The St. Mary's Cement facility in Dixon, Illinois operates four cement kilns: Kilns 1 though 3 are pre-heater kilns and Kiln 4 is called a long-dry kiln. The Consent Decree (CD) addresses Prevention of Significant Deterioration (PSD) nitrogen oxide (NOx) violations related to the facility's use of petroleum coke as a fuel. The CD requires the installation of Selective Non-Catalytic Reduction (SNCR) control technologies to reduce 4,600,000 pounds of NOx emissions, which will cost a total of $1,900,000, at the facility. The facility will have the option of permanently shutting down Kiln 4, or replacing the unit with a new kiln which uses SNCR that reduces NOx emissions to a lower rate. The CD also requires that each kiln operates with a NOx continuous emission monitor, which continuously measures NOx emissions from each stack.