---
kind: "section"
citation: "40 C.F.R. § 51.919"
title: "40"
number: "51.919"
heading: "Applicability."
url: "https://uscodex.org/cfr/40/51.919"
---

# §51.919. Applicability.


As of April 6, 2015, the provisions of [subpart AA](/cfr/40/subpartAA.md) shall replace the provisions of [subpart X](/cfr/40/subpartX.md), [§§ 51.900 to 51.918](/cfr/40/51.900..51.918.md), which will cease to apply, with the exception of the attainment date extension provisions of [§ 51.907](/cfr/40/51.907.md) for the anti-backsliding purposes of [§ 51.1105(d)(2)](/cfr/40/51.1105.md?p=d-2).


## Notes

### Amendments

[80 FR 12312, Mar. 6, 2015]

### Source

Source: 69 FR 23996, Apr. 30, 2004, unless otherwise noted.

### Authority

Authority: 23 U.S.C. 101; 42 U.S.C. 7401-7671q.

### Source

Source: 36 FR 22398, Nov. 25, 1971, unless otherwise noted.

### Amendments

[80 FR 12312, Mar. 6, 2015]