If- | Then- | Unless or until- | In which case- |
(1) A State or authorized Tribe has adopted a water quality standard that is effective under State or Tribal law and has been submitted to EPA before May 30, 2000 . . | . . . the State or Tribe's water quality standard is the applicable water quality standard for purposes of the Act . . | . . . EPA has promulgated a more stringent water quality standard for the State or Tribe that is in effect . . | . . . the EPA-promulgated water quality standard is the applicable water quality standard for purposes of the Act until EPA withdraws the Federal water quality standard. |
(2) A State or authorized Tribe adopts a water quality standard that goes into effect under State or Tribal law on or after May 30, 2000 . . | . . . once EPA approves that water quality standard, it becomes the applicable water quality standard for purposes of the Act . . | . . . EPA has promulgated a more stringent water quality standard for the State or Tribe that is in effect . . | . . . the EPA promulgated water quality standard is the applicable water quality standard for purposes of the Act until EPA withdraws the Federal water quality standard. |
40 C.F.R. §131.21