Cal. Sts. & Hy. Code § 740.4
The department shall transmit a copy of such map insofar as it relates to the land within a county to the planning commission of the county.
The planning commission of such county shall thereafter prepare a precise plan showing such planned right-of-way in conformity with Section 65600 of the Government Code, and the board of supervisors shall thereafter adopt such precise plan in the manner provided in Article 11 (commencing with Section 65600), Chapter 3, Title 7 of the Government Code.
Thereafter, the planning commission shall also notify the department of any application for a building permit for a building costing five thousand dollars ($5,000) or more in sufficient time to give the department an opportunity to purchase the right-of-way from such applicant. Upon adoption of a resolution by the board of supervisors, the notice to the department may be given by any other officer, board, commission, or department designated for that purpose by the resolution.
Ca. Sts. and High. Code § 740.4