species Act,.(2) EFFLUENT FLOW RATE (Qe). The value of effluent flow rate (Qe) used to determine effluent temperature limitations shall be as follows: (a)Flow ratios. For purposes of determining a flow ratio pursuant to s. NR 106.55(6) (a), Qe shall equal: 1. For discharges subject to ch. NR 210 and which discharge for 24 hours per day on a year-round basis, Qe shall equal the maximum effluent flow, expressed as a daily average, that is anticipated to occur for 12 continuous months during the design life of the treatment facility unless it is demonstrated to the department that such a design flow rate is not representative of projected flows at the facility.2. For all other dischargers not subject to ch. NR 210, Qe shall equal the maximum effluent flow, expressed as a daily average, that has occurred for 12 continuous months and represents normal operations.3. For seasonal discharges, discharges proportional to stream flow, or other unusual discharge, Qe shall be determined on a case-by-case basis.(b)Acute temperature limitation. For purposes of determining acute temperature limitations pursuant to s. NR 106.55(6) (b), Qea shall be the highest daily maximum effluent flow rate, expressed as mgd, which has occurred for each calendar month of the year and represents normal operating conditions.(c)Sub-lethal temperature limitation. For purposes of determining sub-lethal temperature limitations pursuant to s. NR 106.55(6) (a), (Qesl) shall be the highest 7-day rolling average effluent flow rate within a calendar month, expressed as mgd, which has occurred for each calendar month of the year and represents normal operating conditions.(d)Non-typical effluent flows. For purposes of determining effluent temperature limitations pursuant to s. NR 106.55(6) (a) and (7), Qea and Qesl may be determined on a case-by-case basis for seasonal discharges, discharges proportional to stream flow, or other unusual discharge situations.Wis. Admin. Code Department of Natural Resources NR 106.53
CR 07-111: cr. Register September 2010 No. 657, eff. 10-1-10.