The MPCA prepared assessments of water quality for Congress under section 305(b) of the Clean Water Act using 10 years of monitoring data (where available) for the following:

• dissolved oxygen
• pH
• turbidity
• un-ionized ammonia
• metals, and
• fecal coliform bacteria.

The Index of Biotic Integrity (IBI), a measure of biodiversity, was also used. In general, 10 years of water quality data were reviewed against the criteria listed below. Waterbodies were then considered for inclusion on the list of impaired waters or total maximum daily load (TMDL) list if they were assessed as impaired (partial or nonsupport) of a designated use per the 305(b) methodology.

The assessment of impairment (partial support or nonsupport) was based on monitoring, not just on survey or evaluation. A survey of local water resource managers was used in some 305b assessments, but was not sufficient alone to cause inclusion on the TMDL list. Exceedances of metals standards was not sufficient alone to cause inclusion on the TMDL list.

The MPCA does not include mercury and PCBs as reasons for including stream segments on the TMDL list. Almost all of the monitoring that the MPCA does for mercury and PCBs is in fish tissue, rather than in the water column. The concentrations in fish tissue that trigger different levels of advice in the fish consumption advisories are simply advisory levels, not legal standards such as there are for pollutants in the water column. In addition, since a high percentage of the mercury and PCB is due to airborne sources, there is no readily agreed on method, either for allocating loads to different sources or for controlling these sources.

The MPCA developed the following list of impaired waters for which total maximum daily loads for particular pollutants are to be determined.

More Information

For questions about the Red River Basin information available on this page, contact Molly MacGregor at 218-846-0494. For more information on water quality assessments, see the 305b assessments pages on this Web site.