In the following situations, the permit writer might assume that water quality criteria should be attained at the point of discharge, despite State/Tribal water quality standards that allow consideration for dilution/mixing:

• Zero stream flow (at critical low flow).
• Presence of attached aquatic life (e.g., mussels, clams).
• Certain types/classes of pollutants (e.g., bioaccumulatives).
• No remaining assimilative capacity for the pollutant.

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