The performance-based approach may be used by the department to establish numeric criteria based on natural conditions that are fully protective of existing and designated aquatic life uses.

(1) Aquatic life water quality criteria must be derived using the procedures referenced in ecology publication 25-10-001, "A Performance-Based Approach for Developing Site-Specific Natural Conditions Criteria for Aquatic Life in Washington".

(2) Application of the performance-based approach for establishing aquatic life water quality criteria is limited to the following listed water quality constituents:

(a) Aquatic life temperature criteria in fresh water;

(b) Aquatic life dissolved oxygen criteria in fresh water;

(c) Aquatic life pH criteria in fresh water;

(d) Aquatic life temperature criteria in marine water;

(e) Aquatic life dissolved oxygen criteria in marine water.

(3) Aquatic life water quality criteria developed using this approach are applicable to the water body upon derivation.

(4) If the requirements set forth in the performance-based approach cannot be met, then site-specific criteria can be established by following the alternatives listed at WAC 173-201A-260 (1)(a)(i).