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Air Toxics Update: Combustion Turbines and Engine Test Cells

  • 6/30/2020 2:58:00 PM
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EPA recently updated several federal regulations for hazardous air pollutants (also known as HAP or air toxics). EPA’s actions address the Risk and Technology Review (RTR) required under the U.S. Clean Air Act.

This is the fourth in a series of articles covering EPA’s updates to air toxics regulations (also known as National Emission Standards for Hazardous Air Pollutants or NESHAP). Find background on the NESHAP RTR requirements and a general overview of the recent changes in the Air Toxics Update. In the following weeks, Iowa DNR will address changes to specific regulations affecting Iowa businesses.

Updates to the Standards for Combustion Turbines and Engine Test Cells

On March 9, 2020, EPA published final NESHAP RTR amendments for Combustion Turbines. This source category includes turbines used at facilities such as power plants, chemical and manufacturing plants, and pipeline compressor stations. The primary air toxics present are formaldehyde, toluene, acetaldehyde, and benzene. DNR estimates that two Iowa facilities are currently subject to this NESHAP.

On June 3, 2020, EPA published final NESHAP RTR amendments for Engine Test Cells/Stands. This source category includes engine test cells/stands that are used in applications to develop, characterize and test engines. Engine test cell/stands emit air toxics in the exhaust gases from combustion of gaseous and liquid fuels as engines are tested. Primary air toxics emitted include toluene, benzene, mixed xylenes, and 1,3- butadiene. DNR estimates that one Iowa facility is currently subject to this NESHAP.

The updated standards for these source categories (Combustion Turbines: published in 40 Code of Federal Regulations (CFR) Part 63 Subpart YYYY and Engine Test Cells: published in 40 CFR Part 63 Subpart PPPPP) include, but are not limited to, the following changes:

  • Startup, Shutdown, and Malfunction (SSM): For both source categories, EPA clarified that the emission standards apply at all times, including during periods of startup, shutdown and malfunction.
  • Electronic Reporting: For both source categories, owners and operators are required to submit electronic copies of performance test reports and performance evaluation reports and semiannual reports through the EPA’s Central Data Exchange, using the Compliance and Emissions Data Reporting Interface. Note: Affected facilities must also comply with Iowa requirements for submitting reports, as specified in Iowa administrative rules or in air permits.

For more information:

Compliance Deadlines

  • Combustion Turbines: Affected sources must comply with the new requirements by Sept. 8, 2020.
  • Engine Test Cells/Stands: Affected sources that commenced construction before May 27, 2003, have until Dec. 1, 2020, to comply with the new amendments. Affected sources that started up on or after May 27, 2003, but on or before May 8, 2019, must comply with all requirements upon startup, except that the compliance date for the new SSM and Electronic Reporting is Dec. 1, 2020. Affected sources that commence construction or reconstruction after May 8, 2019, must comply with all requirements upon start up.

Implementation in Iowa

DNR plans to begin rulemaking to incorporate the updated standards—which will give DNR authority to administer the rules. In the interim, EPA will implement the NESHAP RTR changes. DNR is available to answer questions about the new amendments and will work with EPA Region 7 to assist facilities.

DNR staff will review the changes and contact facilities that we know are impacted and have substantively different requirements in their permits from the updated NESHAP. However, an affected facility should carefully review the updated federal standards to be aware of any new requirements and compliance dates. An affected facility must still comply with the NESHAP requirements even if the requirements are not included in an Iowa air permit.

In the upcoming weeks, please keep an eye on your inbox for Air Toxics updates on other individual source categories.

If you have technical questions about the NESHAP changes, please contact Michael Hermsen (email:; phone: 515-725-9577). For general questions, please contact Christine Paulson (email:; phone: 515-725-9510).