40 CFR §124.17

1. (a)(Applicable to State programs, see 40 CFR 123.25 (NPDES), 145.11 (UIC), and 271.14 (RCRA).)At the time that any final permit decision is issued under § 124.15, the Director shall issue a response to comments. States are only required to issue a response to comments when a final permit is issued. This response shall:
   1. (1)Specify which provisions, if any, of the draft permit have been changed in the final permit decision, and the reasons for the change; and
   2. (2)Briefly describe and respond to all significant comments on the draft permit raised during the public comment period, or during any hearing.
2. (b)For EPA-issued permits, any documents cited in the response to comments shall be included in the administrative record for the final permit decision as defined in § 124.18. If new points are raised or new material supplied during the public comment period, EPA may document its response to those matters by adding new materials to the administrative record.