Colo. Rev. Stat. § 29-8-107
At the time that action is commenced under section 29-8-106, or at any time prior to the time of the hearing provided for in section 29-8-112, and if requested by the governing body or public utility, a bond shall be filed, with security approved by the governing body or cash deposit made sufficient to pay all expenses of the governing body connected with the proceedings and of the public utilities for actual time and expenses incurred in regard to the cost and feasibility study in case the organization of the district is not effected. If at any time during the organization proceedings the governing body is satisfied that the bond first executed or the amount of cash deposited is insufficient in amount, it, on its own initiative or at the request of a public utility, may require the execution of an additional bond or the deposit of additional cash within a time to be fixed, not less than ten days distant, and upon failure of the petitioners to file or deposit the same, the petition shall be dismissed.
C.R.S. § 29-8-107