Cal. Sts. & High. Code § 5702

The engineer of work may be an individual, joint venture, copartnership or corporation. If the engineer of work employed be an individual, he shall make and sign any certificate or document required to be made or signed by the engineer of work. If the engineer of work employed be a joint venture, copartnership or corporation, the legislative body, either by contract of employment or by resolution, shall designate a member of the joint venture, a partner, an officer of the corporation, or an authorized agent of any of the foregoing to make and sign any certificate or document required to be made or signed by the engineer of work.