Total Maximum Daily Load TMDL Studies

February 20, 2012

Total Maximum Daily Load Assessements

A TMDL, or Total Maximum Daily Load, can refer to both a numeric water quality criteria, as well as a process by which such criteria are calculated. Considerable regulatory attention is currently being directed toward TMDL development at both the state and federal level. Despite the tremendous progress in cleaning up the nation’s waterways since the Clean Water Act was enacted in 1972, a significant number of the nations waterways are not in attainment with applicable water use designations. The TMDL process is seen by USEPA and the states as a mechanism for bringing these waterways into attainment. In general, a TMDL establishes the maximum amount of a pollutant a water body can assimilate without exceeding the applicable water quality standard.

The TMDL process uses many diagnostic and regulatory tools that have been in use for many years such as chemistry and biota monitoring, modeling, and wasteload allocation. These tools are used and TMDLs are developed for specific stream segments that are in non-attainment of one or more criteria (i.e., chemical, biological). Where the TMDL process differs from past approaches is that it goes well beyond municipal and industrial point source discharges when evaluating causes of impairment and possible solutions. By design, the TMDL process looks at the full range of contributing factors including non-point source pollution, storm water runoff, sediment contamination, agricultural inputs and land use patterns. Public participation is an important component in the development of most TMDLs because many of the most important causative factors for non-attainment are often outside of the direct control of the environmental agencies charged with water quality management.

Please contact the water quality professionals at EnviroScience for more information on how we can provide support for TMDL projects of any size.