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Step 7: Toxics Best Available Control Technology (TBACT) and Toxics Lowest Achievable Emission Rate (TLAER) and Risk Reduction

TBACT is an emissions limitation which is based on the maximum degree of control that can be achieved and applies to existing facilities, as defined by Cleaner Air Oregon [OAR 340-245-0020(20)]. TBACT may be based on a design standard, equipment standard, work practice standard or other operational standard, or a combination thereof. When TBACT is required the facility must provide a feasibility analysis consisting of the following components [OAR 340-245-0220(3)(a)]:
  • What has been achieved in practice for sources in the same class, or processes or emissions similar to the source under review
  • Energy, health, and environmental impacts not related to air quality
  • Economic impacts and cost-effectiveness strictly related to controlling Toxic Air Contaminant (TAC) emissions
TLAER is an emissions limitation, similar to TBACT, which applies to new facilities in the Cleaner Air Oregon program. The major difference from TBACT is that TLAER must provide the maximum degree of reduction technically feasible without regard to energy impacts, health and environmental impacts, or economic impacts. [OAR 340-245-0220(4)(a)] When TLAER is required it is not considered achievable if the cost of control is so great that a new facility could not be built; however, if another facility in the same industry, or with similar processes or emissions, uses that control technology, then such use demonstrates that the cost to industry of that control is not prohibitive. [OAR 340-245-0220(4)(b)]

​​There are different Risk Action Levels (RALs) for new and existing facilities [OAR 340-245-8010 Table 1]; TBACT/TLAER is required when a facility's risk assessment demonstrates that the following RALs are exceeded:
  • Existing facilities:
    • Excess Cancer Risk of 50 per million
    • Hazard Index of 5
  • New Facilities:
    • Excess Cancer Risk of 10 per million
    • Hazard Index of 1
In order for an existing or new facility to operate at risk levels in exceedance of the RALs above, all Toxics Emissions Units (TEUs) must have either TBACT or TLAER, respectively.

​Case-by-case determinations are made for both TBACT and TLAER analyses. DEQ is currently developing guidance on how to prepare these submittals as well as criteria DEQ will use for making determinations. In general for a TBACT analysis, DEQ will consider cost analyses on a risk basis rather than a mass basis. This approach differs from the conventional BACT analyses as required by the federal New Source Review (NSR) permitting regulations and Prevention of Significant Deterioration (PSD) requirements, which are typically analyzed on a cost per ton pollutant reduction.

​TBACT determinations are required for all TEUs when the risk assessment results for an existing facility demonstrate risk levels in exceedance of the TBACT RALs shown above; however, some of these TEUs may qualify for exemption from further emissions controls if they meet the following criteria and are determined to meet “Presumptive TBACT" [OAR 340-245-0220(2)]:
  • The existing TEU is in compliance with emission control requirements, work practices or limitations established by a major source National Emission Standard for Hazardous Air Pollutants (NESHAP) adopted by the Environmental Protection Agency (EPA) after 1993 and before April 10, 2018, provided that:
    • The emission control requirements, work practices or limitations result in an actual reduction to the emissions of hazardous pollutants (HAPs) regulated under the NESHAP
    • There are no other toxic air contaminants (TACs) emitted by the source that are not controlled by the NESHAP and that materially contribute to public health risk
  • An existing TEU is subject to and complies with the Colored Art Glass Manufacturing rules OAR 340-244-9000 through OAR 340-244-9090 or OAR 340-245-9000 through OAR 340-245-9090

​DEQ will require periodic TBACT/TLAER reviews be submitted in order to ensure that the current maximum emission controls are being met. The requirements for these reviews are outlined in OAR 340-245-0220(5)(b)&(c). The process for determining if TBACT/TLAER at your facility is currently sufficient or will require updates is outlined in OAR 340-245-0220(5)(d).

Cleaner Air Oregon frequently asked questions for facilities 

The frequently asked questions (FAQs) on this page are provided to answer common questions about completing air toxics risk assessments for the Cleaner Air Oregon program, and ensure consistency across assessments. As the Cleaner Air Oregon process evolves, DEQ will update this page with common questions or unique scenarios. If there is a question you would like to see answered or have feedback on a response below, please contact us at

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