40 CFR §51.262

1. (a)Any compliance schedule or revision of it extending over a period of more than one year from the date of its adoption by the State agency must provide for legally enforceable increments of progress toward compliance by each affected source or category of sources. The increments of progress must include—
   1. (1)Each increment of progress specified in § 51.100(q); and
   2. (2)Additional increments of progress as may be necessary to permit close and effective supervision of progress toward timely compliance.
2. (b)[Reserved]