general provisions: MACT Determinations - analysis

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The purpose of this section is to provide state, local agencies and sources of hazardous air pollutants with example methods for establishing case-by-case Maximum Achievable Control Technology (MACT).  As with any guidance, this information does not impose legally binding requirements for either the permitting authority or an owner/operator, but presents a possible process.

This information is based on Guidelines for MACT Determinations under Section 112(j) Requirements[PDF] and 40 CFR Part 63, Subpart B.

The MACT Determination/Analysis

The process of determining an equivalent MACT emission limitation is called a MACT determination.  In order to make sure that emissions standards for major sources are implemented in a timely manner, Congress added a "hammer" provision to the air toxics title of the Clean Air Act Amendments of 1990.  This means that if EPA misses a MACT standard promulgation deadline by more than 18 months, then the states or designated permitting authorities are required to establish MACT standards for the affected sources on a case-by-case basis.  Affected sources are required to submit an application for a MACT determination so that the permitting authority can establish source specific MACT limits.  Limits established by a case-by-case determination must be comparable to the emission limits or requirements that would likely be imposed if an emission standard been promulgated for that source category.

For most source categories, the process by which the permitting authority determines the appropriate limits and level of control will involve a number of different determinations.  First, the emission points at the major source that are related to the activities and equipment in a source category or subcategory must be identified. There may be a number of emitting activities and equipment at a single major source. The entire process will require on-going communication and exchange of information between the permitting authority and the applicant. 

Overview of the MACT Analysis Process

Because of the variety of situations that could arise, the MACT analysis has been divided into three tiers. The figures below show the steps for Tier I, Tier II and Tier III of the analysis within two scenarios.  A MACT floor finding by the permitting authority is made during Tier I.  During Tier II, the permitting authority, in consultation with the applicant, evaluates all commercially available and demonstrated controls that are reasonably applicable to such source.  Tier III uses the information developed in Tier I or Tier II to establish a MACT emission limitation.

  

The MACT Analysis Scenario I Tier I – Making A MACT Floor Finding (Permitting Authority) Identify the MACT Emission unit Make a MACT floor finding: If floor can be determined Tier III – Identifying MACT Identify maximum emission reduction control technology Conduct an impact analysis Establish the MACT emission limitation

         

The MACT Analysis Scenario II Tier I – Making A MACT Floor Finding (Permitting Authority) Identify the MACT emission unit Make a MACT floor finding: If floor cannot be determined Tier II – Considering All Control Technologies List all available/reasonable applicable control technologies Eliminated technologically infeasible control technologies Determine efficiency of applicable control technologies    Tier III – Identifying MACT Identify maximum emission reduction control technology Conduct an impact analysis Establish the MACT emission limitation

If a MACT floor is determined, it is only necessary to complete Tier I and Tier III of the MACT analysis. This analysis compares the costs, non-air quality health and environmental impacts and energy requirements associated with using control technologies that obtain a level of HAP emission reductions that are equal to or greater than the MACT floor. A key assumption is that the Tier I analysis yields sufficient information to conduct the Tier III MACT analysis.

If, under Tier I, the MACT floor cannot be determined or is equal to "no control," Tier II of the analysis should be completed before moving on to Tier III. The purpose of Tier II is to identify all commercially available and demonstrated control technologies that are reasonably applicable to such source. Available control technologies include but are not limited to: reducing the volume of, or eliminating emissions of pollutants through process changes, substitution of materials or other techniques; enclosing systems or processes to eliminate emissions; collecting, capturing, or treating pollutants when released from a process, stack, storage, or fugitive emission point; using design, equipment, work practices, or operational standards (including requirements for operator training or certification); or, a combination of any of these methods.

Once a list of control technologies that are reasonably applicable to the source is developed, each control technology should be evaluated to consider the costs, non-air quality health and environmental impacts, and energy requirements associated with using each control technology. In Tier III, the control technology(s) achieving the maximum degree of HAP emission reductions taking into consideration the costs of achieving such emission reductions and the non-air quality health and environmental impacts and energy requirements should be selected as MACT. Once MACT has been selected, a MACT emission limitation(s) should be established by the permitting authority based on the degree of emission reductions that can be achieved through the application of the maximum achievable control technology (MACT). A design, equipment, work practice or operational standard, or combination thereof, may be designated as the MACT emission limitation, if it is not practicable, in the judgment of the permitting authority, to prescribe or enforce a numerical MACT emission limitation.

If an owner or operator wishes to comply with the MACT emission limitation using a control strategy other than the control strategy selected as MACT, then the Title V permit application should be submitted or revised to demonstrate that this alternative strategy achieves the required level of emission reductions.