Document mpbKzOOMm98q897gR3YYz516Z

TALEN ENERGY NortiNestern EFI('P)Y 5 March 28, 2025 A. The technology to implement the 2024 MATS Rule specifically for Colstrip is unavailable. Concerning technological availability, CAA Section 1 12(i)(4) states: 'The President may exempt any stationary source from compliance with any standard or limitation under this section for a period of not more than 2 years if the President determines that the technology to implement such standard is not available." 42 L.S.C. 7412(i)(4). The President should exempt Colstrip pursuant to CAA Section 112(i)(4) because Colstrip does not have a practically available technology to implement the 2024 MATS Rule. 1. Application of baghouses to Colstrip is technologically unproven and untested given Colstrip's existing pollution control technology. It is true that baghouses, for new power plants, are widely available because the control technology is installed after the combustion device (the boiler). But in the case of Colstrip, the ba2house must be installed after the already-existing wet venturi scrubbers, which the plant currently uses to control fl'M emissions and sulfur dioxide (SO,). To utilize only a baghouse would require a complete redesign of the facility and likely a new stack, which would be cost prohibitive. The wet venturi scrubbers already capture 99.6% of the fPM, but to capture the remaining 0.2% as required by the 2024 MATS Rule, the baghouses would be needed as an addition to the backend of the wet venturi scrubbers, which would be a unique and unproven combination. While this arrangement may be theoretically possible, it is challenging and untested in practice. The combination of wet venturi scrubbers followed by baghouses increases the risk that the condensed water droplets (from the scrubbers) would meet the fly ash emitted by the plant, creating particles similar to concrete on the filter bags, thereby crippling the baghousc. Effectively, the combination increases the likelihood that the entire facility gets clogged with concrete particles. Additionally, once the bags arc plugged, they must be replaced, and a significant number of plugged bags could result in emission exceedances, the plant being derated, or the plant being forced offlinc. Ialcn Montana is unaware of such control technologies ever being applied together in this arrangement at any other facility in the entire United States. As such, there is no proof that such technology is available to capture the small, remaining amount of particulate that exists following the installed wet venturi scrubbers. And because of the short compliance deadline, Colstrip would be required to construct, test, and implement this unprecedented combination on the fly, potentially spending at least 5500 million only to have the revamped control system fail. As a result, the technology to comply with the Rule is technologically unavailable. Sierra Club FOIA 2025-EPA-04883 ED_018388_00000306-00005 SC_EVERSPLIT0006089