Cal. Sts. & Hy. Code § 5130
Before ordering any work to be done under this division the legislative body shall require, except as provided hereunder, the engineer to furnish it with plans and specifications therefor together with careful estimates of the costs and expenses of such work.
In a county having a population of 4,000,000 or over an owner or owners of lots or lands liable to be assessed for work may engage a registered civil engineer, registered pursuant to Chapter 7, Division 3 of the Business and Professions Code, to prepare the plans for any work to be done under this division. The legislative body may purchase said plans for use in proceedings under this division and may establish rules, regulations and procedures to be followed by registered civil engineers engaged by owners in preparing plans, submitting them to and obtaining their approval by the engineer and for the time, manner and determination of the amount to be paid for such plans; provided, however, that the amount paid for plans shall not exceed 8% of the engineer's estimate of the cost of work shown on the plans and that no payment shall be made for any plans which have not been approved by the engineer. The amount paid for any plans and any fee required to be paid, pursuant to the aforesaid rules and regulations, may be paid out of the city treasury and shall be charged against the district as an incidental expense.
Ca. Sts. and High. Code § 5130