(a) Each district plan shall be designed to achieve and maintain the state standards by the earliest practicable date, as determined by the district and subject to the approval of the state board, and in consideration of all relevant factors, including, but not limited to, the following:
(1) Present and projected maximum ambient pollutant concentration.
(2) Distribution and frequency of violations.
(3) Transport contributions.
(4) Projected emission increases based on industrial, vehicular, or population growth.
(5) Emission inventory characteristics.
(6) Anticipated effectiveness of available and potential control measures.
(7) Emission reductions occurring in, or expected to occur in, the district.
(8) In districts where military bases have closed or are scheduled for closure, the reuse plans for the closing base.
(b) Each district plan shall be based upon a determination by the district board that the plan is a cost-effective strategy to achieve attainment of the state standards by the earliest practicable date.