45CSR27 Best Available Technology (BAT)

45CSR27, "To Prevent and Control the Emissions of Toxics Air Pollutants", addresses 14 compounds recognized as "Toxic Air Pollutants" (TAPs) that are emitted by certain types of sources. All 14 TAPs are also included in EPA's list of HAPs. A list of TAPs can be found in the rule at Table A of 45CSR27, or "45CSR27 Toxic Air Pollutants", which also includes synonyms for the TAPs. The scope and purpose of 45CSR27 is to prevent and control the discharge of TAPs from "chemical processing units" by requiring the application of Best Available Technology (BAT), a standard specified in the rule. Table A of 45CSR27 sets a plantwide de minimus level for each TAP, including fugitive emissions. If plantwide emissions of a particular TAP exceed the de minimus level, then a case-by-case review of emissions is performed to ensure these meet the state standard known as BAT.

For the purposes of 45CSR27, a "chemical processing unit" that may be subject to the rule has been defined fairly broadly. Such a unit can include an assembly of reactors, tanks, distillation columns, heat exchangers, vaporizers, compressors, dryers, decanters, and/or other equipment used to treat, store, manufacture, or use TAPs. For the purpose of 45CSR27, a "chemical processing unit" also includes surface coating equipment or similar equipment using a TAP as a solvent or for other purposes, but does not include equipment used in the production and distribution of petroleum products providing that such equipment does not produce or contact materials containing more than 5% benzene by weight. Fugitive emissions, wastewater from "chemical processing units," railcar and tank truck loading and unloading, are also subject to BAT standards.

BAT is an emissions limit requiring the application of the maximum degree of reduction and control which the Director, on a case-by-case basis, determines is achievable for each toxic air pollutant which would be emitted from any stack, pipe, air pollution control device, or from any other equipment or facilities associated with a chemical processing unit.

In the case of "chemical processing units" constructed or modified after the June 30, 1990, effective date of this rule, BAT shall not be less stringent than the most stringent emissions level that is achieved in practice by similar sources or processes. For existing "chemical processing units," BAT may be less stringent than requirements for new or modified units. For all facilities, BAT shall represent the maximum degree of emission reduction that the Director determines is achievable taking into consideration the cost of achieving such emission reduction, and public health and environmental impacts. All BAT programs shall fully consider the additive or cumulative health and environmental impacts of multiple pollutant and multiple unit emissions. No BAT proposal shall be approvable that represents a level of control less stringent than any requirement for a "chemical processing unit" under 40 CFR 61 and 40 CFR 60. The DAQ typically uses a "top-down" approach to determine BAT.

The chart, "45CSR27 - Best Available Technology (BAT) for Toxics Air Pollutants (TAPs) - Applicability Determination" is designed to illustrate the major steps in determining applicability to 45CSR27 and BAT, as well as briefly describe the "Top-Down" process used to determine BAT.