Except to the extent that they are less stringent than the Texas Water Code or the rules of the commission, 40 Code of Federal Regulations (CFR), Subchapter N, Parts 400 - 471, except 40 CFR Part 403, which are in effect as of the date of the Texas Pollutant Discharge Elimination System program authorization, as amended, and Parts 437 (Federal Register, Volume 65, December 22, 2000), 442 (Federal Register, Volume 65, August 14, 2000), 444 (Federal Register, Volume 65, January 27, 2000), 445 (Federal Register, Volume 65, January 19, 2000), and 450 (Federal Register, Volume 74, December 1, 2009), as amended, are adopted by reference.