Cal. Sts. & Hy. Code § 5397
If the superintendent of streets is authorized by ordinance to collect the assessments, the ordinance shall also provide that the superintendent of streets shall furnish to the contractor or his assigns a good and sufficient surety bond conditioned upon the full and prompt payment by the superintendent of streets to the contractor or his assigns of all assessments so collected by him. The bond shall be in an amount not less than 10 percent of the total amount of the assessment shown on the assessment roll if such total amount does not exceed two hundred fifty thousand dollars ($250,000) and shall be in the amount of twenty-five thousand dollars ($25,000) if the total amount of the assessments shown on the assessment roll exceeds the sum of two hundred fifty thousand dollars ($250,000). The premium on the bond shall be payable as a part of the incidental expenses of the proceeding.
As an alternative the legislative body, in its discretion, may provide in such ordinance that a blanket surety bond shall be maintained on file in the office of the city clerk, conditioned as above, in amounts herein provided. Such blanket bond shall cover and protect all contractors and their assigns holding warrants for assessments which the superintendent of streets is authorized to collect. The premium on such blanket bond may be prorated to the several special assessment proceedings as a part of the incidental expenses of such proceedings.
As a further alternative, the legislative body, in its discretion, may provide in such ordinance that the official bond of the superintendent of streets shall guarantee the full and prompt payment by the superintendent of streets to the contractor or his assigns of all assessments collected by him.
Ca. Sts. and High. Code § 5397