BACT Background


South Coast AQMD published its first BACT Guidelines in May 1983, and a major revision in October 1988. On September 8, 1995, the South Coast AQMD Governing Board adopted new policies and procedures that established the Scientific Review Committee and updated cost-effectiveness procedures. On December 11, 1998, the Governing Board approved: (1) a new format for listing BACT determinations; and (2) a revised process for updating South Coast AQMD BACT Guidelines that complies with federal and state laws. On October 20, 2000, the Governing Board approved revisions to the New Source Review regulations that: 1) maintained the federal Lowest Achievable Emission Rate (LAER) requirement for major polluting facilities; and 2) established a minor source BACT (MSBACT) for non-major polluting facilities that will consider cost before making MSBACT more stringent.

The BACT Guidelines for major polluting facilities include:

  • Part A: Policy and Procedures for Major Polluting facilities, and

  • Part B: LAER/BACT Determinations for Major Polluting Facilities.

The BACT Guidelines for non-major polluting facilities include:

  • Part C: Policy and Procedures for Non-Major Polluting Facilities, and

  • Part D: BACT Guidelines for Non-Major Polluting Facilities.

For the December 2016 amendment to the Guidelines, additional parts were added to address Prevention of Significant Deterioration (PSD) requirements for greenhouse gas (GHG) emissions established by U.S. EPA in 40 CFR 52.21 in 2011. The requirements are incorporated by reference in South Coast AQMD Rule 1714.

The BACT Guidelines for GHG requirements include:

  • Part E: Policy and Procedures for Facilities Subject to Prevention of Significant Deterioration for Greenhouse Gases; and

  • Part F: BACT Determinations for Facilities Subject to Prevention of Significant Deterioration for Greenhouse Gases.

The BACT Guidelines explain what BACT is, why it is required, and how it is determined for both major and non-major polluting sources. In addition, Part B of the guidelines provides detailed information on technologies contained in permits issued by South Coast AQMD and in permits or guidelines issued by other agencies, as well as other technologies not yet been qualified as BACT/LAER. Part D details BACT requirements for more than 100 different categories of equipment.


Major polluting facilities that are subject to NSR are required by the Clean Air Act to have the Lowest Achievable Emission Rate (LAER). LAER is determined through the BACT process at the time the permit is issued, with little regard for cost, and pursuant to USEPA’s LAER policy as to what is achieved in practice. South Coast AQMD permitting staff will determine BACT for any new, modified or relocated source at a major polluting facility on a case-by-case basis.  This LAER/BACT determination will be in accordance with Part A of the BACT Guidelines, and will consider information from Part B of the current BACT Guidelines and any other relevant information available to South Coast AQMD.


For non-major polluting facilities, BACT will be determined in accordance with state law (H&SC Section 40440.11) at the time an application is deemed complete unless a more stringent rule requirement becomes applicable prior to permit issuance. For the most part, it will be as specified in Part D of the BACT Guidelines.  Exceptions may be made based on special permitting considerations discussed in Part C of the BACT Guidelines.

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