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Colorado Department of Public Health and Environment

Total Maximum Daily Loads

TMDL Development

For a Water Quality Limited stream segment that requires a TMDL, the State must quantify the pollutant sources and allocate allowable loads to the contributing sources, both point and nonpoint, so that water quality standards can be attained for that segment. TMDL development is a rational method for weighing the competing pollution interests and developing an integrated pollution reduction strategy for point and nonpoint sources. TMDL development includes these five basic steps: 1) select the pollutant to consider, 2) estimate the water body assimilative capacity, 3) identify the contribution of that pollutant from all significant sources, 4) analyzes information to determine the total allowable pollutant load, 5) allocate (with a margin of safety), the allowable pollution among the sources so that water quality standards can be achieved. The complexity of the TMDL development is determined by water body, the sources and the pollutant being considered. While not all segments and TMDL's require complex computer modeling, some do.

Implementation of Controls

Implementation of the TMDL is the final step. it requires participation form all the stake holders as TMDL's are not self implementing. The Waste Load Allocation portion of the TMDL can be implemented through effluent limits in discharge permits. In the case of non-point sources, voluntary controls or locally enacted controls are necessary to implement the Load Allocations. The State must rely on authority already granted by the Clean Water Act to implement TMDL's.

TMDLs by Basin

 


Your opinion is important to us. If you have comments regarding this information, or wish to have additional information included, please e-mail us at comments.wqcd@state.co.us