The Environmental Protection Agency (EPA) has proposed to expand the applicability of the National Emission Standards for Hazardous Air Pollutants (NESHAP) for stationary combustion turbines. EPA originally established the combustion turbine (CT) NESHAP in 2004. On April 12, EPA officially proposed the long overdue residual risk and technology review (RTR), which is required within eight years of the final standards.

While, based on its RTR analysis, EPA proposes to leave the current CT standards in place, the proposal would expand the reach of those standards to two additional subcategories of units by lifting a stay that has been in effect since the standards were originally finalized. Lifting that 15-year-old stay would impact lean pre-mix and diffusion flame natural-gas-fired CTs. The proposal would also eliminate the startup, shutdown, and malfunction exemption for all units subject to the rule. Although all existing lean pre-mix and diffusion-flame gas-fired units would become subject to the NESHAP, only units constructed or reconstructed after January 14, 2003 must comply with substantive emission and operating limitations.

The stay stemmed from an effort to delist certain subcategories of CTs, including lean pre-mix and diffusion flame gas-fired CTs from the list of sources to be regulated under Section 112. In response to a petition filed by the Gas Turbine Association in 2002, in 2004 the EPA proposed to delist the specified CT subcategories under Section 112(c)(9) of the Act. Pending the outcome of its proposed delisting, EPA stayed the rule as applied to these two subcategories to avoid unnecessary compliance costs. However, in 2007, the D.C. Circuit held that delisting only applies to entire source categories, and EPA may not delist a subcategory of an otherwise regulated source category. NRDC v. EPA, 489 F.3d 1364 (D.C. Cir. 2007). EPA has proposed to find that it cannot delist all stationary combustion turbines based on the standards outlined in Section 112(c)(9); therefore, the subcategories must remain on the list as well, eliminating the basis for the 2004 stay.

The 2004 standards, which EPA proposes to leave in place, only establish emission standards for units that commenced construction or reconstruction after January 14, 2003. Those units must limit formaldehyde emissions to 91 ppb at 15% O₂ except during startup. While it removes the exemption for startup, shutdown and malfunctions, the proposal includes a work practice standard for startup that limits duration of unit startup to one hour for simple cycle CTs and three hours for combined cycle units.

If finalized as proposed, lean pre-mix natural gas-fired CTs and diffusion flame gas-fired CTs located at major sources of hazardous air pollutants would become subject to the NESHAP requirements published at 40 CFR part 63, subpart YYYY, including the initial performance test requirements. Affected sources would have 180 days from the effective date of the final rule to complete their initial performance tests. EPA has provided 45 days for public review, and comments on the proposal are due by May 28, 2019. A copy of the proposal can be found here and background on the CT NESHAP is available here.