Colo. Rev. Stat. § 43-1-216
All notices to landowners referred to in this part 2 may be given by mailing the same to such landowners. All tenders of payment of damages to landowners referred to in this part 2 may be made by mailing to each landowner to whom such tender is to be made a written or printed statement reciting the action of the chief engineer and of the commission relating to the award of damages to such landowner, specifying the amount of damages awarded to him, and stating where and by whom payment of the sum so awarded will be made upon demand of such landowner. Depositing in the general post office in the city of Denver or at the county seat of the county in which the land in controversy is located a written or printed copy of any notice referred to in this section, or any statement tendering payment of damages, signed by the proper officer, enclosed in a sealed envelope with proper postage prepaid, and properly addressed to the landowner at his last known place of residence or address, is sufficient mailing of the same for the purpose of this part 2.
C.R.S. § 43-1-216