Section 420.31 - Specialized definitions(a) For ironmaking blast furnaces, the term product means the amount of molten iron produced.(b) The term molten iron means iron produced in a blast furnace as measured at the blast furnace, and may include relatively minor amounts of blast furnace slag that may be skimmed from the molten iron at the steelmaking shop or other location remote from the blast furnace.(c) The term iron blast furnace means all blast furnaces except ferromanganese blast furnaces.(d) The term existing indirect dischargers means only those two iron blast furnace operations with discharges to publicly owned treatment works prior to May 27, 1982. 67 FR 64266 , Oct. 17, 2002