California Code, Public Contract Code - PCC § 20102

Notwithstanding any other provision of this part to the contrary, where plans and specifications have been prepared by a public agency, whose activities are subject to this part, in order for a public project to be put out for formal or informal bid, and, subsequently, the public agency elects to perform the work by day's labor, the public agency shall perform the work in strict accordance with these same plans and specifications.

Revisions of the plans and specifications may be made once a justification detailing the specific reasons for the change or changes has been approved by the public agency or its project director and a copy of the change and its justification is placed in the project file.