Table 4 — Reasonable Potential Multiplication Factor
NR 106.08(6)(d)(d) Maximum toxicity values. The department shall set the TUc effluent and TUa effluent values in par. (b) equal to zero whenever toxicity is not detected or the LC50, IC25, or IC50 equals or exceeds 100% effluent. NR 106.08(6)(e)(e) Exception. WET limits are not necessary under this subsection when the department determines chemical-specific limits for the effluent are sufficient to attain and maintain applicable numeric and narrative water quality standards, taking into consideration all of the following: NR 106.08(6)(e)2.2. Controls on the pollutant discharged by nonpoint source pollution in the watershed. NR 106.08(6)(e)3.3. The variability of the pollutant or parameter in the effluent discharged. NR 106.08(6)(e)4.4. Sensitivity of species to toxicity testing when evaluating whole effluent toxicity as defined in s. NR 106.03. NR 106.08(6)(f)(f) Fact sheet. If the department determines WET limitations are not necessary under par. (e), all of the factors that are required for the determination must be specifically discussed in the fact sheet for the permit. NR 106.08(7)(7) Data Exclusions. The department may exclude data from a WET reasonable potential determination when those data meet any of the following conditions: NR 106.08(7)(b)(b) Positive WET results are caused by deficiency toxicity only. NR 106.08(7)(c)(c) Positive WET results are caused by groundwater or surface water remediation needed to correct or prevent an existing surface or groundwater contamination situation or a public health problem. NR 106.08 HistoryHistory: Cr. Register, February, 1989, No. 398, eff. 3-1-89; am. (1), r. and recr. (5), Register, August, 1997, No. 500, eff. 9-1-97; CR 09-123: am. (5) (a) Register July 2010 No. 655, eff. 8-1-10; correction in (4) made under s. 13.92 (4) (b) 7., Stats., Register July 2010 No. 655; CR 15-085: r. and recr. Register August 2016 No. 728, eff. 9-1-16; CR 17-002: cr. (6) (e), (f) Register April 2018 No. 748, eff. 5-1-18. NR 106.09NR 106.09 Whole effluent toxicity data evaluation and limitations. NR 106.09(1)(1) Data evaluation. Data evaluation procedures are specified in the whole effluent toxicity test methods specified in s. NR 219.04, Table A. In the event of a WET test failure, facility specific requirements shall be established in the WPDES permit which specify required follow-up actions. NR 106.09(2)(a)(a) Except as provided in par. (c), the department shall establish acute whole effluent toxicity limitations to ensure that substances shall not be present in amounts which are acutely harmful to aquatic life in all surface waters including the mixing zone and effluent channel as required by s. NR 102.04 (1). NR 106.09(2)(b)(b) To assure compliance with par. (a), a whole effluent toxicity test may not result in a statistically valid LC50 less than 100% with the following taxa-specific exposure periods: NR 106.09(2)(b)1.1. 48 hours for aquatic invertebrate organisms (including Ceriodaphnia dubia); NR 106.09(2)(b)2.2. 96 hours for aquatic vertebrate organisms (including fathead minnows (Pimephales promelas)); NR 106.09(2)(b)3.3. Any other exposure period deemed appropriate by the department for a specific test organism. NR 106.09(2)(c)(c) If a zone of initial dilution is determined appropriate in accordance with the provisions of s. NR 106.06 (3) (c), whole effluent acute toxicity limitations determined by this subsection shall be adjusted such that the effluent meets the following condition. The adjustment shall insure that after dilution of the effluent with the receiving water at a concentration equal to 3.3 times the percent dilution value calculated through application of the zone of initial dilution, the test solution of effluent and receiving water shall not produce a statistically valid LC50 less than 3.3 times the percent dilution value determined through application of the zone of initial dilution with the exposure periods as provided in par. (b). NR 106.09(2)(d)(d) If, in the judgment of the department, the statistical interpretation methods used to test for LC50 are not appropriate for a specific data set, empirical interpretation methods may be used to determine the significance of an effect. NR 106.09(2)(e)(e) Acute whole effluent toxicity limits shall be expressed as 1.0 TUa unless an AMZ is approved in which case these limits shall be expressed as a value that is 100 divided by the AMZ. Compliance with an acute whole effluent toxicity water quality-based limitation shall be determined by comparing the TUa endpoint from each toxicity test to the limitation. Pursuant to s. NR 106.08 (6) (d) a calculated LC50 that exceeds 100% is set equal to zero. NR 106.09 NoteNote: A toxicity reduction evaluation study is not always required in the event an acute WET limit is imposed in a permit.
NR 106.09(2)(f)(f) Whole effluent acute toxicity limitations shall be expressed in permits as daily maximum limitations.
