Gerdau owns and operates a steel mini-mill in St. Paul, Minnesota. The mill receives recycled automobile bodies, tin cans from refuse-derived fuel recycling operations, recycled white goods, and other grades of scrap steel. The automobile bodies, tin cans, and white goods are shredded in an auto shredder. A wet scrubber and cyclone control particulate matter (PM) and PM less than 10 microns (PM10) emissions from the auto shredder. Per the Minnesota SIP and the facility's Title V Permit, the facility is required to limit emissions from its auto shredder to less than 20 percent (%) opacity. Additionally, the Minnesota SIP and the facility's Title V Permit require the facility to maintain its auto shredder emission unit and associated controls in proper operating condition to ensure proper control of PM/PM10 emissions.
Specifically, Gerdau failed to:
(1) limit emissions from its auto shredding operations to less than 20% opacity on August 30, 2016, on September 1, 2016, and on November 4, 2016;
(2) maintain the auto shredding emission unit and associated controls in proper operating condition for several days in 2016 and 2017;
(3) operate the control equipment in such a manner as to achieve and maintain compliance with the PM10 emission limit at its auto shredding emission unit for several days in 2016 and 2017; and
(4) properly monitor and maintain operating records of the auto shredding emission unit and associated controls for several days during the period fro