Colo. Rev. Stat. § 32-22-107
With the approval of each county or municipality having jurisdiction over the area of such a district, the district may establish a station area improvement district to finance the construction, operation, or maintenance of a station for a passenger rail system. A station area improvement district may consist only of all or a portion of the area within a two-mile radius of the station to be funded by the station area improvement district, and the general assembly finds that the area within a two-mile radius of a passenger rail station, or any portion of such an area that the board may designate as a station area improvement district, is an area that will be especially benefited by the construction, operation, or maintenance of such a station. The board shall not establish a station area improvement district unless it receives a petition signed by the owners of property that will bear a majority of the proposed assessments and by a petition signed by the lesser of a majority of the registered electorate in the proposed station area improvement district or one thousand registered electors in the proposed station area improvement district. The method of creating a station area improvement district, making improvements, assessing the costs of improvements made against property, and levying a sales tax shall be as provided in part 6 of article 20 of title 30; except that the board shall perform the duties of the board of county commissioners under said part 6 and the improvements shall be limited to the construction, operation, or maintenance of a passenger rail station.
C.R.S. § 32-22-107