Colo. Rev. Stat. § 37-44-138
After adopting a plan for the construction of reservoirs and works for the protection of life and property and to furnish water for the irrigation of the territory embraced within the boundaries of the internal improvement district, or to drain lands within or without the boundaries of said district, the board of directors shall give notice, by publication thereof, not less than twenty days in a newspaper published in the county in which the office of the internal improvement district is located, provided a newspaper is published therein, and in such other newspapers as it may deem advisable, calling for bids for the construction of said works or any portion thereof. If less than the whole work is advertised, then the portion so advertised must be particularly described in such notice. The notice shall set forth that plans and specifications may be seen at the office of the board and that the board shall receive sealed proposals therefor and that the contract will be let to the lowest responsible bidder, stating the time and place for opening the proposals, which bids at said time and place shall be opened in public. As soon as convenient thereafter, the board shall let said work, either in portions or as a whole, to the lowest responsible bidder, or it may reject any or all bids and readvertise for proposals, or may proceed to construct the work under its own superintendence. Contracts for the purchase of materials shall be awarded to the lowest responsible bidder. The person to whom a contract may be awarded shall enter into a bond, with good and sufficient sureties, to be approved by the board, payable to said district for its use, for not less than ten percent of the amount of said contract, conditioned for the faithful performance of said contract. The work shall be done under the direction and to the satisfaction of the engineer in charge and shall be approved by the board.
C.R.S. § 37-44-138