Colo. Rev. Stat. § 37-43-153
Such contract and the proceedings taken by any such district pursuant thereto and in connection with the authorization and issue of refunding bonds, in case the indebtedness of such district is reduced by the issuance of such refunding bonds, may include provisions whereby the board of directors of said district covenants and agrees on behalf of said district to levy and collect assessments in excess of the amounts which would meet the principal of and the interest on said bonds as the same fall due if all such assessments were paid in full, in order to create and maintain a reserve fund to insure the prompt payment of the principal of and interest on said bonds; but such covenants and agreements shall never provide for assessments in amounts greater than such assessment would have been had such indebtedness of such district not been so reduced. Said provisions and covenants, when included in the proceedings adopted by the board of directors of any such district, shall inure to the holders of said refunding bonds.
C.R.S. § 37-43-153