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Impaired Waters and TMDLs

The Impaired Waters Restoration Pipeline: Water Quality Improvements

Following TMDL implementation, expectations are high for an impaired water’s condition to begin to change. The improving stage in the impaired waters restoration pipeline is characterized by first allowing time for the implemented pollution control practices to take effect, and second by monitoring to detect improvements. As with tracking implementation, tracking improvements in tens of thousands of waters is an expensive and formidable task that has not been possible for states and EPA alone to carry out on all recovering waters.

Where monitoring data are available, changes can be documented and reported. Partial, but significant, changes may occur, but remain short of full water quality standard attainment. For example, incremental improvement may occur when a water body with multiple pollutants is no longer impaired by one or more of its former problems. Also, monitoring aquatic measures of condition may show significant improvement in a specific chemical or physical parameter, or an improved biological community measure.

The TMDL program analysis focused on approaches for detecting improving conditions and identifying driving factors that are associated with improvements. A waterbody remains on the 303(d) list until it is fully recovered and meets water quality standards.

Reports and Resources