Colo. Rev. Stat. § 30-20-601
Except as otherwise provided in this part 6, any county in this state may construct any of the local improvements mentioned in this part 6 and fund such improvements by assessing the cost thereof, wholly or in part, upon the property especially benefited by such improvements or, for the funding of improvements authorized by section 30-20-603(1)(a), (1) (a.5), and (1)(c), by imposing a sales tax throughout the district or by utilizing a combination of such assessments and tax. The improvements shall be authorized by resolution duly adopted and shall be constructed under the direction of the county engineer or other officer having similar duties or under the direction of the board in accordance with plans and specifications adopted by the board.
C.R.S. § 30-20-601