(a) Except to the extent that they are less stringent than the Texas Water Code or the rules of the commission, the following federal regulations are adopted by reference, as amended:(1) 40 Code of Federal Regulations (CFR) Parts 400 - 402, 404 - 434, 436, 438 - 440, 443, 446 - 448, and 451 - 471, which are in effect as of the date of the Texas Pollutant Discharge Elimination System (TPDES) program authorization; (2) 40 CFR Part 435 (which is in effect as of the date of the TPDES program authorization for discharges subject to this part), except where 40 CFR Part 435 uses the term "produced water" the commission shall instead use the term "produced wastewater"; (3) 40 CFR Part 437 (Federal Register, Volume 68, December 22, 2003); (4) 40 CFR Part 441 (Federal Register, Volume 82, June 14, 2017); (5) 40 CFR Part 442 (Federal Register, Volume 65, August 14, 2000); (6) 40 CFR Part 444 Federal Register, Volume 65, January 27, 2000);(7) 40 CFR Part 445 Federal Register, Volume 65, January 19, 2000);(8) 40 CFR Part 449Federal Register, Volume 77, May 16, 2012); and (9) 40 CFR Part 450 Federal Register, Volume 79, March 6, 2014).(b) For the purposes of the commission's implementation of Texas Water Code, §26.131, "produced water" is defined as all wastewater associated with oil and gas exploration, development, and production activities, except hydrostatic test water and gas plant effluent, that is discharged into water in the state, including waste streams regulated by 40 CFR Part 435.