Section 106.09. Whole effluent toxicity data evaluation and limitations.

 

(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.

(2)   Acute whole effluent toxicity.

(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) .

(b) To assure compliance with par. (a) , a whole effluent toxicity test may not result in a statistically valid LC 50 less than 100% with the following taxa-specific exposure periods:

1. 48 hours for aquatic invertebrate organisms (including Ceriodaphnia dubia) ;

2. 96 hours for aquatic vertebrate organisms (including fathead minnows ( Pimephales promelas ));

3. Any other exposure period deemed appropriate by the department for a specific test organism.

(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 LC 50 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) .

(d) If, in the judgment of the department, the statistical interpretation methods used to test for LC 50 are not appropriate for a specific data set, empirical interpretation methods may be used to determine the significance of an effect.

(e) Acute whole effluent toxicity limits shall be expressed as 1.0 TU a 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 TU a 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.

(f) Whole effluent acute toxicity limitations shall be expressed in permits as daily maximum limitations.

(3)   Chronic whole effluent toxicity.

(a) The department shall establish chronic whole effluent toxicity limitations to ensure that concentrations of substances are not discharged from a point source that alone or in combination with other materials present are toxic to fish or other aquatic life as required by s. NR 102.04 (4) (d) .

(b) To assure compliance with par. (a) , an effluent, after dilution with an appropriate allowable quantity of receiving water flow equivalent to that provided by receiving water flows specified in s. NR 106.06 (3) (c) or implied in s. NR 106.06 (3) (b) 2. , may not cause a significant adverse effect to a test organism population when compared to an appropriate control, as determined by applying all of the following:

1. Using statistical interpretation methods appropriate to the toxicity test protocol, an adverse effect will be determined to be significant if the statistically derived IC25 or IC50, as specified for each species in the whole effluent toxicity test methods required in s. NR 219.04 , Table A, from the whole effluent toxicity test, is less than the calculated IWC.

2. If, in the judgment of the department, the statistical interpretation methods used to test for significance are not appropriate for a specific data set, empirical interpretation methods may be used to determine the significance of an effect.

(c) Chronic whole effluent toxicity limits shall be expressed as a value that is 100 divided by the IWC. Compliance with a chronic whole effluent toxicity water quality-based limitation shall be determined by comparing the monthly average calculated TUc from all toxicity tests conducted during that month to the limitation. Pursuant to s. NR 106.08 (6) (d) , a calculated IC25 or IC50 that exceeds 100% is set equal to zero.

(d) Whole effluent chronic toxicity limitations shall be expressed in permits as monthly average limitations.

Cr. Register, February, 1989, No. 398 , eff. 3-1-89; renum. (1) (a), (b), (c) (intro.) and 2. and (2) to be (2) (a) to (c) and (3) and am. (2) (b), (c), (3) (a), (b) (intro.) and 1., r. (1) (c) 1., cr. (1), Register, August, 1997, No. 500 , eff. 9-1-96; CR 03-050 : am. (2) (b) (intro.) Register February 2004 No. 578 , eff. 3-1-04; CR 04-101 : am. (1) Register May 2005 No. 593 , eff. 6-1-05; CR 15-085 : r. and recr. (2) (e), cr. (2) (f), am. (3) (b) (intro.), 1. , r. and recr. (3) (c), cr. (3) (d) Register August 2016 No. 728 , eff. 9-1-16.

Note

A toxicity reduction evaluation study is not always required in the event an acute WET limit is imposed in a permit. Microsoft Windows NT 6.1.7601 Service Pack 1 A toxicity reduction evaluation study is not always required in the event a chronic WET limit is imposed in a permit. Microsoft Windows NT 6.1.7601 Service Pack 1