Colo. Rev. Stat. § 32-14-113
The district shall make every reasonable effort to obtain funding for a target amount of at least fifty percent of the total costs incurred by the district in the acquisition of a stadium site and in the construction of a stadium from moneys acquired from sources other than the levy and collection of the sales tax authorized pursuant to the provisions of section 32-14-114. Such amount constitutes a target which the district shall attempt to achieve but is not a mandatory requirement. Such moneys may include, but are not limited to, private donations or the revenues acquired by the issuance of special obligation bonds to be paid from the financial incentives specified in section 32-14-110(1)(a) or the operating revenues generated by the district. The sales tax authorized in section 32-14-114 shall be levied only for the period of time for which it is necessary to generate revenues sufficient to pay the percentage of the total costs incurred in said acquisition and construction not funded by other sources of money and for such other purposes specified in section 32-14-115, but such period of time shall not exceed twenty years.
C.R.S. § 32-14-113