an agency under this subparagraph may be used only to carry out activities that would not otherwise occur within the same timeframe using discretionary funds provided in an appropriations Act. (C) Effect on application consideration In carrying out this paragraph, the Commission or an applicable agency shall ensure that the use of applicant funds under subparagraph (A) or (B) will not impact impartial decisionmaking with respect to the responsibilities of the agency, either substantively or procedurally, under this part or any other Federal law, consistent with the regulations for implementing the procedural provisions of the National Environmental Policy Act of 1969 ( 42 U.S.C. 4321 et seq. ) under parts 1500 through 1508 of title 40, Code of Federal Regulations (or successor regulations). (D) Voluntary funding Nothing in this paragraph requires or compels an applicant— (i) to fund a third-party contractor under subparagraph (A)