Health & Saf. Code, § 40930

(a) Each district that has adopted a plan pursuant to this chapter shall, on or before January 31 of each year, prepare and submit to the state board a report identifying the number of days during the preceding calendar year that air quality in the district violated each state ambient air quality standard for which the district’s status is nonattainment.

(b) For any pollutant for which the report indicates that the applicable state ambient air quality standard was not violated during more than three days during the calendar year at any one or more monitoring locations within the district, the district shall not adopt any new or more stringent control measure until after preparation, and approval by the district board, of an analysis that does all of the following:

(1) Assesses the costs and benefits of all additional district, state, and federal regulatory actions that would be necessary to achieve attainment of the applicable state ambient air quality standard, taking into account only the additional costs and benefits attributable to achieving the state standard for the remaining three or fewer days each year.

(2) Includes consideration of all of the socioeconomic impacts specified in Section 40728.5.

(3) Identifies, if the district is an upwind district, the benefits of the additional regulatory actions in the district on the air quality in any downwind district, and identifies the costs attributable to those regulatory actions.

(c) The state board shall review the district analyses prepared pursuant to subdivision (b) to ensure expeditious progress towards attainment in both the district that prepared the analysis and any downwind district and to ensure that any resulting action of the district that prepared the analysis does not adversely affect any downwind district.