40 CFR §60.5575a

1. (a)This subpart can be implemented and enforced by the EPA, or a delegated authority such as your state, local, or Tribal agency. If the Administrator has delegated authority to your state, local, or Tribal agency, then that agency (as well as the EPA) has the authority to implement and enforce this subpart. You should contact your EPA Regional Office to find out if this subpart is delegated to your state, local, or Tribal agency.
2. (b)In delegating implementation and enforcement authority of this subpart to a state, local, or Tribal agency, the Administrator retains the authorities listed in paragraphs (b)(1) through (5) of this section and does not transfer them to the state, local, or Tribal agency. In addition, the EPA retains oversight of this subpart and can take enforcement actions, as appropriate.
   1. (1)Approval of alternatives to the emission standards.
   2. (2)Approval of major alternatives to test methods.
   3. (3)Approval of major alternatives to monitoring.
   4. (4)Approval of major alternatives to recordkeeping and reporting.
   5. (5)Performance test and data reduction waivers under § 60.8(b).