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IDEM Proposes Changes to Stack Testing Rules


By Jennifer Thompson, Attorney, Bingham Greenebaum Doll LLP

The Indiana Department of Environmental Management (“IDEM”) has public noticed proposed changes to the stack testing requirements of 326 IAC 3-6 as part of its Second Notice of Comment Period for Amendments to Rules Concerning Compliance Monitoring, LSA # 05-330 (“proposed rule”). The proposed rule also includes amendments to rules concerning continuous monitoring requirements, fuel sampling and analysis procedures, and certain sulfur dioxide compliance requirements.

The current stack testing requirements found at 326 IAC 3-6-3 require that emission tests be conducted: (1) while the unit being tested is operating at ninety-five percent (95%) to one hundred percent (100%) of its permitted operating capacity; (2) under conditions representative of normal operations; or (3) under other capacities or conditions as approved by IDEM. “Capacity” is defined as the design capacity of the unit or other operating capacity agreed to by the source and IDEM.

The proposed amendments to 326 IAC 3-6-3 would change these requirements and would instead require tests be conducted: (1) while operating at a minimum of ninety-five percent (95%) of the permitted maximum emissions unit’s operating capacity description; (2) under conditions of worst case emissions; or (3) under other capacities or conditions as specified in an applicable requirement or approved by IDEM. The amendments also would require that all test runs for a given pollutant be conducted within twenty-four (24) hours unless process variables or mandatory test lengths of greater than two hours make this impracticable, then the testing must be conducted on consecutive days, with other periods or durations to be approved by IDEM. Additionally, if the owner or operator does not know what its worst case emissions would be, the proposed rule at 326 IAC 3-6-3(b)(1) assumes the worst case emissions to be the maximum process or operating rate of the emissions unit as listed in the permit’s emissions unit description.

Therefore, the proposed rule changes not only the conditions under which a stack test must be conducted but limits the timeframe for completing all tests runs for a given pollutant. Moreover, the rule relies on the non-enforceable maximum capacities included in operating permits for the purpose of establishing worst case emissions.

The National Emission Standards for Hazardous Air Pollutants, 40 CFR Part 63, and the New Source Performance Standards, 40 CFR Part 60, require that tests be based on representative performance of the affected facility. The Maximum Achievable Control Technology Program further defined “representative performance” as “normal operating conditions.” Thus, the proposed rules differ from existing federal requirements which apply to numerous emission units governed by 326 IAC 3-6. The proposed rule at 326 IAC 3-6-3(c) acknowledges that other applicable requirements regarding stack testing exist, but fails to bridge the gap between the proposed rules and the differing federal standards because it requires compliance with the federal standards and the proposed rule “as appropriate.”

IDEM is accepting comments on the proposed changes to the stack testing requirements as well as other amendments to the Compliance Monitoring Rules through June 11, 2010. The Air Pollution Control Board is expected to conduct a preliminary adoption hearing sometime after September of this year.

A copy of the proposed rule can be accessed at:, and a copy of the extension of the comment period is available at:


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