In establishing criteria:

1. (1) Establish numerical criteria values based on:

   1. (A) 304(a) Guidance; or
   2. (B) 304(a) Guidance modified to reflect site conditions (i.e., Water Effects Ratio); or
   3. (C) Other scientifically defensible methods.
2. (2) Establish narrative criteria or criteria based upon biomonitoring methods where numerical criteria cannot be established or to supplement numerical criteria.