California Code, Government Code - GOV § 4004

Prior to the commencement of the public work, the engineer shall prepare and file in his office either full, complete and accurate plans and specifications or a work authorization approved by the engineer describing the work to be performed, and an estimate of the cost thereof, except where other and adequate provision is made by law requiring the preparation and filing of such plans, specifications and estimates of cost by some other officer or in some other office.