California Code, Health and Safety Code - HSC § 40925.5

(a) A district which is nonattainment for the state ozone standard shall be designated “nonattainment-transitional” by operation of law if, during a single calendar year, the state standard is not exceeded more than three times at any monitoring location within the district.

(b) Any district which is designated nonattainment-transitional under subdivision (a) shall review its plan for attaining the state ozone standard and shall determine whether the stationary source control measures scheduled for adoption or implementation within the next three years by the district are needed to accomplish expeditious attainment or to maintain the state standard following the projected attainment date. In making that determination, the district shall consider air quality trends, the effect of the state's adopted and proposed motor vehicle and area source control programs, turnover of the vehicle fleet, the impact of measures previously adopted by the district, the state board, and the Environmental Protection Agency which are in the process of being implemented, and other significant factors influencing emissions trends.

(c) If a nonattainment-transitional district determines that one or more of the stationary source control measures scheduled for adoption or implementation within the next three years are no longer necessary to accomplish expeditious attainment or to maintain the state standard, the district shall shift those measures to the contingency category.

(d) If a nonattainment-transitional district determines that delaying one or more stationary source control measures will not retard the achievement of the state ozone standard, it may delay that measure.

(e) Subdivisions (c) and (d) shall not apply to any stationary source control measures required by Section 39610. In addition, subdivisions (c) and (d) shall be suspended at any time that the district ceases to qualify for a nonattainment-transitional designation under subdivision (a).

(f) Actions of any district pursuant to this section are effective immediately. The state board may disapprove any action of the district pursuant to this section within 90 days of the action. The state board shall not disapprove district actions pursuant to this section unless it finds that the actions will delay expeditious attainment of the state ozone standard.Actions taken by the state board pursuant to this subdivision are subject to Section 41503.4.

(g) Actions of any district pursuant to subdivisions (c) or (d) shall be reviewed by the district in connection with its next review and revision of its attainment plan pursuant to Section 40925.