Draft February 5 , 2009 Ref: PF/NPDES/PER The blast furnace recy cle sy stem consists of two thickeners (i.e., one for each furnace), a cooling tower and a pump house for recirculating treated process water for reuse at the blast f urnaces. Periodic b lowdown from or lake water make

- up to this sy stem occur s throughout the day

in order to maintain a hy draulic balance within the recycle sy stem. The blowdown is discharged to the plant ’s dirty industrial wastewater (DIW) sewer sy stem for further treatment at the Secondary Wastewater Treatment Plant (SWTP) prior to discharge to surface waters of the State. In the event the recycle s ys tem experiences elevated concentrations of cy anide, a stead y - state blowdown can be directed to an alkaline c hlorination s ys tem to destroy the cy anide before discharge to the SWTP. The sinter plant has its own dedicated treatment plant that receives all of the gas cleaning blowdown from the sinter plant and minor quantities of filtrate from the mechanical dewate ring of BOF sludge. Excess moisture is added to this sy stem by virtue of the process and is blown down to the Reclamation Services Building (RSB) for treatment. After pH adjustment (we try to maintain a pH of about 9.3) and the addition of flocculation/co agulation poly mers, the wastewaters are directed to the final thickener for preliminary

clarification. The effluent of the final thickener discharges to the Dirty Industrial Wastewater ( DI W ) sewer s ys tem for further treatment at the SWTP.

The basic ox y gen furnace recy cle sy stem consists of two thickeners that treat the gas cleaning process waters prior to recy cling back to the gas cleaning s ys tem or blowdown to the DIW sewer s ys tem for further treatment at the SWTP. The continuous casters (2) are equip ped with scale pits for the removal of suspended solids and oil. The hot forming mills (two plate mills and the hot strip mill) are also equipped with scale pits and oil skimming equipment. The facilities recy cle a portion of the scale pit effluent water f or use in the production process and the balance is discharged to the DIW sewer s ys tem for further treatment at the SWTP. Wastewaters generated from the hot dip (galvanizing) coating line are filtered prior to discharge to the DIW in order to remove parti culate zinc. Waste pickling acids are either used on site to neutralize wastewaters, sold for off

- site recy cling or disposed of by deep well injection. Pickling rinsewaters and fume scrubber blowdowns are combined with pretreated wastewaters from the cold rolling operations and directed, via the DIW sewer sy stem, to the SWTP for final treatment. Contaminated groundwater from the ore dock area is recovered and used as a replacement for lake water in the gas cleaning s ys tems of either the Sinter Plant or the Blast Furnaces. As noted above, the blowdowns from these sy stems receive initial treatment at the generation site and secondary treatment at the SWTP. Most of the facility ’s wastewaters receive primary treatment at their source and final treatment at the SWTP. Final treatment includes pH adjustment, oil separation,flocculation/coagulation and clarification prior to discharge through several open channel

convey ances before reaching the East Branch of the L ittle Calumet River. Sludges generated b y the SWTP will be disposed on

- site in a permitted Ty pe 1 solid waste landfill (to be constructed) . An y leachate generated b y the landfill will also undergo preliminary treatment prior to discharge to the DI W and SWTP. The SWTP effluent is routed through two lago ons prior to discharge through internal Outfall 011 and final Outfall 001 into the East Branch of the Little Calumet River. The lagoons are equipped with aerators for temperature control. Lake Michigan water can also be added to the Outfall 011 discharge d uring warm weather months for additional temperature control.