If such State legislative action is required, the State program may be approved without regard to whether or not the requirements referred to in paragraphs (1), (2), (3), and (5) of subsection (a) are less stringent than the corresponding standards under
section 6991b(a) of this title during the two-year period commencing on the date of promulgation of regulations under
section 6991b(a) of this title (and during an additional one-year period after such legislative action if regulations are required to be promulgated by the State pursuant to such legislative action).