Upcoming Changes to the Turbine MACT With a Short Timeline to Comply

On Friday, April 12, 2019, U.S. EPA proposed changes to the National Emission Standards for Hazardous Air Pollutants for Stationary Combustion Turbines [40 CFR 63, Subpart YYYY (Turbine MACT)] as a result of its risk and technology review (RTR).  This latest RTR proposal is one in a long list of RTR rules with court-ordered deadlines, so the comment period is only 45 days.  Although U.S. EPA is proposing that the health risk from the turbine source category is acceptable and there have been no new technology developments, there are significant changes to the rule being proposed.  As a reminder, this rule applies to major sources of hazardous air pollutants (HAP), not area sources.

The major change U.S. EPA proposes to make is the removal of the stay of the 91 parts per billion by volume (ppbv) @ 15% oxygen (O₂) formaldehyde limit for new and reconstructed lean premix and diffusion flame gas-fired turbines (those constructed or reconstructed after January 14, 2003).  The 91 ppbv new source standard was originally promulgated in 2004 but U.S. EPA later stayed the effectiveness of the emissions standard for lean premix and diffusion flame gas-fired turbines after a subsequent proposal to delist these subcategories from regulation under 40 CFR Part 63.  However, a 2007 D.C. Circuit Court decision determined that it is not legal for U.S. EPA to delist a subcategory; U.S. EPA may only delist an entire source category.  The current proposal indicates that U.S. EPA does not currently have sufficient information to delist the entire source category. Therefore, U.S. EPA is proposing to remove the stay of the standards, which will reinstate the requirement to implement the 91 ppbv emissions standard.  The proposal only provides 180 days from the date of the final published rule for facilities to demonstrate compliance via stack testing.  The timeline is problematic for some facilities that installed new gas turbines since 2003 without an oxidation catalyst because it is likely that an oxidation catalyst will be necessary to meet the 91 ppbv limit.  U.S. EPA estimates that 182 new lean premix and diffusion flame gas-fired turbines were constructed or reconstructed between 2003 and 2017.  180 days is insufficient time to perform the necessary engineering work and complete a shutdown to install and test a catalyst.  Even scheduling, conducting, and verifying results of a performance test in 180 days may be challenging.  Facilities that will be affected by the 91 ppbv formaldehyde limit should consider testing now to determine whether any changes are necessary to achieve compliance.  The timing required to demonstrate compliance with the new formaldehyde limit will be a focus of industry comments on the rule.  Note also that U.S. EPA is only required to finalize the RTR by March 13, 2020; it could defer the lift of the stay until a subsequent regulatory action.

U.S. EPA is also proposing to remove the startup, shutdown, malfunction (SSM) exemption and eliminate the requirement to develop, implement, and follow an SSM plan for all operators of turbines subject to the rule.  Language reflecting the general duty to minimize emissions is proposed for addition to the rule.  For lean premix and diffusion flame turbines subject to a numerical standard, a work practice requirement is proposed for startup, but there are no separate standards for malfunctions or shutdown periods.  U.S. EPA proposes that during startup, operators must minimize the turbine’s time spent at idle or low load levels and minimize the turbine’s startup time to a period needed for appropriate and safe loading of the turbine, not to exceed 1 hour for simple cycle turbines and 3 hours for combined cycle turbines.  While it is a good approach to implement a work practice for startup periods to allow a certain amount of time for the oxidation catalyst to reach a temperature at which organic HAP emissions will be controlled, the work practice should not be so inflexible as to prohibit operation at low loads if the numeric standard can be met while operating in a turndown type situation (e.g., a site may wish to reduce turbine load during the day to accommodate an influx of solar-generated energy). Collecting formaldehyde emissions data at low loads is warranted for facilities that want this flexibility.  U.S. EPA does not have information to indicate that organic HAP emissions are higher during shutdown than during normal operation and is not proposing a different standard during shutdown.

Proposed changes to recordkeeping and reporting requirements include documenting startup conditions and excess emissions events. Operators will be required to record the date, time, and duration of startup periods.  For excess emissions events, operators will be required to record actions taken to minimize excess emissions, an estimate of the amount of emissions over the standard, and a description of the method used to estimate the excess emissions. Electronic reporting via the Compliance and Emissions Data Reporting Interface (CEDRI) is proposed for routine compliance reports and for annual emissions test reports.  A draft report template is included in the rulemaking docket for comment.

Comments are due by May 28, 2019; contact Amy Marshall at amarshall@all4inc.com or (984) 777-3073 for more information.