Final rule · 2026-11432

Air Plan Approval; Minnesota; Revision to Taconite Federal Implementation Plan

The U.S. Environmental Protection Agency (EPA) is revising the Original 2013 Federal Implementation Plan (FIP) by finalizing nitrogen oxide (NO<INF>X</INF>) emission limits for the indurating furnace at United States Steel's (U.S. Steel) Keetac taconite facility (Keetac) in Keewatin, Minnesota to satisfy the requirement for best available retrofit technology (BART) at taconite facilities. The EPA is finalizing the following NO<INF>X</INF> BART emission limits for the Keetac Grate Kiln indurating furnace, with compliance to be determined on a rolling 720-hour average: 3.4 pounds (lbs) of NO<INF>X</INF> per million British Thermal Unit (MMBtu) when firing exclusively natural gas, which will become enforceable beginning three years after promulgation of a final rule; and 2.0 lbs NO<INF>X</INF>/MMBtu when firing any fuel or combination of fuels other than exclusively natural gas, which will become enforceable five years after promulgation of a final rule, unless before that date the EPA promulgates a modified limit. The final rule allows Keetac, within a period of 52 months from the effective date of the final rule, the option to seek a potential adjustment of the cofiring emission limit, not to exceed 2.5 lbs NO<INF>X</INF>/MMBtu as a 720-hour rolling average, based on collection of continuous emission monitoring system (CEMS) data after installation of the NO<INF>X</INF> reduction technology.