Tilden Mining Company (Tilden) is a taconite iron ore mine and processing plant in Michigan that produces iron pellets for use in integrated steel mills. The company is operated by Cliffs Natural Resources. The facility's operations include mining, crushing, and pulverizing taconite ores to create a concentrate that is then dried, pelletized into balls, and sent into high-temperature indurating furnaces to harden before being transported to integrated steel mills. Tilden is subject to the National Emissions Standards for Hazardous Air Pollutants: Taconite and Iron Ore Processing, at 40 C.F.R. Part 63, Subpart RRRRR (Taconite MACT). The main pollutant of concern is particulate matter (PM). Tilden had several violations of its parametric monitoring limits (pressure drop and water flow rate) required to demonstrate compliance with the Taconite MACT limits. Additionally, Tilden exceeded opacity limits contained in the Michigan State Implementation Plan (SIP). The consent decree includes the following injunctive relief: (1) semi-annual reporting of all pressure drop and/or water flow rate deviations at of the Facility's wet scrubbers and corrective actions taken, and (2) performance of a review of Continuous Opacity Monitoring (COMs) data at the Facility's indurating furnace electrostatic precipitators (ESPs), for visible emissions above 20% opacity on a six-minute average, and a description of the corrective actions taken by the Facility to address the excess opacity. The consent