(1) In accordance with RCW 90.48.520 and 40 C.F.R. 122.44(e), the department shall evaluate all applications for an NPDES permit to determine whether the applicant is applying all known, available, and reasonable methods of prevention, control, and treatment of toxicants.

(2) The department may place the whole effluent toxicity performance standard for acute toxicity into permits as a limit on a case-by-case basis pursuant to 40 C.F.R. § 125.3 (d)(3).

(a) In determining compliance with an acute whole effluent toxicity limit based on the performance standard, a minimum of three toxicity tests shall be used in calculating the median.

(b) For the first two toxicity tests conducted to determine compliance with the performance standard-based acute whole effluent toxicity limit, compliance shall be determined as a minimum of sixty-five percent survival in one hundred percent effluent.

(3) The department may establish performance-based limits for whole effluent toxicity for an entire category of dischargers. Any such limit applied to an entire category of dischargers shall be accomplished by rule making.