(a) This part is effective March 6, 2017. Certification plans approved by EPA before the effective date remain approved except as provided in §§ 171.5(b)-(d) and 171.309.

(b) Status of certification plans approved before effective date. A certification plan approved by EPA before March 6, 2017 remains approved until March 4, 2020, except as provided in paragraph (c) of this section and § 171.309.

(c) Extension of an existing plan during EPA review of proposed revisions. If by March 4, 2020, a certifying authority has submitted to EPA a proposed modification of its certification plan pursuant to subpart D of this part, its certification plan approved by EPA before March 6, 2017 will remain in effect until EPA has approved or rejected the modified plan pursuant to § 171.309(a)(4) or November 4, 2022, whichever is earlier, except as provided in paragraph (d) of this section and § 171.309(b).

(d) Extension of an existing plan after EPA has approved a revised plan. Where EPA has approved a certifying authority's modified certification plan pursuant to § 171.309(a)(4), the certification plan approved by EPA before March 6, 2017 shall remain in effect as specified in EPA's approval of the modified certification plan.

(e) States, Tribes, or Federal agencies that do not have an EPA-approved certification plan in effect may submit to EPA for review and approval a certification plan that meets or exceeds all of the applicable requirements of this part any time.