In the past, Ohio EPA has addressed impairments at the project level. For example, if the Stillwater River basin was assessed, only impairments found in that study area would be addressed in the TMDL. However, as Ohio EPA has gone around the state and completed surveys in all of its watersheds, it has been found that many of these impairments are caused by similar sources. Being able to see these patterns of sources on a broader scale will allow us to put them into perspective and recommend reduction strategies. Covering multiple watersheds across the state will allow us to take a more wholistic approach to TMDL development and implementation and will make more efficient use of staff time and streamline TMDL development for the involved watersheds.
Although new to Ohio, the idea of addressing impairments through a multi-watershed approach has already been implemented by several states, like Kentucky and Michigan, for example. Ohio EPA is currently working on multi-watershed projects for the following impairments: bacteria, sediment, habitat, nutrients, and AMDAT. While the watersheds in these projects are from all over the state, the Agency has refrained from referring to them as “statewide” TMDLs because not all watersheds are covered under each project.