Cal. Sts. & High. Code § 5721

If the legislative body of a county appoints an engineer of work in accordance with Article 2 of this chapter, it may provide that the work shall be done under his direction and to his satisfaction and that the materials used shall comply with the specifications and be to the satisfaction of such engineer of work and it may provide that the engineer of work shall make and sign the assessment. The contract shall nevertheless be entered into with the county surveyor, and the assessment and warrant when confirmed shall be recorded in the office of the county surveyor.