5 Colo. Code Regs. § 1002-21.10
Decisions by the Division with respect to 401 certifications as authorized by section 302(1)(f) of the Act may be appealed to the Commission by any person adversely affected or aggrieved by any such decision. The appeal shall be made in writing to the office of the Administrator of the Commission and must be postmarked no later than 30 days after the date of mailing of the Water Quality Information Bulletin sent to those persons on the mailing list maintained by the Division pursuant to section 25-8-302(1)(e), C.R.S. Such appeals shall be heard in accordance with section 105 of the APA and section 21.4 of this regulation. The filing and disposition of any such appeal is a prerequisite to the right of judicial review pursuant to the APA.
5 CCR 1002-21.10