Colo. Rev. Stat. § 30-20-613
Failure to pay the whole assessment within said period of thirty days shall be conclusively considered and held to be an election on the part of all persons interested, whether under disability or otherwise, to pay in such installments. All persons so electing to pay in installments shall be conclusively held and considered as consenting to said improvements. Such election shall be conclusively held and considered as a waiver of any right to question the power or jurisdiction of the county to construct the improvements, the quality of the work, the regularity or sufficiency of the proceedings, the validity or the correctness of the assessments, or the validity of the lien thereof; except that, with respect to local improvements authorized in section 30-20-603 (11.5), the owner for each property included in the district shall retain all rights otherwise existing by contract or by law against parties other than the county with respect to the financed energy efficiency improvement or renewable energy improvement.
C.R.S. § 30-20-613
This section was originally numbered as § 30-20-612 in C.R.S. 1973 but was renumbered on revision in the 1977 replacement volume for ease of location.