Document 6O8LMj5EjZZQRpj2kXnzyB41

Hon. Lee M. Zeldin March 31, 2025 Page 9 from the source category based on a development in the industry." 88 Fed. Reg. at 30,926. EPA disclosed no development in the industry in the proposed rule and pointed to no error in the use of PM as a surrogate for acid gases, but nonetheless proceeded to propose abandoning its use of PM as a surrogate with a cryptic reference to EPA's "understanding of the chemistry of these compounds." 88 Fed. Reg. at 30,927. U. S. Steel and other commenters raised numerous concerns, including the lack of any explanation why EPA was abandoning its long-held conclusion that PM was an appropriate surrogate and why, even if acid gases were to be independently monitored, EPA believed scrubber water pH was an appropriate parameter for doing so. Yet in the Taconite RTR Rulc EPA inexplicably contravenes its prior determination for the use of PM as a surrogate while continuing to conceal, to the extent it exists, any data or rationale EPA has for rejecting the surrogate relationship EPA has relied upon for nearly two decades. Taconite RTR Rule at 16,420. The Taconite RTR Rule, like the proposed rule, continues to rely on scrubber water pH as a parameter for wet scrubber performance, providing no citation to data or evidence to support this conclusion. C. S. Steel believes that the technology to use scrubber pH water as an operating parameter for measuring acid gas removal efficiency, particularly in a once thru scrubbers, is not based upon any sound data and therefore, the technology is not available. C. Technology to implement the new pi1 Monitoring Requirements at U. S. Steel's Minntac and Keetac facilities is unavailable; and even if it were available, it is not needed to demonstrate compliance with the hydrogen chloride and hydrogen fluoride limits is not available. (See amendments. to 40 (TR 63 Subpart RRRRR including but not limited to 40 CH? 63.9590(h)(5); 63.9622(g), (g)(1)-(2); 63.9623(c), (c)(1); 63.9623(f) 63.9631(f); 63.9632(b)-(e) as applied to pH monitoring; 63.9632(g); (g)(1)-(4); 63.9634(i); (i)(1)-(4); Subpart RRRRR Tables 1-4 as applied to pll monitoring related to hydrogen chloride and hydrogen fluoride.) There is no technology available in which the Taconite RTR Rule's requirements for pI I monitoring and maintaining pH at set points as a questionable means to demonstrate compliance with the new hydrogen chloride and hydrogen fluoride limits for potentially billions of gallons of water at Minntac's once-through wet scrubber systems at Minntac, nor is it available for implementation at Keetac. While taconite iron ore processing facilities, including U. S. Steel, control pH for sulfur dioxide purposes on certain scrubbers that recycle the scrubber water, EPA has not shown any nexus of pH of scrubber water as it is related to hydrogen chloride and hydrogen fluoride emissions. Furthermore, U. S. Steel has no data to correlate pII to hydrogen chloride and/or hydrogen fluoride emissions nor has EPA provided any. There is no indication that maintaining pH is needed to achieve the acid gas limits in the Taconite RTR Rulc and EPA has not provided any such credible justification. Furthermore, when collecting data from taconite iron ore processing facilities under its Information Collection Request authority under Section 114 of the Clean Air for the development of the Taconite RTR Rule, EPA did not request or collect any pH monitoring data. The new HAP limits were determined using data with the taconite iron ore processing facilities operating within the Sierra Club FOIA 2025-EPA-04883 ED_018388_00000151-00009 SC_EVERSPLIT0005889