Cal. Gov. Code § 26230
As a means of implementing a county underground utility ordinance adopted to remove existing overhead utility lines and to require property owners served by the lines, to prepare their properties to accept underground utility lines, counties may provide by ordinance that if any property owner, after due notice, refuses to comply within a reasonable time to effect the removal or preparation in accordance with the applicable rules of the utility involved the county may cause the work to be done and assess the costs of the work against the property and that the assessment shall become a lien against the property. The assessment may be collected at the same time and in the same manner as ordinary county ad valorem taxes are collected, and shall be subject to the same penalties and the same procedure and sale in case of delinquency as provided for these taxes. All laws applicable to the levy, collection, and enforcement of county ad valorem taxes shall be applicable to the assessment.
Ca. Gov. Code § 26230