Rule 3745-1-44 | Whole effluent toxicity provisions.
[Comment: For dates of non-regulatory government publications, publications of recognized organizations and associations, federal rules and federal statutory provisions referenced in this rule, see rule 3745-1-03 of the Administrative Code.]
[Comment: See rule 3745-2-09 of the Administrative Code for whole effluent toxicity water quality based effluent limit calculation procedures.]
(A) Protection of aquatic life - whole effluent approach.
(1) An acute toxicity level of 0.3 acute units (TUa) shall apply outside the mixing zone to limited resource water, warmwater, exceptional warmwater, coldwater, seasonal salmonid, and modified warmwater habitat use designations in accordance with this chapter and the following equation:
TUa = 100/LC50
LC50 = the median lethal concentration as defined in rule 3745-2-02 of the Administrative Code.
(2) A chronic toxicity level of 1.0 chronic toxic units (TUc) shall apply outside the mixing zone to warmwater, exceptional warmwater, coldwater, seasonal salmonid, and modified warmwater habitat use designations, where:
TUc = 100/IC25 for all chronic endpoints, except that:
TUc = 100/(geometric mean of NOEC and LOEC) for survival or mortality endpoints using daphnid species when this is more restrictive than the TUc value resulting from the definition based on IC25.
(B) The chronic toxicity level does not apply to limited resource water use designations.
(C) For undesignated waters, an acute toxicity level of 0.3 TUa and a chronic toxicty level of 1.0 TUc shall apply outside of the mixing zone.
(D) Acute toxicity within the mixing zone shall be regulated by paragraph (B) of 3745-33-07 of the Administrative Code.