When developing a MACT standard for a particular source category, the EPA looks at the current level of emissions achieved by best-performing similar sources through clean processes, control devices, work practices, or other methods. These emissions levels set a baseline, often referred to as the “MACT floor” for the new standard. At a minimum, a MACT standard must achieve, throughout the industry, a level of emissions control that is at least equivalent to the MACT floor.
The EPA can establish a more stringent standard when it makes economic, environmental, and public health sense to do so.
The MACT floor differs for existing sources and new sources.
* For existing sources, the MACT floor must equal the average current emissions limitations achieved by the best-performing 12 percent of sources in the source category, if there are 30 or more existing sources.
If you believe that the EPA under Obama will limit their guidelines to that, I have a bridge to sell you.