Colo. Rev. Stat. § 29-8-136
Upon completion of the conversion contemplated by this article, the public utility shall present the governing body with its verified bill for conversion costs, as computed under section 29-8-131, but based upon the actual cost of constructing the underground facility rather than the estimated cost of the facility. In no event shall the bill for conversion cost presented by the public utility exceed the amount of estimated conversion costs by the public utility. In the event the conversion costs are less than the estimated conversion costs, each owner within the improvement district shall receive the benefit, prorated in such form and at such time as the governing body determines. The bill of the public utility shall be paid within thirty days by the governing body from the improvement district funds or such other source as is properly designated by the governing body. In determining the actual cost of constructing the underground facility, the public utility shall use its standard accounting procedures, such as the uniform system of accounts as defined by the federal communications commission and as is in use at the time of the conversion by the public utility involved, as described in section 29-8-131.
C.R.S. § 29-8-136