5 Colo. Code Regs. § 1002-21.18
The publication of a final TMDL in the Water Quality Information Bulletin constitutes the Division's determination on the final TMDL. Any 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 publication of a final TMDL in the Water Quality Information Bulletin. If no such appeal is timely filed, the Division may submit the final TMDL to EPA. If an appeal is timely filed, it shall be heard by the Commission in accordance with section 105 of the APA and section 21.4 of this regulation, except that notice of any adjudicatory hearing shall also be provided to all dischargers with Waste Load Allocations in the TMDL and to the proponent of a third-party TMDL. The Division will not submit the final TMDL to EPA until at least 30 days after the Commission's decision regarding any appeal becomes final. The filing and disposition of an appeal to the Commission is a prerequisite to the right of judicial review pursuant to the APA.
5 CCR 1002-21.18