California Code, Public Contract Code - PCC § 20443

The legislative body may, by ordinance, prescribe general rules directing the superintendent of streets or the engineer, as the case may be, and the contractor as to the materials to be used, and the mode of executing the work, under all contracts thereafter made.  The assessment and apportionment of the expenses of all such work shall be made by the superintendent of streets or the engineer, as the case may be, in the mode provided by this division.