3M owns and operates two calciners at its Cottage Grove, MN, facility. Both calciners are subject to the Standards of Performance for Calciners and Dryers in Mineral Industries. 3M uses a wet scrubbing system to control nitrogen oxide and particulate matter emissions from the calciners. 3M violated the requirements to measure and record continuously the pressure loss of the gas stream through the scrubber and the scrubbing liquid flow rate to the scrubber and to determine and record once each day an arithmetic average over a 24-hour period of both the change in pressure of the gas stream across the scrubber and the flowrate of the scrubbing liquid. Pursuant to the Consent Agreement and Final Order, 3M will pay a $30,000 civil penalty. In December 2007, 3M requested that it monitor the nozzle pressure of its Venturi scrubber instead of the pressure loss of the gas stream through the Venturi scrubber. In February 2008, EPA approved the request.