Permittees should closely analyze air permitting implications for complex and phased projects. For example, if an application is made for a new process line to replace an existing process line, and the two lines will be operated simultaneously for a period of time to allow for commissioning and troubleshooting of the new equipment, then carefully crafted permit conditions need to be inserted into the air permit to address such. Unless that is done, the default assumption of the air permit is that there will be no simultaneous operation allowed.
In the air permit, such considerations will take the form of alternate operating scenarios and permit conditions to address each operating scenario. "Transition period" permitting can be challenging, but must be taken into account to avoid potential violations. Alternate permitting scenarios may look something like the following:
- Scenario A: Existing equipment operation only. New equipment under construction.
- Scenario B: Existing equipment and new equipment temporarily in simultaneous operation until new equipment becomes fully operational. (This could require a permit condition limiting total production rates of existing and new equipment combined.)
- Scenario C: New equipment only in operation. Existing equipment permanently retired.