site remediation mact summary

11. What is meant by the phrase" once in, always in" and why is it important to this MACT rule?

The “once in, always in” policy is that once a facility or source is subject to a MACT standard, it remains subject to that standard as long as the affected source definition or criteria are met. Because of the uniqueness of the site remediation source category, EPA specifically evaluated how the final site remediation MACT rule could be implemented within the framework of existing policies for implemented MAXT standards promulgated under the the Clean Air Act, Section 112, including this particular policy.

An area source that conducts a site remediation, can become a major source due to the remediation activity (because the activity can increase the PTE (potential to emit) to levels that exceed the major source thresholds). Under this policy, a facility would remain subject to the NESHAP that was triggered by the limited duration change of source status from area to major brought about by the increase in the PTE from the site remediation activity. In this situation, "the once in, always in" policy would create a disincentive for facilities  to engage in site remediations (particularly voluntary remediations). 

It is not EPA's intent to adopt requirements that create incentives to avoid a cleanup or result in the selection of less desirable or less protective remediation approaches.  Therefore, EPA has determined that this policy does not apply where a facility's status changes from an area source to a major source, solely as a result of remediation activity regulated by the Site Remediation MACT, where the facility returns to area source status after the cleanup activity.