TMDLs for these waterbodies will be developed by the year 2000. For each TMDL parameter, IDEM must identify and quantify the probable sources and allocate allowable loadings from the contributing point and nonpoint sources in the watershed so that the water quality standards are attained. For example, potential sources of E. coli include combined sewer overflows, improperly functioning septic systems, and agricultural runoff from livestock. These sources must be quantified through stream monitoring, with diffusion and degradation of the pollutant accounted for as it travels down the stream using computer model simulations. Finally, various pollutant load reduction scenarios are to be modeled to compare their relative cost-effectiveness.
Public meetings are to be held to discuss the various alternatives for reducing the total loading.
One scenario might include a waste treatment plant assisting agricultural producers in the watershed to implement best management practices to reduce overall loading as a more cost-effective alternative than constructing a new sewage treatment plan. Determine Whether the Water Quality Now Meets Standards Throughout the TMDL process, monitoring is a crucial element of water quality-based decision making. Water quality monitoring provides data for the evaluation of whether the TMDL and prescribed control actions protect or improve the environment. Some question whether it is within the scope of EPA's authority to apply TMDLs to agriculture under the language of the Clean Water Act. EPA, however, is proceeding under the assumption that TMDLs do apply.