(a) If your municipal waste combustion unit is located in a State that has a State plan that has not been approved by the EPA or has not become effective, then this subpart applies and the State plan would not apply to your municipal waste combustion unit. However, the State could enforce the requirements of a State regulation while your municipal waste combustion unit is still subject to this subpart.

(b) After the State plan is approved by the EPA and becomes effective, your municipal waste combustion unit is no longer subject to this subpart and will only be subject to the approved and effective State plan.