The department of ecology and the local boards may implement an emission credits banking program. For the purposes of this section, an emission credits banking program means a program whereby an air contaminant source which reduces emissions of a given air contaminant by an amount greater than that required by applicable law, regulation, or order is granted credit for a given amount, which credit shall be administered by a credit bank operated by the appropriate agency. The amount of the credit shall be determined by the department or local board with jurisdiction, but it shall be less than the amount of the emissions reduction. The credit may be used, traded, sold, or otherwise expended for purposes established by regulation of state or local agencies consistent with the provisions of the prevention of significant deterioration program under RCW 70A.15.6240, the bubble program under RCW 70A.15.2240, and the new source review program under RCW 70A.15.2210, if there will be no net adverse impact on air quality.