1. (a) An effluent discharged to a water may not impart chronic toxicity to aquatic organisms, expressed as 1.0 chronic toxic unit, at the point of discharge, or if the department authorizes a mixing zone in a permit, approval, or certification, at or beyond the mixing zone boundary, based on the minimum effluent dilution achieved in the mixing zone. If the department determines that an effluent has reasonable potential to cause or contribute to exceedance of the whole effluent toxicity limit, the department will require whole effluent toxicity testing as a condition of a permit, approval, or certification. The permittee shall use methods and species approved by the United States Environmental Protection Agency in Short-term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to Freshwater Organisms, 4th edition (2002), Technical Report No. EPA-821-R-02-013, adopted by reference, and Short-term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to West Coast Marine and Estuarine Organisms 1st edition (August 1995), Technical Report No. EPA/600/R-95/136, adopted by reference, or alternate methods and species approved by the department that provide equivalent estimates of chronic toxicity. The department will require that the testing use sensitive and biologically important life stages of indigenous species, as the department considers necessary and feasible to protect aquatic life fully. The department will reduce the frequency of, or eliminate, whole effluent toxicity testing if

   1. (1) the results of a sufficient database of testing conclusively demonstrate that an effluent does not have a reasonable potential to exceed the whole effluent toxicity limit;
   2. (2) significant changes in effluent quality are not expected over the life of the permit; and
   3. (3) the department determines that aquatic life will be adequately protected.
2. (b) In this section, "chronic toxic unit" means an expression of the chronic toxicity of an effluent, determined as (100/NOEC), where NOEC, the "No Observed Effects Concentration", is the highest tested percentage concentration of an effluent, established by direct testing of toxicity to aquatic organisms, that causes no observable adverse effects, including effects on growth, development, behavior, reproduction, or survival, over a test duration that generally is one-tenth or more of the lifespan of the test organism. Other equivalent chronic toxicity endpoints approved by the department, such as the "25 percent Inhibition Concentration (IC25)," may be used in place of NOEC, and may incorporate shorter test durations.

(Eff. 11/1/97, Register 143; am 4/29/99, Register 150; am 6/13/2006, Register 178)

Authority: AS 46.03.020, AS 46.03.050, AS 46.03.070, AS 46.03.080