California Code, Streets and Highways Code - SHC § 5132.05

(a) If the proceedings include any acquisition and the actual cost of the acquisition as finally determined is less than the amount included in the assessment as the cost of the acquisition, the excess may be spent as the legislative body may thereafter determine, either for the maintenance or repair of the work or improvement, or the excess shall be refunded or credited in proportion to the amount of the assessments that were levied for the acquisition cost, as follows:

(b) If the legislative body determines that the excess shall be used for maintenance or repair, the legislative body shall establish a separate fund of the excess and shall use it solely for that purpose.