Colo. Rev. Stat. § 37-41-146
The board of directors, if it deems it not for the best interest of the district that the lands mentioned in the petition, or some portion thereof, should be excluded from said district, shall order that said petition be denied; but if it deems it for the best interest of the district that the lands mentioned in the petition, or some portion thereof, be excluded from the district and if there are no outstanding bonds of the district, then the board may order the lands mentioned in the petition, or some defined portion thereof, to be excluded from the district. However, if, within thirty days from the making of such order, a majority of the qualified electors of the district protest in writing to said board against the exclusion of such lands from said district, said order shall be held for naught, and such lands shall not be excluded therefrom. In case a contract has been made between the district and the United States, no change shall be made in the boundaries of the district unless the secretary of the interior shall assent thereto in writing and such assent is filed with the board of directors. Upon such assent, any lands excluded from the district shall be discharged from all liens in favor of the United States under contract with the United States or under bonds deposited with its agents.
C.R.S. § 37-41-146