On December 27, 1996, the Agency published a rule in the Federal Register implementing certain provisions in section 112(g) of the Clean Air Act (Act). After the effective date of that rule, all owners or operators of major sources of hazardous air pollutants (HAP) that are constructed or reconstructed are required to install maximum achievable control technology (MACT) (unless specifically exempted), provided they are located in a State with an approved title V permit program. When no applicable Federal emission limitation has been promulgated under section 112(d) of the Act, the Act requires the permitting authority (generally a State or local agency responsible for the program) to determine a MACT emission limitation on a case-by-case basis. If the permitting authority has not yet established procedures for requiring MACT on constructed or reconstructed major sources by the required date, the rule provides that the EPA Regional Administrator will determine MACT emission limitations on a case-by-case basis for a period of up to one year. This action amends the rule governing constructed or reconstructed major sources--by providing a longer time period (up to 30 months) during which the EPA Regional Administrator may determine MACT emission limitations on a case-by-case basis--if the permitting authority has not yet established procedures for requiring MACT on constructed or reconstructed major sources. This action is needed in order to ensure that major sources can obtain MACT determinations required for construction or reconstruction in those jurisdictions where permitting authorities require extra time to establish procedures to implement the section 112(g) rule.