40 CFR §124.211

1. (a)“Routine changes” are any changes to the standardized permit that qualify as a class 1 permit modification (without prior Agency approval) under 40 CFR 270.42, appendix I, and
2. (b)“Routine changes with prior Agency approval” are for those changes to the standardized permit that would qualify as a class 1 modification with prior agency approval, or a class 2 permit modification under 40 CFR 270.42, appendix I; and
3. (c)“Significant changes” are any changes to the standardized permit that:
   1. (1)Qualify as a class 3 permit modification under 40 CFR 270.42, appendix I;
   2. (2)Are not explicitly identified in 40 CFR 270.42, appendix I; or
   3. (3)Amend any terms or conditions in the supplemental portion of your standardized permit.