Pub. Resources Code, § 21165

(a) When a project is to be carried out or approved by two or more public agencies, the determination of whether the project may have a significant effect on the environment shall be made by the lead agency, and that agency shall prepare, or cause to be prepared by contract, the environmental impact report for the project, if a report is required by this division. In the event that a dispute arises as to which is the lead agency, any of the disputing public agencies, or in the case of a project described in subdivision (c) of Section 21065 the applicant for such project, may submit the question to the Office of Planning and Research, and the Office of Planning and Research shall designate, within 21 days of receiving the request, the lead agency, giving due consideration to the capacity of that agency to adequately fulfill the requirements of this division.

(b) For the purposes of this section, a “dispute” means a contested, active difference of opinion between two or more public agencies as to which of those agencies shall prepare any necessary environmental document. A dispute exists where each of those agencies claims that it either has or does not have the obligation to prepare that environmental document. The Office of Planning and Research shall not designate a lead agency in the absence of such a dispute.