Cal. Sts. & High. Code § 5580

The legislative body, instead of waiting until the completion of the work may, in its discretion, and not otherwise, upon the completion of two blocks or more of any work, order the street superintendent to make an assessment for the proportionate amount of the contract completed, and thereupon proceedings and rights of collection of that assessment shall be the same as provided in this part for the making and collection of other assessments.