Basic Course: Supplemental Topics (NPDES Permit 13)

Characterizing the Effluent & Receiving Water: Identify Pollutants of Concern

State/Tribal authorities typically identify a pollutant of concern as any pollutant that falls into one of the following categories:

• Pollutants with an applicable technology-based effluent limit (TBEL). Thus, if the permit writer has already developed a TBEL for a particular pollutant, then he/she has to consider the pollutant a “concern” and determine whether the TBEL is sufficiently protective of water quality.
• Pollutants with a WLA from a TMDL or watershed analysis. Thus, if the total maximum daily load (TMDL) developers assigned a waste load allocation (WLA ) to a point source, then clearly it is of “concern” and the permit writer must ensure that the TMDL WLA is implemented through the NPDES permit.
• Pollutants identified as needing WQBELs in the previous permit. Thus, if this is a permit reissuance, the permit writer should reassess the need for water quality-based effluent limits for any pollutants that were regulated in the current permit.
• Pollutants identified as present in the effluent through monitoring. Thus, if the permit application or other effluent data indicate that a pollutant is present, then the permit writer should assess whether that pollutant could adversely affect water quality.
• Pollutants that are otherwise expected to be present in the discharge. In some cases, the permit writer may not have effluent data available (e.g., a new facility proposing to discharge). The permit writer may be able to establish that a pollutant is likely to be present in the effluent, based solely on the nature of the operation.