Cal. Pub. Cont. Code § 20409

The board of supervisors may authorize such road commissioner to employ such workmen and purchase such materials, equipment, tools, and appliances and cause such work to be done as is necessary to construct or maintain such bridges and to keep them in repair without adopting plans and specifications, or working details and without advertising for bids as required in Sections 20402, 20403, and 20404. The cost of such construction, maintenance or repair shall be paid out of the county road funds or out of the county general fund.