What requirements may be added to individual VPDES permits as a result of TMDLs?
Federal and state regulations require effluent limits to be “consistent with the assumptions and requirements of any available waste load allocation prepared by the State and approved by EPA pursuant to” the federal TMDL regulations. For bacteria TMDLs, the WLA is calculated as the maximum permitted bacteria concentration multiplied by a maximum annual design flow. Functioning wastewater treatment plants typically do not contribute to bacteria pollution in streams. However, if a treatment plant is considering an expansion, that expansion would result in increased loading due to increased discharge and would not meet the TMDL’s WLA. Therefore, the TMDL would have to be re-opened and a new WLA calculated.
