(a) The certification requirement shall be waived only if a certifying authority fails or refuses to act on a request for certification within the reasonable period of time.

(b) If the Federal agency determines that the certifying authority did not act on a request for certification within the reasonable period of time, the Federal agency shall promptly notify the certifying authority and project proponent in writing that the certification requirement has been waived in accordance with § 121.8. Such notice shall satisfy the project proponent's requirement to obtain certification.