The provisions of this subchapter shall apply only to bridges over navigable waters of the United States, the construction of which is approved after August 2, 1946 , under the provisions of this subchapter; and the provisions of the first proviso of section 401 of this title , and the provisions of sections 491 to 494 and 495 to 498 of this title, shall not apply to such bridges. (Aug. 2, 1946, ch. 753, title V, § 507, 60 Stat. 849 .) CFR Title Parts 33 114