Water Quality Standards Rules (Recap continued)

• WQ criteria must support DUs.
• WQ criteria must be based on science, not economics or social impacts.
• “States” may use EPA’s WQC, but not required if a scientific rationale for alternative is provided.
• May have spatial and/or temporal waivers of WQC (and DUs).
• WQS must not preclude ability to meet downstream WQS.