Cal. Health and Safety Code § 41514.8

(a) Prior to adopting rules or regulations which would affect the operation of existing powerplants, the state board or any district shall consider and adopt written findings that specify the supporting information relied upon with regard to all of the following: (1) The need for the emission reductions expected to be achieved from the implementation of the proposed rule or regulation, and the extent to which the rule or regulation is necessary solely for the attainment of a state ambient air quality standard. (2) The relative cost of achieving the emission reductions from the proposed rule or regulation compared to the cost of feasible reductions from sources other than powerplants. (3) The availability and technological feasibility of control technologies required by the proposed rule or regulation. (b) Rules and regulations affecting the operation of existing powerplants adopted after January 1, 1982 by the state board or any district shall take into consideration the findings under subdivision (a).