While it has yet to appear in the Federal Register, EPA has released the final Combustion Turbine MACT Rule, Subpart YYYY of Part 63, which is designed to limit the emissions of hazardous air pollutant (HAPs) emissions from plant sites that are categorized as major sources. The final rule is much improved over the proposal. The highly problematic requirement to measure CO reductions across oxidation catalysts has been removed. EPA has rejected the proposed use of CARB Method 430, EPA Method 320, and EPA SW 846 Method 0011, relying only on EPA FTIR Method 323. The formaldehyde standard has been raised from 43 to 91 ppb at 15% O2, to be demonstrated by an annual test at full load.
While much better than the proposed rule, the rule is still a prime example of unsupported rulemaking. While some additional data were added, the final limit is still based on scant, poor quality data. There is so little data that EPA apparently felt compelled to keep CARB Method 430 even though it has rejected the method. (EPA found that the CARB 430 data only had a correlation of 0.56 with the FTIR data and applied a bias adjustment factor of 1.7 to the CARB data included in the analysis!) So much of the data "analyzed" were also little more than noise, below or near the true detection limit of the method. How can a meaningful limit be based on such questionable data? At least the new limit is much closer to range that can actually be reasonably measured and, fortunately, only new combustion turbines at major sources will be affected. Of course the most troubling aspect of the rule is that EPA failed to address the question of risk, whether the negligible HAPs from turbines actually pose a significant health problem, particularly at major sources. (Some data have shown higher concentrations in the ambient air than in the stack.)
Once published in the Federal Register, immediate compliance will be required for new or reconstructed combustion turbines located at major sources, although 180 days will given for the compliance demonstration. A copy of the final rule is available at our FTP Library.
RMB Consulting &