Document NG02NyNBpEOEov3e50LXbx4Dg

Unit 1 (257 MWg) commenced commercial operation in 1970, and Unit 2 (477 MWg) commenced operation in 1977. Both units employ Babcock and Wilcox cyclone boilers, and both boilers fire North Dakota lignite supplied from BNI Coal, Ltd's Center Mine, located in close proximity to the Young Station. Each unit is equipped with Advanced Separated Over Fire Air (ASOFA) and Selective Non-Catalytic Reduction (SNCR) for NOx control. Each unit is equipped with Wet Flue Gas Desulfurization (WFGD) for SO2 control. Each unit employs an Electrostatic Precipitator (ESP) for particulate control. Each unit employs halide injection and activated carbon injection for the control of mercury. Currently, Minnkota uses the same mercury control strategies for both Units and has maintained compliance with the standards. Although Minnkota uses the same control devices for the Units, operation and emissions output differs based on a number of factors. The Units vary in capacity and control device design. Unit 2 has a different ductwork configuration between the air heater and the electrostatic precipitator than Unit 1. Unit 1 has shorter ductwork. Length of ducting effects the amount of residence time for the flue gas to be exposed to powdered activated carbon (PAC), a longer duct provides more time for oxidized mercury to be adsorbed by the PAC, resulting in greater ability to limit mercury emissions. C. MATS RTR and Presidential Exemption Section 112(i)(4) 1. Clean Air Act 112(d)(6) and revised MATS RTR EPA promulgated MATS under Clean Air Act (CAA) Section 112 which regulates hazardous air pollutant (HAP) emissions. Congress defines EPA's scope of review for the RTR under the CAA in Sections 112(d)(6)and 112(f)(2). CAA Section 112(d)(6) defines the technology review for air toxics standards such as MATS as follows: The Administrator shall review, and revise as necessary (taking into account developments in practices, processes, and control technologies), emission standards promulgated under this section no less often than every 8 years.2 CAA Section 112 does not require EPA to recalculate the maximum achievable control technology (MACT) floor from the original standard.' The statutory language, "review, and revise as necessary" does not impose that type of analysis.4 Rather, the review process is more limited and defined by statute as the one-time residual risk review and the octennial technology review. In addition, costs are implied as a component of the RTR analysis.' In addition, Section 112(f)(2) states, in part, "if standards promulgated pursuant to subsection (d) and applicable to a category or subcategory of sources emitting a pollutant (or pollutants) classified as a known, probable or possible human carcinogen do not reduce lifetime excess cancer risks to the individual most 2 42 U.S.C. 7412(d)(d). NRDC v. EPA, 529 F.3d 1077, 1083 (D.C. 2008) (NRDC). 4 Id. 5 Association of Battery Recyclers Inc. v. EPA, 716 F.3d 667, 673 (D.C. Cir. 2013). An Equal Opportunity and Affirmative Action Fropinyer. Sierra Club FOIA 2025-EPA-04883 ED_018388_00000327-00004 SC_EVERSPLIT0006313