One of the goals of Regulation XIII is to ensure that any emission increase of nonattainment air contaminants from the operation of any relocated source or from the operation of any new or modified source does not impede the progress of attaining National Ambient Air Quality Standards (NAAQS) or State Ambient Air Quality Standards (SAAQS). To accomplish this goal, District Rule 1303 (PDF)(b)(2) gives the Executive Officer the authority to deny permits to construct for these permit sources unless BACT is employed, and the applicant provides emission offsets to mitigate any emission increase.
An emission offset is that which is acquired either from emission reduction credits (ERCs) or from allocations from the Priority Reserve. Offset ratios are 1.2-to-1.0 for ERCs and 1.0-to-1.0 for allocations from the Priority Reserve, except for facilities not located in the South Coast Air Basin (SOCAB), where the offset ratio for ERCs is 1.2-to-1.0 for VOC, NOx, SOx, and PM10, and 1.0-to-1.0 for CO.